photopolymer printing plate, form letterpress, the printing elements of which are obtained as a result of the action of light on a polymer composition (the so-called photopolymer composition - FPC). These compositions are solid or liquid (fluid) polymer materials, which, under the influence of an intense light source, become insoluble in their usual solvents, liquid FPCs pass into a solid state, and solid ones additionally polymerize. In addition to the polymer (polyamide, polyacrylate, cellulose ether, polyurethane, etc.), FPC contains a small amount of a photoinitiator (for example, benzoin). F. p. f. from solid compositions first appeared in the late 50s. 20th century in the USA, and a few years later in Japan F. p. f. from liquid compositions.

For the manufacture of F. p. f. from solid FPC, thin aluminum or steel sheets are used with a layer of FPC applied to them with a thickness of 0.4–0.5 mm. The process of obtaining F. p. f. consists of exposing the negative, washing out the non-polymerized layer in the blank areas and drying the finished form.

For the manufacture of F. p. f. From liquid FPC, a negative is placed in a special device (for example, a cuvette made of transparent colorless glass), covered with a transparent thin colorless film, and FPC is poured. After that, exposure is made on both sides, as a result of which polymerized (solid) printing elements are formed on the negative side, and a form substrate on the opposite side. Then, the non-polymerized composition is washed out with a solvent jet from the blank elements and dried. finished form.

F. p. f. (often referred to as full-size flexible forms) are used for printing magazines and books, including those with color illustrations. They are easy to manufacture, have a small weight, high circulation stability (up to 1 million prints), allow the wide use of phototypesetting and do not require much time for preparatory operations when printing a run.

Lit.: Sinyakov N. I., Technology for the manufacture of photomechanical printing plates, 2nd ed., M., 1974.

N. N. Polyansky.

Polymer molds

This means that some kind of polymer reacts to light. There are 2 types of polymers: either they "crosslink", i.e. polymerize or solidify under the influence of light, or vice versa - they become soluble. This is what the whole technology of production of printing forms is built on.

The scope of photopolymer printing plates is any printed matter.

Application advantages:

– good registration (since the accuracy of ink application, which determines the quality of prints of a color image)

– reproduction of images with lineature up to 120 l/cm (high lineature) is possible

– simple production of printing forms

– high circulation resistance

– repeated use

Flaws:

– unstable to some components of printing inks (printing inks, if not in accordance with the requirements, can corrode the printing plate)

General requirements for flexo printing plates

1) Uniformity of the printing surface with good ink acceptance and ink release

2) Small deviations in plate thickness (plate thickness uniformity)

3) High circulation resistance

Classification of Photopolymer Printing Plates(only 2 varieties)

1. Hard polymer, so-called. TPFM (hard polymer photographic materials)

2. Liquid polymer forms - ZhFPM

Solid polymer molds are single-layer and multi-layer

Hardness, surface, information properties.

The structure of hard polymer printing plates,

single layer consists of 4 layers:

– protective film

- anti-adhesion layer (i.e., it comes off together with the protective film, does not allow it to stick strongly to?)

- photopolymer layer

– film-substrate

multilayer:

- protective film

- anti-adhesion layer

- photopolymer layer

- stabilizer film

- substrate layer

- anti-adhesion layer

- protective film

The photopolymer strongly interacts with oxygen (loses its photosensitive properties, hardens in air, etc.), so there is a film on both sides.

The substrate is needed so that during the manufacture a thin layer of a photopolymer is poured onto it, which hardens. Then the whole thing is still cut into pieces we need.

Single layer plate. This photopolymer under the influence of UV hardens let it (polymerization occurs). If we put a photoform on top and put the whole thing under ultraviolet light, then roughly speaking, molecular bonds will be destroyed under the transparent areas of the photoform, which are then very easily removed (by washing, blowing with air, mechanically with brushes - it doesn’t matter). We still have printing elements, and the whitespace element has such properties that it can be easily removed.

The composition of the photopolymerizing layer includes monomers (i.e. what is a "polymer" - roughly - a very long molecule), photoinitiators (a substance that is the source of a further chain reaction, i.e. a substance, when it receives a dose of UV, starts the reaction - it changes itself and causes the surrounding molecules to change as well), elastomeric binder, stabilizers and additives.

