JP2794128B2 - Photosensitive layer for printing plate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive layer for a printing plate, and more particularly, to a photosensitive layer for a printing plate which is excellent in ink deposition property and storage stability and has improved developability. About layers.

b. Prior art It is conventionally known to apply a diazo-based photosensitizer to a negative-working photosensitive layer for a lithographic printing plate. Above all, in a photosensitive lithographic printing plate having a photosensitive layer formed on an aluminum thin plate, a diazo photosensitive agent is an indispensable element.

In recent years, many of the materials forming the photosensitive layer of the photosensitive lithographic printing have a diazo-based sensitizer, a polymer that can be mixed with the sensitizer, and a dye, a pigment, a preservative, and a coating property that are added as needed. It is made of a plasticizer or a surfactant for improving the quality.

Among the materials that form these photosensitive layers, those that have a significant effect on the characteristics of the photosensitive lithographic printing plate, such as image reproducibility, inking property, printing durability, storage stability, and developability, are high molecular polymers. There are many cases.

As the high-molecular polymer, generally, JP-A-50-118802
No., JP-A-53-120903, JP-A-54-88403, Japanese Patent Publication No. 5
Various acrylic polymers disclosed in, for example, JP-A-7-43890 are used, and these copolymers are used in a negative-working photosensitive layer. These copolymers have a hydroxyl group (-OH group) that is insoluble in water and necessary for adhesion to an aluminum sheet, and a hydrophilic functional group such as a carboxylic acid group (-COOH group) that can be developed in a weak alkaline aqueous solution. Is an alkali-soluble acrylic copolymer having the formula:

c. Problems to be Solved by the Invention However, these copolymers are either negative-working photosensitive lithographic printing plates (hereinafter referred to as negative-working PS plates) either because of a hygroscopic resin or using these as a material for a photosensitive layer. Is not very good in long-term storage. Further, there is a disadvantage that the gum loses due to the desensitized gum applied after the development at the time of plate making, and at the time of printing, troubles such as defective ink deposition occur.

Further, as a developer for these negative PS plates, JP-A No.
51-77401, JP-A-53-44202, JP-B-59-36256, etc., as described in alkaline agents, organic solvents,
Compositions containing surfactants and water are common, but among these, organic solvents have health problems in terms of toxicity and odor, and also have drawbacks such as environmentally unsatisfactory waste liquid. . Further, the surfactant has a problem that bubbles are generated during development or drainage. Therefore, it was not a very preferable developer composition.

On the other hand, a developer composition not containing an organic solvent or a surfactant is conventionally used as a positive photosensitive lithographic printing plate (hereinafter, referred to as a positive PS plate).
It is called a version. ), But this developer could not develop the negative PS plate as described above. Further, there is a problem that even if the development is apparently performed, a residual film remains and becomes dirty.

The present invention has been intensively studied to improve the above-mentioned disadvantages, and as a result, by mixing a specific copolymer in the photosensitive layer, the ink inking property is excellent, and there is no change in the developability over a long period of time. Further, the present invention has found a photosensitive layer which can be developed by any of a developing solution comprising an alkali agent, an organic solvent, a surfactant and water, or a developing solution comprising only an alkali agent and water.

d. Means for Solving the Problems That is, the present invention relates to a method for preparing p-hydroxystyrene and mono (2-methacryloxyethyl) in a photosensitive layer containing an acrylic copolymer having a hydroxyl group and a carboxylic acid group and a diazo photosensitive agent. A) a photosensitive layer for a printing plate, characterized by mixing a copolymer containing hexahydrophthalate as a copolymer component, and a copolymer component of p-hydroxystyrene and mono (2-methacryloxyethyl) hexahydrophthalate. The present invention provides a photosensitive layer for a printing plate, characterized in that a copolymer containing 20 to 80% by weight is mixed in the photosensitive layer.

 Hereinafter, the present invention will be described in more detail.

The copolymer (hereinafter, referred to as the mixed copolymer of the present invention) containing p-hydroxystyrene and mono (2-methacryloxyethyl) hexahydrophthalate as copolymer components used in the present invention is a kind of acryl. It belongs to a system copolymer, and includes p-hydroxystyrene and mono (2-methacryloxyethyl) hexahydrophthalate as copolymer components, and may further be obtained by copolymerizing other components. Other components can be arbitrarily selected as long as they are general unsaturated compounds.
Among them, 2-hydroxyethyl methacrylate, ethyl methacrylate, acrylonitrile and the like are particularly preferable.

