JPH0529103B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial application field The present invention relates to a composition for forming a surface layer of a lithographic printing plate material suitable for use in electrophotographic engraving, and more specifically, it relates to a composition for forming a surface layer of a lithographic printing plate material suitable for use in electrophotographic engraving. The present invention relates to a composition that is applied to the surface of a substrate to form a surface layer so as to have water film retention properties and form an electrostatic latent image. (b) Prior art and problems to be solved by the invention Conventionally, lithographic printing plate materials used in electrophotographic engraving have been provided with a zinc oxide photoconductive layer on the surface of a base material such as metal foil or paper. is used. This is generally referred to as master paper, and it forms an electrostatic latent image on a zinc oxide photoconductive layer, and then attaches lipophilic developing powder (toner) to the electrostatic latent image to form an image area. to form a lithographic printing plate. By the way, since the zinc oxide photoconductive layer is exposed in the non-image area, it is necessary to make this area hydrophilic to prevent printing ink from adhering to it. It is done by applying it to the area. However, after forming the image area, selectively applying a processing agent only to the non-image area is a troublesome task, and there is a risk that the processing agent will also be applied to the image area, making the image area hydrophilic as well. It was hot. Therefore, the inventors of the present invention conducted intensive studies to obtain a lithographic printing plate material that does not require hydrophilic treatment of non-image areas after the formation of image areas. discovered that it is possible to obtain a lithographic printing plate material that has both photoconductivity and photoconductivity.
This led to the present invention. (d) Means and action for solving the problems That is, the present invention relates to a composition for coating on a base material of a lithographic printing plate material, in which (a) a compound of the general formula RSi(OH) is added to an organic solvent; ) ₃ (wherein, R has 1 to 3 carbon atoms
alkyl group, gamma-macrolopropyl group, vinyl group, 3,3,3-trifluoropropyl group, gamma-glycidoxypropyl group, gamma-methacryloxypropyl group, gamma-mercaptopropyl group, and phenyl group. )
A partial condensate of silane triol represented by (b) polyvinyl alcohol with a degree of saponification of 30 to 60%, (c) a crosslinked product of alkali salt of polyacrylic acid, and (d) a photoconductive substance are dissolved. The present invention relates to a composition for forming a surface layer of a lithographic printing plate material, which is characterized in that it is formed by dispersing or dispersing the composition. Component (a) used in the present invention is a partial condensate of silane triol. Specific examples of silane triols are as follows. _CH3Si (OH) ₃ , _C2H5Si (OH) ₃ , _{C3H7Si (} OH) _{3 ,}
CH ₂ = CHSi(OH) ₃ , C ₆ H ₅ Si(OH) ₃ , (CH ₃ ) ₂
CHSi(OH) ₃ , _F3C- ( _CH2 ) _2Si (OH) ₃ ,C1( _CH2 )
_3Si (OH) ₃ , _H2C =C( _CH3 )COO( _CH2 ) _3Si
(OH) ₃ , HS(CH ₂ ) ₃ Si(OH) ₃ , Component (A) is obtained by partially condensing these silane triols alone or in combination. Partial condensation (partial condensate) is a state in which the hydroxy groups of the silane triol do not completely react, and a considerable amount of hydroxy groups remains, for example, about 1 mole per 3 moles of silicon atoms. means. As the silane triol used in the present invention, it is most preferable to use monomethylsilane triol. A partial condensate of monomethylsilane triol is produced by adding monomethyltrialkoxysilane to a water-alcohol mixed solvent. As the alkoxy group, methoxy group, ethoxy group,
A propoxy group, an isopropyl group, etc. can be used. The reaction mechanism is that monomethylalkoxysilane is hydrolyzed and the resulting monomethylsilane triol is condensed. This condensation is not carried out completely in a water-alcohol mixed solvent, but is carried out partially to obtain a partial condensate of monomethylsilane triol. When the partial condensate of silane triol is heated or dried, the residual hydroxyl groups are condensed to form a three-dimensional network polymer with an (O-Si-O) structure as the backbone, and the resulting product forms a three-dimensional network polymer that forms the surface layer of the printing plate material. It is what it is. When curing the partial condensate of silane triol, it is preferable to use a curing catalyst such as an alkali metal salt of a carboxylic acid such as sodium acetate, an amine carboxylate, or a quaternary ammonium carboxylate because it facilitates curing. The component (b) used in the present invention has a saponification degree of 30 to 60.
