Flexographic printing plate precursor, imaging assembly and uses

Abstract

The present invention relates to a relief-forming precursor comprising a substrate and a relief-forming layer having: a polymer; at least one photopolymerizable monomer; a photopolymerization initiator; and a low surface energy monomer. A relief-forming assembly comprises the relief-forming precursor having the low surface energy monomer and a mask element in full optical contact with the relief-forming surface. A method of making a relief image comprises: exposing the relief-forming layer to curing UV radiation through the mask element to form an imaged relief-forming layer having polymerized regions and non-polymerized regions; removing the mask element from the imaged relief-forming layer; and developing the imaged relief-forming layer by removing the non-polymerized regions to form a relief image. The relief image layer comprises an elastomer and a copolymer comprising at least one photopolymerizable monomer and a low surface energy monomer having a siloxane moiety; and the relief surface comprises a siloxane moiety.

Description

Background Art Technical field:

[0002] The present disclosure relates to flexographic printing plate precursors, imaging assemblies, and methods of making and using the same. More particularly, the present disclosure relates to a photosensitive layer of a relief-forming precursor configured to have a reduced peel force and to produce a relief image with a reduced surface energy.

[0003] Description of related technology:

[0004] Previously, photosensitive materials have been combined with masks in flexographic printing plate precursors. However, removing the mask from the photorelief-forming layer without damaging the mask or the photorelief-forming layer can be difficult. Often, the photorelief-forming layer can be damaged during mask removal. A damaged photorelief-forming layer cannot be used in flexographic printing plates because it can produce artifacts. Consequently, research is ongoing to develop technologies that improve the ability to successfully remove the mask from the photorelief-forming layer without causing any damage.

[0005] Photosensitive relief-forming materials having a relief-forming material or a photosensitive layer are known in the art. Important advances in this field and useful materials for producing flexographic relief images are described in U.S. Patent Application Publication 2005 / 0227182 (Ali et al., hereinafter referred to as US'182). US'182 describes suitable mask element precursors, photosensitive materials for the relief-forming layer, and processes and apparatus for forming a mask element from the mask precursors and a final relief image from the photosensitive relief-forming precursor material.

[0006] Typically, a mask element can be brought into intimate contact with a photosensitive relief-forming precursor material using a laminator apparatus or vacuum drafting, or both, and exposed to actinic radiation (e.g., UV radiation) throughout to cure the photosensitive composition in the relief-forming precursor material in the unmasked areas, thereby forming a negative image of the mask element in the photosensitive relief-forming precursor. The mask element can then be removed, and a development process can be used to remove the uncured areas on the relief-forming material. After drying, the resulting imaged relief-forming precursor has a relief image that can be used in flexographic or relief printing operations.

[0007] Advances in mask element precursors are described in U.S. Patent No. 7,799,504 (Zwadlo et al.). Other useful mask element precursors and processes for their use are described in U.S. Patent No. 8,198,012 (Zwadlo et al.), U.S. Patent No. 8,945,813 (Kidnie), and U.S. Patent No. 9,250,527 (Kidnie). Advances in photosensitive materials are described in U.S. Patent No. 2019 / 0258154 (Kidnie). U.S. Patent No. 8,530,142 (Zwadlo) describes a photopolymer plate precursor that includes a low surface energy release layer on the photosensitive layer to aid in delamination. U.S. Patent No. 10,207,491 (Ali et al.) describes a method of making a flexographic printing plate that includes laminating a mask image to a flexographic printing plate precursor, UV exposure to form a relief pattern, and delaminating the mask from the photosensitive layer. U.S. Patent No. 9,114,601 (Baldwin et al.) describes a flexographic printing plate precursor consisting of two photosensitive layers having low surface energy siloxane monomers only in the photosensitive bottom layer in contact with the backing layer, but no siloxane monomers in the photosensitive top layer in contact with the mask layer, and teaches that the photosensitive top layer has a higher surface energy (e.g., at least 5 dynes / cm) than the bottom layer.

[0008] While the mask element precursors described in these publications have found considerable value in the flexographic printing industry, there is a need for further improvements in the process to manufacture mask elements in an efficient manner, and there is a need to improve interlayer adhesion when a lamination process is used, intimate contact between the mask element and the relief-forming precursor during imaging, and better lowering of the mask element into the relief-forming precursor when vacuum drawing is used.

[0009] Therefore, a need exists for a technique that can be used to provide a photosensitive layer with reduced surface energy and reduced peel force during mask removal. Summary of the Invention

[0010] In some embodiments, the relief-forming precursor may include a substrate and a relief-forming layer. The relief-forming layer may be prepared to have a bottom surface facing the substrate and a relief-forming surface facing away from the substrate. In some aspects, the relief-forming layer may include: a polymer, such as an elastomer; at least one photopolymerizable monomer; a photopolymerization initiator; and a low surface energy monomer. In some aspects, the low surface energy monomer has a siloxane portion connected to at least one polymerizable functional group (e.g., through a joint). In some aspects, at least one polymerizable functional group includes at least one acrylate portion. In some aspects, at least one acrylate portion includes acrylate or methacrylate. In some aspects, the low surface energy monomer includes a plurality of polymerizable functional groups (e.g., siloxane polymer, PDMS) connected to the siloxane portion.

[0011] In some embodiments, the relief-forming precursor may include an adhesive layer on the substrate opposite the relief-forming layer. In some aspects, an antihalation material may be included in the adhesive layer or omitted from the adhesive layer.

[0012] In some embodiments, the relief-forming precursor may consist essentially of the following, in order: a substrate; an optional metal layer on the substrate; a single layer of the relief-forming layer on the substrate or metal layer; and an optional cover sheet on the relief-forming layer.

[0013] In some embodiments, a relief-forming assembly may include a relief-forming precursor and a mask element. In some aspects, the relief-forming precursor may be configured with any of the embodiments described herein that include a low surface energy monomer. In some aspects, the mask element may include an imaged layer having a mask image. In some aspects, the mask element may be in full optical contact with the relief-forming surface of the relief-forming layer.

[0014] In some aspects, the relief-forming assembly may consist essentially of the following, in order: a substrate; an optional metal layer on the substrate; a single layer of relief-forming layer on the substrate or metal layer; and a mask element in full optical contact with the relief-forming surface of the relief-forming layer.

[0015] In some embodiments, a method of manufacturing a relief-forming assembly may include: providing a mask element according to one embodiment; providing a relief-forming layer having a low surface energy monomer according to one embodiment; placing an imaging layer of the mask element on a relief-forming surface of the relief-forming layer; and establishing full optical contact between the mask element and the relief-forming surface. In some aspects, the method may include laminating the mask element to the relief-forming surface. In some aspects, the method may include coupling the mask element to the relief-forming surface by vacuum drawing.

[0016] In some embodiments, a method of making a relief image in a relief-forming assembly may include: providing a relief-forming assembly according to one embodiment; exposing a relief-forming layer to curing UV radiation through a masking element to form an imaged relief-forming layer having UV-exposed regions forming polymerized regions and non-exposed regions forming non-polymerized regions in the imaged relief-forming layer; removing the masking element from the imaged relief-forming layer; and developing the imaged relief-forming layer by removing the non-polymerized regions in the imaged relief-forming layer to form a relief image element having a relief image (e.g., without non-polymerized regions). In some aspects, the method may include polymerizing at least one photopolymerizable monomer and a low surface energy monomer with a photopolymerization initiator such that low surface energy moieties are present in the body and at the relief surface of the relief image of the relief image element. In some aspects, the method may include polymerizing a plurality of polymerizable functional groups of the low surface energy monomer with the at least one photopolymerizable monomer to form a cross-linked polymeric relief image element. In some aspects, the low surface energy monomer has a siloxane moiety attached to at least one polymerizable functional group. In some aspects, the at least one polymerizable functional group comprises at least one acrylate moiety.

[0017] In some embodiments, a relief image element can include a substrate and a relief image layer. The relief image layer can include an elastomer and a copolymer. The copolymer can include at least one photopolymerizable monomer and a low surface energy monomer having a siloxane moiety. The relief surface of the relief image layer can have the peaks and valleys of the relief image, and a portion of the siloxane moiety is present at the relief surface. In some aspects, the copolymer includes crosslinks of the photopolymerized monomer and the low surface energy monomer.

[0018] The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and following information and other features of the present disclosure will become more apparent from the following description and appended claims taken in conjunction with the accompanying drawings. It should be understood that these drawings depict only several embodiments in accordance with the present disclosure and, therefore, should not be considered limiting of its scope, and the present disclosure will be described with additional specificity and detail through use of the accompanying drawings.

[0020] Figure 1A is a schematic cross-sectional view of an embodiment of a mask precursor according to the present invention and illustrating incident infrared radiation used to make a mask element.

[0021] Figure 1B is Figure 1AA schematic cross-sectional view of an embodiment of a mask element formed from a mask precursor is shown.

[0022] Figure 1C is a schematic cross-sectional view of an embodiment of a relief image forming assembly according to the present invention, comprising Figure 1B The mask element is shown in full optical contact with the relief-forming precursor.

[0023] Figure 1D Is to use through Figure 1B A schematic cross-sectional view of an embodiment of a mask element showing incident UV radiation forming an imaged relief-forming precursor.

[0024] Figure 1E is Figure 1D Schematic cross-section of an embodiment of a relief image element provided after imaging is shown, along with a suitable development process for removing unexposed areas in the UV sensitive layer of the imaged relief-forming precursor.

[0025] The elements and components in the figures may be arranged according to at least one embodiment described herein, and the arrangement may be modified according to the disclosure provided herein by one of ordinary skill in the art.

[0026] Detailed description

[0027] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols generally identify similar components unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure as generally described herein and shown in the accompanying drawings may be arranged, substituted, combined, separated, and designed in a variety of different configurations, all of which are expressly contemplated herein.

[0028] Relief forming precursor

[0029] Generally, the present technology includes a photosensitive relief-forming material useful as a relief-forming photopolymer plate precursor having a low-surface energy additive that results in a reduced surface energy and reduced peel force, allowing other layers, films, or bodies to be removed from the photosensitive relief-forming material without damaging any of these components. The resulting relief image element, still having the low-surface energy additive, has a reduced surface energy, for example, due to bonding with a substrate (e.g., polymerization and / or crosslinking) due to the presence of the bound low-surface energy additive at the surface of the relief image. In particular, the reduced peel force and reduced surface energy of the photosensitive relief-forming layer allow for improved coupling with a mask and improved separation of the mask from the imaged relief-forming layer, resulting in the photosensitive relief-forming layer having improved properties that allow for improved use, imaging, and development. For example, the reduced surface energy from the low-surface energy additive can lower the surface energy of the material, allowing for better and more complete optical coupling of the mask layer thereto, followed by improved separation. Furthermore, the subsequent reduced surface energy allows for improved use of the resulting photopolymer plate having the relief image element. The improved photosensitive relief-forming layer can also be used with solvent-washed or water-washed boards.

[0030] US '182 (as mentioned above) provides detailed information on a number of useful relief-forming precursors, such as flexographic printing plate precursors, relief printing plate precursors, and printed circuit boards. Such relief-forming precursors may include a suitable dimensionally stable substrate and a UV (ultraviolet) sensitive relief-forming layer, and optionally a cover sheet and / or metal layer between the substrate and the relief-forming layer. Suitable substrates include dimensionally stable polymer films and aluminum sheets. Polyester films are particularly useful. When they include a low surface energy additive, any UV-sensitive material or element in which a masking element can be used to produce a relief image may be used in the practice of the present invention.

[0031] In some embodiments, the relief formation precursor generally comprises a suitable dimensionally stable substrate, a radiation curable layer with a low surface energy additive that can form a flexographic relief image, and optionally a cover sheet on the radiation curable layer and / or the metal layer between the substrate and the radiation curable layer. Suitable substrates include flexible, dimensionally stable transparent polymer films and metal substrates, such as aluminum sheet. Polyester film is particularly useful as a flexible, dimensionally stable transparent substrate. Optionally, the relief formation precursor can include a metal layer that is arranged between the substrate and the radiation curable layer. This metal layer can include copper or other metals or metal alloys.

[0032] Some embodiments further comprise a removable cover sheet that protects the radiation curable layer from fingerprints and other damage and is disposed over the radiation curable layer. In some embodiments, the flexographic printing plate precursor further comprises a metal layer between the substrate and the radiation curable layer, or both the cover sheet and the metal layer are sandwiched between the radiation curable layer.

