JPH0153450B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photosensitive lithographic printing plate, and more particularly to a diazo-based photosensitive lithographic printing plate that has good storage stability, improved printing durability, and developability. Diazo-based photosensitive compositions are generally used in the photosensitive layer of photosensitive lithographic printing plates (hereinafter referred to as PS plates). The diazo-based photosensitive material for the positive-working PS plate contains naphthoquinone diazide, and the diazo-based photosensitive material for the negative-working PS plate contains 4-diazodiphenylamine, 4-diazo-3-methoxydiphenylamine, and paraformaldehyde. Condensates (hereinafter referred to as diazo resins) are mainly used. By mixing this diazo resin with a polymer compound,
It is possible to make a long-lasting lithographic printing plate without lacquering, and it can be easily developed with an aqueous developer containing a surfactant, so it is used in large quantities as a photosensitive material for negative PS plates. Diazo resin is
The photosensitive layer of a negative PS plate is classified into the following types depending on the partner polymer compound that undergoes a photocrosslinking reaction. (1) A combination of a water-insoluble polymer compound with alcoholic hydroxyl groups and a water-insoluble diazo resin. As a water-insoluble polymer compound having an alcoholic hydroxyl group, epoxy resin
1167), 2-hydroxyalkyl methacrylate, acrylonitrile, methacrylate and
Multi-component acrylic copolymer consisting of methacrylic acid,
Polyvinyl formal resin, polyvinyl butyral resin, polyvinyl chlorobenzal resin,
Multi-component acrylic copolymer consisting of 2-hydroxy-3-phenoxypropyl acrylate, methyl methacrylate, hydroxypropyl methacrylate, acrylonitrile and methacrylic acid (JP-A-52-7364, JP-A-55-34929, JP-A-54- 88403, Japanese Unexamined Patent Publication No. 55-142332), etc. are known. (2) A combination of a water-insoluble polymer compound with a phenolic hydroxyl group and a water-insoluble diazo resin. Examples of polymeric compounds having phenolic hydroxyl groups include phenolic resin (Japanese Patent Publication No. 47-1167), N
(4-hydroxyphenyl)methacrylamide,
Multi-component acrylic copolymers consisting of acrylonitrile, methyl methacrylate and methacrylic acid (JP-A-54-98614, JP-A-56-107234) are known. (3) Combinations of other water-insoluble polymer compounds and water-insoluble diazo resins. Other water-insoluble polymer compounds include polyamide, polystyrene, polyester, polyacetate, polyurethane, polyvinyl acetate (Japanese Patent Publication No. 47-1167, Japanese Patent Publication No. 56-9697), N-vinylpyrrolidone, acrylonitrile, and methyl methacrylate. Acrylic copolymers (Japanese Patent Laid-Open No. 54-27802), multi-component acrylic copolymers consisting of methyl methacrylate, acrylonitrile and methacrylic acid (Japanese Patent Laid-Open No. 56-4144), and the like are known. Combinations that belong to (2) and (3) above have a lower photocrosslinking density with the diazo compound than combinations that belong to (1) above, so they have weaker solvent resistance. As a result, the developability with an aqueous developer containing a surfactant deteriorates, and there are many problems in producing a good negative PS plate. The water-insoluble diazo resin used for negative PS plates is a combination of diazo resin and organic sulfonic acids such as para-toluenesulfonic acid, dodecylbenzenesulfonic acid, 2-methoxy-4-hydroxybenzophenone-5-sulfonic acid, or salts thereof. reaction product with
Also known are reaction products with inorganic acids such as hydroborofluoric acid, thiocyanic acid, and hexafluorophosphoric acid, or their salts (Japanese Patent Publication No. 39-17602, Japanese Patent Publication No. 42-5364, US Pat. No. 4,093,465). The photosensitive composition of these diazo-based negative PS plates is applied to a hydrophilized support such as paper, chromium, or aluminum to make a PS plate. When applied to a plate, the adhesion is too good, so if it has been applied for several months or has been stored at high temperature and high humidity, when it is exposed and developed, the unexposed areas will be eluted and the ink will stain. This phenomenon can be seen. In order to solve these problems, diazo negative type
Oxalic acid (Special Publication No. 1984-8460) is used in photosensitive compositions for PS plates.
