Oxygen barrier layer, preparation method of oxygen barrier layer and flexible resin plate with textured flat-top lattice points on surface

Abstract

The invention provides an oxygen barrier layer, a preparation method of the oxygen barrier layer and a flexible resin plate with textured flat-top lattice points on the surface, polymer particles are formed by in-situ polymerization of polyurethane resin containing free isocyanate monomers and oxygen barrier resin containing hydroxyl in an organic solvent, and solid filler does not need to be additionally added; the molar content of hydroxyl in the oxygen inhibitor resin is greater than the molar content of isocyanate in the isocyanate monomer, so that the oxygen inhibitor is excessive, and the oxygen inhibitor resin, the polyurethane resin and the flatting agent which do not participate in the reaction jointly participate in film formation. Raw materials of the oxygen barrier layer can be dissolved in a mainstream commercially available flexographic flushing medium, such as an organic solvent containing tetrachloroethylene / n-butyl alcohol or a high-end environment-friendly developing solution containing terpene or commercially available Shanghai sensitive morning, and a photopolymerization reaction does not occur. After exposure, laser ablation and plate washing by a flexible plate washing medium, the flexible resin plate with the flat-top lattice points with the sand meshes on the surface is prepared, and the oxygen barrier layer is completely removed without residues in the plate washing process.

Description

Technical Field

[0001] This invention relates to flexible resin plates, and more particularly to an oxygen barrier layer, a method for preparing it, and a flexible resin plate with flat-top dots that have a textured surface. Background Technology

[0002] Currently, flexible resin plates are widely used in printing on easily deformable or soft substrates such as cartons, flexible packaging, and labels.

[0003] Typically, a film with patterns or text is placed on an unexposed flexographic plate containing a photosensitive elastomer and exposed to ultraviolet light. The transparent areas of the film allow ultraviolet light to pass through, causing the initiator in the photosensitive elastomer to decompose and generate free radicals, which in turn initiate the polymerization reaction of crosslinkable monomers and cure the elastomer. The areas that do not transmit ultraviolet light do not undergo crosslinking. Utilizing the difference in solubility of these two types of film in the developer, an embossed image with text or patterns is obtained after washing and development. The developed plate undergoes drying, de-adhesion, and post-exposure treatments to ensure complete polymerization of the photosensitive layer. The resulting plate is then fixed onto the cylinders of a flexographic printing press and is ready for printing.

[0004] The aforementioned plate-making process requires the use of film with patterns or text. This film is susceptible to defects caused by external conditions such as washing, dust, and moisture, which in turn affects the reproduction effect of text and patterns on the flexible resin plate. At the same time, when the film is attached to the flexographic plate's anti-stick layer for plate-making, film adhesion is likely to occur, and plate-making defects such as light refraction and scattering are likely to occur, resulting in a decrease in the reproduction quality of patterns or text.

[0005] With the development of computer technology and prepress document processing technology, document information containing patterns or text can be converted into digital information. Using computer control, this digital information is converted into infrared lasers, violet lasers, etc., and output to the ablation black film of a flexographic plate, achieving laser ablation imaging. This eliminates the need for film imaging, thus removing the problem of reduced image quality caused by using film plates. This type of plate is called a digital flexographic resin plate.

[0006] The conventional digital flexographic printing process involves: after removing the protective film, ablation imaging of the black film is performed using a laser; then, the photosensitive elastomer is exposed using UV-A or UV-LED; finally, the plate is prepared by rinsing with developer, drying, and post-processing. Because the exposure process takes place in air, the oxygen in the air inhibits the exposure of the photosensitive elastomer's surface, causing the dots reproduced on the plate to be bullet-shaped. These bullet-shaped dots have less support during printing and greater friction with the anilox roller walls, resulting in lower printing durability. Furthermore, the printing effect of the highlights is not clear enough, failing to meet the requirements of 150 lpi high-definition flexographic printing.

[0007] Studies have shown that to achieve high-definition flexographic printing, flat-top dots are required, and the surface of the photosensitive elastomer layer must have its own texture to improve ink transfer efficiency and increase the printing plate durability.

[0008] To achieve a textured surface and flat-topped dots on the flexible resin plate, researchers explored a variety of technical solutions.

[0009] The first approach involves filling the photomask of the exposure machine with nitrogen gas, supplied by an external nitrogen generator or a nitrogen cylinder. Once the nitrogen concentration reaches a set value, a standard plate is exposed to form flat-top dots. Patent US2009 / 0186308A1 specifies that the oxygen concentration inside the exposure machine should ideally be controlled between 100-190 ppm. This approach requires additional nitrogen generator equipment, which is relatively bulky, and it is difficult to maintain a constant nitrogen concentration during each plate-making process. Therefore, it is not an ideal method for forming flat-top dots.

[0010] The second approach is lamination. After laser engraving the ablation black film on a conventional printing plate, a thin film is applied to isolate it from oxygen in the air, followed by front-side exposure to create flat-top dots. US Patent US2017 / 0297358A1 optimizes the exposure parameters after lamination to achieve flat-top dots, and this dot reproduction effect is suitable for corrugated cardboard printing. This approach adds an extra step, making it cumbersome for plate makers. Furthermore, dust or air bubbles entering during the lamination process can easily lead to plate failure.

[0011] The third method involves immersing the laser-engraved black film on a plate in water for exposure, thus isolating it from oxygen in the air and forming flat-topped dots, as disclosed in patent CN107521214A. This method is more complicated to operate.

[0012] The fourth approach involves placing an oxygen barrier layer between the laser-ablated black film and the photosensitive elastomer, as disclosed in patent US8492074B2. This plate has a five-layer structure (A), (B), (C), (D), and (E), with an oxygen barrier layer (C) placed between layers (B) and (D). The oxygen barrier layer (C) uses two different resins, such as polyvinylpyrrolidone, lacquer, polyvinyl butyral, polyvinylidene chloride, or vinyl chloride polymers. This oxygen barrier layer can form flat-topped dots, but it cannot create textures on the plate surface.

[0013] CN107969149A discloses an oxygen barrier layer and a self-flat-top dot digitizing flexible resin plate with a sandblasted surface containing the layer's raised portion. The oxygen barrier layer comprises: 50-99% by weight of polyvinyl acetate or polyvinyl acetal with a molar degree of hydrolysis of 10-75%; 1-30% by weight of an alkaline polymer (such as polyethyleneimine); and 0-50% by weight of filler (SiO2 or silicate). This patent produces a flat-top dot plate with a self-textured surface by pressing the oxygen barrier layer and its internal SiO2 or silicate particles onto the surface of the flexible resin plate. The oxygen barrier layer contains SiO2 or silicate with an average particle size of 2-6 micrometers, requiring additional dispersion of solid particles in the coating solution.