[0033] In some embodiments, the radiation-curable layer can be a UV-sensitive layer that is cured by UV light. In some aspects, the UV-sensitive layer can be at least one layer of a relief-forming precursor formed from a UV-sensitive relief-forming material. Thus, reference to a relief-forming material or layer refers to a UV-sensitive material or layer that can be irradiated with UV light and developed into a relief image.

[0034] In some embodiments, the relief-forming precursor comprises: a backing or base film (e.g., as a substrate), a relief-forming layer (e.g., a UV-sensitive material); and an optional removable cover film to protect the photosensitive layer. In another option, a metal layer can be located between the substrate and the relief-forming layer.

[0035] In some embodiments, backing or substrate can be configured to provide support to the relief-forming layer of the relief-forming precursor. The backing layer can be formed by transparent or opaque materials, such as paper, cellulose film, plastic or metal. The backing layer is preferably formed by flexible transparent materials. Examples of such materials are cellulose film or plastic, such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyether, polyethylene, polyamide (Kevlar) or nylon. Preferably, the support layer is formed by polyethylene terephthalate (PET). It has also been found that the relief-forming layer with low surface energy additives can be attached to the support layer. The thickness of the support layer can be approximately 0.001 to approximately 0.010 inches. Optionally, various layers, such as antihalation layer and / or adhesive layer can be set between the backing layer and the relief-forming layer. In some aspects, the adhesive layer can include antihalation material (e.g., light absorbing material to prevent light refraction) or can exclude such antihalation material.

[0036] In some embodiments, the relief-forming layer with reduced peel force can be a UV light-sensitive material that forms a relief image when imaged and developed using UV light, wherein the relief image has a reduced surface energy. Adding a low-surface-energy additive to the UV light-sensitive material can provide many desirable properties for relief image forming schemes, such as easier vacuum drawdown and better lamination to reduce bubble formation. Furthermore, the reduced peel force allows for easier removal of the imaged mask from the relief-forming layer after the primary UV exposure to form the relief image. This scheme can now be performed by peeling the mask from the imaged relief-forming layer. The improved separation resulting from the reduced surface energy and reduced peel force can be applied to the larger plate sizes required for commercial applications. Thus, the photosensitive relief-forming material with reduced surface energy and reduced peel force allows for easier separation of the mask element and photopolymer plate precursor assembly.

[0037] In some embodiments, by incorporating a low surface energy additive into the composition of the photosensitive material, a reduced surface energy and a reduced peeling force are obtained. The low surface energy additive can be contained in the photosensitive material matrix so as to be present in and distributed on the surface of the main body and the photosensitive material. Typically, the low surface energy additive is uniformly mixed in the photosensitive material. However, the additive can be provided randomly or unevenly (e.g., non-uniformly), or provided with a gradient in which the concentration preferentially increases to one side or the other.

[0038] In some embodiments, the low surface energy additive may include a siloxane material, such as a siloxane-based monomer having a reactive functional group. The reactive functional group may be selected to be polymerizable with other polymerizable monomers of the photosensitive material. This allows the siloxane to be incorporated into the polymeric material so that it is retained on the portion of the photosensitive material remaining after the relief formation process. As a result, the reactive functional group may be customized from known functional groups that can participate in polymerization reactions with other monomers of a specific type having the same functional group or different functional groups but having the appropriate reactive functional groups.

[0039] The low surface energy additive makes it easier to separate the mask from the relief-forming precursor. It also provides a lower surface energy to the relief image layer of the flexographic printing plate, which can provide additional benefits for printing.

[0040] In some embodiments, the siloxane material of the low surface energy additive may include an acrylate functional group that can react during polymerization. Although acrylates (e.g., with a hydrogen on the alpha carbon) can be used, other acrylates with substituents on the alpha carbon can also be used. Other acrylates can be substituted acrylates with substituents on the alpha carbon. A common example includes methacrylate with a methyl group on the alpha carbon. The siloxane portion can be attached to the ester oxygen of the acrylate portion. The siloxane portion can include a linker connected to the ester oxygen.

[0041] In some embodiments, the silicone material may include a polydimethylsiloxane (PDMS) backbone having alkyl or alkoxy side chains and having acrylate groups (e.g., acrylate or methacrylate). Such silicone acrylate additives are commercially available from various suppliers and may be referred to as TEGO RAD (silicone polyether acrylates), such as TEGO RAD 2250, TEGO RAD 2300, TEGO RAD 2500, TEGO RAD 2700, CN9800 (difunctional aliphatic silicone acrylate oligomer), EBECRYL 350 (silicone diacrylate), and the like.

[0042] In some embodiments, the siloxane material may include the following structure of Formula 1, Formula 2, Formula 3, Formula 4, or Formula 5:

[0043]

[0044]

[0045] Formula 1 may include m and n as defined below, and each X may independently be a substituent or a polymerizable functional group, wherein at least one X in "m" monomers is a polymerizable functional group. In the formula, n ranges from 1 to 50 (or 10 to 20 or 14 to 16), and m ranges from 0.1 to 10 (or 0.5 to 5 or 0.9 to 3 or 1 to 3), for example, m is 1 in each monomer. The molecular weight may be in the range of 1,000 g / mol to 2,500 g / mol. Y may be any joint, such as those described herein or otherwise known in the art. For example, Y may be the joints shown in Formulas 4 and 5. In addition, the Y joint may include a C1-C10 alkyl group. R may be a substituent, such as an alkyl group (e.g., methyl, ethyl, propyl, etc.).

[0046] In some embodiments, the Y linker can be a hydrocarbon chain with or without one or more heteroatoms (e.g., O, N, or S) and with or without one or more substituents on atoms of the chain. The Y linker can include linear aliphatic hydrocarbons, branched aliphatic hydrocarbons, cyclic aliphatic hydrocarbons, substituted aliphatic hydrocarbons, unsubstituted aliphatic hydrocarbons, saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, aromatic hydrocarbons, polyaromatic hydrocarbons, substituted aromatic hydrocarbons, heteroaromatic hydrocarbons, ethers, amines, primary amines, secondary amines, tertiary amines, aliphatic amines, carbonyls, carboxyls, amides, esters, amino acids, peptides, polypeptides; substituted or unsubstituted derivatives thereof with or without heteroatoms; or combinations thereof. In some aspects, the Y linker can include C1-C24 alkyl, C2-C24 alkenyl, C2-C24 alkynyl, C1-C24 alkyl ester, C6-C20 aryl, C7-C24 alkaryl, C7-C24 aralkyl, amino, mono- and di-(alkyl) substituted amino, mono- and di-(aryl) substituted amine, alkylamido, arylamido, imino, alkylimino, arylimino, nitro, nitroso, sulfo, sulfonic acid, alkylsulfonyl, arylsulfonyl, alkylsulfinyl, arylsulfinyl, alkylsulfonyl, arylsulfonyl, phosphono, phosphonato, phosphinato, phospho, phosphino; any derivative thereof with or without heteroatoms, any derivative thereof with or without substituents, and combinations thereof.

[0047] In some embodiments, the substituent X or substituent on the linker can be a common substituent, such as hydrogen, alkyl, alkenyl, alkynyl, alkyl ester, aryl, alkaryl, aralkyl, halogen, hydroxyl, thiol, alkoxy, alkenyloxy, alkynyloxy, aryloxy, acyl, alkylcarbonyl, arylcarbonyl, acyloxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, alkylcarbonyl, arylcarbonyl, carboxyl, carboxylic acid, carbamoyl, mono(alkyl)-substituted carbamoyl, di(alkyl)-substituted carbamoyl, monosubstituted arylcarbamoyl, thiocarbamoyl, urea, cyano, isocyano, cyanato, isocyanato, Isothiocyanato, azido, formyl, thioformyl, amino, mono- and di-(alkyl)-substituted amino, mono- and di-(aryl)-substituted amino, alkylamide, arylamide, imino, alkylimino, arylimino, nitro, nitroso, sulfo, sulfonic acid, alkylsulfonyl, arylsulfonyl, alkylsulfinyl, arylsulfinyl, alkylsulfonyl, arylsulfonyl, phosphono, phosphonic acid, phosphinic acid, phosphino, phosphino; any substituent with or without heteroatoms, any substituent including a linear chain, any substituent including a branched chain, any substituent including a ring; derivatives thereof and combinations thereof. For example, Formulas 4 and 5 show alkyl ester linkers substituted with hydroxyl groups.

[0048] For Formulas 2-5: When m is 1, the siloxane monomer is monofunctional; when m is 2, the siloxane monomer is difunctional; when m is 3, the monomer is trifunctional, and so on. Thus, the monomer can be multifunctional, for example, when m is 2 or higher, which allows crosslinking during polymerization. Formula 1 can be monofunctional when only one X is a polymerizable functional group and m is 1, but can be multifunctional in other cases.

[0049] In some embodiments, the siloxane moiety can be a monoacrylate, diacrylate, triacrylate, or other polyacrylate. Diacrylates and above can participate in crosslinking with polymerizable monomers. Consequently, by using a siloxane polyacrylate monomer as a low-surface-energy additive, polymerization can result in crosslinking. Thus, formation of an imaged UV-sensitive material can include crosslinking monomers with a siloxane polyacrylate monomer.

[0050] In some embodiments, the low surface energy additive is not a silicone oil. That is, the low surface energy additive is not a free silicone within the material. In contrast, embodiments include low surface energy additives having reactive functional groups that can participate in polymerization, such that the silicone is covalently coupled to the polymeric material. In some aspects, the low surface energy additive polymerizes upon exposure to UV curing radiation. For example, silicone acrylates or silicone methacrylates can be used. Thus, the low surface energy additive includes functional groups for polymerization and attachment to the polymeric matrix, and includes silicones for reducing surface energy and reducing the peel force of the UV-sensitive layer. Incorporation into the adhesive inhibits the migration of silicone, which can be problematic with silicone oils. Therefore, in some embodiments, silicones or other silicones that do not contain polymerizable functional groups are omitted from the present invention.

[0051] In some embodiments, the relief-forming precursor may include only a single body or a single layer of UV-sensing material. That is, the substrate of the relief-forming precursor may include only a single layer of UV-sensing material with a low-surface-energy additive. Thus, when ready for bonding with a mask, the UV-sensing material is the top layer, and the same UV-sensing material is the only UV-sensing material in the relief-forming precursor. A second UV-sensing layer, whether adjacent or separate, is omitted from the relief-forming precursors described herein. Thus, the entire UV-sensing layer includes the low-surface-energy additive.

[0052] In some embodiments, low surface energy additives, such as silicone acrylates, can be included in the UV sensing material in an amount of about 0.1% to about 5% by weight, or about 0.2% to about 4% by weight, about 0.3% to about 3% by weight, or about 0.4% to about 2% by weight, or about 0.5% to about 1% by weight, or any range of endpoints (e.g., 0.5% to about 2%, etc.), based on the weight of the material.

[0053] In some embodiments, the low surface energy additive can be distributed throughout the matrix.In some aspects, the low surface energy additive can be added to the top surface of the UV sensing material.

[0054] The photosensitive layer with the low surface energy additive can be a positive- or negative-working relief-forming precursor, and typically is negative-working and typically includes a UV-sensitive layer (or photocurable layer or relief-image-forming layer or photosensitive layer, etc.) containing a UV radiation-curable composition that cures or hardens by polymerization or cross-linking upon exposure to curing UV radiation. US '182 (noted above) and the references cited therein provide much detailed information on the various components of UV-sensitive relief-forming precursors.

[0055] Some embodiments of the relief-forming precursor may include a removable cover sheet on the photosensitive layer having a reduced surface energy and a reduced peel force.The reduced surface energy and reduced peel force facilitate removal of the cover sheet.

[0056] In some embodiments, the photosensitive material having reduced surface energy and reduced peel force can be a UV-sensitive layer comprising: an elastic binder; at least one polymerizable or photocurable monomer; a photopolymerization photoinitiator sensitive to UV radiation; and a low surface energy monomer, such as a polymerizable siloxane material described herein. Suitable photoinitiator compositions include, but are not limited to, those described in U.S. Pat. No. 4,323,637 (Chen et al.), U.S. Pat. No. 4,427,749 (Graetzel et al.), and U.S. Pat. No. 4,894,315 (Feinberg et al.). Low surface energy monomers can be added to the photoinitiator composition to form a photosensitive material having reduced surface energy and reduced peel force.