The polymer itself is not photosensitive (it doesn’t care what kind of light shines on it), but the photoinitiator doesn’t care, and when ultraviolet is shined on the photoinitiator, it changes itself and causes nearby polymer molecules to also change (the domino principle - it itself fell and others fell down) .

Production process: a roll with a film-substrate is unwound, a polymer is poured onto it in a uniform layer, a protective film is placed on top so that there is no exposure to oxygen. Further it is cut on the necessary format.

), the printing elements of which are obtained as a result of the action of light on a polymer composition (the so-called photopolymer composition - FPC). These compositions are solid or liquid (fluid) polymeric materials, which, under the influence of an intense light source, become insoluble in their usual solvents, liquid FPCs turn into a solid state, and solid ones additionally polymerize. In addition to the polymer (polyamide, polyacrylate, cellulose ether, polyurethane, etc.), FPC contains a small amount of a photoinitiator (for example, benzoin). F. p. f. from solid compositions first appeared in the late 50s. 20th century in the USA, and a few years later in Japan F. p. f. from liquid compositions.

For the manufacture of F. p. f. from solid FPC, thin aluminum or steel sheets are used with a layer of FPC applied to them with a thickness of 0.4–0.5 mm. The process of obtaining F. p. f. consists of exposing the negative, washing out the non-polymerized layer in the blank areas and drying the finished form.

For the manufacture of F. p. f. From liquid FPC, a negative is placed in a special device (for example, a cuvette made of transparent colorless glass), covered with a transparent thin colorless film, and FPC is poured. After that, exposure is made on both sides, as a result of which polymerized (solid) printing elements are formed on the negative side, and a form substrate on the opposite side. Then, the non-polymerized composition is washed out with a solvent jet from the blank elements and the finished form is dried.

F. p. f. (often referred to as full-size flexible forms) are used for printing magazines and books, including those with color illustrations. They are easy to manufacture, have a small weight, high circulation stability (up to 1 million prints), allow the wide use of phototypesetting and do not require much time for preparatory operations when printing a run.

Lit.: Sinyakov N. I., Technology for the manufacture of photomechanical printing plates, 2nd ed., M., 1974.

N. N. Polyansky.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Photopolymer printing plate" is in other dictionaries:

photopolymer printing plate- Embossed printing plate made on the basis of photopolymerizable materials. Printing topics...

Photopolymer printing plate- oven a form of letterpress made from a photopolymer of a high molecular weight organic substance that has high resolution light sensitivity and is suitable for negative copying onto it. After exposure and washing out the dissolution of the special ... ... Publishing Dictionary

photopolymer printing plate- Embossed printing plate made on the basis of photopolymerizable materials…

The carrier is textual and will depict. information, which serves for repeated receipt of impressions; contains printing (giving prints of ink on the printed material) and blank (non-printing) elements. The mutual arrangement of printing and space ... Big encyclopedic polytechnic dictionary

Photo- - (Greek - light painting) a set of methods for obtaining time-stable images of objects and optical signals on photosensitive layers (SChS) by fixing photochemical or photophysical changes that occur in the SChS under ... ... Encyclopedic Dictionary of Media

- (from Zinc and ... graphics) the photomechanical process of making Cliches (illustrative forms of letterpress printing) by photographically transferring the image to a zinc or other plate, the surface of which is then subjected to acid etching in ... Great Soviet Encyclopedia

Flexographic printing (flexography, flexo printing) is a letterpress printing method using flexible rubber forms and quick-drying liquid paints. The term "flexography" was based on the Latin word flexibilis, which means ... ... Wikipedia

forme cylinder- One of the cylinders of the printing apparatus of a rotary printing (sheet or roll) machine, on which the printing form is fixed - offset, photopolymer, stereotype, etc. printing machines rotogravure printing blank and printing ... ... Brief explanatory dictionary of polygraphy

forme cylinder- One of the cylinders of the printing apparatus of a rotary printing (sheet or roll) machine, on which the printing form is fixed offset, photopolymer, stereotype, etc. In gravure rotary printing machines, blank and printing ... ... Technical Translator's Handbook

We display forms for flexographic printing

Dr. tech. sciences, prof. MGUP im. Ivan Fedorov

A type of letterpress that is widely used for printing labels and packaging products from paper, foil, plastic films, as well as for printing newspapers, is flexography. Flexographic printing is carried out with elastic rubber or highly elastic photopolymer printing plates with fluid fast-setting inks.


