Polymerization inhibition system and photopolymerization type lithographic printing plate

Abstract

The invention belongs to a photopolymerization type photosensitive coating lithographic printing plate formed on a supporting body, and relates to a polymerization inhibition system and a photopolymerization type lithographic printing plate, and the polymerization inhibition system is composed of a nitroxide free radical compound and a metal salt. By adopting the polymerization inhibition system, the photopolymerization type lithographic printing plate has better storage stability and higher photosensitive speed, so that the photopolymerization type lithographic printing plate disclosed by the invention has longer service life and more sensitive photosensitive property.

Description

Technical Field

[0001] The present invention belongs to a photopolymerizable photosensitive coating lithographic printing plate formed on a support, relates to an inhibitor system and a photopolymerizable lithographic printing plate, and specifically relates to a photopolymerizable lithographic printing plate that can be directly plated by laser. Background Art

[0002] Lithographic printing technology is one of the important foundations of the modern printing industry and is widely used in the printing of books, magazines, posters, packaging materials, etc. This technology is based on the principle that water and oil do not mix. It uses a smooth plate surface and forms graphic and non-graphic parts on the plate surface through chemical treatment to achieve printing. The above-mentioned smooth plate surface that can achieve imaging is called a lithographic printing plate.

[0003] The so-called photopolymerization lithographic printing plate refers to a lithographic printing plate that can achieve imaging by photopolymerization. Photopolymerization refers to a method of polymerizing monomers under the action of light. Photoinitiated polymerization is divided into direct photoinitiated polymerization and photosensitive polymerization. In the former, under the action of light, the photoinitiator generates active seeds (free radicals or cations) in the excited state to initiate monomer polymerization; in the latter, the photosensitizer first absorbs light and then reacts with the photoinitiator to generate active seeds to initiate monomer polymerization. Therefore, according to the absorption spectrum of the photosensitizer, the required photosensitivity range can be achieved, such as infrared light 830nm, green light 532nm, blue light 488nm and blue-violet light 405nm.

[0004] For the photopolymerizable lithographic printing plate that can be imaged by laser, the area exposed by laser undergoes polymerization reaction and solidifies, and changes from soluble to insoluble in the developer to form the image area; the unexposed area is removed after development processing to form the blank area of ​​the printing plate. During exposure, the sensitizing dye (photosensitizer) in the photopolymerizable photosensitive coating absorbs energy, and the molecules transition from the ground state to the excited state. Through energy transfer or electron transfer, the initiator decomposes to produce free radicals, which trigger the polymerization reaction of the active substances (compounds containing double bonds) in the photopolymerizable photosensitive coating.

[0005] At present, a certain amount of polymerization inhibitor is usually added to the photopolymerization photosensitive coating of the photopolymerization lithographic printing plate to prevent the self-polymerization phenomenon that may occur in the photopolymerization plate. This is mainly because the photosensitive resin in the plate may also undergo a certain degree of polymerization reaction due to factors such as temperature, humidity, and chemical impurities in the absence of light. This spontaneous polymerization may lead to a decrease in the performance of the plate, such as reducing its storage stability and affecting image quality.

[0006] However, the addition of polymerization inhibitors will also have a certain effect on the photosensitive speed. Since the polymerization inhibitor slows down the rate of polymerization, this may lead to a decrease in the photosensitive speed. This is because the photosensitive speed is closely related to the rate of polymerization, and the slowing down of the polymerization rate may cause the photosensitive imaging process to take longer to complete. Summary of the invention

[0007] The present invention provides an inhibitor system and a photopolymerizable lithographic printing plate, aiming to solve the problem that the storage stability and photosensitivity of the above-mentioned photopolymerizable lithographic printing plate cannot be taken into account due to the use of an inhibitor.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows: an inhibition system, which is composed of a nitroxide free radical compound and a metal salt.

[0009] As an improved technical solution of the present application, the nitroxide free radical compound is selected from one of 2,2,6,6-tetramethylpiperidine-1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical, 4-oxygen-2,2,6,6-tetramethylpiperidine-1-oxyl free radical and 4-carbonyl-2,2,6,6-tetramethylpiperidine-1-oxyl free radical or multiple thereof in any mass ratio.

