Photopolymerizable relief precursors with tunable surface properties

Abstract

The present invention further relates to a method for producing a relief structure, the method comprising: (A) a dimensionally stable carrier; (B) a photopolymerizable relief-forming layer comprising at least a crosslinkable elastomeric binder, an ethylenically unsaturated monomer, a migratable surface-active additive, a UVA light-activatable photoinitiator, and a UVC light-activatable photoinitiator.

Description

[Technical Field]

[0001] The present invention relates to photopolymerizable relief precursors having surface properties that can be tuned by exposure conditions, methods for generating relief structures from the relief precursors, the relief structures themselves and uses thereof. [Background technology]

[0002] Printing with solvent-based inks requires a printing plate with an inked surface to prevent ink from flowing into the interstitial spaces between the image dots. This is typically achieved by the presence of a mobile surface-active additive (MSA) in the relief layer, which reduces the surface tension of the printing surface. However, the presence of this additive can be problematic when printing with UV-curable or water-based inks, for example, due to poor ink transfer in the solid areas. Therefore, various printing plates are used for printing with solvent-based inks, UV-curable inks, or water-based inks. Examples of such printing plates are shown in EP 1014194, but such printing plates are only suitable for certain types of solvent-based inks. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present invention to provide a printing plate that is "switchable" so that its surface properties can be adjusted by exposure parameters, so that the same printing plate can be used universally for different application fields. The requirements for a printing plate printing with solvent-based inks are different from those for printing with UV-cured or water-based inks. [Means for solving the problem]

[0004] This object is achieved with a photopolymerizable relief precursor comprising: (A) a dimensionally stable carrier; (B) a photopolymerizable relief-forming layer comprising at least a crosslinkable elastomeric binder, an ethylenically unsaturated monomer, a migratable surface-active additive, a UVA light-activatable photoinitiator, and a UVC light-activatable photoinitiator. [Effects of the Invention]

[0005] The relief precursor of the present invention allows for control of MSA migration to the surface through the selection of exposure parameters. It is believed that MSA tends to diffuse to the surface of the relief layer, thereby rendering this surface hydrophobic. Exposure to UVA light to a deeper penetration depth ensures greater crosslinking throughout the relief layer, stabilizing the entire relief. Exposure to UVC light reduces the depth of penetration into the photoactive layer, ensuring excellent re-crosslinking of still-present monomers and polymers. This reduces or prevents MSA migration to the surface of the relief, resulting in a more hydrophilic surface. This allows the printing area to be wetted with hydrophilic printing inks. UVC exposure can also cause oxidation of formulation components, leading to the formation of polar and hydrophilic groups.

[0006] The relief precursor according to the invention used as a printing plate makes it possible, inter alia, to realize the following advantages:

[0007] Surface properties can be tailored to prevent or reduce the flow of solvent-based ink into the gaps between the screen dots during printing, thereby extending the printing time before the plate needs to be cleaned.

[0008] By tailoring the surface properties, the stickiness of the surface and therefore the tendency of the surface to accumulate dust and dirt can be reduced.

[0009] The same printing plate can be used to print with different types of printing inks, in that the surface properties can be adjusted by selecting the re-exposure conditions so that the printing plate is suitable for printing with solvent-based inks, water-based inks or UV-curable inks. [Brief explanation of the drawings]

[0010] [Figure 1] Figure 1 shows the change in gloss in gloss units (GU) as a function of days for various re-exposure times. [Figure 2] Figure 1 shows the change in gloss in gloss units (GU) as a function of days for various re-exposure times. [Figure 3] Figure 1 shows the change in gloss in gloss units (GU) as a function of days for various re-exposure times. [Figure 4] The integrals of the IR bands at 719 and 729 cm −1 after 7 days at the given re-exposure times are shown. [Figure 5] The integrals of the IR bands at 719 and 729 cm −1 after 7 days at the given re-exposure times are shown. [Figure 6] The integrals of the IR bands at 719 and 729 cm −1 after 7 days at the given re-exposure times are shown. DETAILED DESCRIPTION OF THE INVENTION

[0011] Dimensionally stable carrier materials, which may optionally have additional layers, can be used as the dimensionally stable carrier (A). Examples of suitable dimensionally stable carriers include plates, films, cones, and cylinders made of metals such as steel, aluminum, copper, and nickel, or plastics such as polyethylene terephthalate, polybutylene terephthalate, polyamide, and polycarbonate, or sleeves made of woven and nonwoven fabrics such as glass fiber fabrics (or composite materials made from glass fiber and plastic). Particularly suitable dimensionally stable carriers are dimensionally stable carrier films or metal sheets, such as polyethylene or polyester films, steel sheets, or aluminum sheets. These carrier films generally have a thickness of 50 to 1100 μm, preferably 75 to 400 μm, for example, about 250 μm. When using plastic films, their thickness is in the range of 100 to 200 μm, preferably 125 to 175 μm. When using steel as the carrier material, steel sheets with a thickness of 0.05 to 0.3 mm are preferred. To prevent corrosion, tin-plated steel sheets are preferred. These carrier films or sheets can be coated with a thin adhesion-promoting layer, for example, a layer 0.05 to 5 μm thick, on the side of the carrier film facing the substrate layer, which can be composed of, for example, a mixture of polycarbonate, phenoxy resin, and multifunctional isocyanate.

[0012] These carrier films or sheets are already provided with or can be provided with a thin adhesion-promoting layer (AH), which can be, for example, a polyurethane adhesive varnish (for example according to DE-A 30 45 516) based on polyisocyanate-crosslinked polyether varnish or polyester varnish with a layer thickness of 0.5 to 50 μm, in particular 2 to 30 μm.

[0013] On the side of the adhesive layer opposite the carrier layer, there may be an additional adhesion-promoting intermediate layer (AH). These layers have a thickness of 0.1 to 50, in particular 1 to 10 μm, and can be obtained, for example, from a diluted aqueous alcoholic solution of partially (for example, up to 80 mol%) hydrolyzed polyvinyl ester, phenyl glyceryl ether monoacrylate, and glyoxal, followed by drying and baking.

[0014] The purpose of the adhesion-promoting or intermediate layer is to increase the adhesion between the individual layers and stabilize the layer structure. This requires the selection of a material that can establish an interaction with both layers. Preferred examples are surfactants, amphiphilic molecules with hydrophobic and hydrophilic regions, and block copolymers, as well as oligomers containing blocks compatible with both layers or the polymers in the layers. The adhesion force between the dimensionally stable carrier (A) and the relief-forming layer (B) must exceed 0.5 N / cm when measured in a peel test at a peel angle of 90° and a peel speed of 30 mm / min.

[0015] The relief precursor comprises at least one photopolymerizable, relief-forming layer (B). The photopolymerizable, relief-forming layer can be applied directly to the carrier. However, other layers, such as an adhesive layer or an elastic or compressible underlayer, can be present between the carrier and the relief-forming layer.

[0016] The relief-forming layer (B) can also consist of several layers, in which case it generally comprises 2 to 30 layers, preferably 2 to 5 layers, more preferably 2 to 3 layers, and very preferably 2 layers. The layers can contain the same or different components, in the same or different proportions. Preferably, these layers contain the same components. Preferably, the relief-forming layer closest to the carrier layer is already fixed, crosslinked, and / or reacted. On these fixed, crosslinked, and / or reacted layers, a relief-forming layer is placed, which may also be fixed, crosslinked, or reacted.

[0017] Those skilled in the art are familiar with elastomeric binders for producing the relief-forming layer of a flexographic printing element. Examples include 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 their mixtures.

[0018] Preferably, the elastomer is a thermoplastic elastomeric block copolymer of an alkenyl aromatic compound and a 1,3-diene. The block copolymers can be linear, branched, or radial. Typically, they are triblock copolymers of type ABA, but they can also be diblock copolymers of type AB, or have multiple alternating elastomeric and thermoplastic blocks, e.g., ABABA. Mixtures of two or more different block copolymers can also be used. Commercially available triblock copolymers often contain a specific proportion 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. These are commercially available, for example, under the name Kraton®. Thermoplastic elastomeric block copolymers with styrene endblocks and statistical styrene-butadiene midblocks can also be used. The block copolymers can also be fully or partially hydrogenated, such as SEBS rubber. Preferred elastomeric binders are triblock copolymers of the type ABA or radial block copolymers of the type (AB)n, where A is styrene and B is a diene, and statistical and random copolymers of styrene and dienes.