% polyvinyl alcohol. Saponification degree is 60%
If it exceeds 30%, it becomes insoluble in organic solvents, which is not preferable, and if it is less than 30%, the degree of hydrophilicity is low, which is not preferable. Polyvinyl alcohol mainly improves the hydrophilicity of the surface layer of printing plate materials. Component (iii) used in the present invention is a crosslinked product of alkali salt of polyacrylic acid. Examples of the alkali salt of polyacrylate include sodium polyacrylate and calcium polyacrylate. In the present invention, this polyacrylic acid alkali salt is crosslinked with a crosslinking agent. Examples of crosslinking agents include diglycidyl ether compounds such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and glycerin diglycidyl ether, epichlorohydrin, epibromohydrin,
Haloepoxy compounds such as α-methylepichlorohydrin, aldehyde compounds such as glutaraldehyde and glyoxal, and isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate are used. The crosslinked polyacrylic acid alkali salt improves the hydrophilicity of the surface layer of the printing plate material and also improves the retention of dampening water. The photoconductive substances used as component (2) in the present invention include powdered zinc oxide, silicon, germanium, arsenic, tellurium, selenium, gallium arsenide, cadmium sulfide, cadmium selenide, lead sulfide, and lead telluride. , gallium arsenide, selenium-tellurium mixed crystal,
Inorganic substances such as arsenic-selenium-tellurium mixed crystals, or organic substances such as berimide, oxathiazole, polyvinylcarbazole, polyvinylpyrene, polyvinylacridine, polyacenaphthylene, and polyvinylanthracene can be used. In addition, when using an organic substance, trinitrofluorenone, triallylcarbonium salt, benzopyrylium salt,
It is common to use a sensitizer such as crystal violet in combination. This photoconductive substance imparts photoconductivity to the surface layer of the printing plate material and enables the formation of an electrostatic latent image. The composition according to the present invention can be obtained by uniformly dissolving or dispersing the components (a) to (d) described above in an organic solvent. Examples of organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether. and mixed solvents of these alcohols and water,
Acetic acid, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, ethyl cellosolve, butyl cellosolve, acetic acid cellosolve, toluene, xylene, trichloroethylene, chloroform, acetone, tetrahydrofuran, ethylene glycol monoethyl ether acetate, ethylene glycol dimethyl ether, etc. alone or in combination It is used as In the present invention, it is preferable to add inorganic powder insoluble in the organic solvent as necessary. The inorganic powder that is insoluble in organic solvents may be one that is insoluble in organic solvents or has extremely low solubility.
For example, metal or nonmetal oxides such as zinc oxide, aluminum oxide, antimony oxide, calcium oxide, chromium oxide, tin oxide, titanium oxide, iron oxide, copper oxide, lead oxide, bismuth oxide, magnesium oxide, manganese oxide, and calcium carbonate. , salts such as calcium sulfate, silicon compounds such as silicon dioxide, natural pigments such as kaolin, bentonite, and clay, and various metal powders such as aluminum, iron, and zinc. When an inorganic powder insoluble in an organic solvent is present in the surface layer of a printing plate material, it forms fine irregularities on the surface. Further, the particle size of the inorganic powder may be about 320 mesh passes, and the smaller the particle size, the more preferable it is. In preparing the composition according to the present invention, for example, a trialkoxysilane such as monomethyltrialkoxysilane is added to a water-alcohol mixed solvent, and the silane, which is the component (a), is hydrolyzed and condensed. A partial condensate of triol is produced, and then component (b) polyvinyl alcohol with a degree of saponification of 30 to 60%, component (c) a crosslinked product of alkali polyacrylate salt, and component (d) a photoconductive substance are combined. If necessary, an inorganic powder insoluble in the organic solvent, a chelating agent, a pigment, a dye, a thickener, etc. may be added and vigorously stirred to defoam. The quantitative proportions of each component in the composition according to the present invention are preferably as follows. That is, the amount of polyvinyl alcohol is
Polyvinyl alcohol 50-200 parts per 100 parts by weight
It is about 80 to 180 parts by weight, more preferably about 80 to 180 parts by weight. If polyvinyl alcohol is less than 50 parts by weight, the surface layer tends to lack hydrophilicity,
Moreover, if it exceeds 200 parts by weight, the surface layer may melt and cause printing stains. The amount of cross-linked polyacrylic acid alkali salt is 100% of silane triol.
