EP1031413B1 - Radiation-sensitive recording material for the production of waterless offset printing plates - Google Patents

Description

The invention relates to a recording material digitally imageable with IR radiation with - in this order - an aluminum support, a primer layer, an infrared radiation absorbing layer and a silicone layer. It also relates to a method for producing a printing plate for waterless offset printing from the recording material.

Recording materials from which waterless offset printing plates can be produced are already known. For example, DE-B 25 12 038 (= CA 1 050 805) describes a negative working material with an ink-accepting carrier, a layer which contains laser energy-absorbing particles, nitrocellulose, a crosslinkable resin and a crosslinking agent, and an ink-repellent silicone layer. During laser irradiation, the absorbent layer in the irradiated areas is destroyed, so that the silicone layer above it loses its hold there and can be removed with an organic solvent together with the remnants of the absorbent layer. The developed plate is then heated to approximately 200 ° C. in order to harden the crosslinkable resin and in this way to improve the adhesion of the silicone layer in the non-irradiated areas. DE-B also mentions an insulating layer made of an oleophilic or ink-accepting resin, which can be arranged between a highly thermally conductive metallic carrier and the IR-absorbing layer. According to DE-B, the type of resin is not essential. Any oleophilic resins that are common in the field of planographic printing can be used. Phenol and cresol-formaldehyde resins, vinyl resins, alkyd resins, polyester resins, polyamides, polyvinyl acetate, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polystyrene and polyethylene are mentioned. The shelf life of the plate when printing without dampening solution as well as the The print run that can be achieved with this, however, is insufficient despite the thermal curing of the IR-absorbing layer.

EP-A 0 802 067 describes a recording material for the production of waterless offset printing plates which comprises a support, a heat-insulating and a heat-sensitive layer and an ink-repellent cover layer. The material is characterized in that the heat-insulating, the heat-sensitive layer and the laminate formed from both layers each have an initial modulus of elasticity of 5 to 100 kgf / mm ² and a 5% tensile stress (5% stress) of 0.05 to 5 kgf / mm ² (kgf = kg force = kp). For example, a degreased 0.24 mm thick aluminum foil is used as the carrier. The heat-insulating layer can be produced by applying a mixture of polyurethane resin, blocked isocyanate, epoxy-phenol-urea resin, dibutyltin diacetate, Victoria purple BOH naphthalenesulfonic acid in dimethylformamide and then drying. The weight of the insulating layer is then 5 g / m ² . A mixture of nitrocellulose, carbon black, polyurethane, modified epoxy resin, epoxy acrylate and diethylenetriamine in methyl isobutyl ketone can then be applied to the dried layer and then dried for 1 minute (layer weight: 2 g / m ² ). The top layer consists of an RTV-2 addition type silicone rubber.

EP-A 763 424 discloses a process for producing a waterless printing offset printing plate which uses a material which comprises a support, a layer which converts laser beams into heat and a layer which repels printing ink. A further layer can be arranged between the carrier and the layer that absorbs laser beams, which layer, for example, improves the acceptance of the printing ink. This layer consists in particular of organic polymers, in particular of acrylic, methacrylic, styrene or vinyl ester polymers, of polyester or polyurethane.

The recording material for waterless offset printing plates which can be digitally imaged with IR laser beams in accordance with EP-A 764 522 comprises a support, an IR-absorbing layer and an overlying silicone layer. A primer layer may also be present between the support and the IR-absorbing layer. It does not contain any IR-absorbing soot particles, but other pigments or dyes that make the image created by laser radiation stand out more clearly. In addition, it reduces the outflow of heat from the IR-absorbing layer into the support.

The recording material for waterless offset printing plates described in EP-A 755 781 comprises a thin metal layer which absorbs IR laser beams and is ablated in the process.

WO 97/00175 discloses a recording material for waterless printing offset plates which contains an oleophilic support, an IR radiation-absorbing, preferably oleophilic layer and a preferably oleophobic top layer which is ablated by IR radiation.

The object was therefore to provide a recording material which can be digitally imaged with IR radiation for the production of waterless offset printing plates and which, compared to the known material, has a considerably improved durability even after no special thermal treatment after the irradiation and permits a large print run. On the one hand, the non-irradiated areas of the IR radiation-sensitive layer should adhere so well to the support that they are not detached even during a development that is mechanically assisted, for example by brushing. On the other hand, the areas hit by the IR radiation should adhere as little as possible to the support so that they can be removed easily and quickly. An optimum must be found between these two requirements. The sensitivity of the recording material to radiation in the IR range should be as high as possible and a high thermal insulation should be achieved so that as little as possible of the imagewise acting IR radiation energy is released to the carrier.