[0019] In a preferred embodiment of the present invention, the thermoplastic elastomer binder comprises at least one styrene-isoprene block copolymer, particularly a styrene-isoprene-styrene block copolymer, whereby the polymer may also contain a proportion of a diblock styrene-isoprene copolymer. Preferred binders of the styrene-isoprene type generally contain 10 to 30% by weight, preferably 12 to 28% by weight, and more preferably 13 to 25% by weight, of styrene. In a further embodiment, the binder is a styrene-butadiene-styrene (SBS) block copolymer. Preferred SBS polymers generally contain 20 to 35% by weight, preferably 22 to 33% by weight, and more preferably 24 to 31% by weight of styrene. These block copolymers generally have an average molecular weight (MW) of 100,000 to 300,000 g / mol. Of course, mixtures of different styrene-isoprene or styrene-butadiene block copolymers can also be used.

[0020] In a second embodiment of the present invention, radial isoprene-styrene block copolymers can be used. The isoprene and / or butadiene units in the polyisoprene block can be 1,4-linked, with the remaining double bonds arranged in the chain, or 3,4-linked, with the remaining double bonds arranged pendantly. Block copolymers containing essentially 1,4 bonds and binders with a specific ratio of 3,4 bonds can be used. The pendant vinyl groups in binders with 3,4-linked units preferably react during the crosslinking of the photopolymerizable layer, resulting in plates with a high degree of crosslinking. For example, block copolymers with a vinyl group content of 20 to 70% can be used.

[0021] In a preferred embodiment of the present invention, a radial styrene-isoprene copolymer having a vinyl group content of less than 10% can be used. In a second preferred embodiment of the present invention, a mixture of two different styrene-isoprene block copolymers is used. Preferably, one of them has a vinyl group content of at least 20%, particularly 20-70%, and preferably 25-45%. The other has a low vinyl group content, e.g., less than 10%. Also preferably, a mixture of two styrene-isoprene copolymers can be used, one of which has a high diblock fraction of more than 40% by weight and the other a lower diblock fraction of less than 30% by weight. In addition to the above-mentioned thermoplastic elastomeric block copolymers, particularly styrene-isoprene block copolymers, the photopolymerizable layer can also contain an additional elastomeric binder different from the block copolymer. Such an additional binder, also called a secondary binder, allows for modification of the properties of the photopolymerizable layer. Vinyl toluene-α-methyl styrene copolymer is an example of a secondary binder. Generally, the amount of such secondary binders should not exceed 25% by weight, based on the total amount of all binders used. Preferably, the amount of such secondary binders does not exceed 15% by weight, more preferably does not exceed 10% by weight. The total amount of binders is generally 30-90% by weight, preferably 40-85% by weight, more preferably 60-85% by weight, based on the total amount of all components of the relief-forming layer.

[0022] For aqueous-developable relief precursors, water-soluble, swellable, dispersible, or emulsifiable polymers are used. In addition to fully or partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal, polystyrene sulfonate, polyurethane, polyamide (such as those described in EP-A-0085472 or DE-A-1522444), and any combination thereof, can be used. Examples of such polymers are described in EP-A-0079514, EP-A-0224164, or EP-A-0059988. These polymers can be linear, branched, star-shaped, or dendritic, and can exist as homopolymers, statistical copolymers, block copolymers, or alternating copolymers. Very often, the described polymers are equipped with functional groups that increase solubility and / or can participate in crosslinking reactions. These groups include, for example, carboxyl, SO3, OH, thiol, ethylenically unsaturated, (meth)acrylate and epoxide groups, and any combination thereof.

[0023] In the case of the relief-forming layer (B), the total amount of binder is generally 30 to 90% by weight, preferably 40 to 85% by weight, more preferably 45 to 85% by weight, based on the sum of all components of the relief-forming layer.

[0024] The relief-forming layer (B) may contain additional components selected from the group consisting of plasticizers, solvents, other binders, colorants, stabilizers, modifiers, UV absorbers, dispersing aids, crosslinkers, viscosity modifiers, surfactants, and any combination thereof. These additives, auxiliaries, and adjuvants are contained in the radiation-sensitive mixture at an overall concentration of 0.001 to 60% by weight, preferably 0.01 to 50% by weight, more preferably 0.1 to 50% by weight, and very preferably 1 to 50% by weight, based on the total formulation. Individual additives are contained at a concentration of 0.001 to 40% by weight, preferably 0.01 to 40% by weight, more preferably 0.1 to 40% by weight, and very preferably 0.1 to 35% by weight, based on the total formulation.

[0025] The photopolymerizable relief-forming layer (B) also contains, in a known manner, at least one ethylenically unsaturated monomer compatible with the binder or binders. The ethylenically unsaturated monomer may also be a mixture of two or more different monomers. Suitable compounds have at least one olefinic double bond and are polymerizable. Therefore, they are referred to below as monomers. Monomers that have proven particularly advantageous are esters or amides of acrylic 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.

[0026] Generally, these monomers are not gaseous compounds at room temperature. Preferably, the ethylenically unsaturated monomer contains at least two ethylenically unsaturated groups, more preferably 2 to 10 ethylenically unsaturated groups, and most preferably 2 to 6 ethylenically unsaturated groups. Compounds having a C-C triple bond can also be used in the radiation-sensitive mixture. Preferably, the ethylenically unsaturated groups are at least acrylate and / or methacrylate groups, but styrene derivatives, acrylamides, vinyl esters, and vinyl ethers can also be used. The ethylenically unsaturated monomer generally has a molecular weight of 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.

[0027] Possibilities include, in particular, derivatives of acrylic acid or methacrylic acid, such as esters with mono- or polyhydric alcohols, for example acrylic or methacrylic acid esters of alkanols having 1 to 20 carbon atoms (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, etc.), (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, 1,4-butanediol di(meth)acrylate, etc. Acrylates include 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, or pentaerythritol tetra(meth)acrylate, also poly(ethylene oxide) di(meth)acrylate, m-methylpoly(ethylene oxide)-yl-(meth)acrylate, N,N-diethylaminoethyl acrylate, the reaction product of 1 mole of glycerin, 1 mole of epichlorohydrin, 3 moles of acrylic acid with glycidyl methacrylate, and bisphenol A diglycidyl ether acrylate.

[0028] Also suitable are derivatives of acrylamide and methacrylamide, such as ethers of their N-methylol derivatives with mono- and polyhydric alcohols (e.g., ethylene glycol, glycerin, 1,1,1-trimethylolpropane, oligomeric or polymeric ethylene oxide derivatives), which are particularly suitable when polyamides or polyvinyl alcohols are used as binders.

[0029] Also suitable are known epoxy and urethane (meth)acrylates, such as those obtained by reacting bisphenol A diglycidyl ether with (meth)acrylic acid, or by reacting diisocyanates with hydroxyalkyl (meth)acrylates or polyesters or polyethers containing hydroxyl groups. Other olefinically unsaturated compounds that can be used include esters of acrylic or methacrylic acid, especially those with low vapor pressure, and those modified with compatibilizers, for example, with hydroxyl, amide, sulfonated ester, or sulfonamide groups. Mixtures of the above copolymerizable ethylenically unsaturated organic compounds can also be used.

[0030] Preferred ethylenically unsaturated monomers are 1,4-butanediol 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.

[0031] In one embodiment, the ethylenically unsaturated monomer is present in a concentration in the range of 0.5 to 60 wt. %, preferably in the range of 1 to 50 wt. %, more preferably in the range of 1 to 40 wt. %, and most preferably in the range of 2 to 40 wt. %, based on the total formulation.

[0032] The photopolymerizable relief-forming layer also includes a migratable surface-active additive.

[0033] Preferred transferable surface-active additives are selected from the group consisting of ionic or nonionic surfactants, long-chain hydrocarbons, waxes, especially paraffin waxes, organosilicon compounds, especially silicone oils, silanes and siloxanes, or mixtures thereof. Particularly suitable organosilicon compounds are polysiloxane (meth)acrylates, polysiloxane amines, vinyl-terminated polysilanes and polysiloxanes, polyether polysiloxanes, and mixtures thereof. Examples of compounds in the above classes are available under the following trade names: Polyvest ST-E100, Silico Glide T-41, Silico Glide T-57, AFCONA-3700, Silicon F.1000, Silicon F.60000, Rad2010, Rad2200N, Rad2300, Rad2500, Rad2700, Rad2800, Miramer SIU2400, X-22-2445, X-22-174BX, KBM-5103, X-22-161B, KF-8010, Silmer OH ACR C50, Silmer OH ACR Di-400, Silmer ACR Di-10, Silmer OH ACR D4, AFCONA-3835, and Sartomer CN9800.

[0034] In one preferred embodiment, the mobile surface-active additive is a paraffin wax. Preference is given to branched and / or unbranched paraffin waxes with chain lengths of more than 15 C atoms, more preferably more than 20 C atoms, and very preferably more than 30 C atoms. Chain lengths in the range of 20 to 40 C atoms are also preferred.

[0035] The photopolymerizable relief-forming layer also includes a UVA light activatable photoinitiator and a UVC light activatable photoinitiator.