In the mixed copolymer of the present invention, the content of P-hydroxystyrene is 60 to 90% by weight based on the total amount of the outer copolymer.
And more preferably 70 to 80% by weight. When the content is less than 60% by weight, the ink inking property is deteriorated, and when the content is more than 90% by weight, development becomes difficult with a negative PS plate developer comprising an alkali agent, an organic solvent, a surfactant and water.

The content of mono (2-methacryloxyethyl) hexahydrophthalate is 10 to 10% based on the total amount of the copolymer.
It is preferably 40% by weight, more preferably 20 to 30% by weight. If it is less than 10% by weight, it will be difficult to dissolve in a negative PS plate developer, and if it is more than 40% by weight, the ink inking property will be poor.

It is desirable that the content of the mixture copolymer of the present invention in the photosensitive layer for a printing plate of the present invention is mixed in the range of 20 to 80% by weight based on the total weight of the photosensitive layer. If the content is less than 20% by weight, the gum is easily lost, the ink adhesion is poor, and development cannot be performed with a positive PS plate developer comprising an alkali agent and water. In addition, when the weight is 80% by weight or more, the printing durability decreases, and the negative PS
It becomes impossible to develop with the plate developer.

The acrylic copolymer having a hydroxyl group and a carboxylic acid group contained in the photosensitive layer of the present invention is obtained by copolymerizing an addition polymerizable unsaturated compound having a hydroxyl group and an addition polymerizable unsaturated compound having a carboxylic acid group. Can be made.

Examples of the addition-polymerizable unsaturated compound having a hydroxyl group include: (1) acrylate and methacrylate having a hydroxyl group: for example, 2-hydroxyethyl, or 2-hydroxypropyl acrylate, hydroxydodecyl, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol , Dipropylene glycol,
Polyethylene glycol, polypropylone glycol,
Trimethylolpropane pentaerythol, 2-hydroxy-3-phenoxypropyl, 2-hydroxy-3
Acrylates and methacrylates such as methylphenoxypropyl; (2) acrylates and methacrylates of hydroxyl-containing oligoesters: for example, polyester diols of succinic acid and propylene glycol, polyester diols of maleic acid and propylene glycol, phthalic acid Acrylics such as polyester diols with propylene glycol, polyester diols with hexahydrophthalic acid and propylene glycol, polyester diols with tetrahydrophthalic acid and propylene glycol, and polyester diols with tetrahydrophthalic acid and propylene glycol and glycerin-1-butyl ether And methacrylates, (3) acrylamide and methacrylamide having a hydroxyl group or Derivatives: e.g. hydroxyethyl, hydroxyphenyl, hydroxynaphthyl, and the like acrylamide or methacrylamide such as N- hydroxyethyl -N- methyl. Examples of the addition-polymerizable unsaturated compound having a carboxylic acid group include acrylic acid, methacrylic acid,
Mono (2-methacryloxyethyl) hexahydrophthalate, mono (2-acryloxyethyl) hexahydrophthalate and the like can be mentioned.

The above acrylic copolymer may further be copolymerized with another addition-polymerizable unsaturated compound. As the other addition-polymerizable unsaturated compound, a general unsaturated compound can be arbitrarily used, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl,
n-amyl, n-hexyl, 2-ethylhexyl, octyl, lauryl, dodecyl, cyclohexyl, tetrahydrofuryl, benzyl, stearyl, dimethylaminoethyl, diethylaminoethyl, chloroethyl, aryl (eg, phenyl, tolyl, naphthyl, etc.), glycidyls And acrylic esters or methacrylic esters, or nitriles such as acrylonitrile and methacrylonitrile.

In the acrylic copolymer, the content of the addition-polymerizable unsaturated compound having a hydroxyl group is preferably from 10 to 70% by weight, more preferably from 20 to 70% by weight, based on the total amount of the acrylic copolymer.
~ 60% by weight. When the content is less than 10% by weight, the adhesion to the aluminum support is deteriorated.