The object was achieved by using a mixture of an unmodified epoxy resin with a further organic polymer and a crosslinker for the primer layer.

The present invention accordingly relates to a recording material which can be digitally imaged with IR radiation, with - in this order - a support, a primer layer, an IR-absorbing layer and a silicone layer, which is characterized in that the primer layer contains a mixture of an unmodified epoxy resin , another organic polymer which has functional groups, and a crosslinking agent which reacts with the unmodified epoxy resin and the functional groups of the organic polymer.

In addition to secondary hydroxyl groups and remaining epoxy groups, the unmodified epoxy resin has no further reactive groups, in particular no ester, acetal or carboxy groups. As a rule, it also contains no carbon chains with more than three aliphatic carbon atoms. A particularly suitable unmodified epoxy resin based on epichlorohydrin and bis-phenol-propane (= bisphenol-A) is available, for example, from Vianova Resins GmbH & Co. KG under the name ®Beckopox. The total proportion of the unmodified epoxy resins is generally 0.5 to 95.0% by weight, preferably 2.0 to 80.0% by weight, particularly preferably 5.0 to 70.0% by weight, in each case based on the Total weight of the non-volatile components of the base coat. The weight ratio of unmodified epoxy resins to the further organic polymers with functional groups is advantageously in the range from 1:36 to 89: 1, in particular in the range from 1: 8 to 8: 1.

The functional groups of the further organic polymer are preferably hydroxyl and / or carboxy groups. Unlike the unmodified epoxy resin, this polymer generally contains chains of more than 3, in particular more than 12, aliphatic carbon atoms. For example, it can be a vinyl polymer with a main chain consisting of many (ie 20 or more) aliphatic carbon atoms or a polymer which contains side or terminal aliphatic radicals with more than 8, in particular also more than 12 carbon atoms in a chain. Organic polymers which have particularly suitable functional groups are fatty acid-modified, oven- or air-drying epoxy resins, in particular epoxy resins based on bisphenol-A, available under the name ®Duroxyn from Vianova Resins GmbH & Co. KG, acetalized polyvinyl alcohols, especially polyvinyl butyrals (for example ®Mowital B from Clariant GmbH), or acrylic resins containing hydroxyl groups (for example ®Macrynal from Vianova GmbH & Co. KG). In general, the modification of the epoxy resins is achieved by esterification with a long-chain, saturated or unsaturated (C ₁₂ -C ₂₆ ) fatty acid or a mixture of such fatty acids. The proportion of fatty acid modification is generally 20 to 80% by weight, preferably 30 to 70% by weight, particularly preferably 40 to 60% by weight, in each case based on the total weight of the fatty acid-modified epoxy resin.

The carrier is generally made of metal or a metal alloy. A preferred carrier of this type is a degreased, bright-rolled plate or sheet made of aluminum or an aluminum alloy which has been pretreated in simple processes (for example by pickling or wet brushing). Aluminum supports pretreated electrochemically in complex processes are in no case required for the recording material according to the invention. However, chemical pretreatment, for example with silane coupling agents, is possible. The primer layer not only results in improved adhesion, but also a particularly high thermal insulation.

