DE2301175A1 - PROCESS FOR MANUFACTURING PRINTING FORMS FOR FLEXO PRINTING AND MULTI-LAYER PLATES FOR THIS - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG "lonitnn

230 ι 1/5

Our reference: 0.Z.29 640 W / L 6700 Ludwigshafen, 10.1.1973

Process for the production of printing forms for flexographic printing and

Multilayer panels therefor

The invention relates to a method for producing relief printing plates for flexographic printing by imagewise exposure of a photo-crosslinkable which is applied to a multilayer substrate Layer and a photocrosslinkable multilayer plate therefor.

So-called flexographic printing is used to print packaging materials, for example paper, corrugated cardboard, cell glass, metal foils and, in particular, plastic foils. For flexographic printing, rubber sheets are currently used almost exclusively made of one or more layers of vulcanized rubber, some of which are provided with fabric inserts, the printing rubber layer often consisting of a rubber type specially adapted to the printing material and the carrier layer consisting of an abrasive rubber. It is also known to use other plastic materials, such as polyvinyl chloride, as the base material for such printing plates in addition to the customary types of rubber. A particular disadvantage of the common rubber printing plates is their very costly and time-consuming production, which involves producing an original metal plate by exposure and etching, embossing it with a suitable mat material and then making the rubber clichés by embossing the material and vulcanizing the cliché material under heat and pressure runs. Often it is also necessary to regrind the back of the vulcanized rubber clichés. Another clear disadvantage of the rubber clichés customary in practice is the format size to be used, which is limited by the size or format of the existing and very expensive embossing presses.
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Photopolymers or phot ο networkable printing plates where a Relief by imagewise exposure of a photo-crosslinkable layer and subsequent washing out of the unexposed parts of the layer takes place with a developer liquid are known per se. Recently there has also been a corresponding production of flexible printing plates for flexographic printing have been described, for example in U.S. Patents 2,948,611 and 3,024,180 or the German Offenlegungsschrift 2,062,563 and 2,138,582 photo-crosslinkable layers consist of a mixture of an elastomeric polymer such as chloroprene or nitrile rubber, a photocrosslinkable or photopolymerizable monomer with C-C multiple bonds and a photoinitiator. The reliefs produced in this way, however, often show "only an inadequate Flexibility and insufficient conformability to the rough substrates with thickness differences that are common in flexographic printing on. The also known production of photopolymer printing plates from light-sensitive liquid low molecular weight The disadvantage of prepolymers is that they have their own coating equipment for producing layers from the sticky, highly viscous liquids are required, and furthermore the negative cannot be placed directly on the surface to be exposed.

The present invention was based on the object of providing relief printing forms suitable for flexographic printing with improved printing properties in a simple way to manufacture.

It has now been found that flexographic printing is particularly suitable Can produce relief printing forms by imagewise exposure of a photo-crosslinkable layer A based on a Photoinitiator-containing mixture of at least one polymer (P) with a minor amount of at least one largely compatible photocrosslinkable monomers with at least one C-C multiple bond (M), the layer A on one side with a Intermediate layer Z is connected to a dimensionally stable support (T), and subsequent washing out of the unexposed Parts of layer A with a developer liquid, we ^ n. man a photocrosslinkable layer A is exposed and washed out,

a) their. Content of polymer (P) wholly or predominantly from a soluble in the developer liquid using

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polyurethane elastomers produced from aliphatic polyisocyanates consists,

b) which has a hardness of 50 to 90 Shore A in the photo-crosslinked state,

c) the firmly adhered with a non-photo-crosslinkable intermediate layer Z is connected on the basis of an elastomeric polymer,

C ₁ ) whose hardness is in the hardness range from 15 to 70 Shore A and at least 20 Shore A less than the hardness of layer A in the photo-crosslinkable state,

C ₂ ) which is not dissolved by the developer liquid when the layer A is washed out and

C ₅ ) which in turn is connected to a dimensionally stable carrier T.

