Light-sensitive photopolymerisable printing plate.

The invention relates to a photosensitive, photopolymerizable printing plate which is suitable for the production of printing forms and which bears at least one intermediate layer on a dimensionally stable support and thereon a relief-forming photosensitive, photopolymerizable layer which essentially consists of a mixture of polymeric binder, at least one ethylenically unsaturated polymerizable compound, Photoinitiator and an inhibitor against thermal polymerization, and a method for producing such photosensitive printing plates.

Light-sensitive multilayer materials which have special adhesive layers between the support layer and the relief-forming light-sensitive layer are already known. For example, it is known from DE-A-22 02 357 to firmly anchor photopolymeric relief layers for printing forms by means of special adhesive layers on the support layers, with the support, for example, after coating the steel or aluminum sheets, with a primer lacquer layer (HG) for improved adhesion with the relief-forming light-sensitive layer, an adhesive layer HO is produced by layered application and drying or baking of a lacquer (OL) which contains a hardenable mixture of a binder which with the polymeric binder of the relief-forming layer is compatible. For branding or However, hardening of the adhesive layers HO requires the use of high temperatures, which on the one hand means a high energy expenditure with correspondingly high manufacturing costs, and on the other hand does not allow the use of some carrier materials since they do not survive the heat treatment without severely impairing their properties. This applies, for example, to the production of photopolymer printing plates with polyester films as carrier layers. Although it is known to lower the curing temperature of curable formaldehyde resins by adding acids as catalysts, because of their short pot life, such catalyzed resins are not suitable for producing uniform coatings and uniform, thin adhesive layers.

DE-A-30 45 515 discloses a light-sensitive multilayer material, that between a support layer (T) provided with a primer lacquer layer (HG) and a light-sensitive layer (R) with a photoinitiator-containing mixture of at least one binder and at least one ethylenically unsaturated compound compatible therewith one adhesive layer HO adjacent to the light-sensitive layer R with a hardened one Mixture of 65 to 98% by weight of one compatible with the binder of layer R and the condensate (AZ) Binder (A1) and 2 to 35% by weight of a melamine-formaldehyde condensate containing 1 to 5 melamine units and curable at 60 to 120 ° C without acid catalysis with a degree of methylolation of the melamine of 40 to 100%, 10 to 60% of the Methylol groups are etherified with alcohol.

From EP-A-00 36 301 is a photosensitive polyamide resin mixture of alcohol-soluble polyamide, a non-polymeric compound which has both vinyl and epoxy groups in one and the same molecule and can react with the polymeric binder to form copolymerizable polymers and a polyfunctional vinyl monomer With -O-CH₂-<img file="EP0333012A2_D0001.tif" />-CH₂-O-CO-CR = CH₂ groupings, including phenylglycidyl ether acrylate as a softening component, combined with polyfunctional acrylates, in photopolymerizable printing plates which contain alcohol-soluble modified polyamide as a polymeric binder. It is used here as a softening component in the relief layer.

The object of the present invention is to show photosensitive, photopolymerizable printing plates which have both improved adhesion of the relief layer on the support material and a shorter minimum exposure time in the production of the printing forms from these printing plates.

Surprisingly, this object can be achieved very advantageously by using intermediate layers which contain or consist of certain arylglycidyl ether (meth) acrylates in an at least partially polymerized state.

The present invention relates to a light-sensitive, photopolymerizable printing plate which is suitable for the production of printing forms and which bears at least one intermediate layer on a dimensionally stable support and thereon a relief-forming light-sensitive layer which essentially consists of a mixture of polymeric binder and at least one ethylenically unsaturated polymerizable compound Photoinitiator and thermal polymerization inhibitor, which is characterized in that at least one intermediate layer is a compound of the general formula (I)<chemistry id="chem0001" num="0001"><img file="EP0333012A2_D0002.tif" /></chemistry> wherein R¹ is hydrogen or an alkyl radical having 1 to 10 carbon atoms, R² represents hydrogen or a methyl radical, and X for -C₂H₄-, - (CH₂-CH₂-O)_n-C₂H₄-, - (CHCH₃-CH₂-O)_n-CHCH₃-CH₂-,<chemistry id="chem0002" num="0002"><img file="EP0333012A2_D0003.tif" /></chemistry> and n = 1 to 8, in the at least partially polymerized state.

There may be a thin layer of a conventional adhesion promoter on the dimensionally stable support as the first intermediate layer and a second intermediate layer thereon, which contains a compound of the general formula (I) in a mixture with polymeric binder in the at least partially polymerized state, or an intermediate layer may consist of one Compound of general formula (I) exist in the at least partially polymerized state.

An advantageous embodiment of the invention consists in that at least one intermediate layer consists of a mixture of a compound of general formula (I) with a polymeric binder compatible therewith, the compound of general formula (I) being in at least partially polymerized state and as a polymeric binder , in particular polyvinyl alcohol, a derivative of polyvinyl alcohol, a polyamide or an ethylene / (meth) acrylic acid ester / (meth) acrylic acid copolymer is used.

The light-sensitive layer of the printing plate according to the invention can be covered in the usual way with a removable protective film.

The present invention also relates to a process for producing a photosensitive photopolymerizable printing plate, a solution which comprises a compound of the general formula (I) being applied as an intermediate layer to the dimensionally stable support, after the solvent has been largely removed, the photosensitive layer forming the relief is applied and then the layer structure obtained is exposed over the entire area, that the intermediate layer cures substantially without the polymerized compounds contained in the layer forming the relief polymerizing substantially.