[0036] Preferred photoinitiators activatable by UVA light are selected from the group consisting of benzil ketals, acylphosphine oxides, bisacylphosphine oxides, aminophenyl ketones, phenyloxime esters, and mixtures thereof.

[0037] Preferred photoinitiators activatable by UVC light are selected from the group consisting of hydroxyphenyl ketones, benzoyl formate, benzophenones, aryl alkyl ketones, aryl benzyl ketones, and mixtures thereof.

[0038] In one particularly preferred embodiment, the UVA light activatable photoinitiator is selected from the group consisting of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, benzil dimethyl ketal and benzil diethyl ketal, and the UVC light activatable photoinitiator is selected from the group consisting of oxyphenylacetic acid 2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl ester, oxyphenylacetic acid 2-[2-hydroxyethoxy]ethyl ester, methylbenzoyl formate, p-tolylundecyl ketone, 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenylpropan-1-one and mixtures thereof.

[0039] The migrating surface-active additive is generally included in the photopolymerizable relief-forming layer in an amount of 0.1 to 10% by weight, preferably 0.2 to 5% by weight, and more preferably 0.5 to 1.5% by weight, based on the weight of the photopolymerizable relief-forming layer.

[0040] The UVA light activatable photoinitiator is generally included in the photopolymerizable relief-forming layer in an amount of 0.5 to 20 wt. %, preferably 0.5 to 15 wt. %, more preferably 0.5 to 10 wt. %, and very preferably 0.5 to 6 wt. %, based on the total weight of the photopolymerizable relief-forming layer.

[0041] The UVC light activatable photoinitiator is generally included in the photopolymerizable relief-forming layer at a concentration of 0.1 to 20 wt. %, preferably 0.1 to 10 wt. %, more preferably 0.5 to 5 wt. %, and very preferably 0.25 to 3 wt. %, based on the total weight of the photopolymerizable relief-forming layer.

[0042] Generally, the weight ratio of UVA light activatable photoinitiator to UVC light activatable photoinitiator is 0.1-50, preferably 0.5-40, more preferably 0.5-30, and very preferably 0.5-15.

[0043] Generally, the ratio between the amount of UVA light activatable photoinitiator and the amount of migrating surface active additive is 0.01-10, preferably 0.1-5, more preferably 0.1-3.

[0044] The photopolymerizable relief precursor according to the invention may exhibit one or more further layers selected from the group consisting of: adhesive and / or compressible layers between the carrier layer and the relief-forming layer, functional layers arranged on top of the relief-forming layer, such as structure-imparting layers, barrier layers, cover layers, digitally reproducible mask layers, and combinations of two or more of these layers.

[0045] For example, the photopolymerizable relief precursor may exhibit an intermediate layer, preferably an adhesive layer and / or a compressible layer, between the carrier layer and the photopolymerizable relief-forming layer.

[0046] The photopolymerizable relief precursor may exhibit, on the side of the photopolymerizable relief-forming layer opposite the carrier layer, a further layer selected from the group consisting of a mask layer, a barrier layer, a cover layer, and combinations of two or more of these layers.

[0047] In one preferred embodiment, the photopolymerizable relief precursor comprises: (A) dimensionally stable carrier; (AH) optional adhesion promoting layer; (B) a photopolymerizable relief-forming layer comprising at least a crosslinkable elastomeric binder, an ethylenically unsaturated monomer, a migratable surface-active additive, a UVA light-activatable photoinitiator, and a UVC light-activatable photoinitiator; (C) a laser-abradable mask layer comprising at least a non-radical crosslinkable elastomeric polymer, a UVA light-absorbing material, and an IR light-absorbing material; and, optionally, (D) Peelable cover layer.

[0048] The relief precursor according to the present invention preferably comprises a laser-abradable mask layer (C) disposed on the relief-forming layer (B) and which can also be removed using a solvent or by heating and adsorption / absorption. This layer is heated and volatilized by selective irradiation with high-energy electromagnetic radiation, thus producing a mask with an image-wise structure that 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, allowing the layer to be heated and ablated.

[0049] The optical density of the mask layer in the UV range of 330 to 420 nm is in the range of 1 to 5, more preferably in the range of 1.5 to 4, and most preferably in the range of 2 to 4. The optical density is determined by measuring with an X-rite 361TX densitometer on the "density" setting using a UV filter.

[0050] The layer thickness M of the laser abradable mask layer (C) is generally 0.1 μm to 5 μm. If the layer thickness is less than 0.1 μm, it is difficult to achieve sufficient optical density. If the layer thickness is more than 5 μm, the laser sensitivity of the element is too low, and a long laser time is required for imaging. The layer thickness is preferably 0.3 μm to 4 μm, in particular 1 μm to 3 μm. The laser sensitivity of the mask layer (1 cm of the layer) 2 (measured as the energy required to ablate the 2 , preferably 0.3 to 5 J / cm 2 , more preferably 0.5 to 5 J / cm 2It must be.

[0051] The mask layer (C) comprises at least one non-radical crosslinkable elastomeric polymer, which allows for uniform dispersion of components that absorb electromagnetic radiation and is ablated as efficiently as possible when heated. The elastomeric polymer may be a linear, branched, star-shaped, comb-shaped, or dendritic homopolymer or copolymer. The copolymer may exist as a statistical and / or block copolymer. The elastomeric polymer may also be a mixture of polymers that differ, for example, in structure, monomer composition, block length, molecular weight, functional groups, their number, and / or distribution. A mixture of polymers may also be used.

[0052] Examples of non-radically crosslinkable elastic polymers that are well suited for the mask layer (C) include: ethylene vinyl acetate, flexible elastic polyamides, flexible elastic polyurethanes, nitrocellulose, polyvinyl acetals such as poly(vinyl butyral-vinyl alcohol) copolymers (or poly(vinyl butyral vinyl ethyl-vinyl alcohol) copolymers). Of course, other flexible elastic materials can also be used as binders, such as, for example, partially hydrolyzed polyvinyl acetate. Preferred binders for the mask layer (C) are flexible elastic polyamides, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, or partially hydrolyzed polyvinyl acetals.

[0053] This mask layer (C) can be permeable or impermeable to oxygen.

[0054] Typically, the relief-forming layer (B) and the abradable mask layer (C) are soluble in common commercially available washout media, which generally consist of solvent mixtures or aqueous solutions. These washout media consist primarily of one or more non-polar hydrocarbon solvents, with secondary components in the form of moderately polar alcohols such as benzyl alcohol, n-pentanol, cyclohexanol, ethylhexanol, and heptyl alcohol. The aqueous solutions typically contain surfactants and / or flocculants and generally have a pH >7. The relief-forming layer (C) can typically be processed with these washout media.

[0055] Furthermore, the relief-forming layer (B) and the abradable mask layer (C) can also be thermally developed or removed (see, for example, EP-A-1 239 329 or EP-A-1 170 121). In this case, following imagewise exposure, the relief structure is heated to a softening or melting temperature, which causes the unexposed and non-crosslinked areas of the relief structure to become partially liquid and tacky, and are subsequently removed by suction (absorption) with a nonwoven or woven fabric.

[0056] In a further embodiment, a further oxygen-impermeable layer (E) is present between layers (B) and (C) of the relief precursor according to the invention. If an oxygen-impermeable layer (E) is present, layers (B) and / or (C) are preferably permeable to oxygen. The layer (E) here has a layer thickness in the range of 3 to 5 μm. In addition to the auxiliary agent, this layer mainly comprises one or more elastic polymers with low oxygen permeability, the oxygen permeability of which is less than 1.5×10 5 cm 3 μm / (m 2 The polymer in layer (E) is preferably likewise non-radical crosslinkable.

[0057] Examples of suitable elastomeric polymers that are thermally developable and / or soluble in organic solvents and have sufficient oxygen barrier properties include partially hydrolyzed polyvinyl acetate, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, and ethylene-vinyl acetate-vinyl alcohol copolymers, with a degree of hydrolysis ranging from 30 to 80 mol%. Also highly suitable are cyclic acetals of polyvinyl alcohol, such as polyvinyl butyral, polyvinyl ethyl, polyvinyl formal, and polyvinyl propyl, as well as copolymers containing two or more different vinyl acetal units selected from vinyl formal, vinyl ethyl, vinyl propyl, and vinyl butyral units. Because the complete reaction of polyvinyl alcohol to form acetals is incomplete for statistical and steric reasons, polyvinyl acetals are always copolymers with vinyl alcohol units. Therefore, more precisely, poly(vinyl butyral) is poly(vinyl butyral-vinyl alcohol). The residual OH content of the polyvinyl acetals listed is typically 10-30 wt%. For example, vinylethyl-vinylbutyral-vinyl alcohol copolymer (poly(vinylethyl-vinylbutyral)) is very suitable.