The invention also relates to photocrosslinkable multilayer plates for the production of relief printing forms for flexographic printing according to the method according to the invention and in particular those that are between

a) a 0.1 to 4 mm thick photocrosslinkable layer A,

&. * ) which consists essentially of a photoinitiator-containing mixture of polymers P, predominantly consisting of a polyurethane elastomer soluble in the developer liquid, and photo-crosslinkable monomers M with at least one CC multiple bond and

a ₂ ) which has a hardness of 50 to 90 Shore A in the photo-crosslinked state and '

b) a non-photocrosslinkable, non-photocrosslinkable and insoluble in the developer fluid, 0.1 to 6 mm have strong intermediate layer Z, wherein the intermediate layer Z consists essentially of an elastomeric polymer and the hardness of the intermediate layer Z is in the hardness range from 15 to 70 Shore A and 20 to 50 Shore A is less than the hardness of layer A in the photo-crosslinked state.

In the preferred embodiment of the invention, both the photocrosslinkable layer A and the intermediate layer Z have

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a polyurethane elastomer as the base material, which, however, differs in terms of elasticity, its Shore hardness and its Differentiate solubility.

The flexographic printing plates produced according to the invention make it possible a significantly improved design of the raster points compared to the usual G-ummidruckplatten, which are molded from a die will. This leads to excellent halftone reproductions, where there is no difficulty as before to depict lines and writing next to grid areas. Besides the improvement of the printed image is made possible by the printing plate produced according to the invention with its flexible, elastic intermediate layer a better adaptation and nestling of the printing surface to the different substrates than the known ones single-layer photopolymer plates. In the printing plates produced according to the invention, the elastic intermediate layers take over a sufficient cushioning of the crosslinked top layer A and the elastic overcoming of tolerances of the printing material as well as the machines.

According to the invention for the production of relief printing forms Multi-layer plates used for flexographic printing consist of the photocrosslinkable layer A, at least one less hard layer Intermediate layer Z and a carrier layer T. It is of course possible that the light-crosslinking layer A on its surface still has a cover layer or protective layer made of a translucent wax or a plastic material.

The photocrosslinkable layer A, which generally has a thickness of about 0.1 to 4 and preferably about 0.5 to 1.5 mm, consists essentially of a mixture of one or more polymers and photocrosslinkable monomers with C-C multiple bonds. The polymer content of the mixture is generally about 55 to 90 percent by weight, preferably 70 to 90 percent by weight, and the monomer content expediently about 10 to 45 and preferably about 10 to 30 percent by weight of the Polymer-monomer mixture. The polymer component consists wholly or predominantly of one in the developer liquid soluble, using aliphatic polyisocyanates

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manufactured polyurethane elastomers. Such elastomeric high molecular weight Polyaddition products can be made from a polyether glycol or, in particular, a polyester glycol, which at least is predominantly and preferably built up exclusively from aliphatic components, by reaction with aliphatic polyisocyanates and in particular aliphatic diisocyanates in excess and subsequent reaction with a diol or poly oil, preferably an aliphatic diol or polyoil, where the molar ratio of the NCO groups to the OH groups is between 0.9 and 1.0 and preferably between 0.96 and 1.0 target. Aliphatic polyisocyanates or diisocyanates and aliphatic polyols or diols are also used here cycloaliphatic compounds viewed as aliphatic. The polyurethanes should have sufficient solubility in contain the developer liquids used on the printing plate, for which e.g. ketones, such as acetone, methyl ethyl ketone, or cyclohexanone, cyclic ethers, such as tetrahydrofuran, 1,4-dioxane, also ethyl acetate, dimethylformamide or mixtures of these solvents be used. Suitable polyurethanes with K values (according to H. Pikentscher, Cellulosechemie _1_3 (1932), P. 58 ff.) From about 60 to 70 and form elastic, tack-free films are commercially available. The very appropriate ones Polyurethanes for the top layer should only have one in the actinic absorption range of the photoinitiator used have low light absorption.