[0014] The oxygen barrier layer disclosed in CN105745578A contains polyvinyl alcohol and polyvinyl alcohol derivatives that are poorly soluble in organic solvents, and requires two separate processes: water washing and solvent washing, which is incompatible with the single-process cleaning process of existing commercially available plate washing machines. Summary of the Invention

[0015] To address the limitations of flexographic printing plates in terms of adaptability to plate-making conditions and dot structure performance, this invention provides an oxygen barrier layer, its preparation method, and a flexographic printing plate with flat-top dots featuring a self-textured surface. The particles in the oxygen barrier layer are polymer particles, formed by in-situ polymerization of polyurethane resin containing free isocyanate monomers and oxygen barrier resin with hydroxyl groups in the molecule in an organic solvent, without the need for additional solid fillers. The oxygen barrier layer provided in this application can form a frosted texture and flat dots on the plate surface, improving the ink transfer capability and printing durability of the plate. The raw materials of the oxygen barrier layer provided in this application are compatible with current mainstream plate-making conditions, soluble in mainstream commercially available flexographic washing media, such as organic solvents containing tetrachloroethylene / n-butanol or containing terpenes or commercially available high-end environmentally friendly developer from Shanghai Minchen, and do not undergo photopolymerization. After exposure, laser ablation, and washing with flexographic washing media, a flat-top dotted flexographic printing plate with a self-textured surface is obtained, and the oxygen barrier layer is completely removed without residue during the washing process.

[0016] The object of the present invention is achieved in the following manner: an oxygen barrier layer containing particles with a diameter of 0.1-10 μm, the oxygen barrier layer being formed by coating and drying an oxygen barrier layer coating liquid, the raw materials of the oxygen barrier layer coating liquid including an organic solvent, a leveling agent, a polyurethane resin containing free isocyanate monomers and an oxygen barrier resin containing hydroxyl groups, wherein the molar content of hydroxyl groups in the oxygen barrier resin is greater than the molar content of isocyanate groups in the isocyanate monomers, and a portion of the oxygen barrier resin containing hydroxyl groups reacts with the isocyanate monomers in the polyurethane resin in an organic solvent to generate polymer particles with a diameter of 0.1-10 μm.

[0017] The oxygen permeability of hydroxyl-containing oxygen barrier resins is less than or equal to 500 (cm³×100μm) / (m²×d×bar).

[0018] The oxygen barrier resin is at least one of ethyl cellulose, polyvinyl acetate with a molar degree of hydrolysis of 30-70%, polyvinyl alcohol acetal with a molar degree of hydrolysis of 30-70%, alkyl cellulose, cellulose acetate butyrate, and chitosan.

[0019] The oxygen barrier resin is ethyl cellulose with a degree of substitution of 2.3-2.6.

[0020] Based on the dry weight of the oxygen barrier layer, its components and weight percentages are as follows: 50%-70% oxygen barrier resin containing hydroxyl groups, 20%-45% polyurethane adhesive resin containing free isocyanate monomers, and 5%-10% leveling agent.

[0021] The organic solvent is at least one of n-butanol, ethyl acetate, methanol, ethanol, propylene glycol methyl ether, or butanone, and the boiling point of the organic solvent is below 120°C.

[0022] Polyurethane resins containing free isocyanate monomers have a molecular weight of 1,000-10,000, and the content of free isocyanate monomers is 10%-30%.

[0023] The preparation method of the oxygen barrier coating liquid is as follows: Dissolve the hydroxyl-containing oxygen barrier resin in an organic solvent, add the polyurethane resin containing free isocyanate monomer under stirring conditions of 300-400 r / min, and after the addition is completed within 15 min, stir at high speed of 900-1100 r / min for 2.9-3.1 h to form a suspension, then add the leveling agent and stir to mix evenly to obtain the oxygen barrier coating liquid.

[0024] A flat-top dotted flexible resin plate with a naturally frosted textured surface comprises, from bottom to top, a support, a photosensitive elastomer layer, an oxygen barrier layer, and a laser-ablable mask layer, wherein the oxygen barrier layer is the aforementioned oxygen barrier layer.

[0025] The thickness of the photosensitive elastomer layer is 0.1-7 mm, the thickness of the oxygen barrier layer is 0.5-5 μm, and the thickness of the laser ablation mask layer is 0.5-5 μm.

[0026] Compared to existing technologies, this invention provides an oxygen barrier layer, its preparation method, and a flexible resin plate with a flat-top dot surface possessing its own texture. The polymer particles are formed by in-situ polymerization of polyurethane resin containing free isocyanate monomers and oxygen barrier resin containing hydroxyl groups in an organic solvent, without the need for additional solid fillers. Because the molar content of hydroxyl groups in the oxygen barrier resin is greater than the molar content of isocyanate groups in the isocyanate monomers, the oxygen barrier is in excess, and the unreacted oxygen barrier resin, polyurethane resin, and leveling agent all participate in film formation. The raw materials for the oxygen barrier layer are soluble in mainstream commercially available flexographic printing media, such as organic solvents containing tetrachloroethylene / n-butanol, or those containing terpenes, or commercially available high-end environmentally friendly developers like Shanghai Minchen, without undergoing photopolymerization. After exposure, laser ablation, and flexographic printing media washing, a flexible resin plate with a flat-top dot surface possessing its own texture is obtained, and the oxygen barrier layer is completely removed without residue during the washing process.

[0027] An oxygen barrier coating solution is applied to a laser-ablated black film and then laminated onto a photosensitive elastomer after drying. During the plate-making process, the particle shape is printed onto the surface of the flexographic plate, thereby increasing the roughness of the raised parts of the plate and improving the ability of the plate to transfer ink during printing.

[0028] Furthermore, using the oxygen barrier layer of this technology, there are no cracks on the large solid and halftone dots of the flexible resin plate. The solid areas of the plate have a frosted texture, which has a higher ink transfer capability, resulting in a thicker ink layer and more realistic color reproduction.

[0029] Following conventional flexographic plate-making procedures, the resulting printing plate exhibits flat-topped halftone dots, and the photosensitive elastomer surface of the plate material develops a frosted texture, resulting in increased ink transfer during printing. The flexographic printing plate of this invention features a photosensitive elastomer with its own frosted texture, and a simple and reliable processing method during plate formation, resulting in higher dot reproduction quality and greater tonal gradation in the printed matter. Attached Figure Description

[0030] Figure 1 These are the three-dimensional and outline views of the flexible resin plate with 5% dots at 150 lpi obtained in Example 1. Figure 1 The top right is a top-down view of a 5% dot matrix at 150 lpi. Figure 1 Side 3D view of top left 5% dot @ 150 lpi Figure 1 Below is the outline of 5% of the dots at 150 lpi.