[0057] The elastomeric binder may comprise further polymers or resins that are soluble, swellable or dispersible in aqueous, semi-aqueous or organic solvent developers (as described below) and may include, but are not limited to, natural or synthetic polymers of conjugated dienes, block copolymers, core-shell microgels, and blends of microgels and preformed macromolecular polymers. The elastomeric binder may comprise at least 65 wt% and up to 90 wt% (inclusive) based on the total dry UV sensitive layer weight.

[0058] In some embodiments, the elastomeric binder can be a single polymer or a mixture of polymers (e.g., a homopolymer, a copolymer, a random copolymer, a block copolymer, any having any number of different types of monomers) that can be dissolved, swelled, or dispersed in an aqueous, semi-aqueous, or organic solvent developer. Suitable binders include those described in U.S. Patent No. 3,458,311 (Alles), U.S. Patent No. 4,442,302 (Pohl), U.S. Patent No. 4,361,640 (Pine), U.S. Patent No. 3,794,494 (Inoue), U.S. Patent No. 4,177,074 (Proskow), U.S. Patent No. 4,431,723 (Proskow), and U.S. Patent No. 4,517,279 (Worns). Binders that dissolve, swell or disperse in organic solvent developers include natural or synthetic polymers of conjugated dienes, including polyisoprene, 1,2-polybutadiene, 1,4-polybutadiene, butadiene / acrylonitrile, butadiene / styrene thermoplastic elastomer block copolymers and other copolymers. Block copolymers discussed in U.S. Patent No. 4,323,636 (Chen), U.S. Patent No. 4,430,417 (Heinz) and U.S. Patent No. 4,045,231 (Toda) can be used. The elastomeric binder can be present in an amount of at least about 65wt% of the photosensitive material. As used herein, the term binder includes core-shell microgels and blends of microgels and preformed macromolecular polymers, such as those described in U.S. Patent No. 4,956,252 (Fryd).

[0059] At least one polymerizable monomer can be configured to be compatible with the elastomeric binder to such an extent that a transparent, non-turbid UV-sensitive imageable layer is produced. Polymerizable monomers useful for this purpose are well known in the art and include ethylenically unsaturated polymerizable compounds having a relatively low molecular weight (typically less than 30,000 Daltons). Suitable monomers have a relatively low molecular weight, less than about 5000 Da. Unless otherwise indicated, throughout this specification, molecular weights are weight average molecular weights. Examples of suitable polymerizable monomers include various monoacrylates and polyacrylates, acrylate derivatives of isocyanates, esters, and epoxides. In addition, examples of suitable monomers include tert-butyl acrylate, lauryl acrylate, monoesters and polyesters of acrylic acid and methacrylic acid with alcohols and polyols, for example, alkanols such as 1,4-butanediol diacrylate, 2,2,4-trimethyl-1,3-pentanediol dimethacrylate and 2,2-dimethylolpropane diacrylate; alkylene glycols such as tripropylene glycol diacrylate, butanediol dimethacrylate, hexamethylene glycol diacrylate and hexamethylene glycol dimethacrylate; trimethylolpropane, ethoxylated trimethylolpropane; pentaerythritol such as pentaerythritol triacrylate, dipentaerythritol, etc. Other examples of suitable monomers include acrylate and methacrylate derivatives of isocyanates, esters, epoxides, and the like, such as decamethylene glycol diacrylate, 2,2-bis(p-hydroxyphenyl)propane diacrylate, 2,2-bis(p-hydroxyphenyl)propane dimethacrylate, polyoxyethyl-2,2-bis-(p-hydroxyphenyl)propane dimethacrylate, and 1-phenylethylene-1,2-dimethacrylate. More examples of monomers can be found in U.S. Pat. No. 4,323,636 (Chen), U.S. Pat. No. 4,753,865 (Fryd), U.S. Pat. No. 4,726,877 (Fryd), and U.S. Pat. No. 4,894,315 (Feinberg). The photosensitive material may contain at least 5 wt % to about 25 wt % of the monomer, which may be based on the total dry weight of the photosensitive material.

[0060] The photoinitiator can be any single compound or combination of compounds that is sensitive to ultraviolet radiation and that produces free radicals that initiate polymerization of one or more monomers without over-termination. The photoinitiator can be sensitive to visible light or ultraviolet radiation. The photoinitiator may also be insensitive to infrared and / or visible radiation and may be thermally inactive at 185°C and below. Examples of suitable photoinitiators include substituted and unsubstituted polynuclear quinones. Examples of suitable systems are disclosed in U.S. Patent No. 4,460,675 (Gruetzmacher) and U.S. Patent No. 4,894,315 (Feinberg). The photoinitiator is typically present in an amount of 0.001 wt% to 10.0 wt% based on the weight of the photosensitive material.

[0061] In some embodiments, the photosensitive layer can include: a diblock or triblock copolymer (e.g., an elastomer); at least one photopolymerizable monomer; a photopolymerization initiator; a plasticizer; additives such as stabilizers, inhibitors, colorants, solvents; and a low surface energy monomer, such as a silicone acrylate or silicone methacrylate.

[0062] In some embodiments, the plasticizer can be any suitable plasticizer known in the field of photosensitive layers used as described herein. Examples of suitable plasticizers include aliphatic hydrocarbon oils, such as naphthenic and paraffinic oils, liquid polydienes such as liquid polybutadiene, liquid polyisoprene. Typically, plasticizers are liquids having a molecular weight less than about 5,000Da, but can have a molecular weight of up to about 30,000Da. Plasticizers with low molecular weight will comprise a molecular weight less than about 30,000Da.

[0063] In some embodiments, additives may include rheology modifiers, thermal polymerization inhibitors, stabilizers, inhibitors, tackifiers, colorants, antioxidants, antiozonants, solvents, or fillers. These materials are commonly used in photosensitive layers and examples can be provided in the incorporated references.

[0064] The thickness of the photosensitive layer can vary depending on the type of printing plate desired. In one embodiment, the photosensitive layer can be, for example, about 20-250 mils (500-6,400 microns) thick or greater, more specifically about 20-100 mils (500-2,500 microns) thick.

[0065] In some embodiments, the relief-forming precursor is a flexographic printing plate precursor that includes a suitable UV-curable composition (e.g., a photosensitive material) in a UV-sensitive layer (e.g., a photosensitive layer) that provides a relief image in the flexographic printing plate when exposed through a mask element and developed. Such relief-forming precursors typically include a suitable substrate having a photosensitive material. Examples of commercially available flexographic printing plate precursors include, but are not limited to, FLEXCEL NX flexographic elements available from Miraclon Corporation, FLEXCEL NX flexographic elements available from DuPont (Wilmington, Del.), and FLEXCEL NX flexographic elements available from DuPont (Wilmington, Del.). Flexographic plates, NYLOFLEX° FAR 284 plate available from BASF (Germany), FLEXILIGHT CBU plate available from Macdermid (Denver, Co.), and ASAHI AFP XDI available from Asahi Kasei (Japan) These flexographic printing plate precursors can be modified to include the low surface energy monomers described herein.

[0066] In some embodiments, the relief-forming precursors can also be used to form printed circuit boards, in which a conductive layer (also referred to as a "printed circuit") is formed on a substrate by exposing a pattern indicated by a mask element. Suitable precursors for printed circuit boards typically include a substrate, a metal layer, and a UV-sensitive imageable layer (e.g., a photosensitive material). Suitable substrates include, but are not limited to, polyimide films, glass-filled epoxy or phenolic resins, or any other insulating material known in the art. The metal layer covering the substrate is typically a conductive metal, such as copper or an alloy or metal. The UV-sensitive imageable layer may include a UV-curable resin, a polymerizable monomer or oligomer, a photoinitiator, and a polymer binder. US '182 (as described above) provides more detailed information on printed circuit boards.

[0067] Masks and mask precursors

[0068] A mask for use with a relief-forming precursor having a photosensitive layer with a low surface energy additive can be prepared from the mask precursor. The mask precursor can be prepared and treated with light (e.g., infrared, IR) to form the mask. The mask can then be combined with the relief-forming precursor (e.g., by lamination) and treated, and the mask and the light-treated relief-forming precursor can then be separated from each other. During the separation process, it is important not to damage the relief-forming layer. Thus, the low surface energy additive in the relief-forming layer of the relief-forming precursor can facilitate separation (e.g., delamination) of the mask from the imaged relief-forming layer of the relief-forming precursor.

[0069] Because it has an imageable layer that forms the mask, the mask precursor can be considered an imageable material. The mask precursor can include three basic layers or films as described below, in this order: (a) a transparent polymer support sheet; (b) a light-to-heat conversion (LTHC) layer; and (c) a non-silver halide thermally ablatable imaging layer (IL). Here, the LTHC layer is not ablatable by thermal imaging with light (e.g., IR light). The non-silver halide thermally ablatable imaging layer is ablatable by thermal imaging with light (e.g., IR light), but this thermally ablatable imaging layer does not include silver halide and is therefore a thermally ablatable "non-silver halide" imaging layer. Therefore, the LTHC layer includes a substance that is not ablatable by thermal energy during imaging of the IL layer with IR light. On the other hand, the IL layer includes a thermally ablatable substance. Only these three layers or films are necessary to form a mask element (e.g., referred to as a mask) having a mask image in the IL layer. However, as described below, in some embodiments, a (d) transparent polymer overcoat layer may be disposed directly on the IL, but this optional feature is not required for forming a mask or using a mask image. In contrast, it can help provide abrasion resistance in certain applications.

[0070] A mask precursor for forming a mask element that is ultimately used to form a relief image can be prepared and then processed into a mask as described herein. In some embodiments, the mask precursor 10 is as follows: Figure 1A 1 and 2. As shown, it has (a) a transparent polymer carrier sheet 15 having disposed directly thereon (b) an LTHC layer 20 comprising a non-ablatable binder material having non-ablatable particles 25 as described in more detail below, and (c) an ablatable IL 30 disposed directly on the LTHC layer 20 and positioned to receive light 35 as indicated by the arrows.

[0071] Transparent polymer carrier sheet

[0072] The transparent polymer carrier sheet can be any suitable transparent substrate or film. Useful transparent polymer carrier sheets can be, but are not limited to, transparent polymer films and sheets composed of one or more polymers (e.g., polyesters), including polyethylene terephthalate, polyethylene naphthalate, and fluoropolyester polymers; polyethylene-polypropylene copolymers; polybutadiene; polycarbonate; polyacrylate (a polymer formed at least in part from one or more (meth)acrylate ethylenically unsaturated monomers); vinyl chloride polymers such as polyvinyl chloride and copolymers derived at least in part from vinyl chloride; hydrolyzed or non-hydrolyzed cellulose acetate; and other materials readily understood by those skilled in the art. The transparent polymer carrier sheet can be composed of two or more polymer materials in the form of a blend or composite, as long as the desired transparency and protective properties are achieved. They can be formed as a single polymer film or a laminate of multiple polymer films. Typically, the average dry thickness of the transparent polymer carrier sheet is at least 25 μm and at most 250 μm (inclusive), or typically at least 75 μm and at most 175 μm (inclusive).

[0073] For example, clear polyethylene terephthalate sheets available from various commercial sources are suitable as the clear polymeric carrier sheet.

[0074] If desired, the surface of the transparent polymer carrier sheet can be treated to modify its wettability and adhesion to the applied coating (e.g., LTHC layer coating). Such surface treatments include, but are not limited to, corona discharge treatment and primer coating, as long as the desired transparency (as described above) is achieved.

[0075] If desired, the transparent polymer carrier sheet may also include one or more "first" ultraviolet radiation absorbing compounds (as described below for the LTHC layer or IL). This type of compound or compounds may be the same as or different from the ultraviolet radiation absorbing compounds in the IL (see below). Each useful ultraviolet radiation absorbing compound typically absorbs electromagnetic radiation of at least 150 nm and at most 450 nm (inclusive). These compounds may be present in the transparent polymer carrier sheet in an amount of at least 0.01 wt % and at most 0.1 wt % (inclusive), based on the total dry weight of the transparent polymer carrier sheet.

[0076] In addition, the transparent polymer support sheet may contain one or more "adhesion promoters" to improve adhesion between it and the adjacent LTHC layer. Useful adhesion promoters include, but are not limited to, gelatin, poly(vinylidene chloride), poly(acrylonitrile-co-vinylidene chloride-co-acrylic acid), and polyethyleneimine.

