EP3695275A1 - Relief precursor having low cupping and fluting - Google Patents

Abstract

The invention relates to a digitally imageable, photopolymerizable relief precursor, at least comprising, arranged one atop the other in the specified sequence, (A) a dimensionally stable carrier; (AH) optionally, an adhesion-promoting layer; (B) a relief-forming layer, at least containing a crosslinkable elastomer binding agent, a first ethylenically unsaturated monomer and a photoinitiator; (C) at least one intermediate layer, at least containing a first, non-radically crosslinkable elastic polymer; (D) a laser-ablatable mask layer, at least containing a second, non-radically crosslinkable elastic polymer, a UVA light-absorbing material and an IR light-absorbing material; and optionally (E) a detachable cover layer; characterized in that the layer (C) and, optionally, the layer (D) contain at least a second ethylenically unsaturated monomer.

Description

 Relief precursor with low cupping and fluting

The invention relates to a relief precursor with which relief structures are obtained which have undesired effects such as cupping and / or fluting to a reduced extent. The relief precursor according to the invention has an intermediate layer which contains an elastic, non-radically crosslinkable polymer and an ethylenically unsaturated monomer.

Relief structures such as printing plates are used for printing various substrates, such as paper, foil, cardboard, with low-viscosity inks. The printing inks are mostly water-based or alcohol-based polar inks. The printing process requires printing forms that are soft, elastic and resistant to polar inks.

Conventional precursors for relief structures therefore contain an elastomeric non-polar binder, usually block copolymers based on styrene-isoprene or styrene-butadiene, in combination with monomers, plasticizers and one or more photoinitiators (see, for example, US Pat. No. 4,323,636). This radiation-sensitive layer is generally a few millimeters thick and is located on a dimensionally stable support, usually a PET film. The relief is produced by exposure to electromagnetic radiation through a masking film. During exposure, the exposed areas crosslink, but the unexposed areas of the precursor remain soluble or liquefiable and are removed by suitable methods.

As an alternative to film exposure, relief structures can also be exposed by means of a laser-generated mask. The thin ablatable mask layer is in the so-called digital relief precursors directly on the radiation-sensitive Layer, as described for example in US 5,262,275. By imagewise ablation a mask is generated, is then exposed by the electromagnetic radiation. Regardless of whether the exposure of the radiation-sensitive layer takes place through a film or by means of an integral laser mask, the relief must subsequently be produced by washing with suitable organic solvents, see, for example, EP 0 332 070. When the relief is washed out, the cross-linked layers also swell Regions of the relief structure by the solvent. This solvent must be removed again in a drying step. Due to the temperature sensitivity of the carrier film, the drying of the Flexod jerk shapes can be carried out only at low temperatures. There has been no shortage of attempts to develop relief structures that can be developed faster. Thus, printing plates can also be thermally developed, see, for example, EP 1 239 329 or EP 1 170 121. Here, the relief structures are heated to the melting temperature after the imagewise exposure. The unexposed areas of the relief structure thereby become partially liquid and sticky and are then removed continuously with a nonwoven or a tissue which absorbs the liquid material.

Cupping is understood by the person skilled in the art to be the phenomenon of the formation of measurable edges at the boundaries of the picture elements, in particular at picture elements. In EP 3 035 123 A1, a theory is formulated for the formation of these raised edges, according to which, due to the diffusion of the crosslinker at the boundary between unexposed and exposed areas of the printing plate, significant transport of material results, which is the dot shape of the screen dot and in particular the edges of the screen Grid point essentially determined. This form of the grid point leads to an uneven transfer of the printing ink to the substrate during printing. In extreme cases, rings are obtained instead of circles.

The so-called fluting, also called washing board effect, is observed as an undesirable effect when printing on the outermost layer of corrugated board. The fluting is observed as a striped appearance of alternating darker and lighter areas. The darker areas occur where the outermost layer and the corrugated inner layer touch. The fluting effect becomes especially strong visible, if no solid areas, but Tonwertbereiche be reproduced with a low area ratio. In the case of digitally imageable relief precursors, experience has shown that this effect is particularly pronounced. The object of the invention is to provide a relief precursor which leads to less cupping and / or fluting and thereby to better printing results.

Surprisingly, it has been found that the cupping and fluting can be significantly reduced if the relief precursor contains an intermediate layer which contains a non-radically crosslinkable polymer and an ethylenically unsaturated monomer.

The object is achieved by a digitally imageable, photopolymerizable relief precursor at least comprising, arranged one above the other in the order named, (A) a dimensionally stable support;

 (AH) optionally an adhesion-promoting layer;

 (B) a relief-forming layer, at least comprising a crosslinkable elastomeric binder, a first ethylenically unsaturated monomer and a photoinitiator;

 (C) at least one intermediate layer, at least containing a first, not radically crosslinkable elastic polymer;

 (D) a laser ablatable mask layer, at least comprising a second, non-radically crosslinkable elastic polymer, a UVA light absorbing material and an IR light absorbing material; and optional

 (E) a peelable topcoat;

characterized in that the layer (C) and optionally the layer (D) contain at least one second ethylenically unsaturated monomer.

As a dimensionally stable carrier (A) dimensionally stable carrier materials can be used, which may optionally have further layers. Examples of suitable dimensionally stable carriers are plates, films and conical and cylindrical tubes made of metals such as steel, aluminum, copper or nickel or of plastics such as polyethylene terephthalate, polybutylene terephthalate, polyamide and polycarbonate, woven and nonwoven fabrics such as glass fiber fabric, as well as composite materials of glass fibers and plastics. Dimensionally stable carriers are, in particular, dimensionally stable carrier films or metal sheets, for example polyethylene or polyester films, steel sheets or aluminum sheets. These carrier films or sheets are generally 50 to 1100 μm, preferably 75 to 400 μm, for example about 250 μm thick. Will one Used plastic film whose thickness is in the range of 100 to 200 μηη, preferably from 125 to 175 μηη. When steel is used as the substrate, steel sheets having a thickness of 0.05 to 0.3 mm are preferable. For protection against corrosion tin-plated steel sheets are preferably used. These carrier films or carrier plates can be coated with a thin, adhesion-promoting layer, for example a 0.05 to 5 μm thick layer, on the side of the carrier film facing the substrate layer. This adhesive layer may consist, for example, of a mixture of a polycarbonate, a phenoxy resin and a multifunctional isocyanate. These carrier foils or carrier plates can already be equipped or provided with a thin adhesion-promoting layer (AH). Polyurethane adhesive paints (for example according to DE3045516) based on polyisocyanate-crosslinked polyether or polyester paints in layer thicknesses of between 0.1 and 50 μm, in particular between 2 and 30 μm, can serve as adhesive lacquer layers, for example.

Additional adhesion-improving intermediate layers (AH) may be located on the side of the adhesive layer facing away from the carrier layer, have layer thicknesses between 0.1 and 50, in particular 1 and 10 μm, and may be prepared, for example, from dilute aqueous-alcoholic solution of (for example 80 mol %) partially saponified polyvinyl esters, phenylglycerol ether monoacrylate and glyoxal, drying and baking are obtained.

Adhesion improving layers or intermediate layers are said to increase the adhesion between individual layers and to stabilize the layer structure. Here are materials to choose that can build an interaction to both layers. Preferred examples thereof are surfactants, amphiphilic molecules having hydrophobic and hydrophilic regions, and block copolymers. and oligomers containing blocks compatible with the two layers or compatible with the polymers in the layers.

The adhesion between the dimensionally stable support (A) and the relief-forming layer (B) should be greater than 0.5 N / cm when measured in a peel test at a take-off angle of 90 ° and a take-off speed of 30 mm / min. The relief precursor comprises at least one photopolymerizable, relief-forming layer (B). The photopolymerizable relief-forming layer can be applied directly to the support. But between the carrier and the relief-forming layer can also other layers are, such as adhesive layers or elastic or compressible sub-layers.

The relief-forming layer (B) may also consist of more than one layer, wherein it generally comprises 2 to 20 layers, preferably 2 to 5 layers, more preferably 2 to 3 layers, most preferably 2 layers. The layers may contain the same constituents or different constituents and this in equal or different proportions. Preferably, these layers contain the same constituents. Preferably, the relief-forming layers, which are closest to the carrier layer, are already fixed, crosslinked and / or reacted. At least one relief-forming layer is arranged on these fixed, crosslinked, reacted layers, which can still be fixed, crosslinked or allowed to react.

Elastomeric binders for the production of relief-forming layers of flexographic printing elements are known to the person skilled in the art. Examples which may be mentioned are styrene-diene block copolymers, natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, nitrile-butadiene rubber, butyl rubber, styrene-isoprene rubber, styrene-butadiene-isoprene rubber, polynorbornene rubber or ethylene-propylene-diene rubber (EPDM). Preference is given to using hydrophobic binders. Such binders are soluble in organic solvents or mixtures thereof.

The elastomer is preferably a thermoplastic elastomeric block copolymer of alkenylaromatics and 1,3-dienes. The block copolymers may be linear, branched or radial block copolymers. Usually they are triblock copolymers of the ABA type, but they can also be AB-type diblock polymers or those having a plurality of alternating elastomeric and thermoplastic blocks, eg ABABA. It is also possible to use mixtures of two or more different block copolymers. Commercially available triblock copolymers often contain certain proportions of diblock copolymers. The diene units can be 1, 2 or 1, 4 linked. Both styrene-butadiene or styrene-isoprene type block copolymers and styrene-butadiene-isoprene type block copolymers can be used. They are for example under the name Kraton © commercially available. Also useful are thermoplastic elastomeric block copolymers having endblocks of styrene and a random styrene-butadiene midblock. The block copolymers may also be fully or partially hydrogenated, as in SEBS rubbers. Preferred elastomeric binders are triblock copolymers of the ABA type or radial block copolymers of the type (AB) n, where A is styrene and B are a diene, and random copolymers and random copolymers of styrene and a diene.

