A multi-coat ultraviolet radiation-sensitive lithographic printing plate precursor and on-press development method thereof

Abstract

This invention discloses a multi-coated ultraviolet radiation-sensitive lithographic printing plate precursor and its on-machine development method. The lithographic printing plate precursor comprises, from bottom to top: (1) an aluminum substrate that has been sequentially treated with electrochemical roughening, sulfuric acid anodizing, and hydrophilic treatment with sodium dihydrogen phosphate / sodium fluoride sealing solution; (2) a base coating containing polyvinylphosphonic acid; (3) an imageable layer containing 25-65 parts of a free radical polymerizable compound, 0.5-20 parts of an acid-generating agent, 0.5-25 parts of a free radical initiator, 0.5-20 parts of a coloring dye, and 10-70 parts of a binder; and (4) a protective layer containing highly hydrolyzable polyvinyl acetate. The lithographic printing plate precursor can be patterned and exposed to form exposed and unexposed areas with obvious color differences. Then, the exposed lithographic printing plate precursor is directly developed on a printing press using dampening solution and / or lithographic printing ink. This offset printing plate precursor has excellent thermal stability, which solves the problem of printing background contamination caused by changes in environmental conditions during product storage.

Description

Technical Field

[0001] This invention belongs to the field of offset printing plate preparation technology, specifically relating to a multi-coated ultraviolet radiation sensitive offset printing plate precursor and its plate-making method. Background Technology

[0002] Lithography is a common printing method that uses an oleophilic image area on a lithographic printing plate as the ink receiving area and a hydrophilic non-image area as the wetting water receiving area. Utilizing the mutual repulsion between the wetting water and the oil-based ink, the ink is deposited only in the image area and then transferred to a printing medium such as paper. Recent developments in lithography have benefited from the increasing prevalence of digitization technology, which uses computers to process, store, and output image information electronically. Various new image output methods corresponding to this digitization technology have been put into practical use. This has led to the development of computer-to-plate (CTP) technology, where digitized image information can be loaded onto highly focused radiation such as lasers, and the laser can be used to directly scan and expose the original lithographic printing plate. This technology has attracted considerable attention due to its advantage of eliminating the need for traditional film exposure in lithographic printing plate making, becoming one of the important technical topics in the field of lithographic printing plates.

[0003] In the traditional lithographic printing plate manufacturing process, a post-exposure treatment step involving the removal of unwanted photosensitive coatings using a developing solution (referred to as "off-machine development") is required. This process is relatively time-consuming and increases costs. Especially in recent years, due to environmental protection considerations, the disposal of wastewater generated during the development process using highly alkaline solutions has become a major concern for the entire industry. Therefore, in pursuit of further simplifying the plate-making process and reducing wastewater treatment, a plate precursor known as "on-machine development" and its plate-making method have become cutting-edge research topics in this field. This lithographic printing plate precursor allows the unexposed portions of the photosensitive coating to be removed by the mechanical contact of ink and / or dampening solution on the printing press through rotating cylinders, thereby obtaining a lithographic printing plate with an image.

[0004] On the other hand, after exposure and before mounting on the printing press, the image on the lithographic printing plate needs to be quality checked to confirm whether the intended image has been recorded on the plate. This is especially important in multicolor printing, where the alignment marks must be distinguishable. For ordinary lithographic printing plates using off-machine development, the tinted photosensitive layer and the exposed plate base after development usually have sufficient color difference, making it easy to check the image before mounting the plate on the printing press. However, if there is no clear image available for quality inspection after exposure, these "in-machine developed" lithographic printing plates, which do not undergo development, are prone to errors because they cannot be inspected before printing. For this reason, it is necessary for machine-developable printing plates to provide a reliable means of quality inspection after exposure; that is, the color difference between the exposed and unexposed areas must be sufficiently clear so that the image can be easily checked before mounting the plate on the printing press.

[0005] US Patent document US20100075258 discloses a negative-image imaging element that can be developed on a printing press. The imageable layer of this element contains an infrared radiation-absorbing compound with a cyanine structure to improve printing color quality. The imageable layer is placed on an aluminum substrate that has undergone electrochemical roughening, phosphoric acid anodizing, and is coated with a polyacrylic acid undercoat. The exposed imageable element exhibits improved printing color, achieving consistent on-press development, high sensitivity, and high print volume. However, this imaging element has poor ultraviolet radiation imaging capabilities, being sensitive only to absorption wavelengths of 700-1200 nm, requiring the addition of an infrared-sensitive photosensitizer.

[0006] Compared to the widespread application of infrared-sensitive printing plate precursors, ultraviolet-sensitive on-machine developing printing plate precursors are rarely reported. CN115352177B discloses an ultraviolet-sensitive lithographic printing plate precursor with color development function and its plate-making method, providing a treatment-free photosensitive negative printing plate suitable for on-machine developing quality control. This invention introduces a useful hydrophilic lithographic printing substrate as an aluminum support that is electrochemically ground and anodized with sulfuric acid or phosphoric acid, but does not specify the method used for hydrophilic treatment of the aluminum support.

[0007] Among the many methods for treating aluminum substrates, the advantages of electrochemical roughening, sulfuric acid anodizing, and hydrophilic treatment with sodium dihydrogen phosphate / sodium fluoride sealing solution are (1) avoiding the emission of pollutants such as nitric acid and phosphoric acid, and (2) the use of low-cost sodium dihydrogen phosphate / sodium fluoride sealing solution materials. However, this type of aluminum substrate is quite sensitive to in-machine developability or image clarity, especially after a period of storage or during transportation when the temperature rises, causing the removal of unexposed parts during in-machine development to slow down or even become dirty; in addition, adding color dyes to the imageable layer may also impair the shelf life. These problems are the issues addressed in this invention. Summary of the Invention

[0008] One object of the present invention is to provide a UV-sensitive lithographic printing plate precursor that can be directly developed and plated on a printing press, and which exhibits excellent thermal stability during storage. Another object is to provide a method for preparing the lithographic printing plate precursor, which enables the formation of a pattern with significant color difference after exposure and eliminates the need for off-machine development before printing.

[0009] To achieve the above objectives, the present invention discloses a multi-coated ultraviolet radiation-sensitive offset printing plate precursor, characterized in that it comprises (a) a substrate, (b) a base coating layer covering the substrate, (c) an imageable layer covering the base coating layer, and (d) a protective layer covering the imageable layer; wherein, the substrate is an aluminum sheet substrate that has been sequentially treated with electrochemical roughening, sulfuric acid anodizing, and hydrophilic treatment with sodium dihydrogen phosphate / sodium fluoride sealing solution; the base coating layer is a coating containing polyvinylphosphonic acid; the imageable layer is an ultraviolet radiation-sensitive coating containing 25-65 parts of a free radical polymerizable compound, 0.5-20 parts of an acid-generating agent, 0.5-25 parts of a free radical initiator, 0.5-20 parts of a coloring dye, and 10-70 parts of a binder; and the protective layer is a coating containing highly hydrolyzable polyvinyl acetate.