Suitable polyurethane elastomers can be made from polyester or polyether glycols and aliphatic diisocyanates with concomitant use are produced by diols as chain extenders. Polyester glycols with two free hydroxyl groups that can be used for this purpose at the chain ends expediently have a molecular weight of about 500 to 10,000 and preferably from 1,000 to 5,000 and can be made from saturated aliphatic dibasic acids with 4 to 12 carbon atoms, such as succinic acid, adipic acid or dodecanedioic acid, and aliphatic diols having 2 to 10 carbon atoms. The hydroxyl number these polyester glycols with two free hydroxyl groups correspond to average molecular weights from 1,000 to 5,000. Instead of the polyester glycols or in a mixture with them

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can also polyether glycols with a molecular weight of about 500 to 8,000 and preferably from about 1,000 to 5,000 can be used. The condensation products of ethylene glycol, for example, are suitable and / or propylene glycol or other diols, or their reaction products with ethylene oxide and / or propylene oxide, their Hydroxyl number corresponds to an average molecular weight of about 1,000 to 5,000.

Suitable aliphatic polyisocyanates or diisocyanates for polyurethane production, including - as mentioned - cycloaliphatic Isocyanates are to be understood, are e.g. hexamethylene diisocyanate, Isophorone diisocyanate, diisocyanatocyclohexane, bis (4-isocyanatocyclohexyl) methane and similar polyisocyanates as well as their mixtures. Suitable aliphatic diols as chain extenders are e.g. 1,4-butanediol, 1,6-hexanediol, 1,8 octanediol, diethylene glycol, triethylene glycol, thiodiglycol or 1,3- and 1 ^ -bis-hydroxymethylJ-cyclohexane. From the polyester and / or polyether polyols, a prepolymer can also be prepared by adding a deficiency of diisocyanate, whereby a polyurethane with two terminal hydroxyl groups is formed, which is then mixed with diisocyanate in a known manner and diol can be reacted. Of course you can for the manufacture the polyurethane elastomers also prepolymers from the polyester and / or polyether glycols and excess diisocyanates come into use. In this case, these prepolymers are crosslinked in an equally known manner Addition of polyols. ' In general, when the hydroxy compounds are reacted with the diisocyanates, the molar ratio of the isocyanate groups to the hydroxyl groups are 0.9 to 1.0 and preferably between 0.96 and 1.0.

In some cases, especially to achieve higher durometer hardnesses, it may be expedient to use a polyurethane elastomer as the polymer component instead of the exclusive use of a polyurethane elastomer Mixture of the same with minor amounts, in particular with about 1 to 30 # of its weight of another polymer use that is compatible with the polyurethane elastomer and thus does not lead to clouding of the photocrosslinkable layer. Suitable polymers for such a modification of the properties

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The photo-crosslinkable layer is, for example, vinyl chloride and Vinylidene chloride polymers, cellulose esters and soluble phenoxy resins.

As monomers with at least one photocrosslinkable C-C multiple bond all monomers with C-C multiple bonds that are largely compatible with the other components of layer A are suitable, those by electromagnetic radiation in the presence of a photopolymerization initiator for photocrosslinking or photopolymerization can be brought.

The main monomers are monomers with at least two C-C double bonds suitable, which are crosslinked or photopolymerized by irradiation in the presence of a photoinitiator can, for example, polyolefinically unsaturated carboxylic acid esters, e.g. diesters of aliphatic and cycloaliphatic Diols having preferably 2 to 10, in particular 2 to 6, carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol or cyclohexanediol-1,4-f and monoethylenically unsaturated monocarboxylic acids with 3 to 5 carbon atoms, such as acrylic acid or methacrylic acid, also polyvalent vinyl esters of polycarboxylic acids, in particular divinyl esters of aliphatic or aromatic dicarboxylic acids, preferably containing 4 to 8 carbon atoms, vinyl esters of monoolefinically unsaturated, preferably 3 to 5 carbon atoms, monocarboxylic acids, allyl carboxylic acid esters, in particular of saturated or monoolefinically unsaturated dicarboxylic acids containing up to 8 carbon atoms, the unsaturated Carboxylic acid esters usually have 2 or 3 olefinic double bonds. As polyolefinically unsaturated monomers come furthermore polyolefinically unsaturated carboxamides in question, such as the diamides from acrylic acid or methacrylic acid and aliphatic diamines, as well as dieters of aliphatic or cycloaliphatic diols with preferably 2 to 10, in particular 2 to 6 carbon atoms, such as ethylene glycol or 1,4-butanediol and N-methylolacrylamide or N-methylol methacrylamide. Examples suitable monomers are ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate or the equivalent Dirnethacrylate, cyclohexanediol-1,4-diacrylate, divinyl maleate, Divinyifumarate, vinyl acrylate, vinyl crotonate, allyl