[0077] Non-ablative light-to-heat conversion (LTHC) layer

[0078] The mask precursor also includes a non-ablatable LTHC layer disposed on the transparent polymer carrier sheet and directly between the transparent polymer carrier sheet and the IL. Suitable LTHC layer compositions have three essential components: (i) a first infrared radiation absorbing material; (ii) a non-ablatable cross-linked binder material that is a thermally cross-linked organic polymer that is not ablatable by optical radiation, such as IR radiation, visible radiation, or UV radiation; and (iii) non-ablatable particles that are not ablatable by optical radiation, such as IR radiation, visible radiation, or UV radiation. The LTHC layer is typically disposed on the transparent polymer carrier sheet as a relatively uniform coating (i.e., substantially continuous and having a fairly uniform wet thickness) and then dried, if any solvent is present in the composition formulation.

[0079] The LTHC layer is typically transparent, as that term is defined above. Specifically, the LTHC layer is transparent to the UV radiation used to image the relief-forming precursor, as defined below.

[0080] One or more infrared absorbing materials, collectively referred to herein as "first" infrared radiation absorbing materials, to distinguish them from the second infrared radiation absorbing materials in the IL, as necessary (as described below). The first infrared radiation absorbing material may also be in a transparent polymer carrier sheet. The first and second infrared radiation absorbing materials may be one or more dyes or pigments or mixtures thereof that will provide the desired spectral absorption characteristics and are independently sensitive to electromagnetic radiation within the infrared electromagnetic wavelength range of at least 700 nm and up to 1,500 nm (inclusive) and typically at least 750 nm and up to 1,200 nm (inclusive). Such materials may be granular in nature and dispersed within the non-ablatable cross-linked binder material described below (ii). For example, they may be black dyes or pigments, such as carbon black, metal oxides, and other materials described in US'182 (as described above).

[0081] One suitable IR absorbing pigment is carbon black, which is commercially available in various types and particle sizes. Examples include RAVEN 450, 760ULTRA, 890, 1020, 1250, etc., available from Columbian Chemicals Co. (Atlanta, Ga.), and BLACK PEARLS 170, BLACK PEARLS 480, VULCAN XC72, BLACK PEARLS 1100, etc., available from Cabot Corporation. Other useful carbon blacks are surface functionalized with solubilizing groups. Carbon blacks grafted onto hydrophilic nonionic polymers, such as FX-GE-003 (manufactured by Nippon Shokubai), or carbon blacks surface functionalized with anionic groups, such as 200 or Also useful is ELECTRON(R) 300 (manufactured by Cabot Corporation).

[0082] Useful first infrared radiation absorbing materials also include IR dyes, including but not limited to cationic infrared absorbing dyes and photothermally bleachable dyes. Examples of suitable IR dyes include, but are not limited to, azo dyes, squarilium dyes, crotonate dyes, triarylamine dyes, thiazolium dyes, indolium dyes, oxonolium dyes, oxazolium dyes, cyanine dyes, merocyanine dyes, phthalocyanine dyes, indocyanine dyes, indoletricarbocyanine dyes, oxatricarbocyanine pigments, thiocyanine dyes, thiatricarbocyanine dyes, merocyanine dyes, cryptocyanine dyes, naphthalocyanine dyes, polyaniline dyes, polypyrrole dyes, polythiophene dyes, chalcogenoperylenyl and bis(chalcogenperylenyl)polymethine dyes, oxinolazine dyes, pyrylium dyes, pyrazoline azo dyes, oxazine dyes, naphthoquinone dyes, anthraquinone dyes, quinoneimine dyes, methine dyes, arylmethylene dyes, squaline dyes, azole dyes, crotonine dyes, porphyrin dyes, and any substituted or ionic forms of the foregoing dye classes. Suitable dyes are also described in U.S. Pat. No. 5,208,135 (Patel et al.), U.S. Pat. No. 6,569,603 (Furukawa), and U.S. Pat. No. 6,787,281 (Tao et al.), and EP Publication 1,182,033 (Fijimaki et al.). The formula in paragraph

[0026] of WO 2004 / 101280 shows a general description of a class of suitable cyanine dyes.

[0083] Near-infrared absorbing cyanine dyes are also useful, such as those described in U.S. Pat. No. 6,309,792 (Hauck et al.), U.S. Pat. No. 6,264,920 (Achilefu et al.), U.S. Pat. No. 6,153,356 (Urano et al.), U.S. Pat. No. 5,496,903 (Watanate et al.), the entire disclosures of which are incorporated herein by reference. Suitable dyes can be formed using conventional methods and starting materials or obtained from various commercial sources, including American Dye Source (Baie D'Urfe, Quebec, Canada) and FEW Chemicals (Germany).

[0084] The first infrared radiation absorbing material is typically present in an amount sufficient to provide a transmitted optical density of at least 0.025, and typically at least 0.05, at the wavelength of the exposed electromagnetic radiation (e.g., IR), Typically, this is achieved by including at least 0.1 wt% and up to 5 wt%, inclusive, or typically at least 0.3 wt% and up to 3 wt%, inclusive, based on the total dry weight of the LTHC layer.

[0085] The first infrared radiation absorbing material in the LTHC layer can be the same or a different chemical material than the second infrared radiation absorbing compound incorporated into the IL, as described below. The infrared radiation absorbing material in the LTHC layer can also be different from the infrared absorbing material in the transparent polymer support. In most embodiments, the first and second infrared radiation absorbing materials are the same chemical material. The amounts of the first and second infrared radiation absorbing materials in the imageable material can be the same or different. In most embodiments, they are present in the imageable material in different amounts.

[0086] As described above, the LTHC layer includes a non-ablatable crosslinked binder formed from one or more thermally crosslinked organic polymer binders, which are derived from a thermally crosslinkable organic polymer binder that has been crosslinked. The term "thermally crosslinkable" refers to the presence of crosslinking groups, including, for example, hydroxyl-containing polymers. Particularly useful thermally crosslinkable organic polymers include, but are not limited to, crosslinkable nitrocellulose; crosslinkable polyesters, such as hydroxyl-containing polyesters; polyvinyl alcohol; polyvinyl acetals such as polyvinyl butyral; or combinations of two or more such crosslinkable organic polymer materials. The corresponding non-ablatable crosslinked binder material can be obtained by crosslinking the thermally crosslinkable organic polymer materials.

[0087] The non-ablatable cross-linked binder material formed from a thermally cross-linked organic polymer can be present in the LTHC layer in an amount of at least 40 wt % and up to 90 wt % (inclusive), or more likely in an amount of at least 50 wt % and up to 80 wt % (inclusive), all based on the total dry weight of the LTHC layer.

[0088] The third essential component of the LTHC layer is non-ablatable particles, which are not ablatable by light radiation or heat generated by light radiation, and therefore non-ablatable particles are considered to be non-thermally ablatable particles. Non-thermally ablatable particles are defined as not being thermally ablatable when exposed to light radiation during mask formation or relief image formation. The non-ablatable particles may include an average particle size of at least 0.1 μm and at most 20 μm (inclusive), or at least 5 μm and at most 15 μm (inclusive). The term "average" is used herein to refer to a particle size measurement of dispersed particles, which can be determined according to the manufacturer's specifications or by measuring at least 10 different particles and taking an average.

[0089] The term "non-ablatable" with respect to non-ablatable particles is used herein to indicate that the particles are less sensitive to the wavelength and intensity of laser imaging, as compared to materials that are strongly affected by the laser imaging ablation process used to form the mask. Furthermore, the particles are insensitive to UV radiation during formation of the relief image from the mask and relief-forming precursor. Materials that are sensitive to the laser thermographic ablation process strongly absorb the laser wavelength of the imaging laser and have low thermal decomposition temperatures, making them ablative; such materials are not used in non-ablatable particles. In contrast, the non-ablatable particles used in the present invention do not strongly absorb the laser imaging wavelength and do not have a very low thermal decomposition temperature. Some non-ablatable particles may protrude from the LTHC layer, for example, into the IL, while remaining in the LTHC layer or at least partially embedded therein.

[0090] Non-ablatable particles for the LTHC layer include, but are not limited to, silica, titanium dioxide, zinc oxide particles, or combinations of two or more types of such particles. Silica particles are particularly useful in the practice of the present invention. Furthermore, such non-ablatable particles may be present in the LTHC layer in an amount of at least 0.2 wt % and at most 10 wt % (inclusive), or at least 1 wt % and at most 7 wt % (inclusive), all based on the total dry weight of the LTHC layer.

[0091] Optionally, during formation, the LTHC layer may include one or more thermal crosslinking agents to provide improved handling of the mask element. Such optional thermal crosslinking agents assist in crosslinking the thermally crosslinkable organic binder polymer during coating and drying of the LTHC layer to form a non-ablative crosslinked binder. During formation of the mask element, heat may be used for drying. The thermal crosslinking agent may be present in an amount of at least 5 wt % and up to 25 wt % (inclusive), based on the total dry weight of the crosslinkable polymer crosslinked into the non-ablative LTHC layer. Such materials may include, but are not limited to, melamine formaldehyde resins, dialdehydes, phenolic resins, polyfunctional aziridines, isocyanates (including polyisocyanates), and urea formaldehyde epoxy resins. However, the formed LTHC layer is a crosslinked binder, and thus the formed non-ablative crosslinked material may use all of the crosslinking agent, or no crosslinking agent, or only a small amount of crosslinking agent.

[0092] The LTHC layer typically has an average dry thickness of at least 1 μm and at most 5 μm, inclusive, or typically at least 1 μm and at most 3 μm, inclusive.

[0093] Non-silver halide heat-ablatable imaging layer (IL)

[0094] The IL incorporated into the mask precursor is typically disposed directly on the LTHC layer as a relatively uniform coating (i.e., substantially continuous and having a fairly uniform wet thickness) and then dried, if any solvent is present in the formulation. In most embodiments, the IL is a single coated or applied layer, but in other embodiments there may be multiple sublayers or subcoatings comprising the IL disposed directly on the LTHC layer.

[0095] As the term implies, the IL is substantially free of silver halide. In other words, no silver halide is intentionally added or generated in the IL.

[0096] The IL typically includes one or more ultraviolet radiation absorbing materials (UV light absorbing materials) as essential components. These compounds typically have an absorbance of at least 1.5 and at most 5 (inclusive) in the wavelength range of electromagnetic radiation of at least 300 nm and at most 450 nm (inclusive). In general, useful ultraviolet radiation absorbing materials include, but are not limited to, benzotriazoles, halogenated benzotriazoles, triazines, benzophenones, benzoic acid esters or salts, salicylic acid esters or salts, substituted acrylonitriles, cyanoacrylates, benzyl malonates, oxalanilides, and mixtures thereof. Examples of useful ultraviolet radiation absorbing materials include, but are not limited to, those named (Keystone Aniline Corporation), (Sandoz Chemicals Corp.), Hostavin (Clariant) and UV absorbing dyes or UV stabilizers sold by BASV or Ciba. Examples of useful materials are described in US Pat. No. 5,496,685 (Farber et al.).

[0097] The one or more ultraviolet radiation absorbing compounds may be present in the IL in an amount of at least 10 wt% and up to 40 wt%, inclusive, or typically at least 15 wt% and up to 30 wt%, inclusive, based on the total dry weight of the IL.

[0098] The IL also includes one or more second infrared radiation absorbing materials as a second essential component, which are defined similarly to the first infrared radiation absorbing materials described above for the LTHC layer, and which may be the same as or different from the first infrared radiation absorbing materials. The one or more second infrared radiation absorbing materials may be present in the IL in an amount sufficient to provide a transmitted optical density of at least 0.5, and typically at least 0.75, at the exposure wavelength. Typically, this is achieved by including at least 3 wt % and at most 20 wt % (inclusive) of the one or more second infrared radiation-sensitive compounds, based on the total dry weight of the IL.

[0099] The IL may optionally include one or more fluorocarbon additives for improving the production of halftone dots (i.e., pixels) having well-defined, generally continuous, and relatively sharp edges. Examples and amounts of useful fluorocarbon additives are provided at

[0087] to

[0089] of US '182 (noted above).

[0100] Other optional components of the IL include, but are not limited to, plasticizers, coating aids or surfactants, dispersing aids, fillers, and colorants, as described in

[0094] to

[0096] of US '182 (noted above), all of which are well known in the art. For example, the IL may also contain one or more fluorocarbon additives or one or more non-athermal colorants.

[0101] All essential and optional components of the above-described IL are dispersed in one or more ablatable polymeric binder materials, including synthetic and natural polymeric materials that are ablatable when exposed to light radiation (e.g., IR radiation, visible radiation, or UV radiation). In some aspects, the ablatable polymeric binder in the IL is not cross-linked and is therefore a non-cross-linked binder. Such materials are capable of dissolving or dispersing the essential and optional components in a uniform manner throughout the IL. The one or more ablatable polymeric binder materials can be present in an amount of at least 25 wt% and up to 75 wt% (inclusive), or typically at least 35 wt% and up to 65 wt% (inclusive), based on the total dry weight of the IL.