In the printing apparatus of a flexographic printing machine, rather liquid ink is applied to a printing plate fixed on a plate cylinder, not directly, but through an intermediate rolling (anilox) roller. The knurling roller is made of steel pipe, which can be coated with a layer of copper. A raster grid is applied to this surface by etching or engraving, the deep cells of which are made in the form of pyramids with a sharp top. The raster surface of the anilox roller is usually chrome-plated. The transfer of ink from the ink box to the printing plate is carried out by a rubber (ductor) roller to the anilox roller, and from it to the printing elements of the form.

The use of resilient printing plates and low-viscosity fast setting inks allows for high speed print almost any roll material, reproduce not only line elements, but also single- and multi-color images (with a screening lineature of up to 60 lines/cm). Slight typing pressure ensures b O Greater circulation stability of printed forms.

Flexography is a direct printing method in which ink is transferred from a plate directly onto the printed material. In this regard, the image on the printing elements of the form must be mirrored in relation to the readable image on paper (Fig. 1).

In modern flexographic printing, photopolymer printing plates (FPF) are used, which are not inferior to offset ones in terms of printing and technical and reproduction and graphic properties, and, as a rule, surpass them in run resistance.

Solid or liquid photopolymerizable compositions are used as photopolymer materials. These include solid or liquid monomeric, oligomeric or monomeric-polymer mixtures capable of changing the chemical and physical state under the action of light. These changes lead to the formation of solid or elastic insoluble polymers.

Solid photopolymerizable compositions (SFPs) retain a solid state of aggregation before and after the production of a printing plate. They are delivered to the printing company in the form of photopolymerizable shaped plates of a certain format.

The structure of photopolymerizable plates for flexographic printing is shown in fig. 2.

Liquid photopolymerizable compositions (LFP) are supplied to printing companies in containers in liquid form, or they are made directly at the enterprises by mixing the initial components.

The main technological operation in the manufacture of any FPF, during which the photopolymerization reaction occurs in the photopolymerizable composition and a latent relief image is formed, is exposure (Fig. 3 A) of the photopolymerizable layer. Photopolymerization occurs only in those parts of the layer that are exposed to UV rays and only during their exposure. Therefore, negative photoforms and their analogues in the form of a mask layer are used for exposure.

Rice. Fig. 3. Technological operations for obtaining photopolymer printing plates on solid photopolymerizable plates: a - exposure; b - washing out of gaps; c - drying of the printing plate; d - additional exposure of printing elements

The development of a relief image, as a result of which non-polymerized areas of the photopolymerizable plate are removed, is carried out by washing them out with an alcohol, alkaline solution (Fig. 3 b) or water depending on the type of plates, and for some types of plates - dry heat treatment.

In the first case, the exposed photopolymerizable plate is processed in the so-called solvent processor. As a result of the washout operation (see Fig. 3 b) of non-polymerized sections of the plate, a relief image is formed on the form with a solution. Washout is based on the fact that in the process of photopolymerization, the printing elements lose their ability to dissolve in the wash solution. Drying required after washing photopolymer forms. In the second case, processing is carried out in a thermal processor for processing photopolymer forms. Dry heat treatment completely eliminates the use of traditional chemicals and wash solutions, reduces the time of obtaining molds by 70%, since it does not require drying.

After drying (Fig. 3 V) the photopolymer form is subjected to additional exposure (Fig. 3 G), which increases the degree of photopolymerization of printing elements.

After additional exposure, photopolymer plates based on TFP for flexo printing have a shiny and slightly sticky surface. The stickiness of the surface is eliminated by additional processing (finishing), as a result, the form acquires the properties of stability and resistance to various solvents of printing inks.

Finishing can be done chemically (using chloride and bromine) or by exposure to ultraviolet light in the range of 250-260 nm, which has the same effect on the form. With chemical finishing, the surface becomes matte, with ultraviolet - shiny.

One of the most important parameters photopolymer printing forms is the profile of the printing elements, which is determined by the angle at the base of the printing element and its steepness. The profile determines the resolution of photopolymer printing plates, as well as the adhesion strength of the printing elements to the substrate, which affects the runtime. The profile of the printing elements is significantly affected by the exposure modes and the conditions for washing out white space elements. Depending on the exposure mode, the print elements may have a different shape.