It is known that ink stains on negative PS plates after development can be eliminated over time by mixing phosphorous acid (Japanese Unexamined Patent Publication No. 54-151023), or high-molecular organic acids (Japanese Unexamined Patent Publication No. 56-107238). However, it is still not enough. As a result of intensive research to solve the above problem, the present inventors formed a polymer film of polyacrylic acid or polymethacrylic acid with a film thickness of 0.5μ or less on an anodized aluminum plate, and A photosensitive layer consisting of a water-insoluble diazo resin and a polymer having an acid value of 10 to 100 containing a structural unit represented by the following general formula [] and 20% by weight or less of a structural unit represented by the following general formula []. It has been found that by laminating, a diazo-based negative PS plate with good stability over time and improved printing durability and developability can be obtained. (In each of the above formulas, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 10.) Anodized aluminum used in the present invention After graining the aluminum plate by brush polishing or electrolytic polishing, the plate is anodized in an anodizing bath of sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, or a mixed acid, and is further coated with silicate or zirconium fluoride. The pores are sealed with an aqueous salt solution. The polyacrylic acid or polymethacrylic acid used in the present invention preferably has an average molecular weight of 5,000 to 30,000, is well soluble in water, and almost insoluble in solvents. According to JP-A No. 56-107238, polyacrylic acid is added to the resin of a diazo negative photosensitive composition from 1 to 10%.
It has been reported that the storage stability of PS plates improves when 5% by weight is mixed in. However, since polyacrylic acid is almost insoluble in the solvents such as methyl cellosolve that make up the photosensitive solution, it is difficult to Polyacrylic acid is removed during the process. Therefore P.S.
Variations occur in the storage stability of the plates. Further, the water-insoluble diazo resin is less likely to decompose as the viscosity of the photosensitive liquid increases. Therefore, when applying a photosensitive solution to an aluminum plate sheet by sheet using a roll coater, the resin concentration of the photosensitive solution should be adjusted to 10 to
Adjustment to 15% or more is necessary to produce a PS plate with stable quality, and polyacrylic acid cannot be added and dissolved accordingly. In order to manufacture a PS plate with good storage stability by mixing polyacrylic acid into a photosensitive solution, a polymer compound that is easily soluble in water and methanol and a diazo photosensitive material are used, taking into account the solubility of polyacrylic acid. Must-have. If this photosensitive liquid composition is a storage-stable negative type,
Even if you get the PS version, there are problems with printing durability. The thickness of the polymer film of polyacrylic acid or polymethacrylic acid used in the undercoat layer of the present invention is preferably 0.5μ or less, and if it is 0.5μ or more, the adhesion between the photosensitive layer and the aluminum support will deteriorate during printing. , the image area may be missing in spots. The thickness of these polymer films varies depending on the type of water-insoluble diazo resin used, and is appropriately selected from the above-mentioned range. For example, when using a reaction product of diazo resin and hexafluorophosphate, the polymer film thickness is 0.1 to 0.2μ.
is preferred. When a reaction product of diazo resin and 2-methoxy-4-hydroxybenzophenone-5-sulfonic acid is used, the thickness is preferably 0.1 μ or less. The polymer used in the present invention undergoes an efficient photo-crosslinking reaction with the water-insoluble diazo resin to form a photosensitive film with good adhesion and water resistance and solvent resistance on an anodized aluminum plate. Further, the unexposed area can be easily developed with a weakly alkaline aqueous solution containing a surfactant. Known monomers forming the structural unit represented by the general formula [] include 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxy-3-methylphenoxypropyl acrylate, and corresponding methacrylates. It will be done. Also, general formula []
The monomers forming the structural unit represented by 2-
Hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, etc. are known. The monomers forming the structural units represented by the general formulas [] and [] are methyl (meth) in order to increase the water resistance and ink receptivity required for planographic printing plates.
