Analysis of the plate production of offset printing. Quality criteria
Ministry of Education Russian Federation
Faculty: Printing engineering and technology
Form of study: part-time
Course project
Discipline: Technology of Form Processes
Topic: Development of technology for the production of printed forms of flat offset printing according to the scheme "computer - printed form»
Student: Chernysheva E.A.
Group VTpp-4-1
Spruce supervisor: Nadirova E.B.
Moscow
2011
Fyodorov MOSCOW STATE UNIVERSITY OF PRINT
Faculty of Printing Engineering and Technology
Specialty: Technology of printing production
Form of study: part-time
Department: Technology of prepress processes
EXERCISE
for the implementation of the course project
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4. Initial data for the project ___________________ ______________________________
5. Content of the project ______________________ ______________________________ _____
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6. Literature and other documents recommended for the student to study: ____________
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6.1. Source numbers according to methodological guidelines ____ ___________________________
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7. Date of issue of the task
"___" __________ 2011
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Content
Abstract 4
Introduction 5
1. Technical characteristics and design indicators of the edition 6
2. General technological scheme of product manufacturing 7
3. Technology of the form process, general scheme 9
4. Equipment, materials, software 12
5. Quality control of finished products 13
6. Process map 16
7. Imposition 17
8. Profitability, scope of work and labor intensity 18
Conclusion 19
List of used literature 21
abstract
Objective: Development of technology for the production of printing plates for flat offset printing according to the "computer - printing plate" scheme.
Legend:
TOII is a technology for processing graphic information.
LTTE is a technology for processing textual information.
LEU - laser exposure device.
The content of the work: 19 pages, 2 diagrams, 2 figures.
Introduction
Form processes are a complex of technological operations based on the use of analog and digital technologies for the production of printing plates, which are material carriers of graphic information intended for printing.
When developing this course project, the following goals were pursued: consolidating and expanding knowledge within the discipline, acquiring skills in the process of working with scientific and technical literature and electronic sources of information, developing skills in using reference and regulatory and technical documentation on printing technique and technology, as well as publishing processes, obtaining initial skills in the design and calculation of the form process.
Despite the variety of methods for obtaining printed products, the method of flat offset printing occupies a leading position. This is due to the ability to reproduce one- and multi-color images of any complexity with high graphic, gradation and color accuracy using raster structures with a lineature of up to 120 lines / cm. This method allows you to print publications on papers of different weights using a wide variety of methods for making printing plates. The method is also characterized by a high degree of automation of the form and printing processes, good economic performance, high-performance printing equipment.
1. Technical characteristics and design indicators of the publication
| Indicator name and characteristics | Indicator value | |
| in the edition taken as a sample | in the edition accepted for development | |
| 1 | 2 | 3 |
| Publication type: - for the intended purpose - by the symbolic nature of information - by frequency |
tutorial text-figurative non-periodic |
tutorial text-figurative non-periodic |
| Publication format: - declared format - product of width by height - the proportion of the paper sheet |
80x98 195x255 16 |
80x98 195x255 16 |
| Volume of the edition: - in physical printed sheets - in paper sheets - in pages |
19 9,5 304 |
19 9,5 304 |
| Edition circulation (thousand copies) | 2500 | 2500 |
| Printing design - the colorfulness of the publication and its constituent elements - the nature of the inline images, the rasterization lineature - area of illustrations in stripes and as a percentage of the total volume - the total amount of text in strips - printing method - type of used printing and type of printing inks |
raster 60 lines / cm 60% 183 121 offset book block: offset cover: coated |
4 + 4 (book block) 4 + 0 (cover) raster 60 lines / cm 60% 183 121 offset book block: offset cover: coated ink: for offset sheet printing |
| Edition design - number of notebooks - the number of pages in one notebook - the number and nature of additional elements - method of folding notebooks - method of assembling blocks - type and design of the cover, design |
19 16 cover 3-fold compilation |
19 16 cover 3-fold compilation type 3, paper 175 g / m2 coated, 4 + 0, straight spine |
2. General technological scheme of product manufacturing
In the method of flat offset printing, printing plates are used, on which the printing and space elements are located practically in the same plane. They have selective properties of perception of oil-containing paint and a moisturizing solution - water or an aqueous solution of weak acids and alcohols. The printing elements of the form are hydrophobic, whitespace is hydrophilic.
Fig. 1. Form of flat offset printing: 1 - printing elements, 2 - blank elements
The main difference of this printing method from letterpress and gravure printing is the use of an intermediate surface (offset cylinder) when transferring ink from the printing plate to the printed material.
Forms of flat offset printing differ from forms of letterpress and gravure printing in two main features:
- the absence of a significant geometric difference in height between the printing and space elements (CS thickness: 2–4 µm);
- by the presence of a fundamental difference in the physical and chemical properties of the surface of printing and blank elements.
To obtain these forms, it is necessary to create stable hydrophobic printing and hydrophilic white space elements on the surface of the printing material.
Methods of obtaining printable forms are formatted and item-by-item notation.
Format notation- This is the recording of an image over the entire area at the same time (photographing, copying). Item-by-item notation- the image area is divided into some discrete elements, which are recorded gradually element by element (recording using laser radiation).
Original - a text or graphic work that has undergone editorial and publishing processing and prepared for the manufacture of a printed form. Originals are classified into the following types.
Analog original- the original on a physical medium, which requires translation into a digital file for its subsequent processing and reproduction.
Digital original- the original, the informative part of which is contained in coded form.
Image scanning, computer processing and screen proofing are discussed in detail in the discipline of TOI.
Receiving a text file, proofreading and computer layout of the pages are studied in the LTTE discipline.
Electronic imposition editing- placement of pages in the format of a sealed sheet of the publication in an electronic way, using the computer of the publishing system. Installation is controlled visually on the system monitor screen or on a hard copy received on a printer.
Electronic version of the printed form- an electronic file containing all the elements that will be located on the printed form, in a coded form. From this file, information will be recorded directly on the form.
Flatbed offset printing plate output- production of a printing plate for flat offset printing, depending on its characteristics. The layout of the printed product in electronic form is displayed on the plate, skipping the stage of outputting color-separated transparencies.
Quality control of the finished printing plate- tracking the parameters of the printed form according to the requirements.
3. Technology of the form process, general scheme
In the manufacture of a printing plate for flat offset printing according to the "computer-printing plate" scheme, a kind of digital technology is used - the CTP technology. In turn, it can be divided into two directions, depending on the type of plates: light-sensitive and heat-sensitive. This technology uses lasers as a radiation source in both cases. Therefore, this technology is called laser. When using a photosensitive plate, the laser wavelength is 405-410 nm (violet).
The element-by-element recording of information on this technology is carried out in an autonomous exposing device. The CTP technology can be applied both in the OCU and in the OCU. This method of producing printing plates involves the use of laser exposure. Various properties of laser action are used:
- thermal effect - burning out or thermal decomposition of thin films on blank or printing elements of the future printing plate;
- photochemical effect on the photosensitive layer of the printing material;
- electrophotographic effect on the photosemiconductor layer.
Page PostScript files control an exposure device that shapes a shape in a similar way to a photosetter. However, in this case, the software also carries out the placement of pages on the form in accordance with the adopted imposition organization scheme.
In the modern printing industry, these technologies have not yet taken a leading place. Their introduction is hindered by expensive equipment and mold materials (imported).
3.1. The structure of the printing plate of flat offset printing for CTP technology
A - form plate; B - image recording; B - heating; G - removal of the protective layer; D - printed form after development; 1 - substrate; 2 - photopolymerizable layer; 3 - protective layer; 4 - laser; 5 - heater; 6 - printing element; 6- space element
The technological capabilities of modern offset plates make it possible to produce printing plates on them that are suitable for printing almost all types of high-quality products (graphic, advertising, newspaper, magazine, book, etc.).
In printing plates with a photopolymerizable layer, as a result of the action of radiation, a spatial structure is formed. To enhance the effect of radiation, the exposed plate is subjected to heating, which strengthens the polymer structure. For some types of plate with FPS, an additional layer can be located on the surface of this layer to increase the efficiency of the primary action of laser radiation, in this case heating after exposure is not carried out. Further development is carried out, as a result of which unexposed areas of the layer are removed. After the image is recorded with a laser source, the exposed plate is usually subjected to the necessary processing in chemical solutions. The process of making printing plates can include such operations as gumming and technical proofreading, if they are provided by the technology. Form control is the final stage of the process.
Requirements for plate plates:
- roughness - the adhesion of the copy layer to the substrate and, accordingly, its resistance to mechanical stress depends on it;
- circulation life - 100-400 thousand prints;
- the color contrast after processing the copy allows you to visually assess the quality of the resulting shape;
- light sensitivity (S) determines the exposure time of the plate. The higher the photosensitivity, the less time you need to spend on exposure;
- the resolution determines the percentage of the reproduced raster point and the minimum possible line width;
- energy sensitivity - the amount of energy per unit surface required for the processes in the receiving layers of the plate;
- spectral sensitivity - the sensitivity of the receiving layers to UV in the visible wavelength range.
4. Equipment, materials, software
To process the text and graphic parts of the future edition, you will need such technical means as: a computer, an LCD monitor, a mouse, a keyboard, an inkjet printer, a CTP device, a device for color proofing, and a LEU.
Software: Windows Vista Home Premium (operating system), working formats (PS, PDF, EPS, TIFF, JPEG), applications (Microsoft, Adobe, QuarkXpress, CorelDrow, Preps)
The preparation of the originals consists in checking them for the presence of all the necessary elements, converting them into a single format.
Plate care products
CtP Deletion Pen - correction pencils for thermal plates for CtP manufactured by AGFA, Kodak, Lastra and some others. Their purpose is to correct forms, remove unnecessary printed elements identified at the stage operational control... Pencils have a convenient plastic body, they are available in two standard sizes - for coarse and fine correction, differ in the diameter of the rod.
Positive Deletion Pen are correction pencils designed to remove printed elements from traditional positive offset plates, where the copy layer is diazo compounds. Pencils are produced in 4 standard sizes with different rod diameters.
Adding Pen - pencils for adding printing elements to offset plates. They have an aluminum body, two standard sizes in thickness. Adding printing elements is possible on any type of plate - positive, negative, for exposure in CtP or copy frame.
Laser exposure device
LEU for recording information on offset printing plates are designed to expose the radiation of the receiving layer of the printing plate.
LEU classification:
1. Type of plates - for recording on photosensitive plates.
2. Type of laser source - solid-state laser.
3. The structure of the device is an inner drum. The molding material is located on the inner surface of a stationary drum in the form of an unfinished cylinder. The scanning of the image in such a device is carried out vertically due to the continuous rotation of the deflectors with one reflective edge and horizontally due to the movement of the deflector and the optical system along the axis of the drum.