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acrylate, diallyl phthalate, diallyl maleate or allyl-α-chloroacrylate. Instead of monomers with at least 2 C-C multiple bonds, in some cases, in particular to achieve an improved compatibility of the monomers with the polymers, mixtures of monomers are used in addition to at least 50 percent by weight of such monomers, additionally 0.1 to 50 percent by weight, which are copolymerizable by irradiation Contain monoethylenically unsaturated monomers, such as acrylic and / or methacrylic acid esters of alkanols or cycloalkanol, acrylic and / or methacrylic acid amides or their N-methylol compound as well as their ethers with alcohols. Monomers may be mentioned as such 2-hydroxyethyl acrylate, 1,4-butanediol monoacrylate, acrylamide, Methacrylamide, N-methylolacrylamide, N-methylol-acrylamide methyl ether

The photocrosslinkable layer A also contains finely divided still small amounts of photopolymerization initiators, i.e. compounds that under the action of light of one wavelength from 300 to 700 µm and preferably 300 to 420 µm, in Radicals decay or, in the process, generate radicals through a reaction that start the polymerization «, examples of suitable ones Photoinitiators are vicinal ketaldony! Compounds, such as diacetyl and benzil, α-ketaldonyl alcohols such as benzoin, acyloin ethers such as benzoin methyl ether, benzoin isopropyl ether or α-methylolbenzoin methyl ether and aromatic acyloins substituted in the α-position, such as α-methylbenzoin, aromatic ketones and Aldehydes such as benzophenone, propiophenone or benzaldehyde. The photopolymerization initiators are generally used in amounts from 0.001 to 10 and preferably from 0.01 to 5 percent by weight, based on the monomers, added

The photocrosslinkable layer can also contain the usual additives, such as inhibitors for thermal polymerization, e.g. p-benzoquinone, p-methoxyphenol, mono-tert.-butylhydroquinone, Phenothiazine, methylene blue, ß-naphthylamine, ß-naphthol or salts of N-ITitrosocyclohexy! hydroxylamine «The The amount of these additives is generally from 0.01 to 3 percent by weight of the constituents of layer Ao

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ORIGINAL INSPECTED

In some cases it has - especially for better assessment the picture elements - proven to be useful, the photocrosslinkable ones Layer A to add a dye which - provided it does not absorb any self-absorption in the actinic region of layer A. - can be added in any amount. If the dye shows self-absorption in the actinic region, then according to its absorption in an amount of 0.001 to 2.5 percent by weight, preferably 0.005 to 0.5 percent by weight, based on the layer A, added.

The characteristic of the multilayer plates processed according to the invention into relief printing forms for flexographic printing is that their photocrosslinkable layer A firmly adheres to a non-photocrosslinkable Intermediate layer Z is connected on the basis of an elastomeric polymer, the hardness of which is in the hardness range from 15 to 70 Shore A and in particular between 20 and 60 Shore A and at least 20 Shore A, preferably 20 to 50 Shore A less is than the hardness of the layer A in the photo-crosslinked state. Another characteristic of this intermediate layer is that it is washed out of the unexposed constituents of layer A is not dissolved by the developer liquid after the photo-crosslinking. The thickness of the intermediate layer Z is generally 0.1 to 6 mm and preferably 1 to 3 mm. Suitable and economical Interlayers consist e.g. of natural rubber, styrene-butadiene rubber, Polybutadiene rubber, butadiene-acrylonitrile rubber, elastomeric ethylene-propylene copolymers, elastomeric propylene oxide polymers, silicone rubber, polysulphide rubber and vinylidene fluoride-hexafluoropropylene elastomeric copolymers. In all cases the elastomeric materials must have the have specified low hardness and can be brought into sheet or plate shapes. The firm connection of the Interlayer with the top layer can be made more solvent-resistant with the help of Adhesives, e.g. based on elastic polyurethane or polychloroprene reactive adhesives or epoxy two-component adhesives be accomplished, which are applied on one or both sides of the layers to be connected, e.g. in a layer thickness of about 10 / µm.