[0102] Useful ablatable polymer binder materials include, but are not limited to, materials such as those described in

[0081] to

[0085] of US '182. These materials may also be referred to as "binders," as described in

[0081] of US '182. Examples of such materials include, but are not limited to, acetyl polymers such as those available from Solution, Inc. (St. Louis, Mo.) and Poly(vinyl butyral) is available as MACROMELT® B-76, and acrylamide polymers are available as MACROMELT 6900 from Henkel Corp. (Gulph Mills, Pa.) Pressure-sensitive adhesive polymers may also be used for this purpose.

[0103] In some embodiments, it is advantageous to use a binder material in the IL that readily thermally combusts or thermally ablates and produces gases and volatile fragments at temperatures below 200° C. Examples of such materials are thermally ablatable nitrocellulose, polycarbonates, poly(cyanoacrylates), polyurethanes, polyesters, polyorthoesters, polyacetals, and copolymers thereof (see, e.g., U.S. Pat. No. 5,171,650 to Ellis et al., column 9, lines 41-50, the disclosure of which is incorporated herein by reference), which may be non-crosslinked.

[0104] Other useful ablatable materials for ILs have hydroxyl groups (or hydroxyl polymers), as described at

[0082] to

[0084] of US '182 (noted above), such as polyvinyl alcohol and cellulosic polymers (e.g., nitrocellulose). Still other useful polymers are non-crosslinkable polyesters, polyamides, polyurethanes, polyolefins, polystyrenes, polyethers, polyvinyl ethers, polyvinyl esters, and polyacrylates and polymethacrylates having alkyl groups of 1 and 2 carbon atoms.

[0105] Particularly useful ablatable materials for ILs include, but are not limited to, polyurethanes, poly(vinyl butyral), (meth)acrylamide polymers, nitrocellulose, polyacetals, poly(cyanoacrylates), polymers derived at least in part from any of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate, or combinations of two or more of these materials.

[0106] The IL may have an average dry thickness of at least 0.5 μm and at most 5 μm (inclusive), or typically at least 0.8 μm and at most 2.5 μm (inclusive).

[0107] Transparent polymer topcoat

[0108] In some embodiments, the mask precursor optionally includes a transparent polymer overcoat layer disposed directly on the IL opposite the LTHC layer. Although such a transparent polymer overcoat layer is not essential to the advantages of the present invention. The transparent polymer overcoat layer typically includes one or more transparent film-forming polymers or resins, including but not limited to methacrylic acid copolymers (e.g., copolymers of ethyl methacrylate and methacrylic acid) and one or more fluoropolymer particles dispersed therein, as described, for example, in U.S. Patent No. 6,259,465 (Tutt et al.), the disclosure of which is incorporated herein by reference. Due to the presence of the fluoropolymer particles, the transparent polymer overcoat layer can provide wear resistance during processing. It can also act as a barrier layer to prevent chemicals from migrating from the mask element to the relief-forming precursor when they are in full optical contact.

[0109] When present, the transparent polymeric overcoat layer may be directly attached to the IL and may have an average dry thickness of at least 0.05 μm and at most 1 μm, inclusive.

[0110] Forming mask elements

[0111] In some embodiments, a mask can be formed by creating exposed and non-exposed regions in the IL of a mask precursor as described herein. The choice of imaging mechanism will determine the possible variations in the formed mask image, as described below.

[0112] The mask precursor can be exposed to ablative light energy in selected areas to ablate the IL layer, also referred to as "imagewise exposure". In some embodiments, imagewise exposure can be achieved using thermal radiation from a thermal or infrared laser that is scanned or rastered under computer control. Any known scanning device can be used, including flatbed scanners, external drum scanners, and internal drum scanners. In these devices, the mask precursor material is fixed to a drum or plate, and the laser beam is focused to a point on the IL that can impinge on the mask precursor material. Two or more lasers can scan different areas of the IL simultaneously.

[0113] For example, the mask precursor material can be exposed to infrared radiation, for example, within an electromagnetic wavelength range of at least 700 and up to 1500 nm (inclusive). Such mask precursor materials include one or more second infrared radiation absorbing materials in the IL as described above to provide sensitivity to infrared radiation. In these embodiments, the mask precursor material can be appropriately mounted on an infrared imager and exposed to infrared radiation using an infrared laser (e.g., a diode laser or an Nd:YAG laser) that can be scanned under computer control. Suitable infrared imagers include, but are not limited to, the TRENDSETTER imagers and ThermoFlex flexographic CTP imagers available from Eastman Kodak Company for CTP lithographic applications and for imaging flexographic elements, the DIMENSION image typesetters available from Presstek (Hudson, NH) for CTP lithographic applications, the IR-T imagers available from Esko-Graphics (Kennesaw, Ga.), and the IR-T imagers available from Esko-Graphics (Kennesaw, Ga.). A digital imager (CDI SPARK) and an OMNISETTER imager available from Misomex International (Hudson, NH) were used to image the flexographic elements.

[0114] The exposure step Figure 1A Some embodiments are described in which the mask precursor material 10 is exposed to infrared radiation 35 in an image-wise manner to provide Figure 1B , and corresponding to the mask image, are exposed areas 40 and non-exposed areas 42 shown in the mask element 36 shown in FIG. As shown, the exposed areas 40 are ablated and removed from the non-exposed areas 42. In this way, the exposed areas form the mask image.

[0115] If desired, the step of forming a mask image may further include the step of removing exposed or non-exposed areas from the IL. In some embodiments, the exposed areas of the IL are removed, for example, by ablating the exposed material in the IL. In this mechanism, the exposed areas of the IL are removed from the mask element by generating gases during ablation to leave behind the mask image. The IL may contain a specific binder (e.g., non-crosslinked) that decomposes to rapidly generate gases when exposed to heat (e.g., heat generated by IR laser irradiation). This action differs from other mass transfer techniques in that it is a chemical change rather than a physical change, resulting in almost complete transfer of the IL, rather than partial transfer.

[0116] In other embodiments, not shown, a mask image can be formed on the carrier sheet (and the LTHC layer disposed thereon) by creating exposed and non-exposed areas in the IL and selectively removing the non-exposed areas.

[0117] In some embodiments, the mask image in the IL of the mask element can be cured by heat treating the mask element, provided that the properties of the mask element are not adversely affected. Heat treatment can be performed in a variety of ways, including but not limited to storage in an oven, hot air treatment, or contact with a heated platen or heated roller device. Heat treatment is not required for curing.

[0118] In still other embodiments, a mask image can be formed in the IL as described above, and the exposed areas can be transferred to a receptor sheet, which is then removed from the mask element before contacting it with the relief-forming precursor. Such procedures are well known in the art.

[0119] In a lift-off imaging mechanism, the exposed areas of the IL can be removed from the carrier sheet (and the LTHC layer disposed thereon) using a suitable receptor sheet based on the different adhesion properties of the IL. After image-wise exposure of the mask precursor, the receptor sheet is separated from the carrier sheet, and the exposed or non-exposed areas remain in the mask element.

[0120] Forming a relief image

[0121] After forming the mask element and relief-forming precursor as described above, the mask element is brought into full optical contact with the relief-forming precursor, which includes a photosensitive layer having a low surface energy additive and is sensitive to curing UV radiation. This approach can be achieved by placing the mask element on the relief-forming precursor, or vice versa, as described in more detail below. For example, contact and coupling of the mask element to the relief-forming precursor can be achieved using laminating equipment and processing. Vacuum stretching of the mask element onto the relief-forming precursor can also be performed with or without lamination to achieve the desired full optical contact.

[0122] According to some embodiments of the present invention, Figures 1A to 1E As mentioned above, Figure 1A A mask precursor 10 is shown which is exposed to infrared radiation 35 to form a mask element 36 ( Figure 1B ).

[0123] exist Figure 1C , mask element 36 includes IL layer 15 (e.g., having non-ablatable particles) on LTHC layer 20, which is located on ablated IL layer 30 having a mask image formed therein. Mask element 36 is shown in intimate or complete optical contact with relief-forming precursor 55 to provide relief image-forming assembly 50. Relief-forming precursor 55 includes UV-sensing layer 60 (e.g., a photosensitive relief-forming layer having a low surface energy additive and sensitive to curing UV radiation), typically carried on substrate 65.

[0124] Figure 1D The step of exposing the relief image forming assembly 50 to UV radiation 70, as indicated by the arrows, is shown. The UV radiation 70 passes through the transparent polymer carrier sheet 15 of the mask element 36, the LTHC layer 20, and the exposed areas of the IL 30 (e.g., the portion of the IL layer of element 40 that was removed) to induce photocuring in the UV sensitive layer 60 of the relief-forming precursor 55.

[0125] After UV exposure, the masking element 36 may be removed from the UV sensitive layer 60 of the relief-forming precursor 55, and a development scheme may provide a relief image in the UV sensitive layer 60 ( Figure 1E As shown, the relief image includes relief image peaks 75 and relief image valleys 80 in the UV sensitive layer 60 .

[0126] laminated

[0127] As described above, the mask element and the relief-forming precursor can be in full optical contact to provide an air-free interface at the shared interface. Typically, this is achieved by laminating the mask element to the UV-sensitive layer of the relief-forming precursor prior to UV exposure, applying appropriate pressure or heat, or both, to form an air-free or gap-free interface. However, when the relief-forming precursor includes a UV-sensitive layer 60 having a low surface energy additive as described above, a lamination procedure may not be required. As described above, vacuum drawing of the mask element onto the relief-forming precursor can then be used.

[0128] Commercially available laminators that provide both heat and uniform pressure may be used, including but not limited to the KODAK Model 800XL APPROVAL laminator available from Eastman Kodak Company (Rochester, NY). The CODOR LPP650 laminator available from CODOR (Amsterdam, Holland) and the LEDCO HD laminator available from Filmsoury (Casselbury, FL) are also useful. If the transparent polymer overcoat is directly attached to the IL of the mask element material, it may be removed prior to lamination or other operations that bring the mask element into full optical contact with the relief-forming precursor. The relief image-forming assembly formed by coupling the mask element and the relief-forming precursor may be fed into the laminator at the desired speed, temperature, and pressure.

[0129] Useful laminating (laminator) apparatus and methods of using the same are described, for example, in U.S. Pat. No. 7,802,598 (Zwadlo et al.), the disclosure of which is incorporated herein by reference. As described herein, a pre-pressed flexographic plate laminator can be used to laminate a mask element ("masking film") to a relief-forming precursor ("pre-pressed flexographic printing plate") by applying a balanced, non-distorting, optimized lamination force to achieve full optical contact while minimizing lateral deformation.

[0130] In some embodiments, the relief-forming precursor does not have a separating layer, spacer layer, or anti-stick layer on the UV-sensitive relief-forming layer, so pressure alone is sufficient to achieve an air-free interface because the relief-forming layer with the low surface energy additive within the relief-forming layer can still be tacky, or act as a pressure-sensitive adhesive, due to the presence of the polymerizable monomer. The amount of the low surface energy additive can be adjusted within the parameters defined herein to obtain a desired or optimal amount of tack. Excessive low surface energy monomer may result in a reduced surface tack, and thermal lamination can then be used to provide optical contact coupling with the mask.

[0131] UV exposure

[0132] After achieving full optical contact between the mask element and the relief-forming precursor as described above, the relief-forming precursor can be exposed to curing UV radiation through the mask element to form an imaged relief-forming precursor having exposed areas and non-exposed areas in the UV-sensitive layer. The exposed areas are cured and solidified by polymerization of the monomers in the UV-sensitive layer. The unexposed areas remain uncured and the monomers are not polymerized. Thus, uniformly emitted curing UV radiation is projected onto the relief-forming precursor through the mask image, which preferentially blocks some of the UV radiation through the remainder of the IL layer. In the unmasked (exposed) areas, the curing UV radiation will cause the UV-sensitive composition in the IL to harden or cure. Therefore, the mask image is substantially opaque to the exposing or curing UV radiation, meaning that the mask image should have a transmitted optical density of 2 or greater, and typically 3 or greater, in the unexposed areas. The remainder of the IL layer still includes UV-sensitive material to absorb UV light and block it. Unmasked (exposed) areas of the UV-sensing composition may be substantially transparent, meaning that they should have a transmitted optical density of 0.5 or less, or even 0.1 or less, more typically at least 0.5 and at most 0.1 (inclusive), or at least 0.1 and at most 0.3 (inclusive). The transmitted optical density can be measured using an appropriate filter on a densitometer, such as a MACBETH TR 927 densitometer.

