JPS63257758A - Photosensitive planographic printing plate - Google Patents

Abstract

PURPOSE:To prevent scumming and to improve developability and plate wear by incorporating a specific high-polymer compd. into an under coating layer of a photosensitive compsn. layer contg. a diazonium compd. and polyurethane resin. CONSTITUTION:The high-polymer compd. having a sulfonic acid group in the molecule is incorporated into the under coating layer of the photosensitive compsn. layer contg. the diazonium compd. and the polyurethane resin. p-Styrene sulfonic acid, 2-acrylamide-2-methyl propane sulfonic acid, etc., are used for the high-polymer compd. and there is no limit in the mol.wt. range thereof as far as said compd. is soluble in solvent. The amt. of the monomer unit having the sulfonic acid group to be incorporated into the high-polymer compd. is adequately 1-100mol.%, more preferably 5-100mol.%. The coating amt. thereof is adequately about 0.0001-1g/m<2>, more preferably 0.0005-0.2g/m<2>.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a photosensitive lithographic printing plate.

More specifically, the developability is improved, and background stains are less likely to occur.
This invention relates to a photosensitive planographic printing plate with excellent printing durability.

[Conventional technology]

Obtaining printed matter without scumming is one of the essential conditions that a lithographic printing plate should have. The scumming increases especially with storage time after manufacture. Even if there is no scumming immediately after manufacture, scumming will occur after a certain period of time after manufacture. This tendency is particularly noticeable when stored under high temperature and high humidity conditions. Therefore, there is a need for a photosensitive lithographic printing plate that can withstand long-term storage, especially storage under high temperature and high humidity conditions, and does not cause scumming.

Many such attempts have been made in the past.

For example, a photosensitive lithographic printing plate in which an undercoat layer made of polyvinylphosphonic acid is provided on the surface of an anodized aluminum plate, and a photosensitive layer containing a diazo compound is provided thereon (West German Patent No. 1, 621, 478); A photosensitive planographic printing plate (West German Patent No. 1.091) in which an aluminum support is undercoated with polyacrylic acid, etc., and a diazo resin is applied thereon.
, No. 433), a photosensitive lithographic printing plate with a polyacrylamide undercoat and a photosensitive layer thereon (U.S. Pat. No. 3,5
No. 11,661), a polymeric organic acid is added to the photosensitive layer in order to improve the stability over time of a photosensitive lithographic printing plate having a photosensitive layer containing a diazo compound and an organic polymer carrier and to prevent the occurrence of scumming. A method of adding (JP-A-56-107238) and the like are known. However, none of these methods exhibited sufficient effects, and further improvements were desired.

Further, JP-A-59-101651 discloses a technique for providing an undercoat layer of a polymer having a sulfonic acid group between a photosensitive layer and a support.

However, although this method can prevent the occurrence of scumming, there is a problem in that a lithographic printing plate having sufficient printing durability cannot be obtained.

On the other hand, the composition of the photosensitive layer of a photosensitive lithographic printing plate using a diazonium compound is disclosed, for example, in U.S. Pat.
As described in the specification of No. 66, diazo resin alone, that is, without a binder, and as described in JP-A-50-30604, for example, a binder and diazo resin are mixed. However, in recent years, many photosensitive lithographic printing plates using diazonium compounds are made of a diazonium compound and a polymer as a binder in order to have high printing durability.

As described in JP-A No. 50-30604, such a photosensitive layer is of the so-called alkaline development type, in which the unexposed area is removed (developed) with an aqueous alkaline developer, and the so-called alkaline development type, in which the unexposed area is removed (developed) with an aqueous alkaline developer, and the photosensitive layer is developed with an organic solvent developer. Although the so-called solvent-developed type is known, from the viewpoint of occupational safety and health, the alkaline-developed type is attracting attention, and this is mainly determined by the properties of the binder.