4. Purpose - universal.
5. The degree of automation is automated.
6. The format is large.
5. Quality control of finished products
The produced printing plate must have the following characteristics:
- coating with a protective colloid;
- lack of surface damage;
- the presence of control marks for alignment;
- the presence of marks for cutting and folding;
- on the edges of the form, there should be scales that allow you to quickly control the printing process;
- the size of the image must be equal to the specified size of the reproduction. Permissible deviations: for image sizes up to 40x50 cm - 1 mm;
- the image on the form must be located in strict accordance with the layout. Image size must match the size of the transparencies.
- forms of one set for printing multicolor products must be of the same thickness. Permissible deviations for plates with a thickness of 0.35–0.5 mm are not more than ± 0.06 mm; with a thickness of 0.6–0.8 mm, no more than ± 0.1 mm.
- all printing elements must be reproduced on the form.
- the image on the form should be located strictly in the center, taking into account the fixing of the form in the printing machine.
- on the form there should be marks-crosses for alignment, necessary to control the printing process, and marks for folding, cutting and cutting (depending on the type of product).
Digital technologies for recording information on plate plates require quality control:
- testing and calibration of recording devices;
- control of the recording process itself;
- evaluation of the performance of the printed form.
Each stage of control is important, and the first two stages are considered fundamental, since the adjustment of the EI and the installation of the required powers of the laser source inevitably affects the entire subsequent technological process, and ultimately not the quality of the molds. Control test objects are used to control the quality of forms. They are presented in digital form and contain a number of fragments for various purposes for visual and instrumental control:
- information fragment with constant information about the test object itself and variable information with current data on specific recording modes;
- fragments containing objects of pixel graphics for visual control of the reproduction of image elements;
- fragments allowing to evaluate the technological capabilities of the recorder and the raster processor, as well as the reproduction and graphic indicators of printed forms.
UGRA / FOGRA DIGITAL PLATE CONTROL
Functional groups:
1. Informational part. Contains constant (username) and variable information. The angle of rotation of the raster structure is specified here, etc.
2. Evaluation of the resolution. Consists of dashed elements diverging from the center at different angles.
3. Diagnostics of geometry. For evaluating the reproduction of line elements of various sizes.
4. "Chess" zone. Control of reproduction of picture elements.
5. Area of visual assessment. Visual control of exposure.
6. Halftone wedge. Raster scale to control the reproduction of the gradation of tones.
DIGI CONTROL WEDGE
Functional groups:
1. Focusing. For visual control of the focusing of the laser beam. Consists of 180 radial lines 1 pixel wide.
2. Exposition. Visual control of exposure. Contains 6 fields in the form of circles with checkerboard filling.
3. Reproduction of line elements. Visual control.
4. Gradation interval.
5. Rastering. Rasterization information.
6. Information fragment. Contains information of permanent content.
A printing plate is considered suitable if all functional groups provide a satisfactory result.
6. Technological map of the process
| № | the name of the operation | The purpose of the operation and its essence | Applied equipment | Applicable materials |
| 1 | Image recording | Formation of a spatial structure in the photosensitive layer | Laser source, EPOD | Form plate with FPS, digital data |
| 2 | The heating | Strengthening the structuring effect | IR drying | Form plate with a recorded image |
| 3 | Removing the protective layer | Releasing printed elements | Rinsing bath | Form plate |
| 4 | Manifestation | Washing out the whitespace | CPU | FP, fixer, developer |
| 5 | Additional chemical treatment |
7. Imposition of the bands
8. Profitability, scope of work and labor intensity
CTP technology enables the transition to a complete digital process. This means that all stages of production can be controlled and automated: from image acquisition from digital media to finished printing plates. When using this technology, the production process is reduced by several stages. Two developing processes become unnecessary, measuring equipment for film control, copying equipment, perforation and mold registration systems, and assembly equipment. Considerably smaller equipment room is required. Productivity is increased by 70%. The makeready period for machines is noticeably reduced.
Exposure or recording time is the main factor affecting performance.
Conclusion
In the course of writing the term paper, knowledge was gained about CTP technology, photosensitive and heat-sensitive plates. And also the characteristics of this process are analyzed and a comparative analysis is carried out. Based on this, it can be concluded that the "computer-printing machine" system, both on the pre-press and during the preparation of the printing press, allows to achieve greater productivity with high cost savings. Fast plate making time, precise placement and automatic pre-adjustment of ink zones based on digital data is a huge advantage.
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abstract
Work 21 pages, 7 figures, 2 schemes, 2 tables, 5 sources.
FORM PLATE. OFFSET PRINT FORM. QUALITY OF PRINTED FORMS. TEST OBJECT.
Modern offset production is characterized by heavy use electronic equipment at all stages of preparing a publication for printing and conducting the printing process.
Looking at the popularity of offset today, the question arises of the need to control the quality of the forms and methods of its implementation, which is the subject of this project.
Introduction
1. Basic information about forms of offset printing
2. Reproduction and graphic indicators of offset printing forms
2.1 Resolution
2.2 Method for determining the modulation transfer function
2.3 Gradation characteristic
3. Factors affecting reproductive and graphic indicators
4. Means of control of reproductive-graphic indicators
4.1 Control of printing plates of flat offset printing, made on photosensitive plates
4.2 Control of printing plates of flat offset printing, made on heat-sensitive plates
Conclusion
Bibliography
Introduction
Today offset printing is the most developed highly mechanized industrial branch. Modern technologies, a high degree of standardization and automation of the entire production process, as well as reliable, fast and relatively inexpensive production of printing plates by conventional and digital methods, explain the high demand for this printing method.
The following reasons contributed to the high rate of development of the offset printing method:
1. Availability of high-performance, technologically flexible printing equipment;
2. Availability of manufacturing large-format products both on sheet and roll machines;
3. Possibility of two-sided printing of multicolor products in one run;
4. Improvement of quality and appearance of new technological materials.
1. Form basicsoffset printing
Printing plate - an image carrier, is a solid surface, flat or cylindrical, bearing printing (image) and space (other light) elements.
There is no officially approved classification for printing plates. Printed forms used for reproduction of text and pictorial information can be classified according to the following criteria:
Colorfulness of printed matter - forms for monochrome printing and forms (color-separated) for multicolor printing;
The symbolic nature of information is textual forms containing only textual information;
Pictorial forms containing pictorial information only;
Text-figurative forms containing text and figurative information;
Methods and types of printing - forms of letterpress (typographic and flexographic), flat offset (with moistening and without moistening blank elements), gravure printing and special printing methods;
The method of recording information on printing materials is made by format recording (information is transferred simultaneously to the entire surface area of the printing material - a plate or cylinder) and made by element-by-item recording (information is transferred sequentially to very small areas of the area).
In addition, depending on the purpose, printing forms are often subdivided into test forms, which serve to control color separation and other parameters, and production forms, used to print a certain number of copies of the same edition - circulation.
Offset printing is a printing technology that involves transferring ink from a printing plate to the printed material not directly, but through an intermediate offset cylinder. Accordingly, unlike other printing methods, the image on the printing plate is not mirror-image, but straight. Offset is mainly used in flatbed printing.
As forms for offset printing, very thin (less than 0.3 mm) metal plates are usually used. Such plates (either polymetallic or monometallic) stretch quite well on the plate cylinder. Printing plates for offset printing can also be paper-based or polymer-based. The most common material for metal printing plates is aluminum. The surface of the plate is granulated in different ways: using a sandblasting machine, using abrasive materials, etc. Currently, the process of graining the plate is carried out mainly electrochemically; at the final stage of the process, the plates are oxidized.
The process of making a printing plate for offset printing is as follows: a copy layer is applied to a metal base, on which an image bearing the ink is obtained. Typically, the oleophilic layer on the plate is copper. Currently, printing houses mainly use light-sensitive aluminum plate. After exposure and development of the plates, the image is formed. This is due to the fact that after processing, the surface of the plates acquires different properties. Under the influence of light and processing, printing plates form either ink-receiving or ink-repelling elements.
When processing a plate, two different photochemical reactions are usually distinguished:
1. Or the copy layer is cured with light, as a result of which it becomes insoluble for the developer. This is called negative copying.
2. Under the influence of light, the destruction of the copy layer can occur. Due to the destruction of the copy layer, those areas of the plate are cleaned on which there is no image. This processing is called positive copying.
Regardless of the form of copying, identical forms are obtained - the only difference is in the applied layers.
Sometimes, in order to increase the print life, after development, metal printing plates are subjected to additional heat treatment by firing.
3. To perform works of a small format that do not require High Quality printing, you can use forms on the basis of mylar.
In addition to the described printing plates used in traditional offset printing, thermosensitive plates have been created, the image on which is recorded by means of laser radiation.
2. Reproduction and graphic indicators of offset printing forms
Reproduction-graphic indicators characterize the quality of reproduction on printed forms of line and raster images. These include:
1. Resolution. Characterizes the reproduction of fine details of the image. It is estimated by the limiting number of lines per unit of length, separately reproduced on the printed form. To assess it, use special tests or control scales (worlds).
2. The releasing ability. It characterizes the ability to convey free-standing strokes, next to which there are no other small details. It is estimated by the width of the minimum reproducible stroke.
3. Gradation transmission of tone images. Specifies the quality of reproduction of tonal or bitmap images. Estimated by graphical dependencies.
2.1 Resolution highlightingability
Resolution R is the most important numerical indicator of the quality of graphic information reproduction. It characterizes the ability of the layer to reproduce separately the dashed elements of the image and is estimated by the number of lines (maximum created during the recording of the image) per unit length.
Unlike photographic copying processes, there is no approved standard for determining R copy layers and criteria for its assessment. In most cases in scientific research and industrial practice R is estimated by the frequency of the highest-frequency periodic grating consisting of groups of grooves of various sizes that are still resolved. The lattice is allowed if the strokes and the gaps between them are separated. Measured R in (or). For greater objectivity of the assessment, sometimes the value of the permissible relative distortions of strokes is also indicated.
Unlike R the highlighting ability characterizes the property of a layer to transmit free-standing dashed elements, next to which there are no other strokes or small details. The need to introduce such an indicator is associated with the peculiarities of the reproduction of a stand-alone stroke in comparison with reproduction in a group.
Resolution determination methods.
To determine the resolution, special test objects or control scales (targets) are used.
Such worlds (Fig. 2.) consist of groups of strokes of various sizes, and the strokes (at least three) in each separate group have the maximum optical density, and the gaps between the strokes are maximally transparent (therefore they are called worlds of absolute contrast). In most cases, the dimensions of the stroke and the gap (the gap between the strokes) in each group are equal to each other.
When evaluating the resolution of the copy layers, the world is copied onto a plate, and after developing on the image, the worlds are determined by the size of the minimum reproducible stroke, transmitted separately. Evaluated R the maximum number of strokes per 1 mm (or cm).
The highlighting power is estimated by the size of the minimum reproduced stroke and is measured in mm (or microns).