[0010] As an improved technical solution of the present application, the metal salt is selected from one or more of copper sulfate, copper acetate, copper nitrate, copper chloride, copper naphthenate, copper benzoate, copper stearate, ferrous sulfate, ferrous chloride, ferrous nitrate, ferrous acetate, titanium trichloride, N-nitrosophenylhydroxylamine aluminum salt and sodium sulfate in any mass ratio.

[0011] As an improved technical solution of the present application, the molar ratio of the nitroxide free radical compound to the metal salt is ≥2.

[0012] Another object of the present application is to provide a photopolymerizable lithographic printing plate, which includes a support, a photopolymerizable photosensitive coating on the support, and a water-soluble protective layer attached to the photopolymerizable photosensitive coating, characterized in that the photopolymerizable photosensitive coating contains the aforementioned inhibitor system.

[0013] As an improved technical solution of the present application, the photopolymerizable photosensitive coating comprises an ethylenically unsaturated compound, an initiator system, a colorant, and an inhibitor system, and the weight percentage of each component is:

[0014] Ethylenically unsaturated compounds: 70-90 parts

[0015] Initiator system: 8-15 parts

[0016] Colorant: 3-10 parts

[0017] Inhibition system: 0.01-0.1 parts.

[0018] As an improved technical solution of the present application, the inhibitor system accounts for 0.01%-0.1% of the weight of the photopolymerizable photosensitive coating after drying.

[0019] As an improved technical solution of the present application, the photopolymerizable photosensitive coating has a weight after drying of 0.1 g / m 2 -10g / m 2 .

[0020] As an improved technical solution of the present application, the water-soluble protective layer comprises the following substances in parts by weight:

[0021] Water-soluble polymer compound: 90-99 parts

[0022] Surfactant and other additives: 0.1-2 parts.

[0023] As an improved technical solution of the present application, the water-soluble protective layer is 0.5-10g / m2 by weight after drying. 2 .

[0024] Beneficial Effects

[0025] Different inhibitors have different properties. Inhibitors terminate the chain growth reaction by reacting with free radicals to form stable or unstable compounds. Some of their effects are reversible, that is, under certain conditions, they can be "released" to release free radicals, allowing the polymerization reaction to continue; some are irreversible, that is, once they react with free radicals, they cannot release free radicals again, so the polymerization reaction cannot be restarted.

[0026] The polymerization inhibition system of the present application adopts two polymerization inhibitors, nitroxide free radical compounds and metal salts, for compound use, wherein the nitroxide free radical compounds combine with the active free radicals in the photopolymerization type photosensitive coating to form a stable nitroxide free radical complex, thereby inhibiting the polymerization reaction. The specific mechanism of this combination to form a stable complex mainly involves the stability of the nitroxide free radical and the regulation of the active free radical. The nitroxide free radical (such as TEMPO) generates a "dormant species" by reacting with the chain free radical, and then releases the free radical again under appropriate conditions (such as heating), thereby continuing to participate in the polymerization reaction, showing a certain reversibility. The metal salt polymerization inhibitor used in the polymerization inhibition system has a variable valence characteristic and can accept or provide electrons. When the free radical contacts the metal salt, the unpaired electrons in the free radical will be transferred to the metal salt to form a stable metal complex or metal oxide. This process leads to the disappearance of the free radical, thereby preventing the polymerization reaction from continuing, and this effect is usually irreversible.

[0027] In photopolymerizable lithographic printing plates, the large-scale use of irreversible inhibitors can effectively inhibit spontaneous polymerization during the storage of the plates and extend the shelf life, but it will slow down the photopolymerization rate of the plates; the use of reversible inhibitors has little effect on the photosensitivity of the plates, because the photopolymerizable plates pass through a heating treatment unit during the platemaking process, causing the inhibitors to release free radicals again.