[0058] The object of the invention is also a method for producing a relief structure comprising the following steps: (i) providing a photopolymerizable relief precursor comprising at least one mobile surface-active additive; (ii) applying a mask onto said photopolymerizable relief-forming layer or creating a structured mask layer; (iii) optionally, exposing the backside to electromagnetic radiation through a carrier layer; (iv-a) exposure of the photopolymerizable relief-forming layer through said mask or said mask layer to electromagnetic radiation, preferably in the wavelength range of 315 to 380 nm; (v) removing the mask or the mask layer, any further layers, and the non-photopolymerized areas of the relief-forming layer not exposed in step (iv), thereby generating a relief; (vi) optionally drying the relief; (vii) re-exposure of the relief from the side opposite the carrier layer to UVA light in the wavelength range of 315-380 nm and / or UVC light in the wavelength range of 200-280 nm, whereby the relief is re-crosslinked and the permeability of the mobile surface-active additives is adjusted in order to adjust the surface properties of the relief, preferably for the use of specific printing inks, (viii) Optionally, further processing steps.

[0059] An object of the invention is also a method for producing a relief structure comprising the following steps: (i) providing a photopolymerizable relief precursor comprising at least one mobile surface-active additive; (iii) optionally, exposing the backside to electromagnetic radiation through a carrier layer; (iv-b) imagewise exposure of said photopolymerizable relief-forming layer to electromagnetic radiation, preferably in the wavelength range of 315 to 380 nm; (v) removing any further layers, if present, and the non-photopolymerized areas of the relief-forming layer not exposed in step (iv), thus producing the relief; (vi) optionally drying the relief; (vii) re-exposure of the relief from the side opposite the carrier layer to UVA light in the wavelength range of 315-380 nm and / or UVC light in the wavelength range of 200-280 nm, whereby the relief is re-crosslinked and the permeability of the mobile surface-active additives is adjusted in order to adjust the surface properties of the relief, preferably for the use of specific printing inks, (viii) Optionally, further processing steps.

[0060] In a preferred embodiment, the re-exposure in step (vii) is with UVA light and UVC light. The re-exposure to UVA light and UVC light can be carried out at the same time (simultaneously) or in sequence (alternately).

[0061] For re-exposure to UVA light, this is typically 100-30,000 mJ / cm 2It is performed with a dose of UVA light: 100-20,000mJ / cm 2 UVA light is preferred, with 100 to 7,000 mJ / cm 2 UVA light is more preferable, 500-7,000mJ / cm 2 UVA light is highly preferred.

[0062] For re-exposure to UVC light, this is typically 100-20,000 mJ / cm 2 It is done with a dose of UVC light: 100-20,000mJ / cm 2 UVC light is preferred, with a dose of 100-8,000mJ / cm 2 UVC light is more preferable, with 500-8,000mJ / cm 2 UVC light is highly preferred.

[0063] Re-exposure to UVA and UVC light can occur simultaneously, sequentially, or alternately, thereby reducing the dose ratio of UVA to UVC light (D UVA / D UVC ) is generally greater than 0.2, preferably greater than 0.4, more preferably greater than 0.6, and very preferably greater than 0.8. Due to the shallow penetration depth, exposure to UVC light preferably seals the surface of the layer, whereas exposure to UVA light ensures stronger cross-linking throughout the layer, resulting in a mechanically stable relief.

[0064] In a first step (i), a relief precursor as described above is provided, which can optionally be cleaned using all techniques well known to those skilled in the art, such as brushing, blowing, wiping (with or without solvents), rinsing, and any desired combination thereof.

[0065] The wavelength of the irradiated electromagnetic radiation is in the range of 200 to 2,000 nm, preferably in the UV range, more preferably in the range of 200 to 550 nm, and most preferably in the range of 300 to 450 nm. In addition to broadband electromagnetic radiation, it may be advantageous to use narrowband or monochromatic wavelength ranges of the kind that can be generated using corresponding filters, lasers, or light-emitting diodes (LEDs). In these cases, preferred wavelengths are in the ranges of 350, 365, 385, 395, 400, 405, 532, 830, and 1064 nm, individually (and about 5 to 10 nm above and / or below) or in combination.

[0066] If a cover layer (D) is present, it is removed. Preferably, the cover layer is a protective film and is peeled off.

[0067] In step (ii), the mask layer is imaged either by layer ablation and / or spatially resolved modification of its absorption and / or reflection properties in such a way that the mask layer becomes at least partially transparent in the wavelength range used for imaging. The mask layer is preferably ablated with a high-energy laser, the laser beam being directed onto the mask layer under computer control. In this case, IR lasers with wavelengths in the range of 500-20,000 nm, preferably 800-10,000 nm, and more preferably 1,000-2,000 nm, are primarily used. Wavelengths of approximately 830 nm, 980 nm, 1064 nm, and 10.6 μm, or combinations thereof, are particularly preferred.

[0068] In optional step (iii), the relief precursor can be extensively irradiated with electromagnetic radiation from at least one side. This irradiation is preferably carried out from the side of the relief precursor opposite the mask layer, in order to achieve fixing (back exposure) of the generated relief structure. This back exposure is preferably carried out through a transparent, dimensionally stable material, such as a polymer film, especially a polyester film, as a carrier material. In the case of an opaque carrier material, step (iii) is omitted.

[0069] Exposure of the relief precursor according to the invention to electromagnetic radiation in step (iv-a) via layer (C) and optionally layer (E) induces a reaction in the regions of layer (B) underlying the exposed regions of layer (C), which leads to crosslinking of the components present in the layer. As a result of this crosslinking, these regions are stabilized and cannot be removed in a subsequent development step. Irradiation is generally broad-area, but can alternatively be carried out in small areas (substantially dot-like) by a guided laser beam or spatially resolved projection of electromagnetic radiation. The electromagnetic radiation used for this exposure generally has a wavelength in the range of 200 to 2,000 nm, preferably in the range of 315 to 380 nm.

[0070] The irradiation here can be continuous or pulsed, or multiple short periods with continuous radiation. The intensity of the radiation here can vary over a wide range, ensuring that a sufficient dose is used to crosslink layer (B) for the subsequent development step. The intensity of the radiation is generally between 10 and 1,000 mW / cm. 2 The radiation dose is generally in the range of 3 to 100 J / cm 2 The range is preferably 6 to 20 J / cm 2 The exposure to the energy source can also be carried out in an inert atmosphere, such as, for example, a noble gas, CO2 and / or nitrogen, or under a liquid that does not damage the multilayer elements.

[0071] Direct imaging exposure can be achieved by selectively exposing the areas to be crosslinked. This can be achieved, for example, with one or more laser beams controlled accordingly (through the use of a screen in which specific pixels are activated to emit radiation, through the use of mobile LED strips, through an LED array in which individual LEDs are intentionally switched on and off, through the use of an electronically controllable mask in which pixels are made transparent to allow the radiation of the radiation source to pass, through the use of a projection system in which pixels are exposed to radiation from the radiation source via the orientation of corresponding mirrors, or a combination thereof). Direct exposure with a controlled laser beam or a projection system with mirrors is preferred. Here, the absorption spectrum of the initiator or initiator system and the emission spectrum of the radiation source must at least partially overlap.

[0072] In step (v), layer (C), layer (E), if present, and the non-crosslinked areas of layer (B) are removed to produce the relief. In step (v), the unexposed, non-photopolymerized areas of the relief-forming layer can be removed by treatment with a washout medium or by thermal treatment.

[0073] The layers can be removed individually, in groups, or all together simultaneously. Preferably, all layers and non-crosslinked regions of (B) are removed in a single step. Depending on the nature of the layers, this can be achieved by treatment with a solvent-based or water-based washout medium (e.g., an organic solvent, a mixture thereof, water, an aqueous solution, or a water-organic solvent mixture, etc., that can dissolve, emulsify, and / or disperse the non-crosslinked regions in layer (B)).

[0074] In another embodiment, the removal of layer (C), and, if present, layer (E), and the non-crosslinked regions of layer (B) in step (v) is carried out thermally, i.e., by introducing heat and removing the softened or partially liquefied material from the layers. Heating the exposed relief precursor can be carried out by any technique known to those skilled in the art, such as irradiation with IR light, the action of hot gas (e.g., air), the use of hot rollers, or any desired combination thereof. To (visually) remove the liquid regions, any technique and process familiar to those skilled in the art can be used, such as blowing, suction, tapping, blasting (with particles and / or droplets), stripping, wiping, transferring to a development medium, and any desired combination thereof. Preferably, the liquid material is taken up (absorbed and / or adsorbed) by the development medium, which is continuously brought into contact with the heated surface of the relief precursor. This procedure is repeated until the desired relief height is reached. Possible development media include paper, woven and nonwoven fabrics, and films capable of taking up the liquefied material and which may be composed of natural and / or polymeric fibers. Preference is given to using nonwoven fabrics or nonwoven fibrous webs of polymers such as cellulose, cotton, polyester, polyamide, polyurethane, and any desired combination thereof, which are stable at the temperatures used during development.