The photosensitive, photopolymerizable printing plates according to the invention, or those produced by the process according to the invention, are distinguished by improved adhesion, a substantially improved resistance to the developer and a higher print run resistance.

The details of the structural components of the printing plates according to the invention and the materials to be used for the method according to the invention are as follows.

As compounds of the general formula (I) to be used according to the invention<chemistry id="chem0003" num="0003"><img file="EP0333012A2_D0004.tif" /></chemistry> are those in which R¹ is hydrogen, an alkyl radical having 1 to 10 carbon atoms or an aryl radical having 6 to 10 carbon atoms, R² represents hydrogen or a methyl radical, and X for -C₂H₄-, - (CH₂-CH₂-O)_n-C₂H₄-, - (CHCH₃-CH₂-O)_n-CHCH₃-CH₂-,<chemistry id="chem0004" num="0004"><img file="EP0333012A2_D0005.tif" /></chemistry> and n = 1 to 8.

In addition to hydrogen, the R 1 is, for example, an alkyl radical having 1 to 10 carbon atoms, such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, hexyl, n- Octyl, isooctyl or an aryl radical, such as a phenyl or naphthyl radical in question.

Preferred compounds of the formula (I) are those in which R 1 is hydrogen or methyl and X is the rest -CH₂-<img file="EP0333012A2_D0006.tif" />-CH₂- stand.

Suitable dimensionally stable supports are those which are customarily used for the production of photopolymer printing forms, for example steel sheets, aluminum sheets, plastic films, such as, for example, those made of polyesters, such as polyethylene terephthalate, polycarbonate, polyvinyl chloride or polyamide.

It may be advantageous to first provide the dimensionally stable support with a primer coat. Various primer layers can be used for this, provided they provide sufficient adhesion between the base material and the intermediate or adhesive layer to be applied to it, and, if necessary, can be dried or baked at temperatures at which the properties of the base material are not thermally damaged.

Pigmented and unpigmented primer coats, which have been produced from reactive lacquers and have been found to be very suitable, are those containing polyisocyanates and hydroxyl-containing oligomers and polymers such as hydroxyl-containing epoxy resins and / or hydroxyl-containing polyesters (preferably with molecular weights of 20,000 to 30,000) or mixtures thereof with other polyols, for example 1,4-butanediol. For the preparation of the primer coat, for example the ready-mixed primer with a solids content of 20-70% by weight is applied to the dimensionally stable support in such a thickness that a dry layer thickness of 3-100 µm, preferably 5-20 µm, is achieved. The coating can be carried out using one of the usual techniques such as brushing, spraying, dipping, pouring or roller application. The coating can then be dried at temperatures between 50 and 300 ° C, depending on the carrier material. be branded.

To produce the intermediate or adhesive layer on the dimensionally stable support or the dimensionally stable support provided with a primer coat, a compound of general formula (I) or a mixture thereof with a polymeric binder compatible therewith and optionally further additives, advantageously in the form of their solution in such Layer thicknesses applied that a dry film thickness of 3 to 25 microns, especially 5 to 15 microns. This coating can also be done by brushing, spraying, dipping, pouring or roller application.

Possible polymeric binders which can optionally be used in a mixture with a compound of the general formula (I) are: water-soluble copolymers or derivatives of polyvinyl alcohol, for example elastomeric graft polymers which are soluble or dispersible in aqueous solvents and which are obtained by polymerizing vinyl esters in the presence of polyalkylene oxides and an initiator of free-radical polymerization, Saponification or partial saponification of the resulting graft copolymer and optionally subsequent esterification or transesterification of vinyl alcohol units of the saponified or partially saponified graft copolymer are prepared and essentially consist of structural units of the composition<chemistry id="chem0005" num="0005"><img file="EP0333012A2_D0007.tif" /></chemistry> where Z: grafted on side branches with structural units<chemistry id="chem0006" num="0006"><img file="EP0333012A2_D0008.tif" /></chemistry> R¹ is hydrogen and / or alkyl radicals with 1 or 2 carbon atoms, R² represents alkyl and / or alkenyl radicals, optionally with carboxyl substituents, and x&gt; y, n&gt; m, m at least 2, n + m = 20-2000, and<maths id="math0001" num=""><img file="EP0333012A2_D0009.tif" /></maths> as described in EP-A-224 164.

Likewise suitable are polyvinyl alcohols partially esterified with methacrylic acid, as described in EP-A-220 507 or DE-A-33 22 993, and partially acetalized polyvinyl alcohol. Such suitable polyvinyl alcohols generally have molecular weights<o ostyle="single">M</o>_n between about 4,000 and 100,000, preferably 10,000 and 70,000; Polyamides, such as Copolyamides as described in DE-A-15 22 463, for example copolyamides from approximately equal parts of hexamethylene diammonium adipate, 4,4'-diammonium di-cyclohexyl methane adipate and ε-caprolactam, the K values ​​(according to Fikentscher, Cellulosechemie 13 (1932) 58) from 55 to 75; copolymers containing carboxyl groups, in particular such acrylate resins, for example those based on copolymers of (meth) acrylic acid esters with (meth) acrylic acid the acid numbers between 30 and 100, molecular weights (<o ostyle="single">M</o>_w) from about 10,000 to about 100,000 and glass transition temperatures between 30 and 80 ° C, for example commercial products such as Carboset®resin XL 44 from BF Goodrich; also ethylene / (meth) acrylic acid ester / (meth) acrylic acid copolymers, for example those with MFI (melt flow index; measured in g / 10 minutes at 190 ° C. and 2.16 kg load) values ​​between 50 and 400 and acid numbers between 50 and 200 mg KOH / g.