Rice. 2. Worlds for determining the resolution of the copy layers and their structure: 1 - circular; 2 - fan-shaped; 3 - rectangular, oriented in different directions; 4.5 - rectangular
The ability of copy layers to reproduce fine details of an image is conventionally evaluated in terms of resolution and highlighting capabilities. In essence, they only allow one to determine the size of the minimum stroke element of a particular test object, but at the same time they do not give an idea of how the strokes of other sizes are reproduced. Their reproduction can be assessed using the modulation transfer function, which contains information about the amount of blurring of line details of an image of various sizes.
2. 2 Method for determining the modulation transfer function
The method for determining the modulation transfer function of the copy layers is based on the construction of the edge function with its subsequent recalculation into the modulation transfer function. In turn, the boundary function is determined, for example, by changing the dimensions of dashed elements. For this purpose, they are repeatedly copied onto a layer at different exposures and the reproduction of these strokes on the developed copy is evaluated.
After constructing the boundary function, it is recalculated into the modulation transfer function. Based on the data obtained, the function of transferring the modulation of the copying process is built.
Rice. 3. An example of the transfer function of the modulation of the copying process
The presented method makes it possible to assess the capabilities of plates for reproducing images with elements of various sizes under specific exposure conditions.
2. 3 Gradation characteristic
Gradation measures the quality of a bitmap image reproduction. It is expressed by graphical dependence, which in most cases characterizes the reproduction of a raster image on a printed form in comparison with an image on a photographic form:
where and are the relative areas of raster elements on the printed form and the photographic form, respectively.
To build a gradation dependence, it is necessary to measure the relative area of raster elements on a printed form, obtained by copying stepped raster scales with different lineatures, consisting of fields with a change in increments, usually 5 or 10%; in high highlights and deep shadows, the step can be 0.5 or 1%.
Methods for assessing the gradation characteristic.
The gradation characteristic is determined at optimal exposure and processing modes of copy layers and characterizes the fidelity of reproduction of the original information in highlights (including high tones), halftones and shadows (including deep ones).
printing offset graphic image
3. Factors affecting reproductive-graphicindicators
The quality of printed forms is assessed through reproduction-graphic indicators, which, in turn, are influenced by the parameters of the copy layer, the microgeometry of the surface of the plate substrate, the conditions of exposure / development, the screening ruling (the greater the ruling, the more distortions).
The influence of most of the above factors associated with the nature of the distribution of radiation during exposure of the layer or its change in the reproduction system: radiation source - photoform - plate. This influence manifests itself through a change in the illumination zone under the dashed / raster elements, which lead to a change in the original dimensions of the elements, which affects the reproductive and graphic indicators.
For positive copy layers, for example, with increasing exposure, there is a decrease in the resolution and highlighting and an increase in the distortion of the gradation characteristics, moreover, the distortions with an increase in the exposure value increase and the greatest distortions occur in the area of highlights and halftones, which is associated with a decrease in the contrast of the raster image due to changes in raster dot configurations.
The influence of the development modes, as a rule, affects the reproductive-graphic indicators to a lesser extent than the influence of the exposure modes. The effect of the thickness of the copy layer can be determined using geometric optics. The higher the thickness of the copy layer, the higher the resolution. It can also be explained on the basis of the following: with an increase in the thickness of the copy layer, a large exposure is required to ensure physical and chemical transformations. Increasing the exposure leads to increased light scattering, and hence the resolution decreases.
4 . Facilitiescontrol of reproductive and graphic indicators
Reproduction and graphic indicators of printed forms allow you to evaluate the quality of reproduction of details of raster and line images.
Control test objects are a means for controlling the quality of forms. .
They are presented in digital form and contain a number of fragments for various purposes for visual and instrumental control:
Information fragment with constant information about the test object itself and variable information with current data about specific recording modes;
Fragments containing objects of pixel graphics for visual control of the reproduction of image elements;
Fragments that allow assessing the technological capabilities of the recorder and the raster processor, as well as the reproduction and graphic indicators of printed forms.
4.1 Controlprinting plates of flat offset printing, made on photosensitive plates
For recording on these plates, radiation with a wavelength of 405-410 nm (violet region of the spectrum) is used. Distinguish between electrophotographic (currently little used due to low quality), photopolymerizable and silver-containing plate. Currently, as photosensitive plates are used plates with a photopolymerizable layer and a silver-containing layer. They have a fairly high sensitivity. Plates with a silver-containing layer are more sensitive and have better properties than plates with a photopolymerizable layer. Laser radiation ensures that certain processes occur in the receiving layers of light-sensitive plates, which are the result of exposure to light. As a result of exposure to light, electrophotographic and photochemical processes take place in the receiving layers of the plate. In photopolymerizable plates under the action of laser radiation in the areas of its action, crosslinking of macromolecules of the photopolymerizable layer is observed. In this way, ink receiving elements are formed.
For first generation photopolymerizable plates, after exposure, heating is required, as a result of which the polymerization process is completed and the resistance of the exposed areas to the action of the developer increases. Subsequent processing includes washing, followed by removal of the protective layer, development in solutions and gumming. Gap elements are formed on the surface of the substrate after development. Second generation photopolymerizable plates do not require heating after exposure.
Silver-containing plates are widely used today, the formation of printing elements on which is carried out as a result of the diffusion of silver complexes. Under the light action of the laser, the silver halide particles are activated and, upon development, interact with the gelatin that is part of the emulsion layer, forming stable bonds with it. In this case, in unexposed areas, silver halide particles, on the contrary, acquire mobility and the ability to diffuse. Diffusing from the emulsion layer through the barrier layer to the surface of the substrate, these particles form printing elements on it. During the subsequent rinsing with water, the emulsion layer and also the water-soluble barrier layer are washed off from the substrate on which the blank elements are formed.
To assess the reproductive-graphic characteristics of printing plates made using digital laser technology, the Agfa Digi Control Wedge test object is used, shown in Figure 5.
Figure 5 - Structure of the Digi Control Wedge Afga test object
1 - focus control element; 2 - exposure control scale; 3 - element for control of reproduction of line elements; 4 - raster scale (independent of RIP); 5 - "working" raster scale, reflecting the set raster and RIP adjustments; 6 - window with information about rasterization; 7 - information window.
The exposure control scale consists of 6 circular fields that contain raster elements arranged in a checkerboard pattern. Each field contains bitmap elements with sizes from 11, 22 to 66. The background around the fields consists of 88 bitmap elements and serves for visual comparison with round fields. All fields, including the background, are made up of raster dots. The exposure is assessed by visual control, comparing the round fields of fragment 2 of the test object with the background: with a correctly selected exposure, the round fields merge with the background, with an incorrectly selected one, the round fields are clearly distinguishable against the raster background.
4.2 Inspection of flatbed offset printing plates made on heat-sensitive plates
Heat-sensitive plates are used for digital recording of printing plates with infrared laser radiation with a wavelength of 830 nm. The thermal effect of this wavelength range stimulates thermal processes in the receiving layers of the plate, as a result of which the absorbed laser radiation energy increases the temperature of the layer to values that ensure the occurrence of certain transformations in the layer. Depending on the nature of the receiving layer and the radiation wavelength, these transformations are accompanied by thermal destruction, thermal structuring, a change in the state of aggregation, or inversion of wettability.
In contrast to light exposure, which is characterized by the presence of light scattering during recording, during thermal laser exposure, as a result of point heating of the layer, secondary heating is observed due to jets of incandescent decomposition products in the region adjacent to the area of laser exposure. The influence of the process of propagation of high temperature, due to the inertia of thermal processes, can be eliminated by, for example, increasing the speed of movement of the laser spot (aberrations when exposed to light radiation cannot be eliminated). Due to this, when using thermal influence, it is possible to achieve a higher quality of reproduction of line and raster elements - their images are distinguished by higher sharpness.
Technological processes for the manufacture of printing plates on thermosensitive plates of various types differ from each other in that in cases of thermal destruction or structuring in the layers, processing in solutions is mandatory. Form plates, in the receiving layers of which, under the influence of IR radiation, a change in the state of aggregation (for example, as a result of sublimation) or inversion of wettability is observed, such processing is not required. This distinctive feature of the last two types of thermosensitive plates makes it possible to use them in technologies for digital recording of printing plates according to the "computer-printing machine" scheme.
As a result of the implementation of the recording process and carrying out "wet" processing (if necessary), printing and white space elements are formed on the forms. If the recording process is accompanied by thermal destruction or thermal structuring of the receiving layer, then after development in solutions, printing elements are formed on the layer itself, whitespace - on a hydrophilic substrate. On thermosensitive plates, on which the process of thermal destruction is realized, blank elements are formed after the dissolution of the layer in the areas of exposure to radiation. On the contrary, during the structuring process, the printing elements are formed in the areas of exposure to radiation, and these plates, after exposure, can be subjected (if necessary) to additional heating. If the structure of the plate includes a coating that contains thermally active components that exclude incomplete stitching of the exposed areas, then preheating is not required. The sublimation process, accompanied by a change in the state of aggregation, is used to record printing plates.
To assess the reproductive-graphic characteristics of printing plates of various types, made on heat-sensitive plates, a method based on the use of the UGRA / FOGRA Digital Plate Control Wedge test object is used (Figure 6):
Figure 6 - Test object UGRA / FOGRA Digital Plate Control Wedge
1 - information field; 2 - fields for control of resolution; 3 - fields for focusing control; 4 - fields of geometric diagnostics; 5 - fields for visual control of exposure; 6 - fields for control of reproduction of the image tone gradations.
Fragment 2 represents areas consisting of two semicircular elements: in one of the elements, an image consisting of positive lines radiating out from the center is twice the width of the nominal scan.
Fragment 4, an enlarged image of which can be seen in Figure 7, consists of six columns with elements, the dimensions of which are set within the width of the nominal scan line. The first two columns contain a line raster, and the width corresponds to the value, one (in the first column) and two times (in the second column) scan line width; strokes are located horizontally and vertically.
Figure 7 - Enlarged image of fragment 4
Fragment 5 (Figure 8) consists of fields in the form of rectangles with a procellular breakdown 44 with a checkerboard filling, placed inside half-tone fields with S rel from 35% to 85% with a step of 5%. Under optimal playback conditions and ideal gradation, the staggered fields coincide with the 50% field. The fragment is also used to control the stability of the process of recording printing plates.
Figure 8 - Enlarged image of fragment 5
Fragment 6 (Figure 9) consists of raster fields with S rel from 0% to 5% (with a step of 1%), then from 10% to 90% (with a step of 10%) and from 95% to 100% (again with a step one%).
Figure 9 - Enlarged image of fragment 6
After recording the test object on the receiving layer of the printing plate and carrying out the corresponding processing, the following parameters are measured: the size of the reproduced strokes of the elements and the interval of reproducible gradations.