[0075] An object of the present invention is also a method for producing an optimized relief structure, wherein steps (i) to (viii) are carried out multiple times, whereby in step (vii) the re-exposure to UVA light and / or UVC light is varied in terms of dose and / or chronological sequence of the UVA and UVC re-exposure steps in order to optimize the surface properties of the relief.

[0076] The present invention also provides a relief structure obtainable by the method described above, and its uses. The relief structure can be used as a pad printing plate, flexographic plate, letterpress plate, gravure plate, microfluidic component, microreactor, foremantic cell, photonic crystal, or optical component. In the case of microfluidic components or microreactors, it can be advantageous to render the surface hydrophobic in order to use aqueous or very polar fluids when using non-polar fluids, in order to reduce wall interaction or to generate a hydrophilic surface. In the case of foremantic cells, photonic crystals, or optical components, rendering the surface hydrophobic or hydrophilic, respectively, can be advantageous in terms of contamination and cleaning.

[0077] The present invention will be elucidated in more detail by the following examples. [Example]

[0078] method: Inflow assessment To assess flow-in, plates were evaluated after approximately 1,000 linear meters of printing by evaluating the tonal value field from 10% to 50%. Significant flow-in (large amount of ink in the interstitial spaces) was given a classification of "-", moderate flow-in was given a classification of "0", and little or no flow-in (no ink in the interstitial spaces) was given a classification of "+".

[0079] Gloss measurement method Gloss measurements were performed to provide evidence of mobile surface-active additives (MSA) on the plate's surface. Gloss was measured at a glancing angle of 60° using a micro TRI-gloss μ glossmeter (BYK-Gardner GmbH). The glossmeter was calibrated prior to measurement using an integrated calibration standard. Results are the average of three measurements at different points on the plate's surface. Cleaning the surface with solvent to remove the MSA increases gloss to 40-50 GU.

[0080] Figures 1-3 show the change in gloss in gloss units (GU) as a function of days for various re-exposure times.

[0081] IR measurement method FT-IR measurements were performed to provide evidence of MSA on the surface of the plate. A Tensor 27 FT-IR (Bruker) equipped with a PIKE MIRacle Diamant / ZnSe ATR-IR unit (PIKE Technologies) was used for FT-IR measurements of the plate surface. Data were captured and analyzed using Opus software version 7.5 (Bruker). Background correction of the spectra was performed automatically. The peaks at 719 and 729 cm were used as a measure of the presence of MSA. -1 The integrals of the IR bands at 1730 cm were used. -1 The integrals of the IR bands were normalized to the values ​​of the IR bands of the saturation and zero values ​​(results without MSA) were subtracted. The signal due to MSA was determined by IR spectroscopy of the pure material. After removing the MSA by washing the surface with solvent, the signal due to MSA in the IR spectrum no longer appears.

[0082] Figures 4 to 6 show the 719 and 729 cm after 7 days at a given re-exposure time. -1 The integrals of the IR bands at

[0083] Contact angle measurement method The effect of MSA on the wetting of surfaces by water was investigated by contact angle measurements. To do so, 10 μL of demineralized water was dropped onto the surface of the printing plate. The water droplet profile was captured with a Keyence VHX-500F optical microscope using a VH-Z20R lens and a VH-S30 tripod. The droplet radius r and height h were measured from these captures using the associated software. The contact angle θ was calculated using trigonometry (Equation 1). θ=arccos(1-h / r) (1)

[0084] Example 1: SBS-based relief precursors (1.14 mm total thickness) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C20) with a melting point of 50–57 °C as the MSA, and 2 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV). The relief precursors were exposed to light in a nyloflex® Combi FIII exposure unit (Flint Group) using fluorescent tubes (Philips TL80W / 10-R) at 16 mW / cm. 2 After removing the protective film, the precursor was imaged with a ThermoFlexX20 (Xeikon) and subsequently exposed to 16 mW / cm 2 at 40 °C in a nyloflex® Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL80W / 10-R). 2 The exposed precursor was exposed through the mask layer for 15 minutes at an intensity of 1000 kJ / cm. The exposed precursor was washed off with nylosolv A in a nyloflex® Digital Washer FIII (Flint Group) at a speed of 220 mm / min. Drying was carried out at 60°C for 120 minutes. Various re-exposures were then carried out in a nyloflex® Combi FIII exposure unit, which resulted in the following: no UVA (Philips TL60W / 10-R, intensity 11 mW / cm). 2 ) only, UVC (Philips TUV 75WHOG75T8, intensity 13mW / cm 2 ) only, and sequential and simultaneous UVA and UVC exposures were used, in each case at 40°C. In this context, simultaneous means that both exposures (with UVA and UVC) started at the same time. IR and gloss measurements of the printed surface thus formed were then carried out at time intervals. The reference did not include MSA. 1A means a 1-minute re-exposure to UVA light, and 1C means a 1-minute re-exposure to UVC light.

[0085] Figures 1, 2, and 3 show the progression of gloss on the surface of a printing plate over time under various re-exposure conditions. As MSA diffuses to the surface, the gloss value decreases. Comparing Figures 4, 5, and 6, we can see that the decrease in gloss value is associated with an increase in IR signal. With a 3-minute re-exposure to UVC (Figure 1), the effect of UVA re-exposure time on MSA migration is not yet apparent. With a 10-minute re-exposure to UVC (Figure 2), the amount of MSA decreases sharply with increasing re-exposure time. The effect of UVC re-exposure on MSA migration is most noticeable when combined with a 10-minute re-exposure to UVA. With a 10-minute exposure to UVA and a 10-minute re-exposure to UVC, much less MSA reaches the printing surface than with a 10-minute re-exposure to UVA without UVC exposure (Figure 3). Therefore, the properties of the printing surface can be controlled.

[0086] [Table 1]

[0087] Table 1 shows the IR integral and gloss of the printed surface after two days as a function of the re-exposure conditions. The higher the IR integral, the more MSA is present on the surface of the plate. The IR integral correlates with the inverse of gloss. Low gloss is evidence of the presence of MSA on the surface. IR spectroscopy cannot detect MSA in its absence. A 10-minute exposure to UVA followed by a 10-minute re-exposure to UVC results in much less MSA reaching the printed surface than no re-exposure or a 10-minute re-exposure to UVA without UVC exposure. Therefore, the properties of the printed surface can be controlled.

[0088] [Table 2]

[0089] Table 2 shows the effect of UVA and UVC exposure on the presence of MSA on the plate surface. A 7-day period was chosen to ensure that MSA did not actually reach the surface. Reference 1 shows the values ​​that would occur without MSA. The less UVA and UVC light applied to the printing plate with MSA, the more MSA would be present on the surface after 7 days. The effect of UVC light here is greater than that of UVA light. The values ​​obtained with the combined UVA and UVC re-exposure correspond to those for the printing plate without MSA.

[0090] Example 2: a) SIS-based relief precursors (1.14 mm thick) were prepared on a polyester carrier containing 1 wt % paraffin wax (>C35) with a melting point of 58 °C as MSA, 5 wt % benzyl-α,α-dimethylacetal (IGM Resins BV), and 0.5 wt % 1-hydroxycyclohexylphenylketone (IGM Resins BV). b) A second relief precursor without 1-hydroxycyclohexylphenyl ketone was prepared similarly to a).

[0091] Both plate types were imaged using fluorescent tubes (Philips TL80W / 10-R) at 16 mW / cm in a nyloflex® Combi FIII exposure unit (Flint Group). 2 After removing the protective film, the precursor was imaged with a ThermoFlexX20 (Xeikon) and subsequently exposed from the backside at an intensity of 16 mW / cm2 at 40 °C using a fluorescent tube (Philips TL80W / 10-R) in a Nylofex Combi FIII exposure unit (Flint Group). 2The precursor was exposed through the mask layer for 15 minutes at an intensity of 11 mW / cm. The precursor was washed off with nylosolv A in a nyloflex® Digital Washer FIII (Flint Group) at a rate of 200 mm / min. Drying was carried out at 60°C for 120 minutes. Various re-exposures were then carried out at 40°C in a nyloflex® Combi FIII exposure unit, whereby UVA and UVC exposures were used in parallel and initiated simultaneously. In the former case, an intensity of 11 mW / cm was used. 2 UVA exposure (Philips TL60W / 10-R) for 10 minutes at an intensity of 13 mW / cm 2 In the latter case, there was a 10-minute UVA exposure and a 10-minute UVC exposure. Gloss measurements of the unprinted area (floor) thus formed were then carried out at time intervals.