In a preferred embodiment of the invention, the thermoplastically elastomeric binders are at least one styrene-isoprene block copolymer, in particular styrene-isoprene-styrene block copolymers, wherein the polymers may also contain portions of diblock copolymers styrene-isoprene. Preferred styrene-isoprene-type binders generally contain from 10 to 30% by weight, preferably from 12 to 28% by weight and more preferably from 14 to 25% by weight, of styrene. These block copolymers usually have an average molecular weight Mw (weight average) of from 100,000 to 300,000 g / mol. Of course, mixtures of different styrene-isoprene block copolymers can be used. In a second embodiment of the invention, radial isoprene-styrene block copolymers may preferably be used. The isoprene units in the polyisoprene blocks can be 1,4-linked, ie the remaining double bond is arranged in the chain or 3,4-linked, ie the remaining double bond is arranged on the side. Block copolymers can be used which have essentially 1,4-linkages and binders which have certain proportions of 3,4-linkages. The pendant vinyl groups in binders having 3,4-linked isoprene units may preferentially react in the course of crosslinking of the photopolymerizable layer and accordingly give a high crosslinked plate. For example, styrene-isoprene block copolymers can be used which have a vinyl group content of 20 to 70%. In a preferred embodiment of the invention, one can use a radial styrene-isoprene copolymer which has a vinyl group content of less than 10%. In a second preferred embodiment of the invention, a mixture of two different styrene-isoprene block copolymers is used. One of these preferably has a vinyl group content of at least 20%, in particular from 20 to 70%, preferably from 25 to 45%. The other may have a low vinyl group content, for example, less than 10%. It is furthermore preferred to use a mixture of two styrene-isoprene copolymers, one of which has a high diblock content of more than 40% by weight and the second one a lower diblock fraction of less than 30% by weight. In addition to the thermoplastic-elastomeric block copolymers mentioned, in particular the styrene-isoprene block copolymers, the photopolymerizable layer may also comprise further elastomeric binders other than the block copolymers. With such additional binders, Also called secondary binder, the properties of the photopolymerizable layer can be modified. An example of a secondary binder is vinyltoluene-a-methylstyrene copolymers. As a rule, the amount of such secondary binder should not exceed 25% by weight with respect to the total amount of all the binders used. Preferably, the amount of such secondary binder does not exceed 15% by weight, more preferably not 10% by weight. The total amount of binders is usually 30 to 90 wt .-% with respect to the sum of all components of the relief-forming layer, preferably 40 to 85 wt .-% and particularly preferably 60 to 85 wt .-%.

In water-developable relief precursors, water-soluble, swellable, dispersible or emulsifiable polymers are used. In addition to fully or partially hydrolyzed polyvinyl acetates, it is possible to use polyvinyl alcohol, polyvinyl acetals, polystyrene sulfonates, polyurethanes, polyamides (as described, for example, in EP 0 085 472 or in DE 1522444) and any desired combinations thereof. Examples of such polymers can be found in EP 0 079 514, EP 0 224 164, or EP 0 059 988. These polymers can be linear, branched, star-shaped or dendritic and are present both as homopolymers, random copolymers, block copolymers or alternating copolymers. Very often, the polymers mentioned are provided with functional groups which either increase the solubility and / or can participate in crosslinking reactions. These groups include, for example, carboxy, S0 ₃ , OH, thiol, ethylenically unsaturated, (meth) acrylate, epoxide groups and any combinations thereof.

The total amount of elastomeric binders is in the case of the relief-forming layer (B) usually 30 to 90 wt .-% with respect to the sum of all components of the relief-forming layer, preferably 40 to 85 wt .-% and particularly preferably 45 to 85 wt .-%.

The relief-forming layer (B) may contain further constituents selected from the group consisting of plasticizers, solvents, further binders, colorants, stabilizers, regulators, UV absorbers, dispersing aids, a crosslinker, viscosity modifiers, surface-active substances and any desired combinations thereof , These additives or auxiliaries and additives are in the radiation-sensitive mixture in a total concentration in the range of 0.001 to 60 wt .-%, based on the total formulation, preferably in the range of 0.01 to 50 wt .-%, especially in the range of 0 From 1 to 50% by weight, more particularly in the range from 1 to 50% by weight. The individual additives are in concentrations of 0.001 to 40 Wt .-%, based on the total formulation, preferably in the range of 0.01 to 40 wt .-%, especially in the range of 0.1 to 40 wt .-%, especially in the range of 0.1 to 35 wt .-%, contain. The photopolymerizable relief-forming layer (B) further comprises, in a known manner, at least one first ethylenically unsaturated monomer which is compatible with the binder (s). The first ethylenically unsaturated monomer may also be mixtures of two or more different monomers. Suitable compounds have at least one olefinic double bond and are polymerizable. These are therefore referred to below as monomers. Esters or amides of acrylic acid or methacrylic acid with monofunctional or polyfunctional alcohols, amines, amino alcohols or hydroxy ethers and esters, esters of fumaric or maleic acid, vinyl ethers, vinyl esters and allyl compounds have proved to be particularly advantageous.

In general, these monomers are not gaseous compounds at room temperature. Preferably, the first ethylenically unsaturated monomer contains at least 2 ethylenically unsaturated groups, more preferably 2 to 6 ethylenically unsaturated groups, most preferably 2 or more ethylenically unsaturated groups. Compounds with C-C triple bonds can also be used in the radiation-sensitive mixture. Preferably, the ethylenically unsaturated group is at least one acrylate and / or one methacrylate group, but it is also possible to use styrene derivatives, acrylamides, vinyl esters and vinyl ethers. The ethylenically unsaturated monomer has a molecular weight of generally less than 600 g / mol, preferably less than 450 g / mol, more preferably less than 400 g / mol, very preferably less than 350 g / mol and especially less than 300 g / mol on.

Particularly suitable are derivatives of acrylic and / or methacrylic acid, such as their esters with mono- or polyhydric alcohols, for example acrylic or methacrylic esters of alkanols having 1 to 20 carbon atoms, such as methyl methacrylate, ethyl acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Lauryl (meth) acrylate, (meth) acrylic esters of polyhydric alcohols having 2 to 20 carbon atoms, for example 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth ) acrylate, butanediol-1,4-di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, 1,1,1-trimethylol Propanetri (meth) acrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol diacrylate, di-, tri- and tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate or pentaerythritol tetra (meth) acrylate, further poly (ethylene oxide) di (meth) acrylate, m-methylpoly (ethylene oxide) -yl (meth) acrylate, N, N-diethylaminoethyl acrylate, a reaction product of 1 mole of glycerol, 1 Mole of epichlorohydrin and 3 moles of acrylic acid and glycidyl methacrylate and bisphenol A diglycidyl ether acrylate.

Also suitable are derivatives of the acrylamide and the methacrylamide, e.g. Ethers of their N-methylol derivatives with monohydric and polyhydric alcohols, e.g. Ethylene glycol, glycerol, 1,1,1-trimethylolpropane, oligomeric or polymeric ethylene oxide derivatives. These are particularly suitable when polyamides or polyvinyl alcohol are used as binders. Also suitable are so-called epoxide and urethane (meth) acrylates, as obtained, for example, by reacting bisphenol A diglycidyl ether with (meth) acrylic acid or by reacting diisocyanates with hydroxyalkyl (meth) acrylates or with hydroxyl-containing polyesters or polyethers can. Further usable olefinically unsaturated compounds are esters of acrylic or methacrylic acid, especially those with low vapor pressure and those which are modified with compatibilizers, e.g. with hydroxy, amido, sulfoester or sulfonamide groups. Mixtures of the abovementioned copolymerizable ethylenically unsaturated organic compounds can also be used.

Preferred first ethylenically unsaturated monomers are butanediol-1,4-di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, 1,1,1-trimethylolpropane tri (meth) acrylate, 1, 4- Butanediol diacrylate, 1, 6-hexanediol diacrylate, 1, 6-hexanediol dimethacrylate, 1, 9-nonanediol diacrylate, di-, tri- and tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate and pentaerythritol tetra (meth) acrylate.

In one embodiment, the first ethylenically unsaturated monomer in a concentration in the range of 0.5 to 60% by weight, based on the total formulation, preferably in the range of 1 to 50 wt .-%, particularly preferably in the range of 1 to 40 wt. -%, most preferably in the range of 2 to 40 wt .-%.

Furthermore, the relief-forming layer (B) contains one or more initiators or initiator systems of at least two components which, upon irradiation with electromagnetic radiation, generate radicals which cause polymerization and / or crosslinking. Such initiators are known to the person skilled in the art and are described, for example, in the following literature: Bruce M. Monroe et al., Chemical Review, 93, 435 (1993), RS Davidson, Journal of Photochemistry and Biology A: Chemistry, 73, 81 (1993), JP Faussier, Photoinitiated Polymerization-Theory and Applications: Rapra Review, Vol. 9, Report, RapraTechnology (1998), M. Tsunooka et al., 25 Prog. Polym. Sci., 21, 1 (1996), FD Saeva, Topics in Current Chemistry, 1 56, 59 (1990), GG Maslak, Topics in Current Chemistry, 168, 1 (1993), HB Shuster et al., JAGS, 1 12, 6329 (1990) and IDF Eaton et al., JAGS, 102, 3298 (1980), P. Fouassier and JF Rabek, Radiation Curing in Polymer Science and Technology, pages 77 to 17 (1993) or KK Dietliker, Photoinitiators for free Radical and Cationic Polymerization, Chemistry & Technology of UV & EB Formulation for Coatings, Inks and Paints, Volume, 3, Sita Technology LTD, London 1991; UV or EB Curing, Sita Technology LTD, London 1999. Other initiators are described in JP45-37377, JP44-86516, US3567453, US4343891, EP109772, EP109773, JP63138345, JP63142345, JP63142346 and RS Davidson, Exploring the Science , JP63143537, JP4642363, JP59152396, JP61151597, JP6341484, JP2249 and JP24705, JP626223, JPB6314340, JP1559174831, JP1304453 and JP1 152109.