[0010] Furthermore, the average roughness R of the aluminum sheet substrate surface layer... a The alumina thickness is 0.40-0.80 μm, and the surface alumina weight is 1.5-4.0 g / m². 2 The solute composition of the sodium dihydrogen phosphate / sodium fluoride sealing solution is 90-99.8 parts of sodium dihydrogen phosphate and 0.2-10 parts of sodium fluoride; The coverage of the base coating is 10-30 mg / m². 2 Preferred concentration: 15-25 mg / m² 2 The coverage of the imageable layer is 0.6-1.6 g / m². 2 The preferred dosage is 0.8-1.4 mg / m³. 2 ; The coverage of the protective layer is 0.3-1.3 g / m². 2 The preferred dosage is 0.4-0.8 mg / m³. 2 ; The free radical polymerizable compound is one or more of acrylates, methacrylates, urethane acrylates, urethane methacrylates, epoxide acrylates or epoxide methacrylates, acrylates of polyols, methacrylates of polyols, polyurethane acrylates, polyurethane methacrylates, polyether acrylates, and polyether methacrylates; the acid-generating agent is one or more of onium salts and trihalomethyl compounds. The free radical initiator has one or more absorption peaks or absorption bands in the 350nm-450nm UV-violet light range, and can be selected from one or more of carbonyl compounds, coumarins, anthraquinones, organoboron compounds, oxime esters or phosphine oxides; The coloring dye is one or more compounds containing lactones, lactams, sulopentalides, and spiropyrans; The adhesive is a polymer derived from at least one of the following as repeating units: acrylic acid, methacrylic acid, acrylate, methacrylate, acrylamide, methacrylamide, styrene and styrene derivatives, acrylonitrile, methacrylonitrile, N-substituted cyclic imide, and maleic anhydride. The degree of hydrolysis of the polyvinyl acetate is 80% to 99.9%.

[0011] Another object of the present invention is to provide a method for making a multi-coated ultraviolet radiation sensitive lithographic printing plate precursor, characterized by comprising the following steps: (a) Patterning exposure of the aforementioned multi-coated UV-sensitive offset printing plate precursor, thereby forming exposed and unexposed areas with obvious color differences; (b) Using dampening solution and / or lithographic printing ink, the exposed lithographic printing plate precursor is developed directly on the printing press.

[0012] Compared with the prior art, the technical solution of the present invention has the following advantages: 1) This invention effectively solves the problem of poor compatibility between the aluminum substrate, which has undergone electrochemical roughening, sulfuric acid anodizing, and sodium dihydrogen phosphate / sodium fluoride sealing hydrophilic treatment, and the imaging layer, resulting in poor shelf life and thermal stability of the printing plate precursor. This is achieved by applying a base coating containing polyvinylphosphonic acid between the hydrophilic substrate and the imaging layer, thus avoiding product deterioration during transportation and storage.

[0013] 2) By selecting a polyphosphonic acid base coating with strong acidity and its appropriate coverage, this invention allows the acid-sensitive color dye and the imaging layer to benefit from the acidity of the surrounding environment, which is beneficial to improving the effect and stability of the printing color difference after the printing plate precursor is exposed, thus meeting the customer's plate-making needs for the on-machine developing photosensitive negative type offset printing plate precursor.

[0014] 3) Compared with the existing substrate treatment technology for on-machine developing plates, the present invention adopts hydrochloric acid electrochemical roughening, sulfuric acid anodizing and sodium dihydrogen phosphate / sodium fluoride sealing solution hydrophilic treatment process, which has more competitive advantages in terms of environmental protection and cost, avoids the emissions generated by using nitric acid or phosphoric acid as electrolyte and reduces the investment in production equipment. Detailed Implementation

[0015] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below in conjunction with specific embodiments. This invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. In this invention, the terms "UV-sensitive lithographic printing plate precursor," "lithographic printing plate precursor," "plate precursor," and "precursor" are used interchangeably with respect to embodiments of the invention. In this invention, the term "off-machine development" refers to the step of removing the image recording layer of a lithographic printing plate precursor by contacting it with a liquid (typically a developer solution) in an apparatus (typically an automatic plate processor), thereby exposing the surface of a hydrophilic substrate; the term "on-machine development" refers to the step of removing the image recording layer of a lithographic printing plate precursor by contacting it with ink and / or dampening solution on a printing press, thereby exposing the surface of a hydrophilic substrate; the term "treatment-free" refers to a plate-making method that requires no mechanical or chemical treatment after exposure and before printing, unless otherwise specified.

[0016] The following is a detailed description of the lithographic printing plate precursor and its plate-making method of the present invention.

[0017] A. Pre-printing plate for offset printing: The lithographic printing plate precursor used in this invention is characterized by its multi-layered structure, comprising, from bottom to top: (a) a base layer, (b) a base coating layer covering the base layer, (c) an imageable layer covering the base coating layer, and (d) a protective layer covering the imageable layer. The specific structure and composition of each coating layer are described in detail below: a. Base: In the lithographic printing plate precursor of this invention, the substrate is composed of an aluminum sheet support known in the art. Its manufacturing method includes roughening by physical (mechanical) grinding or electrochemical grinding, followed by sulfuric acid anodizing to obtain an aluminum oxide surface layer, and finally covering the oxide layer with a hydrophilic layer containing phosphates / fluorides. The thickness of the substrate can be varied but should be sufficient to withstand printing abrasion and flexible enough for winding; commonly used thicknesses are 0.1 mm to 0.8 mm, preferably in the range of 0.1 to 0.5 mm.

[0018] The grinding method generally employs electrochemical grinding to produce an average roughness (Ra) between 0.2 and 0.8 μm, preferably in the range of 0.4 to 0.8 μm. Acidic anodizing of the aluminum sheet support typically produces a roughness of 1-5 g / m² on the aluminum surface. 2 Oxides, more typically 1.5-4 g / m 2 The coverage is high. Sulfuric acid is preferred as the acid medium for anodizing. When using sulfuric acid for anodizing, a higher oxide weight can provide a longer print life.

[0019] The anodized aluminum sheet support can be treated with phosphate / fluoride materials to improve its hydrophilicity. A preferred hydrophilic layer comprises the following components in parts by weight: 90–99.8 parts phosphate and 0.2–10 parts fluoride.

[0020] b. Primer coating: In the lithographic printing plate precursor involved in this invention, an undercoat layer, sometimes also called an intermediate layer, is specifically chosen between the aluminum sheet support and the imageable layer. For negative lithographic printing plate precursors, since it is necessary to strengthen the adhesion between the support and the imageable layer in the exposed area, and to ensure that the imageable layer can be easily peeled off from the support in the unexposed area, this undercoat layer helps to alleviate the problem of poor shelf life and thermal stability of the printing plate precursor caused by poor compatibility between the aluminum sheet base and the imageable layer. At the same time, it has the effect of preventing the heat generated by exposure from diffusing to the support and reducing sensitivity, and is beneficial to improving the effect and stability of the printing color difference after the printing plate precursor is exposed.

[0021] The compounds used in the primer layer are preferably polymers of monomers having adsorption groups or / and monomers having hydrophilic groups, for example, monomers containing -PO3H2, -OPO3H2, -COCH2, carboxyl or hydroxyl groups.