With overexposure, a flat profile of the printing elements is formed, which ensures their reliable fixation on the substrate, but is undesirable due to the possible decrease in the depth of gaps.

With insufficient exposure, a mushroom-shaped (barrel-shaped) profile is formed, leading to instability of the printing elements on the substrate, up to the possible loss of individual elements.

The optimal profile has an angle at the base of 70 ± 5º, which is the most preferable, as it ensures reliable adhesion of the printing elements to the substrate and high image resolution.

The profile of printing elements is also influenced by the ratio of exposures of preliminary and main exposure, the duration of which and their ratio are selected for different types and batches of photopolymer plates for specific exposure installations.

Currently, for the manufacture of photopolymer printing plates for flexographic printing, two technologies are used: “computer-photoform” and “computer-printing plate”.

So-called analog plates are produced for the “computer-printing plate” technology, and digital plates for the “computer-printing plate” technology.

In the manufacture of photopolymer forms of flexographic printing based on TFPK (Fig. 4), the following main operations are performed:

• preliminary exposure of the reverse side of the photopolymerizable flexographic plate (analogue) in the exposure unit;
• the main exposure of mounting the photoform (negative) and the photopolymerizable plate in the exposure unit;
• processing of a photopolymer (flexographic) copy in a solvent (washout) or thermal (dry heat treatment) processor;
• drying photo polymer form(solvent-washout) in a drying device;
• additional exposure of the photopolymer form in the exposure unit;
• additional processing (finishing) of the photopolymer form to eliminate the stickiness of its surface.

Rice. Fig. 4. Scheme of the process of manufacturing photopolymer molds based on TPPC using the “computer-photoform” technology

Exposing the reverse side of the plate is the first step in the manufacture of the form. It represents an even illumination of the reverse side of the plate through a polyester base without the use of vacuum and negative. This is an important technological operation that increases the photosensitivity of the polymer and forms the base of the relief of the required height. Correct exposure of the reverse side of the plate does not affect the printing elements.

The main exposure of the photopolymerizable plate is carried out by contact copying from a negative photoform. On a photoform intended for making molds, the text must be mirrored.

Photoforms must be made on a single sheet of film, since composite montages glued with adhesive tape, as a rule, do not provide a reliable fit of the photoform to the surface of the photopolymerizable layers and can cause distortion of the printing elements.

Before exposure, the photoform is applied to the photopolymerizable plate with the emulsion layer down. Otherwise, a gap equal to the thickness of the base of the film is formed between the plate and the image on the photoform. As a result of the refraction of light in the basis of the film, a strong distortion of the printing elements and copying of the raster areas can occur.

To ensure close contact of the photoform with the photopolymerizable material, the film is matted. Microroughnesses on the surface of the photoform allow you to completely quickly remove air from under it, which creates a tight contact between the photoform and the surface of the photopolymerizable plate. For this, special powders are used, which are applied with a cotton-gauze swab with light circular movements.

As a result of the processing of photopolymer copies based on solvent washout plates, the monomer that has not been exposed and polymerized is washed out - it dissolves and is washed off from the plate. Only areas that have undergone polymerization and form a relief image remain.

Insufficient washout time, low temperature, improper brush pressure (low pressure - bristles do not touch the surface of the plate; high pressure - bristles bend, washout time is reduced), low solution level in the wash tank leads to too fine relief.

Excessive washout time, high temperature and insufficient solution concentration lead to too deep relief. The correct washout time is determined experimentally depending on the thickness of the plate.

When washing out, the plate is impregnated with a solution. The polymerized image relief swells and softens. After removing the wash solution from the surface with non-woven napkins or a special towel, the plate must be dried in the drying section at a temperature not exceeding 60 °C. At temperatures above 60 °C, registration difficulties may occur, since the polyester base, which at normal conditions maintains stable dimensions, begins to shrink.

Swelling of the plates during washing leads to an increase in the thickness of the plates, which, even after drying in the dryer, do not immediately return to their normal thickness and must be left for another 12 hours in the open air.