Preference is given to initiators or initiator systems which originate from the group of Norrish type I or Norrisch type II initiators which are based on H abstraction or electron transfer. Examples of Norrish type I initiators include benzoyl radical initiators, α-hydroxy ketones, α-amino ketones, acyl phosphine oxides, bisacyl phosphine oxides, triazines, and hexaaryl bisimidazoles, which can be further combined with dyes or sensitizers to increase sensitivity. Combinations of ketones or aldehydes with H-carriers, such as, for example, amines or thiols, may be mentioned in particular in the case of the Norrish type II initiators. The initiators are preferably selected from the group consisting of benzil dimethyl ketal, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxides, 2,4,6-trimethylbenzoylphenylphosphinates; Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxides, bis (2,6-dimethoxybenzoyl) -2, -1,4-trimethylpentyl) phosphine oxides, Michler's ketone, benzophenone alone and / or combined with sensitizers, amines or thiols and any Combinations of it. Other initiators which can be used are onium salts, organic peroxides, thio compounds, ketoximes, borates, coumarins, ketocoumarines, azinium and azo compounds, metallocenes and compounds having a carbon-halogen group which can also be combined or used together with sensitizers, amines or thiols. In the sensitizers, for example, xanthones, thioxanthones, anthracenes, perylenes, phenothiazines, benzophenones, acetophenones, coumarins, ketocoumarins and dyes can be used. A prerequisite for sensitization is that either the triplet energy of the sensitizer is higher than that of the sensitizer to be sensitized or it may come to an electron transfer from an excited state of the sensitizer.

In general, the relief-forming layer according to a preceding embodiment contains the initiator or the initiator system in a concentration in the range from 0.1 to 20% by weight, based on the entire formulation. Preferred initiator concentrations are in the range of 1 to 10 wt .-%, more preferably in the range of 1 to 8 wt .-%, most preferably in the range of 1 to 6 wt .-%. The relief-forming layer (B) may contain plasticizer. It is also possible to use mixtures of different plasticizers. Examples of suitable plasticizers include modified and unmodified natural oils and resins, such as high-boiling paraffinic, naphthenic or aromatic mineral oils, synthetic oligomers or resins such as oligostyrene, high-boiling esters, oligomeric styrene-butadiene copolymers, oligomeric alpha-methylstyrene / p-methylstyrene oligomers. Copolymers, liquid oligobutadienes, in particular those having a molecular weight of 500 to 5000 g / mol, or liquid oligomeric acrylonitrile-butadiene copolymers or oligomeric ethylene-propylene-diene copolymers. Preference is given to polybutadiene oils (liquid oligobutadienes), in particular those having a molecular weight of 500 to 5000 g / mol, high-boiling aliphatic esters, in particular alkylmono- and dicarboxylic acid esters, for example stearates or adipates, and mineral oils. Particularly preferred are high-boiling, substantially paraffinic and / or naphthenic mineral oils. For example, so-called paraffin-based solvates and special oils can be used. The expert distinguishes mineral oils from technical white oils, which may still have a very low aromatics content, as well as medicinal white oils, which are essentially free of aromatics. They are commercially available and equally well suited. Particularly common plasticizers are white oils or oligomeric plasticizers, in particular polybutadiene oils, carboxylic esters, phthalates. For example, reference may be made to EP 992 849 and EP 2 279 454. The amount of optional plasticizer will be determined by one skilled in the art according to the desired properties of the layer. As a rule, it will not exceed 60% by weight of the sum of all constituents of the photopolymerizable relief-forming layer (B), in general it is 0 to 60% by weight, preferably 0 to 50% by weight.

The relief-forming layer (B) may further contain other functional additives, for example as described in US 8,808,968, small amounts of phosphites, phosphines, thioethers and amino-functional compounds. This can be the disturbing influence of oxygen, which is still in the layer or diffused, switched off or minimized and an even higher resolution can be obtained.

The relief-forming layer (B) may in further embodiments contain further constituents which are selected from the group consisting of solvents, stabilizers, dyes, pigments, additives, surface-active substances, UV absorbers, regulators, plasticizers, binders and any combinations thereof. Furthermore, the relief-forming layer (B) may contain surface-active substances such as hydrophobic waxes or siliconized or perfluorinated compounds, as described in US Pat. No. 8,114,566. These substances migrate from the relief layer to the surface during the drying of the flexographic printing plates, have a repellent effect on the printing ink and, in the printing process, cause less fine rasters to be polluted and the printing plates to be cleaned less frequently. Further, in the radiation-sensitive mixture of the relief-forming layer (B), thermal polymerization inhibitors which do not possess appreciable self-absorption in the actinic region in which the photoinitiator absorbs may be contained, e.g. 2,6-di-tert-butyl-p-cresol, hydroquinone, p-methoxyphenol, β-naphthol, phenothiazine, pyridine, nitrobenzene, m-dinitrobenzene or chloranil; Thiazine dyes such as thionin blue G (C.I. 52025), methylene blue B (C.I. 52015) or toluidine blue (C.I. 52040); or N-nitrosamines, such as N-nitrosodiphenylamine, or the salts, for example the potassium, calcium or aluminum salts of N-nitrosocyclohexylhydroxylamine. In addition, it is also possible to use other inhibitors or stabilizers, as described, for example, in A. Valet, Lichtschutzmittel für Lacke, 33ff, Vincentz Verlag, Hannover 1996, and in particular sterically hindered phenols and amines.

Suitable colorants, such as dyes, pigments or photochromic additives, may also be present in the radiation-sensitive mixture of the relief-forming layer (B) in an amount of from 0.0001 to 2% by weight, based on the mixture. They are used to control the exposure properties, as a slider, the identification, the direct control of the exposure result or aesthetic purposes. The prerequisite for the selection and the amount of such additives is that, just as the inhibitors of the thermally initiated polymerization, they do not disturb the photopolymerization of the mixtures. Suitable examples are the soluble phenazinium, phenoxazinium, acridinium and phenothiazinium dyes, such as neutral red (Cl 50040), safranine T (Cl 50240), rhodanil blue, the salt or amide from rhodamine D (Basic Violet 10, Cl 45170). , Methylene blue B (Cl 52015), thionin blue G (Cl 52025), or acridine orange (CI 46005); as well as solvent Black 3 (Cl 26150). These dyes can also be used in conjunction with a sufficient amount of a reducing agent which does not reduce the dye in the absence of actinic light, but which can reduce the excited state dye upon exposure. Examples of such mild reducing agents are ascorbic acid, anethole, thiourea, for example diethylallylthiourea, in particular N-allylthiourea, and also hydroxylamine derivatives, in particular salts of N-nitrosocyclohexylhydroxylamine, preferably the potassium, calcium and aluminum salts. The latter can, as mentioned, also serve as inhibitors of the thermally initiated polymerization. The reducing agents may generally be added in amounts of 0.005 to 5 wt .-%, based on the mixture, which has proved in many cases the addition of a 3 to 10 times the amount of co-used dye.

UV absorbers in the relief-forming layer (B) can also have advantages and positively influence the relief formation. Compounds suitable as UV absorbers are described, for example, in A. Valet, Lichtschutzmittel für Lacke, 20ff, Vincentz Verlag Hannover 1996. Examples are hydroxyphenylbenzotriazoles, hydroxybenzophenones, hydroxyphenyl-s-triazines, oxalanilides, hydroxyphenylpyrimidines, salicylic acid derivatives and cyanoacrylates, and any combinations thereof. Surfactants include compounds that, in a particular composition, tend to accumulate on the surface of the composition. These include, in particular, surfactants, amphiphilic molecules having hydrophobic and hydrophilic regions, and block copolymers and oligomers containing blocks having a lower surface energy. However, it is also possible to use substances of low to high molecular weight which are incompatible with the formulation and / or migrate to the surface due to their particularly low surface energy, for example waxes, silicones, silanes and fluorinated compounds. Preference is given to waxes, such as paraffin waxes, polyethylene waxes, polypropylene waxes, and any mixtures thereof. In a preferred embodiment, the relief-forming layer (B) contains at least one wax in a concentration in the range of 0.1 to 10 wt .-% based on the total mass of the relief-forming layer (B). Preferably, the wax concentration is in the range of 0.2 to 5 wt .-%, more preferably in the range of 0.5 to 5 wt .-%, most preferably in the range of 0.5 to 4 wt .-%.

These surface-active substances, and in particular the waxes, can have an effect as a mobile barrier layer for oxygen. This will cause oxygen inhibited fixation reactions faster and the level of detail higher. An advantage of using relatively low molecular weight waxes and surfactants is that they always seek to migrate to the freshly generated surface. Preferably, they are used with elastomeric binders such as styrene-butadiene rubbers, nitrile-butadiene rubbers, butyl rubbers, styrene-isoprene rubbers, styrene-butadiene-isoprene rubbers waxes such as paraffin waxes, polyethylene waxes or polypropylene waxes. The thickness of the relief-forming layer (B) is generally 0.1 to 7 mm, preferably 0.5 to 4 mm, more preferably 0.7 to 3 mm and most preferably 0.7 to 2.5 mm. In some cases, the layer thickness is preferably from 2 to 7 mm, more preferably from 2.5 to 7 mm, and most preferably from 2.8 to 7 mm. The layer thickness S of the intermediate layer (C) according to the invention is generally 0.1 to 30 μm, preferably 0.5 to 25 μm, particularly preferably 0.7 to 20 μm and very particularly preferably 0.7 to 15 μm.

The intermediate layer (C) according to the invention comprises at least one first elastic polymer and at least one second ethylenically unsaturated monomer which preferably carries at least two ethylenically unsaturated groups. The second ethylenically unsaturated monomer may be the same or different from the first ethylenically unsaturated monomer. They may be mixtures of two or more different ethylenically unsaturated monomers. Preferably, the first and second ethylenically unsaturated monomers are the same ethylenically unsaturated monomer or mixture of two or more ethylenically unsaturated monomers. Thus, as the second ethylenically unsaturated monomer, all ethylenically unsaturated monomers which have been mentioned above as first ethylenically unsaturated monomers are suitable.