[0092] [Table 3]

[0093] Table 3 shows the surface gloss of the printing plate after 3 days and the inflow of the printing plate after printing with solvent-based ink (LM). Lower gloss values ​​are observed with 10 minutes of UVA and 10 minutes of UVC re-exposure (Example 2c) compared to no re-exposure (Example 2a) or 10 minutes of UVA and 3 minutes of UVC re-exposure (Example 2b). This indicates the presence of MSA on the floor surface. In printing tests, the printing plates from Examples 2a and 2b show reduced flow.

[0094] Example 3: a. SBS-based relief precursors (1.14 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C and 2 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV) as the MSA. This was exposed to 19 mW / cm in a Next FV exposure unit (Flint Group) using a fluorescent tube (Light Emission Tech F100T12 / 10-R100W). 2 After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 19 mW / cm² intensity in a Next FV exposure unit (Flint Group) using a fluorescent tube (Light Emission Tech F100T12 / 10-R100W). 2 The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) using Nylosolv A (Flint Group) at a speed of 255 mm / min. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, with re-exposures at room temperature. The UVA exposure time was 10 min, and the UVC exposure time was increased from 0 to 10 min in 2 min intervals. b. SBS-based relief precursors (1.14 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C and 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV) as the MSA. This was exposed to 19 mW / cm in a Next FV exposure unit (Flint Group) using a fluorescent tube (Light Emission Tech F100T12 / 10-R100W). 2After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 19 mW / cm 2 with a Next FV exposure unit (Flint Group) using a fluorescent tube (Light Emission Tech F100T12 / 10-R100W). 2 The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) using Nylosolv A (Flint Group) at a speed of 285 mm / min. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, with re-exposures at room temperature. The UVA exposure time was 8 min, and the UVC exposure time was increased from 0 to 10 min in 2 min intervals. c. An SBS-based relief precursor (1.14 mm thick) was fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C and 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV) as the MSA. This was exposed to 19 mW / cm in a Next FV exposure unit (Flint Group) using a fluorescent tube (Light Emission Tech F100T12 / 10-R100W). 2 After peeling off the protective film, the precursor was imaged with a CDI2530 (Esko) followed by 3 × 250 mm / min and 800 mW / cm for 26 seconds. 2The precursor was exposed through the mask layer in a Next FV exposure unit (Flint Group) using a UV LED strip with an intensity of 1000 uV. The precursor was developed in a nyloflex® Flowline Washer FV (Flint Group) with nylosolv A (Flint Group) at a speed of 255 mm / min. Drying was carried out at 60 °C for 120 min. Next, a UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, with re-exposures at room temperature. The UVA exposure time was 8 min, and the UVC exposure time was increased from 0 to 10 min in 2 min intervals.

[0095] Printing parameters: The solvent-based ink, Flexistar MV Process Cyan (Flint Group), was printed on a 400 mm wide, 55 μm thick LD-PE film (Delo) that was corona pretreated on one side using an F&K Flexpress 6S / 8 press (Fischer & Krecke). The printing plate was fixed using Lohmann 5.3 foam adhesive tape (Lohmann). The anilox roller used had a screen resolution of 420 lines / cm and a 3.5 cm offset. 3 / m 2 The volume was 1000. The printing speed was 200 m / min, and the crosswise feed was 70 μm in the printing unit and 60 μm in the screen roller. Drying was performed in two stages at 40°C and 60°C.

[0096] [Table 4]

[0097] Table 4 shows the evaluation of the influx of printing plates after printing with solvent-based inks at various ratios of simultaneous UVA and UVC re-exposure. The higher the applied UVC re-exposure dose, i.e., the smaller the ratio of UVA to UVC re-exposure doses, the more the influx of printing plates into the interstitial space. On the other hand, at moderate UVC re-exposure doses, migration of MSA largely avoids influx into the interstitial space.

[0098] Example 4: MSA Move SIS-based relief precursors (1.14 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C and 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV) as the MSA. This was exposed to light in a Combi FIII exposure unit (Flint Group) at 28 mW / cm using fluorescent tubes (Philips TL60W / 10-R). 2 After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 19 mW / cm 2 with a Next FV exposure unit (Flint Group) using a fluorescent tube (Light Emission Tech F100T12 / 10-R100W). 2 The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) using Nylosolv A (Flint Group) at a speed of 290 mm / min. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, with re-exposure at room temperature. The UVA exposure time was 8 minutes, and the UVC exposure times were 0 and 2 minutes.

[0099] UV curable ink printing parameters: For printing, an MO4 press (Nilpeter) equipped with an FA4 flexo unit was used, using Flexocure Force UV-curable ink (Flint Group). The printing media used were PE-based adhesive label stock (Raflatac) 330 mm wide and 130 μm thick, or paper-based adhesive label stock (Raflacoat, UPM) 330 mm wide and 120 μm thick. The printing plate was fixed using medium-hardness Tesa Blue foam adhesive tape (Tesa). The anilox roller used had a screen resolution of 500 lines / cm and a 2.5 cm 3 / m 2 The volume was 100 m / min.

[0100] [Table 5]

[0101] Table 5 shows the effect of MSA when printing with UV-curable inks on PE film or paper. UVC re-exposure results in less MSA diffusing to the surface of the printing plate. When printing on PE film, the absence of MSA results in a loss of full-tone color density; when printing on paper, a leading edge occurs. Without UVC re-exposure, MSA diffuses to the surface of the printing plate, facilitating ink transfer to the associated print medium. When printing on PE film, the presence of MSA increases the observed full-tone color density; when printing on paper, the leading edge disappears.

[0102] Example 5: SBS-based relief precursors (1.14 mm thick) were fabricated on a polyester carrier containing 0.1 or 2.5 wt. % paraffin wax (>C35) with a melting point of 58 °C and 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV) as the MSA. This was exposed to 28 mW / cm in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 28 mW / cm 2 in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) at a speed of 250 mm / min using Cyrel® Flexosol-i (DuPont) as the washout medium. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, and re-exposed at room temperature. The UVA exposure time was 8 minutes, and the UVC exposure time was 2 minutes.

[0103] Printing conditions: The solvent-based ink, Flexistar MV Process Cyan (Flint Group), was printed on a 400 mm wide, 55 μm thick LD-PE film (Delo) that was corona pretreated on one side using an F&K Flexpress 6S / 8 press (Fischer & Krecke). The printing plate was fixed using Lohmann 5.3 foam adhesive tape (Lohmann). The anilox roller used had a screen resolution of 420 lines / cm and a 3.5 cm offset. 3 / m 2 The volume was 1000. The printing speed was 200m / min.

[0104] [Table 6]

[0105] In reference 5a, significant inflow of the plate was observed. Addition of MSA significantly reduced the inflow (Examples 5b and 5c (Table 6)).

[0106] Example 6: SBS-based relief precursors (1.14 mm thick) were prepared on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C as the MSA, 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV), and 0%, 0.25%, or 0.5% 1-hydroxycyclohexylphenylketone (C1), or 0.5% mixtures of oxyphenylacetic acid 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and oxyphenylacetic acid 2-[2-hydroxyethoxy]ethyl ester (C2) (respectively IGM Resins BV) at 28 mW / cm using a fluorescent tube (Philips TL60W / 10-R) in a Combi FIII exposure unit (Flint Group). 2 After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 28 mW / cm 2 in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) at a speed of 250 mm / min using Cyrel® Flexosol-i (DuPont) as the washout medium. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, and re-exposed at room temperature. The UVA exposure time was 8 minutes, and the UVC exposure time was 2 minutes.

[0107] Printing conditions: The solvent-based ink, Flexistar MV Process Cyan (Flint Group), was printed on a 400 mm wide, 55 μm thick LD-PE film (Delo) that was corona pretreated on one side using an F&K Flexpress 6S / 8 press (Fischer & Krecke). The printing plate was fixed using Lohmann 5.3 foam adhesive tape (Lohmann). The anilox roller used had a screen resolution of 420 lines / cm and a 3.5 cm offset. 3 / m 2 The volume was 1000. The printing speed was 200m / min.

[0108] [Table 7]

[0109] In the absence of MSA or UVC photoinitiator (Reference 6a), significant flux is observed in the plate. Addition of MSA and UVC photoinitiator significantly reduces flux. For this plate formulation, the addition of 0.5% UVC photoinitiator C2 also reduces flux (Table 7).

[0110] Example 7: SIS-based relief precursors (1.14 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C as the MSA, 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV), and 0%, 0.25%, or 0.5% 1-hydroxycyclohexylphenylketone (C1) (IGM Resins BV). This was exposed to 28 mW / cm in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 28 mW / cm 2 in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) at a speed of 150 mm / min using Cyrel® Flexosol-i (DuPont) as the washout medium. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, and re-exposed at room temperature. The UVA exposure time was 8 minutes, and the UVC exposure time was 2 minutes.