[0031] Figure 2 These are the three-dimensional and outline views of the flexible resin plate with 5% dots at 150 lpi obtained in Example 2. Figure 2 The top right is a top-down view of a 5% dot matrix at 150 lpi. Figure 2 Side 3D view of top left 5% dot @ 150 lpi Figure 2Below is the outline of 5% of the dots at 150 lpi.

[0032] Figure 3 These are the 3D image and outline of the flexible resin plate with 5% halftone dots at 150 lpi obtained in Comparative Example 1. Figure 3 The top right is a top-down view of a 5% dot matrix at 150 lpi. Figure 3 Side 3D view of top left 5% dot @ 150 lpi Figure 3 Below is the outline of 5% of the dots at 150 lpi.

[0033] Figure 4 These are the 3D image and outline of the flexible resin plate with 5% halftone dots at 150 lpi obtained in Comparative Example 2. Figure 4 The top right is a top-down view of a 5% dot matrix at 150 lpi. Figure 4 Side 3D view of top left 5% dot @ 150 lpi Figure 4 Below is the outline of 5% of the dots at 150 lpi.

[0034] Figure 5 These are the 3D image and outline of the flexible resin plate with 5% halftone dots at 150 lpi obtained in Comparative Example 3. Figure 5 The top right is a top-down view of a 5% dot matrix at 150 lpi. Figure 5 Side 3D view of top left 5% dot @ 150 lpi Figure 5 Below is the outline of 5% of the dots at 150 lpi.

[0035] Figure 6 This is a photograph of the solid material of the printing plate with a frosted texture in Example 1, taken under a 500x microscope. The black granular or striped shapes in the image are the frosted texture on the solid material of the printing plate. Because they are pits, they appear black under the microscope.

[0036] Figure 7 This is a photograph of the solid material of Comparative Example 1 without a matte texture, taken under a 500x microscope.

[0037] Figure 8 This is a photograph of the solid material residue in control example 4 under a 500x microscope. Detailed Implementation

[0038] A flexible resin plate with a flat-topped dot pattern on its surface has a textured surface. From bottom to top, it comprises the following structural layers: a support (A), a photosensitive elastomer layer (B), an oxygen barrier layer with particles (C), a laser-ablable mask layer (D), and a removable protective film (E).

[0039] The following is a detailed description of each structural layer: Support (A) The flexible resin plate includes a dimensionally stable support (A), preferably made of a dimensionally stable material with a thickness of 50-300 μm, the material being selected from steel, aluminum, alloys, or plastics, wherein the plastic material is, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or polycarbonate. More preferably, it is a PET film with a thickness of 100-200 μm; in specific applications, for plates with a thickness of 1.14 mm or less, a PET film with a thickness of 175 μm is preferred; for flexible plates of other thicknesses, a PET film with a thickness of 125 μm is preferred.

[0040] The dimensionally stable support (A) may be selected from conventional surface adhesion treatments, such as corona treatment, chemical etching treatment, or physical bonding treatment.

[0041] Photosensitive elastomer layer (B) The flexible resin plate includes at least a photosensitive elastomer layer (B). Other functional layers, such as an adhesive layer or an elastic reinforcing layer, may be provided between the support (A) and the photosensitive elastomer layer (B). The photopolymerizable photosensitive elastomer layer (B) is preferably a photopolymerizable photosensitive elastomer layer.

[0042] The photopolymerizable photosensitive elastomer layer (B) has a conventional structure, which includes at least an elastomer binder, an olefinic unsaturated compound, a photoinitiator or a photoinitiator system, and may also include one or more auxiliary components, such as plasticizers, dyes, UV absorbers, etc.

[0043] Elastomer adhesive: selected from materials known to those skilled in the art, such as styrene-diene block copolymers, natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, nitrile rubber, butyl rubber, styrene-isoprene rubber, styrene-butadiene-isoprene rubber, polynorbornene rubber, or ethylene-propylene-diene rubber; preferably an elastomeric adhesive soluble in nonpolar hydrocarbon solvents and moderately polar alcohols. More preferably, it is a thermoplastic elastomeric block copolymer comprising an alkenyl aromatic compound and 1,3-diene, specifically an A-B-A type triblock copolymer, (AB)n type radial block copolymer (where A is a styrene unit and B is a diene unit), or a statistical copolymer or random copolymer of styrene and diene.

[0044] Component content: Based on the total weight of the photosensitive elastomer layer (B), the content of the elastomer adhesive is preferably 45-75 wt%; the content of the olefin unsaturated polymerizable monomer is preferably 3-15 wt%; the content of the photoinitiator or photoinitiator system is preferably 3-6 wt%; and the content of the plasticizer (optionally self-modified or unmodified natural oil or natural resin) is preferably 0-40 wt%.

[0045] Optional components: The photosensitive elastomer layer (B) may also contain surfactants, such as hydrophobic waxes, silicon-containing compounds, or perfluorinated compounds, as disclosed in U.S. Patent US8114566. These surfactants can migrate from the interior of the photosensitive elastomer layer (B) to the surface during the drying process of the flexographic printing plate, generating repulsion with the printing ink, thereby reducing the accumulation of fine dots during printing and decreasing the frequency of plate cleaning.

[0046] The thickness of the photosensitive elastomer layer (B) is typically 0.1-7 mm, preferably 0.5-4 mm, and more preferably 0.7-2.5 mm.

[0047] Oxygen barrier layer with particles (C) An oxygen barrier layer is positioned between the photosensitive elastomer layer and the laser-ablable mask layer (D) used for image formation. The laser-ablable mask layer is a laser-ablable mask / laser-ablable black film. The oxygen barrier layer bonds the photosensitive elastomer layer and the laser-ablable mask layer together. When the protective film (E) is removed, the laser-ablable mask / laser-ablable black film can detach perfectly from the protective film and completely cover the surface of the photosensitive elastomer. Simultaneously, during laser ablation imaging of the laser-ablable mask / laser-ablable black film, laser ablation does not damage the oxygen barrier layer; after the black film is ablated, the oxygen barrier layer remains intact on the photosensitive elastomer.

[0048] The oxygen barrier layer contains particles with a diameter of 0.1-10 μm. These particles are formed by the polymerization of polyurethane resin containing free isocyanate monomers (-N=C=O) and oxygen barrier resin containing hydroxyl groups (-OH) in an organic solvent. Unreacted oxygen barrier agents, polyurethane resins, and leveling agents all participate in film formation.

[0049] When the oxygen barrier layer is coated onto the laser-ablated black film layer and laminated with the photosensitive elastomer layer, the sand-like structure formed by the polymer particles in the oxygen barrier layer is pressed onto the soft surface of the photosensitive elastomer, thereby forming a texture on the surface of the photosensitive elastomer to improve the ink transfer performance of the flexographic resin plate. The oxygen barrier layer set in this invention can reduce the influence of oxygen on the polymerization reaction of the photosensitive elastomer, thus forming flat-top dots; the raw materials used in the oxygen barrier layer are all soluble in mainstream commercially available flexographic plate washing media, such as organic solvents containing tetrachloroethylene / n-butanol or those containing terpenes or commercially available high-end environmentally friendly developers from Shanghai Minchen, etc., and will not undergo photopolymerization reaction, avoiding residues in subsequent plate-making processes.