A method for imparting alkaline developability to the binder is to copolymerize a carboxylic acid-containing monomer as described in JP-A-50-30604, or as described in U.S. Pat. No. 2,861,058. There is a method of introducing carboxylic acid into a polymer by reacting the hydroxyl group of polyvinyl alcohol with a cyclic acid anhydride such as phthalic anhydride, but the resulting polymer has poor wear resistance due to its structure. However, from photosensitive lithographic printing plates containing such a binder in the photosensitive layer, only lithographic printing plates with low stiffness resistance could be obtained. On the other hand, polyvinyl acetal forms a tough film and has abrasion resistance, but has the disadvantage that only organic solvent-developable photosensitive lithographic printing plates can be obtained.

Polyurethane resins are also known as polymers with excellent abrasion resistance. , and a combination system of a diazonium salt polycondensate and a branched polyurethane resin. However, none of these polyurethane resins have an alkali-soluble group, so they inherently have insufficient solubility in aqueous alkaline developers, and it is extremely difficult to develop them without leaving a residual film. there were.

On the other hand, Japanese Patent Application No. 60-263233 describes a polyurethane having high printing durability and excellent developability. According to the same description, if a photosensitive lithographic printing plate is stored for a long period of time under high temperature and high humidity after being manufactured, a residual film will be formed during development, and scumming will likely occur.

[Problem that the invention seeks to solve]

An object of the present invention is to overcome the above-mentioned drawbacks, and to provide a photosensitive lithographic printing plate which has improved developability, is less prone to scumming, and has excellent stiffness resistance.

[Means for solving problems]

The present inventors have made extensive studies to achieve the above object, and have found that a support is provided with a layer containing a polymeric compound having a sulfonic acid group in its molecule as an undercoat layer, and contains a diazonium compound and a polyurethane resin. It has been found that by providing a photosensitive composition layer, as a result of a very specific combination, developability is improved, a photosensitive lithographic printing plate that is less prone to scumming and has excellent stiffness resistance can be obtained.

The sulfonic acid group in the polymer compound used in the undercoat layer of the present invention can be obtained by polymerizing at least one type of monomer having a sulfonic acid group or by copolymerizing it with other monomers not having a sulfonic acid group. In addition to being able to be introduced into polymer compounds, chemical modification reactions of existing polymers (e.g.
sulfonation) into cough polymer compounds.

Here, as a monomer unit having a sulfonic acid group,
For example, p-styrenesulfonic acid, 2-acrylamide-
2-methylpropanesulfonic acid, ethylenesulfonic acid,
2-chloroethylenesulfonic acid, ethylenedisulfonic acid, 1-propene-1-sulfonic acid, 1-propene-2-
Sulfonic acid, 2-methyl-1,3-propenedisulfonic acid, 1-butene-1-sulfonic acid, 1-pentene-1-
Sulfonic acid, 1-hexene-1-sulfonic acid, 2-phenylethylenesulfonic acid, ■-methyl-2-phenylethylenesulfonic acid, 3-chloroallylsulfonic acid, allylsulfonic acid, 3-chloro-2-butenesulfonic acid ,3
-chloromethallylsulfonic acid, metaallylsulfonic acid, 3-methylylsulfonic acid, 3-phenylmethallylsulfonic acid, 2-hensylallylsulfonic acid, 2-chloro-4-styrenesulfonic acid, vinyltoluenesulfonic acid, Examples include those derived from alkali metal salts of α-methylstyrenesulfonic acid, sodium p-styrenesulfonate, sodium 2-acrylamido-2-methylpropanesulfonate, and the like.