[0028] Through research and testing of different polymerization inhibitors, the present invention provides a polymerization inhibition system composed of nitroxide free radical compounds and metal salts. When the weight of the polymerization inhibitor system added to the photosensitive coating is 0.01-0.1 parts, preferably 0.04-0.08 parts, and the molar ratio of the nitroxide free radical compound to the metal salt is ≥2, the storage stability of the plate material is greatly improved, and the photosensitive speed is faster. Therefore, the photopolymerizable lithographic printing plate of the present invention has a longer life and more sensitive photosensitivity. DETAILED DESCRIPTION

[0029] 1. Inhibition system

[0030] A polymerization inhibition system is composed of a nitroxide free radical compound and a metal salt.

[0031] As an improved technical solution of the present application, the nitroxide free radical compound is selected from one of 2,2,6,6-tetramethylpiperidine-1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical, 4-oxygen-2,2,6,6-tetramethylpiperidine-1-oxyl free radical and 4-carbonyl-2,2,6,6-tetramethylpiperidine-1-oxyl free radical or multiple thereof in any mass ratio.

[0032] As an improved technical solution of the present application, the metal salt is selected from one or more of copper sulfate, copper acetate, copper nitrate, copper chloride, copper naphthenate, copper benzoate, copper stearate, ferrous sulfate, ferrous chloride, ferrous nitrate, ferrous acetate, titanium trichloride, N-nitrosophenylhydroxylamine aluminum salt and sodium sulfate in any mass ratio.

[0033] As an improved technical solution of the present application, the molar ratio of the nitroxide free radical compound to the metal salt is ≥2.

[0034] In photopolymerization systems, the selection of inhibitors is crucial because they can effectively prevent premature polymerization reactions, thereby extending the storage time of the material and maintaining its performance. As photopolymerization inhibitors, phenols such as hydroquinone, p-methoxyphenol (MEHQ), tert-butylhydroquinone, and 2,6-di-tert-butyl-p-cresol can be selected. Quinones such as benzoquinone, tert-butylhydroquinone, p-benzoquinone, and hydroquinone can be selected. Sulfide compounds such as phenothiazine and distearyl thiodipropionate can be selected. Nitrogen oxide free radical compounds such as 2,2,6,6-tetramethylpiperidin-1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical, 4-oxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical and 4-carbonyl-2,2,6,6-tetramethylpiperidin-1-oxyl free radical can be selected. Metal salts such as copper sulfate, copper acetate, copper nitrate, copper chloride, copper naphthenate, copper benzoate, copper stearate, ferrous sulfate, ferrous chloride, ferrous nitrate, ferrous acetate, titanium trichloride, N-nitrosophenylhydroxylamine aluminum salt, and sodium sulfate can be used.

[0035] As an improved technical solution of the present application, a composite inhibitor system of nitroxide free radical compounds and metal salts is innovatively adopted. Experimental verification shows that when the molar ratio of the two is ≥2, the obtained lithographic printing plate has a longer life and more sensitive photosensitivity.

[0036] 2. Photopolymerization lithographic printing plate

[0037] The photopolymerizable lithographic printing plate comprises a support, a photopolymerizable photosensitive coating on the support, and a water-soluble protective layer attached to the photopolymerizable photosensitive coating; the photopolymerizable photosensitive coating contains the aforementioned inhibitor system.

[0038] 1. Support

[0039] The support used in the present application can be dimensionally stable aluminum or its alloy. The thickness of the aluminum plate is preferably about 0.1 mm to 0.6 mm. In addition, a plastic film or paper laminated or vapor-deposited with aluminum or aluminum alloy can also be used.

[0040] When the support is an aluminum plate, various treatments are usually applied to its surface according to the purpose. As a general treatment method, the aluminum surface is first cleaned by degreasing or electrolytic grinding and decontamination of the aluminum plate. Then, a mechanical surface roughening treatment or / and an electrochemical surface roughening treatment are applied to give the aluminum plate surface fine concave and convex. In addition, chemical etching treatment and decontamination treatment are sometimes added. In order to improve the wear resistance of the aluminum plate surface, anodizing treatment is applied, and the aluminum surface is subjected to hydrophilization treatment or / and sealing treatment as required.

[0041] 2. Formation of photopolymerizable photosensitive coating

[0042] A photopolymerizable photosensitive coating layer is formed by coating a photopolymerizable photosensitive composition on a support and drying the coating.