The content of the addition polymerizable unsaturated compound having a carboxylic acid group is 2.0 to 40 with respect to the total amount of the acrylic copolymer.
%, More preferably 3.0 to 30% by weight. If it is less than 2.0% by weight, it will be difficult to dissolve in a weakly alkaline aqueous solution and the developability will be poor. If it is more than 40% by weight, gelation occurs depending on the reaction conditions.

The acrylic copolymer is preferably contained in an amount of about 10 to 70% by weight based on the total weight of the photosensitive layer.

When the content is 10% by weight or less, an image is easily damaged by a negative PS plate developer comprising an alkali agent, an organic solvent, a surfactant and water, and when the content is 70% by weight or more, the inking property and the storage stability become poor. Further, it becomes difficult to develop with a positive PS plate developer comprising an alkali agent and water.

In the present invention, as the diazo-based photosensitive agent added to the photosensitive layer, a conventionally known negative-type photosensitive agent such as a diazo resin and a diazo compound (a compound having two or more diazo groups) can be used. Particularly preferred are diazo resins. Examples of diazo resins include Japanese Patent Publication No. 40-8611.
And diazodiarylamines described in US Pat. No. 2,922,715 and US Pat. No. 2,946,683, and an active carbonyl compound such as formaldehyde and acetaldehyde. Examples of the diazoarylamine include 4-diazodiphenylamine, 4-diazo-3-methyldiphenylamine, 4-diazo-3'-methyldiphenylamine, 4-diazo-4'-methoxydiphenylamine, and 4-diazo-3-methoxydiphenylamine. And the like.

Most preferably, the diazo resin is used in the form of an organic salt or an inorganic salt. Examples of compounds that form an organic salt by combining with the above diazo resin include JP-B-40-2203,
Compounds described in JP-B-41-6813, JP-B-47-1167, etc., for example, benzenesulfonic acid, p-toluenesulfonic acid, 2,5-xylenesulfonic acid, linear or side chain type dodecylbenzenesulfonic acid (commonly known) Dodecylbenzenesulfonic acid), 2-methoxy-4-hydroxy-5-benzoylbenzenesulfonic acid, methanyl yellow, 2-chlorotoluene-4-sulfonic acid and alkali metal salts, alkaline earth metal salts, ammonium salts and the like thereof. be able to.

Examples of the compound which forms an inorganic salt by combining with the above diazo resin include JP-B-40-2203 and JP-A-54-9861.
No. 3, compounds described in U.S. Pat.No. 4,093,465, such as borofluoric acid, hexafluorophosphoric acid, phosphotungstic acid, thiocyanic acid and alkali metal salts thereof,
Ammonium salts and the like can be mentioned.

The diazo-based photosensitizers can be used alone or in combination, and the content is preferably about 5 to 30% by weight based on the total weight of the photosensitive layer.

A dye or pigment can be added to the photosensitive layer of the present invention for coloring. As these dyes or pigments, dyes or pigments which are not eluted by the developing solution from the image portion (cured portion by irradiation with ultraviolet rays or the like) during development of the photosensitive layer are desirable.

Examples of the dye include crystal violet, malachide green, Victoria blue, methylene blue, ethyl violet, rhodamine B, and the like, and basic oily dyes that are derivatives thereof. Commercially available such dyes include Victoria Pure Blue BOH
(Made by Hodogaya Chemical Co., Ltd.), oil cable # 603
(Manufactured by Orient Chemical Co., Ltd.) and Permanent Blue # 47 (manufactured by Daido Chemical Co., Ltd.).

Examples of the pigment include phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone red, and indanthrene blue. Commercial products include Neozapon Blue FLE (manufactured by Vertish Aniline Co., Ltd.), Oil Blue BOS (manufactured by Orient Chemical Co., Ltd.), and Spiron Blue GNH (manufactured by Hodogaya Chemical Industry Co., Ltd.). is there.

The content of the dye is about 0.1 to the total weight of the photosensitive layer.
To 5.0% by weight, more preferably 0.5 to 4.0% by weight. The content of the pigment is about 1.0 to 5.0% by weight, more preferably 2.0 to 4.0% by weight based on the total weight of the photosensitive layer.
% By weight.