The polymeric binders can generally be present in the intermediate layers in amounts of 0 to 90, preferably 35 to 80% by weight, based on the total weight of the solvent-free intermediate layer.

Other constituents for the production of the intermediate or adhesive layer are photoinitiators or photoinitiator systems, inhibitors against thermal polymerization, solvents, aqueous or organic solvent mixtures and additives for achieving special effects, for example glyoxal or glutardialdehyde.

Photoinitiators are generally present in amounts of 0.01 to 10 and in particular 0.01 to 3% by weight, based on the total amount of the intermediate layer. Compounds suitable as photoinitiators are those which are capable of forming free radicals when exposed to actinic light and which trigger rapid photopolymerization in the layer. Examples of suitable photoinitiators are acyloins and acyloin ethers, aromatic diketones and their derivatives and polynuclear quinones. Benzoin and α-hydroxymethylbenzoin and especially their alkyl ethers with 1 to 8 carbon atoms such as benzoin isopropyl ether, α-hydroxymethyl benzoin methyl ether or benzoin methyl ether, benzil monoketals such as benzil dimethyl ketal, benzil methyl ethyl ketal, benzil methyl benzyl ketal are very suitable , Benzil-neopentyl ketal or diarylphosphine oxides, as described in DE-OS 29 09 992, preferably 2,6-dimethoxybenzoyldiphenylphosphine oxide and in particular 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. Preferred are type and quantity of photoinitiators that they require only short minimum exposure times, preferably not more than a few minutes, to trigger the photopolymerization when exposed imagewise with actinic light, in particular UV light.

The photopolymerizable intermediate layers according to the invention also expediently also contain inhibitors against thermal polymerization, such as hydroquinone, p-methoxyphenol, dinitrobenzene, p-quinone, methylene blue, β-naphthol, N-nitrosamines such as N-nitrosodiphenylamine, phenothiazine, phosphorous acid esters such as triphenylphosphite or the salzephosphite especially the alkali and aluminum salts of N-nitroso-cyclohexyl-hydroxylamine. The inhibitors are generally added to the photopolymerizable mixtures of the relief-forming polymerizable layer in an amount of 0.001 to 3% by weight and in particular in an amount of 0.003 to 1% by weight, based on the total amount of the polymerizable layer.

In a known manner, other conventional additives can of course also be used, such as plasticizers, saturated low-molecular compounds with amide or alcohol groups, waxes, soluble dyes, pigments, etc.

After the intermediate layer has been applied to the dimensionally stable support, which is optionally provided with a primer lacquer layer, after removal of any solvent present, by evaporation or drying, the entire area of ​​the intermediate layer is exposed to actinic light to at least partially, preferably, the compound of the general formula (I) predominantly to convert to the polymeric state.

A further possibility is to apply the photopolymerizable relief-forming layer to the intermediate layer immediately after application of the intermediate layer and removal of the solvent and then to expose the layer structure obtained over the entire area so long that the ethylenically unsaturated polymerizable compounds contained in the relief-forming layer have not yet or not in polymerize to a significant extent, however, the intermediate layer is at least partially converted into the polymerized state. With transparent supports, the exposure can also take place from the back.

A further possibility for converting the intermediate layer into the polymerized state consists in a thermally triggered polymerization, in which case typical initiators of the radical polymerization, for example organic peroxides, such as benzoyl peroxide, or labile azo compounds, such as azodiisobutyronitrile, may be present. This method is particularly suitable for metallic substrates that can withstand the required high temperatures (usually above 100 ° C) without loss of dimensional stability.

The relief-forming layer is generally advantageously laminated onto the intermediate or adhesive layer, the lamination solvent being determined by the polymeric binders in the relief-forming layer. The lamination can also be carried out without a solvent, for example as hot lamination.

Suitable polymeric binders for the photosensitive relief-forming layer are virtually all polymer binders specified in the literature for the production of photopolymer printing plates or relief forms. Mention may be made of polyamides and particularly alcohol-soluble copolyamides, as described in French Pat. No. 1,520,856, cellulose derivatives, in particular cellulose derivatives which can be washed out with alkaline water, vinyl alcohol polymers and polymers and copolymers of vinyl esters of aliphatic monocarboxylic acids having 1 to 4 carbon atoms, such as of vinyl acetate, with different degrees of saponification, homo- and copolymers of vinyl pyrrolidone, polyurethanes, polyether urethanes, polyester urethanes, polyester resins, Acrylic and methacrylic acid ester copolymers such as copolymers of methyl methacrylate with acrylic acid, methacrylic acid, acrylamide and / or hydroxyalkyl (meth) acrylates, and elastomeric diene polymers and copolymers such as block copolymers from butadiene and / or isoprene homopolymer blocks and polymer blocks from styrene or α -Methylstyrene and ethylene elastomers, as described for example in DE-A-3 540 950. They are usually present in the relief-forming layers in a mixture with one or more photopolymerizable mono- or poly-ethylenically unsaturated compounds compatible with them, the type and amount of which depend on the type of polymer binder and the type of intended use of the light-sensitive multilayer materials.