[0050] The oxygen permeability of oxygen barrier resins with oxygen barrier effect is usually less than 1000, preferably not more than 500 (cm³×100μm) / (m²×d×bar).

[0051] For the oxygen barrier layer (C), in principle, any oxygen barrier agent with an oxygen permeability not exceeding the above-mentioned upper limit can be used, but it must simultaneously meet the following essential technical conditions: it must carry hydroxyl groups in its molecular structure, be transparent to UVA light (wavelength 300-400nm), and be soluble or dispersed in commercially available flexographic washing media. Therefore, the hydroxyl-containing oxygen barrier resin is one or more of ethyl cellulose, polyvinyl acetate with a molar degree of hydrolysis of 30-70%, polyvinyl alcohol acetal with a molar degree of hydrolysis of 30-70%, alkyl cellulose, or chitosan. If the degree of hydrolysis of polyvinyl acetate is too low, its oxygen barrier performance is poor; if it is too high, its solubility in commercially available washing solutions is low. Both excessively high and low levels are detrimental to its use, and the same applies to polyvinyl alcohol acetal.

[0052] The substitution value of ethyl cellulose is related to its solubility. To facilitate coating operations, ethyl cellulose with a substitution value in the range of 2.3-2.6 is selected. Although its oxygen barrier properties are sufficient to meet the requirements, pure ethyl cellulose is difficult to achieve good adhesion between the laser ablation black film and the photosensitive elastomer, and it cannot form a sand-like texture.

[0053] To create a sandy texture (fine pits) in the halftone and solid areas, thereby improving the ink transfer capability of the printing plate, a polyurethane resin containing free isocyanate monomers needs to be added. This polyurethane resin contains free isocyanate monomers, which can react with hydroxyl-containing oxygen barrier resins to form polymer particles.

[0054] The molecular weight of polyurethane resin is positively correlated with its tensile strength; increasing the molecular weight can improve the bonding effect. However, excessively high molecular weight will lead to higher resin viscosity, increasing the difficulty of stirring and coating processes. At the same time, excessive cohesion reduces the wettability of the substrate, easily causing damage to the bonding interface. Therefore, the molecular weight of polyurethane resin containing free isocyanate monomers is preferably 1000-10000, more preferably 1000-3000.

[0055] Polyurethane resins containing free isocyanate monomers are also used as adhesives. Increasing the isocyanate monomer content can enhance the hardness and tensile strength of the adhesive, and at the same time, it can react with hydroxyl-containing oxygen-barrier components to generate a higher concentration suspension, thereby introducing more grit during the plate-making process. However, excessively high isocyanate content can lead to decreased elasticity and increased brittleness of the oxygen-barrier layer, and may cause the particle size of the polymer generated by the reaction to exceed the acceptable range (0.1-10 μm). Therefore, the preferred isocyanate monomer content is 10%-30%.

[0056] In this invention, the organic solvent should meet the following conditions: 1. It should have good solubility for the above-mentioned oxygen inhibitors and binders; 2. It should have a baking temperature with a boiling point below 120°C. Examples of organic solvents that meet the above requirements include: one of n-butanol, ethyl acetate, methanol, ethanol, propylene glycol methyl ether, and butanone, or a mixture of the above substances.

[0057] The solvent is eventually evaporated at high temperature when it is coated onto the photoreceptor to form an oxygen barrier layer.

[0058] Leveling agents are commonly used in oxygen barrier layers to adjust the tension for easier coating.

[0059] The preparation method of the oxygen barrier coating solution is as follows: Dissolve the hydroxyl-containing oxygen barrier resin in an organic solvent, and slowly add a polyurethane binder containing free isocyanate monomers while stirring. At this time, fine particles can be observed to precipitate. Continue stirring until a suspension is formed. Finally, add a leveling agent and stir to obtain the oxygen barrier coating solution.

[0060] The particle diameter in the oxygen barrier layer can be precisely controlled by adjusting the pore size of the filter cartridge, the concentration of reactants, the feeding rate of the reaction components, and the stirring speed, ultimately achieved through filtration of the oxygen barrier coating solution. To ensure uniform dispersion of particles in the coating solution and prevent precipitation, the particle size is typically controlled below 10 μm. The roughness is optimized to be such that details are not visible to the naked eye, with an optimal range of 0.1-5 μm.

[0061] Of the total dry weight of the oxygen barrier layer, 50%-70% is oxygen barrier resin containing hydroxyl groups; 20%-45% is polyurethane resin containing isocyanate monomers; and 5%-10% is leveling agent. Polyurethane resin containing isocyanate monomers is also known as polyurethane resin containing free isocyanate monomers.

[0062] All raw materials used in the oxygen barrier layer are soluble in mainstream commercially available flexographic washing media, such as organic solvents containing tetrachloroethylene / n-butanol or those containing terpenes or commercially available high-end environmentally friendly developer from Shanghai Minchen, and will not undergo photopolymerization, thus avoiding residues in subsequent plate-making processes.

[0063] The thickness of the oxygen barrier layer is 0.5-5μm, with 1μm-2μm being particularly preferred. While a thicker oxygen barrier layer can improve oxygen barrier performance, it can lead to dot gain, which becomes a problem for the printing plate. Furthermore, a thicker oxygen barrier layer is prone to breakage at low temperatures. A thinner oxygen barrier layer does not adequately block oxygen, and the cross-linking of small dots is partially affected by oxygen, preventing proper reduction. Since the oxygen barrier layer's dissolution and swelling in the washing solution should be minimal, the less oxygen barrier layer, the better, while maintaining effective oxygen barrier properties.

[0064] Laser-ablative mask layer (D) The laser-ablable mask layer (D), also known as the laser-ablable black film, is located between the oxygen barrier layer (C) and the removable protective film (E), and it must meet the following performance requirements: Laser ablation: It can absorb infrared lasers and be ablated by laser imaging, and is suitable for laser imaging machines with wavelengths such as 830nm and 1064nm commonly used in the market.

[0065] UV blocking: During the UVA exposure stage of the plate-making process, it can effectively block ultraviolet rays, preventing the photosensitive elastomer layer (B) covered by it from undergoing cross-linking polymerization reaction.

[0066] Plate washing compatibility: It can be dissolved or dispersed in commercially available flexographic plate washing solutions.

[0067] The laser-ablable mask layer (D) is a conventional laser ablation mask in the prior art, and its main components include: Infrared absorption and ablation component: Selected from materials capable of absorbing infrared radiation and being ablated, such as carbon black, graphite, carbon nanoparticles, carbon nanotubes, etc., more preferably carbon nanotubes. This component also has ultraviolet blocking function. Based on the total weight of the laser-ablable mask layer (D), its content is 10-60 wt%, preferably 20-40 wt%.