Further, a preservative may be added to the photosensitive layer of the present invention. As a preservative, for example, citric acid, tartaric acid, lactic acid, 5-sulfosalicylic acid, oxalic acid, DL-malic acid,
2-methoxy-4-hydroxy-5-benzoyl-benzenesulfonic acid and the like. The content of these preservatives is about 0.1 to 4.0% by weight, more preferably 0.5 to 3.0% by weight, based on the total weight in the photosensitive layer.

Furthermore, a plasticizer or a surfactant can be added for the purpose of improving the coating property of the photosensitive layer and improving the inking property of the photosensitive layer. As the plasticizer, for example, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, diisononyl phthalate, ethyl phthalyl ethyl glycol, dimethyl Isophthalate and the like can be mentioned.

The content of the above plasticizer is, based on the total weight of the photosensitive layer, about
0.5 to 3.0% by weight, more preferably 0.6 to 2.0% by weight
It is.

Examples of the surfactant include sorbitan monooleate, sorbitan stearate, sorbitan monostearate, sorbitan sex oleate, sorbitan monolaurate, polyoxyethylene noniphenyl ether, and polyoxyethylene octyl phenyl ether. .

The content of the surfactant is about 0.4 to 2.0% by weight, more preferably 0.6 to 1.6% by weight based on the total weight of the photosensitive layer.
% By weight.

When the photosensitive layer of the present invention is formed on a support, two kinds of acrylic copolymers, diazo-based photosensitizers and dyes and pigments to be added as required, a preservative, a plasticizer, and a surfactant are used in the present invention. A mixed solvent of one or more of organic solvents such as methanol, methylene chloride, ethyl acetate, tetrahydrofuran, N-N-dimethylformamide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, etc. And coated on a support using various coating machines (for example, a wheeler, a roll coater, a bar coater, an extrusion coater, etc.) and dried.

As a support, paper, plastic film, or a metal plate such as copper, zinc, aluminum, and stainless steel,
Further, a composite material in which two or more of these materials are combined can be used. Among them, an aluminum plate polished with a brush or a ball, an aluminum plate polished with a brush and then anodized, and anodized after an electrolytic polished plate An aluminum plate that has been treated or an aluminum plate that has been subjected to a treatment combining these are suitable.

The aluminum plate subjected to such a pre-treatment, further alkali conversion treatment with alkali silicate, zirconium fluoride, alkyl titanate, trihydroxybenzoic acid,
After boehmite treatment or coating treatment with an aqueous solution of strontium acetate, zinc acetate, magnesium acetate, calcium benzoate, etc., coating treatment with polyvinyl pyrrolidone, polyamine sulfonic acid, polyacrylic acid, polymethacrylic acid, poly-2-hydroxyethyl acrylate, etc. It can be performed as a process.

The photosensitive layer of the present invention coated on the support is exposed to actinic rays such as ultraviolet rays, and is developed with a weakly alkaline aqueous solution as a developer to obtain an image.

The photosensitive layer of the present invention can be used as a resist for fine processing or a photosensitive layer for image formation.

e. Action The photosensitive layer of the present invention obtained by mixing the mixed copolymer of the present invention with a photosensitive layer containing an acrylic copolymer having a hydroxyl group and a carboxylic acid group and a diazo-based photosensitizer is coated on a support. The printing plate for a photosensitive plate coated and dried on a plate has no hygroscopicity and strong oil sensitivity, and thus has no ink loss due to the desensitized gum at the time of plate making and has good ink inking property. In addition, a printed matter free from stains can be obtained without any change in developability or ink deposition property over a long period of time.

Furthermore, even though the photosensitive layer is originally a negative-working photosensitive layer, it can be developed with a developer for developing a positive working PS plate, which is economically and workally advantageous. It is.

f. Examples Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 An aluminum plate was washed with an aqueous solution at 80 ° C. in which 3% of sodium hydroxide and 5% of sodium silicate were dissolved, polished with a brush, and then anodized with a sulfuric acid electrolyte for 1 minute (current density).
2A / dm ^3, voltage 10V) and. Next, after washing with water, the film is treated with an aqueous solution containing 5% of sodium silicate for 10 seconds,
An anodized aluminum plate was prepared. A photosensitive solution having the following composition was applied to the aluminum plate using a spin coater (wheeler), and then dried at 80 ° C. for 3 minutes.
A photosensitive lithographic printing plate having a thickness of 1.7 g / m ² was obtained.