Among these, particularly preferred monomers in the present invention are p-
These include styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, ethylene sulfonic acid, and alkali metals such as sodium salts and potassium salts. One or more of these are appropriately selected and polymerized, or copolymerized with other monomers. In the case of copolymerization, the partner monomer may be any monomer as long as it can be copolymerized with these monomers having a sulfonic acid group, but particularly preferred ones include alkyl acrylates (methyl acrylate, ethyl acrylate, etc.).
n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate,
n-amyl acrylate, isoamyl acrylate, n
-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, 2-hydroxyethyl acrylate, etc.), alkyl methacrylates (methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n- Butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate,
2-ethylhexyl methacrylate, n-octyl methacrylate, n-decyl methacrylate, 2-hydroxyethyl methacrylate, etc.), styrenes (styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethyl Styrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3゜5-dimethylstyrene, 2,4,5-1-dimethylstyrene,
2.4.6-) dimethylstyrene, 0-ethylstyrene, o-5ec-butylstyrene, o-tert-7
'Chylstyrene, p-fluorostyrene, 2,5-difluorostyrene, 0-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, 2,5-dichlorostyrene, 2,6-dichlorostyrene , 3.4-dichlorostyrene, p-bromostyrene,
p-cyanostyrene, etc.), acrylonitrile, methacrylaterile, acrylamide, N-5ec-butylacrylamide, N-tert~butylacrylamide,
Included are N,N-diptylacrylamide, N-tert-butylmethacrylamide, acrylic acid, methacrylic acid, vinyl acetate, and the like.

The molecular weight range of the polymer compound used in the undercoat layer of the present invention is not limited as long as it is soluble in the solvent, but as a general guideline, a range of about 1,000 to about t, ooo, ooo is suitable. Yes, preferably 2,000 to 100,000
．． The most preferred range is 10,000 to ioo, ooo.

Further, the amount of the sulfonic acid group-containing 7-unit unit contained in the polymer compound can be used within a wide range, and is suitably in the range of about 1 to 100 mol%, more preferably in the range of 5 to 100 mol%. be.

The polymer compound used in the undercoat layer of the present invention can be synthesized by a conventionally known method. For example, it can be polymerized by a solution polymerization method, and if desired, it can be collected by neutralizing the acid groups of the produced polymer. can. In this solution polymerization method, polymerization is usually carried out in a solvent such as isopropyl alcohol that can dissolve the raw material monomers in a nitrogen atmosphere in the presence of a polymerization initiator. Alternatively, it is also possible to obtain an aqueous dispersion by emulsifying the raw material monomer in water with a surfactant in the same manner as in the usual latex synthesis, and then emulsion polymerizing it using a polymerization initiator such as potassium persulfate. , may be collected as a solid substance.

The above-mentioned polymer compound can be prepared by dissolving garlic in a suitable solvent,
It may be applied onto a support by a conventionally known method.

The amount of coating varies depending on the polymer compound used, so it is difficult to determine it unconditionally, but it is approximately 0.0001 to 1 g /
tri is appropriate. If it is less than 0.0001g/a, the effect of suppressing the occurrence of scumming will decrease;
If it exceeds /m, the rigidity resistance etc. of the lithographic printing plate after plate making will be adversely affected.

Therefore, it is preferably O, OOO5 to 0.2 g/bo. Appropriate additives such as phosphoric acid,
A pH adjuster such as phosphorous acid, oxalic acid, or a low molecular weight organic sulfonic acid, or a wetting agent such as saponin may be added.

The undercoat layer of the present invention can be provided on various supports. For example, paper, paper laminated with plastic (such as polyethylene, polypropylene, polystyrene, etc.), sheets of metal such as aluminum (including aluminum alloys), zinc, copper, etc., such as cellulose diacetate, cellulose triacetate. Films of plastics such as cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc., paper or plastic film laminated with or vapor-deposited with metals such as those mentioned above. etc. are included. Among these supports, aluminum plates are particularly preferred because they are extremely dimensionally stable and inexpensive. Furthermore, a composite sheet in which an aluminum sheet is bonded to a polyethylene terephthalate film as described in Japanese Patent Publication No. 48-18327 is also preferred.