[0043] The photopolymerizable photosensitive coating comprises an ethylenically unsaturated compound, an initiator system, a colorant, and an inhibitor system, and the weight percentage of each component is:

[0044] Ethylenically unsaturated compounds: 70-90 parts

[0045] Initiator system: 8-15 parts

[0046] Colorant: 3-10 parts

[0047] Inhibition system: 0.01-0.1 parts.

[0048] (1) Ethylenically unsaturated compounds

[0049] The ethylenically unsaturated compound refers to a compound having an ethylenically unsaturated bond that undergoes addition polymerization, crosslinking, and curing by the action of a photopolymerization initiator when the photopolymerizable photosensitive composition is irradiated with active light.

[0050] The ethylenically unsaturated compound can be arbitrarily selected from compounds having at least one, preferably two or more, terminal ethylenically unsaturated bonds, and can have a chemical form such as a monomer, a prepolymer (i.e., a dimer, a trimer, and an oligomer), or a copolymer.

[0051] Examples of the monomer and copolymer thereof include acrylic acid esters, methacrylic acid esters, itaconates, crotonates, isocrotonates, maleates, and amide compounds.

[0052] Examples of the acrylate include ethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane tri(acryloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri(acryloxyethyl) isocyanurate, polyester acrylate oligomers, polyurethane acrylate oligomers, and the like.

[0053] Examples of the methacrylate include 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, hexanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol pentamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, di[p-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]dimethylmethane, and di[p-(methacryloyloxyethoxy)phenyl]dimethylmethane.

[0054] Examples of itaconate include ethylene glycol diitaconate, propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanediol diitaconate, 1,4-butanediol diitaconate, pentaerythritol diitaconate, and sorbitol tetraitaconate.

[0055] Examples of the crotonate include ethylene glycol dicrotonate, 1,4-butanediol dicrotonate, pentaerythritol dicrotonate, and sorbitol tetracrotonate.

[0056] The isocrotonate includes ethylene glycol diisocrotonate, pentaerythritol diisocrotonate, sorbitol tetraisocrotonate and the like.

[0057] The maleate includes ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, sorbitol tetramaleate and the like.

[0058] Examples of the amide compounds include methylenebis-acrylamide, methylenebis-methacrylamide, 1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide, diethylenetriamine triacrylamide, xylylenebisacrylamide, and xylylenebismethacrylamide.

[0059] (2) Initiation system

[0060] Among them, as the initiator system contained in the photopolymerizable photosensitive coating of the photosensitive lithographic printing plate in the present application, various photoinitiators known in the prior art can be appropriately selected according to the wavelength of the light source used, or a combined system of two or more photoinitiators can be used. Specific examples are listed below, but are not limited to these.

[0061] For example, it may be a cationic dye / borate system, a merocyanine dye / titacenene system, a carbazole type dye / titacenene system, etc. In the present application, a titanocene compound is particularly preferably used because of its excellent sensitivity.

[0062] As the titanocene compound, various substances can be used. More specifically, dicyclopentadienyl-Ti-dichloride, dicyclopentadienyl-Ti-diphenyl, dicyclopentadienyl-Ti-di-2,3,4,5,6-pentafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,5,6-tetrafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,4,6-tri ...4,5,6-pentafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,5,6-tetrafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,5,6-tetrafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,6-trifluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,5,6-pentafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,5,6-pentafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,5,6-tetrafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,6-trifluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,5,6-pentafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,3,4,5,6-pentafluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2, -2,6-difluorobenzene-1-yl, dicyclopentadienyl-Ti-di-2,4-difluorobenzene-1-yl, di-methylcyclopentadienyl-Ti-di-2,3,4,5,6-pentafluorobenzene-1-yl, di-methylcyclopentadienyl-Ti-di-2,6-difluorobenzene-1-yl, dicyclopentenyl-Ti-di-2,6-difluoro-3-(pyrrol-1-yl)-benzene-1-yl, and the like.