Composition of photosensitive solution Acrylic copolymer (1) 1.5 g Mixed copolymer (A) 1.5 g Diazo-based photosensitizer (1) (2-methoxy-4-hydroxy-5-condensate of 4-diazodiphenylamine and formaldehyde) Benzoylbenzenesulfonate) 0.3 g Victoria Pure Blue BOH (manufactured by Hodogaya Chemical Industry Co., Ltd.) 0.1 g tartaric acid 0.03 g ethylene glycol monomethyl ether 90 g NN-dimethylformamide 10 g The acrylic copolymer (1) is as follows: It was manufactured as follows.

Under a nitrogen stream, 0.3 g of azobisisobutyronitrile was added to 150 g of dioxane, the mixture was heated to 80 to 85 ° C., and a mixture having the following composition was dropped into the mixture with stirring.

2-Hydroxy-3-phenoxypropyl acrylate 40 g methyl methacrylate 30 g acrylonitrile 10 g acrylic acid 20 g After dropping, stirring was continued for 5 hours, 150 g of dioxane was added, and the mixture was poured into water to precipitate the copolymer. . The precipitate was redissolved in 2-methoxyethanol, dropped into water, purified, and dried in vacuum (70 ° C.) to obtain a copolymer (1).

A 20% by weight solution of this copolymer in 2-methoxyethanol was prepared, and its viscosity was measured to be 300 CPS (25 ° C.).

The mixed copolymer (A) is an acrylic copolymer (1)
And polymerized with the following composition in the same manner as described above.

Note: 80 g of p-hydroxystyrene 20 g of mono (2-methacryloxyethyl) hexahydrophthalate A 20 wt% 2-methoxyethanol solution of this copolymer was prepared, and its viscosity was measured. As a result, it was 100 CPS (25 ° C.).

Example 2 A photosensitive lithographic printing plate was obtained in the same manner as in Example 1 except that a photosensitive solution having the following composition was used.

Acrylic copolymer (1) 2.0 g Mixed copolymer (B) 1.0 g Diazo compound (2) (dodecylbenzenesulfonate of condensate of 4-diazodiphenylamine and formaldehyde) 0.3 g Oil blue # 603 (Orient 0.1 g citric acid 0.03 g ethylene glycol monomethyl ether 90 g NN-dimethylformamide 10 g The above mixed copolymer (B) is an acrylic copolymer (1)
In the same manner as in the above, it was obtained by polymerization with the following composition.

Note: 70 g of p-hydroxystyrene 10 g of acrylonitrile 20 g of mono (2-methacryloxyethyl) hexahydrophthalate A 20% by weight solution of this mixed copolymer in 2-methoxyethanol was prepared, and the viscosity was measured to be 120 CPS (25 ° C.).
Met.

Example 3 A photosensitive lithographic printing plate was obtained in the same manner as in Example 1 except that a photosensitive solution having the following composition was used.

Acrylic copolymer (1) 1.0 g Mixed copolymer (C) 2.0 g Diazo-based photosensitizer (3) (hexafluorophosphate of condensate of 4-diazo-3-methoxydiphenylamine and formaldehyde) 0.3 g Oil blue # 603 0.1g DL-malic acid 0.03g Ethylene glycol monomethyl ether 90g N-N-dimethylformamide 10g The above mixed copolymer (C) is an acrylic copolymer (1)
And polymerized with the following composition in the same manner as described above.

P-Hydroxystyrene 70 g Ethyl methacrylate 5 g Mono (2-methacryloxyethyl) hexahydrophthalate 25 g A 20% by weight solution of this mixed copolymer in 2-methoxyethanol was prepared, and the viscosity was measured to be 150 CPS (25 ° C.).
Met.

Example 4 A photosensitive lithographic printing plate was obtained in the same manner as in Example 1 except that a photosensitive solution having the following composition was used.