Preferred second ethylenically unsaturated monomers are butanediol-1,4-di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, 1,1,1-trimethylolpropane tri (meth) acrylate, 1, 4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol diacrylate, di-, tri- and tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate and pentaerythritol tetra (meth) acrylate. In one embodiment, the second ethylenically unsaturated monomer is present in the intermediate layer (C) in a concentration K equal to or lower than the concentration of the first ethylenically unsaturated monomer in layer (B). More preferably, K is lower than the concentration of the first ethylenically unsaturated monomer in layer (B). Furthermore, the concentrations of the first ethylenically unsaturated monomer in layer (B) and the concentrations of the second ethylenically unsaturated monomer in intermediate layer (C) differ by ± 2 wt .-%, each based on the total mass of the layer (B) or (C ), preferably ± 1, 5 wt .-%, particularly preferably ± 1 wt .-%. The second ethylenically unsaturated monomer in the intermediate layer (C) is generally in a concentration K of 0.1 to 25 wt .-%, preferably in the range of 0.2 to 20 wt .-%, particularly preferably in the range of 0, 2 to 15 wt .-% and most preferably in the range of 0.2 to 10 wt .-% before, based on the total weight of the intermediate layer (C). The concentration of the second ethylenically unsaturated monomer in the layers can be determined by all methods of analysis known to those skilled in the art. For this purpose, it may be advantageous to detach the individual layers and to investigate the solutions obtained. For this purpose, for example, gas chromatography (optionally coupled with mass spectroscopy) can be used. In another method, the layers are analyzed without the use of solvents by means of secondary ion mass spectrometry (SIMS or ToF SIMS).

It has proved to be advantageous if this is the ratio of the layer thickness S in μηη and the concentration K in% by weight in the range from 30: 0.1 to 0.1: 25 μm by weight, preferably in the range from 25 : 0.2 to 0.5: 20 microns wt .-%, particularly preferably in the range of 20: 0.2 to 0.7: 15 μιτι / ΘΘνν .-%, is located.

The intermediate layer (C) may be a transparent layer to ensure exposure of the relief-forming layer (B). For transparency measurement, the layer constituents are dissolved in a suitable solvent mixture and applied to a transparent PET film (125 μm thickness). Subsequently, the composite is dried for 30 minutes in a drying oven at 1 10 ° C. The transparency measurement can be performed with a UV-VIS Spectrometer Varian Cary 50 Conc with the software Cary Win UV version 2.00 (25), for this purpose the transparency of the PET film without a layer as reference / baseline is subtracted. Measured is in the range of 500 to 350 μηη. The transparency of a 3 to 5 μηη thick intermediate layer (C) in the range of actinic radiation (350-500 nm) should be in the range of 40 to 100%, preferably in the range of 60 to 100%, more preferably in the range of 65 to 100%.

The intermediate layer (C) may be permeable or impermeable to oxygen. In another embodiment, the intermediate layer (C) is impermeable to oxygen. As a result, the inhibition of the radical chain reaction is reduced by post-diffusing oxygen or completely suppressed. As a result, halftone dots have a flat surface. In an embodiment in which the intermediate layer (C) is permeable to oxygen, on the other hand, halftone dots with a rounded surface are produced. This can be advantageous under certain conditions.

In the case where the intermediate layer (C) is impermeable to oxygen, the first elastic polymer used is that which has an oxygen permeability of less than or equal to 1.5 ^× 10 ⁵ cm ² m / (m ^{2 *} d ^* bar). The oxygen permeability is determined by the carrier gas method, according to ASTM D3985, with instruments from Mocon Inc. with coulometric sensor, at 23 ° C and 0% relative humidity. The samples are measured free-standing, the measuring surface is 5 cm ² or 10 cm ² and the sample thickness is between 75 and 108 μηη. In the case that the intermediate layer (C) for oxygen permeable, can be used as the first elastic polymer, such polymers having an oxygen permeability of greater than 1, 5 ^× 10 ⁵ cm ^ m / (m ^{2 *} d ^* bar).

The first elastic polymer is designed so that it carries no groups that can lead to crosslinking in a radical reaction. This ensures that the removal of the intermediate layer by means of solvents or by melting and subsequent adsorption on a development material takes place as completely as possible. The first elastic polymer may be a linear, branched, star-shaped, comb-shaped, dendritic homo- or copolymer. Copolymers may be present as random and / or block copolymers. The first elastic polymer may also be a mixture of different polymers differing, for example, in structure, monomer composition, block lengths, molecular weights, functional groups, their number and / or distribution.

In a further embodiment, the first elastic, non-radically crosslinkable polymer has a δ solubility parameter of 15 to 27 (MPa) ^{/ 2} , in order to be able to dissolve the second ethylenically unsaturated monomer in sufficient quantity. The elastic, non-radically crosslinkable polymer preferably has a δ-solubility viscosity parameter of δ solubility parameter of 17 to 27 (MPa) ^{/ 2} , most preferably δ solubility parameter of 19 to 27 (MPa) ^{/ 2} . Solubility parameters include three factors: the energy of dispersive forces between molecules, the energy of dipolar intermolecular forces between the molecules, and the energy of hydrogen bonds between the molecules. These three parameters can be treated as coordinates for a point in three dimensions, also known as Hansen space. For polymers, the solubility parameter is determined empirically from solution experiments in various solvents. The values of some polymers are listed in Polymer Handbook by J. Brandrup, EH Immergut and EA Grulke, 4th Edition, Wiley-Interscience, 1999.

Suitable first elastic polymers have a softening or melting point below 230 ° C, preferably below 180 ° C and more preferably below 160 ° C.

Suitable first elastic polymers, which are soluble in organic solvents and / or can be thermally developed and have a sufficient barrier effect against oxygen, are, for example, partially hydrolyzed polyvinyl acetates having a degree of saponification of from 30 to a maximum of 80 mol%, ethylene-vinyl acetate copolymers and ethylene oxide. Vinyl alcohol copolymers and ethylene-vinyl acetate-vinyl alcohol copolymers. Also suitable are cyclic acetals of polyvinyl alcohol such as polyvinyl butyral, polyvinyl ethy ral, polyvinyl formal, polyvinyl propyral and copolymers containing two or more different vinyl acetal units selected from vinyl formal, vinyl ethy ral, vinyl propyral and vinyl butyral units. The polyvinyl acetals are always copolymers with vinyl alcohol units, since the conversion of polyvinyl alcohol to the full acetal is not complete for statistical and steric reasons. For example, poly (vinyl butyral) is a poly (vinyl butyralvinyl alcohol). Usually, the residual OH content of said polyvinyl acetals is between 10 and 30% by weight. Vinylethyralvinyl butyralvinyl alcohol copolymers (poly (vinylethyralvinyl butyral)) are very suitable, for example.

Suitable first elastic polymers which are soluble in water and / or organic solvents and / or can develop thermally and have little or no barrier effect against oxygen are, for example, ethylene vinyl acetates, flexible polyamides, polyvinyl chlorides, polyesters, flexible elastomers, nitrocelluloses, modified polyolefins and any combinations thereof, soft-elastic polyamides include long-chain, bifunctional as monomeric building blocks Fatty acids which impart soft elastic properties to the polyamide. Especially suitable is Makromelt® 6900 (Henkel AG). Also suitable are styrene-diene block copolymers, natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, nitrile-butadiene rubber, butyl rubber, styrene-isoprene rubber, styrene-butadiene-isoprene rubber, polynorbornene rubber or ethylene Propylene-diene rubber (EPDM), especially after hydrogenation.

An embodiment includes that the intermediate layer (C) comprises the first non-radically crosslinkable, elastic polymer in a concentration of 60 to 99 wt .-%, preferably in the range of 70 to 99 wt .-%, particularly preferably in the range of 80 contains up to 99 wt .-%.

In an additional embodiment, the intermediate layer (C) contains particles having a particle size of 0.2 to 30 μm, preferably in the range of 0.3 to 20 μm, particularly preferably in the range of 0.5 to 15 μm, very particularly preferably in the range from 1 to 10 μηη. The particle size distribution can be very wide, but is preferably narrow. The particles can bring about a structuring of the surface of the relief-forming layer (B) and produce there a roughness and an enlargement of the surface, which proves to be advantageous in color transfer. The structuring can take place by molding the particles as well as by permanent attachment of the particles to the surface of the relief-forming layer (B).

The particles may be inorganic or organic particles or mixed inorganic-organic particles. The particles may be in amorphous, crystalline or partially crystalline form. They can be round and regular, but also irregular. The shape of the particles can be symmetrical, as is the case with crystalline materials. They can be hollow, porous or compact, and core-shell or onion-like structures can be used. Suitable particles include inorganic fillers, such as silicates, quartz flour, glass particles, silicon oxides or aluminum or titanium oxides, but also natural minerals such as hydroxyapatite, talc, calcium sulfate or calcium carbonate or pigments such as iron or chromium oxides. The particles may be surface-treated or surface-functionalized to ensure uniform dispersion of the particles in the intermediate layer (C). Preferably, silicates or silicas are used. In a specific embodiment, particles of organic materials such as polyethylene, polycarbonates and poly (meth) acrylates may also be used. The particles may be crosslinked or uncrosslinked and may also be functionalized with organic functional groups. When organic particles are used, it is advantageous if these materials are not dissolved in the composition used to produce the layer or are incompatible with the polymers used therein, resulting in the formation of discrete phases and particles.

Depending on the surface functionality of the respective particles, the process of taking the topography of the barrier layer (C) onto the relief-forming layer (B) may be different. If a particle is functionalized, for example, with ethylenically unsaturated groups on the surface, then the particles will react with the crosslinkable constituents of the relief-forming layer in the case of surface UVA exposure. As a result, the particle is transferred to the relief-forming layer and then stand out of the surface. Non-functionalized particles, on the other hand, are usually removed, but leave depressions in the surface.

In addition, the particles can also be preloaded / swollen with monomer, which can lead to a fixation of the particles on the surface of the layer (B). Furthermore, ethylenically unsaturated monomer can be introduced into the intermediate layer (C) in this way.