[0063] In addition, it is known that the photoinitiator ability can be further improved by adding hydrogen donating compounds such as thiol compounds such as 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, and 2-mercaptobenzoxazole, and amine compounds such as N-phenylglycine and N,N-dialkylaminoaromatic alkyl esters as co-initiators to the above-mentioned photoinitiator as needed.

[0064] (3) Colorants

[0065] For the purpose of coloring the photopolymerizable photosensitive coating, a colorant may be added. As the colorant, pigments such as phthalocyanine pigments, azo pigments, carbon black, titanium oxide, etc. may be used, and dyes such as anthraquinone dyes, cyanine dyes, azo dyes, ethyl violet, crystal violet, etc. may also be used.

[0066] (4) Inhibition system

[0067] The above-mentioned polymerization inhibitor system is used to prevent unnecessary polymerization of the polymerizable ethylenically unsaturated compound during the preparation or storage of the photosensitive composition.

[0068] The use process is as follows: when the photopolymerizable photosensitive coating composition is coated on the support aluminum plate, the composition needs to be dissolved in various organic solvents for use. The solvents used here include acetone, methyl ethyl ketone, cyclohexane, ethyl acetate, diethylene chloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 3-methoxypropanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, methyl lactate, ethyl lactate, etc. These solvents can be used alone or mixed in any weight ratio.

[0069] In order to improve the coating appearance, a surfactant may be added to the photopolymerizable composition of the photopolymerizable photosensitive coating layer of the photosensitive planographic printing plate of the present invention.

[0070] In addition, the coating amount of the photopolymerizable photosensitive coating composition is about 0.1 g / m 2 -10g / m 2 The range of is appropriate. More preferably, it is 0.3-5g / m 2 More preferably, it is 0.5-3g / m 2 .

[0071] The photopolymerizable photosensitive composition used for the photopolymerizable photosensitive coating is dissolved and dispersed at a solid content concentration of 2-50% by weight, applied to the support aluminum plate and dried. The coating amount of the layer of the photopolymerizable photosensitive composition (photopolymerizable photosensitive coating) applied to the support aluminum plate varies depending on the application, but is generally preferably 0.1-10 g / m after drying. 2 .

[0072] Coating method:

[0073] As a method for coating the photosensitive composition, a coating rod method, an extrusion coater method, a slide bead coater method, etc. can be used, but it is not limited to these.

[0074] 3. Formation of water-soluble protective coating

[0075] The water-soluble protective layer comprises the following substances in parts by weight:

[0076] Water-soluble polymer compound: 90-99 parts

[0077] Surfactant and other additives: 0.1-2 parts.

[0078] As water-soluble polymers containing hydrogen-bonding groups contained in the protective coating, polyvinyl alcohol and its partial esters, ethers and acetals, or copolymers thereof containing a substantial amount of unsubstituted vinyl alcohol units to give them the necessary water solubility, can be cited. As polyvinyl alcohol, polyvinyl alcohol that is 71-100% hydrolyzed and has a degree of polymerization in the range of 300-2400 can be cited. Specifically, they may be: PVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST, PVA-HC, PVA-203, PVA-204, PVA-205, PVA-2107, PVA-2177, PVA-220, PVA-224, PVA-217EE, PVA-220, PVA-2247PVA-217EE, PVA-217EPVA-220E, PVA-224E, PVA-405, PVA-420, PVA-613, L-8, etc. Examples of the above copolymers include 88-100% hydrolyzed polyvinyl acetate chloroacetate or propionate, polyvinyl formal and polyvinyl acetal, and copolymers thereof. Other useful polymers include polyvinyl pyrrolidone, gelatin and gum arabic, which can be used alone or in combination.

[0079] The protective coating layer may further contain known additives such as a surfactant for improving coating properties and a water-soluble plasticizer for improving film-forming properties.

[0080] As water-soluble plasticizers, for example, propionamide, cyclohexanediol, glycerol, sorbitol, etc. can be included. In addition, water-soluble (meth) acrylic polymers can be added. The coating amount is about 0.1-15 g / m2 based on the weight after drying. 2 The range of is appropriate. More preferably, it is 1.0g-5.0g / m 2 .