The primer layer permanently and firmly anchors the overlying IR radiation-sensitive layer on the metallic support. In a preferred embodiment, the primer layer further contains a hardener or crosslinker. These are generally polyfunctional, low molecular weight compounds that can react with the reactive groups, especially the hydroxyl groups, the unmodified epoxy resin and the organic polymer. Formaldehyde adducts derived from urea, melamine or benzoguanamine and completely or partially etherified formaldehyde-amine adducts are particularly suitable. These include in particular partially or completely etherified melamine-formaldehyde adducts with methanol, ethanol, propanol or butanol. These are available under the name ®Maprenal from Vianova Resins GmbH or under the name ®Cymel from Cytec. Polyisocyanates and aliphatic or aromatic polyamines are also suitable. The proportion of the crosslinking agent is advantageously 5 to 35% by weight, preferably 10 to 30% by weight, in each case based on the total weight of the nonvolatile constituents of the layer. The hardener or crosslinker can optionally also react with the functional group-containing organic polymer. The curing caused by crosslinking is usually carried out in the presence of organic acids, in particular phosphoric acid derivatives or para- toluenesulfonic acid. The proportion of acid is expediently 0.5 to 4% by weight, based on the total weight of the non-volatile constituents of the primer layer. In order to be able to apply the primer layer more uniformly, it preferably also contains finely divided pigments, in particular inorganic pigments such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ or TiO ₂ pigments. The average diameter of the pigment particles is generally less than 10 μm, preferably less than 1.0 μm. In a particularly preferred embodiment, the pigment particles are predispersed in the fatty acid-modified epoxy resin. Finally, the proportion of the pigments is generally 1 to 40% by weight, preferably 5 to 30% by weight, in each case based on the total weight of the non-volatile constituents of the primer layer. The Finally, the primer layer can also contain the usual additives which bring about a more uniform layer course (so-called leveling agent) or contribute to it, so that the layer can be applied more easily. Examples include silicone oils that are available under the name ®Edaplan, alongside surface-active agents and / or adhesion promoters. The proportion of the additives is generally not more than 10% by weight, preferably not more than 5% by weight, in each case based on the total weight of the non-volatile constituents of the primer layer. Crosslinkers, pigments and additives generally have a share of up to 50% by weight, based on the total weight of the layer. The weight of the primer layer is generally 0.5 to 10.0 g / m ² , preferably 1.0 to 5.0 g / m ² , particularly preferably 2.0 to 4.0 g / m ² .

The pigments or dyes optionally contained in the IR-absorbing layer particularly absorb laser beams with a wavelength in the infrared range (especially in the range from 700 to 1200 nm). Soot should also be counted among the pigments here. Suitable IR absorbers are mentioned in J. Fabian et al., Chem. Rev. 92 [1992] 1197. Also suitable are pigments which. Contain metals, metal oxides, metal sulfides, metal carbides or similar metal compounds. Finely divided metallic elements of III are preferred. to V. main group and the I., II. and IV. to VIII. subgroup of the periodic table, such as Mg, Al, Bi, Sn, In, Zn, Ti, Cr, Mo, W, Co, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zr or Te. Metal-phthalocyanine compounds, anthraquinones, polythiophenes, polyanilines, polyacetylenes, polyphenylenes, polyphenylene sulfides and polypyrroles are also suitable as IR-absorbing components. In order not to unnecessarily worsen the resolution, the absorbent pigment particles should have an average diameter of not more than 30 μm if possible. The proportion of the IR-absorbing component is generally 2 to 80% by weight, preferably 5 to 57% by weight, in each case based on the total weight of the nonvolatile constituents of the layer. The IR-absorbing layer also contains at least one polymeric, organic binder. Binders are particularly advantageous decompose by themselves when exposed to heat. These self-oxidizing binders include, in particular, nitrocellulose. In addition, non-self-oxidizing polymers can also be used, which decompose indirectly when thermally induced to form gaseous or volatile fission products. Examples include cellulose ethers and esters (such as ethyl cellulose and cellulose acetate), (meth) acrylate polymers and copolymers (such as poly (methyl methacrylate), poly (butyl acrylate), poly (2-hydroxyethyl methacrylate), lauryl acrylate / methacrylic acid - Copolymers), polystyrene, poly (methyl-styrene), vinyl chloride / vinyl acetate copolymers, vinylidene chloride / acrylonitrile copolymers, polyurethanes, polycarbonates, polysulfones, polyvinyl alcohol, polyvinyl pyrrolidone. The directly or indirectly thermally decomposable polymers are not always necessary, so that other film-forming polymers can also be used. This applies if the IR-absorbing component already forms sufficient volatile products when irradiated. Soot, for example, burns when IR laser beams hit it and accordingly supplies gaseous combustion products. They are used either in combination with the thermally decomposable materials or alone. The proportion of the binders is generally about 10 to 95% by weight, preferably 20 to 80% by weight, in each case based on the total weight of the nonvolatile constituents of the layer.

In addition, the layer can also contain compounds that crosslink the binder. The type of crosslinker depends on the chemical functionality of the binder (S. Paul, Crosslinking Chemistry of Surface Coatings in Comprehensive Polymer Science Volume 6, Chapter 6, page 149). Nitrocellulose can be crosslinked, for example, with a melamine or a di-, tri- or polyisocyanate and thus hardened. The proportion of the crosslinker or crosslinkers is generally 0 to 30% by weight, preferably 3 to 20% by weight, particularly preferably 5 to 15% by weight, in each case based on the total weight of the nonvolatile constituents of the layer.