When using heat-sensitive photopolymerizable plates, the manifestation of the relief image occurs by melting the non-polymerized sections of the forms during their processing in a thermal processor. The molten photopolymerizable composition is adsorbed, absorbed and removed with a special cloth, which is then sent for disposal. Such a technological process does not require the use of solvents, and therefore, drying of the developed forms is excluded. In this way, both analog and digital forms can be produced. The main advantage of the technology with the use of heat-sensitive plates is a significant reduction in mold manufacturing time, which is due to the absence of a drying stage.

To give durability, the plate is placed in an exposure unit for additional illumination with UV lamps for 4-8 minutes.

To eliminate the stickiness of the plate after drying, it must be treated with UV radiation with a wavelength of 250-260 nm or chemically.

Analog solvent-washout and heat-sensitive photopolymerizable flexographic plates have a resolution that provides 2-95 percent dots at a screen lineature of 150 lpi, and a print run of up to 1 million prints.

One of the features of the process of manufacturing flat photopolymer forms of flexographic printing using the “computer-photoform” technology is the need to take into account the degree of stretching of the form along the circumference of the plate cylinder when it is installed in printing machine. The stretching of the mold surface relief (Fig. 5) leads to an elongation of the image on the print compared to the image on the photoform. In this case, the thicker the stretchable layer located on the substrate or stabilizing film (when using multilayer plates), the longer the image.

The thickness of photopolymer forms varies from 0.2 to 7 mm and above. In this regard, it is necessary to compensate for elongation by reducing the image scale on the photoform along one of its sides, oriented in the direction of movement of the paper web (tape) in the printing machine.

To calculate the scale value M photoforms, you can use the stretching constant k, which for each type of plates is equal to k = 2 hc (hc is the thickness of the relief layer).

Print length Lott corresponds to the distance that a certain point on the surface of the mold travels during a complete revolution of the forme cylinder, and is calculated as follows:

Where Dfts— diameter of the plate cylinder, mm; hf— thickness of the printing plate, mm; hl— adhesive tape thickness, mm.

Based on the calculated impression length, the necessary shortening of the photoform Δ is determined d(in percent) according to the formula

.

So, the image on the photoform in one of the directions should be obtained with a scale equal to

.

Such scaling of the image on the photoform can be performed by computer processing of a digital file containing information about the imposition or individual pages of the publication.

The production of photopolymer flexographic printing plates using the “computer-printing plate” technology is based on the use of laser methods processing of form materials: ablation (destruction and removal) of the mask layer from the surface of the form plate and direct engraving of the form material.

Rice. Fig. 5. Stretching of the surface of the printing plate when installed on the plate cylinder: a - printing plate; b - printing plate on a plate cylinder

In the case of laser ablation, the subsequent removal of the non-polymerized layer can be performed using a solvent or thermal processor. For this method special (digital) plates are used, which differ from traditional ones only in the presence of a mask layer 3-5 microns thick on the surface of the plate. The mask layer is a soot filler in an oligomer solution that is insensitive to UV radiation and thermally sensitive to the infrared range of the spectrum. This layer is used to create the primary image formed by the laser and is a negative mask.

The negative image (mask) is necessary for the subsequent exposure of the shaped photopolymerizable plate with a UV light source. As a result of further chemical processing, a relief image of the printing elements is created on the surface.

On fig. 6 shows the sequence of operations for manufacturing a flexographic plate on a plate containing a mask layer 1 , photopolymer layer 2 and substrate 3 . After laser removal of the mask layer in places corresponding to the printing elements, a transparent substrate is exposed to create a photopolymer substrate. Exposure to obtain a relief image is carried out through a negative image created from the mask layer. Then the usual processing is carried out, consisting of washing out the unpolymerized photopolymer, washing, post-exposure with simultaneous drying and light finishing.

When recording an image using laser systems, the dot size on masked photopolymers is, as a rule, 15–25 μm, which makes it possible to obtain images with a lineature of 180 lpi and higher on the form.

In the manufacture of photopolymer forms in the "computer-printing form" technology, plates are used based on solid photopolymer compositions that provide high quality printing plates, further processing of which occurs in the same way as analog flexographic photopolymer forms.

On fig. 7 shows the classification of photopolymerizable plates for flexographic printing based on solid photopolymer compositions.

Depending on the structure of the plate, single-layer and multi-layer plates are distinguished.

Single-layer plates consist of a photopolymerizable (relief-forming) layer, which is located between the protective foil and the lavsan base, which serves to stabilize the plate.