The quantitative ratio in the mixture of monomers and polymeric binder can be varied widely, it is preferably 10 to 55 and in particular 25 to 50% by weight of monomers and 45 to 90 and in particular 50 to 75% by weight of polymeric binder on the sum of the amounts of monomers and polymeric binders. The preferred relief-forming layers are solid at room temperature and generally have thicknesses of 200 to 1200 µm. The content of known photoinitiators which are able to form free radicals when exposed to actinic light is generally from 0.01 to 15% by weight of the total amount of the relief-forming layer.

Examples of particularly preferred polymeric binders for the relief-forming layer are Polyvinyl alcohols with a residual acetate content of 10 to 30 mol% and an average molecular weight <o ostyle="single">M</o>_w from about 10,000 to about 30,000, internally plasticized polyvinyl alcohols based on polyethylene oxide-polyvinyl alcohol graft copolymers, as already mentioned for the production of the intermediate layer (cf. EP-A-224 164), alcohol-soluble mixed polyamides, e.g. those made from approximately equal parts of hexamethylene diammonium adipate, 4,4'-diammonium dicyclohexyl methane adipate and ε-caprolactam, 80 mol% of partially saponified and about 3 mol% of the free OH group esterified with methacrylic acid polyvinyl alcohols (for example prepared according to DE-A-33 22 993), Copolymers, especially ter- or quaterpolymers of ethylene, (meth) acrylic acid and esters of acrylic acid, such as n-butyl acrylate (for example, manufactured according to DE-A-35 40 950).

Examples of olefinically unsaturated photopolymerizable compounds to be used in the relief-forming layer are compounds with at least one photopolymerizable olefinically unsaturated double bond. The known monomers, oligomers and unsaturated polymers used for the production of relief molds and photopolymer high, low and offset printing plates can be used, the type of which depends on the intended use of the mixtures, but also on the type of the other mixture components. Monomers with two or more olefinically unsaturated photopolymerizable double bonds are suitable alone or in a mixture with monomers with only one olefinically unsaturated photopolymerizable double bond. Polymers with several side or terminal olefinically unsaturated double bonds can also be used instead of or in a mixture with the monomers. Examples of suitable monomers are the di- and polyacrylates and methacrylates, as can be prepared by esterifying diols or polyols with acrylic acid or methacrylic acid; such as the di- and tri (meth) acrylates of ethylene glycol, diethylene glycol, triethylene glycol or polyethylene glycols with a molecular weight of up to about 500, 1,2-propanediol, 1,3-propanediol, neopentylglycol, (2,2-dimethylpropanediol), 1.4 -Butanediol, 1,1,1-trimethylolpropane, glycerol or pentaerythritol, furthermore the monoacrylates and monomethacrylates of such diols and polyols, such as, for example Ethylene glycol, di-, tri- or tetraethylene glycol monoacrylate, monomers with two or more olefinically unsaturated bonds which contain urethane groups and / or amide groups, such as the low molecular weight compounds prepared from aliphatic diols of the type mentioned above, organic diisocyanates and hydroxyalkyl (meth) acrylates . Also mentioned are acrylic acid, methacrylic acid and their derivatives such as (meth) acrylamide, N-hydroxymethyl (meth) acrylamide or the (meth) acrylates of monoalcohols with 1 to 6 carbon atoms.

Suitable monomers are also reaction products of glycidyl ethers with acrylic acid or methacrylic acid, such as reaction products of bisphenol A diglycidyl ether or butanediol diglycidyl ether with acrylic acid or methacrylic acid.

Suitable photoinitiators and inhibitors against thermal polymerization for the relief-forming layer are those which have already been mentioned above for the production of the intermediate layer, with the same quantitative data also applying here in each case (ie 0.01 to 10, preferably 0.01 to 3% by weight) % Photoinitiator and 0.001 to 3, preferably 0.003 to 1% by weight of inhibitor, in each case based on the total amount of the polymerizable layer).

Possible plasticizers to be used in the relief-forming layer are the customary ones, for example benzenesulfonic acid-Nn-butylamide, benzenesulfonamide, or polyhydric alcohols, such as glycerol or polyethers containing OH groups, amino alcohols, for example triethanolamine or commercially available phthalic acid esters, in amounts of 0 to 30 % By weight, based on the dry weight of the relief-forming layer, can be used.

The photopolymerizable relief-forming layer can also contain a regulator system, as described for example in EP-A-114 341.

These are mixtures of certain dyes (1) with mild reducing agents (2) for the respective dye (1) used (cf. also EP-A-0 114 341). The mixture (1) + (2) should not cause any noticeable photopolymerization in the layer of the photopolymerizable mixture in the imagewise exposure to actinic light, which can be determined with a few experiments. For example, If the exposure time for layers of the photopolymerizable mixture containing the photoinitiator according to the invention, preferably essentially solvent-free, is X hours or minutes, then the corresponding layer which does not contain the photoinitiator should advantageously also be used ten times the exposure time during subsequent development of the relief shape by washing have no noticeable proportions of photopolymerized layer, generally less than 20% by weight of the exposed amounts of monomers should be photopolymerized.