The IR-absorbing layer can also contain compounds which decompose under the action of heat and / or IR rays or chemically induced and thereby form chemically active species (in particular acids), which in turn cleave or decompose the polymeric, organic binder cause. This in turn creates volatile fission or decomposition products. Binder that tert. -Butoxycarbonylgruppen contain, for example, provide CO ₂ and isobutene when acid acts on it. The layer can furthermore contain compounds which form low-molecular, gaseous or at least volatile fission products (Encycl. Polym. Sci. Eng., Vol. 2, page 434). Examples of such compounds are diazonium salts, azides, bicarbonates, and azobicarbonates. The IR-absorbing layer can also contain stabilizers to increase the shelf life, plasticizers, catalysts to initiate the crosslinking reaction, matting agents, additional dyes, surfactants, leveling agents or other auxiliaries to improve durability, processing or reprographic quality. The proportion of these additives is generally 0 to 50% by weight, preferably 5 to 30% by weight, in each case based on the weight of the nonvolatile constituents of the layer. The total weight of the IR-absorbing layer is generally 0.1 to 4.0 g / m ² , preferably 0.2 to 3.0 g / m ² , particularly preferably 0.5 to 1.5 g / m ² .

For the silicone layer on the IR-absorbing layer, basically any silicone rubber that is sufficiently ink-repellent is suitable to allow printing without fountain solution. According to the definition by Noll, "Chemistry and Technology of Silicones", Verlag Chemie, 1968, page 332, the term "silicone rubber" is understood to mean a high molecular weight, essentially linear diorganopolysiloxane. The term "silicone rubber" is used for the cross-linked or vulcanized products. In any case, a silicone rubber solution is applied to the radiation-sensitive layer, dried and crosslinked in the process. Suitable as a solvent for example isoparaffin mixtures (for example ®Isopar from Exxon) or ketones, such as butanone.

The silicone rubbers can be single or multi-component rubbers. Examples of this can be found in DE-A 23 50 211, 23 57 871 and 23 59 102. Condensation silicone rubbers, for example one-component silicone rubbers (RTV-1), are preferred. They are usually based on polydimethylsiloxanes which have hydrogen atoms, acetyl, oxime, alkoxy or amino groups or other functional groups at the ends. The methyl groups in the chain can be replaced by other alkyl groups, haloalkyl groups or unsubstituted or substituted aryl groups. The terminal functional groups are easily hydrolyzable and cure in the presence of moisture in a period of a few minutes to a few hours.

The multi-component silicone rubbers can be crosslinked by addition or condensation. The addition-crosslinkable types generally contain two different polysiloxanes. The one polysiloxane is present in a proportion of 70 to 99% by weight and has alkylene groups (especially: vinyl groups) which are bonded to silicon atoms in the main chain. The other is present in a proportion of 1 to 10% by weight. In it, hydrogen atoms are bonded directly to silicon atoms. The addition reaction then takes place in the presence of about 0.0005 to 0.002% by weight of a platinum catalyst at temperatures of more than 50 ° C. Multi-component silicone rubbers have the advantage that they cross-link very quickly at a higher temperature (approx. 100 ° C). The time in which they can be processed, the so-called "pot life", on the other hand, is often relatively short.

The mixtures which can be crosslinked by condensation contain diorganopolysiloxanes with reactive end groups, such as hydroxyl or acetoxy groups. These are crosslinked with silanes or oligosiloxanes in the presence of catalysts.

The crosslinkers have a proportion of 2 to 10% by weight, based on the total weight of the silicone layer. The catalysts have a proportion of 0.01 to 6% by weight, again based on the total weight of the silicone layer. These combinations also react relatively quickly and therefore have a limited pot life.

The silicone layer can also contain other components. These can be used for additional crosslinking, better adhesion, mechanical reinforcement or for coloring. The further components have a proportion of not more than 10% by weight, preferably not more than 5% by weight, in each case based on the total weight of the silicone layer.

A preferred mixture consists of hydroxy-terminated polydimethylsiloxanes, a silane crosslinking component (in particular a tetra- or trifunctional alkoxy, acetoxy, amido, amino, aminoxy, ketoxime or enoxysilane), a crosslinking catalyst (in particular an organotin or an organotitanium Compound) and optionally other components (in particular organopolysiloxane compounds with Si-H bonds, silanes with adhesion-improving properties, reaction retarders, fillers and / or dyes). The silane crosslinking components mentioned and the reactions occurring during the crosslinking are described by J. J. Lebrun and H. Porte in "Comprehensive Polymer Science", Vol. 5 [1989] 593-609.