In order not to influence the transparency of the intermediate layer (C) too much, the refractive index of the particles used should be similar to that of the polymers used in the intermediate layer (C). As a rule, the refractive indices should not differ by more than ± 0.09, preferably not more than ± 0.06, more preferably not more than ± 0.05 and most preferably not more than ± 0.04.

The intermediate layer (C) may contain the particles in a concentration of 0.5 to 35 wt .-%, preferably in the range of 1 to 25 wt .-%, particularly preferably in the range of 1, 5 to 20 wt .-%.

The intermediate layer (C) may contain further constituents which facilitate the processing of the layer or impart additional properties to it. The further constituents may be, for example, additives, stabilizers, adhesion promoters, defoamers, surface-active substances, emulsifiers, dispersants, waxes and dyes. Suitable adhesion promoters are, in particular, oligomers, polymers and block copolymers and random copolymers which have an affinity for adjacent layers. In particular, basic adhesive components can be used if the neighboring layers have acidic functions and vice versa. It is also possible to use ionic polymers, one of the adjacent layers containing cationic polymers and the other layer containing anionic polymers.

Another property of the intermediate layer (C) is that it is not predominantly removed during the imaging of the mask layer (D) but remains on the relief-forming layer. Therefore, the use of materials and substances that absorb ablation electromagnetic radiation, are volatile, decompose when heated and / or generate gases or promote ablation. The relief precursor according to the invention comprises a laser-ablatable mask layer (D) arranged above the intermediate layer (C), which is also removable by solvents or by heating and adsorbing / absorbing. This layer is heated and volatilized by selective irradiation using high energy electromagnetic radiation to form a patterned mask which is used to transfer the structure to the relief precursor. For this purpose, it must be impermeable in the UV range and absorb radiation in the VIS-IR range, which leads to heating of the layer and its ablation.

The optical density of the mask layer in the UV range from 330 to 420 nm is in the range of 1 to 5, preferably in the range of 1, 5 to 4, particularly preferably in the range of 2 to 4. The optical density is determined by an X-rite 361TX densitometer in the "Density" setting with UV filter.

The optical density OD (VIS IR) of the mask layer in the VIS-IR range of 340 to 660 nm is in the range of 1 to 5, preferably in the range of 1, 5 to 4, particularly preferably in the range of 2 to 4. The optical Density is determined by measuring with an X-rite 361TX Densitometer in the Density setting.

The layer thickness M of the laserablatierbaren mask layer (D) is usually 0.1 μηη to 5 μηη. At layer thicknesses below 0.1 μm, it is difficult to achieve a sufficient optical density. At layer thicknesses of more than 5 μηη the laser sensitivity of the element is too low, so that long laser imaging times necessary. Preferably, the layer thickness is 0.3 μηι to 4 μηι, more preferably 1 μηι to 3 μηι. The laser sensitivity of the mask layer (measured as the energy necessary to ablate 1 cm ² layer) should be between 0.1 and 10 mJ / cm ² , preferably between 0.3 and 5 mJ / cm ² , more preferably between 0 , 5 and 5 mJ / cm ² .

The mask layer (D) may optionally also contain the second ethylenically unsaturated monomer. It is also possible that optionally at least one further monomer other than the first and second ethylenically unsaturated monomer is present in the mask layer. Provided that the ethylenically unsaturated monomers are soluble in the layers (A, AH, B, C, D, E, and F) and have a sufficiently high rate of diffusion, they may be present in all layers.

The mask layer (D) comprises at least a second, non-radically crosslinkable elastic polymer which is able to uniformly distribute the components which absorb the electromagnetic radiation and which is ablated as efficiently as possible when heated. The second elastic polymer may be the same polymer as the first elastic polymer or a different polymer. The second elastic polymer can be a linear, branched, star-shaped, comb-shaped, dendritic homo- or copolymer. Copolymers may be present as random and / or block copolymers. The second elastic polymer may also be a mixture of different polymers which differ, for example, in structure, monomer composition, block lengths, molecular weight functional groups, their number and / or distribution. Mixtures of polymers can also be used.

In a further embodiment, the second elastic, non-radically crosslinkable polymer has a solubility parameter of 15 to 26 (MPa) ^{/ 2} , in order to be able to dissolve the second ethylenically unsaturated monomer in a sufficient amount. In another embodiment, the first and second elastic, non-radically crosslinkable polymers have a solubility parameter of 15 to 26 (MPa) ^{/ 2} . In an additional embodiment, the first and second elastic non-radically crosslinkable polymers may also have a solubility parameter of 15 to 26 (MPa) ^{/ 2} . The values of some polymers are listed in Polymer Handbook by J. Brandrup, EH Immergut and EA Grulke, 4th Edition, Wiley-Interscience, 1999. Ethylene vinyl acetates, flexible polyamides, flexible polyurethanes, nitrocellulose, polyvinyl acetals such as, for example, poly (vinyl butyralvinyl alcohol) copolymers (or polyvinylvinyl butyralvinylethyralvinyl alcohol) copolymers are readily suitable, non-radically crosslinkable, elastic polymers for the mask layer (D) It is also possible to use other flexible materials as binders, such as partially hydrolyzed polyvinyl acetates Preferred binder for the mask layer (D) is a flexible polyamide, a polyvinyl alcohol, a partially saponified polyvinyl acetate or a partially saponified polyvinyl acetal The mask layer (D) can be permeable to oxygen or it is preferably permeable to oxygen in the case of an oxygen-impermeable intermediate layer (C), and both layers (C) and (D) may be impermeable to oxygen Elv forming (B) layer, the intermediate layer (C) and the ablatierbaren mask layer (D) is that they are soluble in the common, commercially available liquids (washing agents), which are usually composed of solvent mixtures or aqueous solutions. These washout agents consist of one or more non-polar hydrocarbon solvents as the main constituent and a moderately polar alcohol, for example benzyl alcohol, n-pentanol, cyclohexanol, ethylhexanol or heptyl alcohols, as a minor constituent. Aqueous solutions usually contain surfactants and / or flocculants and generally have a pH> 7. The relief-forming layer (B) can be processed in these washout agents in conventional times. Up to a solids content of at least 5% by weight, no contamination of the washout devices and no settling of solids in the washout solution are observed.

Furthermore, the relief-forming layer (B), the intermediate layer (C) and the ablatable mask layer (D) can also be thermally developed or removed (see, for example, EP 1 239 329 or EP 1 170 121). Here, the relief structures are heated to the softening or melting temperature after the imagewise exposure. The unexposed and non-crosslinked areas of the relief structure thereby become partially liquid and sticky and are then removed continuously by absorption with a fleece or a fabric.

In a further embodiment, the surface of the relief after removal of the layers and the uncrosslinked regions has a roughness Rz of less than 20 μm, preferably less than 18 μηη, more preferably less than 15 μηι on. The roughness is determined using a Marahr M 300 mobile roughness tester from the Mahr company using the "MarWin XR20" software (V 4.26) using a scanning speed of 0.5 mm / s and a measuring force of 0.00075 N.

Furthermore, in one embodiment, a finished relief structure (after removing the layers C and D, the uncrosslinked areas and optionally after a post exposure) has a hardness in the range of 20 to 100 ° Miko-Shore A preferably in the range of 30 ° to 90 °, more preferably in the range of 40 ° to 90 ° and most preferably in the range of 50 ° to 85 °.

In a further embodiment, in the relief precursor according to the invention between layer (B) and (C) or between layer (C) and (D) there is a further layer (F) which is impermeable to oxygen. When an oxygen-impermeable layer (F) is present, layers (B), (C) and / or (D) are preferably permeable to oxygen. The layer thickness of the layer (F) is in the range of 3 to 5 μηη. In addition to additives, the layer mainly contains one or more elastic polymers which have a low oxygen permeability, these having an oxygen permeability with a value of less than or equal to 1.5 ^* 10 ⁵ cm ² m / (m ^{2 *} d ^* bar). Preferably, the polymers in the layer (F) are also not free-radically crosslinkable.

Suitable elastic polymers which are soluble in organic solvents and / or can be thermally developed and have a sufficient barrier effect against oxygen are, for example, partially hydrolyzed polyvinyl acetates having a degree of saponification between 30 and at most 80 mol%, ethylene-vinyl acetate copolymers and ethylene-vinyl alcohol Copolymers and ethylene-vinyl acetate-vinyl alcohol copolymers. Also suitable are cyclic acetals of polyvinyl alcohol such as polyvinyl butyral, polyvinyl ethyral, polyvinyl formal, polyvinyl propyral and copolymers containing two or more different vinyl acetal units selected from vinylformal, vinylethyral, vinylpropyral and vinylbutyral units. The polyvinyl acetals are always copolymers with vinyl alcohol units, since the conversion of polyvinyl alcohol to the full acetal is not complete for statistical and steric reasons. For example, poly (vinyl butyral) is a poly (vinyl butyralvinyl alcohol). Usually, the residual OH content of said polyvinyl acetals is between 10 and 30% by weight. Vinylethyralvinylbutyral-vinyl alcohol copolymers (poly (vinylethyralvinyl butyral), for example, are very suitable. In a preferred embodiment, the layers (D) and if present (F) also contain at least one second ethylenically unsaturated monomer, wherein in both layers the same or different monomers may be present. These are the ethylenically unsaturated monomers described for layer (C), which may be present in concentrations described for layer (C).

The invention also provides a process for producing a relief precursor according to the invention, comprising applying the above-described layers to a support. This method generally comprises the steps of: a) providing a dimensionally stable carrier (A),

b) optionally cleaning the carrier (A),

c) applying the relief-forming layer (B), the intermediate layer (C), the mask layer (D) and optionally the layer (F),

d) optionally further treatment of the layer composite,

e) optionally applying the cover layer (E),

f) optionally further treatment of the layer structure.

In step a), a dimensionally stable carrier (A) is provided, which is optionally additionally coated with further layers, e.g. a bonding agent layer (AH) may be provided.