[0111] Printing conditions: The solvent-based ink, Flexistar MV Process Cyan (Flint Group), was printed on a 400 mm wide, 55 μm thick LD-PE film (Delo) that was corona pretreated on one side using an F&K Flexpress 6S / 8 press (Fischer & Krecke). The printing plate was fixed using Lohmann 5.3 foam adhesive tape (Lohmann). The anilox roller used had a screen resolution of 420 lines / cm and a 3.5 cm offset. 3 / m 2 The volume was 1000. The printing speed was 200m / min.

[0112] [Table 8]

[0113] Flux decreases by increasing the UVC photoinitiator content while keeping the UVA photoinitiator content the same. When 0.5% UVC photoinitiator is used (Example 7c), almost no flux is observed (Table 8).

[0114] Example 8: SIS-based relief precursors (1.70 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C, 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV), and 0%, 0.25%, or 0.5% 1-hydroxycyclohexylphenylketone (C1) (IGM Resins BV). This was exposed to 28 mW / cm in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 28 mW / cm 2 in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 The precursor was developed in a nyloflex® Flowline Washer FV (Flint Group) at a speed of 230 mm / min using nylosolv A (Flint Group) as the washout medium. Drying was carried out at 60°C for 120 min. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, and re-exposed at room temperature. The UVA exposure time was 8 minutes, and the UVC exposure time was 4 minutes.

[0115] Printing conditions: The solvent-based ink, Flexistar MV Process Cyan (Flint Group), was printed on a 400 mm wide, 55 μm thick LD-PE film (Delo) that was corona pretreated on one side using an F&K Flexpress 6S / 8 press (Fischer & Krecke). The printing plate was fixed using Lohmann 5.3 foam adhesive tape (Lohmann). The anilox roller used had a screen resolution of 420 lines / cm and a 3.5 cm offset. 3 / m 2 The volume was 1000. The printing speed was 200m / min.

[0116] [Table 9]

[0117] When compared to Reference 8a, the influx of the plates was sharply reduced by the addition of MSA and photoinitiator C1 (Examples 8b and 8c). Further increasing the UVC photoinitiator content from 0.5% (Example 8b) to 1% (Example 8c) did not result in any further improvement in influx (Table 9).

[0118] Example 9: SIS-based relief precursors (1.70 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C, 1 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV), and 0%, 0.5%, 1.0%, 1.5%, or 2.0% 1-(4-methylphenyl)-1-dodecanone (C3) (BASF). This was exposed to 28 mW / cm in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 28 mW / cm 2 in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2The precursor was exposed to UVA light (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) for 9 minutes through a mounted mask layer fixed in place by vacuum. After removing the mask layer, the precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) at a speed of 250 mm / min using Cyrel® Flexosol-i (DuPont) as the washout medium. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started simultaneously and run in parallel, with re-exposure at room temperature. The UVA exposure time was 10 minutes and the UVC exposure time was 5 minutes.

[0119] Printing conditions: The solvent-based ink, Flexistar MV Process Cyan (Flint Group), was printed on a 400 mm wide, 55 μm thick LD-PE film (Delo) that was corona pretreated on one side using an F&K Flexpress 6S / 8 press (Fischer & Krecke). The printing plate was fixed using Lohmann 5.3 foam adhesive tape (Lohmann). The anilox roller used had a screen resolution of 420 lines / cm and a 3.5 cm offset. 3 / m 2 The volume was 1000. The printing speed was 200m / min.

[0120] [Table 10]

[0121] Significant flux through the plate was observed in Reference 9a. Addition of MSA and photoinitiator C3 (Examples 9b-9e) significantly reduced flux. Starting with a 1.0% concentration of UVC photoinitiator C3 (Example 9c), almost no flux was observed. The same was true when the UVC photoinitiator concentration was further increased to 1.5% or 2.0% (Examples 9d and 9e) (Table 10).

[0122] Example 10: SIS-based relief precursors (total thickness 1.14 mm) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C20) with a melting point of 50-57°C as the MSA, 2 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV), and 0% or 0.5% 1-hydroxycyclohexylphenylketone (IGM Resins BV). The relief precursors were exposed to 16 mW / cm illumination in a nyloflex® Combi FIII exposure unit (Flint Group) using fluorescent tubes (Philips TL80W / 10-R). 2 After removing the protective film, the precursor was imaged with a ThermoFlexX20 (Xeikon) and subsequently exposed to light from the backside at an intensity of 16 mW / cm2 using a fluorescent tube (Philips TL80W / 10-R) in a Nylofex Combi FIII exposure unit (Flint Group). 2 The precursor was exposed through a mask layer at 40°C for 15 minutes with an intensity of 10 ... 2 ) only, UVC (Philips TUV 75W HO G75T8, intensity 13mW / cm 2) alone or simultaneous UVA and UVC exposures were used, each at 40 °C. In this context, simultaneous means that both exposures (UVA and UVC) started at the same time. After at least one week of storage after development of the printing plate, contact angle measurements were performed on the printed surface thus formed. The reference used was the surface of pure MSA obtained by melting and subsequent cooling.

[0123] The contact angle is a measure of the wetting of a surface. Uniform wetting of a surface by a liquid (printing ink) is a fundamental prerequisite for a successful printing process. Without complete wetting, the printing form cannot be completely transferred to the print medium. Wetting is crucially determined by the difference between the surface tension of the printing ink and the surface energy of the printing plate. If there is a significant difference between the surface tension of the liquid and the surface energy of the printing plate, a drop of the liquid on the surface will exhibit a large contact angle. If the difference is small, the surface will be uniformly wetted by the liquid and the contact angle will be small. MSA creates a hydrophobic surface. For example, with polar liquids such as water, a large contact angle is expected.

[0124] Table 11 shows the contact angles of a water droplet on the printing plate with and without MSA on the surface of the printing plate. The presence of MSA is controlled by re-exposure. Pure MSA serves as the reference.

[0125] [Table 11]

[0126] The presence of MSA on a surface affects the wetting of the surface by water. When MSA is present on the surface of a printing plate, the contact angle of a water droplet is much larger than when MSA is not present on the surface. When MSA is present on the plate surface (Examples 10b, 10d, and 10f), the contact angle of a water droplet approaches that of pure MSA (Reference 10a). In the absence of MSA, the concentration of photoinitiator has a particular effect on the contact angle. A smaller contact angle was obtained with 1% UVC PI (Example 10e) than without it (Example 10c). When printing with water-based inks, the presence of MSA can result in wetting problems. MSA migration can be controlled by re-exposure.

[0127] Example 11: SBS-based relief precursors (total thickness 1.14 mm) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C20) with a melting point of 50-57 °C as the MSA, and 5 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV). The relief precursors were exposed to 16 mW / cm in a nyloflex® Combi FIII exposure unit (Flint Group) using fluorescent tubes (Philips TL80W / 10-R). 2 After removing the protective film, the precursor was imaged with a ThermoFlexX20 (Xeikon) and subsequently exposed from the backside at an intensity of 16 mW / cm2 using a fluorescent tube (Philips TL80W / 10-R) in a Nylofex Combi FIII exposure unit (Flint Group). 2 The plate was exposed through the mask layer at an intensity of 1000 kJ / cm² at 40°C for 15 minutes. The exposed precursor was washed off in a nyloflex® Digital Washer FIII (Flint Group) using nylosolv A at a speed of 220 mm / min. Drying was carried out at 60°C for 120 minutes. The plate was then exposed to UVA light (Philips TL60W / 10-R, intensity 11 mW / cm²) in a nyloflex® Combi FIII exposure unit. 2) for 10 minutes under UVC light (Philips TUV 75W HO G75T8, intensity 13mW / cm 2 ) for 5 min. Both exposures (UVA and UVC) started simultaneously and were carried out at 40 °C. After at least one week of storage after development of the printing plate, contact angle measurements were carried out on the printed surface thus formed. The reference used was the surface of pure MSA obtained by melting and subsequent cooling.

[0128] [Table 12]

[0129] When MSA is present on the surface of the printing plate (Example 11b), the contact angle approaches that of pure MSA (Reference 11a). When MSA is absent from the surface of the plate (Example 11c), a much smaller contact angle is obtained, even if other processing conditions are the same.