[0133] Typically, exposure of the relief-forming precursor through the mask element is accomplished by flood exposure from a suitable UV radiation source. Exposure can be performed in the presence of atmospheric oxygen. Exposure under vacuum is unnecessary because full optical contact is already established.

[0134] In the manufacture of relief imaging elements (e.g., flexographic printing plates), one side of a relief-forming precursor can typically first be exposed to curing UV radiation through its transparent substrate (referred to as "back exposure") to produce a thin, uniform cured layer (e.g., relief image valleys 80) on the substrate side of the UV-sensitive layer. The relief-forming precursor is then exposed to curing UV radiation through a masking element containing a mask image, thereby inducing UV induction to cause hardening or curing in the unmasked (exposed) areas. The unexposed and uncured areas of the UV-sensitive layer can then be removed by a development process (described below), leaving behind cured or hardened areas (e.g., relief image peaks 75) that define the shape and size of the predetermined desired pattern peaks 75 and valleys 80 of the relief image printing surface. Back exposure can be performed before or after full optical contact is made between the masking element and the relief-forming layer.

[0135] The wavelength or wavelength range suitable for curing UV radiation will be determined by the electromagnetic sensitivity of the relief-forming layer. In some embodiments, the UV curing radiation may have one or more wavelengths within the range of at least 150 nm and at most 450 nm (inclusive), or more typically at least 300 nm and at most 450 nm (inclusive). Sources of flood or bulk exposure UV radiation include, but are not limited to, carbon arcs, mercury vapor arcs, fluorescent lamps, electronic flash devices, and photographic floodlights. UV radiation from mercury vapor lamps and sun lamps is particularly useful. Representative UV radiation sources include a SYLVANIA 350 BLACKLIGHT fluorescent lamp (FR 48T12 / 350VL / VHO / 180, 115 watts) having a central emission wavelength of approximately 354 nm, available from Topbulb (East Chicago, Ind.), and a BURGESS exposure frame model 5K-3343V511 with an ADDALUX 754-18017 lamp, available from Burgess Industries, Inc. (Plymouth, Mass.).

[0136] Other suitable UV radiation sources include platesetters that can be used to expose the relief-forming precursor to radiation and to develop the imaged relief-forming material after exposure to radiation. Examples of suitable platesetters include, but are not limited to, the KELLEIGH MODEL 310 platesetter available from Kelleigh Corporation (Trenton, NJ) and the GPP500F platesetter available from Global Asia Ltd.

[0137] The exposure time through the mask element will depend on the nature and thickness of the UV-sensitive layer of the relief-forming precursor and the source and intensity of the UV radiation. For example, in one embodiment, a FLEXCEL-SRH plate precursor available from Eastman Kodak Company can be mounted on a KELLEIGH MODEL 310 platesetter and exposed to UV-A radiation for approximately 20 seconds through the transparent support to produce a thin, uniform cured layer on the support side of the relief-forming precursor. The mask element and the relief-image-forming assembly of the relief-forming precursor can then be exposed to UV radiation through the mask element for approximately 14 minutes. The mask image information is thus transferred to the relief-forming precursor (e.g., a flexographic plate precursor).

[0138] Separating the mask from the UV sensing layer

[0139] Typically, the methods described herein may further comprise removing the mask element from full optical contact with the imaged relief-forming precursor after UV exposure and before development. This may be accomplished using any suitable means, such as by peeling the two elements apart. For example, this may be accomplished by pulling the mask element away from the imaged relief-forming precursor.

[0140] In some embodiments, after UV exposure, the mask element can be removed from the relief-forming layer by peeling the mask element from the relief-forming layer. This can be achieved by providing support to one of the mask element or the relief-forming precursor and then applying a pulling force to the edge or end of the other mask element or the relief-forming precursor (e.g., the relief-forming layer). The low surface energy additive can provide a lower surface energy and a lower peeling force, making separation easier without damaging the mask element of the relief-forming layer. In this way, the peeling or separation promoted by the lower surface energy and the lower peeling force can inhibit the delamination of the mask element, which allows the mask element to be reused. In addition, the lower surface energy and the lower peeling force can inhibit the degradation and undesirable breakage of the peaks of the relief-forming layer.

[0141] In some embodiments, the mask element can be delaminated from the relief-forming precursor, for example, by delaminating from the relief-forming layer. In these embodiments, the mask element is laminated to the relief-forming layer. Then, after UV curing, the mask is delaminated from the relief-forming layer. However, this delamination does not necessarily mean that the mask itself delaminates, resulting in different layers of the mask element delaminating from one another. Here, due to the presence of the low-surface-energy additive, the mask element delaminates from the relief-forming layer as a whole. Therefore, when the mask is peeled from the relief-forming layer, the mask itself does not delaminate or become damaged. Similarly, the relief-forming layer does not delaminate from the relief-forming precursor.

[0142] In some embodiments, the relief-forming precursor can omit a transparent release layer on the UV-sensitive layer. The low-surface-energy additive can now provide easier release of the mask from the relief-forming precursor. Thus, the UV-sensitive relief-forming layer can be in direct contact with the mask element, allowing separation to separate the mask directly from the relief-forming layer. The low-surface-energy additive can reduce the surface energy and adhesion potential, allowing for a clean separation without damaging the mask element or the relief-forming precursor.

[0143] In some embodiments, the relief-forming layer can allow for less force to be applied during stripping of the mask and imaging of the relief image precursor (e.g., a flexographic printing plate precursor). The lesser force is comparable to that of a relief-forming layer without the low surface energy additive of the present invention. Thus, the low surface energy additive reduces the surface energy and the stripping force compared to the same composition without the low surface energy additive. The mask can be stripped more quickly and completely from the relief-forming precursor, with little or no residual material. This effect provides for faster development of the imaged relief image precursor, as there is little or no residual material to inhibit the development process. Because stripping is easier, the flexographic imaging assembly requires minimal handling and pressing pressure, and the process can be easily performed at room temperature. Therefore, no heating is required during the curing process.

[0144] A flexographic printing plate assembly with a UV-sensitive layer comprises a unique combination of materials that enables rapid and complete mask stripping. "Complete" means that at least 95%, preferably at least 98%, at least 99%, or 100% of the mask is stripped, leaving little or no residual material. The composition of the UV-sensitive layer provides a peel force relative to the mask element comprising the mask image of less than about 73 g / inch, preferably less than about 60 g / inch, and more preferably less than about 55 g / inch. The relief-forming layer may have a measurable peel force relative to the mask, for example, at least about 1 g / in, at least about 5 g / in, or at least about 10 g / in.

[0145] In some embodiments, the relief-forming layer is a solvent-washable plate precursor and comprises a peel force relative to a mask element comprising a mask image of less than about 73 g / in, preferably less than about 60 g / in, and more preferably less than about 55 g / in. The solvent-washable relief-forming layer may have a measurable peel force relative to the mask, for example, at least about 1 g / in, at least about 5 g / in, or at least about 10 g / in.

[0146] In some embodiments, the relief-forming layer is a water-washable plate precursor and comprises a peel force relative to a mask element comprising a mask image of less than about 40 g / in, preferably less than about 30 g / in, and more preferably less than about 20 g / in. The water-washable relief-forming layer may have a measurable peel force relative to the mask, for example, at least about 1 g / in, at least about 5 g / in, or at least about 10 g / in.

[0147] The peel force value can be measured by mounting a 2.54 cm wide and 25.4 cm long mask strip laminated to a UV-sensitive layer with a low-surface-energy additive from a flexographic printing plate that has been exposed to UV light on an IMASS SP-2000 Slip / Peel Tester (MASS Inc., Accord, Mass.) using double-sided tape, with the printing plate facing downward. The mask's initial edge is pulled away from the printing plate and mounted in the force gauge. The maximum peel force of the film is measured in grams per linear inch (2.54 cm) at a peel angle of 180° and a peel speed of 2 cm / sec.

[0148] In some embodiments, a mask element containing a mask image is removed from the UV-exposed, UV-sensitive, relief-forming layer of a flexographic printing plate precursor by peeling it off at the interface of the mask element and the relief-forming layer. This peeling process can be performed using vacuum hold-in-place as described in U.S. Patent No. 7,802,598. The mask element is then pulled away from the printing plate at a corner at a rate of 2 to 10 cm / sec at a peel angle of 150-180°, thereby substantially pulling the imaged film back on itself, while maintaining the imaged film near the vacuum table surface in a continuous motion until the entire mask element is removed from the UV-sensitive layer of the printing plate. In the practice of the present invention, at least 95% by weight of the dry mask element is removed during this operation, so it is generally said that the mask element is "completely" or substantially completely removed from the exposed, radiation-curable layer of the precursor. "Completely" means that at least 95%, preferably at least 98%, at least 99%, or 100% of the mask is peeled off, leaving little or no residual material.

[0149] development

[0150] After the masking element is removed from the relief-forming layer, the imaged relief-forming precursor is then typically developed with a suitable developer (or processing solution or "washing solution") to form a relief image. Development serves to remove the unexposed (uncured) areas of the UV-sensitive layer, leaving a defined relief image. Figure 1E The exposed (cured) areas of the relief image are shown.

[0151] Any known organic solvent-based or water-based developer can be used in this processing step, including known developers containing primarily chlorinated organic solvents. However, other useful developers are primarily non-chlorinated organic solvents. By "primarily" is meant that greater than 50% (by volume) of the developer comprises one or more non-chlorinated organic solvents, such as aliphatic hydrocarbons and long-chain alcohols (i.e., alcohols having at least 7 carbon atoms). The remainder of the developer can be a chlorinated organic solvent known in the art for this purpose.

[0152] Some useful developers are primarily so-called "perchloroethylene alternative solvents" (PAS), which are typically volatile organic compounds typically composed of a mixture of aliphatic hydrocarbons and long-chain alcohols. Examples of such commercially available solvents include, but are not limited to, PLATESOLV available from Hydrite Chemical Co. (Brookfield, Wisc.), HYDROLYZE available from BASF (Germany), and HYDROLYZE available from BASF (Germany). Available from DuPont (Wilmington, DE) Available from DuPont (Wilmington, Del.) and SOLVIT° QD available from MacDermid (Denver, Co.).

[0153] Other useful developers are described in U.S. Pat. No. 5,354,645 (Schober et al.) and U.S. Pat. No. 6,248,502 (Eklund), the disclosures of which are incorporated herein by reference, and include one or more diethylene glycol dialkyl ethers, acetates or alcohols, carboxylates, and alkoxy-substituted carboxylates. Still other useful developers are described in U.S. Pat. No. 6,162,593 (Wyatt et al.), which describes a developer including diisopropylbenzene (DIPB).

[0154] Additional useful developers are described in U.S. Patent No. 6,582,886 (Hendrickson et al.) and contain methyl esters alone or in mixtures with cosolvents, such as various alcohols soluble in the methyl esters. U.S. Patent Application Publication No. 2010 / 0068651 (Bradford) describes useful developers containing dipropylene glycol dimethyl ether (DME) alone or in combination with various cosolvents, such as alcohols and aliphatic dibasic acid ethers. Other useful developers are described in U.S. Patent Application Publication No. 2011 / 0183260 (Fohrenkamm et al.). Other useful developers are described in U.S. Patent No. 8,771,925 (Fohrenkamm et al.), which includes diisopropylbenzene and one or more organic cosolvents, one of which is an aliphatic dibasic acid ester. Still other useful developers are described in U.S. Pat. No. 9,005,884 (Yawata et al.), where the processing solution may include an alkali metal salt of a saturated fatty acid having 12 to 18 carbon atoms and an alkali metal salt of an unsaturated fatty acid having 12 to 18 carbon atoms, with the weight ratio of the first fatty acid salt to the second fatty acid salt being 20:80 to 80:20.