In addition, in the case of a support having a surface of metal, especially aluminum, surface treatments such as graining treatment, immersion treatment in an aqueous solution of sodium silicate, potassium fluorozirconate, phosphate, etc., or anodization treatment are performed. It is preferable that Also, as described in U.S. Patent No. 2,714,066, an aluminum plate immersed in a sodium silicate solution, and as described in Japanese Patent Publication No. 47-5125, an aluminum plate can be anodized. Aluminum treated and then immersed in an aqueous solution of an alkali metal silicate, treated by a combination of mechanical and electrolytic roughening as described in U.S. Pat. No. 4,476,006. Supports are also suitably used.

The above-mentioned anodizing treatment may be performed using, for example, an aqueous or non-aqueous solution of an inorganic acid such as phosphoric acid, chromic acid, sulfuric acid, or boric acid, or an organic acid such as oxalic acid or sulfamic acid, or a salt thereof, either alone or in combination of two or more. It is carried out by passing an electric current through an aluminum plate as an anode in an electrolytic solution.

It is also preferable that the material is grained, anodized, and then sealed. Such pore sealing treatment is performed using a sodium silicate aqueous solution,
This is carried out by immersion in hot water and a hot aqueous solution containing an inorganic or organic salt, a steam bath, and the like.

Noricate electrodeposition as described in U.S. Pat. No. 3,658,662 is also effective.

Examples of the diazonium compound used in the photosensitive layer of the present invention include the diazonium compounds described in U.S. Pat. No. 3,867,147 and the diazonium compounds described in U.S. Pat. No. 2,632,703, but especially aromatic diazonium salts and active carbonyl-containing compounds, etc. Diazo resins represented by condensates with (for example, formaldehyde) are useful. Preferred diazo resins include, for example, hexafluorophosphates, tetrafluoroborates, and phosphates of condensates of p-diazodiphenylamine and formaldehyde or acetaldehyde. Also, U.S. Patent No. 33
Sulfonates of condensates of p-diazodiphenylamine and formaldehyde as described in No. 00309 (e.g. p-)luenesulfonates, dodecylbenzenesulfonates, 2-methoxy-4-hydroxy-5
-benzoylbenzenesulfonate, etc.), phosphinates (e.g., benzenephosphinate, etc.), hydroxy group-containing compound salts (e.g., 2,4-dihydroxybenzophenone salt, etc.), organic carboxylates, etc. are also preferred.

Furthermore, 3-methoxyl 4-diazodifninylamine as shown in JP-A No. 58-27141 is added to 4.4
Mesitylene sulfonate obtained by condensation with '-bis-methoxy-methyl-diphenyl ether is also suitable.

The content of these diazonium compounds in the photosensitive composition is 1 to 50% by weight, preferably 3 to 20% by weight.

Moreover, two or more types of diazonium compounds may be used in combination, if necessary.

On the other hand, the polyurethane resin used in the photosensitive composition layer of the present invention includes a film-forming, solvent-soluble linear polyurethane resin described in Japanese Patent Publication No. 49-36961, and a linear polyurethane resin described in West German Patent No. 2948555. A reaction product of a polyurethane prepolymer having free isocyanate groups at the terminals and a compound having at least three hydroxyl groups in the molecule, described in as yet unpublished Japanese Patent Application No. 60-263232, Polyurethane resins having groups having carboxyl groups are useful. Furthermore, the polyurethane resin suitably used in the present invention is a polyurethane resin mainly containing a group having a carboxyl group in the main chain, and a group having a hydroxyl group and/or a nitrile group, and preferably has the following general formula ( 1) and the diisocyanate compound represented by the general formula (
It includes a polyurethane resin whose basic skeleton is a reaction product of a diol compound having a carboxyl group represented by n) or (I[).

0CN-R, -NGO(1) HO-R, -C-R4-OH(II) 0OH HOR3Ar R40H(I[I) OOH In the formula, RI is a divalent aliphatic which may have a substituent Or indicates an aromatic hydrocarbon. If necessary, R1 may contain other functional groups that do not react with isocyanate groups, such as ester, urethane, amide, and ureido groups.