[0130] Example 12: SBS-based relief precursors (1.14 mm thick) were fabricated on a polyester carrier containing 1 wt. % paraffin wax (>C35) with a melting point of 58 °C and 2 wt. % benzyl-α,α-dimethylacetal (IGM Resins BV) as the MSA. Plates contained either no MSA, 1 wt. % paraffin wax (>C35) with a melting point of 58 °C, or 0.5 wt. % polysiloxane polyester acrylate (PPA) as the MSA. The relief precursors were exposed to 26 mW / cm in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2 After removing the protective film, the precursor was imaged with a CDI2530 (Esko) and subsequently exposed to 26 mW / cm 2 in a Combi FIII exposure unit (Flint Group) using a fluorescent tube (Philips TL60W / 10-R). 2The precursor was developed in a Nyloflex® Flowline Washer FV (Flint Group) using Nylosolv A (Flint Group) at a speed of 255 mm / min. Drying was carried out at 60°C for 120 minutes. Next, UVA exposure (Philips TL80W / 10-R SLV G13, intensity 12 mW / cm) was performed. 2 ) and UVC exposure (Philips TUV TL-D95W HO SLV / 25, intensity 11 mW / cm 2 ) were started at the same time and run in parallel, with re-exposure at room temperature. The UVA exposure time was 10 minutes and the UVC exposure time was 6 minutes.

[0131] Printing conditions: An MO4 press (Nilpeter) equipped with an FA4 flexo unit was used for printing using Flexocure Ancora Process Cyan UV-curable ink (Flint Group). The printing media used were one-sided corona-treated PE-based adhesive label stock (Raflatac) or 120 μm thick paper-based adhesive label stock (Raflacoat, UPM). Tesa Blue foam adhesive tape (Tesa) of medium hardness was used to fix the printing plate. The anilox roller used had a screen resolution of 500 lines / cm and a 2.5 cm 3 / m 2 The volume was provided. The printing speed was 100 m / min. The inflow was evaluated after approximately 500 linear meters.

[0132] result: Table 13: Flow of the plate after printing on PE film and paper. Re-exposure used: Intensity UVA 7200 mJ / cm 2 ;UVC=3960mJ / cm 2 . UVA / UVC re-exposure intensity ratio = 1.8.

[0133] [Table 13]

[0134] Table 13 shows the effect of MSA on plate flow when printed with UV-curable inks. Significant flow is observed without MSA. Block flow can be significantly reduced by adding paraffin wax as an MSA. Further improvement in flow is observed when polysiloxane polyester acrylate is used as an MSA.

Claims

1. A photopolymerizable relief precursor comprising: (A) a dimensionally stable carrier; (B) at least a crosslinkable elastomeric binder, an ethylenically unsaturated monomer, a migratable surface-active additive, a UVA light-activatable photoinitiator, and a UVC light-activatable photoinitiator; 10. A photopolymerizable relief-forming layer, wherein said mobile surface-active additive is paraffin wax or polysiloxane polyester acrylate.

2. 2. The photopolymerizable relief precursor of claim 1, wherein the photopolymerizable relief-forming layer comprises the migrating surface-active additive in an amount of 0.1 to 10 wt. %, based on the weight of the photopolymerizable relief-forming layer.

3. 3. A photopolymerizable relief precursor according to claim 1 or 2, wherein the chain length of said paraffin wax is more than 15 C atoms.

4. 4. The photopolymerizable relief precursor according to claim 1, wherein the ratio between the amount of UVA light activatable photoinitiator and the amount of mobile surface-active additive is 0.01 to 10.

5. 5. A photopolymerizable relief precursor according to claim 1, wherein the photoinitiator activatable with UVA light is selected from the group consisting of benzil ketals, acylphosphine oxides, bisacylphosphine oxides, aminophenyl ketones, phenyl oxime esters and mixtures thereof, and the photoinitiator activatable with UVC light is selected from the group consisting of hydroxyphenyl ketones, benzoyl formate, benzophenones, aryl alkyl ketones, aryl benzyl ketones and mixtures thereof.

6. 5. A photopolymerizable relief precursor according to any one of claims 1 to 4, characterized in that the photoinitiator activatable by UVC light is selected from the group consisting of hydroxyphenyl ketones, benzoyl formate, benzophenone, aryl alkyl ketones, aryl benzyl ketones and mixtures thereof.

7. 7. A photopolymerizable relief precursor according to claim 5 or 6, characterized in that the photoinitiator activatable with UVA light is selected from the group consisting of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, benzil dimethyl ketal and benzil diethyl ketal, and the photoinitiator activatable with UVC light is selected from the group consisting of oxyphenylacetic acid 2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl ester, oxyphenylacetic acid 2-[2-hydroxyethoxy]ethyl ester, methylbenzoyl formate, p-tolylundecyl ketone, 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenylpropan-1-one and mixtures thereof.

8. 8. The photopolymerizable relief precursor according to claim 1, wherein the photopolymerizable relief-forming layer comprises the mobile surface-active additive in an amount of 0.2 to 5 wt. %, based on the weight of the photopolymerizable relief-forming layer.

9. 9. The photopolymerizable relief precursor according to claim 1, wherein the photopolymerizable relief-forming layer comprises the UVA light activatable photoinitiator in an amount of 0.5 to 20 wt. %, based on the total weight of the photopolymerizable relief-forming layer.

10. 10. The photopolymerizable relief precursor according to claim 1, wherein the photopolymerizable relief-forming layer comprises the UVC light activatable photoinitiator in a concentration of 0.1 to 20 wt. %, based on the total weight of the photopolymerizable relief-forming layer.

11. 11. The photopolymerizable relief precursor according to any one of claims 1 to 10, characterized in that the photopolymerizable relief-forming layer comprises the mobile surface-active additive in an amount of 0.5 to 1.5 wt. %, based on the weight of the photopolymerizable relief-forming layer.

12. A method for producing a relief structure comprising the steps of: (i) providing a photopolymerizable relief precursor according to any one of claims 1 to 11, (ii) applying a mask onto said photopolymerizable relief-forming layer or creating a structured mask layer; (iv-a) exposing said photopolymerizable relief-forming layer to electromagnetic radiation through said mask or said mask layer; (v) removing the mask or the mask layer, any further layers, and the non-photopolymerized areas of the relief-forming layer not exposed in step (iv), thereby generating a relief; (vii) re-exposing the photopolymerizable relief-forming layer of the relief from the side opposite the dimensionally stable carrier to UVA light in the wavelength range of 315-380 nm and / or UVC light in the wavelength range of 200-280 nm, whereby the relief is re-crosslinked and the transparency of the mobile surface-active additive is adjusted in order to adjust the surface properties of the relief.

13. A method for producing a relief structure comprising the steps of: (i) providing a photopolymerizable relief precursor according to any one of claims 1 to 11, (iv-b) imagewise exposing said photopolymerizable relief-forming layer to electromagnetic radiation; (v) removing further layers, if present, and non-photopolymerized areas of the relief-forming layer not exposed in step (iv), thus producing the relief; (vii) re-exposing the photopolymerizable relief-forming layer of the relief from the side opposite the dimensionally stable carrier to UVA light in the wavelength range of 315-380 nm and / or UVC light in the wavelength range of 200-280 nm, whereby the relief is re-crosslinked and the transparency of the mobile surface-active additive is adjusted in order to adjust the surface properties of the relief.

14. 14. The method of claim 12 or 13, wherein in step (vii) said re-exposure to UVA light and UVC light is performed, whereby said re-exposure to UVA light and UVC light is performed simultaneously, sequentially or alternatingly.

15. 14. Method according to claim 12 or 13, characterized in that the re-exposure conditions are adjusted as a function of the type of printing ink in order to adjust the surface properties of the relief for that printing ink.

16. 16. The method of claim 15, wherein by selecting re-exposure conditions, the surface properties of the printing plate can be adjusted to make it suitable for printing with solvent-based inks, water-based inks, or UV-curable inks.

17. 17. A method according to any one of claims 12 to 16 for producing an optimized relief structure, characterized in that the method comprises performing steps (i) to (viii) multiple times, whereby in step (vii) the re-exposure to UVA and / or UVC light is varied in terms of dose and / or chronological sequence of UVA and UVC re-exposure steps in order to optimize surface properties of the relief.

18. A method according to any one of claims 12 to 17, characterized in that the migration of said mobile surface-active additive is controlled by the choice of exposure parameters of the re-exposure step.

19. 19. The method according to any one of claims 12 to 18, characterized in that there is a re-exposure to UVA light of 100 to 30,000 mJ / cm2.

20. 20. The method according to any one of claims 12 to 19, characterized in that there is a re-exposure to UVC light of 100 to 20,000 mJ / cm2.

21. 21. The method according to any one of claims 12 to 20, characterized in that the ratio of the doses of UVA to UVC light (DUVA / DUVC) is greater than 0.

2.

22. 16. The method according to any one of claims 12 to 15, characterized in that exposure to UVC light seals the surface of the layer due to its shallow penetration depth, while said exposure to UVA light ensures stronger cross-linking of the entire layer.

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