Multi-layer plates designed for high-quality raster printing consist of relatively hard thin-layer plates with a compressible substrate. On both surfaces of the plate there is a protective foil, and between the photopolymerizable layer and the base there is a stabilizing layer, which ensures almost complete absence of longitudinal deformation when the printing plate is bent.

Depending on the thickness, photopolymerizable plates are divided into thick-layer and thin-layer ones.

Thin-layer plates (thickness 0.76-2.84 mm) have high hardness in order to reduce dot gain during printing. Therefore, printing plates made on such plates provide high quality finished products and are used to seal flexible packaging, plastic bags, labels and tags.

Thick-layer plates (thickness 2.84-6.35 mm) are softer than thin-layer ones and provide tighter contact with an uneven printed surface. Printing forms based on them are used for sealing corrugated cardboard and paper bags.

IN Lately when printing on materials such as corrugated cardboard, plates with a thickness of 2.84-3.94 mm are more often used. This is explained by the fact that when using thicker photopolymer forms (3.94-6.35 mm) it is difficult to obtain a high-line multicolor image.

Depending on the hardness, plates of high, medium and low hardness are distinguished.

Plates of high hardness are characterized by less dot gain of raster elements and are used for printing high-line works. Plates of medium rigidity allow you to print raster, line and solid works equally well. Softer photopolymerizable plates are used for ink printing.

Depending on the method of processing photopolymer copies, plates can be divided into three types: water-soluble, alcohol-soluble, and plates processed using thermal technology. For machining inserts belonging to different types, it is necessary to use different processors.

The method of laser ablation of the mask layer of photopolymerizable plate materials produces both flat and cylindrical printing plates.

Cylindrical (sleeve) flexographic forms can be tubular, put on a plate cylinder from its end, or represent the surface of a removable plate cylinder installed in a printing machine.

The process of manufacturing flat flexographic printing plates based on solvent washout or heat-sensitive digital photopolymerizable plates with a mask layer using the “computer-printing plate” technology (Fig. 8) includes the following operations:

• preliminary exposure of the reverse side of the photopolymerizable flexographic plate (digital) in the exposure unit;
• transferring a digital file containing data on color separation images of stripes or a full-size printed sheet to a raster processor (RIP);
• digital file processing in RIP (reception, interpretation of data, rasterization of the image with a given lineature and raster type);
• writing the image on the mask layer of the plate by ablation in the forming device;
• main exposure of the photopolymerizable layer of the plate through the mask layer in the exposure unit;
• processing (washing out for solvent-washable or dry heat treatment for heat-sensitive plates) of a flexographic copy in a processor (solvent or thermal);
• drying of the photopolymer form (for solvent-washable plates) in a drying device;
• additional processing of the photopolymer form (light finishing);
• additional exposure of the photopolymer form in the exposure unit.

The process of manufacturing sleeve photopolymer flexo printing plates by the ablation method (Fig. 9) differs from the process of manufacturing flat plates mainly in the absence of the operation of preliminary exposure of the reverse side of the plate material.

The use of the mask layer ablation method in the manufacture of photopolymer flexo plates not only shortens the technological cycle due to the lack of photo plates, but also eliminates the causes of quality degradation that are directly related to the use of negatives in the production of traditional printing plates:

• there are no problems arising due to loose pressing of photoforms in a vacuum chamber and the formation of bubbles during exposure of photopolymer plates;
• there is no loss in the quality of forms due to dust or other inclusions;
• there is no distortion of the shape of the printing elements due to the low optical density of photoforms and the so-called soft point;
• no need to work with vacuum;
• the profile of the printing element is optimal for dot gain stabilization and accurate color reproduction.

When exposing a montage consisting of a photoform and a photopolymer plate, in traditional technology, the light passes through several layers before reaching the photopolymer: silver emulsion, frosted layer and film base, and glass of a vacuum copy frame. In this case, the light is scattered in each layer and at the boundaries of the layers. As a result, the halftone dots have wider bases, resulting in increased dot gain. In contrast, when laser-exposing masked flexographic plates, there is no need to create a vacuum and there is no film. The near-total absence of light scatter means that the high-resolution image on the layer mask is faithfully reproduced on the photopolymer.

