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 side of the negative, 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

), 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 side of the negative, 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.

Big 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 mass 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. In gravure rotary printing machines, space and printing ... ... Brief Dictionary for printing

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 a flexo printing press printing machine rather liquid ink is applied to the printing plate fixed on the 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 elastic printing plates and low-viscosity fast setting inks allows for high speed seal 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 inverted with respect to the readable image on paper (Fig. 1).

Modern flexo printing uses photopolymer printing forms(FPF), which are not inferior to offset in terms of printing and technical and reproduction and graphic properties, and in terms of circulation resistance, as a rule, surpass them.

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 supplied to the printing company in the form of photopolymerizable 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. After washing, drying of photopolymer forms is required. 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 of photopolymer printing plates 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 the printing elements is also affected by the ratio of exposures of preliminary and main exposure, the duration of which and their ratio are selected for various types and batches of photopolymer plates for specific exposure units.

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 of the photopolymer 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 important technological operation, which 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 the 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 scale of the image on the photoform along one of its sides, oriented in the direction of motion. paper web(ribbons) in the printing press.

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 manufacture of photopolymer flexographic printing plates using the “computer-printing plate” technology is based on the use of laser methods for processing plate materials: ablation (destruction and removal) of the mask layer from the surface of the plate and direct engraving of the plate 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 μm 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 plates in the "computer-printing plate" technology, plates based on solid photopolymer compositions are used, which provide high quality printing plates, the further processing of which occurs in the same way as analog flexo photopolymer plates.

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. There is a protective foil on both surfaces of the plate, and a stabilizing layer is located between the photopolymerizable layer and the base, which provides almost complete absence 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.

Recently, 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. To process plates 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.

When manufacturing flexographic plates using the digital mask layer ablation technology, it must be borne in mind that the formed printing elements, in contrast to exposure through a photoform in traditional (analogue) technology, turn out to be 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. 11. Scheme of direct laser engraving: D and f - aperture and focal length lenses; 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 is a block diagram 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 the modern level of flexo 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.

3. Manufacture of letterpress forms based on photopolymer compositions

An essential factor in the development of flexographic printing was the introduction of photopolymer printing plates. Their use began in the 1960s, when DuPont introduced the first Dycryl letterpress plates to the market. However, in flexo they could be used to make original cliches, from which matrices were made, and then rubber molds by pressing and vulcanization. A lot has changed since then.

Today, the following manufacturers of photopolymer plates and compositions are best known on the global flexographic printing market: BASF, DUPONT, Oy Pasanen & Co, etc. Due to the use of highly elastic forms, this method allows printing on various materials while creating a minimum pressure in the print contact zone ( we are talking about the pressure that is created by the printing cylinder). These include paper, cardboard, corrugated cardboard, various synthetic films (polypropylene, polyethylene, cellophane, polyethylene terephthalate lavsan, etc.), metallized foil, combined materials (self-adhesive paper and film). The flexographic method is used mainly in the field of packaging production, and also finds application in the manufacture of publishing products. For example, in the USA and Italy, about 40% of the total number of all newspapers are printed flexographically on special flexographic newspaper units.

There are two types of plate material for making flexographic plates: rubber and polymer. Initially, the plates were made on the basis of rubber material, and their quality was low, which, in turn, made the quality of flexo prints in general poor. In the 70s of our century, a photopolymerizable (photopolymer) plate was first introduced as a plate material for the flexographic printing method. The plate made it possible to reproduce high-line images up to 60 lip/cm and above, as well as lines with a thickness of 0.1 mm; dots with a diameter of 0.25 mm; text, both positive and negative, from 5 pixels and bitmap 3-, 5-, and 95-percentage points; thus allowing flexography to compete with the "classic" methods, especially in the field of packaging printing. And, naturally, photopolymer plates have taken a leading position as a plate flexographic material, especially in Europe and in our country.

Rubber (elastomer) printing plates can be obtained by pressing and engraving. It should be noted that the molding process itself based on elastomers is laborious and not economical. The maximum reproducible lineature is about 34 lines/cm, i.e. the reproduction capabilities of these plates are at a low level and do not meet modern packaging requirements. Photopolymer forms allow you to reproduce both complex color and transitions, various tonalities, and bitmaps with a lineature up to 60 lines / cm with a rather small pulling apart (increasing tonal gradations). Currently, as a rule, photopolymer forms are made in two ways: analog - by exposing UV radiation through a negative and removing unpolymerized polymer from gaps using special wash solutions based on organic alcohols and hydrocarbons (for example, using a wash solution from BASF Nylosolv II ) and by means of the so-called digital method, i.e. laser exposure of a special black layer deposited on top of the photopolymer layer, and subsequent washing out of unexposed areas. It is worth noting that recently new developments by BASF have appeared in this area, which make it possible to remove the polymer in the case of analog plates using ordinary water; or directly remove the resin from the gaps using laser engraving in the case of digital mold making.