In the optional step b), the surface of the carrier will be cleaned. In the process dust and foreign particles as well as surface contaminants that impair adhesion (such as fingerprints) are removed. For use, all methods familiar to the person skilled in the art can be used here, such as, for example, brushing, blowing off, wiping (with and without solvent), rinsing off and any combinations thereof. In general, such a cleaning is carried out.

In step c) the layers (B), (C) and (D) and optionally (F) are applied, wherein between the application of individual layers further process steps can be carried out, such as drying, irradiation or spraying and suitable combinations thereof. Layer (F) can be applied between (B) and (C) or between (C) and (D). The layers are usually applied in liquid form, in which case not only solutions but also melts are used. For individual layers, it may also be advantageous to apply them to additional carriers and to apply such composites in dry or solid form. The application of the layers can be carried out by all methods familiar to the person skilled in the art, such as, for example, wise laminating, laminating, pouring, dipping, spraying and suitable combinations thereof. It may be necessary for the solutions, melts and / or layers to be heated or cooled. Depending on the application methods, it may be necessary to carry out further treatments of the layer structure in step d). In particular, when liquid or solvent-containing mixtures are applied, it may be necessary for drying steps to be carried out by heating the layer composite or by evaporating off solvent. Furthermore, it may be necessary to treat the layer structure mechanically, for example by rolling or pressing. In addition, it may be advantageous to irradiate the layer structure at this stage of at least one side, which is correspondingly transparent, with electromagnetic waves.

In step e) the protective layer (E) is optionally applied, whereby the methods already mentioned above can be used. In step f) optionally further treatments may be added, which are advantageous for further processing. These include, for example, exposure to electromagnetic radiation from at least one of the two sides of the layer structure (which is correspondingly transparent), optical quality control for defects and / or contamination, trimming into predetermined formats, thermal treatment, packaging, storage, and any Combinations of it.

The present invention also provides a process for producing relief structures using a relief precursor according to the invention, comprising the steps of: i) providing a relief precursor according to the invention;

ii) optionally cleaning the relief precursor;

iii) optionally irradiation with electromagnetic radiation from a first side; iv) optionally removing the cover layer (E);

v) imagewise removal of the mask layer (D);

vi) exposing the relief precursor through the mask layer (D) with ^Λ electromagnetic radiation;

vii) removing layers (C), (D) and optionally (F) and the non-crosslinked regions of layer (B); and

viii) optionally further treatment steps. In the first step i) the relief precursor described above is provided. This can optionally be purified in step ii), using any of the methods familiar to the person skilled in the art, such as, for example, brushing, blowing off, wiping (with and without solvent), rinsing off and any combinations thereof.

In optional step iii), the relief precursor of at least one side can be irradiated over a large area with electromagnetic radiation. This irradiation preferably takes place from the side of the relief precursor which lies opposite the mask layer, in order to achieve a capping of the relief structure to be produced (back-side exposure). Preferably, this backside exposure is carried out by transparent dimensionally stable materials such as polymer films and in particular polyester films as support material. For non-transparent substrates, step iii) is omitted. The wavelength of the irradiated electromagnetic radiation is in the range of 200 to 2000 nm, preferably in the UV range, more preferably in the range of 200 to 550 nm, most preferably in the range of 300 to 450 nm. In addition to broadband irradiation of the electromagnetic waves It is advantageous to use narrowband or monochromatic wavelength ranges, such as can be generated using appropriate filters, lasers or light emitting diodes (LEDs). In these cases, wavelengths in the ranges 350, 365, 385, 395, 400, 405, 532, 830, 1064 nm individually (and about 5-10 nm above and / or below) or as combinations are preferred. In the presence of a covering layer (E), this can be removed in optional step iv), which is possible both mechanically and chemically by treatment with solvents, water or aqueous solutions. Preferably, the cover layer is a protective film and is peeled off. In step v), the imaging of the mask layer takes place either by removal of the layer and / or a spatially resolved change in the absorption and / or reflection properties so that the mask layer becomes at least partially transparent in the wavelength range used for imaging. Preferably, the mask layer is ablated by means of high-energy laser, wherein laser beams are computer-controlled guided over the mask layer. In this case, mainly IR lasers with wavelengths in the range of 500 to 20,000 nm, preferably in the range of 800 to 10,000 nm, particularly preferably in the range of 1000 to 2000 nm are used. In particular, wavelengths around 830 nm, 980 nm, 1064 nm and 10.6 μm or combinations thereof are preferred.

By exposing the relief precursor with electromagnetic radiation in step vi) through the layers (C) and (D) and optionally (F) is in the areas of the layer (B), which lie under the exposed surfaces of the layer (D), triggered a reaction that leads to the crosslinking of the constituents present in the layer. Through this networking, these areas are stabilized and can not be removed in the later development step. The irradiation generally takes place over a large area, but can also be carried out over a small area (approximately point-like) by means of guided laser beams or spatially resolved projection of electromagnetic radiation. The electromagnetic radiation used for exposure has wavelengths in the range of 200 to 2000 nm, as already described above. The irradiation can be continuous, pulsed or in several short periods with continuous radiation. The intensity of the radiation can be varied over a wide range, it being ensured that a dose is used which is sufficient to sufficiently crosslink the layer (B) for the later development process. The radiation-induced reaction must, if appropriate, have progressed so far after further thermal treatments that the exposed areas become at least partially insoluble and thus can not be removed in the development step vii). Intensity and dose of the radiation depend on the reactivity of the formulation and the duration and efficiency of the development. The intensity of the radiation is in the range from 1 to 15,000 mW / cm ² , preferably in the range from 5 to 5000 mW / cm ² , particularly preferably in the range from 10 to 1000 mW / cm ² . The dose of radiation is in the range of 0.3 to 6000 J / cm ² , preferably in the range of 3 to 100 J / cm ² , more preferably in the range of 6 to 20 J / cm ² . The action of the energy source can also be carried out in an inert atmosphere, for example in noble gases, C0 ₂ and / or nitrogen or under a liquid which does not damage the multilayer element.

In step vii), the layers (C), (D) and, if present, the layer (F) and non-crosslinked areas of the layer (B) are removed to produce the relief. The layers can be removed individually or in groups or all together and simultaneously. Preferably, all layers and the non-crosslinked regions of (B) are removed in a single step. Depending on the nature of the layers, this can be done both mechanically and chemically by treatment with washout agents, such as organic Solvents, mixtures thereof, water, aqueous solutions or aqueous-organic solvent mixtures which are capable of dissolving, emulsifying and / or dispersing non-crosslinked areas in the layer (B). In this development step, all methods familiar to the person skilled in the art can be used. The solvents or their mixtures, the aqueous solutions as well as the aqueous-organic solvent mixtures may contain auxiliaries which stabilize the formulation and / or increase the solubility of the components of the non-crosslinked regions. Examples of such auxiliaries are emulsifiers, surfactants, salts, acids, bases, stabilizers, corrosion inhibitors and suitable combinations thereof. For development with these solutions, any methods known to the person skilled in the art may be used, such as, for example, dipping, washing or spraying with the development medium, brushing in the presence of development medium and suitable combinations thereof. Preference is given to developing with neutral aqueous solutions or water, the removal being assisted by means of rotating busts or a plush pile. Another way to influence the development is to control the temperature of the developing medium and, for example, to accelerate development by increasing the temperature. In this step, further layers which are still present on the radiation-sensitive layer can be removed if these layers can be detached during development and sufficiently dissolved and / or dispersed in the developer medium.

When organic solvents are used, preference is given to using those which have a high flash point which is above a temperature of 40 ° C., particularly preferably above 60 ° C. The flash point may be above 100 ° C in special cases.

Conventional washout agents are described, for example, in EP 332,070. In general, these contain aliphatic, cycloaliphatic or aromatic hydrocarbons and one or more alcohols. Most of the washing agents used in the market contain non-polar hydrocarbons as the main component and medium polar alcohols in an amount of 10 to 30% by weight. Examples of commercial washout agents include mixtures containing about 40% by weight of high boiling point hydrocarbon solvents, about 40% by weight of decalin and about 20% by weight of n-pentanol, mixtures containing about 50% by weight of high boiling point hydrocarbons, ca. 20 wt .-% diisopropylbenzene and about 30 wt .-% cyclohexanol, mixtures containing about 56 wt .-% decalin, about 27 wt .-% aliphatic hydrocarbon solvent, about 12 wt .-% benzyl alcohol and about 2 wt .-% ethylhexanol and mixtures containing about 70 wt .-% of aromatic hydrocarbons and about 30 wt .-% heptyl alcohols. In some cases, terpenes and other components are additionally used, as described, for example, in US 2016/0054656.

In the case of the aqueous washout agents, in addition to tap water, aqueous solutions are used which contain further constituents, for example dispersants, emulsifiers, acids, bases, flocculants, salts and usually have a pH of> 7. As dispersants and / or emulsifiers, cationic, anionic or nonionic substances or combinations thereof are used. Examples of anionic compounds are carboxylates such as sodium laurate or sodium oleate, sulfuric acid ester salts such as sodium lauryl sulfate, sodium cetyl sulfate, sodium oleyl sulfate, alkyl sulfonates, phosphoric acid esters or block copolymers with polar and non-polar blocks. As organic and inorganic acids, for example, sulfuric acid, nitric acid, phosphoric acids, formic acid, acetic acid, carboxylic acids, oxalic acid, citric acid, maleic acid or p-toluenesulfonic acid can be used. Examples of bases are alkali and alkaline earth hydroxides, such as LiOH, KOH, NaOH or CaOH. Water-solvent mixtures are often used which allow the use of the polymer whose water solubility is lower. Examples of solvents are methanol, ethanol, isopropanol, benzyl alcohol, cyclohexanol, cellosolve, glycerol, polyethylene glycol, dimethylformamide, dimethylacetamide and acetone. In a further embodiment, the removal of the layers (C), (D) and, if present, the layer (F) and the non-crosslinked regions of the layer (B) in step vii) takes place thermally, ie by introducing heat and removing the softened or partially liquefied material of the layers. The heating of the exposed relief precursor may be carried out by any means known to those skilled in the art, such as by irradiation with IR light, exposure to hot gases (eg air), hot rollers or any combination thereof. To remove the (viscous) liquid areas, it is possible to use all methods and methods familiar to the person skilled in the art, such as blowing off, suction, blotting, blasting (with particles and / or droplets), stripping, wiping, transfer to a developing medium and any desired combinations from that. Preferably, the liquid material is taken up (absorbed and / or adsorbed) by a developing medium which is continuously contacted with the heated surface of the relief precursor. The process is repeated until the desired relief height is reached. As development media papers, fabrics, nonwovens and films can be used, which can accommodate the liquefied material and can consist of natural and / or plastic fibers. Preferably, nonwovens or nonwoven fibrous webs of polymers such as celluloses, cotton, polyesters, polyamides, polyurethanes and any combinations thereof are used which are stable at the temperatures used in development.