In the manufacture of flexographic forms according to digital technology ablation of the mask layer, it must be borne in mind that the formed printing elements, in contrast to exposure through a photoform in traditional (analogue) technology, are somewhat smaller in area than their image on the mask. This is explained by the fact that the exposure takes place in an air environment and, due to the contact of the FPS with atmospheric oxygen, the polymerization process is inhibited (delayed), causing a decrease in the size of the forming printing elements (Fig. 10).

Rice. Fig. 10. Comparison of printing elements of photopolymer forms: a — analog; b - digital

The result of exposure to oxygen is not only a slight decrease in the size of the printing elements, which affects small raster dots to a greater extent, but also a decrease in their height relative to the height of the plate. In this case, the smaller the raster dot, the smaller the height of the relief printing element.

On a form made using analog technology, the printing elements of raster dots, on the contrary, exceed the die in height. Thus, the printing elements on a plate made by digital mask technology differ in size and height from the printing elements formed by analog technology.

The profiles of the printing elements also differ. So, the printing elements on the forms made by digital technology have steeper side edges than the printing elements of the forms obtained by analog technology.

Direct laser engraving technology includes only one operation. The mold manufacturing process is as follows: the plate without any pre-treatment is mounted on a cylinder for laser engraving. The laser forms the printing elements by removing material from the space elements, that is, the space elements are burned out (Fig. 11).

Rice. Fig. 11. Scheme of direct laser engraving: D and f are the aperture and focal length of the lens; q - beam divergence

After engraving, the form does not require treatment with washable solutions and UV radiation. The form will be ready for printing after rinsing with water and drying for a short time. Dust particles can also be removed by wiping the mold with a damp soft cloth.

On fig. 12 presented structural scheme technological process production of photopolymer flexographic printing plates using direct laser engraving technology.

The first engraving machines used a 1064nm infrared high-power ND:YAG neodymium yttrium aluminum garnet laser to engrave rubber sleeves. Later, they began to use a CO2 laser, which, due to its high power (up to 250 W), has O performance, and due to its wavelength (10.6 microns) allows you to engrave a wider range of materials.

The disadvantage of CO2 lasers is that they do not provide image recording with lineatures of 133-160 lpi, necessary for modern level flexographic printing, due to the large beam divergence q. For such lineatures, the image should be recorded with a resolution of 2128-2580 dpi, that is, the size of an elementary point of the image should be approximately 10-12 microns.

The spot diameter of the focused laser radiation must correspond in a certain way to the calculated size of the image dot. It is known that at proper organization laser engraving process, the spot of laser radiation should be much larger than the theoretical size of the dot - then there is no unprocessed material between adjacent lines of the recorded image.

Increasing the spot by 1.5 times gives the optimal diameter of the elementary point of the image: d 0 = 15-20 µm.

In the general case, the diameter of the CO2 laser radiation spot is about 50 μm. Therefore, printing plates obtained by direct CO2 laser engraving are mainly used for printing wallpaper, packaging with simple patterns, notebooks, that is, where high-line raster printing is not required.

Recently, there have been developments that allow increasing the resolution of image recording by direct laser engraving. This can be done through the skilful use of overlapping laser recording points, which make it possible to obtain elements smaller than the spot diameter on the form (Fig. 13).

Rice. 13. Obtaining small details on the form using overlapping laser spots

To do this, laser engraving devices are modified in such a way that it is possible to change from one beam to work with several beams (up to three), which, due to different power, engrave the material to different depths and thus provide better formation of slopes of raster dots. Another innovation in this area is the combination of a CO2 laser for pre-embossing, especially in deep areas, with a solid-state laser, which, due to the much smaller spot diameter, can form the slopes of the printing elements of a predetermined shape. The limitations here are set by the mold material itself, since the radiation of the Nd:YAG laser is not absorbed by all materials, in contrast to the radiation of the CO2 laser.

Usage: in printing for the manufacture and processing of letterpress photopolymer clichés, the essence of the invention: the finished photopolymer printing plate is irradiated with an electron beam and / or y-quanta in the energy range of 0.5-10 MeV with a particle flux density of 10tT-1012 particles / cm2 s in within 1-30 min. 1 tab.