[0081] Coating method:

[0082] As a coating method of the protective layer, a coating rod method, an extrusion coater method, a slide bead coater method, etc. can be used, but it is not limited to these.

[0083] 4. Exposure and Development Processing

[0084] The prepared photopolymerizable lithographic printing plate precursor is subjected to image exposure to the photopolymerizable photosensitive coating using, for example, 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 ion laser, an FD-YAG laser, a helium-neon laser, a semiconductor laser (350nm-600nm), a solid laser emitting infrared rays, and a semiconductor laser (760nm-1200nm). After image exposure using these conventionally known active rays, an image can be formed on the surface of the aluminum plate support by development treatment.

[0085] Between image exposure and development, a heating process may be performed at 50°C to 150°C for 1 second to 5 minutes in order to increase the curing rate of the photopolymerizable photosensitive coating.

[0086] In addition, as described above, it is known to provide a protective coating with oxygen barrier properties on the photopolymerizable photosensitive coating of the photosensitive lithographic printing plate of the present invention, and use a developer to simultaneously remove the protective coating and the unexposed portion of the photopolymerizable photosensitive coating; or to first remove the protective coating with water or warm water, and then remove the unexposed portion of the photopolymerizable photosensitive coating by development.

[0087] V. Comparative Example (D1-6), Example (S1-12)

[0088] 1. Preparation of photopolymerizable lithographic printing plates

[0089] The aluminum plate (support) with a thickness of 0.30 mm was rolled into a coil (coiled) and fixed to the feeder. The aluminum plate continuously fed from the feeder was immersed in 10% sodium hydroxide at 70°C for 60 seconds in the surface treatment part, etched, washed with running water, neutralized and washed with 20% HNO3, and washed with water. A sinusoidal alternating waveform current was used under the condition of VA = 12.7 V, and 300 coulombs / dm in a 1% nitric acid aqueous solution was used. 2 The surface roughening treatment was carried out by electrolysis at the anode of 10000 ℃. The surface roughness was measured and found to be 0.6 um.

[0090] Then, the surface was immersed in a 30% H2S04 aqueous solution at 55°C for 2 minutes to remove dirt. Then, a cathode was placed on the surface of the sand mesh in a 20% H2S04 aqueous solution at 33°C and a current density of 5A / dm 2 Under 50 seconds of anodizing, the thickness is 2.7g / m 2 In addition, the anodized film on the back side at this time is about 0.5 g / m 2 , about 1.0g / m at the end 2 .

[0091] The following hydrophilic layer coating composition was mixed and stirred at 30° C. After about 5 minutes, heat was observed, and after reacting for 60 minutes, the contents were transferred to another container, and 10,000 parts by weight of methanol was further added to prepare a primer coating.

[0092] (Liquid composition for primer)

[0093]

[0094] The liquid coating was applied to the treated aluminum plate to a concentration of 0.1 g / m 2 , drying until the aluminum temperature reaches 70°C, and then cooling until the aluminum temperature reaches below 50°C.

[0095] On the primer layer thus obtained, a photopolymerizable photosensitive composition of the following composition was applied so that the dry coating weight became 1.6 g / m 2 , drying is performed until the aluminum temperature reaches 100°C, and then cooling is performed until the aluminum temperature reaches below 50°C.

[0096] (Photopolymerizable photosensitive layer coating liquid composition)

[0097] Table 1: Comparative Examples of Photopolymerizable Photosensitive Coating Compositions D1-6.

[0098]

[0099] Table 2: Comparative Examples of Photopolymerizable Photosensitive Coating Compositions S1-12.

[0100]

[0101]

[0102] In the above Table 1 and Table 2:

[0103] A: Propylene glycol methyl ether (Dow Chemical, PM), solvent

[0104] B: Methyl ethyl ketone (Qixiang Tengda Chemical, MEK), solvent

[0105] C: Polyurethane acrylate (SARTOMER, CN970A60), film-forming resin

[0106] D: Acrylate oligomer (SARTOMER, CN549), prepolymer

[0107] E: Pentaerythritol tetramethacrylate (SARTOMER, SR531), multifunctional monomer

[0108] F: Photopolymerization initiator (CIBA, titanium ocene compound), initiator