It is about 50 to 200 parts by weight, more preferably about 80 to 150 parts by weight. If the amount of polyacrylic acid alkal salt is less than 50 parts by weight, the ability to retain dampening water on the surface of the printing plate material will decrease, and the hydrophilicity will tend to decrease, while if it exceeds 200 parts by weight, dampening water will tend to decrease. There is a tendency that the capacity to retain the energy does not increase, which tends to be uneconomical. The amount of the photoconductive substance is about 5 to 50 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of silane triol.
It is about 30 parts by weight. When the amount of the photoconductive substance is less than 5 parts by weight, it tends to be difficult to form an electrostatic latent image on the surface of the printing plate material. In addition, when the amount exceeds 50 parts by weight, the amount of polyvinyl alcohol and polyacrylic acid alkali salt tends to decrease relatively.
Hydrophilicity tends to decrease. Further, the amount of inorganic powder insoluble in organic solvents added as needed is about 30 to 150 parts by weight, preferably 50 to 120 parts by weight, based on 100 parts by weight of silane triol.
It is about parts by weight. If the amount of the inorganic powder insoluble in the organic solvent is less than 30 parts by weight, it tends to cause variations in the unevenness of the surface of the printing plate material and also tends to cause variations in the adhesion of the developing powder that forms the image area. . Further, even if the amount exceeds 150 parts by weight, the adhesion of the developing powder cannot be improved much, and adding more than this tends to be uneconomical. As the base material for applying the composition according to the present invention, any material may be used as long as it is inexpensive and satisfies the required performance as a lithographic printing plate, such as aluminum, iron, copper, zinc, Foils or plates made of single metals such as lead or alloys thereof; plastic films or sheet-like molded products made of polyester, polypropylene, polyimide, polyacrylonitrile, polycarbonate, polyamide, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyethylene, etc. , synthetic paper, art paper,
Various materials such as coated paper, cardboard, thin paper, etc. can be used. Aluminum, zinc, iron, etc. are suitable as the metal base material. As the plastic base material, polyethylene, polyimide, and polycarbonate, which have relatively high dimensional stability, are suitable. As the paper base material, synthetic paper, coated paper, art paper, and cardboard are suitable. When applying the composition according to the present invention to a metal substrate, 5%
-Sulfosalicylic acid, ethylenediaminetetraacetic acid, trans-cyclohexane-1,2-diaminetetraacetic acid, butane-1,2,3,4-tetracarboxylic acid, propylenediaminetetraacetic acid, pentamethylenediaminetetraacetic acid, cyclopentane-1, Chelating agents such as 2-diaminetetraacetic acid, cyclohexane-1,4-diaminetetraacetic acid, and 2-hydroxytrimethylenediaminetetraacetic acid may be added to the composition according to the present invention. Furthermore, the substrate does not need to be pretreated prior to application of the composition according to the invention, as long as its surface is not contaminated with oily substances. If necessary, the specific surface area of the substrate surface can be reduced by physically treating the surface of the substrate by wet or dry hoing, ball polishing, brush polishing, etc., or by chemically treating it by chemical conversion treatment with acid or alkali. Of course, there is no problem in increasing it. (d) Examples Example 1 100 parts by weight of monomethyltrimethoxysilane was added to an organic solvent prepared by mixing 700 parts by weight of water and 700 parts by weight of isopropanol, and then the degree of saponification was 55.