[0022] Specifically, the preferred base coating material used in this invention is polyvinylphosphonic acid, which is available from FEW Chemicals (Germany).

[0023] The primer coating can be applied to the substrate using known methods such as extrusion coating, rod coating, roller coating, blade coating, or solution immersion. The coating weight (solid content) is preferably 10-30 mg / m³. 2 More preferably 15-25 mg / m 2 .

[0024] c. Imageable layer: The lithographic printing plate precursor involved in this invention has an imageable layer covering an undercoat layer.

[0025] The imageable layer used in this invention comprises a specific free radical polymerizable compound, an acid-generating agent, a free radical initiator, a coloring dye, and a binder. The details of each component contained in the imageable layer are described below.

[0026] Free radical polymerizable compounds: Radical polymerizable compounds are well known to those skilled in the art and have been described in a considerable number of publications, including: "Photoreactive Polymers: The Science and Technology of Resists," A. Reiser, Wiley, New York, 1989, pp. 102-177; B.M. Monroe, "Radiation Curing: Science and Technology," SPPappas, Ed., Plenum, New York, 1992, pp. 399-440; "Polymer Imaging," A.B. Cohen and P. Walker; "Imaging Processes as Material," I.M. Sturge et al., Van Nostrand Reinhold, New York, 1989, pp. 226-262. Additionally, useful radical polymerizable components are described in European Patent 1,182,033 (Fujimaki et al.).

[0027] According to the present invention, the free radical polymerizable compound is a polymeric monomer or oligomer containing at least one olefinic unsaturated double bond, preferably one or more of the following: acrylates of polyols, methacrylates of polyols, urethane acrylates, urethane methacrylates, epoxide acrylates, epoxide methacrylates, polyester acrylates, polyester methacrylates, polyether acrylates, and polyether methacrylates.

[0028] Suitable free radical polymerizable monomers may include, for example, polyfunctional acrylate monomers or polyfunctional methacrylate monomers (e.g., ethylene glycol, trimethylolpropane, pentaerythritol, ethoxylated ethylene glycol, ethoxylated trimethylolpropane acrylate, ethoxylated trimethylolpropane methacrylate, polyfunctional urethane acrylate, polyfunctional urethane methacrylate, epoxidized acrylate, and epoxidized methacrylate), and oligomeric diacrylates. In addition to acrylate groups and methacrylate groups, acrylic monomers or methacrylate monomers may also have other double bonds or epoxide groups. The acrylic monomer or methacrylate monomer may also contain acid (e.g., carboxylic acid) or base (e.g., amine) functionality. Useful free radical polymerizable compounds include dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, bis(trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate, and other polymerizable monomers that are obvious to those skilled in the art.

[0029] The amount of the free radical polymerizable component present in the composition is sufficient to prevent the UV-sensitive composition from being removed by ink and / or dampening solution on the printing press after radiation exposure. This is generally 25-65% by weight, preferably 30-65% by weight, based on the dry weight of the radiation-sensitive composition.

[0030] Acid-producing agents: The acid-producing agent is a photo-induced acid-producing agent that generates proton acids through photo-initiated decomposition. In this invention, it exists as a precursor of the acid chromogenic agent in an imageable ultraviolet light-sensitive composition and can be selected from one or more onium salts and trihalomethyl compounds.

[0031] Suitable onium salts include sulfonium salts, iodonium salts, phosphonium salts, and diazonium salts. Specific examples include diphenyliodonium chloride, diphenyliodonium hexafluorophosphate, (4-methylphenyl)[4-(2-methylpropyl)-phenyl]iodonium hexafluorophosphate, bis(4-tert-butylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium octylsulfate, diphenyliodonium octylthiosulfate, diphenyliodonium 2-carboxylic acid, and N-methyl-2-methyl-2-carboxylic acid. Oxy-α-methylpyridinium, 4-methoxyphenyl diazonium tetrafluoroborate, 2-cyanoethyl triphenylphosphine chloride, bis-[4-diphenylsulfonium phenyl]sulfide of bis(hexafluorophosphate), bis-4-dodecylphenyliodomonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium octyl sulfate, phenoxyphenyl diazonium hexafluoroantimonate, and phenylaminophenyl diazonium hexafluoroantimonate.

[0032] Suitable trihalomethyl compounds include trichloromethyltriazine compounds, such as those described in U.S. Patents 3,779,778 and 4,997,745, for example 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-2-triazine, 2-phenyl-4,6-bis(trichloromethyl)triazine, 2,4,6-tris(trichloromethyl)triazine, and 2-methyl-4,6-bis(trichloromethyl)triazine.

[0033] The aforementioned acid-generating agent is present in the imageable ultraviolet light-sensitive composition at an amount of 0.5-25%, preferably at least 1% and at most including 20%, based on the total solids of the ultraviolet light-sensitive composition or the dry weight of the coated imageable layer.

[0034] Free radical initiators: The free radical initiator used in this invention exhibits one or more absorption bands in the UV-violet light range, and at least one of these bands extends into the visible range of the electromagnetic spectrum shown, or has a shoulder or one or more other secondary bands in the visible range. Examples include one or more of carbonyl compounds, coumarins, anthraquinones, organoboron compounds, oxime esters, or phosphine oxides.

[0035] 3-Ketocoumarins and polycarboxylic acid co-initiators for UV and visible light activation, such as aniline-N,N-diacetic acid and second co-initiators, as described in U.S. Patent 5,942,372; cyanine dyes and co-initiators having a carboxylic acid group connected via a methylene group to an N, O, or S group directly linked to an aromatic ring, as described in U.S. Patent 5,368,990. Suitable free radical initiators include, for example, benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 2,4-dihydroxybenzophenone, michidone, α,α-diethoxyacetophenone, α-hydroxyalkylacetophenone, α-aminealkylacetophenone, diphenylacetophenone, α,α-dimethoxy-α-phenylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-methoxy-1,2-diphenylacetophenone, aniline-N,N-diacetic acid, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-l-[4-(methylthio)phenyl-2-morpholinylprop-l-one, 2,4-diethylthioxanthrone, 1 1-Chloro-4-propoxythioxanthones, thiopropoxythioxanthones, isopropylthioxanthones, 2-chlorothioxanthones, aromatic phosphine oxides, bisbenzoylphenylphosphine oxide, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 3-benzoyl-7-methoxycoumarin, coumarinone 93, diphenylethanol ketone, alkyl-substituted anthraquinones, tetrabutylammonium triphenyl(n-butyl)borate, tetraethylammonium triphenyl(n-butyl)borate, diphenyliodonium tetraphenylborate, bis(substituted phenyl)iodonium tetraphenylborate, triphenylsulfonium triphenyl(n-butyl)borate, and the borates described in U.S. Patent 11,242,360. In addition, commercially available products include BAPO, CPTX, DEAP, Darocure 1173, Darocure 184, IHT-PI 4265, IHT-PI 659, IHT-PI ITX, IHT-PI 910, IHT-PIBP, Irgacure 369, Irgacure 907, MBF, OXE-1, OXE-2, PDO, Quantacure DMB, TEPO, TPO, TPO-L, UV-651, FP5041, and P3B.