After application as a layer, the silicone rubbers are crosslinked in a known manner by exposure to moisture or by themselves at room temperature or at elevated temperature to form a silicone rubber which is essentially insoluble in organic solvents. The weight of the finished silicone layer is generally 1.0 to 5.0, preferably from 1.2 to 3.5, particularly preferably 1.5 to 3.0 g / m ² .

In order to protect the recording material from mechanical and / or chemical influences during storage, a plastic film can be laminated onto the silicone layer. Polyethylene films are particularly suitable. The film is removed again before the imagewise irradiation.

The recording material according to the invention is produced by customary methods known to those skilled in the art. The constituents of the primer layer are generally dissolved or dispersed in an organic solvent or solvent mixture and applied to the optionally pretreated carrier. Suitable organic solvents are ketones, such as butanone (= methyl ethyl ketone) or cyclohexanone, ethers, such as tetrahydrofuran, (poly) glycol ethers and glycol ether esters, such as ethylene glycol monomethyl ether or monoethyl ether, propylene glycol monomethyl ether or monoethyl ether, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether or triethylene glycol monomethyl ether, or esters, such as ethyl lactate or butyl lactate, but also hydrocarbons, such as xylene or solvent naphtha. The coating itself can be carried out by pouring on, spin coating or by similar known methods. The solvent is then removed by drying. For this purpose, the material is expediently heated to a temperature in the range from 80 to 130 ° C. for 1 to 3 minutes. The crosslinking reaction is accelerated by the heating.

In an analogous manner, the constituents of the IR radiation-sensitive layer are dissolved or dispersed in an organic solvent or solvent mixture. The solution or dispersion is then applied to the primer layer and dried. The drying conditions can be selected as in the production of the primer layer.

As already described, the silicone rubber layer is then applied to the IR radiation-sensitive layer, dried and crosslinked in the process. Suitable drying conditions are, for example, 1 min at 120 ° C.

The imaging of the recording material is generally carried out by irradiation with radiation having a wavelength of approximately 700 to 1100 nm, that is to say with IR radiation. The imaging is generally digital, i.e. without film, in a suitable radiation device. The device is, for example, an inner or outer drum imagesetter or a flat bed imagesetter. IR laser diodes, YAG lasers, in particular Nd-YAG lasers, or the like serve as radiation sources. The radiation-sensitive layer is decomposed in the exposed areas (generally with the formation of gaseous decomposition products), so that the silicone layer above is no longer firmly anchored there. The silicone layer itself absorbs practically no IR radiation and therefore cannot be ablated as such by IR radiation. The irradiated recording material is then treated with water or an aqueous solution in a device known and known for waterless printing plates. This process is expediently mechanically supported by brushing or in some other way. The silicone layer is removed in the areas hit by the IR radiation. The swelling of the irradiated recording material can optionally be dispensed with. The components of the silicone layer detached during development can be separated off by filtration. So there is no problem with the disposal of used developer solutions contaminated with chemicals.

The printing forms for waterless offset printing produced from the negative working recording material according to the invention show a high resolution and at the same time allow a large print run.

The following examples serve to explain the invention. "Gt" stands for "part (s) by weight". Percentages are percentages by weight unless otherwise stated.

Examples 1 to 8 :

The mixtures described in Table 1 (the numerical values therein are Gt) were spun onto a degreased bright-rolled aluminum plate with a thickness of 0.3 mm. The coating applied in this way was then dried in a circulating air cabinet at 120 ° C. for 2 minutes.

In the comparative example and in Examples 1 to 4, a mixture of was applied to the dried primer layer 56.7 g ®EFWEKO NC 118/2 from Degussa AG (mixture of 18% high color channel (HCC) carbon black, 56% collodion wool (dinitrocellulose), 22% plasticizer and 4% additive); 20% dispersion in ethylene glycol monomethyl ether, 6.0 g modified siloxane / glycol copolymer (®Edaplan LA 411 from Münzing Chemie GmbH, Heilbronn), 1% solution in butanone, 3.0 g Polyisocyanate crosslinker (about 31% NCO groups; ®Desrnodur VKS 20 F from Bayer AG), 20% solution in butanone, 164.26 g Butanone and 69.84 g Ethylene glycol monomethyl ether (®Dowanol PMA from Dow Chemical) applied and dried for 2 min at 120 ° C in a circulating air cabinet. The IR radiation-sensitive layer then had a weight of 0.92 g / m ² .