[0109] G: 2-Mercaptobenzimidazole (Shanghai Ethyl Chemical, MBT), co-initiator

[0110] H: Phthalocyanine pigment dispersion (Sanyo Pigment, S1293), pigment

[0111] I: BYK-330 (BYK, Germany), leveling agent

[0112] J: 2,2,6,6-tetramethylpiperidin-1-oxyl radical (Nanjing Huikang Biotechnology Co., Ltd.) (molecular weight: 141.25), inhibitor

[0113] K: Copper naphthenate (Nanjing Shude High-tech Materials Technology Co., Ltd.) (molecular weight: 405.8), inhibitor

[0114] L: 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl radical (Nanjing Huikang Biotechnology Co., Ltd.) (molecular weight 157.25), inhibitor

[0115] M: N-nitrosophenylhydroxylamine aluminum salt (Nanjing Bermuda Biotechnology Co., Ltd.) (molecular weight: 438.3), inhibitor

[0116] A protective coating having the following composition was applied on the applied photopolymerizable photosensitive coating so that the dry coating weight was 2.0 g / m 2 , blow dry air at a temperature of 120°C at a wind speed of 8m / s in a drying oven for 5 minutes, and then cool until the aluminum temperature reaches below 50°C.

[0117] (Protective layer coating liquid composition)

[0118] Polyvinyl alcohol (PVA-105 from Kuraray) 20 parts by weight

[0119] Polyvinyl alcohol (PVA-203 from Kuraray) 20 parts by weight

[0120] Polyvinyl pyrrolidone (Shanghai Reagent Company, Sinopharm Group) 2 parts by weight

[0121] Surfactant (Shanghai Reagent Company, Sinopharm Group, 0P-15) 0.5 parts by weight

[0122] 600 parts by weight of distilled water

[0123] 2. Test Method

[0124] (Photographic speed measurement)

[0125] A simulated grayscale scale (such as Ugra 1982 or Stouffer 21-level scale, with a transmission density difference of 0.15 between two adjacent levels) was pasted on the plate, and the entire plate was exposed using an ECRM MOKO 8 platemaker (laser wavelength 405nm, resolution 2540dpi) with different laser energy values ​​set (to produce a solid 175 lines / inch file). The exposed plate was developed using a Gulongyan VPP85 photopolymer plate developer using developer PVD (produced by Lucky Huaguang Printing Technology Co., Ltd.), and the development conditions were as follows:

[0126] Layout preheating temperature: 110℃

[0127] Developer temperature: 26°C

[0128] Development time: 17 seconds

[0129] Taking Stouffer 21-level gray scale 3-level solid 6-level clean or Ugra 1982 gray scale 2-level solid 5-level clean as the appropriate exposure, the corresponding laser energy value is expressed as the photosensitive speed. The larger the value, the greater the laser energy required and the slower the photosensitive speed of the plate; the smaller the value, the smaller the laser energy required and the faster the photosensitive speed.

[0130] For photopolymerized lithographic printing plates, the faster the photosensitivity, the wider the laser energy range that can be adapted in the corresponding platemaking process. The photosensitivity is 45uj / cm 2 Below, it can meet the energy of all plate-making machines on the market, and the sensitivity is 45uj / cm 2 The above will no longer be applicable to some platemaking machines with aging lasers.

[0131] (Storage stability determination)

[0132] Cut the prepared unexposed lithographic printing plate into several strips of 3cm*10cm, package them in opaque sealed bags, put them in a 50℃ oven for forced aging, take them out after several hours, and then use PVD developer (produced by Lucky Huaguang Printing Technology Co., Ltd.), heat or cool the developer to 26℃, drop it onto the plate at an ambient temperature of 26℃, rinse it with clean water after 10 seconds, and then observe under a microscope whether the coating is rinsed clean.

[0133] The storage stability is expressed by the number of forced aging hours when the bottom is left (not washed clean). The larger the value, the less likely the photopolymerization type photosensitive coating of the plate is to self-polymerize, the better the storage stability and the longer the life of the plate; the smaller the value, the easier the photopolymerization type photosensitive coating of the plate is to self-polymerize, the worse the storage stability and the shorter the life of the plate.