[0068] Flexible elastic adhesive: selected from ethylene-vinyl acetate, flexible elastic polyamide, flexible elastic polyurethane, polyvinylpyrrolidone (PVP), nitrocellulose, polyvinyl acetal (such as poly(vinyl butyral-vinyl alcohol) copolymer (Butvar®, Mowital®), poly(vinyl butyral-vinyl acetal-vinyl alcohol) copolymer (Pioloform®)) or partially hydrolyzed polyvinyl acetate, etc.; preferably flexible elastic polyamide Technomelt® PA6900.

[0069] Optical density requirement: The optical density of the laser-ablable mask layer (D) to UVA radiation (wavelength 300-400nm) is 1-5, preferably 2-5. The optical density is the logarithmic coefficient of the light transmittance of the layer within this wavelength range, and its measured value is the average light transmittance within a specified wavelength range. It can be measured using a commercially available densitometer (e.g., X-Rite products) within the UVA wavelength range.

[0070] Dry coating amount and ablation energy: The dry coating amount of the laser-ablable mask layer (D) is 2-5 g / m², preferably 2-4 g / m². Within this range, its ablation energy is approximately 3.0-4.5 J / cm², which is compatible with commercially available flexographic laser ablation imaging machines, ensuring that the imaging machine is in normal working condition and at a reasonable working efficiency.

[0071] The thickness of the laser-ablated mask layer is 0.5-5μm.

[0072] Protective film (E) The removable protective film (E) is the outermost layer of the flexible resin plate, used to protect the plate body, and needs to be removed before laser ablation imaging. The material of the removable protective film (E) is preferably PET film, with a thickness of 80-150 μm, more preferably 100-130 μm; its average surface roughness (Ra) is preferably 0.02-0.5 μm. The removable protective film (E) can be transparent or translucent, preferably with a certain degree of haze to facilitate differentiation between the front and back sides of the plate.

[0073] The UV-polymerizable photosensitive elastomer layer (B) (the part of the photosensitive elastomer layer that does not participate in photopolymerization), the oxygen barrier layer (C), and the laser-ablable mask layer (D) can all be dissolved or dispersed in mainstream commercially available flexographic printing media, such as organic solvents containing tetrachloroethylene / n-butanol or containing terpenes, or commercially available high-end environmentally friendly developer from Shanghai Minchen.

[0074] Production of flexographic printing plates according to this invention The flexographic printing plate of this invention is prepared in a manner known in the art: the components of the photosensitive elastomer layer are melted and mixed in an extruder, and the melt is extruded through a slit die into the roll gap of a calender to form the photosensitive elastomer layer. A support, optionally coated with other layers (such as an adhesive layer), travels on one calender roll; a pre-fabricated outer film comprising a laser ablation mask and an oxygen barrier layer travels on another calender roll. The dimensionally stable support, the photosensitive elastomer layer, and the outer film with the oxygen barrier layer and the laser ablation mask layer are composited into a single unit through a calendering process.

[0075] In the fabrication of the outer membrane assembly, a laser-ablable mask layer is first coated onto the outer membrane surface. This coating process can be carried out using solution coating, melt coating, or spray coating. Subsequently, an oxygen barrier layer is applied over the laser-ablable mask layer. Before applying subsequent layers, the surface of the PET substrate to be coated may need to be treated with methods such as corona treatment to improve its spreading performance. It should be noted that the effect of corona pretreatment typically weakens with prolonged plate storage time and cannot achieve durable and ideal adhesion.

[0076] As an alternative, each layer can be coated onto different membrane materials and then laminated. For example, the mask layer and the oxygen barrier layer can be coated onto separate membrane materials: specifically, the mask layer is coated onto the outer membrane and the oxygen barrier layer is coated onto the temporary auxiliary membrane; after coating, the two membranes are laminated together, and then the temporary auxiliary membrane is removed.

[0077] Coating techniques are well known to those skilled in the art. The thickness of the coating layer can be adjusted in ways known in the art, such as diluting the coating solution or changing coating parameters (e.g., blade gap, coating speed, and feed rate). To improve coating quality, it may be necessary to add surfactants or leveling agents to the coating solution.

[0078] The coated outer film is rolled up and passed through one of the calendering rollers during the subsequent extrusion process, thus firmly bonding it with the photosensitive elastomer to form a whole printing plate.

[0079] As an alternative, a multi-step layer-by-layer lamination method can also be used. For example, the oxygen barrier layer supported on the temporary auxiliary film can be passed through a calendering roller and laminated with the photopolymerizable layer; then the auxiliary film can be removed; subsequently, in the second lamination step, the laser ablation mask layer and the photosensitive elastomer with the composite oxygen barrier layer can be laminated to obtain the printing plate.

[0080] The method for making the flexible resin plate includes the following steps: (1) Preparation of oxygen barrier coating liquid: Dissolve the oxygen barrier resin containing hydroxyl groups in an organic solvent, add polyurethane resin containing free isocyanate monomer under stirring conditions of 300-400r / min, add it within 15min, and then stir at high speed of 1000r / min for 3h to form a suspension containing polymer particles, and then add leveling agent and stir to mix evenly. (2) Forming an oxygen barrier layer-laser ablation mask layer composite: The coating liquid of step (1) is coated on the other surface of the laser ablation mask layer with a protective film at a speed of 30 m / min, and dried at 120℃ for 10 min to form an oxygen barrier layer with a thickness of 1-2 μm, thus obtaining a laser ablation mask with a frosted flat-top dot structure oxygen barrier layer, which is also an oxygen barrier layer-laser ablation mask layer composite. (3) Composite and plate making: The oxygen barrier layer in the composite of step (2) is sequentially composited with the photosensitive elastomer layer and the support. After exposure, laser ablation and flexographic washing medium washing, a flat-top dot flexible resin plate with sand pattern on the surface is obtained, and the oxygen barrier layer is completely removed without residue during the washing process.

[0081] The present invention will now be described in detail with reference to specific embodiments. It should be noted that these embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above description of the present invention.

[0082] Example 1 This patent is achieved by adding an oxygen barrier layer to the digital flexible plate. The technical details of the digital flexible plate involved are omitted.

[0083] In the preparation of the oxygen barrier coating solution, the components are prepared according to the following weight ratios, with a total weight of 110 kg: Ethyl cellulose M70 (degree of substitution of ethyl cellulose M70 is 2.3), commercially available, 7 kg; polyurethane resin with molecular weight of 2000 (isocyanate monomer content 15%) JL-2000, from Polytechnic Technology Co., Ltd., 2.5 kg; leveling agent—BYK333, from BYK (Germany), 0.5 kg; propylene glycol methyl ether, commercially available solvent, 100 kg. Huaguang DR170H type photosensitive elastomer, from Lucky Huaguang Printing Technology Co., Ltd., is a commercially available product.