Conclusion
In this course project, the general classification of forms of flat offset printing and the main methods of their manufacture are considered in detail. Currently, there are various methods of making printing plates, each of which has its own advantages and disadvantages. Manufacturers offer a large number of types of plate, which differ in their characteristics. This kind of forms and their characteristics require their own method for controlling the quality of printed forms. The quality control method can be both visual and hardware. It should be noted that for flat offset printing, the scales of test objects give both a qualitative and a quantitative assessment.
The main indicators of the quality of printing forms, the factors influencing them, and equipment for quality control have been analyzed. Modern technical means (densitometers, digital microscopes) allow high-precision measurements.
Bibliography
1. Polyansky N.N., Kartasheva O.A., Nadirova E.B., Busheva E.V. Form process technology. Laboratory work, part 1. M .: MGUP, 2004 .-- S. 35-36
2. Polyansky N.N., Kartasheva O.A., Nadirova E.B. Form process technology. M .: MGUP, 2010 .-- P. 366
3. Polyansky N.N., Kartasheva O.A., Nadirova E.B., Busheva E.V. Form process technology. Laboratory works. Part 2.M .: MGUP, 2005. - P. 18
4. Kartasheva O.A. Digital technologies of plate offset printing processes. / Kartasheva O.A., Busheva E.V., Nadirova E.B. ? Moscow: MGUP, 2013.? 71s.
5. Gribkov A.V. Technique for printing production. Part 2. Pre-press equipment. / Gribkov A.V., Tkachuk Yu.N. ? Moscow: MGUP, 2010.? 254s.
6. Samarin Yu. N. Pre-press equipment: Textbook for universities. - Moscow: RITs MGUP, 2012.? 208s.
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abstract
Photopolymer plates, exposure, laser engraving, flexographic printing, negative copying, finishing.
The object of analysis is flexographic printing plates.
The purpose of the work is to compare the main features of the manufacture of printing plates flexographic printing.
In the process of work, the features of the structure and manufacture of forms were considered. A separate chapter is devoted to the problems of choosing technologies, materials and equipment arising from flexographic printing.
The results of the comparison of printing plates revealed the advantages and disadvantages of technological processes, and the optimal method of making a plate for the presented sample was chosen.
Introduction
1. Technical characteristics of the product
2. General technological scheme of product manufacturing
3. Comparative analysis production of polymer forms for flexographic printing
3.1 Development history of flexographic printing
3.2 Types of plates
3.3 General schemes making printing plates in various ways
3.3.1 Negative copying
3.3.2 CTP Technologies
3.3.2.1 Direct Laser Engraving Technology (LEP)
3.3.2.2 Indirect laser engraving
4 The choice of technology, equipment and materials for the manufacture of a sample
4.1 Process selection
4.2 Selection of basic equipment
4.3 Selection of materials
4.4 Technological instructions
5. Calculation of the number of printed forms per circulation
Conclusion
List of sources used
Applications
flexo printing technology polymer
Introduction
The share of flexographic printed products is increasing every year. Today flexo printing is used in printing on cardboard boxes, on corrugated board, when sealing flexible plastic packaging and even in newspaper production. This is primarily due to the economy of the process itself, with the possibility of obtaining high quality multicolor products, low waste paper yield, low investment and much more.
In obtaining any printed original, there is certainly a stage of making printing plates. Forming processes are one of the most important stages at which the quality of future products is determined. Achieving a high-quality printing plate requires the use of special plate materials and their careful processing.
Currently, Russian enterprises have begun to widely use Computer-to-Plate (CtP) technology, which is the main method of manufacturing printing plates in European countries. This technology makes it possible to exclude the production of photoforms from the process, which leads to a reduction in the terms of production of printing plates. The introduction of CtP technology allows to improve the quality of the image on printing plates and improve the environmental conditions at the printing enterprise.
The work will consider the main technologies for the manufacture of flexographic printing plates. Based on the analysis of these technologies, the optimal method of making a printing plate will be selected and the corresponding technological instructions for the selected sample.
1. Technical characteristics of the product
I chose a label as a sample, since it is the flexographic printing method that is beneficial to print this type of product. Flexographic printing is currently the only way which can cost-effectively seal almost all materials used in packaging products, while ensuring high print quality at the same time.
Table-1 Product Specification
2. General technological scheme of product manufacturing
1. Processing of text and graphic information:
Entering information
Information processing by means of Word, Photoshop
QuarkXPress page layout
Descent of the bands
Writing a PS file
Output of negative frosted film
2. Making a photoform:
Exposure
Development in alkaline solution
Anchoring in an acidic environment
Rinsing with water
3. Making a printing plate:
Incoming inspection of equipment and materials
Back flare
Main exposure
Manifestation
Drying at to40-60oC
Additional exposure
Finishing
4. Printing of the circulation:
Colorfulness 4 + 0
5. Post-printing processes:
Waxing
3. Comparative analysis of the production of polymer forms of flexographic printing
3.1 Development history of flexographic printing
The development of this method began in the USA, where flexography, due to the specific attitude to packaging, came to the court. Since originally aniline synthetic dyes were used in this printing method, the method was termed "aniline printing" or "aniline rubber printing". The generally accepted term "flexography" was first proposed on October 21, 1952 in the USA at the 14th National Conference on Packaging Materials. In this case, it was assumed that aniline dyes should not be used in this method at all. The term was based on the Latin word flex-ibillis, which means "flexible", and the Greek word graphlem, which means "to write", "to draw".
It is difficult to name the exact date of the invention of flexography. It is known that as early as the middle of the 19th century, aniline dyes were used in wallpaper printing. Aniline is a poisonous, colorless, slightly water-soluble liquid. Aniline dyes were used mainly in the textile industry. The concept of "aniline dyes" was later extended to all organic synthetic dyes in general. But now this concept is considered obsolete.
Another important technical prerequisite for the emergence of flexography was the invention of elastic rubber molds. They were intended for the manufacture of rubber stamps. The main material for the implementation of the method was natural rubber - an elastic material of plant origin. Currently, synthetic rubber is the basis for the manufacture of rubber printing plates.
A new stage in the development of flexography began around 1912, when they began to make cellophane bags with inscriptions and images on them, which were printed with aniline inks.
The expansion of the scope of flexography was facilitated by certain advantages of this type of letterpress printing method over classical methods, especially where it was not required to obtain high-quality prints. Forms of letterpress printing were previously made only of wood or metal (typographic alloy - hart, zinc, copper), but with the advent of flexible printing plates in flexography, printing plates began to be made in letterpress from photopolymers as well. The difference between printing plates of classic letterpress printing and flexography is only in the hardness of the printing elements. Even such a small difference in physical properties "hard-elastic" has led to a strong expansion of the field of application of fundamentally the same printing methods.
Flexography combines the advantages of letterpress and offset printing and, at the same time, it is devoid of the disadvantages of these methods.
In 1929 flexography was used to make envelopes for phonograph records. In 1932, automatic packaging machines with flexographic printing units appeared for packaging cigarettes and confectionery.
Since about 1945, flexographic printing has been used to print wallpapers, promotional materials, school notebooks, office books, forms and other office documents.
In 1950, a series of paperback books began to be published in Germany in large editions. They were printed on newsprint, on a roll-fed rotary machine of aniline (in two years time it will be called flexographic) printing. The cost of books was low, which allowed the publishing house to sharply reduce prices for book products.
Around 1954, flexography began to be used for the manufacture of postal envelopes, Christmas cards, and especially durable packaging for bulk products.
For almost the entire 20th century, improvements continued in both the printing processes and materials used to make flexible printing plates, and the design of printing presses for flexographic printing.
Flexography has developed rapidly over the past 10 years. According to numerous sources, this type of printing occupies a market share of 3% to 5% in all divisions of the global packaging industry, and in the printing industry is rapidly approaching 70% of all packaging printed products. Technological developments in photopolymer materials, ceramic raster rollers, squeegees and inks have literally turned and accelerated the evolutionary scenario for flexo printing.
The catalyst was the achievements of the chemical industry in the field of photopolymers and printing inks; they were supplemented with especially thin multilayer mold materials. The purpose of creating these materials was to improve the quality of flexographic printing. /one/
3.2 Types of plates
Flexographic printing is a method of high direct rotary printing from elastic (flexible rubber, photopolymer) embossed printing plates that can be mounted on plate cylinders of various sizes. Using a roller or rasterized cylinder interacting with a squeegee, they are coated with liquid or paste-like fast-drying (water-soluble, volatile) printing ink and transferred to any kind of printing material, including non-absorbent materials. The image on the printing plate is mirrored.
Improving print quality is one of the reasons for the use of different plates in flexography. It is it that makes demands on the properties of the plates. Modern forms can tolerate a uniform ink film when printing solid fill areas (dies) and give very little dot gain when printing text, line and bitmap images. Further requirements are clear elements on the inversion (the technique of making a printing plate from a line iso-original, when you need to get a negative, inverted image on the print: white strokes on a black background), the absence of ink blocking the blank areas of the form and the best gradation of halftones on the print.
Initially, printing plates were made by matting from rubber, and after the creation of photopolymers, by exposure and washing.
However, there is one more method that is still used for the manufacture of author's forms in linocut. On linoleum or on a polymer material similar to it, the author engraves an image from lines and surfaces of various sizes, removing the material and deepening the background. The image turns out to be convex, and all the elements towering above the background lie in the same plane. And what is this if not a letterpress printing plate? And since the printing elements are elastic, this is the printing plate for the flexographic printing method. Of course, printing plates are not made of linoleum for industrial purposes.
The development of technology for printing plates is going in three main directions. These are flexible packaging printing, label printing and direct printing on finished corrugated board.
In these three areas, different plates are used depending on the substrates, compression pads or tapes used, the plate material, its thickness and hardness, the plate's resistance to ink solvent swelling, quality requirements, material compatibility, and the design of the printing press.
For direct printing on finished corrugated board, plates with a thickness of at least 3 mm are used and then they are considered as a technology of thin printing plates. When printing labels and on flexible packaging, plates are considered ultrathin, less than 1 mm thick.
Plates 2.54 mm thick are mounted on a thin backing or foam tape 0.50 - 0.55 mm thick. Accordingly, plates of this thickness in combination with a cushioning substrate are considered to be printing plates on a soft tape.
Thin wafer technology means a "flexible substrate", which is the anchorage of the printing plate. This compression backing generally consists of a combination of textile fibers and rubber, with the rubber grades in the individual backings differing in specific features. Several layers of material have been selected to optimize the entire system “printing plate - substrate - printing surface - gap between plate and impression cylinders”. The material consists of a rubber base, two fibrous intermediate layers for stabilization and a compressible polymer microporous layer. The total thickness of the structure is no more than 2 mm.
This material, which is a type of double-sided adhesive tape with a compression polyurethane foam lining inside, can be used with almost all types of flexo plates, protects the printing plate from wrinkles and at the same time ensures its easy positioning during installation and keeps it in the correct position throughout the entire print run. ...
Another type of application for thin printing plates is sleeve technology. Unlike traditional technology, it has the advantage of being reusable. This system uses the principle air cushion when installing the liner on the gravure cylinder.