[0134] Under normal circumstances, the faster the photosensitivity of a photopolymer lithographic printing plate, the worse its storage stability and the shorter its retention time during forced aging at 50 degrees. Based on experimental experience in plate production and testing, a photopolymer lithographic printing plate with a shelf life of one year must meet the requirement of not leaving any bottom during forced aging for 96 hours.

[0135] The following table compares the storage stability and photosensitive speed of the plate material implementing the present invention (Example S1-12) and the plate material not implementing the present invention (Comparative Example D1-5):

[0136] Table 3: Storage stability (retention time) and photosensitive speed results of comparative examples D1-6

[0137]

[0138] Table 4: Storage stability (retention time) and photosensitive speed results of Examples S1-12

[0139]

[0140] The following conclusions can be drawn from the results in Table 3 and Table 4:

[0141] The introduction of inhibitors into the photopolymerizable photosensitive coating can effectively improve the storage stability and prolong the retention time (see the results obtained in D1-3, D4-6, and S1-4).

[0142] The introduction of inhibitors into the photopolymerizable photosensitive coating leads to an unfavorable slowing down of the photosensitive speed (see the results obtained in D1-3, D4-6, S1-4, S5-8, and S9-12).

[0143] When the molar concentration ratio of L (nitrogen oxide free radical inhibitor) to M (metal salt inhibitor) is ≥2, it is unexpectedly found that the retention time is unexpectedly extended (see S5, S9, S10, S11), among which S5 has good storage stability (≥95h) and the photosensitivity can be maintained at a faster level (≤45uj / cm2).

Claims

1. An inhibition system, characterized in that: The polymerization inhibition system consists of nitroxide free radical compounds and metal salts.

2. The polymerization inhibition system according to claim 1, characterized in that: The nitroxide free radical compound is selected from one of 2,2,6,6-tetramethylpiperidine-1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical, 4-oxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical and 4-carbonyl-2,2,6,6-tetramethylpiperidine-1-oxyl free radical or multiple compounds in any mass ratio.

3. The polymerization inhibition system according to claim 1, characterized in that: The metal salt is selected from one or more of copper sulfate, copper acetate, copper nitrate, copper chloride, copper naphthenate, copper benzoate, copper stearate, ferrous sulfate, ferrous chloride, ferrous nitrate, ferrous acetate, titanium trichloride, N-nitrosophenylhydroxylamine aluminum salt and sodium sulfate in any mass ratio.

4. The polymerization inhibition system according to claim 1, characterized in that: The molar ratio of the nitroxide free radical compound to the metal salt is ≥2.

5. A photopolymerizable lithographic printing plate, comprising a support, a photopolymerizable photosensitive coating on the support, and a water-soluble protective layer attached to the photopolymerizable photosensitive coating, characterized in that: The photopolymerizable photosensitive coating comprises the inhibitor system according to any one of claims 1 to 3.

6. A photopolymerizable lithographic printing plate according to claim 5, characterized in that: The photopolymerizable photosensitive coating comprises an ethylenically unsaturated compound, an initiator system, a colorant, and an inhibitor system, and the weight percentage of each component is: Ethylenically unsaturated compounds: 70-90 parts Initiator system: 8-15 parts Colorant: 3-10 parts Inhibition system: 0.01-0.1 parts.

7. A photopolymerizable lithographic printing plate according to claim 5, characterized in that: The inhibitor system accounts for 0.01% to 0.1% of the weight of the photopolymerizable photosensitive coating after drying.

8. The photopolymerizable lithographic printing plate according to claim 5, characterized in that: The photopolymerizable photosensitive coating has a weight after drying of 0.1 g / m 2 -10g / m 2 .

9. The photopolymerizable lithographic printing plate according to claim 5, characterized in that: The water-soluble protective layer comprises the following substances in parts by weight: Water-soluble polymer compound: 90-99 parts Surfactant and other auxiliary agents: 0.1-2 parts.

10. The photopolymerizable lithographic printing plate according to claim 5, characterized in that: The water-soluble protective layer has a weight after drying of 0.5-10 g / m 2 .

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