[0155] Still other useful developers are described in co-pending and commonly assigned U.S. Patent No. 10,248,025 (Ollmann et al.). Such a flexographic developer may include: a) a fatty acid composition consisting of one or more saturated or unsaturated fatty acids or alkali metal salts thereof, each saturated or unsaturated fatty acid or alkali metal salt thereof independently having from 12 to 20 carbon atoms, the fatty acid composition being present in an amount of at least 0.25 wt% and at most 2.0 wt% (inclusive), and at least 85 wt% of the fatty acid composition consisting of one or more C18 mono- or polyunsaturated fatty acids or alkali metal salts thereof; b) an aminopolycarboxylic acid or alkali metal salt thereof in an amount of at least 0.05 wt% and at most 0.30 wt% (inclusive); c) a buffer compound in an amount of at least 0.5 wt% and at most 0.60 wt% (inclusive); and d) water.

[0156] Development can be carried out under known conditions, for example, for at least 1 minute and up to 20 minutes (inclusive) at a temperature of at least 20° C. and up to 32° C. (inclusive). The type of development equipment and specific developer used will dictate specific development conditions and can be adjusted by those skilled in the art.

[0157] In some cases, post-development treatment of the relief image in the imaged relief-forming precursor may be appropriate. Typical post-development treatments include drying the relief image to remove any excess solvent and post-curing by exposing the relief image to curing radiation to cause further hardening or cross-linking. The conditions of these processes are well known to those skilled in the art. For example, the relief image can be blotted or wiped dry, or dried in a forced air or infrared oven. Drying times and temperatures will be apparent to those skilled in the art. Post-curing can be performed using the same type of UV radiation as was previously used to expose the relief-forming precursor through the imaged mask material.

[0158] If the relief image surface is still tacky, detackification (or "light finishing") may be used. Such treatments, for example by treatment with bromine or chlorine containing solutions or exposure to UV or visible radiation, are well known to those skilled in the art.

[0159] The resulting relief image can have a depth of at least 2% and up to 100% (inclusive) of the original thickness of the UV-sensitive layer (e.g., if the layer is disposed on a substrate). For flexographic printing plates, the maximum dry depth of the relief image can be at least 150 μm and up to 1,000 μm (inclusive), or typically at least 200 μm and up to 500 μm (inclusive). For printed circuit boards, the UV-sensitive layer can be completely removed in exposed or non-exposed areas to reveal the underlying metal layer. In these components, the maximum depth of the relief image depends on the dry thickness of the UV-sensitive layer. Advantageously, in any embodiment, the relief image can have a shoulder angle greater than 50°.

[0160] Thus, in some embodiments, the method is performed where the relief-forming precursor is a UV-sensitive flexographic printing plate precursor, and the precursor is imaged and developed to provide a flexographic printing plate having a relief image layer formed from the relief-forming layer of the relief-forming precursor. Similarly, relief printing plates can be prepared from appropriate precursor elements.

[0161] The relief image layer can also include a low surface energy additive that is integrated or otherwise bound (e.g., polymerized) to the polymer of the relief image layer after development. Thus, the ready-to-use release image layer can have a low surface energy portion present on the exposed surface. This results in the relief image layer having an exposed surface where the siloxane is exposed, which provides a relatively low surface energy as described below.

[0162] In some embodiments, the relief image layer can receive ink during the process of creating the relief image with ink. The ink can be applied to the relief image layer in an appropriate amount to help the ink have reduced printing dot gain. Thus, a relief image having polymerized low surface energy portions can help reduce printing dot gain. This overcomes the problem of flexographic printing plates having excessively high printing dot gain.

[0163] In some embodiments, the relief image layer with ink can be cleaned to remove the ink for various reasons, such as changing colors or cleaning the surface to apply new ink. In addition, changing the ink can help remove any particles in the relief image layer that may have been generated during the process. Low surface energy portions can be present on the surface of the relief image layer to facilitate cleaning of the ink and allow for easier removal of ink from surface features (e.g., protrusions, depressions, etc.) after printing. This provides a clean relief surface so that the plate can be stored and then used for printing again.

[0164] Those skilled in the art can readily see that such ink elements have various utilities in a variety of industries, including flexographic printing of various packaging materials. Example

[0165] Preparation of relief-forming precursors

[0166] The polymer / binder, along with the plasticizer, was introduced into a double-arm sigma mixer heated to 120°C. Once the plasticizer was absorbed into the binder and the mixture reached a homogeneous or "semi-melt" state, the remainder of the premixed formulation, including monomers / stabilizers / photoinitiators / inhibitors / colorants / solvents, was gradually added as a solution for Comparative Example 1. Furthermore, a silicone acrylate monomer, such as a silicone polyether acrylate (e.g., TEGO RAD2250 from Evonik, referred to herein as TR2250), was further introduced as a solution in cyclopentanone for the inventive examples described herein. Thus, TR2250 was omitted from the comparative examples, while TR2250 was included in the inventive examples. The composition was mixed for an additional 1-1.5 hours until no visible binder particles were observed and the melt was homogeneous. Once the melt reached mixing temperature, the mixer temperature was turned off, and the material was allowed to "cool" in the mixer without mixing for a period of time (to approximately 75°C) before discharge.

[0167] Once discharged from the mixer, the necessary amount of sensitized photopolymer mixture is measured and placed between the base film and the cover sheet. The correct plate thickness is obtained using an appropriate shim gauge, which is placed between the base and the cover film. This sandwich structure (base film, sensitized photopolymer, and cover film) is then placed in a hot metal press set to approximately 240°F and pressed at a pressure of approximately 20 tons for 2-3 minutes to produce the photosensitive printing plate precursor.

[0168] Comparative Example 1

[0169] Formulations were prepared without the low surface energy monomer TR2250. A solvent-processable photosensitive flexographic printing precursor was prepared according to the above procedure using a photosensitive polymer composition similar to that described in US Pat. No. 6,897,006, wherein the photosensitive polymer composition consisted of 60 parts by mass of a triblock copolymer (trade name Kraton 405), 30.17 parts by mass of a polybutadiene plasticizer (trade name Nisso PB2000, manufactured by Nippon Soda Co., Ltd., and Polyvest 110 manufactured by Evonik), a total of 0.91 parts by mass of stabilizers and inhibitors (BHT Swanox, Nonflex EBP, Q-1301), 0.13 parts of a solvent (THF), 0.92 parts of a colorant (Diaresin blue and NBT-1150 green), 1.34 parts of a biphenyl dimethyl ketal photoinitiator (Omnirad 651), and a total of 7.69 parts of a crosslinkable monomer (HDDA and TMPTA).

[0170] Invention Example 1

[0171] The formulation was prepared with the low surface energy silicone polyether acrylate TEGO RAD 2250. A flexographic printing plate photopolymer was obtained as described in Comparative Example 1, except that 0.5% of low surface energy silicone polyether acrylate (TR2250) was also added and cyclopentanone was used as solvent instead of the solvent (THF).

[0172] Comparative Example 2

[0173] Flexcel NX Ultra photopolymer plate precursor commercially available from Miraclon Corporation was used as Comparative Example 2 for Inventive Example 2.

[0174] Invention Example 2

[0175] To test the effect of low surface energy monomers (e.g., silicone acrylates) in reducing / improving delamination of mask elements in water-washable flexographic printing plate precursors, TR2250 was introduced into a Flexcel NX Ultra photopolymer plate precursor (e.g., a UV-sensitive material) by scraping off the photopolymer mixture from the Flexcel NX Ultra photopolymer plate precursor and placing the photopolymer mixture in a sigma mixer set at 120°C. The mixture quickly reached a semi-molten state, into which 1 part of TR2250 was slowly added. The composition was then further mixed for one hour, then allowed to cool and finally removed from the mixer. A UV-curable material for a flexographic photosensitive plate precursor was then obtained by the above procedure using an appropriate amount of the mixture (now additionally including TR2250).

[0176] Comparative Example 3

[0177] As a comparative / test example, aminofunctional silicone oil (poly(dimethylsiloxane), bis(3-aminopropyl) endcapped, similar to that described in US 8,114,566) from Sigma-Aldrich was incorporated into the photopolymer composition of Comparative Example 1 at 0.5 parts.

[0178] After removing the cover sheet from the photopolymer plate precursor, the imaged mask was laminated to the front imaging surface (relief-forming layer) of the flexographic printing plate precursor. Lamination was performed using a commercially available Flexcel NX Wide 5080 laminator with standard settings so that the mask element was in direct and intimate contact with the front imaging surface of the UV-sensitive layer of the relief-forming precursor. After lamination, the mask element and the relief-forming precursor were uniformly exposed through the back surface, followed by front image exposure through the mask element. Numerous bubbles were observed to form at the interface of the mask and the relief-forming layer. It is known that any bubble formation is detrimental to image reproduction from the mask to the UV-sensitive material because it creates a gap between the mask image and the relief-forming material, and the intimate contact between the mask and the relief-forming layer is disrupted. In contrast, the examples according to the present invention having the siloxane monomer did not form bubbles.

[0179] Peel force measurement

[0180] The peel force measurements were performed according to the method described in US Pat. No. 10,207,491. After removing the cover sheet from the relief-forming layer of the relief-forming precursor, the imaged mask was laminated to the front imaging surface of the UV-sensitive layer. Lamination was performed using a commercially available Flexcel NX Wide 5080 laminator with standard settings to bring the mask element into direct and intimate contact with the front imaging surface of the relief-forming layer. After lamination, the mask element and relief-forming precursor were uniformly exposed through the back surface, followed by front image exposure through the mask element. A 2-inch wide sample was cut for each combination of laminated article and exposed article for peel testing, using a The relief-forming precursor was adhered to a stainless steel plate using a double-sided clear tape E1120H. The peel force (in grams) was measured using an IMASS adhesion tester SP-2100 (available from Imass, Inc., Hingham, Mass.) equipped with a 5 kg load, a 180° peel angle, and a 12 in / min peel rate. The measurements were averaged over the 5-second and 1-second delays.

[0181] Formation of flexographic printing plates with relief images

[0182] After removing the cover film from the relief-forming layer of the relief-forming precursor, followed by lamination and UV curing of the mask as described above, the mask is removed from the photosensitive layer manually or by a mechanical process. The relief image precursor having a relief image in the relief-forming layer is then treated with a solvent or aqueous plate treatment agent, depending on the nature of the photopolymer plate precursor, dried, and finished (UV post-exposure) to obtain a relief printing plate.

[0183] Surface energy measurement:

[0184] To derive the surface energy value of the relief flexographic printing plate, contact angles were first measured using polar (water) and dispersant (diiodomethane) droplets.

[0185] The surface energy components of each liquid used are:

[0186] water:

[0187] Diiodomethane:

[0188] in:

[0189]

[0190]

[0191]

[0192] To calculate the surface energy, the Fowkes model and the Owens-Wendt-Rabel & Kaelble model were used.

[0193]

[0194] Equation 1: Fowkes equation relating liquid and solid components to contact angle.

[0195] in:

[0196]

[0197]

[0198] θ = contact angle.

[0199]

[0200] Equation 2: Owens-Wendt-Rabel & Kaelble model.

[0201] Surface Energy and Peel Force Overview

[0202] The peel force for peeling a masking element from an imaged relief-forming layer of a relief-forming precursor was measured as described herein. Additionally, the relief-forming layer was developed into a relief image layer of a relief printing plate and the surface energy of the relief image layer was measured as described herein.

[0203] The examples of the present invention are compared with the comparative examples shown in Table 1.

[0204] When the masking element is removed from the imaged relief-forming layer of the relief-forming precursor, there is a significant reduction in peel force. In addition, the layer of the relief image with the low surface energy additive of the relief printing plate achieves a lower surface energy compared to the higher surface energy of the relief image layer without the low surface energy additive.

[0205] As is apparent from Table 1, for solvent-washable relief-forming precursors, Inventive Example 1, which contains a low surface energy monomer, exhibits a 30% reduction in the force required to peel a mask TIL-R (e.g., the mask described in U.S. Patent No. 8,945,813 (Kidnie)) from a plate compared to Comparative Example 1. The peel force was also reduced by 65% when using the mask described in U.S. Patent No. 2019 / 0258154 (Kidnie) compared to Comparative Example 1. This significant reduction in peel force allows the imaged mask to be easily peeled and removed from the plate, which can be accomplished using a simple mechanical device to automatically remove the mask from the relief-forming layer.

[0206] Furthermore, Table 1 shows that the peel force of Inventive Example 2 (a water-washable UltraNX plate containing a low surface energy monomer) is reduced by 52% compared to Comparative Example 2, making it easier to peel the mask from the water-washable relief-forming layer of the flexographic plate precursor, which helps prevent accidental damage to the mask or the relief-forming layer of the relief flexographic printing plate during separation.