R2 is a hydrogen atom, alkyl which may have a substituent,
It represents an aralkyl, aryl, alkoxy, or aryloxy group, preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 15 carbon atoms. R4, R4,
Rs may be the same or different, and may be a single bond,
Indicates a divalent aliphatic or aromatic hydrocarbon that may have a substituent. Preferably, it is an alkylene group having 1 to 20 carbon atoms, or an arylene group having 6 to 15 carbon atoms, and more preferably an alkylene group having 1 to 8 carbon atoms. Further, if necessary, R3, R4, and R3 may contain other functional groups that do not react with isocyanate groups, such as ester, urethane, amide, ureido, and ether groups. Note that R2, R
Two or three of s, R4, and Rs may form a ring.

Ar represents a trivalent aromatic hydrocarbon which may have a substituent, preferably an aromatic group having 6 to 15 carbon atoms.

Specifically, the diisocyanate compound represented by the general formula (I) includes those shown below.

That is, 2,4-tolylene diisocyanate, a dimer of 2゜4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-xylylene diisocyanate, m
-xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 3°3'-dimethylbiphenyl-4,4'-
Aromatic diisocyanate compounds such as diisocyanate; aliphatic diisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, dimer acid diisocyanate; isophorone diisocyanate), 4.
4'-methylenebis(cyclohexyl isocyanate)
, methylcyclohexane-2,4 (or 2,6) diisocyanate, l.

Examples include aliphatic diisocyanate compounds such as 3-(isocyanatomethyl)cyclohexane, and diisocyanate compounds which are reaction products of diol and diisocyanate such as an adduct of 1 mol of 1,3-butylene glycol and 2 mol of tolylene diisocyanate. It will be done.

Moreover, the diol compound having a carboxyl group represented by the general formula (II) or (II[) specifically includes those shown below.

That is, 3,5-dihydroxybenzoic acid, 2,2-bis(
hydroxymethyl)propionic acid, 2゜2-bis(2-
hydroxyethyl)propionic acid, 2,2-bis(3-
hydroxypropyl)propionic acid, bis(hydroxymethyl)acetic acid, his(4-hydroxyphenyl)acetic acid,
4,4-bis(4-hydroxyphenyl)pentane M,
Examples include tartaric acid.

The hydroxyl group and/or nitrile group contained in the polyurethane resin is a hydroxyl group and/or a part of the carboxyl group derived from general formula (II) or (III).
Alternatively, it can be incorporated into a polyurethane resin by reacting with a halogen compound having a nirolyl group in the presence of a base. In the case of a nitrile group, it can also be introduced into the polyurethane resin by using a diol compound having a nitrile group together with a diol compound of general formula (n) or (III).゛The polyurethane resin used in the photosensitive composition layer of the present invention is formed from a diisocyanate compound represented by general formula (1) and two or more diol compounds having a carboxyl group represented by general formula (n) or (III). may be done.

Furthermore, a diol compound that does not have a carboxyl group and may have other substituents that do not react with isocyanate may be used in combination to the extent that the alkali developability is not deteriorated.

Specifically, such diol compounds include those shown below.

Namely, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, 1.3-7' ethylene glycol, 1
．． 6-hexanediol, 2-butene-1,4-diol, 2゜2.4-1-methyl-1,3-bentanediol, ■, 4-bis-β-hydroxyethoxycyclohexane, cyclohexane dimetatool, tricyclo Decane dimetatool, hydrogenated bisphenol A1 hydrogenated bisphenol F1 ethylene oxide adduct of bisphenol A, propylene oxide adduct to bisphenol,
Ethylene oxide adduct of bisphenol F, propylene oxide adduct of bisphenol F, ethylene oxide adduct of hydrogenated bisphenol A, propylene oxide adduct of hydrogenated bisphenol A, hydroquinone dihydroxyethyl ether, p-xylylene glycol, dihydroxyethyl sulfone , bis(2-hydroxyethyl)-2,4-)lylene dicarbamate, 2.4
-) rylene-bis(2-hydroxyethyl rubamide)
, bis(2-hydroxyethyl)-m-xylylene dicarbamate, bis(2-hydroxyethyl) isophthalate, and the like.