Acrylic copolymer (1) 1.5 g Mixed copolymer (D) 1.5 g Diazo compound (1) 0.3 g Oil blue # 603 0.1 g Oxalic acid 0.03 g Ethylene glycol monomethyl ether 90 g N-N-dimethylformamide 10 g The mixed copolymer (D) is an acrylic copolymer (1)
In the same manner as in the above, it was obtained by polymerization with the following composition.

P-hydroxystyrene 70 g 2-hydroxyethyl methacrylate 5 g acryltrinil 5 g mono (2-methacryloxyethyl) hexahydrophthalate 20 g A 20% by weight solution of this mixed copolymer in 2-methoxyethanol was prepared, and the viscosity was measured. However, 170 CPS (25 ° C)
Met.

Comparative Example 1 A photosensitive lithographic printing plate was obtained in the same manner as in Example 1, except that a photosensitive solution having the following composition was used.

Acrylic copolymer (1) 3.0 g Diazo compound (1) 0.3 g Victoria Pure Blue BOH 0.1 g Oxalic acid 0.03 g Ethylene glycol monomethyl ether 90 g N-N-dimethylformamide 10 g Comparative Example 2 For a photosensitive solution having the following composition A photosensitive lithographic printing plate was obtained in the same manner as in Example 1, except for the difference.

Acrylic copolymer (1) 3.0 g Diazo compound (2) 0.3 g Oil blue # 603 0.1 g DL-malic acid 0.03 g Ethylene glycol monomethyl ether 90 g N-N-dimethylformamide 10 g These Examples 1-4 and comparison A negative film was vacuum adhered on the photosensitive layers of the various photosensitive lithographic printing plates obtained in Examples 1 and 2, and irradiated with ultraviolet rays at a distance of 1 m for 30 seconds using a 2 kW high-pressure mercury lamp, and then a developer having the following composition (1),
Using (2), the developability of each plate was observed (developer temperature: 25 ° C.). Table 1 shows the results.

Developer (1) (similar composition to positive PS plate developer) JIS No. 3 sodium silicate 25 g potassium hydroxide 15 g water 1 kg Developer (2) (similar composition to negative PS plate developer) 20% potassium silicate aqueous solution 50 g phenyl glycol PGH (organic solvent) 40 g potassium isopropyl naphthalenedisulfonic acid (surfactant) 5 g potassium sulfite 2 g water 903 g From the results shown in Table 1, it can be seen that the lithographic printing plate according to the present invention has an advantage that it can be developed even with a conventionally used developing solution for a positive working PS plate, while being a negative working printing plate.

Next, the plates prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were exposed and developed with a developer (2). After washing with water, a desensitized gum solution (arabian gum 8 ° Baume solution) was thinly applied and dried to obtain each lithographic printing plate.

Each of these plates is printed on a high-quality paper with an offset printing press (Heidelberg KOR type printing press) using a commercially available ink, and the number of prints from the start of printing until a print with sufficient ink density is obtained (the ) And press life. Table 2 shows the results.

From the results shown in Table 2, it can be seen that the lithographic printing plate according to the present invention is particularly excellent in terms of ink deposition.

In addition, the various photosensitive lithographic printing plates obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were left in a high-temperature atmosphere at a temperature of 30 ° C. and a humidity of 80% for several days, after which plate making and proof printing were performed. ,
The number of days (preservability) at which the non-image area begins to cause background soiling was examined. Table 3 shows the results.

From the results shown in Table 3, it is understood that the photosensitive lithographic printing plate according to the present invention has excellent storage stability.

f. Effects of the Invention According to the present invention, it is possible to obtain a negative-working photosensitive layer for a printing plate which is excellent in ink deposition property and storage stability and can be developed even with a developer for a positive PS plate.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03F 7/021 G03F 7/033

Claims (2)

(57) [Claims] 1. A photosensitive layer containing an acrylic copolymer having a hydroxyl group and a carboxylic acid group and a diazo photosensitive agent contains p
-A photosensitive layer for a printing plate, wherein a copolymer containing hydroxystyrene and mono (2-methacryloxyethyl) hexahydrophthalate as copolymer components is mixed. 2. A photosensitive layer containing 20 to 80% by weight of a copolymer containing p-hydroxystyrene and mono (2-methacryloxyethyl) hexahydrophthalate as copolymer components. Item 6. The photosensitive layer for a printing plate according to item 1).