The basis of a photopolymer plate of any type (both analog and digital) is a photopolymer, or the so-called relief layer, due to which the formation of raised printing and recessed blank elements, i.e. relief, occurs. The basis of the photopolymer layer is a photopolymerizable composition (FPC). The main components of FPC, which have a significant impact on the printing and technical characteristics and quality of photopolymer printing plates, are the following substances.

1) Monomer - a compound of relatively low molecular weight and low viscosity, containing double bonds and, therefore, capable of polymerization. The monomer is a solvent or diluent for the remaining components of the composition. By changing the monomer content, the viscosity of the system is usually controlled.

2) Oligomer - capable of polymerization and copolymerization with a monomer, an unsaturated compound of a molecular weight greater than the monomer. These are viscous liquids or solids. The condition for their compatibility with the monomer is solubility in the latter. It is believed that the properties of cured coatings (eg, photopolymer printing plates) are determined mainly by the nature of the oligomer.

As oligomers and monomers, oligoether- and oligourethane acrylates, as well as various unsaturated polyesters, are most widely used.

3) Photoinitiator. The polymerization of vinyl monomers under the action of UV radiation can, in principle, proceed without the participation of any other compounds. This process is simply called polymerization and is rather slow. To speed up the reaction, small amounts of substances (from fractions of a percent to percent) are introduced into the composition, capable of generating free radicals and/or ions under the action of light, initiating a polymerization chain reaction. This type of polymerization is called photoinitiated polymerization. Despite the insignificant content of the photoinitiator in the composition, it plays an extremely important role, which determines both many characteristics of the curing process (photopolymerization rate, exposure latitude) and the properties of the obtained coatings. Derivatives of benzophenone, anthraquinone, thioxanthone, ascilphosphine oxides, peroxy derivatives, etc. are used as photoinitiators.

The nyloflex ACE plate is designed for high quality flexo screen printing in areas such as:

Flexible film and paper packaging;

Beverage packaging;

Labels;

Pre-sealing of corrugated cardboard surface.

It has the highest hardness among all nyloflex plates - 62 ° Shore A (Shore A scales). Main advantages:

Plate color change during exposure - the difference between exposed / unexposed areas of the plate is immediately visible;

Large exposure latitude ensures good fixation of halftone dots and clean indentations on reverses, masking is not required;

A short time processing (exposure, washing, finishing) saves work time;

A wide range of tone gradations on the printed form allows you to simultaneously print raster and line elements;

Good contrast of printed elements facilitates installation;

High-quality ink transfer (especially when using water-based inks) allows you to evenly reproduce the raster and solid, and reducing the required amount of transferred ink makes it possible to print smooth raster transitions;

High hardness with good stability, transfer of high-line raster transitions when using the technology of "thin printing plates" in combination with compression substrates;

Wear resistance, high circulation-resistance;

Ozone resistance prevents cracking.

The plate shows excellent ink transfer, especially when using water-based inks. In addition, it is well suited for printing on rough materials.

Nyloflex ACE can be supplied in the following thicknesses:

ACE 114-1.14mm ACE 254-2.54mm

ACE 170-1.70 mm ACE 284-2.84 mm

The plate has a low hardness (33° Shore A), which ensures good contact with the rough and uneven surface of the corrugated board and minimizes the washboard effect. One of the main advantages of FAC-X is its excellent ink transfer, especially for water-based inks used in printing on corrugated board. Uniform printing of plates without high printing pressure helps to reduce the increase in gradations (dot gain) during raster printing and increase the contrast of the image as a whole. In addition, the plate has a number of other distinctive features:

The violet shade of the polymer and the high transparency of the substrate make it easier to control images and mount forms, using adhesive tapes, on a plate cylinder; - high bending strength of the plate eliminates peeling of the polyester substrate and protective film;

The form is well cleaned both before and after printing.

The nyloflex FAC-X plate is single layer. It consists of a photosensitive photopolymer layer deposited on a polyester substrate for dimensional stability.

Nyloflex FAC-X is available in 2.84mm, 3.18mm, 3.94mm, 4.32mm, 4.70mm, 5.00mm, 5.50mm, 6.00mm, 6.35mm .