[0036] The aforementioned initiator is present in the imageable ultraviolet light-sensitive composition at an amount of 0.5-25%, preferably at least 1% and at most including 20%, based on the total solids of the ultraviolet light-sensitive composition or the dry weight of the coated imageable layer.

[0037] Coloring dyes: The coloring dyes involved in this invention refer to certain substances that can produce color when bound to protons, such as compounds with structural groups such as lactone, lactam, sulopentalide, fluorescein, spiroisobenzofuran, spiroxazine, and spiropyran. When these structural groups come into contact with electron-accepting (proton- or Lewis acid) compounds, the structure of these groups rapidly undergoes ring-opening or cleavage, resulting in color production.

[0038] Examples of such coloring dyes include 3-(1,2-dimethyl-3-indolyl)-3-[4-diethylamino-2-methylphenyl]phthalide, 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methyl-1H-indol-3-yl)phthalide, 3,3-bis[2-[4-(dimethylamino)phenyl]-2-(4-methoxyphenyl)vinyl]-4,5,6,7-tetrachlorophthalide, and 3-(4-dimethylaminophenyl) 3-(4-Diethylamino-2-tolyl)-6-dimethylaminophthalinol, 3-(4-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalinol, 3-(4-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalinol, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalinol, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalinol, 3,3-bis(9-ethylcarbazole-3-yl)-6-dimethylaminophthalinol, 3-(4-diethylaminophenyl)-3-(1,2-dimethylindol-3-yl)-6-dimethylaminophthalinol, 3-(4-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)-5-dimethylaminophthalinol, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalinol, 3-(4-dimethylaminophenyl)-3-(2-methylindol-3-yl)-6-dimethylaminophthalinol, 3-(4-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)-5-dimethylaminophthalinol, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalinol, 3-(4-dimethylaminophenyl)-3- ... 3,3-bis[1,1-bis(4-dimethylaminophenyl)vinyl-2-yl]-4,5,6,7-tetrachlorophthalolide, 3,3-bis[1,1-bis(4-pyrrolidinephenyl)vinyl-2-yl]-4,5,6,7-tetrachlorophthalolide, 3,3-bis[1,1-bis(4-pyrrolidinephenyl)vinyl-2-yl]-4,5,6,7-tetrabromophthalolide, 3,3-bis[1-(4-pyrrolidinephenyl)-1-(4-methoxyphenyl)vinyl-2-yl]-4,5,6,7-tetrachlorophthalolide, 3-[1,1-bis(1-ethyl-2-methylindole-3-yl] [1,1-[ ...

[0039] 3,3-Bis(1-ethyl-2-methyl-1H-indol-3-yl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-methyl-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-n-propoxycarbonylamino-4-di-n-propanophenyl)-3 -(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(2-methylamino-4-di-n-propanophenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(2-methyl-4-di-n-hexanephenyl)-3-(1-n-octyl-2-methylindole-3-yl)-4,7-diazaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(1-n-octyl-2-methylindole-3-yl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide.

[0040] 3,6-Dimethoxyfluorescein, 3-Dimethylamino-7-methoxyfluorescein, 3-Diethylamino-6-methoxyfluorescein, 3-Diethylamino-7-methoxyfluorescein, 3-Diethylamino-7-chlorofluorescein, 3-Diethylamino-6-methyl-7-chlorofluorescein, 3-Diethylamino-6,7-dimethylfluorescein, 3-N-hexyl-N-n-butylamino-7-methylfluorescein, 3-Diethylamino- 7-Dibenzylamine fluorescein, 3-Diethylamino-7-octane fluorescein, 3-Diethylamino-7-di-n-hexane fluorescein, 3-Diethylamino-7-phenylamine fluorescein, 3-Diethylamino-7-(2'-fluorophenylamino) fluorescein, 3-Diethylamino-7-(2'-chlorophenylamino) fluorescein, 3-Diethylamino-7-(3'-chlorophenylamino) fluorescein, 3-Diethylamino-7-(2',3'-Dichlorophenylamino)fluorescein, 3-diethylamino-7-(3'-trifluoromethylphenylamino)fluorescein, 3-di-n-butylamino-7-(2'-fluorophenylamino)fluorescein, 3-di-n-butylamino-7-(2'-chlorophenylamino)fluorescein, 3-N-isopentyl-N-ethylamino-7-(2'-chlorophenylamino)fluorescein, 2'-(dibenzylamino)-6'-(diethylamino)fluorescein, 2-(2-4-dimethylamino)-3-methyl-6-diethylaminofluorescein, 2-bromo-3-methyl-6-di-n-butylaminofluorescein, 3-N-n-hexyl-N-ethylamino-7-( 2'-Chlorophenylamino) fluorescein, 3-diethylamino-6-chloro-7-phenylamino) fluorescein, 3-di-n-butylamino-6-chloro-7-phenylamino) fluorescein, 3-diethylamino-6-methoxy-7-phenylamino) fluorescein, 3-di-n-butylamino-6-ethoxy-7-phenylamino) fluorescein, 3-pyrrolidine-6-methyl-7-phenylamino) fluorescein, 3-hydropyridyl-6-methyl-7-phenylamino) fluorescein, 3-morpholino-6-methyl-7-phenylamino) fluorescein, 3-dimethylamino-6-methyl-7-phenylamino) fluorescein, 3-diethylamino-6-methyl-7-phenylamino) fluorescein, 3-di-n-butyl ... 3-Methyl-7-phenylamine fluorescein, 3-di-n-pentanamino-6-methyl-7-phenylamine fluorescein, 3-N-ethyl-N-methylamino-6-methyl-7-phenylamine fluorescein, 3-N-n-propyl-N-methylamino-6-methyl-7-phenylamine fluorescein, 3-N-n-propyl-N-ethylamino-6-methyl-7-phenylamine fluorescein, 3-N-n-butyl-N-methylamino-6-methyl-7-phenylamine fluorescein, 3-N-n-butyl-N-ethylamino-6-methyl-7-phenylamine fluorescein, 3-N-n-butyl-N-methylamino-6-methyl-7-phenylamine fluorescein, 3-N-isobutyl-N-methylamino-6-methyl-7-phenylamine fluorescein, 3-N-isobutyl-N-ethyl ... 3-N-Isopentyl-N-ethylamino-6-methyl-7-phenylamine fluorescein, 3-N-n-hexyl-N-methylamino-6-methyl-7-phenylamine fluorescein, 3-N-cyclohexyl-N-ethylamino-6-methyl-7-phenylamine fluorescein, 3-N-cyclohexyl-N-n-propylamino-6-methyl-7-phenylamine fluorescein, 3-N-cyclohexyl-N-n-butyl-6-methyl-7-phenylamine fluorescein, 3-N-cyclohexyl-N-n-hexylamino-6-methyl-7-phenylamine fluorescein, 3-N-cyclohexyl-N-n-octylamino-6-methyl-7-phenylamine fluorescein.