After dissolving 100 parts by weight of % polyvinyl alcohol, cross-linked sodium polyacrylate (Sumitomo Chemical
Co., Ltd., trade name Sumikagel) 100 parts by weight, zinc oxide
30 parts by weight, 100 parts by weight of silicon dioxide having a particle size of 10 to 15 mmμ, and 1 part by weight of sodium acetate were added, mixed and stirred to obtain a composition. This composition was applied to a degreased aluminum thin plate (JIS A-1100, thickness 0.15 mm, dimensions 200 mm x 300
mm) with a #6 bar coater and heated to 100°C.
was heated for 60 seconds to form a surface layer (surface film), and a lithographic printing plate material was obtained. A toner image (test pattern: 175 lines, halftone dots 3 to 75%) was formed on the surface of this lithographic printing plate material using an electrophotographic copying machine to obtain a lithographic printing plate. When this lithographic printing plate was printed on high-quality paper using a Heidel KORD printing machine, approximately 10,000 prints were obtained without any background smudges. Example 2 After adding 100 parts by weight of monomethyltrimethoxysilane to an organic solvent prepared by mixing 800 parts by weight of water and 500 parts by weight of methanol, and then dissolving 80 parts by weight of polyvinyl alcohol with a degree of saponification of 40%. , 90 parts by weight of a crosslinked product of sodium polyacrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumikagel), 20 parts by weight of lead telluride, 55 parts by weight of titanium oxide with a particle size of 10 to 15 mmμ, and 2 parts by weight of sodium acetate were added. The mixture was mixed and stirred to obtain a composition. This composition was used in the same manner as in Example 1 to obtain a lithographic printing plate. Example 1 using this lithographic printing plate
When printing was carried out in the same manner as in Example 2, about 10,000 prints were obtained without any occurrence of scumming or the like. Example 3 100 parts by weight of γ-glycidoxypropyltrimethoxysilane was added to an organic solvent prepared by mixing 400 parts by weight of water and 1000 parts by weight of isopropanol, and then polyvinyl alcohol with a degree of saponification of 50% was added.
After dissolving 100 parts by weight of sodium polyacrylate, 50 parts by weight of a crosslinked product of sodium polyacrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumikagel), 15 parts by weight of polyvinylcarbazole, and 1 part by weight of crystal violet as a sensitizer. 30 parts by weight of barium sulfate having a particle size of 10 to 15 mmμ and 1 part by weight of sodium acetate were added, mixed and stirred to obtain a composition. This composition was used in the same manner as in Example 1 to obtain a lithographic printing plate. Example 1 using this lithographic printing plate
When printing was carried out in the same manner as in Example 3, about 10,000 prints were obtained without any occurrence of scumming or the like. Comparative example 100 parts by weight of monomethyltrimethoxysilane was added to an organic solvent prepared by mixing 700 parts by weight of water and 700 parts by weight of isopropanol, and then zinc oxide was added.
30 parts by weight, 100 parts by weight of silicon dioxide having a particle size of 10 to 15 mmμ, and 1 part by weight of sodium acetate were added, mixed and stirred to obtain a composition. This composition was prepared in Example 1.
A lithographic printing plate was obtained in the same manner as above. When printing was carried out using this lithographic printing plate in the same manner as in Example 1, in the comparative example, background smear occurred from the start of printing, and from about the 200th sheet onwards, the background smear became noticeable and printing could not be continued. Ta. As is clear from the above results, by using the lithographic printing plate material according to the example, more printed matter with less scumming can be obtained compared to the lithographic printing plate material according to the comparative example. (e) Effects of the invention The lithographic printing plate material obtained by applying the composition of the present invention to a base material is different from the conventional lithographic printing plate material (master paper) in that the surface layer of the lithographic printing plate material is It is made hydrophilic and has improved water film retention in non-image areas, so if you print with it, you can get printed matter with less scumming. Furthermore, when an inorganic powder insoluble in an organic solvent is added to the composition of the present invention, fine irregularities are formed on the surface of the lithographic printing plate material, and the image area formed by the toner is affected by the printing plate material. This has the effect of improving adhesion.

[Claims]

1 In an organic solvent, (a) General formula (); CH ₂ = CXCOO (CH ₂ ) _o Si (OH) ₃ () (in the formula, X represents a hydrogen atom or a methyl group,
n represents an integer of 1 to 6. ) A trihydroxysilane compound represented by (b) a polymerization catalyst for the trihydroxysilane compound, (c) polyvinyl alcohol with a saponification degree of 30 to 60%, and (d) a crosslinked product of an alkali salt of polyacrylic acid. (e) A composition for forming a surface layer of a lithographic printing plate material, characterized in that it is formed by dissolving or dispersing a photoconductive substance and (e) a photoconductive substance.