Relief depth of nyloflex FAC-X plates is set by pre-exposure reverse side plates by 1 mm for plates with a thickness of 2.84 mm and 3.18 mm and in the range from 2 to 3.5 mm (depending on each specific case) for plates with a thickness of 3.94 mm to 6.35 mm.

With nyloflex FAC-X plates, it is possible to obtain screen lineature up to 48 lines / cm and a gradation interval of 2-95% (for plates with a thickness of 2.84 mm and 3.18 mm) and a screen lineature of up to 40 lines / cm and a gradation interval of 3-90% (for inserts with a thickness of 3.94 mm to 6.35 mm). The choice of plate thickness is guided both by the type of printing machine and the specifics of the printed material and the reproduced image.

The digiflex II photopolymer plate was developed from the first generation of digiflex plates and combines all the advantages of digital communication with even simpler and easier processing. Benefits of the digiflex II plate:

1) No photographic film, which enables direct transfer of data to the printing plate, protecting the environment and saving time. After removing the protective film, a black layer becomes visible on the surface of the plate, which is sensitive to infrared laser radiation. Image and text information can be written directly on this layer using a laser. In places that are affected by the laser beam, the black layer is destroyed. After that, the printing plate is exposed to UV rays over the entire area, washed, dried, and the final illumination occurs.

2) optimal transfer of gradations, allowing to recreate the slightest shades of the image and providing high quality printing;

3) low installation costs;

4) the highest quality of the press. The basis of laser-exposed photopolymer printing plates are nyloflex FAH printing plates for highly artistic raster flexographic printing, which are covered with a black layer. The laser and subsequent conventional exposures are chosen such that significantly lower gradation increments are achieved. You get exceptionally high quality print results.

5) reduced load on environment. No film processing not used chemical compositions for photo processing, closed exposure and washing units with closed regeneration devices lead to a reduction in the harmful impact on nature.

The scope of plates for digital transmission of information is wide. These are paper and film bags, corrugated cardboard, films for automatic machines, flexible packaging, aluminium foil, film bags, labels, envelopes, napkins, beverage packaging, cardboard products.

Nyloflex Sprint - new for Russian market plate from the nyloflex series. At the moment, it is being tested at a number of production printing enterprises in Russia. This is a special water washable plate for printing with UV inks. Washing with ordinary water makes sense not only from a nature protection point of view, it also significantly reduces the processing time compared to the technology using an organic wash solution. The nyloflex sprint plate requires only 35-40 minutes for the entire deprinting process. Due to the fact that only clean water is needed for flushing, nyloflex sprint also saves on additional operations, because the used water can be poured directly into the sewer without filtration or additional treatment. And for those who already work with nyloprint water-washable plates and letterpress processors, they don't even need to buy additional equipment.

Modern photopolymer forms (FPF). General scheme for the manufacture of the FPF

The use of photopolymer printing plates began in the 60s. An essential factor in the development of flexographic printing was the introduction of photopolymer printing plates. Their use began in the 1960s, when DuPont introduced the first Dycryl letterpress plates to the market. However, in flexo they could be used to make original cliches, from which matrices were made, and then rubber molds by pressing and vulcanization. A lot has changed since then.

Today, the following manufacturers of photopolymer plates and compositions are best known on the global flexographic printing market: BASF, DUPONT, Oy Pasanen & Co, etc. Due to the use of highly elastic forms, this method allows printing on various materials while creating minimal pressure in the print contact zone (we are talking about pressure generated by the impression cylinder). These include paper, cardboard, corrugated cardboard, various synthetic films (polypropylene, polyethylene, cellophane, polyethylene terephthalate lavsan, etc.), metallized foil, combined materials (self-adhesive paper and film). The flexographic method is used mainly in the field of packaging production, and also finds application in the manufacture of publishing products. For example, in the USA and Italy, about 40% of the total number of all newspapers are printed flexographically on special flexographic newspaper units. There are two types of plate material for making flexographic plates: rubber and polymer. Initially, the plates were made on the basis of rubber material, and their quality was low, which, in turn, made the quality of flexo prints in general poor. In the 70s of our century, a photopolymerizable (photopolymer) plate was first introduced as a plate material for the flexographic printing method. And, naturally, photopolymer plates have taken a leading position as a plate flexographic material, especially in Europe and in our country.

Production of the FPF.

In the manufacture of photopolymer forms of flexographic printing, the following main operations are performed:

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