RESG!U1 LIK (19) s

K (2 (2 (4 (7 ve (7 (7 ve (5

F m skrash f m to st g

STRONG 1-!OE IlAI F. I I I IOE house of the ussr

SPATENT USSR)) 5018354/12

) 08/30/93. Bull. No. 32

) A.P. Ignatiev, V.A. Senyukov and M.E. Berg

) Limited Liability Partnership "Firma Triam"

6234. class B 41 N 1/00, 1983.

The invention relates to a technology for the production and processing of photopolymer ate forms based on a solid photoporous material, in particular letterpress topolymer clichés, and can be used in the printing industry.

The purpose of the invention is to expand the temperature range of use and improve the performance characteristics of the topolymer printing plate by changing the physico-mechanical properties of the foiler. /or y-quanta in the energy shaft 0.5 - 10 MeV with a particle flux density of 10 -10 particles / (cm, s) value 1 - 30 min.

The essence of the proposed honeycomb method is that the finished polymer form is exposed to ionizing (sI>c B 41 N 1/00, B 41 C 1/10, G 03 F 7/26 (54) : in the printing industry for the manufacture and processing of letterpress photopolymer cliches, The essence of the invention: the finished photopolymer printing plate is irradiated with an electron beam and / or y-quanta in the energy range of 0.5 - 10 MzV with a particle flux density of 10 -10 particles / cm s in tt 12 2 for 1 - 30 min. 1 table of radiation, while the products of ionization and excitation of molecules of polymer compounds are distributed over the volume of irradiated printing plates in accordance with the distribution of absorbed doses. Thus, selecting the appropriate distribution and dose rate in the irradiated sample , it is possible to obtain new desirable properties of a photopolymer compound that do not arise without a radiation-chemical process.Irradiation of the finished polymer form with an electron beam and / or y-quanta allows you to expand the temperature range of using photopolymer plates up to 200 C, increase the elastic limit and Young's modulus, increase the hygroscopicity of photopolymer printing plates, which ultimately improves. performance characteristics of letterpress photopolymer clichés and allows them to be used at elevated temperatures.

1838158 known photopolymers of the type "Cellophot" and "Flexophot" as follows.

Example 1. A sample of a printing plate made of a cellophot-type photopolymer is irradiated with an electron beam with an energy of 8 MeV for 15 minutes with an electron beam current equal to

19 μA, Measurement of physical and mechanical parameters is carried out at a temperature of 20 C, Example 2. A sample of a printing plate of a photopolymer of the "Flexophot" type is irradiated with an electron beam with an energy of 10 MeV with an electron beam current of 10 μA for 25 minutes. Measurement of physical and mechanical parameters is carried out at a temperature of 20 C, 15

Example 3. Similar to example 1.

Measurement of physical and mechanical parameters is carried out at a temperature of 140 C.

The modes of the method were chosen based on the following considerations: at an electron energy below 0.5 MeV (Ee 10 MeV, photonuclear reactions, the equipment is activated, a radiation hazard arises, When the electron flux density

P 10 electrons/cm.s, a significant amount of absorbed energy leads to radiation heating and destruction of the photopolymer plate.

In the study of changes in the physico-mechanical properties of photopolymers on- "O", the following characteristics were determined, the modulus of elasticity (Young's modulus), the limit of elasticity, and hygroscopicity.

Research data on the physical and mechanical properties of photopolymers are given in Table 45.

From the Bèäno table, after irradiation, for a photopolymer of the "Cellophot" type, in comparison with the initial sample, the elastic modulus increases by 30-40, and the elastic limit - by 4 times. For photopolymer type

"Fleksofot" after irradiation compared with the original sample, Young's modulus increases by 4.8 times, the elastic limit by 44 times, and the hygroscopicity by 50, which significantly affects the quality of the prints. The photopolymer of the "Flexofot" type after irradiation becomes hydrophilic, which makes it possible to use various stamp paints up to conventional inks without degrading the quality of prints.

"Cellophot" at an elevated temperature (up to 150 C) showed that Young's modulus increases by 1.8 times, the elastic limit - by 3.6 times, and if at an elevated temperature the print run of unirradiated cellophote is 0, then after irradiation the number of prints is 10,000 copies. An increase in the thermal stability of the Cellophot type photopolymer under the action of ionizing radiation will make it possible to abandon the use of metal in the creation of printing plates operating at elevated temperatures. method, operable at a temperature of the order

200 C and can be used in circulation more than 10,000 times without destroying the printing plate.