[0041] 6'-(diethylamino)-2'-[[3-(trifluoromethyl)phenyl]amino]-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 6'-(dipentylamino)-3'-methyl-2'-(phenylamino)-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 6'-(diethylamino)-3'-methyl-2'-(octylamino)-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 3'-chloro-6'-(dibutylamino)-2'-(phenylamino)-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3- Ketones, 6'-(isobutylethylamino)-3'-methyl-2'-phenylamino-spiro[isobenzofuran-1(3H), 9'-[9H]oxanthracene]-3-one, diethylamino)-1-yl5-29-dimethyl-spiro[isobenzofuran-1(3H), 9'-[9H]oxanthracene]-3-one, 6'-(dibutylamino)-3'-methyl-2'-(phenylamino)-spiro[isobenzofuran-1(3H), 9'-[9H]oxanthracene]-3-one, 6-diethylamino-2-[(dimethylphenyl)amino-3-methyl-spiro[isobenzofuran-1(3H), 9'-[9H]oxanthracene]-3-one, 3,5',6'-tris(diethylamino ... 3',6'-bis(ethylamino)-2',7'-dimethyl-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 6'-[ethyl(4-methylphenyl)amino]-2'-methyl-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 2'-[cyclohexyl(benzyl)amino]-6'-(diethylamino)-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 3'-N,N-dibenzylamino-6'-N,N-diethylamino ...benzylamino-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 3'-N,N-dibenzyl Benzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 2'-(N-methyl-N-phenyl)amino-6'-(N-ethyl-N-(4-tolyl))amino-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 6'-[ethyl(4-methylphenyl)amino]-3'-methyl-2'-(phenylamino)-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one, 6'-[ethyl(3-methylbutyl)amino]-3'-methyl-2'-(phenylamino))-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one.

[0042] Rhodamine-B-phenylamino lactone, Rhodamine-(4-nitrophenylamino) lactone, Rhodamine-B-(4-chlorophenylamino)amide, 3,7-bis(diethylamino)-10-benzoylpyrazine, benzoyl colorless methylene blue, 4-nitrobenzoyl methylene blue; benzyl colorless methylene blue, 7-[4-(diethylamino)-2-(hexyloxy)phenyl]-7-(1-ethyl-2-methyl-1H-indol-3-yl)furano[3,4-b]pyridin-5(7H)-one, 7-[4-(diethylamino)-2-methyl] [3,4-b]-7-(1-ethyl-2-methyl-1H-indol-3-yl)-furano[3,4-b]pyridine-5(7H)-one, 3-methyl-spiro-dinaphthopiperan, 3-ethyl-spiro-dinaphthopiperan, 3-phenyl-spiro-dinaphthopiperan, 3-benzyl-spiro-dinaphthopiperan, 3-methyl-naphtho-(3-methoxybenzo)spiropipeperan, 4,4-bis-dimethylaminobenzopropanol benzyl ether, N-halophenyl-leuco-auramine, N-2,4,5-trichlorophenyl-leuco-auramine.

[0043] Color dyes can also be selected from commercially available products, such as ATP, BLACK15, BLACK100, BLACK305, BLACK400, BLACK500, BLACK-XV, BLMB, Blue63, Blue203, Blue220, BLUE520, ETAC, GN2, GN169, GREEN300, GREEN-DCF, H-1046, H-2114, H-3035, H-7001, S-205, TH-107, and Vermilion B2.

[0044] The aforementioned coloring dye is present in the imageable composition in an amount of 0.5-20% by weight, preferably at least 1% by weight and at most including 15% by weight, based on the total solids of the UV-sensitive composition or the dry weight of the coated imageable layer. From a visibility point of view, green, blue, or black are preferred as the hue after color development by the coloring dye.

[0045] Adhesive: The binder of the present invention is a carbon-containing polymer with a main chain, and any one or more of the binder polymers known in the art for use in the photosensitive layer of a negative lithographic printing plate precursor can be used without limitation.

[0046] Useful polymeric binders can be homogeneous, i.e., dissolved in coating solvents, or can exist as discrete particles and include, but are not limited to, acrylic acid, methacrylic acid, acrylates, polymers derived from methacrylates, polyvinyl acetals, phenolic resins, polymers derived from styrene and its derivatives, acrylonitrile, methacrylonitrile, N-substituted cyclic imides, or maleic anhydride, such as those described in European Patent 1,182,033 (cited above) and U.S. Patent 6,309,792 (cited above), U.S. Patent 6,569,603 (cited above), and U.S. Patent 6,893,797 (Munnelly et al.). Also, there are vinylcarbazole polymers described in U.S. Patent 7,175,949 (Tao et al.).

[0047] On the other hand, useful polymer binders can also be particulate polymers distributed (typically uniformly) throughout the imageable layer. These polymers have an average particle size of 10-10000 nm (typically 20-800 nm) in diameter. Typically, this polymer binder is solid at room temperature and is usually a non-elastic thermoplastic. The polymer binder contains both hydrophilic and hydrophobic regions, which is considered important for enhancing the difference between exposed and unexposed areas by promoting development ability; the presence of these discrete particles tends to promote the development ability of unexposed areas. Specific examples of polymer binders in this embodiment are described in U.S. Patent 6,899,994 (stated above), WO2009 / 030279 (Andriessen et al.), U.S. Patent 7,261,998 (Hayashi et al.), U.S. Patent 7,659,046 (Munnelly et al.), and European Patent 1,614,540 (Vermeersch et al.). The typical average molecular weight of the polymers used as adhesives is 2,000-500,000, preferably 5,000-100,000. The total amount of all adhesive polymers used is typically 10-70% by weight, preferably 10-55% by weight, relative to the total weight of the non-volatile components of the infrared-sensitive composition.

[0048] In addition, the imageable layer described in this invention may also include, in conventional amounts, various additives such as surfactants, background coloring dyes, adhesion promoters, polymerization inhibitors, antioxidants or combinations thereof, or any other additives commonly used in offset printing technology.

[0049] The imageable layer of the present invention is formed by preparing a coating solution by dissolving or dispersing each of the above-mentioned essential components in a solvent and then coating the coating solution. Solvents that can be used include, for example, dichloroethane, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propane acetate, dimethoxyethane, methyl lactate, ethyl lactate, N,N-dimethylacetamide, N,N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, cyclohexane, γ-butyrolactone, tetrahydrofuran, dioxolane, dioxane, toluene, and water, but the invention should not be construed as limited thereto. These solvents can be used alone or as mixtures. The solids content concentration of the coating solution is preferably 1-50% by weight.

[0050] The imageable layer can be applied over the base layer using known methods such as extrusion coating, bar coating, spin coating, roller coating, blade coating, spray coating, or solution immersion.

[0051] The amount (solid content) of the imageable layer formed on the support after the coating liquid is coated and dried can vary depending on the desired purpose, but is preferably 0.6 g / m³. 2 -1.6g / m 2 Within the range, it is particularly preferred to be within 0.8 g / m 2 ~1.4g / m 2 Within a certain range, to obtain more desirable sensitivity and better film-forming properties of the imaging layer.

[0052] d. Protective layer: The lithographic printing plate precursor of the present invention preferably has a protective layer (sometimes also called an outer coating) covering the imageable layer. In addition to overcoming the function of oxygen barrier that inhibits the reaction that hinders image formation, the protective layer also has the function of preventing the imageable layer from being scratched by impact during the production of the printing plate precursor or during the plate making process.