In flexible packaging printing, multilayer plates can be used as an alternative to thin printing plates, since both have a similar structure. These plates combine in their structure a thin shape and a compressible substrate. They consist of a lower protective film, a carrier elastic layer, a stabilizing film, a photosensitive embossing layer and an upper protective film. For high quality flexographic printing, this multi-layer plate structure has many advantages.
However, in the case of using chemically active paints, for example, based on ethyl acetate, elastic rubber molds must be used. Conventional alcohol-resistant forms made from photopolymer plates are not suitable for ethereal paints. For this purpose, ether-resistant photopolymer plates can be used.
One of the features of flexography is that pressure is needed to print and to level the unevenness of the contacting surfaces during the printing process. These are technological requirements. And the more pressure, the better it is for achieving the ultimate goal. On the other hand, the higher the pressure, the greater the distortion of the geometry of the printing elements. These violations of the printing plate, due to high pressure, lead to a decrease in the quality of the print - high dot gain, smearing, uneven distribution of ink on the solid. High pressure affects the print life of the plate and can lead to delamination. It is clear that a compromise or a new idea is needed here.
When using conventional plates, excess pressure is partially absorbed by them. As a result of deformation of the top photopolymer layer of the printing plate, dot gain occurs, which must be reduced if high-quality raster works are printed.
To achieve this, thin plates within 1mm thick are used for printing on labels and packaging. In this case, most of the excess pressure is absorbed by the compressible substrate, and thus the degree of deformation of the recording elements in the area of the printed contact is reduced due to the compressibility of the substrate, which leads to a significant improvement in print quality.
The term "compressibility" ("compressibility") means the compensation of pressure through a decrease in volume. Accurate restoration of the substrate to its original size has a load-balancing effect. In other words, the material used for the manufacture of printing plates for flexography must be capable of highly elastic deformations.
Compressible sleeves, which are used in packaging printing, have a surface consisting of a compression layer that does not lose its properties even after several years of use. The effect of the foamed structure is that a significant part of the pressure acting on the mold is absorbed by the substrate. Therefore, the relief of the printing plate is kept more stable while the compressed foam straightens to its original height after passing through the printing nip. This allows you to perform raster, line and spot jobs from the same shape.
The main characteristics of the printing plate are thickness, stiffness and hardness, which are closely related. The hardness of the same material increases with decreasing thickness. At the same time, different materials of the same thickness can have different stiffness. Thinner, stiffer plates are better at rendering the bitmap dot, but they are more difficult to work with. For smooth print media, it is better to use more rigid shapes when printing bitmaps than when printing strokes and text. Therefore, it is necessary to flexibly use different types of plate in the manufacture of printing plates.
Thus, the essence of flexography is a feature of the printing plate, everything else works for it, enhancing the positive factors. /one/
In conclusion, I want to say that in order to obtain high-quality printed products, three factors must be coordinated with each other, namely, the choice of a printing plate, an ink system and a screened (anilox) roller. The choice of thick or thin plate, water-based or UV-curable ink and the required screening roller for uniform ink transfer to the plate are critical to the quality of the printing process.
3.3 General schemes for the manufacture of printing plates in various ways
Flexographic printing plates are manufactured in several ways. Let's take a look at some of them.
3.3.1 Negative copying
For negative copying, photopolymer plates (Fig. 1) of various thicknesses from 0.76 mm to 6.5 mm and stiffness are used. The stiffness of the plate depends on its thickness.
Structural diagram of the plate
1- protective layer;
2- liquid photosensitive photopolymer copying layer;
3- adhesive sublayer;
4- polymer backing.
The first stage of the copying process is exposure (Fig. 2) of the reverse side of the plate, which is performed through the base film without the use of vacuum / 2 /. It is carried out with UV radiation of a certain wavelength (about 360 nm) to form the base of future printing elements, to form active centers, increase photosensitivity and ensure the correct trapezoidal shape of the printing elements / 3 /.
Scheme of manufacturing a printing plate
The exposure time depends on the required relief depth and is selected by trial and error.
If small dots and thin lines are reproduced, a flatter relief is required, for which the duration of the pre-exposure should be increased / 2 /.
The main exposure is the second stage of processing in the production of photopolymer printing plates and should be done immediately after the exposure of the reverse side.
Before making the main exposure, remove the protective film from the plate.
The main exposure is done through a negative photographic form. The relief is formed as a result of polymerization. Raster dots, text and thin lines present on the negative photographic form in the form of transparent areas are copied onto the plate. You cannot make changes to the resulting copy.
A test exposure must first be performed to accurately determine the exposure duration. This requires test negatives / 2 /. Tests can eliminate differences in tonal values and reduce the risk of misjudging a copy.
The following factors affect the duration of the main exposure:
- point base area
- angle of inclination of the wall
- the presence of solid areas with saturated color
If the exposure time is too short, an acceptable embossing base cannot be formed on the pre-exposed backside of the wafer because there is no through-curing. Thus, a soluble region is formed, which is subsequently washed out together with raster dots. First of all, small dots and thin lines are washed out.
In addition to the need for optimal formation of the relief walls, special attention should be paid to the continuous intermediate areas of the image.
The solid saturated areas present on the negative are most at risk of overexposure, resulting in such areas being printed solid.
The development process consists in the removal of unpolymerized parts of the mold with the help of a solvent. Various mechanical devices, brushes or soft scrapers are auxiliary in the washing process.
Development is carried out in 3 stages:
Swelling of the polymer
Removal of polymer
Washing a copy / 3 /
The washout process should be as short as possible. The longer the contact with the solvent, the deeper the relief.
If the washout lasts too long, the relief may be damaged, there may even be signs of separation. Destruction is possible even with the wrong choice of solvent. The optimal time is determined empirically.
Drying is carried out in a special drying cabinet.
During drying, the washout solution penetrated into the relief coating evaporates under the influence of warm air at t0 40-60 С0. the longer the drying time, the higher the print stability and print stability.
After drying, the flexo plate must be kept at room temperature for about 12-15 hours for it to fully regain its size. We recommend leaving the plate overnight at room temperature.
During the main exposure, depending on the nature of the image, more or less light is effective. As a result, the level of polymerization in certain areas of the image may be insufficient.
Therefore, additional exposure is carried out - exposure to UV radiation (360 nm) of the entire surface of the form in the absence of negative for the complete polymerization of the printing elements of the form and to increase its print life.
During additional exposure, insufficiently polymerized zones are fully associated with the resulting relief, forming a printing plate uniform in terms of characteristics and hardness.
Finishing is the last stage of manufacturing. Carried out in UV light (256 nm). Finishing is necessary to close the pores, which eliminates the stickiness of the printing plate and increases the stability of properties.
The disadvantage of this method is the possible distortion of the thickness of line and raster elements when exposed to diffused light, as well as inaccuracies in the exposure.
In 2000, DuPont proposed a heat treatment technology for exposed copies, CyrelFast / 3 /.
Heat treatment technology is a “dry” method for making flexographic printing plates. This technology can be implemented both in analog and digital versions, taking all the advantages of digital technology. Heat treatment technology (FAST) involves the use of special photopolymerizable plates made of thermosetting photopolymer, which is removed from the blank elements using heat.
The technological process of making printing plates is similar to the traditional one. To obtain a latent image on a photopolymerizable plate, traditional equipment is used. The plate is exposed in a conventional copy frame. New is the method of removing uncured material from the blank elements, for which a special processor is used. The plate is placed on a cylinder in the processor, where, under the influence of an IR heater, unexposed areas are softened and removed from the plate. This is done by using a non-woven roll material, which is pressed against the surface of the plate using a rubber roller. The process of removing material from the blank areas of the form takes several minutes, while a relief of up to 0.8 mm is achieved. The use of heat treatment technology makes it possible to obtain molds using "dry" processing, while there is no process of washing out with the use of solvents. This eliminates the need for a lengthy drying operation, and the production time of the printing plate can be reduced by up to 25%.
The disadvantage of heat treatment technology is currently limited in thickness range of plates, rather high cost of non-woven material and unresolved issues of processing or disposal of contaminated non-woven material / 4 /.
3.3.2 CTP Technologies
Filmless methods of making flexographic printing plates by laser recording provide sharper and denser raster dots and, ultimately, provide a significant improvement in print quality due to significantly higher gradation and image contrast with better light processing. Thin negative and positive line elements are reproduced with high accuracy / 5 /.
At its core, CtP technology is a computer-controlled process for making a printing plate by directly writing an image onto a plate material. This process, implemented using single-beam or multi-beam scanning, is characterized by high accuracy, since each plate is the first original copy made from the same digital data. As a result, it is possible to increase the sharpness of the dots, the accuracy of register and reproduction of the entire tonal range of the original image, to reduce the dot gain of the raster dot, and also to significantly speed up the preparatory and fitting work on the printing press.
Manufacturing of flexographic printing plates using ComputertoPlate technology can be carried out in two ways: direct laser engraving of flexographic plates and using masked photopolymers.
3.3.2.1 Direct Laser Engraving Technology (LEP)
Direct Laser Engraving (LEP) technology uses a special non-photosensitive elastomer polymer plate with above average hardness. This technology combines high-quality polymer material and a fast way of processing it using a laser / 4 /.
The technology is based on the use of a modern and powerful laser such as CO2, which has been found to be the most suitable for direct laser engraving.
Direct laser engraving technology includes only one operation - the blank elements on the plate are burned out with an IR laser by sublimation, after which the form is ready for printing (Fig. 3).
Direct laser engraving diagram
D and f - aperture and focal length of the lens;
θ - beam divergence; d0 - spot diameter
Although this technology is fundamentally simple, it has a number of advantages:
1) savings on equipment and materials are achieved,
2) time of mold making is saved,
3) direct transmission of data from a computer using a laser makes it possible to practically eliminate possible errors.
The mold making process boils down to the following: the plate is placed on the cylinder for laser processing without any pre-treatment. Blank elements are burned out immediately during laser irradiation.
During processing, the depth of the relief and the profile of raster dots are controlled - that is, the probability of loss of small details is minimized. After engraving, dust particles must be removed from the mold using a special vacuum cleaner or rinsing with running water. The produced printing plates have an increased circulation life and durability, as well as high graphic possibilities. The time for making a mold in A4 format is about 1 hour.
Currently, direct laser engraving technology has several disadvantages. This is a limited range of plates in thickness, high energy consumption, the need to remove combustion products, the need to periodically replace the power elements of lasers and resistance not to all types of printing inks.
3.3.2.2 Indirect laser engraving
The production of flexographic forms using CtP technology with the use of masked photopolymers has become widespread in the production of high-quality printed products. As a basis for masked photopolymers, photopolymerizable compositions are used, which have proven themselves well in the analog production of printing plates. The main distinguishing feature of digital printing materials is the presence of a thin (several microns) mask coating that absorbs laser radiation. This coating is removed from the surface of the plate during exposure to an infrared laser. As a result, a negative image is created on the surface of the plate, replacing the photographic form during subsequent exposure to UV radiation. Since masked photopolymers are developed on the basis of traditional photopolymers for flexography, the processing processes are the same (Fig. 4).