In Examples 5 to 8, a mixture was made on the primer layer 4.97 g Nitrocellulose (contains 18% dibutyl phthalate as plasticizer; Walsroder NC chips E 950 from Wolff Walsrode AG), 4.13 g Polyisocyanate crosslinker (about 31% NCO groups; ®Desmodur VKS 20F from Bayer AG), 20% solution in butanone, 64.22 g a dispersion of 7.51 g of LCF (Low Color Fumace) carbon black (Special Black 100 from Degussa), 3.22 g of nitrocellulose (Walsroder NC chips E 950) and 53.4 g of ethylene glycol monomethyl ether (®Dowanol PMA), 8.25 g modified siloxane / glycol copolymer (®Edaplan LA 411 from Münzing Chemie GmbH, Heilbronn), 1% solution in butanone, 201.93 g Butanone and 266.60 g Ethylene glycol monomethyl applied and dried as described. The weight of the dried IR radiation-sensitive layer was 0.96 g / m ² . The silicone layer applied to this layer was identical to that in the comparative example and in Examples 1 to 4.

A mixture was then applied to the IR radiation-sensitive layer 23.79 g a hydroxy-terminated polydimethylsiloxane with a viscosity of about 5,000 mPs, 2.54 g Tris (methyl-ethyl-ketoximo) vinyl silane (H ₂ C = CH-Si [-ON = C (CH ₃ ) -C ₂ H ₅ ] ₃ ), 13.50 g a 1% solution of dibutyltin acetate in an isoparaffinic hydrocarbon mixture with a boiling range from 117 to 134 ° C (catalyst C80 from Wacker Chemie GmbH), 0.54 g 3- (2-Amino-ethyl) -amino-propyl-trimethoxy-silane, 177.74 g an isoparaffinic hydrocarbon mixture with a boiling range of 117 to 134 ° C (®Isopar E from Exxon) and 81.90 g butanone spun on. The layer thus produced was dried at 120 ° C. for 2 minutes. The weight of the dried silicone layer was then 3.1 g / m ² , the thickness of the layer correspondingly about 3 μm.

The recording material produced in this way was then mounted on the roller of an outer drum imagesetter and exposed to the IR radiation of an Nd-YAG laser which emitted radiation with a power of 100 mW and a wavelength of 1064 nm and whose spot size was 20 μm. The energy arriving on the plate was adjusted to 350 mJ / cm ² by rotating the drum. At the same time the laser was moved so that lines were written in the material. The material digitally imaged in this way was then treated with water at room temperature in a system customary for the development of waterless printing plates and brushed in order to close the IR radiation-sensitive layer and the areas above the silicon layer in the areas hit by the radiation remove. The sensitivity was deduced from the width of the lines produced in the material. The closer the line width comes to the diameter of the laser beam used for exposure (20 µm), the higher the sensitivity.

The printing form obtained from the recording material according to the invention showed a high resolution and a high stability during printing, so that longer print runs were also possible.

Explanations to Table 1: ®Duroxyn EF 900 Epoxy resin based on epichlorohydrin and bisphenol-A, esterified with ricin fatty acid, 58% epoxy resin and 42% fatty acid modification; dynamic viscosity (DIN 53 015; 23 ° C): 650 to 950 mPa s; a 60% solution in xylene was used ®Macrynal SM 540 Acrylic resin with units of (2-hydroxyethyl) acrylate or methacrylate, a hydroxyl number (DIN 53 240) from 40 to 50, a hydroxyl group content (based on solids) of about 1.4% and a dynamic viscosity (to 50% diluted with xylene; DIN 53 018 / ISO 3219; 23 ° C) from 300 to 550 mPa s; a 60% solution in xylene / butyl acetate was used (mixing ratio: 9 pbw to 1 pbw) ®Mowital B 30 H Polyvinyl butyral containing 75 to 78% vinyl acetal, 1 to 4% vinyl acetate and 18 to 21% vinyl alcohol units ®Carboset 526 thermoplastic polyacrylate (molecular weight M _w about 200,000; acid number about 100; glass transition temperature T _g about 70 ° C; manufacturer: BF Goodrich) ®Cymel 303 Hexamethoxymethyl melamine ®Beckopox EP 301 unmodified epoxy resin from epichlorohydrin and bisphenol-A ®Kronos 2059 TiO ₂ pigment (a 50% dispersion of ®Duroxyn EF 900 and Kronos 2059 (1: 1) in ®Dowanol PMA was used) pTsOH para toluenesulfonic acid MEK Methyl ethyl ketone (= butanone)

Examples 9 to 18

The mixtures described in Table 2 (the numbers given are Gt) were spun onto a degreased, bright-rolled aluminum plate with a thickness of 0.3 mm. The coating applied in this way was again dried for 2 min in a circulating air cabinet at 120 ° C.