[0053] Regarding protective layers with such properties, for example, as described in U.S. Patent 3,458,311, water-soluble polyvinyl acetate or polyvinyl alcohol or modified polyvinyl alcohol can be appropriately selected as low-oxygen permeability polymers used in protective layers.

[0054] Among the above-mentioned water-soluble polymers, polyvinyl acetate with a degree of hydrolysis of 85% or more is preferred, more preferably 95% or more. There is no particular upper limit to the degree of hydrolysis, as long as it is below 100%.

[0055] The coating solvent can be appropriately selected according to the polymer used, and when using water-soluble polymers, distilled water or purified water is preferred as the solvent. The coating solution of the protective layer thus prepared is applied over the imageable layer and then dried to form the protective layer.

[0056] The protective layer can be applied over the imageable layer using known methods such as extrusion coating, bar coating, spin coating, blade coating, air knife coating, gravure coating, roller coating, spray coating, or solution immersion.

[0057] The coating amount (solid content) of the protective layer is preferably 0.3 g / m³. 2 -1.3g / m 2 Within the range, it is particularly preferred to be within 0.4 g / m 2 ~0.8g / m 2 Within the range.

[0058] B. Plate-making methods and printing methods for lithographic printing: The plate-making feature of the lithographic printing plate precursor in this invention is that it has the following negative image forming capability: the exposed area of ​​the image is solidified to form the image portion, and the unexposed area is removed by the developing process, thereby forming the non-image portion.

[0059] The method for making and printing a lithographic printing plate precursor according to the present invention preferably includes: a step of exposing the lithographic printing plate precursor according to the present invention into an image (also called an "exposure step"), then supplying at least one imageable layer selected from printing ink and water-based components to a printing press to remove non-image portions to make a lithographic printing plate (also called an "on-machine development step"), and a step of printing using the obtained lithographic printing plate (also called a "printing step").

[0060] The preferred embodiments of each step of the plate-making method and printing method of the lithographic printing plate precursor involved in this invention will be described below.

[0061] Exposure process: The exposure process of the lithographic printing plate precursor involved in this invention involves exposing the lithographic printing plate precursor into an image to form exposed and unexposed portions. Preferably, the lithographic printing plate precursor involved in this invention is exposed using a transparent film having line images, halftone images, etc., or exposed into an image using laser scanning based on digital data.

[0062] In embodiments of the present invention, the laser used to expose the offset printing plate precursor of the present invention can be a carbon arc lamp, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, a halogen lamp, a helium-cadmium laser, an argon ion laser, an FD-YAG laser, a helium-neon laser, or a semiconductor laser (350nm-450nm) to expose the photosensitive layer. Currently, commercially available digital plate-making machines use high-performance lasers or laser diodes with an emission wavelength of 405nm. The imaging device can be configured as a flat-panel recorder or a drum recorder, wherein the imaging element is mounted on the inner or outer cylindrical surface of the drum. Suitable exposure equipment includes, for example, CRON and AMSKY's CTCP / UV imaging machines, BasysPrint's Xeikon UV device, Liischer's Xpose UV machine, and ECRM's Nautilius device. Depending on the photosensitivity of the radiation-sensitive layer, 10mJ / cm² is generally used. 2 Up to 300mJ / cm 2 Optimal 20mJ / cm 2 Up to 150 mJ / cm 2 The energy is used for this imaging.

[0063] In the case of on-machine development, the lithographic printing plate precursor can be mounted on the printing press, and the image can be exposed on the printing press.

[0064] On-machine developing process: The method for making a lithographic printing plate precursor involved in this invention also includes an on-machine development process. In the on-machine development method, the lithographic printing plate precursor exposed to the image is preferably processed on a printing press to remove the imageable layer of the non-image portion using oil-based ink and water-based components to make a lithographic printing plate.

[0065] To explain the on-machine developing process more specifically, after image exposure, the lithographic printing plate precursor is directly mounted onto the printing press, followed by the supply of oil-based inks and water-based components for printing. In the initial stage of printing, the non-image section is dissolved or dispersed and removed by one or both of the supplied oil-based inks and water-based components, exposing a hydrophilic surface in that area. Conversely, in the exposed section, the imageable layer cured by exposure forms an oil-based ink receiving area with an oleophilic surface.

[0066] The ink initially supplied to the printing plate can be either oil-based or water-based; however, to prevent contamination of the image-forming layer removed by the water-based component, oil-based ink is preferred initially. Thus, the lithographic printing plate precursor is developed on the printing press and directly used for multi-sheet printing. Conventional lithographic printing inks and dampening solutions are preferably used as the oil-based ink and water-based component.

[0067] Printing process: The lithographic printing method involved in this invention includes a printing process of supplying printing ink to a lithographic printing plate and printing a recording medium.

[0068] There are no particular restrictions on the type of printing ink; various known inks can be used as needed. Furthermore, oil-based inks or ultraviolet-curing inks (UV inks) are preferred as printing inks.

[0069] Furthermore, dampening solution can be supplied as needed during the aforementioned printing process.

[0070] Regarding the above printing process, it can be carried out immediately following the above on-machine developing process without stopping the printing press.

[0071] Example The present invention will now be described in more detail with reference to specific embodiments, but the invention should not be construed as limited thereto. Unless otherwise specified below, the common chemicals and solvents used in the examples are available from Aldrich Chemical Company (Milwaukee, WI).

[0072] The following are some of the special components and materials used in the examples below: Binder A is a polymer dispersion containing 90% by weight styrene and 10% by weight polyethylene glycol methyl ether methacrylate in propanol / water, with a solid content of 23.7%.

[0073] Binder B is a polymer dispersion containing 30% by weight styrene, 60% by weight acrylonitrile and 10% by weight polyethylene glycol methyl ether methacrylate in propanol / water, with a solid content of 26%.

[0074] Binder C is a solution of a polymer containing 60% by weight methyl methacrylate, 20% by weight styrene and 20% by weight methacrylic acid in ethylene glycol methyl ether, with a concentration of 24.8%.

[0075] Binder D is a polymer containing 94% by weight methyl methacrylate and 6% by weight methacrylic acid.

[0076] Adhesive E is a polymer solution containing 90% by weight allyl methacrylate and 10% by weight polyethylene glycol methyl ether methacrylate in 2-butanone, with a solid content of 10%.

[0077] The reaction product of free radical polymer compound A: 1,6-hexamethylene diisocyanate with hydroxyethyl acrylate and pentaerythritol triacrylate (oligomeric solution in 2-butanone, solid content 80%).

[0078] The reaction product of free radical polymerizable compound B: 1,6-hexamethylene diisocyanate with hydroxyethyl acrylate and pentaerythritol triacrylate (polymer solution in dimethylformamide, solid content 60%).

[0079] Sartomer 355 is a multifunctional acrylic monomer available from Sartomer Co., Inc.

[0080] PF5041 is a free radical initiator and is available from HRI.

[0081] YK-341 and BYK-330 silicone surface additives are available from BYK GmbH, Germany.