This procedural disadvantage can be avoided if

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polyurethane elastomers are also more suitable for the intermediate layer Z. Hardness, which are not soluble in the developer liquid, can be used. You have the advantage of being because of the same or similar composition as the top layer In most cases, it is sufficiently firmly connected to layer A directly by simply lamination using a lamination solution can be. In addition, intermediate layers Z made of polyurethane elastomers have excellent mechanical properties in terms of elasticity, abrasion resistance, damping behavior, rebound resilience, creep resistance and heat resistance on. Suitable polyurethane sheets or polyurethane layers can be made from liquid starting compounds, such as the above-mentioned polyester glycols or polyether glycols, low molecular weight diols and diisocyanates are produced, which in centrifugal molds or casting molds to form precise layers can be cured. The starting components for the polyurethanes are those for the polyurethanes of layer A above mentioned in coinage with the difference that. for the polyurethanes the intermediate layer Z, aromatic diisocyanates can also be used in their production, such as tolylene diisocyanate. For harder embodiments of the intermediate layer, polyurethane films that are laid in webs are suitable, for example by calendering obtain thermoplastic polyurethane elastomers and are available on the market »

The connection of the photocrosslinkable layer A with the intermediate layer Z can usually take place in a simple manner by laminating the two layers on top of one another, if the two systems are still have sufficient surface tack. Otherwise they are both layers with a suitable laminating liquid such as ethyl acetate, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, Dimethylformamide or other strongly polar solvents, easily brought together.

The support of the multilayer board according to the invention has the task of giving the board good dimensional stability, which is particularly necessary and desirable in multi-color printing. Dimensionally stable is understood here to mean that the Carrier layer under the manufacturing and processing conditions

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of the relief printing forms is dimensionally stable «The carriers can be flexible or rigid, reflect or not reflect the actinic light used for photocrosslinking. Particularly Thin metal supports are suitable because of their high strength, such as thin steel sheets or aluminum sheets »steel sheets are of course particularly suitable when the printing cliché is to be applied to magnetic cylinders Films made of plastic, such as polyester films, are used as carriers, which are usually better than aluminum or steel carriers can be glued on a pressure roller and lifted off again without warping the plate. An adhesive bond the carrier layer T with the intermediate layer Z can be achieved particularly advantageously in that the pouring and curing the polyurethane-forming reaction mixture is carried out directly on the carrier layer, with the optional Polyester film or metal film provided with an adhesive varnish usually develops sufficient adhesive strength. If the intermediate layer Z is separated, e.g. produced as a film, it can be replaced by an adhesive layer based on e.g. Polyurethane or polychloroprene reactive adhesives are brought into a sufficient bond with the carrier layer.

The imagewise exposure and subsequent washing out of the unexposed Parts of the layer A with a developer liquid can be carried out in a manner known per se. For the Exposure, virtually any source of high light intensity can be used, such as xenon lamps, high pressure mercury vapor lamps and low pressure mercury vapor lamps. The wavelength of the applied radiation should be between about 300 and 700 µm and preferably between about 300 and 4-20 µm and must be matched to the self-absorption of the related photoinitiator, i.e. the wavelength of the main one The absorption of the photoinitiator must be present in sufficient intensity in the emitted radiation spectrum of the light source be. The light used for the irradiation is preferably used as area light with diverging radiation Formation of the grid points used. The light intensity should be sufficient to guarantee sufficiently short exposure times. The exposure itself is done through a transparent one

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Copy master which is brought into intimate contact with the light-sensitive layer, for example with the aid of a transparent film pressed on with a vacuum. After exposure, the unexposed parts of layer A can be washed out with a developer liquid such as acetone, methyl ethyl ketone, tetrahydrofuran, dimethylformamide or mixtures of these solvents. The exposed parts of layer A remain as an insoluble relief on intermediate layer _{B, which is also insoluble} are desired if, nachbelichtet yet finally 1 to 20 minutes ,, the resulting printing form is without the required with conventional rubber plates regrinding the back ready to use and may, for example, by means of a double adhesive film on the steel cylinder of a flexographic printing machine can be attached _o

The relief printing plates produced according to the invention produce prints of outstanding quality in flexographic printing with the usual flexographic inks Reproduction accuracy and also prove to be extremely abrasion-resistant and resistant to the printing ink solvents used, With them, linework can be reproduced without restriction next to snapped-in halftone motifs, whereby the soft-elastic intermediate layer has the necessary elasticity of the overall printing form and for a good fit the substrate surface ensures.