[0084] The preparation method of the oxygen barrier coating solution is as follows: Dissolve 7 kg of ethyl cellulose in 100 kg of propylene glycol methyl ether. After it is completely dissolved, add 2.5 kg of polyurethane resin under stirring at 300-400 r / min, and add it within 15 min. Then stir at high speed of 1000 r / min for 3 h until a suspension is formed. Finally, add 0.5 kg of leveling agent BYK333 and stir at 300-400 r / min for 10 min to obtain the oxygen barrier coating solution.

[0085] The aforementioned oxygen barrier coating solution was applied at a speed of 30 m / min to the other surface of the laser-ablable mask layer (D) with a protective film (E). The layer was dried at 120°C for 10 min to form an oxygen barrier layer with a thickness of 1.6 μm and a dry weight of 4.85 g / m², thus obtaining a laser ablation mask with a frosted flat-top dot structure oxygen barrier layer. This laser ablation mask was then pressed onto the surface of a Huaguang DR170H photosensitive elastomer (which has a support structure). The printing plate was dried at 100-120°C and cooled to room temperature to obtain a raw printing plate.

[0086] The resulting green plate, without removing the protective film (E), is first back-exposed for 20 seconds (at 365nm, light intensity 17.1mw / cm²). 2 Then, the protective film (E) is peeled off, and the flexible resin plate of the present invention is fed into a CDI SPARK 2120 plate-making machine (manufactured by ESKO Corporation). At 2540dpi, the imaging speed is set to Optics 10.0, the main laser wavelength is 1064nm, and the laser ablation mask layer (D) is ablated. The ablation pattern contains dots of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, and 100% at 150lpi, containing solids, independent positive and negative lines of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm, and independent dots and independent negative dots of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm.

[0087] After laser ablation, the plate was exposed to UV-A light for 720 seconds (365nm, 17.1mw / cm²). 2 Alternatively, scan the plate ten times with a UV-LED lamp (365nm, 809.5mW / cm). 2 The plate was washed using Shanghai Minchen's high-end environmentally friendly developer at a speed of 180 mm / min, dried in a 60℃ oven for 1.5 hours, de-adhesive for 5 minutes, and then exposed for 5 minutes. A 3D microscope and Vipflex 334 were used to evaluate the presence of texture on the solid surface, the size of the 2% dot reproduction, the size of independent dots, and whether the dots were flat-topped.

[0088] Example 2 In the preparation of the oxygen barrier coating solution, the components are prepared according to the following weight ratios, with a total weight of 110 kg: Ethyl cellulose M70 (degree of substitution of ethyl cellulose M70 is 2.3), commercially available, 5.5 kg; polyurethane resin with molecular weight of 2000 (isocyanate monomer content 15%) JL-2000, from Polytechnic Technology Co., Ltd., 3.0 kg; leveling agent—BYK333, from BYK (Germany), 1.0 kg; propylene glycol methyl ether, commercially available solvent, 100 kg.

[0089] The preparation method of the oxygen barrier coating solution is as follows: Dissolve 5.5 kg of ethyl cellulose in 100 kg of propylene glycol methyl ether. After it is completely dissolved, add 3.0 kg of polyurethane resin under stirring at 300-400 r / min, and add it within 15 min. Then stir at high speed of 1000 r / min for 3 h until a suspension is formed. Finally, add 1.0 kg of leveling agent BYK333 and stir at 300-400 r / min for 10 min to obtain the oxygen barrier coating solution.

[0090] The above-mentioned oxygen barrier coating solution was applied to the other surface of the laser ablation mask layer (D) with a protective film (E) at a speed of 30 m / min. It was then dried at 120°C for 10 min to form an oxygen barrier layer with a thickness of 1.6 μm and a dry weight of 4.79 g / m², thus obtaining a laser ablation mask with a frosted flat-top dot structure oxygen barrier layer. This laser ablation mask was then pressed onto the surface of a Huaguang DR170H photosensitive elastomer (which has a support structure). The printing plate was dried at 100-120°C and cooled to room temperature to obtain a raw printing plate.

[0091] The resulting green plate, without removing the protective film (E), is first back-exposed for 20 seconds (at 365nm, light intensity 17.1mw / cm²). 2Then, the protective film (E) is peeled off, and the flexible resin plate of the present invention is fed into a CDI SPARK 2120 plate-making machine (manufactured by ESKO Corporation). At 2540dpi, the imaging speed is set to Optics 10.0, the main laser wavelength is 1064nm, and the laser ablation mask layer (D) is ablated. The ablation pattern contains dots of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, and 100% at 150lpi, containing solids, independent positive and negative lines of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm, and independent dots and independent negative dots of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm.

[0092] After laser ablation, the plate was exposed to UV-A light for 720 seconds (365nm, 17.1mw / cm²). 2 Alternatively, scan the plate ten times with a UV-LED lamp (365nm, 809.5mW / cm). 2 The plate was washed using Shanghai Minchen's high-end environmentally friendly developer at a speed of 180 mm / min, dried in a 60℃ oven for 1.5 hours, de-adhesive for 5 minutes, and then exposed for 5 minutes. A 3D microscope and Vipflex 334 were used to evaluate the presence of texture on the solid surface, the size of the 2% dot reproduction, the size of independent dots, and whether the dots were flat-topped.

[0093] Compare with Example 1 In the preparation of the oxygen barrier coating solution, the components are prepared according to the following weight ratios, with a total weight of 103 kg: Polyurethane resin with a molecular weight of 2000 (isocyanate monomer content 15%) JL-2000, from Polytechnic Technology Co., Ltd., 2.5Kg; leveling agent—BYK333, from BYK (Germany), 0.5Kg; propylene glycol methyl ether, commercially available solvent, 100Kg.

[0094] The preparation method of the oxygen barrier coating solution is as follows: 2.5Kg of polyurethane resin is added to 100Kg of propylene glycol methyl ether, stirred and dissolved at a speed of 300-400r / min, then 0.5Kg of surfactant is added, and stirring is continued for 10 minutes to obtain the coating solution.

[0095] The coating solution was applied to the other surface of the laser-ablable mask layer (D) with a protective film (E) at a speed of 30 m / min, and dried at 120 °C for 10 min to obtain a thickness of 1.3 μm and a dry weight of 1.55 g / m. 2A coating was applied to prepare a laser ablation mask. This laser ablation mask was then pressed onto a Huaguang DR170H photosensitive elastomer (the Huaguang DR170H photosensitive elastomer has a support). The mask was dried at 100-120℃. After cooling to room temperature, a raw mask was produced.