[0207]

[0208] It should be noted that different types of panels can have different surface energies with the addition of a low-surface-energy additive. That is, the type of matrix material of the relief-forming layer can provide a basis for the surface energy, and the addition of a low-surface-energy additive can significantly reduce this surface energy. Thus, the reduced surface energy is relative to the same type of material without the low-surface-energy silicone acrylate additive. Thus, when a low-surface-energy additive is included, as in Inventive Example 2, materials such as Comparative Example 2 have an even further reduced surface energy.

[0209] In light of the foregoing, low-surface-energy additives can reduce the release force of UV-curable relief-forming materials for various types of matrix materials. This allows for the use of a certain type of polymerizable monomer for the matrix, and then the addition of a low-surface-energy additive to reduce the release force of that specific monomer type. It should be understood that different types of monomers and resulting polymers may exhibit different release forces in the absence of a low-surface-energy additive, and that the addition of a low-surface-energy additive reduces the release force of each of the different types of monomers and resulting polymers. Accordingly, one type of polymer may have a higher surface energy than another; however, the low-surface-energy additive can reduce the surface energy of these polymers in the resulting relief image layer. Thus, the low-surface-energy additive reduces the release force required to release the mask from the UV-sensing layer and reduces the surface energy of the resulting relief image layer, compared to a composition without the low-surface-energy additive.

[0210] In some embodiments, for any type of mask, the peel force may be less than about 73.41 g / in. For solvent-washable plate precursors, the peel force may be less than about 70 g / in, more preferably less than about 60 g / in, even more preferably less than about 55 g / in, and even more preferably less than about 50 g / in. For water-washable plate precursors, the peel force may be less than about 30 g / in, more preferably less than about 25 g / in, more preferably less than about 20 g / in, and even more preferably less than about 15 g / in.

[0211] In some embodiments, the surface energy of the solvent-washable relief image layer may be less than about 60 mj / m2, more preferably less than about 58 mj / m2, less than about 57 mj / m2, or less than or about 56 mj / m2. Additionally, the surface energy of the water-washable relief image layer may be less than about 46 mj / m2, more preferably less than about 45 mj / m2, less than about 44 mj / m2, or less than or about 43 mj / m2.

[0212] definition

[0213] As used herein to define the various components of non-ablative light-to-heat conversion (LTHC) layers, non-silver halide thermally ablatable imaging layers (ILs), and other materials, layers, and compositions (e.g., developers or processing solutions) used in the practice of the invention, the singular forms "a," "an," and "the" are intended to include one or more components (i.e., include plural referents) unless otherwise indicated.

[0214] Each term not expressly defined in this application should be understood to have a meaning generally accepted by those skilled in the art. If a term is constructed in such a way that it loses its meaning or substantially loses its meaning in the context, the term should be interpreted as having its standard dictionary meaning.

[0215] Unless expressly stated otherwise, the use of numerical values within the various ranges specified herein is to be considered approximate, as if both the minimum and maximum values within the stated ranges were preceded by the word "about." In this manner, slight variations above and below the stated ranges may contribute to achieving substantially the same results as the values within the ranges. Furthermore, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values and the endpoints of the ranges.

[0216] The non-ablatable light-to-heat conversion layer is also identified herein as an LTHC layer.

[0217] The non-silver halide thermally ablatable imaging layer is also identified herein as an IL.

[0218] Unless otherwise indicated herein, the term "imageable material" is used to refer to embodiment articles prepared and used in accordance with the present invention. Such imageable materials may also be referred to as "mask films," "mask precursors," or "mask elements." Imageable materials can be converted by appropriate thermal (IR) imaging into "mask elements" that contain a mask image that can be used to form relief images in accordance with the present invention.

[0219] Unless otherwise stated, percentages are by weight.

[0220] As used herein, the term "relief-forming precursor" refers to any imageable element or material that can produce a relief image when exposed to light through a mask element. Examples of such relief-forming precursors are described in detail below, but some examples include flexographic printing plate precursors, relief printing plate precursors, and printed circuit boards. Detailed information on useful relief-forming materials is described in U.S. Patent Application Publication No. 2005 / 0227182 (noted above), the disclosure of which is incorporated herein by reference. In this disclosure, relief-forming precursors are generally identified as "radiation-sensitive / inductive elements."

[0221] Unless otherwise specified, the term "ablative" or "ablation" refers to thermal imaging performed by a laser that causes rapid localized changes in a non-silver halide heat-ablatable imaging layer (IL) of an imageable material, resulting in the ejection of material from the IL. This is in contrast to other material transfer or imaging techniques such as melting, evaporation, or sublimation.

[0222] The terms "optical contact" and "perfect optical contact" have the same meaning and refer to two layers or two elements (such as in the case of a mask element and a relief-forming precursor) that share an interface and are in intimate physical contact such that there are substantially no air gaps or voids between the contacting surfaces, thereby providing an "airless interface." More precisely, two surfaces are defined as being in optical contact when the reflective and transmissive properties of their interface are substantially fully described by Fresnel's laws for reflection and transmission of light at a refractive index boundary.

[0223] As used herein, unless otherwise indicated, the term "transparent" refers to the ability of a material or layer to transmit at least 95% of impinging (or incident) electromagnetic radiation, such as electromagnetic radiation having a wavelength of at least 200 nm to 750 nm (i.e., commonly referred to in the art as UV and visible radiation). The transparent polymer support sheet and LTHC layer described below particularly possess this property.

[0224] The "average dry thickness" of a given dry layer is typically the average of 10 different measurements taken from cross-sectional images of the dry layer.

[0225] Those skilled in the art will understand that for the processes and methods disclosed herein, the functions performed in the processes and methods may be implemented in a different order. Furthermore, the steps and operations outlined are provided as examples only, and certain steps and operations may be optional, may be combined into fewer steps and operations, or may be expanded into other steps and operations without departing from the essence of the disclosed embodiments.

[0226] The present disclosure is not limited to the aspects of the specific embodiments described in this application, which are intended to serve as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope, which will be apparent to those skilled in the art. In addition to those enumerated herein, functionally equivalent methods and devices within the scope of the present disclosure will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is only limited by the terms of the appended claims and the full scope of equivalents granted by these claims. It should be understood that the present disclosure is not limited to specific methods, reagents, compound compositions or biological systems, which can of course vary. It should also be understood that the terms used herein are only used to describe the purpose of specific embodiments and are not intended to be limiting.

[0227] With respect to the use of substantially any plural and / or singular terms herein, those skilled in the art can convert the plural to the singular and / or the singular to the plural as appropriate to the context and / or application. For clarity, the various singular / plural permutations may be expressly stated herein.

[0228] Those skilled in the art will understand that, in general, the terms used herein, and particularly in the appended claims (e.g., the bodies of the appended claims), are generally intended to be “open-ended” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “comprising” should be interpreted as “including but not limited to,” etc.). Those skilled in the art will further understand that if a specific number of an introduced claim recitation is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, to aid understanding, the following appended claims may contain the use of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that a claim recitation introduced by the indefinite article “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and an indefinite article, such as “a” or “an” (e.g., “a” and / or “an” should be interpreted to mean “at least one” or “one or more”); the same is true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of introduced claim recitations is explicitly recited, one skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). Furthermore, such construction is generally used in those instances where a convention is similar to "at least one of A, B, and C, etc.", with the intention that one skilled in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include, but is not limited to, systems having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). Such construction is generally used in those instances where a convention is similar to "at least one of A, B, or C, etc.", with the intention that one skilled in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include, but is not limited to, systems having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). Those skilled in the art will further understand that, in practice, any disjunctive word and / or phrase presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to include the possibility of including one of the terms, either one of the two terms, or both terms. For example, the phrase "A or B" will be understood to include the possibility of "A" or "B" or "A and B."

[0229] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subcombination of members of the Markush group.

[0230] As will be understood by those skilled in the art, for any and all purposes, such as for providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily identified as fully described, and the same range can be broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be easily broken down into a lower third, a middle third, and an upper third. As will be understood by those skilled in the art, all language, such as "up to," "at least," etc., includes the enumerated numbers and refers to a range that can subsequently be broken down into the subranges discussed above. Finally, as will be understood by those skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to a group having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to a group having 1, 2, 3, 4, or 5 cells, etc.

[0231] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for illustrative purposes and that various modifications may be made without departing from the scope and spirit of the present disclosure. Therefore, the various embodiments disclosed herein are not intended to be limiting, with the true scope and inventive concept being indicated by the appended claims.

[0232] All references cited herein are incorporated by specific reference in their entirety.

Claims

1. A relief-forming precursor comprising: substrate; and a relief-forming layer having a bottom surface facing the substrate and a relief-forming surface facing away from the substrate, wherein the relief-forming layer is uncured and the relief-forming surface is adapted to receive a mask; The relief-forming layer comprises: polymer; at least one photopolymerizable monomer; a photopolymerization initiator that is sensitive to UV radiation; and Photopolymerizable low surface energy monomer.

2. The relief-forming precursor of claim 1, wherein the photopolymerizable low surface energy monomer has a siloxane moiety attached to at least one polymerizable functional group.

3. The relief-forming precursor of claim 2, wherein the at least one polymerizable functional group comprises at least one acrylate moiety.

4. The relief-forming precursor of claim 3, wherein the at least one acrylate moiety comprises acrylate or methacrylate.

5. The relief-forming precursor of claim 2, wherein the photopolymerizable low surface energy monomer further comprises a plurality of polymerizable functional groups attached to the siloxane moiety.

6. The relief-forming precursor according to claim 1, which consists of the following in order: substrate; an optional metal layer on the substrate; a single layer of said relief-forming layer on said substrate or metal layer; and Optional cover sheet on the relief-forming layer.

7. A relief forming assembly comprising: The relief-forming precursor according to claim 1; and A mask element having an imaged layer having a mask image, the mask element being in full optical contact with the relief-forming surface of the relief-forming layer.

8. The relief-forming assembly of claim 7, wherein the photopolymerizable low surface energy monomer has a siloxane moiety attached to at least one polymerizable functional group.

9. The relief-forming assembly of claim 8, wherein the at least one polymerizable functional group comprises at least one acrylate moiety.

10. The relief-forming assembly of claim 9, wherein the at least one acrylate portion comprises acrylate or methacrylate.

11. The relief-forming assembly of claim 7, further comprising an adhesive layer on the substrate opposite the relief-forming layer.

12. The relief-forming assembly of claim 11, further comprising an antihalation material in the adhesive layer.

13. The relief forming assembly according to claim 7, which is composed of the following in order: substrate; an optional metal layer on the substrate; a single layer of said relief-forming layer on said substrate or metal layer; and Mask element.

14. A method of manufacturing the relief-forming component of claim 7, comprising: placing the imaged layer of the mask element on the relief-forming surface of the relief-forming layer; and Complete optical contact is formed between the mask element and the relief-forming surface.

15. The method of claim 14, further comprising at least one of the following: laminating the masking element to the relief-forming surface; or The mask element is coupled to the relief-forming surface by vacuum drawing.

16. A method of producing a relief image in a relief forming assembly, the method comprising: Providing a relief forming assembly according to claim 7; exposing the relief-forming layer to curing UV radiation through a mask element to form an imaged relief-forming layer having UV-exposed regions forming polymerized regions and unexposed regions forming non-polymerized regions; removing the masking element from the imaged relief-forming layer; as well as The imaged relief-forming layer is developed by removing the non-polymerized areas in the imaged relief-forming layer to form a relief image element having a relief image.

17. The method of claim 16, further comprising polymerizing at least one photopolymerizable monomer and a photopolymerizable low surface energy monomer with a photopolymerization initiator such that a low surface energy portion exists at the relief surface of the relief image of the relief image element.

18. The method of claim 17, further comprising polymerizing the plurality of polymerizable functional groups of the photopolymerizable low surface energy monomer with the at least one photopolymerizable monomer to form a cross-linked polymeric relief image element.

19. The method of claim 17, wherein the photopolymerizable low surface energy monomer has a siloxane moiety attached to at least one polymerizable functional group.

20. The method of claim 19, wherein the at least one polymerizable functional group comprises at least one acrylate moiety.

21. A relief image element comprising: substrate; A relief image layer having an elastomer and a copolymer, wherein the copolymer includes at least one photopolymerizable monomer and a photopolymerizable, low surface energy monomer having a siloxane moiety, wherein the relief image layer has a relief surface having peaks and valleys of a relief image, wherein a portion of the siloxane moiety is present at the relief surface.

22. The relief image element of claim 21 wherein the copolymer comprises crosslinks of a photopolymerizable monomer and a photopolymerizable low surface energy monomer.

Images