Suitable dyes (1) for the photopolymerizable mixtures of the relief-forming layer are, in particular, those from the series of phenoxazine dyes, such as, for example Capri Blue GN (CI 51000), Zapo Real Blue 3 G (CI 51005), Gallo Blue E (CI 51040), Real New Blue 3 R (CI 51175), Nile Blue A (CI 51180), Real Green M (CI 51210), Real Black L (CI 51215) , as well as rhodanil blue, the salt or amide from rhodamine B (Basic Violet 10, CI 45170) and Nile blue (Basic Blue 12, CI 51180), compounds from the series of phenazinium dyes, such as neutral red (CI 50040), neutral violet (CI 50030), azine scarlet G (CI 50045), rhodulin heliotrope 3 B (CI 50055), neutral blue C (CI 50150), azine green GB (CI 50155), safranin B (CI 50200), indamine blue B (CI 50204), rhodulin red G (CI 50215), rhodulin blue GG extra (CI 50220), indazine GB (CI 50221), safranin T (CI 50240), mauvein (CI 50245 ), Naphthyl red (CI 50370) and nigroin black T (CI 50415), acridinium dyes such as acriflavin (CI 46000), acridine orange (CI 46005), acridine scarlet J (CI 46015), acridine yellow G (CI 46025), aurazine G (CI 46030), diamond phosphine GG (CI 46035), phosphine E ( CI 46045), flaveosin (CI 46060), benzoflavin (CI 46065) and Rheonin A (CI 46075), also phenothiazinium dyes, such as methylene blue or thionine. (Isobutylthio) anthraquinone is also suitable as a dye (1).

The choice of the dye (1) used in the photopolymerizable mixture is primarily determined by the aesthetic impression. For example, a visual assessment of the printing plates is particularly easy with the compounds neutral red (CI 50040), safranin T (CI 50240) and rhodanil blue, which are preferably used in the photopolymerizable mixture.

The light-sensitive relief-forming layers can therefore, in combination with the dye (1), contain a sufficient amount of a reducing agent (2) for the dye (1) which does not reduce the dye (1) used in the absence of actinic light, when exposed to light However, dye in the excited electron state can reduce, especially to semiquinone. Examples of such mild reducing agents are ascorbic acid, anethole, thiourea, diethylallylthiourea, hydroxylamine derivatives, especially N-allylthiourea and preferably salts of N-nitrosocyclohexyl-hydroxylamine, especially the potassium and aluminum salts. The latter are also known as inhibitors against thermal polymerization in photopolymerizable mixtures. The amount of the reducing agent added is generally about 0.005 to 5 and in particular 0.01 to 1% by weight, based on the total amount of the photopolymerizable layer, but should not be less than the reduction equivalent of the amount of the dye (1) used. In many cases, the addition of 3 to 10 times the amount of dye (1) used has proven successful.

The photopolymerizable printing plates are generally produced by applying a homogeneous mixture of the components of the photopolymerizable relief layer, optionally with the addition of solvents or solvent mixtures, to the dimensionally stable support provided with at least one adhesive (= intermediate) layer.

The homogeneous photopolymerizable mixture of the relief-forming layer can be produced in the usual way by mixing the individual components in conventional mixing units, for example in kneaders, extruders or stirred kettles. The homogeneous mixture is then generally applied in a thickness of 25 to 6000, preferably 200 to 1000 .mu.m to the dimensionally stable support provided with the adhesive layer or with one or more intermediate layers.

It may also be advantageous to apply a cover or protective layer to the photopolymerizable relief-forming layer, for example a thin layer of polymers soluble in the developer medium, such as polyvinyl alcohol or polyvinyl alcohol-polyethylene oxide copolymers.

The photopolymerizable printing plates according to the invention can be processed in a known manner to give relief forms, in particular printing forms. For this purpose, the layer of the photosensitive material is generally exposed imagewise with actinic light from light sources, such as UV fluorescent tubes, high, medium or low pressure mercury lamps, fluorescent tubes, etc., the emitted wavelength preferably being between 300 and 420 nm. The unexposed and uncrosslinked layer portions can be removed by spraying, washing, brushing, etc. with aqueous solvents or water. It is an advantage of the printing plates according to the invention that they allow the unexposed layer parts to be washed out with pure water without the addition of organic solvents. Developed relief and printing forms are expediently dried at temperatures of up to 120 ° C. and, if necessary, after-exposed simultaneously or thereafter with actinic light.

The printing forms produced from recording materials according to the invention are particularly suitable for direct and indirect letterpress printing, for example for flexographic printing, newspaper flexographic printing and similar types of printing.

The printing plates according to the invention, which contain a compound of the general formula (I), in particular phenylglycidyl ether (meth) acrylate as a photopolymerizable ethylenically unsaturated compound in the intermediate or adhesive layer, can be produced very advantageously and processed into printing forms which have a significantly improved adhesion of the Relief layer on the carrier material and a significantly reduced minimum exposure time in the manufacture of the printing forms.

The invention is illustrated by the following examples. Unless stated otherwise, the parts and percentages therein relate to the weight. Parts by volume behave in parts like liters to kilograms.

example 1

a) Production of the relief-forming layer:

50 Parts of an internally plasticized polyvinyl alcohol based on a polyethylene oxide-polyvinyl alcohol graft copolymer (viscosity of the 4% solution in water at 25 ° C. 4 mPas; e.g. Mowiol 04-M1 from Hoechst AG), 50 parts of phenylglycidyl ether acrylate, 1.2 parts of benzil dimethyl ketal, 0.5 part of the potassium salt of N-nitrosocyclohexylhydroxylamine and 0.05 part of Safranin T (CI 50240) are dissolved in 50 parts of water and 50 parts of methanol by stirring at 60 ° C. The solution thus obtained is poured onto a polyester film and scraped off in such a way that, after drying for up to 100 ° C., a layer of 0.5 mm thickness is formed.

b) Production of the intermediate or adhesive layer:

Phenylglycidyl ether acrylate, which contains 0.5% of the potassium salt of N-nitrosocyclohexylhydroxylamine and 2% benzil dimethyl ketal, is poured onto a 0.25 mm thick polyester film etched with trichloroacetic acid in such a way that after doctoring and exposure for 2 minutes with UV fluorescent tubes ( or: with actinic light) under a nitrogen atmosphere a layer of 0.02 mm thickness and non-sticky surface is created.