[0082] Example a Preparation of the aluminum substrate: A 0.3 mm thick aluminum substrate was immersed in an aqueous solution containing 8 g / L sodium hydroxide for 15 seconds at 45°C to remove oil, and then rinsed clean with water. Subsequently, it was subjected to alternating current at 25°C and 50 A / dm² in an aqueous solution containing 9 g / L hydrochloric acid, 20 g / L acetic acid, and 3.5 g / L aluminum ions. 2 The aluminum material was then subjected to electrochemical roughening at a current density of [value missing]. Subsequently, it was etched for 12 seconds at 35°C with an aqueous solution containing 1.8 g / L sodium hydroxide, and then rinsed with water. This was followed by etching at 28°C and 35 A / dm [value missing]. 2 The aluminum material was anodized in an aqueous solution containing 180 g / L sulfuric acid at a given current density, followed by washing with water. It was then post-treated at 60°C for 20 seconds with a solution containing 120 g / L sodium dihydrogen phosphate and 0.8 g / L sodium fluoride, and rinsed with deionized water. Finally, it was dried at 120°C for later use. The resulting substrate is characterized by a surface roughness of an average surface roughness Ra of 0.55 μm and an average oxide weight of approximately 2.73 g / m². 2 .

[0083] Examples b1-b5 Preparation of the substrate coating: Different concentrations of polyvinylphosphonic acid aqueous solutions were coated onto the substrate of Example a using a wire rod coating method, and then dried in an oven at 120°C for 1.5 minutes to obtain the following substrates with various polyvinylphosphonic acid coverage rates. Example c1 The imageable layer described in this example (selected from Embodiment 1 of CN115352177B) comprises the following weight percentages: Example c2 The imageable layer described in this example comprises the following weight percentages: Example c3 The imageable layer described in this example is the chromogenic dye 6'-(diethylamino)-3'-methyl-2'-(octylamino)-spiro[isobenzofuran-1(3H),9'-[9H]oxanthracene]-3-one removed from the composition of Example c2.

[0084] Example d The protective layer described in this example comprises the following weight percentages: The following comparative examples 1–4 and 1–3 illustrate the test scheme and evaluation results of the present invention for improving the thermal stability of lithographic printing plate precursors.

[0085] Comparative Example 1 The components of Example c1 were dissolved in a mixed solvent of 20.2 g of 1-methoxy-2-propanol, 9.5 g of water, and 16.5 g of 2-butanone. The solution was then applied to the aluminum substrate of Example a using a spin-coating method and dried in an oven at 110°C for 2 minutes, resulting in an imageable layer coverage of 1.2 g / m². 2 Subsequently, the components from Example d were dissolved in 97 grams of water, and the solution was coated onto the imageable layer using a wire rod coating method. The mixture was then dried again in an oven at 110°C for 2 minutes, yielding a double-coated layer with a total weight of approximately 1.9 g / m². 2 The lithographic printing plate precursor was then wrapped in a waterproof packaging bag and placed in a 50°C oven for accelerated aging for 5 days. After that, it was taken out and placed at room temperature for testing.

[0086] The aforementioned accelerated-aging lithographic printing plate precursor was subjected to graphic scanning exposure on a CRON UVP-820G+ CTcP plate-making machine under conditions of a drum rotation speed of 1050 rpm and a laser power of 45 mW. Then, this exposed lithographic printing plate precursor was directly mounted on a Heidelberg Printmas GTO 52-4 printing press. A combination of lithographic printing ink and dampening solution was used to remove the unexposed areas of the radiation-sensitive imageable layer. After printing more than 50 sheets, the background became dirty and the image became unclear.

[0087] Comparative Example 2 The components of Example c2 were dissolved in a mixed solvent of 20.67 g of 1-methoxy-2-propanol, 4.1 g of water, and 16.1 g of 2-butanone. The solution was then applied to the aluminum substrate of Example a using a spin-coating method and dried in an oven at 110°C for 2 minutes, resulting in an imageable layer coverage of 1.2 g / m². 2Subsequently, the components from Example d were dissolved in 97 grams of water, and the solution was coated onto the imageable layer using a wire rod coating method. The mixture was then dried again in an oven at 110°C for 2 minutes, yielding a double-coated layer with a total weight of approximately 1.9 g / m². 2 The lithographic printing plate precursor was then wrapped in a waterproof packaging bag and placed in a 50°C oven for accelerated aging for 5 days. After that, it was taken out and placed at room temperature for testing.

[0088] The aforementioned accelerated-aging lithographic printing plate precursor was subjected to graphic scanning exposure on a CRON UVP-820G+ CTcP plate-making machine under conditions of a drum rotation speed of 1050 rpm and a laser power of 45 mW. Then, this exposed lithographic printing plate precursor was directly mounted on a Heidelberg Printmas GTO 52-4 printing press. A combination of lithographic printing ink and dampening solution was used to remove the unexposed areas of the radiation-sensitive imageable layer. After printing more than 50 sheets, the background became dirty and the image became unclear.

[0089] Example 1 The components of Example c2 were dissolved in a mixed solvent of 20.67 g of 1-methoxy-2-propanol, 4.1 g of water, and 16.1 g of 2-butanone. The solution was then applied to the aluminum substrate of Example b1 using a spin coating method and dried in an oven at 110°C for 2 minutes, resulting in an imageable layer coverage of 1.2 g / m². 2 Subsequently, the components from Example d were dissolved in 97 grams of water, and the solution was coated onto the imageable layer using a wire rod coating method. The mixture was then dried again in an oven at 110°C for 2 minutes, yielding a double-coated layer with a total weight of approximately 1.9 g / m². 2 The lithographic printing plate precursor was then wrapped in a waterproof packaging bag and placed in a 50°C oven for accelerated aging for 5 days. After that, it was taken out and placed at room temperature for testing.

[0090] The accelerated-aging lithographic printing plate precursor was subjected to graphic scanning exposure on a CRON UVP-820G+ CTcP plate-making machine with a drum rotation speed of 1050 rpm and a laser power of 45 mW. Then, this exposed lithographic printing plate precursor was directly mounted on a Heidelberg Printmas GTO52-4 printing press. Using a combination of lithographic printing ink and dampening solution, the unexposed areas of the radiation-sensitive imageable layer were removed on the machine. After printing more than 50 sheets, the background did not become dirty and the image was clear.

[0091] Examples 2-3 and Comparative Examples 3-4 Similar to the preparation method of Example 1, the components in Example c2 were coated onto the aluminum substrates of b2, b3, b4 and b5 respectively. The remaining plate making and testing methods were all the same as those in Example 1. The test results are listed in Table 1.

[0092] Table 1. Test results of thermal stability of offset printing plate precursor Table 1 shows the results of Examples 1-3, which improve the thermal storage stability of the lithographic printing plate precursor, within the scope of this invention. The following comparative examples 5-6 and Example 4 illustrate the test scheme and evaluation results of this invention for improving the color difference (color difference) between the exposed and unexposed areas of the lithographic printing plate precursor after exposure. Color difference refers to the visual perception difference between two colors. The quantitative evaluation of color difference is achieved through mathematical models and measurement tools; commonly used formulas include CIELAB, CIE94, and CIEDE2000. The main measurement tools are colorimeters and spectrophotometers. Color difference is represented by ΔE; the larger the value, the more significant the difference.