Monomers such as acrylate, styrene, benzyl acrylate, α-cyanomethyl acrylate, and acrylonitrile are copolymerized as necessary, and acrylic acid, methacrylic Acid, unsaturated carboxylic acid such as maleic acid is copolymerized. The polymer compound containing the structural unit represented by the general formula [] can efficiently photocrosslink with the diazo resin, have strong adhesion to the anodized aluminum plate, and form a photosensitive layer with good abrasion resistance. Form.
However, the monomer forming the structural unit represented by the general formula [] is difficult to copolymerize with other acrylic monomers, and the polymerization solution tends to gel, but the structural unit represented by the general formula [] When a monomer that forms is present, it easily forms a copolymer with other monomers. The content of the structural unit represented by the general formula [] is
5 to 30% by weight, and if it exceeds 30% by weight, the adhesion to the anodized aluminum plate is too strong.
It becomes difficult to develop, and if it is less than 5% by weight, the mechanical strength of the image area will be insufficient. The content of the structural unit represented by the general formula [] is
20-50% by weight is preferred. If it is less than 20% by weight, it will be difficult to copolymerize with the monomer forming the structural unit represented by the general formula [], and if it is more than 50% by weight, it will be difficult to copolymerize with the monomer forming the structural unit represented by the general formula []. Since the adhesion with the coated aluminum plate decreases, the image area swells during development and the ink receptivity decreases. The acid value of the above polymer is preferably 10 to 100. If the acid value is less than 10, development with a slightly alkaline aqueous solution containing a surfactant will be slow, and even after development is completed, ink stains will easily occur. If the acid value is 100 or more, the oil sensitivity of the image area will be significantly reduced, making it unsuitable for use in the photosensitive layer of a lithographic printing plate. Further, the molecular weight of the polymer is preferably in the range of 50,000 to 150,000. The water-insoluble diazo resin used in the present invention includes organic sulfonate salts of diazo resins as described above,
and reaction products with inorganic acid salts can be used.
In particular, a reaction product of a diazo resin with a hexafluoro acid salt or a 2-methoxy-4-hydroxybenzophenone-5-sulfonate is preferred. Since these water-insoluble diazo resins are soluble in solvents such as methyl cellosolve, dimethylformamide, and ethylene dichloride, a mixed solvent of these is used as the solvent constituting the photosensitive liquid. Diazo negative type
In order to improve the storage stability of PS plates, oxalic acid, phosphorous acid, polymeric organic acids, etc., which were conventionally added to photosensitive solutions, are difficult to dissolve in these solvents, and a high viscosity photosensitive solution such as a roll coater is required. With this coating method, there were many pinholes and uneven coating on the coating surface, and there were also variations in storage stability between production lots. In this invention, since a polymer film of polyacrylic acid or polymethacrylic acid, which is completely soluble in water, is used as the undercoat layer, it is possible to prevent ink stains during development due to the resinization of some diazo resin during synthesis. Can be done. The content of the diazo compound is 5% relative to the polymer.
~20% by weight is preferred. Furthermore, if necessary, the performance of the PS plate can be improved by adding dyes, pigments, and fillers. When developing the negative PS plate of the present invention, anionic surfactants, benzyl alcohol,
Although it is possible to use a developer consisting of an aqueous solution containing a water-soluble sulfite and a water-soluble sulfite, for more efficient development, phenyl cellosolve and benzotriazoleamine addition salt described in JP-A-55-138740 and Preference is given to using a developer consisting of an aqueous solution containing a surfactant. The present invention will be explained in detail below with reference to Examples, but the present invention is not limited thereto. Example 1 Under a nitrogen stream, 0.3 g of azobisisobutyronitrile is added to 150 g of dioxane and heated to 80-85°C. 2-Hydroxy-
3-phenoxypropyl acrylate 15.5g, 2
- A mixture consisting of 41 g of hydroxyethyl methacrylate, 20.5 g of methyl methacrylate, 18 g of α-cyanomethyl acrylate, and 5 g of methacrylic acid was added dropwise for an hour or so, and after the addition was completed, 80 g of methacrylic acid was added.