Scheme of making a mold using laser recording of a mask
After the laser has removed the mask layer in the places corresponding to the printing elements, a transparent substrate is exposed in order to create the base of the photopolymer form. The embossing is exposed through the negative image created from the masked layer. Then the usual processing is carried out, consisting of washing out the uncured photopolymer, washing and additional exposure with simultaneous drying and finishing.
Reducing the technological cycle of making forms due to the absence of photographic forms allows not only to simplify the prepress process, but also to avoid mistakes associated with the use of negatives:
There are no problems arising from the loose pressing of the photoforms in the vacuum chamber and the formation of bubbles when exposing the photopolymer plates;
There is no loss of quality caused by dust or other inclusions between the mold and the plate;
There is no distortion of the shape of the printing elements due to the low optical density of photoforms;
There is no need to work with vacuum;
The profile of the printing element is optimal for stabilization of dot gain and accurate color reproduction / 6 /.
When exposing an assembly consisting of a photographic form and a photopolymer plate, in traditional technology, before reaching the photopolymer, light passes through several layers: a silver emulsion, a matted layer and a base of a photographic form, a film of a vacuum copying frame. In this case, light is scattered in each layer, as well as at the boundaries of the layers. As a result, raster dots get wider bases, which leads to increased dot gain. When exposing masked flexographic plates with a laser, there is no need to create a vacuum, moreover, there is no film. The almost complete absence of light scattering means that the image recorded with high resolution on a layer mask, accurately reproduced on a photopolymer / 7 /.
Thus, the advantages of printing plates made using the CtP technology and arising from the peculiarities of the printing process include the following:
1) exposure is carried out without vacuum;
2) there is no need to make a negative and use a special matte film;
3) there are no problems of loose fit of the negative during exposure due to incomplete removal of air, the formation of bubbles or the ingress of dust and other inclusions;
4) there is no loss of fine details due to insufficient optical density of the image and the fuzzy edge of the dots.
Thus, having considered these methods of making molds, we can say that one of the most advantageous is the method of indirect laser engraving. Because not only the process cycle time is reduced, but also there are no errors associated with the use of negatives, and there is no loss of fine details due to insufficient optical density of the image. The same cannot be said about negative copying, the main advantage of which is the use of plates of different thicknesses. Moreover, this method has many disadvantages. Because the depth of the relief is chosen empirically, there is a risk of overexposure, distortion of the thickness of the elements, which leads to inaccurate exposure. However, the main disadvantage is the large labor and time costs. Although in 2000 a “dry” manufacturing method was proposed, which reduced manufacturing time by 25%, due to the limited range of plates, high cost of materials and their disposal, this method has not received widespread use.
4. The choice of technology, equipment and materials for the manufacture of the sample
4.1 Process selection
When choosing the optimal technology for the manufacture of this sample, one should take into account the product format, its field of application, resolution, circulation and other factors that make it possible to obtain a product with lower economic costs and high quality.
Table-2 Comparison of the selected technological processes
Purpose of the process |
Possible process options |
Selected option | Justification of the chosen option |
| Manufacturing of a printing plate | Negative copying Indirect laser recording Direct laser engraving |
Direct laser engraving | The use of this method of making a printing plate allows you to abandon the photographic form. In addition, the environmental friendliness and productivity of the process is increased. Printed elements are obtained with a rectangular base, which makes it possible to significantly increase the accuracy of the development of a part without losing circulation resistance. Print run more than 1 million prints, resolution 12 - 70 lines / cm |
4.2 Selection of basic equipment
The equipment is selected taking into account its performance, the quality of the technological process, the degree of automation, ease of maintenance, estimated cost and energy intensity / 8 /.
Table-3 Comparison of the selected equipment
| Process or operation name | Types (brands) of possible equipment for performing the process (operation) | Selected equipment and its technical characteristics | Rationale for the choice of equipment |
| Manufacturing of a printing plate | FlexPose! Direct 250L |
Format 1500/1950 x 145 x 4500 The engraving depth is controlled by the operator Compatible with all types of inserts Laser 500 W |
The Morpheus 611X provides direct laser engraving capability for flexo printing plates. It is a versatile, highly accurate rubber and resin engraving system that uses a single laser beam to define a dot pattern. This setting is good for narrow web packaging printing, security printing, and fabric and wallpaper printing. Morpheus can be equipped with an optional YAG laser for LAM technology. |
| Print run | Mark Andy 2200 OFEM COLUMBUS 10 NIKELMAN 230 MULTI TWIN |
The machine allows high-quality full-color printing in a wide range of materials, from plastic films to lightweight cardboard. The printable area matches the maximum roll width to maximize productivity and minimize waste. Max. roll width, mm 178, 254, 330, 432 Max. number of printing units -12 Length of the printed surface, mm 140-610 Number of punching / nibbling sections -3 Material thickness (min / max.), Μm 30-300 |
|
| Waxing | PRA-50.000.SB |
For waxing paper Roll dimensions, mm: width - 840 - 900; Productivity, m / min - 180. |
4.3 Selection of materials
When choosing basic materials, one should be guided by the characteristics of the product, the method of printing and post-printing processing, and design. And also to compare the economic parameters of the consumption of materials, their cost, storage conditions.
Table-4 Comparison of selected materials
| Process name | Possible materials | Selected materials (indicating grades, GOST, OST, etc. and justification for the choice) |
| Manufacturing of printed forms | ||
| printed paper |
GOST 16711-84 For inner wrapping of confectionery |
|
|
UV Rainbow ZU-V 31 Bargoflex Seria 53-20 |
AKVAFIX– 123 Water-borne paint. It has four different modifications for printing on thin caramel paper, packaging for food products and the production of envelopes due to the low deformation of the paper from 25-100 g / m2. It can be used in work with both natural rubber forms and photopolymer materials. |
4.4 Technological instructions
1. Creating a layout:
Discussion and elaboration of the idea by the designer
Production and approval of sketches
Production and approval of the original layout
2. Creating a digital original:
Creation of complete decoration of the project
All production phases of order fulfillment are taken into account
3. Proof print:
Approval of the sample by the customer
4. Making a printing plate:
· A non-photosensitive elastomer is used in the form of a form material;
· Recording of the digitized information of the original with the help of an IR laser by sublimation, blank elements are burned out - 3-5 minutes;
· The remaining soot is sucked off with a special vacuum cleaner;
· Rinsing with running water - 12-18 minutes;
Drying - 10 minutes;
· Additional exposure - 3-10 min;
Finishing - 10 minutes;
· Quality control of the form;
5. Adjustment of the printing press;
6. Printing of the circulation;
7. Visual control of color rendering stability;
8. Post-printing processing:
· Rejection of circulation;
· Waxing;
· package;
9. Delivery of the circulation.
5. Payment quantity printed forms on the circulation
Calculation of the number of printing plates for a given format:
where nn is the number of stripes (20);
k - the brilliance of the product (4 + 0);
nprinting f. - the number of stripes on the printed form (20 labels on 1 form).
Fpech.f. = 4 shapes
Calculation of the number of installation plans:
where nmff is the number of stripes on the editing photographic form.
1 installation plan
Calculation of the number of printed forms:
where-N is the number of sets of identical printing plates.
where T is the circulation of the publication, thousand copies.
Tst is the circulation rate of the printed form in thousand copies. (N is rounded up to a whole number).
where k is the colorfulness of the edition
40 edition printing forms
Conclusion
Despite its hazy past and controversial quality, flexography is ideal for most types of packaging. In addition to flexography's inherent flexibility in media selection, another advantage is price. Photopolymer flexographic forms are much cheaper than metal gravure forms, and this is just one of the components of the relative cheapness of flexography.
Another advantage of flexography is its ability to handle various plate sizes, which optimizes the use of packaging materials, while fixed sizes of offset plates often lead to an increased percentage of waste.
In the course of this work, three methods of manufacturing PFPs were analyzed. Based on this analysis, the optimal manufacturing method was selected, combining economy and quality. Also, materials and equipment suitable for this technology were proposed.
When considering the main issue of this course work, it was revealed that today the most profitable methods are CTP technologies.
List of sources used
1 / Stefanov S. "FLEXOGRAPHY - the centaur of printing" / Publish.- 2001.- №1.
2 / Mitrofanov V. "Technique of flexographic printing" / M. - 2001. - 208 p.
3 / Dmitruk V. "Lectures on DFT"
4 / Sorokin B. "CtP systems in flexographic printing" / Copyright.- 2005.- №5.
5 / Filin V. "Packaging printing at the beginning of the new millennium" / ComputerArt. - 2000. - No. 6.
6 / "Basics of flexography" / Flexo Plus. - 2001. - №1.
7 / K. Marikutsa "Vivat, Koroleva, or determination of the parameters of the prepress process in flexography" / Flexo Plus. - 2002. - No. 5.
8 / Kargapoltsev S. "Form production: choice of equipment" / Flexo Plus. - 2000. - No. 1.
Improvement of plate materials for offset printing
In the field of improvement of molded materials, the main directions are: expansion of the assortment and production volumes of pre-sensitized monometallic plates of a new generation, which are distinguished by high circulation resistance; creation of materials for direct film-free production of printing plates; invention of forms for printing without moisture.
On the market of mold materials today there are a large assortment plates for various purposes: for small, medium and large runs; for negative and positive copying; highly sensitive plates for direct exposure in laser output devices; for the electrographic method of making molds. Various types of substrates are also available, in particular paper, plastic and aluminum substrates.
Recently in Ukraine there is a search for new materials and technologies for offset printing. So, UkrNIIPP named after T. Shevchenko (Lviv) created an offset plate material "Semele" intended for the manufacture of offset forms for printing small-circulation products on machines such as "Romayor" and "Dominant". This is a polyethylene terephthalate film with sequentially applied metal and photosensitive layers, its technical data are as follows:
Maximum spectral sensitivity, nm 320 ... 400
Exposure time at irradiance 50 W m ~ 2, s, no more than 60
Development time, s, no more than 50
Lineature of the reconstructed raster, lines / cm, not less than 48
Print run speed, not less than 100
Guaranteed shelf life, months, not less than 6
Offset printing plates are made by contact copying using a UV light source according to the "positive - negative" or "negative - positive" scheme. For the manifestation of forms, environmentally friendly weakly alkaline aqueous solutions are used.