The above-mentioned polyurethane resin is synthesized by heating the above-mentioned diisocyanate compound and diol compound in an aprotic solvent, adding a known catalyst having an activity corresponding to the reactivity of each compound. The molar ratio of diisocyanate and diol compound used is preferably from 0.8:1 to 1
．． If the ratio is 2:1 and an isocyanate group remains at the end of the polymer, the polymer can be finally synthesized in a form in which no inocyanate group remains by treating with an alcohol or an amine.

The molecular weight of the polyurethane resin of the present invention is preferably 1000 or more on weight average, more preferably s, ooo
~100,000.

These polyurethane resins may be used alone or in combination. The content of these polymer compounds contained in the photosensitive composition is about 50 to 99.5% by weight, preferably about 55 to 95% by weight.

The photosensitive composition of the present invention may also contain other resins in an amount of up to 50% by weight based on the polymer. Examples of the resins to be mixed include polyamide resins, epoxy resins, polyacetal resins, acrylic resins, methacrylic resins, polystyrene resins, and novolac type phenolic resins.

The photosensitive composition of the present invention may contain dyes, pigments,
Performance can also be improved by adding stabilizers, fillers, surfactants, plasticizers, etc.

Suitable dyes include oil-soluble dyes such as C, 1°261
05 (Oil Left RR), C, Summer.

21260' (Oil Blue Letter #308), C.

1.74350 (oil blue), C, 1°520
15 (methylene blue), C, 1,42555 (crystal violet), C, 1,42595 (Victoria Pure Blue), etc.

Stabilizers include phosphoric acid, phosphorous acid, oxalic acid, p-toluenesulfonic acid, dipicolinic acid, malic acid, tartaric acid,
Examples include 2-methoxy-4-hydroxy-5-benzoyl-benzenesulfonic acid, butylnaphthalenesulfonic acid, p-hydroxybenzenesulfonic acid, and the like.

The photosensitive composition of the present invention is usually dissolved in a solvent and applied to a support provided with an undercoat layer consisting of a polymer compound containing in its molecule at least one monomer unit having a sulfonic acid group as a repeating unit. and dried before use. The coating amount is approximately 0.1 to 5 g/m" in terms of dry weight,
Preferably it is 0.3/3g/m2.

Such solvents include, for example, methanol, ethanol,
Isopropanol, n-butanol, t-butanol,
2-methoxyethanol, 1-methoxy-2-propanol, 2-ethoxyethanol, 2-methoxyethyl acetate, ethylene glycol, tetrahydrofuran,
Dioxane, dimethylsulfoxide, N,,N-dimethylformamide, acetone, methyl ethyl ketone, etc. and mixtures thereof are used.

Various additives can be further added to the photosensitive composition used in the present invention.

For example, alkyl ethers (e.g. ethyl cellulose, methyl cellulose) and fluorine surfactants to improve coating properties, plasticizers (e.g. tricresidyl phosphate, dimethyl phthalate) to impart flexibility and abrasion resistance to the coating film. , dibutyl phthalate, trioctyl phosphate, tributyl phosphate, tributyl citrate, polyethylene glycol, polypropylene glycol), and other common stabilizers for photogenic diazo resins (phosphoric acid, phosphorous acid, pyrophosphoric acid, oxalic acid). , boric acid, benzenesulfonic acid, toluenesulfonic acid, malic acid, polyacrylic acid and its copolymers, polyvinylphosphonic acid and its copolymers, polyvinylsulfonic acid and its copolymers, 5-nitronaphthalene-1-phosphone acid, 4-chlorophenoxymethylbosphonic acid, sodium phenyl-methyl-pyrazolone sulfonate, 2-phosphonobutanetricarboxylic acid-1,2,4,1-phosphonoethanetricarboxylic acid-1
, 2,2,1-hydroxyethane-1゜1-disulfonic acid, pigments such as acridine dyes, cyanine dyes, styryl dyes, triarylmethane dyes, and phthalocyanines as coloring substances to visualize the image area after development. can be added.