[0093] Comparative Example 5 The components of Example c3 were dissolved in a mixed solvent of 20.67 g of 1-methoxy-2-propanol, 4.1 g of water, and 16.1 g of 2-butanone. The solution was then applied to the aluminum substrate of Example a using a spin-coating method and dried in an oven at 110°C for 2 minutes, resulting in an imageable layer coverage of 1.2 g / m². 2 Subsequently, the components from Example d were dissolved in 97 grams of water, and the solution was coated onto the imageable layer using a wire rod coating method. The mixture was then dried again in an oven at 110°C for 2 minutes, yielding a double-coated layer with a total weight of approximately 1.9 g / m². 2 The precursor for offset printing plates.

[0094] The offset printing plate precursor was exposed by graphic scanning on a CRON UVP-820G+ CTcP plate-making machine with a drum rotation speed of 1050 rpm and a laser power of 45 mW. The color difference ΔE between the exposed and unexposed areas was measured to be 0.46 using an X-Rite eXact spectrophotometer.

[0095] Comparative Example 6 The components of Example c2 were dissolved in a mixed solvent of 20.67 g of 1-methoxy-2-propanol, 4.1 g of water, and 16.1 g of 2-butanone. The solution was then applied to the aluminum substrate of Example a using a spin-coating method and dried in an oven at 110°C for 2 minutes, resulting in an imageable layer coverage of 1.2 g / m². 2Subsequently, the components from Example d were dissolved in 97 grams of water, and the solution was coated onto the imageable layer using a wire rod coating method. The mixture was then dried again in an oven at 110°C for 2 minutes, yielding a double-coated layer with a total weight of approximately 1.9 g / m². 2 The precursor for offset printing plates.

[0096] The offset printing plate precursor was exposed by graphic scanning on a CRON UVP-820G+ CTcP plate-making machine with a drum rotation speed of 1050 rpm and a laser power of 45 mW. The color difference ΔE value between the exposed and unexposed areas was measured to be 1.95 using an X-Rite eXact spectrophotometer.

[0097] Example 4 The components from Example c2 were dissolved in a mixed solvent of 20.67 g of 1-methoxy-2-propanol, 4.1 g of water, and 16.1 g of 2-butanone. The solution was then applied to the aluminum substrate of Example b2 using a spin-coating method and dried in an oven at 110°C for 2 minutes, resulting in an imageable layer coverage of 1.2 g / m². 2 Subsequently, the components from Example d were dissolved in 97 grams of water, and the solution was coated onto the imageable layer using a wire rod coating method. The mixture was then dried again in an oven at 110°C for 2 minutes, yielding a double-coated layer with a total weight of approximately 1.9 g / m². 2 The precursor for offset printing plates.

[0098] The offset printing plate precursor was exposed by graphic scanning on a CRON UVP-820G+ CTcP plate-making machine with a drum rotation speed of 1050 rpm and a laser power of 45 mW. The color difference ΔE between the exposed and unexposed areas was measured to be 3.17 using an X-Rite eXact spectrophotometer.

[0099] Comparative results of Examples 5-6 and Example 4 show that: in the absence of colorant, the color difference ΔE value between the exposed and unexposed areas of the offset printing plate precursor of Example 5 is only 0.46 after exposure, making it almost impossible to distinguish the exposed image with the naked eye; although the color difference ΔE value of the offset printing plate precursor with added colorant (Comparative Example 6) is increased to 1.95 after exposure, it is still difficult to distinguish the details of the exposed image with the naked eye; while the color difference ΔE value of the offset printing plate precursor constructed using the present invention (Example 4) is improved to 3.17 after exposure, and the observation of the details of the exposed image basically meets the requirements.

[0100] The results of all the above embodiments and comparative embodiments show that the design of the multi-coated ultraviolet radiation sensitive lithographic printing plate precursor on a specific hydrophilic aluminum substrate based on the present invention not only improves the poor shelf life and thermal stability of the printing plate precursor, but also improves the effect of color difference in the printed image after exposure.

Claims

1. A multi-coated ultraviolet radiation-sensitive offset printing plate precursor, characterized in that... Include: (a) Subbase; (b) A base coat covering the substrate; (c) An imageable layer covering the undercoat; (d) A protective layer covering the imageable layer; The substrate is an aluminum sheet substrate that has undergone electrochemical roughening, sulfuric acid anodizing, and hydrophilic treatment with sodium dihydrogen phosphate / sodium fluoride sealing solution. The base coating is a coating containing polyvinylphosphonic acid; the imaging layer is an ultraviolet radiation sensitive coating containing 25-65 parts of a free radical polymerizable compound, 0.5-20 parts of an acid-generating agent, 0.5-25 parts of a free radical initiator, 0.5-20 parts of a coloring dye, and 10-70 parts of a binder; and the protective layer is a coating containing highly hydrolyzable polyvinyl acetate.

2. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The average roughness R of the aluminum sheet substrate surface layer a The alumina thickness is 0.40-0.80 μm, and the surface alumina weight is 1.5-4.0 g / m². 2 The solute composition of the sodium dihydrogen phosphate / sodium fluoride sealing solution is 90-99.8 parts sodium dihydrogen phosphate and 0.2-10 parts sodium fluoride.

3. The offset printing plate precursor according to claim 1, characterized in that: The coverage of the base coating is 10-30 mg / m². 2 .

4. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The coverage of the imageable layer is 0.6-1.6 g / m². 2 .

5. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The coverage of the protective layer is 0.3-1.3 g / m². 2 .

6. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The free radical polymerizable compound is one or more of the following: acrylate, methacrylate, urethane acrylate, urethane methacrylate, epoxide acrylate or epoxide methacrylate, acrylate of polyol, methacrylate of polyol, polyurethane acrylate, polyurethane methacrylate, polyether acrylate, and polyether methacrylate.

7. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The acid-producing agent is one or more of onium salts and trihalomethyl compounds.

8. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The free radical initiator has one or more absorption peaks or absorption bands in the 350nm-450nm UV-violet light range, and can be selected from one or more of carbonyl compounds, coumarins, anthraquinones, organoboron compounds, oxime esters or phosphine oxides.

9. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The coloring dye is one or more compounds containing lactones, lactams, sulopentalides, or spiropyrans.

10. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The adhesive is a polymer derived from at least one of the following: acrylic acid, methacrylic acid, acrylate, methacrylate, acrylamide, methacrylamide, styrene and styrene derivatives, acrylonitrile, methacrylonitrile, N-substituted cyclic imide, and maleic anhydride, which constitute repeating units.

11. The multi-coated ultraviolet radiation sensitive offset printing plate precursor according to claim 1, characterized in that: The degree of hydrolysis of the polyvinyl acetate is 80% to 99.9%.

12. A method for on-machine development of a multi-coated ultraviolet radiation-sensitive lithographic printing plate precursor, characterized in that, It includes the following steps: (a) Patterning exposure of the multi-coated ultraviolet radiation sensitive lithographic printing plate precursor as described in claims 1-11, thereby forming exposed and unexposed areas with obvious color differences; (b) Using dampening solution and / or lithographic printing ink, the exposed lithographic printing plate precursor is developed directly on the printing press.

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