Optionally, following the previous steps, further treatment steps (viii) can be carried out. These include, for example, thermal treatment, drying, treatment with electromagnetic radiation, with plasma, with gases or with liquids, attachment of identification features, cutting, coating and any combinations thereof. A thermal treatment can be used, for example, to start and / or complete reactions, to increase the mechanical and / or thermal stability of the relief structure and to remove volatile components. For thermal treatment, the known methods can be used, such as heating by heated gases or liquids, IR radiation and any combinations thereof. This can be ovens, blowers, lamps and any combination thereof and used. With the treatment with gases, plasma and / or liquids, not only detackification but also surface modifications can be accomplished, in particular if reactive substances are additionally used. For example, treatment with electromagnetic radiation may be used to render the surfaces of the relief structure tack-free, initiate and / or complete the polymerization and / or crosslinking reactions. The wavelength of the irradiated electromagnetic waves is in the range of 200 to 2000 nm, as already described above.

In a further embodiment, the relief structures produced can be used as printing plates, in particular as flexographic printing plates, letterpress printing plates, pad printing plates and gravure printing plates. Likewise, the relief structures can be used as optical components, for example as a Fresnel lens.

If at least one further layer is applied to the relief structures produced, which is so stiff that it does not follow the shape of the relief, arise Components with channels and / or cavities, which may be separated or interconnected. For this, the further layer may be stiff or inflexible, so that it does not sink into the depressions, but flexible layers can also be used if suitable measures are taken to ensure that the further layer can not sink into the depressions (for example, in FIG the wells are filled with liquids and / or gases and then removed). These channels and / or cavities may optionally be provided with other materials and / or liquids. Such components can be used as a microfluidic component (eg for microanalysis and / or for high throughput screening), as a microreactor, optical component, for example as a phoretic cell (as shown, for example, in WO2004 / 015491), as a light-controlling element for color representation (as in WO2003 / 062900) or as photonic crystals. The further layer can be applied, for example, during the aftertreatment according to step viii). The abovementioned components and components can be designed to be both rigid and / or flexible. Flexible embodiments are particularly preferred if they are to be worn on and / or in the body and / or used in fabrics and / or garments.

The invention thus also relates to the use of the relief precursor according to the invention as a pad printing plate, flexographic printing plate, letterpress printing plate, gravure printing plate, microfluidic component, microreactor, phoretic cell, photonic crystal and optical component.

The invention is further illustrated by the following examples.

Examples

Determination of micro-shore A hardness

The Micro-Shore A hardness was measured on samples with a thickness of 1.7 mm and after exposure, development, drying and after-exposure with a digi test II-M Shore A measuring instrument (Bareiss Prüfgerätebau GmbH), which was placed in the test stand BS 09 (Bareiss Prüfgerätebau GmbH) was installed and controlled by the control unit DTAA (Bareiss Prüfgerätebau GmbH). The measuring head (indenter with 35 ° angle) was placed on a solid surface for the measurement and pressed by the digi test II analyzer with a contact force of 235 mN and read after 3 s, the hardness value. Two measurements were made and the arithmetic mean was formed. The measurements were carried out on the basis of DIN ISO 7619. Perthometer measurements to determine the roughness:

 The perthometer measurements were carried out with a Marahr M 300 mobile roughness tester from Marahr with the software "MarWin XR20" (V 4.26) using a scanning speed of 0.5 mm / s and a measuring force of 0.00075 N.

Oxygen permeation measurements:

The oxygen permeability is determined by the carrier gas method according to ASTM D3985 in devices from Mocon Inc. With coulometric sensor. Determined at 23 C and 0% relative humidity. The samples were measured free-standing, the measuring surface is 5 cm ² or 10 cm ² and the sample thickness is between 75 and 108 μηη.

UV-VIS measurement:

 For transparency measurement, the layer constituents were dissolved in a suitable solvent mixture and applied to a transparent PET film (thickness 125 μm). Subsequently, the composite was dried for 30 minutes in a drying oven at 1 10 ° C. The transparency measurement was carried out with a Varian Cary 50 Coric UV-VIS spectrometer with Cary Win UV software version 2.00 (25). For this purpose, the values of the uncoated PET film were subtracted as a reference / baseline. Measurements were made in the wavelength range between 500 and 350 nm.

Determination of cupping:

 To determine the cupping, the 50% rasters were measured at 146 lpi using a Marahr M 300 mobile roughness tester from Marahr with the "MarWin XR20" software (V 4.26), with a scanning speed of 0.5 mm / s and a measuring force of 0.00075 N. Next, the shape of the individual halftone dots was analyzed and a difference value between the height of the edge and the center of the dots was determined, which is referred to as cupping and given in μηη, in each case 3 points were measured and the arithmetic mean Analysis of the fluting:

For the analysis of the fluting a selected motifs of the resolution was 2540 dpi, each with different precursors of the thick type 394 on a Bobst FFG 1228 NTRS Rapidset at a rate of 1 10 m / min using an anilox roll with a cell volume of 15 cm ³ / m ² printed. A paint of Siegwerk (black) with a viscosity of 21 s was used. On these motifs the washboard effect was assessed and divided into different classes. Motives with strong Fluting got the class "-", with middle the class "0" and with less fluting the category "+".

Determination of the content of the ethylenically unsaturated monomer in the intermediate layer:

To determine the content of the ethylenically unsaturated monomer, here exemplified by the HDDA content, the intermediate layer without laser-ablatable mask layer was applied to the photopolymer by extrusion and left there for 4 weeks. Subsequently, the intermediate layer was peeled off together with the cover sheet. 318 cm ^{2 of} the film with the layer was placed in 100 g of ethanol to dissolve the HDDA and the layer binder. By differential weighing the cover sheet with the layer and the film without a layer, the basis weight of the intermediate layer was determined. Subsequently, a calibration curve was generated by GC analysis by measuring various concentrations of a standard solution with a defined HDDA content (1.009 g in 20 ml ethanol) and determining the HDDA content of the solution. With the HDDA content of the solution and the basis weight of the intermediate layer, the HDDA content in the layer was calculated according to the following formula

Proportion HDDA in sample length 3] * Size of sample size.ge [ml]

 .m l

determined surface weight \ ^S use

ΎΐΙ 2 * th area [m ² ] calculated. GC studies were performed on a Perkin Elmer Clarus 500 with a TurboMatrix 40 sampler and TotalChrom software (version 6.3.2). For sample measurement, 1 μΙ of the prepared extraction solution was injected at normal injection rate. The temperatures of the detectors were 200 and 310 ° C. The measurement was carried out for 28.5 minutes at a data rate of 12.5 pts. The individual components were separated on a Perkin Elmer Elite Series column (Perkin Elmer; PE17-HT, N931 -6264 with a length of 30 m and 0.25 mm inner diameter and a 0.15 μηη film). The carrier gases used were compressed air and hydrogen. The gas flow rate was 450 ml / min for compressed air and 45 ml / min for hydrogen.

Example 1 :

Preparation of Sheet-like Materials: A Photopolymeric Composition Containing 73.75 Parts of a SIS Block Copolymer (SIS Triblock, Having a Styrene Content of 14 to 15%). 7-8%) as binder, 9.3 parts of hexanediol diacrylate (HDDA), 3.3 parts of hexanediol dimethacrylate, 5 parts of diisononyl cyclohexane-1, 2-dicarboxylate as a plasticizer and a diblock fraction of about 26% 5 parts Vinyltoluolmethylstryryl- copolymer as extrusion aid and 2.5 parts of benzil dimethyl ketal as a photoinitiator and 1, 25 parts of other ingredients such as inhibitors and dyes was melted at elevated temperatures (120 to 180 ° C) in the extruder and a slot die between a cover sheet with laserablatierbarer mask layer and optionally an intermediate layer containing 71 parts of polyvinyl butyral (OH content 18-21%, 14-20 mPas as 10% ethanolic solution), 15 parts of an inorganic, siliceous filler and 5 parts of an adhesion-promoting component and etylenic unsaturated monomer (HDDA) and had a thickness of 100 μηη, and calendered a support film having a thickness of 125 μηη, so that the Reli efvorläufer (photopolymer + films) had a thickness of 1855 μηη. The oxygen permeability of the intermediate layer was 6 ^* 10 ⁴ cm ^ m / (m ^{2 *} d ^* bar).

By laser ablation different tone value fields were generated on the precursors between 1 and 100% area coverage with a screen resolution of 146 lpi. The ablation was performed using a ThermoFlexx Laser (Xeikon) Software Multiplate (version 5.0.0.309) and the following parameters: wavelength 1064 nm, 10.5 revolutions per second, 35 W laser power. The UV exposure was carried out with a Combi FIII imager (Flint Group) using tube light of intensity 13 mW / cm ² (solvent development) for 15 min and 24 mW / cm ² for 10 min (thermal development). Development then proceeded with solvent in a Flll scrubber (Flint Group) at 35 ° C using nylosolv A (Flint Group) as developing solution. The drying was carried out for 2 hours at 60 ° C and it was post-exposed simultaneously with 10 minutes UVA and 5 minutes UVC in a Combi FIII platesetter (Flint Group). Alternatively, part of the samples were sampled with a nyloflex Xpress FIV instrument (Flint Group, thermal development at a temperature of 163 ° C (325 ° F) and 14 revolutions at a pressure of 4.13 bar (60 psi) and a speed of 0 , 7 7s, and post-exposed simultaneously with 10 minutes of UVA and 6 minutes of UVC in a Combi FIII (Flint Group).