The amount of these additives added varies depending on the purpose of use, but is generally 0.5 to 3% of the total solid content of the photosensitive layer.
It is 0% by weight.

As a plate-making method for producing a lithographic printing plate from the photosensitive lithographic printing plate of the present invention, a conventional method can be used as is. That is, the photosensitive layer in the non-image areas is removed by exposure through a transparent original having a line image and/or halftone image, and then treatment with a developer. Suitable light sources used during exposure include mercury lamps, xenon lamps, chemical lamps, metal halide lamps, strobes, and the like. As the developer, JP-A-51-77401, JP-A-51-80228, JP-A-53-44202 are used.
Organic solvents (benzyl alcohol, ethylene glycol monophenyl ether) whose solubility in water is 101 tit% or less at room temperature, alkaline agents (triethanolamine, mono- ethanolamine), anionic surfactant (
aromatic sulfonates, dialkyl sulfosuccinic acids, alkylnaphthalene sulfonates, branched alkyl sulfate salts), water and, if necessary, antifouling agents (sodium sulfite, sodium salt of sulfopyrazolone) and water softeners (sodium salt of ethylenediaminetetraacetic acid). etc.) can be used as a weak alkaline aqueous solution.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Synthesis Examples and Examples, but the content of the present invention is not limited thereto.

In a third round bottom flask of 500 val equipped with a condenser and a stirrer was added 125 g (0.50 mole) of 4,4'-diphenylmethane diisocyanate and 2.
67 g of 2-bis(hydroxymethyl)propionic acid
(0.50 mole) was added and dissolved in 290 ml of dioxane. 1 g of N,N-diethylaniline was added as a catalyst, and the mixture was heated under reflux for 6 hours with stirring. Thereafter, the reaction solution was poured into a solution of water B and 40 ml of acetic acid with stirring to precipitate a white polymer. This polymer was filtered, washed with water, and dried under vacuum.
g of polymer was obtained.

Gel permeation chromatography (GPC)
) The weight average molecular weight (polystyrene standard) was 28,000. Furthermore, the carboxyl group content was measured by titration and found to be 2.47 meq/
It was g.

Further, 40 g of this polymer was placed in a third 300 ml round bottom flask equipped with a condenser and a stirrer, and DMF2
Dissolved at 00++11. Add 6.3 g (0,062 mole) of triethylamine to this solution and heat at 80°C.
After heating to 7.7 g (0,062
+ wole) was added dropwise over 10 minutes while stirring. Stirring was then continued for 2 hours.

After the reaction was completed, the reaction solution was poured into a solution of 41 parts of water and 200 parts of acetic acid and 11 parts of acetic acid while stirring to precipitate a white polymer. This polymer was filtered, washed with water, and dried under vacuum to obtain 42 g of polymer.

It was confirmed by NMR measurement that the hydroxyethyl group was introduced into the carboxyl group, and the content of the remaining carboxyl group was measured by titration.
eq/g (polyurethane (a) of the present invention).

Example 1 Comparison 11 An aluminum plate with a thickness of 0.24 mm was used with a nylon brush.
The surface was grained using an aqueous suspension of 00 mesh Bumiston, and then thoroughly washed with water. This was etched by immersing it in a 10% aqueous sodium hydroxide solution at 70°C for 60 seconds, then washed with running water, neutralized with 20% nitric acid, and then electrochemically roughened as described in JP-A-53-67507. law, i.e. Va=12.7 V, VC=9. I
1 in a 1% nitric acid aqueous solution using a sinusoidal alternating waveform current of V.
Electrolytic surface roughening treatment was performed using an anode special electricity amount of 60 corons/dm2.