The parts mentioned in the examples below relate on weight.

example 1

a) 69.45 parts of a commercially available polyester polyurethane elastomer which is free from isocyanate groups and soluble in methyl ethyl ketone the hardness of 70 Shore A, dissolved in 105 parts of tetrahydrofuran, are mixed with 30 parts of 1,1,1-trimethylolpropane triacrylate (containing 0.05 part of hydroquinone as an inhibitor of thermal polymerization) and 0.5 part of a-methylolbenzoin methyl ether mixed and cast on a polyethylene terephthalate film to form a film with a dry layer thickness of 0.60 mm A sample of layer A was taken with a flat exposure

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ORIGiNAL INSPECTED

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ter irradiated with 60 W UV fluorescent tubes for 25 minutes and then has a hardness of 75 Shore A.

b) 10,000 parts of a dry and bubble-free commercially available aliphatic polyester glycol with a molecular weight of about 2,000 (®Desmophen 2 200 from the Bayer Aa paint factory, Leverkusen) are mixed with 0.6 part Ν, Ν'-endoethylene piperazine as an activator and 900 parts 2, 4-toluene diisocyanate mixed and poured into a 5 m ^ large centrifugal mold. The mixture is then cured ^{at 130 ° C. for 30 minutes.} The resulting 2 mm thick polyurethane elastomer layer Z with a hardness of 36 Shore A is laminated directly to layer A of Example 1 a) in the presence of tetrahydrofuran, so strong adhesion is produced that the relief layer of the photo-crosslinked layer A follows does not come off after washing out, even during the printing process.

The intermediate layer Z is then covered with a polyethylene terephthalate film using a commercially available polyurethane reactive adhesive connected as a carrier »

c) From the resulting multilayer board, consisting of the protective film S over the photocrosslinkable layer A, the over the intermediate layer Z is connected to the carrier film T, the protective film S is peeled off and the uncovered smooth one Surface of layer A with a standard flat exposure unit with 60 W-ÜV fluorescent tubes for 20 minutes an image negative brought into contact with layer A is exposed. After that, the negative image is stripped off, and it the unexposed parts of layer A with methyl ethyl ketone as developer liquid in a spray wash-out device washed out (washout time approx. 7 minutes). The result is a relief image ο The printing form is dried again and directly used in a flexographic printing machine draws the relief image are characterized by great image sharpness and very good reproduction of fine lines and grids.

The printing form gives prints of very good reproduction accuracy and is extremely abrasion-resistant and resistant to the printing ink solvents »

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Example 2

a) A solution of 83.8 parts of a soluble in tetrahydrofuran Polyester polyurethane from an adipic acid-ethylene glycol-1,4-butanediol polyester, Hexamethylene diisocyanate as well as 1,4-butanediol and neopentyl glycol with an NCO / OH ratio 0.97 s 1 in 233 parts of tetrahydrofuran is mixed with 15.0 parts of triethylene glycol diacrylate, 0.2 parts of hydroquinone and 1.0 parts of α-methylolbenzoin methyl ether are added and the mixture is in vacuo concentrated to a solution with a viscosity of about 30,000 cP, which is poured onto a polyethylene terephthalate film and in the dried, solvent-free state provides a film with a thickness of 0.72 mm. (A sample of the photosensitive Layer A is exposed from both sides for 30 minutes in a flat exposure unit and then has a hardness of 66 Shore A on «)

b) The photosensitive layer A obtained is covered with the polyethylene terephthalate film to the outside of a polyurethane elastomer layer Z from Example 1 by moistening the to be connected surfaces applied with tetrahydrofuran and roller, so that a permanent connection between the photosensitive layer A and the elastomer layer Z produced will.

c) With the multilayer plate obtained, consisting of the upper protective film S (polyethylene terephthalate film) over the photocrosslinkable layer A, the polyurethane intermediate layer Z and the carrier film T, proceed as indicated in Example 1, but 10 minutes after the washout process long post-exposure before the relief printing form 20 minutes at
is post-dried.