From the finished relief structures samples were taken from the 50% grid and the cupping measured (Table 1 a). Example Intermediate Cupping depth Cupping depth Micro thickness of the HDDA layer in solvent-thermal Shore Intermediate development Development A layer (normalized to (normalized to (m)

 Example a1) Example a1

 thermal)

 Example No 0% 1 1, 65.4

1 a

 Example Yes 7 ± 2 0.87 0.59 65.8 4 ± 1 1 b

 Example Yes 9 ± 1% 0.82 0.43 65.1 4 ± 1 1 c

 Example yes 0 1 1, 65.4 4 ± 1 1 d

As can be seen from the above table, the cupping is reduced by the monomer in the intermediate layer. The best result is achieved with 9% HDDA in the intermediate layer and thermal development, but even lower concentrations cause a significant reduction. Presumably, cupping is reduced because monomer can also diffuse from the intermediate layer into the exposed areas from above, not just from the unexposed areas of the page.

Example 2:

Preparation of plate-like materials: A photopolymeric mixture containing 65 parts of a SBS block copolymer (SBS triblock, having a styrene content of 31% and a diblock content of about 17%) as a binder, 6.5 parts of hexanediol diacrylate, and 2.5 parts of benzil dimethyl ketal Photoinitiator, 1 part of other ingredients such as inhibitors and dyes and 25 parts of a polybutadiene (vinyl content 2%, M _n = 5000 g / mol) as a plasticizer was melted at elevated temperatures (120-180 ° C) in the extruder and a slot die between a cover film with laserablatierbarer mask layer and optionally an intermediate layer containing 90 parts of polyvinyl butyral (OH content 18 to 21%, 14 to 20 mPas measured as 10% ethanolic solution), 4 parts of a coupling agent and optionally 6 parts of monomer (HDDA) and had a thickness of 100 μηη, and calendered a support film with a thickness of 125 μηη, so that the relief precursor (photopolymer + films) egg ne strength of 4100 μηη had. The oxygen permeability of the intermediate layer was 5.8 ^* 10 ⁴ cm ^ m / (m ^{2 *} d ^* bar). By laser ablation, different tone value fields of between 1 and 100% area coverage with a screen ruling of 146 lpi and various images were produced on the precursors. The ablation was performed using a ThermoFlexx Laser (Xeikon) Software Multiplate (version 5.0.0.309) and the following parameters: wavelength 1064 nm, 10.5 revolutions per second, 35 W laser power. The exposure was carried out with a Combi FIII imager (Flint Group) using tube light of intensity 24 mW / cm ² for 10 min. The development was carried out in a Flll scrubber (Flint Group) at 35 ° C using nylosolv A (Flint Group) as a developing solution. The drying was carried out for 2 hours at 60 ° C and it was post-exposed simultaneously with 10 minutes UVA and 4 minutes UVC in parallel in a Combi FIII platesetter (Flint Group).

The print results show that the use of a monomer-containing interlayer can significantly reduce fluting. The HDDA in the interlayer probably leads to a better and more uniform cross-linking at the cliché surface, which is able to compensate for the fluctuations in the substrate in the corrugated board.

Example 3:

The relief precursors were prepared according to the procedure described above (Example 1) with an HDDA content of 7 ± 2% and developed by solvent washing. For the experiments in this example, different polymers were used as binders of the intermediate layer:

• PVA: OH content 71 mol%, 5 to 73.5%, 5.6-6.6 mPas as 4% aqueous solution

 • PVB: OH content 18 to 21 mol%, 14 to 20 mPas as 10% ethanolic solution

• PA: softening point 130 to 155 ° C, MFR at 175 ° C: 5 to 15 g / 10 min, cold flexibility - 40 ° C

Example 4:

The relief precursors were prepared according to the procedure described above (Example 2) with an HDDA content of 7 ± 2%. For the experiments in this example, different polymers were used as binders of the intermediate layer:

BUNA S, styrene content 30 mol%, (comparative example, crosslinkable polymer)

PU: Aromatic polyisocyanate based on tolylene diisocyanate-toluene diisocyanate, NCO content 12 mol%, equivalent weight about 350

 • PVB: OH content 18 to 21 mol%, 14 to 20 mPas as 10% ethanolic solution

• PA: softening point 130 to 155 ° C, MFR at 175 ° C: 5 to 15 g / 10 min, cold flexibility -40 ° C

Ethyl cellulose: ethoxyl content 48 to 49.5 mol%, 90 to 110 mPas as 5% solution in 80% toluene and 20% ethanol

Claims

Flint Group Germany GmbH October 5, 2018 DS71003PC Patentansprüche

1 . Digitally imageable, photopolymerizable relief precursor at least comprising, arranged one above the other in the stated order,

 (A) a dimensionally stable carrier;

 (AH) optionally an adhesion-promoting layer;

 (B) a relief-forming layer, at least comprising a crosslinkable elastomeric binder, a first ethylenically unsaturated monomer and a photoinitiator;

 (C) at least one intermediate layer, at least containing a first, not radically crosslinkable elastic polymer;

 (D) a laser ablatable mask layer, at least comprising a second, non-radically crosslinkable elastic polymer, a UVA light absorbing material and an IR light absorbing material; and optional

 (E) a peelable topcoat;

 characterized in that layer (C) and optionally layer (D) contain at least one second ethylenically unsaturated monomer and in that the concentration of the first ethylenically unsaturated monomer in layer (B) and the concentration of the second ethylenically unsaturated monomer in intermediate layer ( C) differ by a maximum of ± 2 wt .-%, each based on all components of the layers (B) and (C).

2. relief precursor according to claim 1, characterized in that the layer thickness S of the intermediate layer (C) in from 0.1 to 30 μηη.

3. Relief precursor according to claim 1 or 2, characterized in that the first and the second ethylenically unsaturated monomer are the same ethylenically unsaturated monomer.

4. relief precursor according to one of claims 1 to 3, characterized in that the second ethylenically unsaturated monomer in the intermediate layer (C) in a Concentration K is equal to or lower than the concentration of the first ethylenically unsaturated monomer in the relief-forming layer (B).

5. relief precursor according to one of claims 1 to 4, characterized in that the second ethylenically unsaturated monomer in the intermediate layer (C) in a

Concentration K of 0.1 to 25 wt .-%, based on all components of the intermediate layer (C), is present.

6. relief precursor according to one of claims 1 to 5, characterized in that the ratio of the layer thickness S of the intermediate layer (C) in μηη to the

Concentration K of the first ethylenically unsaturated monomer in wt .-% of 30: 0.1 to 0.1: 25 m / wt .-% is.

7. Relief precursor according to one of claims 1 to 6, characterized in that the first and the second ethylenically unsaturated monomer have at least 2 ethylenically unsaturated groups and a molecular weight of less than 600 g / mol.

8. relief precursor according to one of claims 1 to 7, characterized in that the first elastic, not radically crosslinkable polymer a

Solubility parameter of 15 to 26 (MPa) ^{/ 2} has.

9. relief precursor according to one of the claims 1 to 8, characterized in that the first and the second elastic, not radically crosslinkable polymer have a solubility parameter of 15 to 26 (MPa) ^{/ 2} .

10. relief precursor according to one of the one of the claims 1 to 9, characterized in that the first elastomeric, not radically crosslinkable polymer in the intermediate layer (C) an oxygen permeability of less than or equal to 1, 5 ^* 10 ⁵ cm ^ m / (m ^{2 *} d ^* bar).

1 1. Relief precursor according to one of claims 1 to 9, characterized in that the first elastomeric, non-radically crosslinkable polymer in interlayer (C) has an oxygen permeability greater than 1.5 ^* 10 ⁵ cm ² m / (m ^{2 *} d ^* bar) having.

12. relief precursor according to one of claims 1 to 1 1, characterized in that the intermediate layer (C) the first elastomeric, not radically crosslinkable polymer in a concentration of 60 to 99 wt .-%, based on all components of the intermediate layer (C) , contains.

13. relief precursor according to one of claims 1 to 12, characterized in that the intermediate layer (C) contains particles having a particle size of 0.2 to 30 μηη.

14. relief precursor according to one of claims 1 to 13, characterized in that the intermediate layer (C) contains particles in a concentration of 0.5 to 35 wt .-%, based on all components of the intermediate layer (C).

15. relief precursor according to any one of claims 13 or 14, characterized in that the particles contain the second ethylenically unsaturated monomer.

16. relief precursor according to one of claims 1 to 15, characterized in that between the reliefbinding layer (B) and the intermediate layer (C) or between the intermediate layer (C) and the mask layer (D) another layer (F), the is impermeable to oxygen.

17. Relief precursor according to claim 16, characterized in that the layer (F) contains a second ethylenically unsaturated monomer.

18. Relief precursor according to one of claims 1 to 17, characterized in that the mask layer (D) contains a second ethylenically unsaturated monomer.

19. A method for producing relief structures comprising the following steps:

 i) providing a relief precursor as defined in any one of claims 1 to 18;

 ii) optionally cleaning the relief precursor;

 iii) optionally irradiation with electromagnetic radiation from a first side;

 iv) optionally removing the cover layer (E);

 v) imagewise removal of the mask layer (D);

vi) exposing the relief precursor through the mask layer (D) with electromagnetic radiation; vii) removing the layers (C), (D) and optionally (F) and the non-crosslinked regions of the layer (B).

20. The method according to claim 19, characterized in that step vii) is carried out with a washout agent.

21. Process according to claim 19, characterized in that step vii) takes place thermally.

22. Use of the relief precursor as defined in any one of claims 1 to 18 as a pad printing plate, flexographic printing plate, letterpress printing plate, gravure printing plate, microfluidic component, microreactor, phoretic cell, photonic crystal and optical component