The relief-forming layer obtained under a) is laminated using the mixture prepared in this way using a mixture of ethanol and water (1: 1) and the raw plate obtained is stored for a few days.

After removing the protective film, a cliché is made from it in the usual way with very good adhesion of the relief parts to the carrier. Adhesion cannot be measured using the usual method, since the photopolymeric relief layer tears before the adhesion limit is reached.

Example 2

a) Production of the relief-forming layer:

50 Parts of a commercially available alcohol-soluble mixed polyamide from approximately equal parts of hexamethylene diammonium adipate, 4,4'-diammonium dicyclohexyl methane adipate and ε-caprolactam with a K value (according to Fickentscher) of 68 (e.g. ®Ultramid 1C from BASF AG) are dissolved together with 25 parts of phenylglycidyl ether acrylate, 25 parts of trimethylolpropane triacrylate, 0.3 part of the potassium salt of N-nitrosocyclohexylhydroxylamine and 2 parts of benzil dimethyl ketal in 90 parts of methanol and 10 parts of water and the solution as described in Example 1 , processed into a photopolymerizable relief layer.

b) Production of the intermediate or adhesive layer:

Phenylglycidyl ether acrylate, the 5% of a partially acetalized polyvinyl alcohol (containing about 20% by weight of vinyl alcohol, about 1% by weight of vinyl acetate and 80% by weight of vinyl butyral units) is placed on a 0.25 mm thick polyester film etched with trichloroacetic acid (according to Fikentscher, Cellulose Chem. 13, 58 (1932)) 44, 0.5% of the potassium salt of nitrosocyclohexylhydroxylamine and 2% benzil dimethyl ketal dissolved, poured, the casting layer pre-exposed for 1 minute with actinic light, laminated with a 0.05 mm thick polyethylene film and by exposure for 2 minutes hardened actinic light.

This, after peeling off the polyethylene film, is laminated with the relief layer using a mixture of ethanol and water (1: 1) and the raw plate obtained is stored for a few days.

The printing plate produced therefrom after the protective film has been removed is characterized by excellent adhesion of the relief layer to the support. When trying to detach the relief layer from the carrier film, the polyester film splices.

Example 3

Carrier sheets made of 1.05 mm thick aluminum sheet and 0.24 mm thick steel sheet were coated with the two-layer adhesive varnish described below in order to permanently anchor the relief layers of photopolymerizable high-pressure plates with binders made of polyamide and polyvinyl alcohol on the metal supports.

3.1 Production of the primer coat:

243 Parts of a commercial epoxy resin (made from bisphenol A and epichlorohydrin) with an epoxy equivalent of approx. 0.02 (based on 100 g of resin), a molecular weight of approx. 5,500 and an OH content of 5.9%, and 150 parts of finely divided Rutile, 6 parts of finely divided chrome oxide green, 90 parts of talc and 20 parts of a commercially available paste of a bentonite modified with organic ammonium bases (for example Bentone® from Fa. National Lead Co.) are rubbed with a mixture of butyl acetate, ethyl glycol acetate and xylene (mixing ratio 1/1/1) in a ball mill for 2 days.

346 parts of a commercially available reaction product composed of 1 mol of 1,1,1-trimethylolpropane and 3 mols of tolylene diisocyanate as polyisocyanate in the form of the 75% strength solution in xylene / ethyl glycol acetate (mixing ratio 1: 1) are mixed into the resulting base lacquer.

The resulting primer coat is cast in layers on aluminum sheet or steel sheet. The lacquer layer is flashed off at room temperature for 1 hour and then baked in a convection oven at 180 ° C for 5 minutes. The dry film thickness of the resulting primer coat is approximately 18 µm.

3.2 Production of the second adhesive layer or intermediate layer:

150 Parts of a copolyamide from approximately equal parts of hexamethylene diammonium adipate, 4,4'-diammonium di-cyclohexyl methane adipate and ε-caprolactam with a K value (according to Fikentscher, Cellulosechemie 13 (1932) 58) of 67, 100 parts of phenylglycidyl ether acrylate and 5 parts 2,4,6-Trimethylbenzoyldiphenylphosphinoxid are introduced in methanol / water (weight ratio 9/1) at 60 ° C with stirring. In this way, a 10% solution is produced, which is applied with a coater to the carrier sheets provided with the primer lacquer layer in such a way that a dry film thickness of the intermediate layer of approximately 0.005 mm results. After flashing off at room temperature for 30 minutes, bake in a continuous nozzle dryer at 150 ° C. for 1.5 minutes.