form 20 minutes at 70 ⁰ C in a fresh air drying cabinet

Example 3

a) 1,000 parts of a hydroxyl-containing polyether based of a reaction product of 11,1-trimethylolpropane with excess propylene oxide-1,2 (Pluracol TP-4040 from the company BASF-Wyandotte Corporation, Wyandotte / Michigan, USA) becomes with 120 parts of 2,4-tolylene diisocyanate and 0.1 part of Ν, Ν'-endo-

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Ethylenpiperazine mixed as activator and ^{heated to 80 0} C for 1 hour. 52 parts of a propylene oxide-1,2-polymer with two hydroxyl groups in the molecule with a molecular weight of about 1000 (Pluracol P 1010 from BASF-Wyandotte Corporation) are mixed into the cooled reaction product, the mixture in one on a carrier of 0.5 mm thick, commercially available polyurethane film, poured onto the mold and ^{cured at 130 °} C. for 30 minutes. The practically cured product with a layer thickness of 3.0 mm has a hardness of 20 Shore A and adheres firmly to the polyurethane film as a carrier T ₀

b) A film consisting of the solution of the photosensitive mixture is applied to the surface of this intermediate layer Z. Example 2, poured on, with a layer A with a thickness of 0.7 mm remaining after the tetrahydrofuran has evaporated, which is covered with a protective film.

c) After peeling off the protective film S from the photocrosslinkable layer of the resulting multilayer plate, layer A is put in a commercially available flat exposure unit with 60 watt UV fluorescent tubes for 20 minutes through a negative film placed on layer A and held by a vacuum-pressed holding film drawn over it. Copy master exposed. After removing the negative, the multi-layer plate is washed out for 8 minutes and then dried for 20 minutes in a spray washout with methyl ethyl ketone at 70 ⁰ C. The relief of the crosslinked layer A that remains on the intermediate layer Z and has not been removed adheres excellently to the intermediate layer Z and does not come off either during the washing process or during printing.

Example 4

a) For a further photo-crosslinkable layer A, a soluble polyester urethane made from adipic acid, butanediol, diethylene glycol and dicyclohexylmethane-4,4'-diisocyanate with a Shore A hardness of 69 is used. 147.39 parts of the polyurethane are dissolved at 60 ⁰ C in 245 parts of tetrahydrofuran ,, with further 50.0 parts of 1,4-butanediol diacrylate, with 0.2 parts of a-Methylolbenzoinmethylather and 0.01 parts Zapon

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Real black (CI. 12 195) offset, so that about 4-5 percent by weight Solution is obtained, which is poured into a mold on the intermediate layer described below Z rests. The wet layer thickness is chosen so that, after the tetrahydrofuran has evaporated, a film thickness of 1.0 mm remains. A sample of this layer A has a hardness of 78 Shore A after 30 minutes of exposure on both sides.

b) To 100 parts of a polyfunctional liquid mercaptan, with a molecular weight of approx. 4,000 (Thiokol LP2 from Thio / 'kol Corp., Trenton, USA), into which 30 parts of finely divided zinc sulfide are rolled, 15 parts of a hardening paste, consisting of 50 # lead peroxide, 5 i "Di-n-butyl phthalate was added and the components mixed together by rolling. The mixture is poured into a 3 mm high mold resting on a thin polyester film and ^{cured while pressing at 100 °} C. within 10 minutes. The elastic layer of polysulphide rubber resulting after curing has a Shore A hardness of 42 and adheres directly to the film carrier.

A firmly adhering compound of the photocrosslinkable compounds that is resistant to the washout solvent methyl ethyl ketone Layer A with the polysulphide rubber layer on polyethylene terephthalate film is applied by thinly applying a commercially available polychloroprene reactive adhesive to the Surfaces and made by rolling both layers together.

c) For the development and manufacture of the ready-to-use multilayer relief plate proceed as in example 2c).