Subsequently, it was immersed in a 30% aqueous sulfuric acid solution and desmutted at 55°C for 2 minutes, and then anodized in a 7% aqueous sulfuric acid solution so that the amount of aluminum oxide covered was 2.0 g/m''. It was immersed for 1 minute in a 3% aqueous solution of sodium silicate at ℃, washed with water and dried.A 1% aqueous solution of a copolymer having the following composition A was applied to the aluminum plate obtained in the above manner using a roll coater and dried. An undercoat layer was formed.The coating amount after drying was 0.05g.
/m2 Composition A Methyl methacrylate/ethyl acrylate/sodium 2-acrylamido-2-methylpropanesulfonate (50:30:20 molar ratio) copolymer (average molecular weight approximately 6
0,000) A photosensitive liquid (1) having the following composition was applied onto this undercoat layer using a wheeler and dried at 80° C. for 2 minutes to obtain a photosensitive lithographic printing plate. The dry weight is 2. 'Og/m2. This is designated as sample (■).

Photosensitive liquid (r) For comparison, I was hooked just because there was no undercoat layer (sample ■
A photosensitive lithographic printing plate similar to that was prepared.

This is designated as sample ① (comparative example 1).

After these samples were left at 40°C and 80% RH for 5 days, each image was exposed for 1 minute from a distance of 1 m using Fuji Photo Film's PS Light, and then exposed for 1 minute at room temperature using the following developer. After soaking, gently rub the surface with absorbent cotton,
Remove the unexposed areas and create a bright blue image on the lithographic printing plate.
I got ■.

(Developer) Each printing plate was printed on high-quality paper using a commercially available ink using a KOR type printing machine manufactured by Heidelberg.

Background smearing was observed in the printed matter printed using the printing plate ■ which did not have an undercoat layer, whereas no background smearing was observed in the printed matter printed using the printing plate which is an example of the present invention. There wasn't. In addition, there is almost no difference in printing performance between ■ and ■ in terms of rigidity resistance, and the printing area is 1sooo with no blurring.

Two prints were obtained.

Comparative Example 2 Next, as a comparative example, a photosensitive liquid (n
) was coated in the same manner (on a support that had been treated in exactly the same way as sample (1) and provided with an undercoat layer) and dried. Dry weight is 2.0g/
m''. This is designated as sample ■.

(Polymer used in Comparative Example (2)) A polymer with the following structure, a / b / c /
The molar ratio of d was 9/24158/9.

In addition, the weight average molecular weight (polystyrene standard) is 55,
It was 000.

Sample (2) was left to stand for 5 days in exactly the same manner as in Example 1, and then subjected to image exposure, development, and printing. No scumming was observed at all, but only 80,000 good prints were obtained.

An undercoat layer of a copolymer having the following composition was formed on an aluminum plate that had been surface-treated in the same manner as in Example 1. The coating amount was 0.05.
g/m"), and photosensitive liquid (1) was applied to obtain sample (2).

Composition Methyl methacrylate/methyl acrylate/sodium p-styrene sulfonate (30:40:30 molar ratio)
Copolymer sample (average molecular weight: about 80,000) Sample (2) was made into plates in exactly the same manner as in Example 1, and when printed, no scumming was observed and 180,000 good prints were obtained.

Claims (1)

[Claims] In a photosensitive lithographic printing plate in which a photosensitive composition layer containing a diazonium compound and a polyurethane resin is provided on a support, a polymer compound having a sulfonic acid group in the molecule is used as an undercoat layer for the photosensitive composition layer. A photosensitive lithographic printing plate characterized by being provided with a layer containing.