A mixture of was then applied to the dried primer layer 1.57 g Nitrocellulose (contains 18% dibutyl phthalate as plasticizer; Walsroder NC chips E 950 from Wolff Walsrode AG), 2.75 g Polyisocyanate crosslinker (about 31% NCO groups; ®Desmodur VKS 20F from Bayer AG), 20% solution in butanone, 59.03 g a dispersion of 6.20 g LCF (Low Color Furnace) carbon black (Special Black 250 from Degussa), 2.66 g nitrocellulose (Walsroder NC chips E 950) and 50.18 g ethylene glycol monomethyl ether (®Dowanol PMA), 5.50 g modified siloxane / glycol copolymer (®Edaplan LA 411 from Münzing Chemie GmbH, Heilbronn), 1% solution in butanone, 207.96 g Butanone and 273.22 g Ethylene glycol monomethyl applied and dried for 2 min at 120 ° C in a circulating air cabinet. The IR radiation-sensitive layer then had a weight of 0.50 g / m ² .

A mixture was then applied to the IR radiation-sensitive layer 36.44 g a hydroxy-terminated polydimethylsiloxane with a viscosity of about 6,000 mPs (CDS 6T from Wacker Chemie GmbH), 2.56 g Tris (methyl-ethyl-ketoximo) vinyl silane (H ₂ C = CH-Si [-ON = C (CH ₃ ) -C ₂ H ₅ ] ₃ ), 20.00 g a 1% solution of dibutyltin acetate in an isoparaffinic hydrocarbon mixture with a boiling range from 117 to 134 ° C (®Isopar E from Exxon), 0.80 g 3- (2-Amino-ethyl) -amino-propyl-trimethoxy-silane, 302.20 g an isoparaffinic hydrocarbon mixture with a boiling range of 117 to 134 ° C (®Isopar E from Exxon) and 138.00 g butanone spun on. The layer thus produced was dried at 120 ° C. for 1 minute. The weight of the dried silicone layer was 2.2 g / m ² .

Explanations to Table 2: ®Alcoa P 807/808 Al ₂ O ₃ pigment from Alcoa Chemie GmbH ®Tosoh TZ-OITZ-3Y / TZ-8Y ZrO ₂ pigment from Tosoh Corporation / Japan ®Aerosil R 972 SiO ₂ pigment from Degussa AG

Example 19:

A mixture of was placed on a degreased bright aluminum plate with a thickness of 0.3 mm 666.00 g ®Beckopox EP 301 (75% in xylene), 810.00 g ®Beckopox EP 301, 270.00 g ®Cymel 303, 270.00 g para toluenesulfonic acid (10% in ethylene glycol monomethyl ether), 2160.00 g TiO ₂ pigment (®Kronos 2310; 50% in ethylene glycol monomethyl ether), 135.00 g modified siloxane / glycol copolymer (®Edaplan LA 411; 10% in ethylene glycol monomethyl ether), 9180.00 g Butanone and 4509.00 g Ethylene glycol monomethyl spun on. The coating applied in this way was dried in a circulating air cabinet at 120 ° C. for 2 minutes. The layer then had a weight of 3.16 g / m ² .

A mixture of was then applied to the primer layer thus produced 3.31 g Nitrocellulose (contains 18% dibutyl phthalate as plasticizer, Walsroder NC chips E 950 from Wolff Walsrode AG), 1.13 g Hexamethoxymethyl-melamine (®Cymel 301; 20% solution in butanone), 0.45 g para- toluenesulfonic acid (10% in butanone), 0.90 g an IR-absorbing dye with an absorption maximum at about 820 nm (®PRO-JET 830 from Zeneca Specialist Colors), 2.25 g modified siloxane / glycol copolymer (®Edaplan LA 411 from Münzing Chemie GmbH, Heilbronn), 1% solution in butanone, 83.77 g Butanone and 58.20 g Ethylene glycol monomethyl applied and dried for 2 min at 120 ° C in a circulating air cabinet. The IR radiation-sensitive layer then had a weight of 1.01 g / m ² .