[0096] The resulting green plate, without removing the protective film (E), is first back-exposed for 20 seconds (at 365nm, light intensity 17.1mw / cm²). 2 Then, the protective film (E) is peeled off, and the flexible resin plate of the present invention is fed into a CDI SPARK 2120 plate-making machine (manufactured by ESKO Corporation). At 2540dpi, the imaging speed is set to Optics 10.0, the main laser wavelength is 1064nm, and the laser ablation mask layer (D) is ablated. The ablation pattern contains dots of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, and 100% at 150lpi, containing solids, independent positive and negative lines of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm, and independent dots and independent negative dots of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm.

[0097] After laser ablation, the plate was exposed to UV-A light for 720 seconds (365nm, 17.1mw / cm²). 2 Alternatively, scan the plate ten times with a UV-LED lamp (365nm, 809.5mW / cm). 2 The plate was washed using Shanghai Minchen's high-end environmentally friendly developer at a speed of 180 mm / min, dried in a 60℃ oven for 1.5 hours, de-adhesive for 5 minutes, and then exposed for 5 minutes. A 3D microscope and Vipflex 334 were used to evaluate the presence of texture on the solid surface, the size of the 2% dot reproduction, the size of independent dots, and whether the dots were flat-topped.

[0098] Compare with Example 2 In the preparation of the oxygen barrier coating solution, the total weight of the following components is 110 kg: Ethyl cellulose M70 (degree of substitution of ethyl cellulose M70 is 2.3), commercially available, 7.0 kg; polyurethane resin with molecular weight of 2000 (free isocyanate-free) JL-2000, from Polytechnic Technology Co., Ltd., 2.5 kg; leveling agent—BYK333, from BYK (Germany), 0.5 kg; propylene glycol methyl ether, commercially available solvent, 100 kg.

[0099] The preparation method of the oxygen barrier coating solution is as follows: Dissolve 7.0 kg of ethyl cellulose in 100 kg of propylene glycol methyl ether. After it is completely dissolved, add 2.5 kg of polyurethane resin under stirring at 300-400 r / min, and add it within 15 min. Then stir at high speed of 1000 r / min for 3 h until a suspension is formed. Finally, add 0.5 kg of leveling agent BYK333 and stir at 300-400 r / min for 10 min to obtain the oxygen barrier coating solution.

[0100] The above-mentioned oxygen barrier coating solution was applied to the other surface of the laser ablation mask layer (D) with a protective film (E) at a speed of 30 m / min. It was then dried at 120°C for 10 min to form an oxygen barrier layer (adhesive layer) with a thickness of 1.6 μm and a dry weight of 4.70 g / m², thus obtaining a laser ablation mask with a frosted flat-top dot structure oxygen barrier layer. This laser ablation mask was then pressed onto the surface of a Huaguang DR170H photosensitive elastomer (which has a support structure). The printing plate was dried at 100-120°C and cooled to room temperature to obtain a raw plate.

[0101] The resulting green plate, without removing the protective film (E), is first back-exposed for 20 seconds (at 365nm, light intensity 17.1mw / cm²). 2 Then, the protective film (E) is peeled off, and the flexible resin plate of the present invention is fed into a CDI SPARK 2120 plate-making machine (manufactured by ESKO Corporation). At 2540dpi, the imaging speed is set to Optics 10.0, the main laser wavelength is 1064nm, and the laser ablation mask layer (D) is ablated. The ablation pattern contains dots of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, and 100% at 150lpi, containing solids, independent positive and negative lines of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm, and independent dots and independent negative dots of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm.

[0102] After laser ablation, the plate was exposed to UV-A light for 720 seconds (365nm, 17.1mw / cm²). 2 Alternatively, scan the plate ten times with a UV-LED lamp (365nm, 809.5mW / cm). 2The plate was washed using Shanghai Minchen's high-end environmentally friendly developer at a speed of 180 mm / min, dried in a 60℃ oven for 1.5 hours, de-adhesive for 5 minutes, and then exposed for 5 minutes. A 3D microscope and Vipflex 334 were used to evaluate the presence of texture on the solid surface, the size of the 2% dot reproduction, the size of independent dots, and whether the dots were flat-topped.

[0103] Compare with Example 3 The Huaguang DR170H flexible digital plate structure includes a support (A), a photosensitive elastomer layer (B), a laser-ablable mask layer (D), and a protective film (E), but does not include an oxygen barrier layer with particles.

[0104] The above raw image, without removing the protective film (E), is first back-exposed for 20 seconds (at 365nm, light intensity 17.1mw / cm²). 2 Then, the protective film (E) is peeled off, and the flexible resin plate of the present invention is fed into a CDI SPARK 2120 plate-making machine (manufactured by ESKO Corporation). At 2540dpi, the imaging speed is set to Optics 10.0, the main laser wavelength is 1064nm, and the laser ablation mask layer (D) is ablated. The ablation pattern contains dots of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, and 100% at 150lpi, containing solids, independent positive and negative lines of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm, and independent dots and independent negative dots of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm.

[0105] After laser ablation, the plate was exposed to UV-A light for 720 seconds (365nm, 17.1mw / cm²). 2 Alternatively, scan the plate ten times with a UV-LED lamp (365nm, 809.5mW / cm). 2 The plate was washed using Shanghai Minchen's high-end environmentally friendly developer at a speed of 180 mm / min, dried in a 60℃ oven for 1.5 hours, de-adhesive for 5 minutes, and then exposed for 5 minutes. A 3D microscope and Vipflex 334 were used to evaluate the presence of texture on the solid surface, the size of the 2% dot reproduction, the size of independent dots, and whether the dots were flat-topped.

[0106] Compare with Example 4 Example 2 of CN114474959A was repeated as a control example for washing residue.

[0107] In the preparation of the oxygen barrier coating solution, the total weight of the following components is 100 kg: Polyvinylpyrrolidone K90, commercially available, 4.0 kg; Amino acid-containing water-soluble resin PD-70000 with a molecular weight of 70000, from Lucky Chemicals Co., Ltd., 2.4 kg; Carboxyl-containing flexible resin SR, from Lucky Chemicals Co., Ltd., 1.0 kg; Perfluorobutyl sulfonyl fluoride, commercially available solvent, 0.6 kg.

[0108] The preparation method of the oxygen barrier coating solution is as follows: Dissolve 4.0 kg of polyvinylpyrrolidone and 92 kg of deionized water together, slowly add 2.4 kg of PD-70000 resin under high-speed stirring (1000-2000 r / min), and finally add 0.6 kg of surfactant perfluorobutyl sulfonyl fluoride. Stir at 300-400 r / min for 10 min to obtain the oxygen barrier coating solution.