3.3 Applying the light-sensitive relief-forming layer:

A 65% solution of a mixture of 60% of the copolyamide specified under 3.2, 25% of the diether from 1 mole of ethylene glycol and 2 moles of N-hydroxymethyl-acrylamide, 13.5% of benzenesulfonamide and 1.5% of benzointetrahydropyranyl ether are 0.3% of the Potassium salt of N-nitrosocyclohexylhydroxylamine, 0.01% of a black dye (Color Index No. 12195) and 0.03% 2-butylthio-2-anthraquinone added. The solution is poured onto the aluminum sheet provided with the adhesive layers according to 3.1 and 3.2 in such a way that after drying at about 70 ° C. a light-sensitive relief-forming layer with a thickness of 200 μm is formed.

3.4 Testing the photopolymerizable printing plates

The printing plates produced according to Examples 3.1 to 3.3 are each exposed for 1, 2, 3 ... to 10 minutes in close contact with a film negative with a 3% screen tone value of the screen line width 30 lines per centimeter. A commercially available printing platesetter with superactinic UV fluorescent tubes is used as the light source. The exposure time is determined, which is sufficient to reproduce the grid fields without errors with a washout time extended by a factor of 2 (100% overwashing). This minimum exposure time when overwashed is the better the more suitable the adhesive coating system is with a constant relief layer formulation.

The printing plates manufactured according to 3.3 require a minimum exposure time of 3.0 minutes with aluminum as well as with steel carrier sheet. The printing plate was washed out for 6 minutes at 30 ° C. in an ethanol / water mixture (87% ethanol and 13% water) in a commercially available spray washer at a spray pressure of 4 bar although the minimum washout time required was only 3.0 minutes.

Example 4

The procedure is as described in Example 3, but the intermediate layer (see 3.2) contains no photoinitiator. The test according to 3.4 shows the slightly worse minimum exposure time of 3.75 minutes.

Comparative experiment 1a

The procedure is as in Example 3, but the intermediate layer contains no phenylglycidyl ether acrylate and no photoinitiator. Checking the printing plates reveals a very poor minimum exposure time of more than 10 minutes.

Comparative experiment 1b

The procedure is as in Example 3, but instead of 100 parts of phenylglycidyl ether acrylate, the intermediate layer contains 65 parts of a curable phenolic resin (prepared by condensing 30 parts of phenol and 7.5 parts of bisphenol A with excess formaldehyde at 100 ° C. in the presence of dimethylethanolamine). The enamel layer is baked at 180 ° C and 5 minutes dwell time. The inspection of the printing plates shows the still insufficient minimum exposure time of 8 minutes.

Example 5

5.1 Production of a two-layer adhesive varnish

The primer coat is prepared as described in Example 3.1. In contrast to Example 3, 100 parts of 80 mol% partially saponified and 3 mol% methacrylated polyvinyl alcohol (production see DE-A-33 22 993) of the average molecular weight are used to produce the second adhesive layer (= intermediate layer)<o ostyle="single">M</o>_w = 17000. 110 parts of phenylglycidyl ether acrylate, 5 parts of photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 3 parts of 30% strength aqueous glyoxal solution in 60 ° C. warm water / n-propanol (75/25) mixture, dissolved with stirring, by a 14% ige (solids content) paint solution. Layer thickness and stoving are identical to the values ​​described in 3.2.

5.2 Production of the light-sensitive relief-forming layer:

A 65% solution of 60 parts to 80 mol% partially saponified and 3 mol% methacrylated polyvinyl alcohol (manufactured according to DE-A-33 22 993) of the average molecular weight <o ostyle="single">M</o>_w= 17000, 30 parts of the diether from 1 mol of ethylene glycol and 2 mol of N-hydroxymethylacrylamide, 7 parts of Nn-butylbenzenesulfonamide, 2 parts of benzil dimethyl ketal, 0.03 parts of safranin T (CI 50240), 0.03 parts of crystal violet (CI 42555) and 0 , 3 parts of the potassium salt of N-nitrosocyclohexylhydroxylamine was prepared by dissolving in a mixture of n-propanol / water (mixing ratio 25:75) of 60 ° C. By pouring onto the aluminum support plates described in 5.1 or Steel and drying to a residual solvent moisture of 6% gave photopolymerizable printing plate layers with a relief layer thickness of 0.2 mm.

5.4 Checking the pressure plates

The test is carried out exactly as described in Example 3.4. Instead of the ethanol / water detergent, tap water at room temperature is used. The normal washout time is 1.5 minutes. The washout time, extended by a factor of 2, is therefore 3 minutes. The test plates are produced with this washout time. The assessment criteria for the clichés are identical to those described in Example 3.4.

The printing plates produced according to Example 5.2 require a minimum exposure time of 2.0 minutes on both steel and aluminum carrier sheet. The printing plate was washed out in a spray washer at a spray pressure of 4.5 bar and room temperature for 3 minutes (= doubled normal washout time). Even under these unfavorable conditions, the minimum exposure time remains at 2.0 minutes. Even tripling the washout time to 4.5 minutes does not worsen the minimum exposure time. If the appropriate amount of cresyl glycidyl ether acrylate is used in the adhesive layer instead of the phenyl glycidyl ether acrylate, a minimum exposure time of 2.0 minutes is also obtained.

Comparative experiment 3a

The procedure is as in Example 5, but the adhesive layer (= intermediate layer) contains no phenylglycidyl ether acrylate and no photoinitiator. Checking the printing plates reveals a very poor minimum exposure time of more than 10 minutes.