A mixture was then applied to the IR radiation-sensitive layer 27.75 g a hydroxy-terminated polydimethylsiloxane with a viscosity of about 5,000 mPs, 2.96 g Tris- (methyl ethyl ketoximo) vinyl-silane, 15.75 g a 1% solution of dibutyltin acetate in an isoparaffinic hydrocarbon mixture with a boiling range from 117 to 134 ° C (catalyst C 80 from Wacker Chemie GmbH), 0.63 g 3- (2-Amino-ethyl) -amino-propyl-trimethoxy-silane, 277.36 g an isoparaffinic hydrocarbon mixture with a boiling range of 117 to 134 ° C (®Isopar E from Exxon) and 125.55 g butanone spun on. The layer thus produced was then dried at 120 ° C. for 1 minute. The weight of the dried silicone layer was 2.51 g / m ² .

The recording material produced in this way was exposed to the radiation from IR laser diodes (830 nm; power of 10 watts) on an outer drum exposer (40 revolutions per minute) and, after water-assisted mechanical removal of the ablated layer residues, gave a sharp image of high resolution.

Claims (16)

1. A recording material which is sensitive to IR radiation and comprises, in the order given, a substrate, a primer layer, an IR-absorbing layer and a silicone layer, wherein the primer layer contains a mixture of an unmodified epoxy resin, a further organic polymer which has functional groups, and a crosslinking agent which reacts with the unmodified epoxy resin and the functional groups of the organic polymer.
2. Recording material according to claim 1, wherein the functional groups of the organic polymer are hydroxyl and/or carboxyl groups.
3. Recording material according to claim 1 or 2, wherein the organic polymer having functional groups is a fatty acid-modified, oven-drying or air-drying epoxy resin, a partially acetalated polyvinyl alcohol or an acrylic resin containing hydroxyl groups.
4. Recording material according to any of claims 1 to 3, wherein the amount of the unmodified epoxy resin is from 2.0 to 94.0% by weight, preferably from 2.5 to 80.0% by weight, more preferably from 2.5 to 49.0% by weight, based in each case on the total weight of the nonvolatile components of the primer layer.
5. Recording material according to any of claims 1 to 4, wherein the weight ratio of unmodified epoxy resin to the further organic polymer having functional groups is in the range of from 1:36 to 89:1, preferably in the range of from 1:8 to 8:1.
6. Recording material according to claim 5, wherein the amount of the crosslinking agent is from 5 to 35% by weight, preferably from 10 to 30% by weight, based in each case on the total weight of the nonvolatile components of the primer layer.
7. Recording material according to any of claims 1 to 6, wherein the primer layer contains finely divided pigments, preferably inorganic pigments.
8. Recording material according to claim 7, wherein the inorganic pigments are SiO₂, Al₂O₃, ZrO₂ or TiO₂ pigments.
9. Recording material according to claim 7 or 8, wherein the amount of the pigments is from 1 to 40% by weight, preferably from 5 to 30% by weight, based in each case on the total weight of the nonvolatile components of the primer layer.
10. Recording material according to any of claims 1 to 9, wherein the substrate is a degreased plate or foil of aluminium or an aluminium alloy, which has been bright rolled or pretreated in simple processes.
11. Recording material according to any of claims 1 to 6, wherein the IR-absorbing layer contains a) a component which converts the IR radiant energy into heat, b) a polymeric binder which undergoes thermal degradation or decomposition under the action of the heat generated from the IR radiation and c) a crosslinking resin and/or a crosslinking agent.
12. Recording material according to any of claims 1 to 11, wherein the weight of the IR sensitive layer is from 0.1 to 4.0 g/m², preferably from 0.2 to 3.0 g/m², more preferably from 0.5 to 1.5 g/m².
13. Recording material according to any of claims 1 to 12, wherein the silicone layer comprises an unvulcanized condensation silicone rubber.
14. Recording material according to any of claims 1 to 13, wherein the weight of the silicone layer is from 1.0 to 5.0 g/m², preferably from 1.2 to 3.5 g/m², more preferably from 1.5 to 3.0 g/m².
15. Recording material according to any of claims 1 to 14, wherein a plastic film, preferably a polyethylene film, is present on the silicone layer.
16. A process for the production of a printing plate for waterless offset printing, wherein a recording material as claimed in one or more of claims 1 to 15 is exposed imagewise to IR radiation, preferably to IR laser radiation, and is then freed from the ablated layer components by means of water or an aqueous solution.