Stir at ~85°C for 2 hours. After the reaction, the mixture is cooled, diluted with a mixture of dioxane and methanol, and then poured into a large amount of water with stirring to precipitate the copolymer. This polymer is redissolved in methyl cellosolve, purified by pouring it into water again, and vacuum dried to reduce the water content to 1% or less. The acid value of this multi-component acrylic copolymer was 28.6. After graining a 0.3 mm thick aluminum plate with a nylon brush, immerse it in 10% caustic soda water for 10 seconds and rinse with water. Furthermore, immerse it in 10% nitric acid water for 5 seconds,
After desmatting, I washed it with water. 20 pieces of this aluminum plate
% sulfuric acid at 2 A/dm ² for 3 minutes. After that, it was treated with 5% sodium silicate water at 70℃ for 30 seconds, washed with water, dried, and then processed using a Whaler with a 0.1% polyacrylic acid aqueous solution (using polyacrylic acid with a molecular weight of 8000).
was applied and dried at 60°C for 5 minutes. The polyacrylic acid film thickness was 0.08μ. A photosensitive solution having the following composition was applied to this anodized aluminum plate treated with polyacrylic acid using a Whaler, and dried at 85°C for 3 minutes.
A negative PS version (1) was obtained. On the other hand, for comparison, a comparative PS plate (2) was obtained by applying a photosensitive liquid on an anodized aluminum plate that had not been treated with polyacrylic acid in the same manner as described above. In both cases, the thickness of the photosensitive layer was 1.7 μm. Photosensitive liquid 1 Rx. Multi-component acrylic copolymer 5.0g Reaction product of diazo resin and hexafluorophosphate 0.5g Oil Blue #603 0.25g Methyl cellosolve 95.0g Dimethylformamide 10.0g (Diazo resin is a combination of diazo diphenylamine and , using a condensate with paraformaldehyde) The obtained negative PS plate (1) and comparative PS plate (2) were
It was exposed to light for 1 minute using a 1 kW ultra-high pressure mercury lamp at an intensity of 2.2 mW/cm ² , and developed with the following developer at 25° C. for 30 seconds to obtain a lithographic printing plate. Developer Rx. Phenyl cellosolve 12g Benzotriazole triethanolamine addition salt 3g Sodium isopropylnaphthalene sulfonate
6g water 250g To observe storage stability, temperature 40℃, temperature
The negative PS plate (1) of the present invention and the comparative PS plate (2) were stored in a 75% atmosphere, and compared with those exposed and developed immediately after manufacture, Kodak Step Tablets (Kodak Step Tablet) No. 2 was tested for increasing change in clear stage and scumming phenomenon of printing ink in non-image areas.

[Table] As is clear from Table 1, negative type according to the present invention
It can be seen that the PS version (1) has excellent storage stability.
In addition, we were able to print over 100,000 copies of the negative PS version (1). Example 2 Even if the water-insoluble diazo resin used in Example 1 was replaced with a reaction product of diazo resin with 2-methoxy-4-hydroxybenzophenone-5-sulfonic acid, the storage stability and printing durability were improved. It was found that the properties were as excellent as in Example 1.

Claims (1)

[Claims] 1. On an anodized aluminum plate, the film thickness is
A polymer film of polyacrylic acid or polymethacrylic acid of 0.5μ or less is formed, and a water-insoluble diazo resin and the following general formula [] The structural unit represented by and 50% by weight or less of the following general formula [] (In the above formula and inside, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or an alkyl group,
A photosensitive lithographic printing plate comprising a photosensitive layer made of a polymer having an acid value of 10 to 100 and containing a structural unit represented by (n is an integer of 1 to 10).