Example 6

Printing plate support plates are produced as described in Examples 5.1 to 5.2. The layer thickness of the intermediate layer is 0.03 mm instead of 0.005 mm. In order not to polymerize this adhesive layer already thermally, it is dried in a jet dryer within 5 minutes in a forced-air drying cabinet instead of at 150 ° C. The crosslinking of this adhesive (= intermediate) layer is effected photochemically by exposure in a continuous tube imagesetter, which is equipped with superactinic fluorescent tubes as UV-A light source, with a dwell time of 60 seconds.

A 65% solution of 60 parts to 80 mol% partially saponified and 3 mol% methacrylated polyvinyl alcohol (according to DE-A-3 22 993) provides the average molecular weight <o ostyle="single">M</o>_w= 17,000, 30 parts of the diester of 1 mol of 1,4-butanediol diglycidyl ether and 2 mol of acrylic acid, 2 parts of benzil dimethyl ketal, 0.03 part of safranin T (CI 50240), and 0.3 part of the potassium salt of the N-nitrosocyclohexylhydroxylamine was dissolved produced in a mixture of n-propanol / water (mixing ratio 1/3) of 60 ° C. By pouring onto the aluminum support plates described in 5.1 or Steel and drying to a residual solvent moisture of 6% gave photopolymerizable printing plate layers with a relief layer thickness of 0.7 mm.

With the normal washout time of 6 minutes at 40 ° C and 4.0 bar spray pressure, these printing plates require a minimum exposure time of 5.0 minutes, which does not deteriorate noticeably even when the washout time is doubled.

Comparative experiment 4

The procedure is as in Example 6, but the intermediate layer contains no phenylglycidyl ether acrylate. Checking the printing plates reveals a very poor minimum exposure time of more than 10 minutes.

Example 7

Printing plate support plates are produced as described in Examples 5.1 to 5.2. The layer thickness of the intermediate layer is 0.01 mm instead of 0.005 mm. In order not to already thermally polymerize this intermediate layer, it is dried in a nozzle dryer instead of at 150 ° C. at 110 ° C. The crosslinking of this adhesive layer is only effected photochemically during the processing to form the cliché by the processing step of the full-surface pre-exposure.

To produce the printing plate, a 65% solution of 50 parts of an 80 mol% partially saponified polyvinyl alcohol of average molecular weight is used <o ostyle="single">M</o>_w= 17,000, 40 parts of hydroxyethyl methacrylate, 1 part of 1,3,5-trimethylbenzoyldiphenylphosphine oxide and 0.3 part of hydroquinone monomethyl ether by dissolving in n-propanol / water (mixing ratio 1/3) at 60 ° C. By pouring onto the support sheets made of aluminum or steel described in more detail under 5.1 and drying to a residual solvent moisture of 6%, photopolymerizable printing plate layers with a relief layer thickness of 0.5 mm were obtained.

With a normal washout time of 2.5 minutes at 40 ° C and 4.0 bar spray pressure and a full pre-exposure of 3.5 seconds, these printing plates require a minimum main exposure time of 1.5 minutes, which does not deteriorate noticeably even when the washout time is doubled.

Comparative experiment 5

The procedure is as in Example 7, but the intermediate layer contains no phenylglycidyl ether acrylate. Examination of the printing plates with a doubled washout time results in a minimum main exposure time of 6 minutes, whereby other picture elements, especially fine lines and dots, require even longer exposure times.

Example 8

8.1 Production of the primer coat

Carrier sheets made of 1.05 mm thick aluminum sheet and 0.24 mm thick steel sheet were first provided with a primer coat as described in Example 3.1.

8.2 Production of the intermediate layer

A 20% solution of a mixture consisting of 49 parts of an acrylate resin containing carboxyl groups SZ: 75; MG: 30,000; T_G: 42 ° C; eg Carboset resin XL 44 from BF Goodrich), 49 parts of phenylglycidyl ether acrylate and 2 parts of benzil dimethyl ketal poured into a layer. The applied lacquer layer was flashed off at room temperature for 1 hour and baked at 160 ° C. for 5 minutes. The resulting dry film thickness of the resulting adhesive layer was 10 μm.

8.3 Application of the light-sensitive relief-forming layer:

A photosensitive layer consisting of 80 parts of a terpolymer (from 60% ethylene, 20% acrylic acid and 20% n-butyl acrylate, melt flow index approx. 300), 15 parts of hexanediol diacrylate, 10 parts of benzenesulfonic acid butylamide, 2 parts of benzil dimethyl ketal and 0.4 parts Hydroquinone monomethyl ether is laminated onto the intermediate layer and the resulting multilayer material is stored for 3 days at room temperature.

8.4 Checking the multi-layer materials

The photosensitive layer was exposed imagewise and developed with 1% sodium carbonate solution. It was found that the applied intermediate layer had excellent adhesion to both the primer and the photopolymerized relief layer. It was not possible to remove parts of the relief created from the steel girder. Both the primary and secondary adhesion of the adhesive layer (= intermediate layer) were greater than the cohesion of the photopolymerized relief layer.

Example 9

The procedure was as in Example 8, except that instead of the carboxyl-containing acrylate resin used in the intermediate layer, the terpolymer described under 8.3 (ethylene / acrylic acid / n-butyl acrylate) was used. Here, too, it was found that the intermediate layer had excellent adhesion to the primer and to the photopolymerized relief layer. In this example, too, the primary and secondary liability proved to be greater than the cohesion of the relief layer.