UkrNIIPP named after T. Shevchenko also developed pre-sensitized monometallic offset plates on grained aluminum, obtained by a photomechanical method (Table 1). Plates are made with a photosensitive layer: positive - based on ortonaphthoquinone diazide or negative - based on acrylate copolymer. UkrNIIPP named after T. Shevchenko developed a technological process (Table 2) and equipment for the regeneration of aluminum offset plates of the following format:
minimum, mm 530x650
maximum, mm 700x85
thickness, mm 0.30.8
Table 1. Technical characteristics of pre-sensitized monometallic offset plates
|
Indicator |
Sensitized plates |
||
|
positive |
negative |
||
|
Plate format, mm |
|||
|
Base thickness, mm |
|||
|
Copy layer thickness, mm |
|||
|
Resolution, mm ~ 1 |
|||
|
Storage life, year |
|||
|
Exposure time, min |
|||
|
Development time, s |
|||
|
Print life of forms, thousand prints |
To implement this process, a set of equipment has been created, which consists of: FKP-1000 cuvettes for removing printing ink; leveling rollers FVN-85; FHO-85-1 installations for primary chemical preparation of the machine surface for the purpose of granulating the surface of an aluminum sheet (electromechanical or mechanical); FHO-85-11 units for further chemical treatment of the aluminum sheet surface; equipment for technological testing of regenerated plates (exposure unit and development of cells FKP-1000). The use of specialized equipment for the regeneration of aluminum plates will make it possible to normalize the technological process and increase work productivity. The production of high-quality reusable offset printing plates is guaranteed, which will significantly reduce the cost of printing products, ensure the conservation of aluminum, and also reduce foreign exchange costs due to the lack of production of printed aluminum rolled products and pre-sensitized offset plates in Ukraine. Joint-stock company "Polygraphia" (Moscow) has developed a technology for the manufacture of pre-sensitized offset printing plates with a positive photosensitive layer on mirror-like aluminum. The basis of the plates is a tape made of AM-2 aluminum alloy of increased strength, the surface of which is processed by the method of dry brush granulation. The plates have good gradation and make it possible to easily recreate fine details of the image in any type of printed matter (in particular, highly artistic graphic). The technical characteristics of the plates, which are manufactured by the Dmitrivsky Research Plant of Aluminum Tape (Dmitriv, Moscow Region), are as follows:
Format, mm:
minimum 1050х7
maximum 1160х1420
Plate thickness, mm 0.3
Base strength, MPa 255 ... 335
Roughness of the base surface, μm 0.5 ... 0.7
Photosensitive layer thickness, μm 3
Shelf life, hour 1
Resolution, mm 25
Print life of forms, thousand prints:
without heat treatment of the photosensitive layer 50 ... 70
with heat treatment 250
Scheme of the technological process of regeneration of offset printing plates
offset printing sensitized
Printing plates made on these plates have high printing and technical properties and can be used on flat and web offset presses.
The Moscow State Academy of Printing and JSC "Polygraphy" have created multilayer offset plates intended for printing information reproduction in output devices with energetic laser radiation of the visible spectrum. The composition of the plates: a substrate, a copying layer based on ortonaphthoquinone diazides, a photoreceiving layer based on silver halide. The main technical data of these plates, which are manufactured by the Moscow plant of technical photographic plates, are as follows:
Spectral sensitivity in any visible area
radiation spectrum "0.44 ... 0.8
Resolution, mm "" up to 30
Print life of forms, thousand prints 100
The use of multilayer offset plates makes it possible to:
to reduce the technological process of issuing publications;
reduce the range of equipment and materials used, and production area and the number of employees;
develop a technology for a fully automated prepress process;
to use for image registration output devices with a visible radiation spectrum, which provide low energy consumption, high speed and the accuracy of the recording.
A number of foreign manufacturers of pre-sensitized offset plates are increasing their production capacity, putting into operation new factories and supplying new, improved types of these plates to the world market. The annual growth in the production of pre-sensitized offset plates is estimated at 4 ... 6%. Thus, according to the data presented in the literature, the world market for these plates in 2006 was 200 million m2, of which Europe accounted for 65 million m2, Japan - 70 million m2, and North America - about 50 million m 2. Almost all manufacturers of pre-sensitized offset plates produce equipment for their exposure and processing. High quality design and compactness are characteristic of modern models of this equipment. They are controlled by a computer, which makes it possible to automate the process of processing the plates.
The leading position in the world in terms of the volume of production of offset printing plates until 2006 belonged to the German concern Hoechst, which produced such plates as Ozasol No. 7, Ozasol No. 8, Ozasol No. 90. The first is a negative photopolymer, and the second is known as the first high sensitivity offset printing plate for projection and laser exposure. Form plate "Ozasol No. 90", which was first demonstrated at the exhibition "Drupa 90", is intended for the production of FOPP using the ctp technology.
High quality plate "Agfa Ozasol". In 2006 p. Belgian concern "Agfa-Gevaert N.V." became the owner of the enterprises of one of the most famous and most popular manufacturers of monometallic plates in the world - Kalle-Albert, which previously belonged to the Hoechst company.
A significant event in 2007 was the purchase by this company of another manufacturer of offset plates - a department of the DuPont company, which specialized in this production. Over time, Agfa firmly established itself as one of the leading manufacturers of offset plates in the world. Today there are factories for the production of Ozasol printing plates in Germany, Italy, the USA, Brazil and South Korea.
Of all the offset plates produced by the Agfa company, Agfa Ozasol plates are supplied to the Ukrainian market.
The assortment of plates produced under the Agfa Ozasol trademark contains a number of positive and negative materials for various purposes. They differ in the type of copying (positive and negative), circulation (test, short and high circulation printing), exposure method (traditional in UV rays and laser using computer-to-plate technology) and other characteristics. The list of plates that are in greatest demand today is given in table. 3. Agfa Ozasol pre-sensitized metal plates have won well-deserved recognition in the world market for their excellent printability. The combination of precision electrochemical granulation and a strong anode layer on the surface of the plates ensures their ideal behavior in the printing press (no oxidation and condensation), as well as excellent reproduction of even the smallest details at a high circulation life.
The most common and versatile inserts are P5S positive grades. They are considered standard multipurpose plates, work well in both web and sheet-fed presses, consume a small amount of dampening solution and quickly achieve optimal ink-water balance. The main technical parameters of P5S plates are given in table. 4.
Production of offset pre-sensitized plates "Ozasol P5S" is a complex multistage process, in which each operation is aimed at achieving high quality printed products. Aluminum base with a thickness of 0.15 or 0.3 mm, obtained by cold rolling, lends itself to complex electrochemical processing, which consists of several stages:
processing the plate in an alkaline solution to clean the surface;
electrochemical granulation under the influence of a high voltage electric current (several tens of thousands of volts) in special baths. Thus, a porous structure of aluminum is created, which ensures good adhesion of the plate surface to the photosensitive layer. In addition, the crystal structure of the surface is the basis for the formation of the desired level of resolution. Also, at this stage, the prerequisites for hydrophilicity (ability to humidify with water) are created;
anodizing (build-up of an oxide film on the microporous structure of aluminum to provide the surface with the strength necessary to exclude mechanical and chemical damage during printing). The oxide film is characterized by high adsorption properties, which guarantees strong adhesion to the copy layer and determines a high print plate circulation rate (100 thousand prints without heat treatment), and also ensures stable hydrophilicity of intermediate elements. At the same time, the surface strength increases approximately 1000 times, and also creates favorable conditions for an optimal ink-water balance during printing;
the filling of the oxide film gives the intermediate elements stable hydrophilic properties, reduces the excess porosity of the surface, and increases the plate circulation life.
A micropigment photosensitive copying layer based on ortonaphthoquinone diazides (2 µm thick) is applied to the plate prepared in this way.
Table 3. Assortment and properties of "Agfa Ozasol" plates. Positive pre-sensitized monometallic plates for sheet and roll printing
|
Density, thousand prints |
||||
|
Standard plates for medium to large runs. Treated with electrochemical graining from NMOd. Recommended for printing with the stochastic screening method "Agfa Cristal-Raster" |
||||
|
For test printing with low circulation rates For medium and short run printing on small format sheet-fed presses. Electromechanically grained from HNO |
||||
|
For small and medium editions |
||||
|
For small and large editions. Electromechanical grained HCL; require short exposure time |
||||
|
For large and medium editions. Electrochemically grained HCL |
||||
|
Versatile Positive-Negative Plates for Large and Medium Runs |
||||
|
For large editions. Double-grained for maximum resolution. Recommended for printing with the stochastic screening method "Agfa CristalRasten" |
||||
|
For very large runs (over 200 thousand) with special surface treatment |
Negative pre-sensitized mono plates for sheet and roll printing
|
Print run, thousand prints |
|||
|
For large editions. Electromechanical grained with HNO. Designed for printing packages, newspapers, continuous forms |
|||
|
Electromechanical grained HNO double-sided inserts. Recommended for printing books |
|||
|
Double-grained inserts for maximum run life. Recommended for newspaper printing |
|||
|
For medium and large runs of any product Treated with electromechanical grain from HC1 |
|||
|
Plates for projection exposure with a permanent photopolymer layer. Treated with electromechanical graining and HCl. Recommended for printing books and posters |
|||
|
For laser recorders. Electromechanical grained and HCl treated |
|||
|
For laser recorders (improved version of N90 High speed) |
Table 4. Main technical parameters of P5S plates
The sensitization of the plate is carried out under the control of a special system that monitors the uniform application, distribution and drying of the copy layer. In this method, the same coating thickness is ensured on the entire surface of the plate, including along the edges.
A copy layer based on water-insoluble film-forming resins with a diazo compound as a photosensitive component also contains special abrasive micropigments (dispersion of particles 3 ... 4 microns). Protruding above the surface, micropigments create favorable conditions for quickly reaching vacuum in copy frames and provide excellent contact between the transparency and the photosensitive layer during exposure. This prevents the occurrence of "blank copies" (that is, partial absence of an image in different places on the printing plate due to poor adherence of the photographic plate to the copy layer). Finished plates are cut into standard formats (over 300 sizes of Ozasol P5S plates are offered for sheet machines and over 1000 for roll-fed machines from 225x370 and 224x387 mm to 1490x1980 and 1158x1689 mm, respectively). High cutting precision (± 0.8 mm per 1 m length) and smooth edges ensure ease of use and prevent damage to the cylinders and rollers of printing machines. Before packing, the plates are checked with a laser beam for defects in the copy layer. The plates are packed in paper or plastic (depending on the size) and made up in cardboard or wooden boxes. In this damage-proof package, Ozasol printing plates are delivered to printers around the world.
After exposure and development, the copy layer can act as a printing element. It has a green-blue color, and during exposure, due to the decomposition of the photosensitive component, it acquires a blue color. This creates the maximum color contrast between printed and intermediate elements, which facilitates quality control of the copy.
The high roughness index ensures tight contact between the plate and the plate during copying and facilitates the printing process due to the mechanical content of the dampening film. Plates for web presses, which operate at high speeds, have a more developed surface. A significant degree of wetting is also required for the stability of the properties of the plate and the printing plate under conditions of temperature fluctuations. environment... In addition, the graininess indirectly affects the resolution. Electrochemical graining in nitric acid provides a more regular rough surface.