Example 5

a) 48.16 parts of the polyurethane of layer A from Example 4 are added together with 20.64 parts of a phenoxy resin with a molecular weight of 10,000, 30.0 parts of triethylene glycol diacrylate, 1.0 part of α-methylolbenzoin methyl ether and 0.2 part of hydroquinone in 105 parts Tetrahydrofuran at 60 ⁰ C dissolved to a homogeneous solution and with the help of a pouring device

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Polyethylene terephthalate film <applied, after drying in a heated to 60 ⁰ C air stream, the 0.55 mm thick layer with the uncovered layer side to the interlayer glued A sample of the light-sensitive layer has after exposure, the hardness 85 Shore A.

b) A 3 mm thick nitrile rubber plate with a hardness of 40 Shore A is produced from an unvulcanized, commercially available nitrile rubber by vulcanizing for 10 minutes at HO ^{0 O.} The vulcanization is carried out on a 0.2 mm thick steel support, which is provided with a thin layer of adhesive varnish. The rubber layer, firmly adhering to the steel, is applied as an intermediate layer Z with the above photosensitive layer by means of a commercially available polyurethane reactive adhesive by applying a thin layer to the surfaces to be connected.

c) The exposure, development and finishing of the multilayer printing plate takes place as described in example 2c),

-18-409831 / 0443

Claims (9)

- 18 - Ο »Ζ. 29 640 Claims (jy Process for the production of relief printing forms suitable for flexographic printing by imagewise exposure of a photocrosslinkable layer A based on a photoinitiator-containing mixture of at least one polymer (P) with a minor amount of at least one largely compatible photocrosslinkable monomer with at least one CC multiple bond (M), the layer A being connected on one side to an intermediate layer Z on a dimensionally stable carrier T, and subsequent washing out of the unexposed parts of the layer A with a developer liquid, characterized in that a photo-crosslinkable layer A is exposed and washed out, a) their content of polymer (P) wholly or predominantly from a soluble in the developer liquid, using consists of polyurethane elastomers made from aliphatic polyisocyanates, b) which in the photo-crosslinked state has a hardness of 50 to 90 Has Shore A, c) the firmly adhered with a non-photocrosslinkable intermediate layer Z is connected on the basis of an elastomeric polymer, C ₁ ) whose hardness is in the hardness range from 15 to 70 Shore A and at least 20 Shore A less than the hardness of layer A in the photo-crosslinked state, C ₂ ) which is not dissolved by the developer liquid when the layer A is washed out and c-z) which in turn are connected to a dimensionally stable carrier T. is" 2. The method according to claim 1, characterized in that the hardness of the intermediate layer Z is 20 to 50 Shore A below the hardness of the photocrosslinked layer A. 3. The method according to claim 1 or 2, characterized in that the intermediate layer Z has a hardness of 20 to 60 Shore A. 409831/044 3 ~ ¹⁹ ~ - 19 - O.Zc 29 640 4. The method according to any one of claims 1 "to 3, characterized in that the intermediate layer Z consists essentially of a polyurethane elastomer. 5. The method according to any one of claims 1 to 4, characterized in that the layer A has a hardness of 65 to 85 Shore A in the photo-crosslinked state. 6. The method according to any one of claims 1 to 5 » characterized in that the intermediate layer Z is firmly bonded to a sheet-like metal carrier. 7. The method according to any one of claims 1 to 6, characterized in that the layer thickness of the photocrosslinkable layer A is about 0.1 to 4 mm. 8. The method according to any one of claims 1 to 7, characterized in that the layer thickness of the intermediate layer Z is about 0.1 to 6 mm « 9. Photo-crosslinkable multilayer plate for the production of relief printing forms for flexographic printing, characterized in that it is between a) a 0.1 to 4 mm thick photocrosslinkable layer A, which a.j) consisting essentially of a phot ο initiator containing Mixture of polymers P, mainly consisting of a polyurethane elastomer which is soluble in the developer liquid, and photocrosslinkable monomers M with at least one C-C multiple bond and a ₂ ) which has a hardness of 50 to 90 Shore A in the photo-crosslinked state b) and a dimensionally stable carrier layer T c) a non-photocrosslinkable, non-photocrosslinkable and insoluble in the developer liquid, 0.1 to Have 6 mm thick intermediate layer Z, the intermediate layer Z essentially made of an elastomeric polymer and the hardness of the intermediate layer Z is in the hardness range of 15 to 70 Shore A and 20 to 50 Shore A. is less than the hardness of layer A in the photo-crosslinkable state. Badische Anilin- & Soda-Fabrik AG 403831/0 * ^ 3