[0109] The above-mentioned oxygen barrier coating solution was applied to the other surface of the laser ablation mask layer (D) with a protective film (E) at a speed of 30 m / min. It was then dried at 120°C for 10 min to form an oxygen barrier layer (adhesive layer) with a thickness of 1.2 μm and a dry weight of 4.70 g / m², thus obtaining a laser ablation mask with a frosted flat-top dot structure oxygen barrier layer. This laser ablation mask was then pressed onto the surface of a Huaguang DR170H type photosensitive elastomer (which has a support structure). The printing plate was dried at 100-120°C and cooled to room temperature to obtain a raw plate.

[0110] The resulting green plate, without removing the protective film (E), is first back-exposed for 20 seconds (at 365nm, light intensity 17.1mw / cm²). 2 Then, the protective film (E) is peeled off, and the flexible resin plate of the present invention is fed into a CDI SPARK 2120 plate-making machine (manufactured by ESKO Corporation). At 2540dpi, the imaging speed is set to Optics 10.0, the main laser wavelength is 1064nm, and the laser ablation mask layer (D) is ablated. The ablation pattern contains dots of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, and 100% at 150lpi, containing solids, independent positive and negative lines of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm, and independent dots and independent negative dots of 0.08mm, 0.10mm, 0.15mm, 0.20mm, and 0.30mm.

[0111] After laser ablation, the plate was exposed to UV-A light for 720 seconds (365nm, 17.1mw / cm²). 2 Alternatively, scan the plate ten times with a UV-LED lamp (365nm, 809.5mW / cm).2 The plate was washed using Shanghai Minchen's high-end environmentally friendly developer at a speed of 180 mm / min, dried in a 60℃ oven for 1.5 hours, de-adhesive for 5 minutes, and then exposed for 5 minutes. A 3D microscope and Vipflex 334 were used to evaluate the presence of texture on the solid surface, the size of the 2% dot reproduction, the size of independent dots, and whether the dots were flat-topped.

[0112] The 3D images and contour images of the flexible resin plates prepared in Examples 1-2 and Comparative Examples 1-3 with 5% dots at 150 lpi are as follows: Figure 1-5 ; Figure 6 This is a photograph of the printing plate from Example 1, which has a frosted texture. Figure 6 The black, droplet-like or stripe-like images are the frosted texture on the solid material of the printing plate. Because they are pits, they appear black under a microscope. Figure 7 This is a photo of the actual printing plate in Example 1, which has no matte texture and is relatively smooth; Figure 8 This is a photograph of the solid plate material remaining after washing in Control Example 4, taken under a 500x microscope. The evaluation results of Examples 1-2 and Control Examples 1-4 are shown in Table 1.

[0113] Table 1 Evaluation results of Examples 1-2 and Control Examples 1-4 Comparative Examples 1 and 2 and Comparative Examples 1 and 3 show that the amount of oxygen barrier affects the dot shape, dot reproduction performance and independent dot size. Comparative Examples 1 and Comparative Examples 1, 2 and 3 show that in order to form a texture on the surface of the printing plate, both the isocyanate in the adhesive and the hydroxyl-containing oxygen barrier are indispensable.

[0114] In summary, as shown in Table 1, the technology of this invention can produce a flat-topped dotted flexible resin plate with a self-textured surface, and it works even under low-intensity UV-A lamps (365nm, 17.1mw / cm²). 2 Even under high-intensity UV-LED light sources (365nm, 809.5mW / cm²), 2 No residue issues were found during the exposure and plate-making process.

[0115] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. It should be noted that for those skilled in the art and any person skilled in the art, any equivalent substitutions or changes made to the technical solution and inventive concept of the present invention without departing from the overall concept of the present invention, as well as any changes and improvements made, should also be considered within the scope of protection of the present invention.

Claims

1. An oxygen barrier layer characterized by: The oxygen barrier layer contains particles with a diameter of 0.1-10 μm, and is formed by coating and drying an oxygen barrier layer coating liquid, the raw materials of the oxygen barrier layer coating liquid including an organic solvent, a leveling agent, a polyurethane resin containing free isocyanate monomers, and an oxygen barrier resin containing hydroxyl groups, the molar content of the hydroxyl groups in the oxygen barrier resin being greater than the molar content of isocyanate groups in the isocyanate monomers, and part of the oxygen barrier resin containing hydroxyl groups and the isocyanate monomers in the polyurethane resin reacting in the organic solvent to form the polymer particles with a diameter of 0.1-10 μm.

2. The oxygen barrier layer of claim 1, wherein: The oxygen permeability of the oxygen barrier resin containing hydroxyl groups is less than or equal to 500 (cm3×100 μm) / (m2×d×bar).

3. The oxygen barrier layer of claim 2, wherein: The oxygen barrier resin is at least one of ethyl cellulose, polyvinyl acetate with a molar hydrolysis degree of 30-70%, polyvinyl acetal with a molar hydrolysis degree of 30-70%, alkyl cellulose, cellulose acetate butyrate, and chitosan.

4. The oxygen barrier layer of claim 3, wherein: The oxygen barrier resin is ethyl cellulose with a degree of substitution of 2.3-2.

6.

5. The oxygen barrier layer of claim 1, wherein: The components and weight proportions of the oxygen barrier layer, based on the dry weight of the oxygen barrier layer, are as follows: the oxygen barrier resin containing hydroxyl groups, 50%-70%; the polyurethane adhesive resin containing free isocyanate monomers, 20%-45%; and the leveling agent, 5%-10%.

6. The oxygen barrier layer of claim 1, wherein: The organic solvent is at least one of n-butanol, ethyl acetate, methanol, ethanol, propylene glycol methyl ether, or butanone, and the boiling point of the organic solvent is less than 120°C.

7. The oxygen barrier layer of claim 1, wherein: The polyurethane resin containing free isocyanate monomers has a molecular weight of 1000-10000, and the content of the free isocyanate monomers is 10%-30%.

8. A preparation method of the oxygen barrier layer coating liquid according to any one of claims 1-7, comprising: dissolving the oxygen barrier resin containing hydroxyl groups in an organic solvent, adding the polyurethane resin containing free isocyanate monomers under stirring at 300-400 r / min, adding the polyurethane resin containing free isocyanate monomers within 15 min, and then stirring at a high speed of 900-1100 r / min for 2.9-3.1 h to form a suspension, and then adding the leveling agent and stirring to obtain the oxygen barrier layer coating liquid.

9. A flat-top dot flexible resin plate with self-grained texture on surface, comprising, from bottom to top, a support, a photosensitive elastomer layer, an oxygen barrier layer and a laser-ablatable mask layer, characterized in that: The oxygen barrier layer is the oxygen barrier layer according to any one of claims 1-8.

10. The flat-top screened flexible resinous printing form of claim 9, wherein: The thickness of the photosensitive elastomer layer is 0.1-7 mm, the thickness of the oxygen barrier layer is 0.5-5 μm, and the thickness of the laser-ablatable mask layer is 0.5-5 μm.

Images