The indices of the resolution and excretion abilities determine the level of reproduction of small, including raster, elements, sufficient for the production of high-quality products. A significant level of light sensitivity determines the short exposure time of the plates (from 40 s to 2 min). Shorter exposure times result in fewer specks on the plate and accurate reproduction of medium to deep tones. The development process is characterized by high selectivity, which ensures that minimal printing elements are retained after the copy has been developed. This creates a rich color gamut on the print.
During the processing of the exposed P5S plate, it is recommended to use the branded chemicals "Agfa Ozasol" - a developer, a regenerator for it, a gum solution, a cleaning emulsion, a protective solution for heat treatment. This will certainly ensure the reliability of using the plate in printing machines, high and stable product quality.
A slightly alkaline aqueous developer solution, which is used for Agfa Ozasol plates, is consumed economically during processing and, in addition, is subject to the action of a regenerating compound. The low cost and non-aggressiveness of the developer ensure an almost environmentally friendly processing.
Heat treatment is used to increase the circulation life of printing plates up to 500 thousand prints. This operation is also recommended if printing is carried out using UV drying inks. Manufacturing of printing plates based on Agfa Ozasol materials is environmentally friendly, does not require strict adherence to temperature and humidity regimes, ensures high productivity of the technological process and guarantees good results.
Howson-Algraphy, together with Du Pont, has developed a technology for the production of new Stiveriith offset printing plates. Instead of the traditional light-sensitive layer, a special light-sensitive silver-retaining layer is applied to the plate. The printed image is acquired by exposing the forms with the help of a laser, which is controlled by a computer. The advantage in this case is the complete elimination of the process of making photoforms, higher resolution of the forms, and reducing the time for making printing plates up to 3 minutes. The company manufactures equipment for processing these plates. The process of processing them takes 90 seconds.
Howson-Algraphy has created a new automatic line for the production of offset plates designed for the production of negative and positive forms of all types, including those with sensitivity to laser radiation and processed using electrostatic technologies. The line is used to make Super-Spartan plates that produce fine grain images with high screening lines. Line dimensions - 70x6x6 m. Replacement of rolls of aluminum tape is automatic.
New offset printing plates "Proft-Print SD", developed in 2004 by "Eskafot Gmb" (Germany), which are distinguished by high sensitivity, minimum exposure times and high resolution, have a thickness of 0.2 mm. SD forms can be used with almost all offset inks for flat and roll printing, their circulation is 10 thousand prints. Polyester-based SD molding material can be supplied in rolls up to 61 m in length in various widths.
Form plates "Plazer" are intended for direct production of FOPPs on laser printers. Compared with other pre-sensitized offset metal plates, these plates make it possible to exclude photographic film, chemicals for its processing, copying equipment from the technological process of manufacturing printing plates, and to increase the efficiency of manufacturing forms. The maximum circulation of prints from one printing plate is 15,000 copies.
At the request of the customer, when supplying Plazer plates, a tray can be added for inserting plates into the printer and a perforator for securing plates in POL-35 and Romajor printing machines.
Printing Developments Inge manufactures bimetallic plates in which a copper layer is electroplated onto an aluminum plate. This layer replaces the traditional polymer coating. The image that is reproduced by the copper plating can be adjusted to compensate for the enlargement of the bitmap during printing. When using a bimetallic mold, significantly less dampening solution is required than when using conventional molds. This makes it easier to control the water-paint balance.
The joint Ukrainian-Bulgarian venture "SKS-Ukraine" is the official distributor of the company "POLYCHROME-POAR", which produces pre-sensitized aluminum offset plates PP-1. These plates are successfully used today at many enterprises in Ukraine. Plates of the PP-1 type are intended for the production of high-quality offset forms by the method of positive copying for sheet-fed and roll-fed machines. The technical characteristics of the plates are as follows:
Circulation life of plates, thousand prints:
raw 100 ... 150
after burning out 300
Plate thickness, mm 0.3; 0.15
Storage temperature of plates, ° С 5 ... 20
Developer temperature during plate development, "С 18 ... 23
Developer costs for processing plates during development, l / m2:
manual 0.3
machine 0.2
Shelf life of plates and chemicals, 1 year
V last years In Ukraine, aluminum plates (electrically ground, anodized, pre-sensitized, both positive and negative) with the corresponding chemical products and equipment for the processing of offset printing plates of the world famous company Lastra (Italy) are gaining popularity. This company produces FUTURA ORO positive plates and NITIO DEV negative plates.
Plates "FUTURA ORO" have a circulation resistance under normal conditions of over 250 thousand prints, and after heat hardening - over 400 thousand prints. These plates allow you to print with a minimum of water, ensuring high fidelity and sharpness of the image, as well as ink saturation.
"NITIO DEV" - these are new negative plates, which, starting from September 2007 p., Are produced instead of the “NITIO SAN” plates and have a number of significant advantages compared to them, as evidenced by the following data:
"NITIO SAN" "NITIO DEV"
Color green olive blue-green
Roughness R μm 0.51 ... 0.55 0.55 ... 0.6 Mass of the photosensitive layer, g / m2 0.9 0.9
Mass of anodized layer, g / m2 2 ... 2.2 2.5 ... 2.7 Exposure time, s "90 55
According to their technical characteristics, "NITIO DEV" are pre-sensitized negative plates, which are especially recommended for printing newspapers in mass circulation. They can be used for scanning in print control and programming systems, since they have a fairly high image contrast in comparison with the light and shiny tone of the electrograin surface.
Based on the above, it can be noted that the first simplest solution is the creation of new equipment using traditional printing materials, if the image on the form is obtained using a powerful laser. In this case, you can use any photosensitive plate of negative or positive copying method, but you need special exposure equipment, for example, the Plate Setter Aurora by OPTRONICS, which uses a 400 mW ytrium-aluminum-garnet (YAG) laser. For comparison, it should be noted that laser exposure of supersensitive materials requires lasers with a power of 0.2 ... 30 mW.
The second direction in the development of computer-to-plate laser technologies is the creation of new super-light-sensitive materials. These are plates with photothermal hardening, silver-containing and photoconducting layers.
An example of laser imaging in photothermally hardened layers are technologies using the photopolymerization process with further heat treatment of Ozasol N90 aluminum-based plates from Hoechst-Kalle, Electra plates from Horsell-Aniter, Thermal Infrared plates from Kodak ".
The second group of super light-sensitive materials is multilayer aluminum-based plate with silver-containing layers. This technology uses the principle of forming an image in a layer, which, after developing and fixing, will play the role of a mask for further exposure and processing of positive or negative copy layers (Polychrome CTX plates from Polychrome, FNH plates from Fuji Foto Film) , or the principle of diffusion of a complex compound to a silver halide in unexposed areas. After the restoration of connections to metallic silver, these areas serve as printed elements ("silver-printed" elements). These are Ozasol P80 and P90 plates from Hoechst-Kalle, Silverlith SDB plates from DuPont-Howson, Lithostar plates from Agfa.
Similar works are carried out by the mentioned companies for the production of plates on inexpensive substrates such as synthetic film and paper. Mitsubisi has developed a plate material with silver-containing photodiffuse layers “Silver Digiplate SDP”. Materials of this company are classified according to the type of substrate. For example, SDP-F materials are produced on a polyester basis, and SDP-R on paper. In addition, the material grade contains a conventional designation of the laser used to expose the forms (AR - argon, HN - helium-neon, LD - infrared and YAG - ytrium-aluminum-garnet lasers). This group should include 3M Onyx plates on a polyester base, the cost of which is only 70% of the cost of conventional forms, as well as Agfa's Setprint material.
Plates for laser exposure, where the principle of electrography and photoconductive photosensitive layers are applied, provide, unfortunately, a low quality of forms. Photoconductive layers based on inorganic compounds (CdS, Zn) are inferior in image quality to photoconductive layers based on organic compounds. An example of materials with light-sensitive organic compounds are OPC-D plates from Poluchrome on an aluminum base using rare toner in the development process, which are exposed in the OPC 2500 system, Laserite plates from Hoechst-Kalle. The Fuji Film Company has developed a technology for the production of forms by the electrographic method "Electrophotographic Direct Plate Making System" (ELP) on a paper basis, the company "ZM" has created the material HSP, in the systems of direct exposure they use the material "Tesso Direct Image Paper Plates", where the development carried out with dry toner, and "Tesso Master Polyester", respectively, on paper and polyester bases.
Creation of new ultra-light-sensitive plate materials does not eliminate the need to improve equipment for laser exposure of plates. Currently, there are more than 30 suppliers of equipment for these purposes. For ultra-sensitive mold materials, the systems Creo 3244, Gutenberg by Linotype-Hell, Plate-Rite PL-R 1008 by Screen, Do Plate 800 by Scitex, UP-1000 have been developed. the firm "POLYCHROME"; for Ozasol N90 plates from Hoechst - Raystap device from Scitex. For the Digiplate plates of Mitsubisi the following has been created: a special Panther Plate 34 / P system by Prelress Solutions (Varityper), the resolution of which is 1200 dots / cm, the information is displayed on an A3 format form in 2 minutes; apparatus "Escofot DXF" (Multigraphics Quick Set SL) from "Eskofot", recording in 52x52 cm format - in 3 minutes; automatic machines "AM Multi SP", 65TPM, EP 988; line "Extrema Laser", automated computer system "Laser Xposer" by "Danish Hope Computer Corporation", laser machine for recording information on a plate by "Surpess", etc.
Other technologies, where the image is obtained not in light-sensitive layers, but by printing it with a laser printer on a plate material on a paper basis "Plate Maker" by "XANTE", "Tecco" on a synthetic basis by "Kimoto" or "Autotype", give significantly lower quality of forms. The same quality can be achieved using computer-controlled ink spraying, which will act as a mask in the further production of the Lastra mold, where the inkjet printer is connected to the Extrema Ink Jet line or to the Polychrome Toray Waterless Plate ... It is also possible to use thermosensitive layers for this in Plate Setters manufactured by MAN ROLAND, where the images from the ink ribbon are transferred to the hydrophilic surface of the printing cylinder by a laser beam due to heat. At the same time, the time for making a mold of A3 format takes 8.5 minutes. This principle is used in Laser-Mask films and Polaroid plates.
The choice of the type of plate and technology depends on the quality of the form, format and circulation that must be provided. Of course, the strength of the base and its deformation significantly affect the durability of the form, as well as the quality.
To increase the circulation life and dimensional stability, paper is additionally laminated with plastic wrap or aluminum. For forms on a synthetic polyester base, this can be achieved by increasing its thickness. For example, with a base thickness of 0.12 mm, forms withstand a circulation of 10 thousand prints, and with a thickness of 0.2 mm - 25 thousand prints.
Form materials on polyester and paper backing are used for printing small-format products of low and medium quality. For printing high-quality color illustrated editions of medium and large formats, computer output of information on plate materials with an aluminum base should be used, where the image is formed using supersensitive layers.
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