JP2944734B2 - Photosensitive layer for lithographic printing plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a photosensitive layer for a lithographic printing plate, and more particularly to a photosensitive layer for a lithographic printing plate having improved printout stability over time.

b.Conventional technology A negative photosensitive lithographic plate in which a photosensitive composition having a photosensitive diazo resin of an acrylic copolymer having a hydroxyl group and a carboxylic acid group as a main component is coated on a hydrophilized aluminum support. Printing plates are well known in the art. This printing plate forms an lipophilic image area on the surface of a hydrophilic support by exposing an image to harden an exposed area to make it insoluble in a developing solution, and dissolve and remove an unexposed area with a developing solution. It is provided for lithographic printing using water and ink.

The photosensitive diazo resin used in such a lithographic printing plate is, in most cases, an organic acid salt of an aromatic diazonium compound, a carbonyl-containing organic compound and a condensate (aromatic sulfonate as a seed).

By mixing a dye having a salt-forming ability into the photosensitive layer containing such a diazo resin, a print-out property that allows an image to be distinguished immediately after exposure is imparted.

c. Problems to be Solved by the Invention However, when the diazo resin as described above is used, the bakeout property is inferior. For this reason, JP-B-39-17602 and JP-A-54-98613 disclose, instead of an organic acid salt of a diazo resin, a halogen-substituted Lewis acid salt of a diazo resin (for example, hexacondensate of a condensate of 4-diazodiphenylamine and formaldehyde). The use of fluorophosphate has improved the bakeout property.

However, when a halogenated Lewis acid salt of a diazo resin is used, a photosensitive lithographic printing plate having a photosensitive layer comprising an acrylic copolymer having a hydroxyl group and a carboxylic acid group has poor stability over time. That is, there is a drawback that a developing defect occurs with the passage of time and the non-image portion is easily stained during printing.

In order to solve this drawback, a photoacid generator compound has been proposed as an alternative to the halogenated Lewis acid salt of diazo resin,
For example, JP-A-59-148784 and JP-A-63-261352 disclose oxadiazole compounds and trihalomethyl compounds, but no remarkable improvement in bakeout properties was found.

Therefore, the present inventor has conducted intensive studies to improve such disadvantages. As a result, instead of using a photoacid generating compound such as a halogenated Lewis acid salt of a diazo resin as a photosensitive diazo resin, an organic acid salt of a diazo resin is used. It has been found that by mixing a specific photoacid generating compound with a photosensitive layer containing a photosensitive layer, a photosensitive layer having excellent printout properties and stability over time can be obtained, and the present invention has been accomplished.

d. Means for Solving the Problems That is, the present invention relates to a lithographic printing plate photosensitive layer containing an acrylic copolymer having a hydroxyl group and a carboxylic acid group, an organic acid salt of a diazo resin and a dye, having the following general formula ( I)
A photosensitive layer for a lithographic printing plate, characterized in that 0.3 to 10% by weight of a photoacid generator compound represented by the formula (1) is mixed.

General formula: (Wherein, R represents a substituted or unsubstituted alkyl group, an aryl group or a heterocyclic compound residue; X ₁ , X ₂ and X
₃ represents a halogen atom. The acrylic copolymer having a hydroxyl group and a carboxylic acid group is produced by copolymerizing an addition polymerizable unsaturated compound having a hydroxyl group and an addition polymerizable unsaturated compound having a carboxylic acid group.

Examples of the addition-polymerizable compound having a hydroxyl group include the following.

(1) Acrylates and methacrylates having a hydroxyl group, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and hydroxydodecyl, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, trimethylo Propanepentaerythritol, 2-hydroxy-3-phenyloxypropyl, 2-
Acrylates or methacrylates such as hydroxy-3-methylphenoxypropyl.

(2) Acrylates and methacrylates of oligoesters having a hydroxyl group, for example, polyester diols of succinic acid and propylene glycol, polyester diols of maleic acid and propylene glycol, polyester diols of phthalic acid and propylene glycol, hexahydrophthalic acid and propylene Acrylates and methacrylates such as polyester diol with glycol, polyester diol with tetrahydrophthalic acid and propylene glycol, propylene glycol tetrahydrophthalate and polyester diol with glycerin-1-butyl ether.

(3) Acrylamide and methacrylamide having a hydroxyl group or derivatives thereof, for example, acrylamide or methacrylamide such as hydroxyethyl, hydroxyphenyl, hydroxynaphthyl and N-hydroxyethyl-N-methyl.

Examples of the addition-polymerizable unsaturated compound having a carboxylic acid group include acrylic acid, methacrylic acid, and mono (2
-Methacryloxyethyl) hexahydrophthalate, mono (2-acryloxyethyl) hexahydrophthalate and the like.

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.), acrylate or methacrylate of glycidyls, or acrylonitrile, methacrylonitrile, etc. Of nitriles.

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 20 to 70% by weight based on the total amount of the acrylic copolymer.
~ 60% by weight. When the amount 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 4.0 with respect to the total amount of the acrylic copolymer.
% By weight, more preferably 3.0 to 30% by weight. If it is less than 2.0% by weight, it is difficult to dissolve in an alkaline aqueous solution as a developer, and the developer is poor. If it is 40% by weight or more, gelation occurs depending on the reaction conditions.

As the organic acid salt of the diazo resin, Japanese Patent Publication No. 40-8611
, US Pat. No. 2,927,715, US Pat. No. 2,946,683, and the like, a condensate of a diazodiarylamine with an active carbonyl compound such as formaldehyde or acetaldehyde can be used as an organic acid salt.

Examples of the diazoarylamine include 4-diazodiphenylamine, 4-diazo-3-methyldiphenylamine, 4-diazo-3'-methyldiphenylamine, 4-diazo-4'-methoxydiphenylamine,
-Diazo-3-methoxydiphenylamine and the like.

Examples of the compound which forms an organic acid salt by reacting with the above condensate include compounds described in JP-B-40-2203, JP-B-41-6813, JP-B-27-1167 and the like.

Specifically, benzenesulfonic acid, p-toluenesulfonic acid, 2,5-xylenesulfonic acid, linear or side chain type dodecylbenzenesulfonic acid (commonly called dodecylbenzenesulfonic acid), 2-methoxy-4-hydroxy- Examples thereof include 5-benzoylbenzenesensulfonic acid, methanyl yellow, 2-chlorotoluene-4-sulfonic acid, and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof.

The organic acid salt of the diazo resin is preferably contained in an amount of 5 to 30% by weight based on the total weight of the photosensitive layer.

The dye used in the present invention is one that develops a color from colorless to colored by the acid generated by exposure, one that is decolorized from colored to colorless, or one that changes the hue.

Specific examples of such dyes include Victoria Pure Blue BOH (manufactured by Hodogaya Chemical Co., Ltd.), Oil Blue # 603 (manufactured by Orient Chemical Co., Ltd.), Patent Pure Blue (manufactured by Sumitomo Sangoku Chemical Co., Ltd.), crystal violet, and brilliant green. , Ethyl violet, methyl violet, methyl green, erythrosin B, basic fuchsin, malachite green, oil red, m-
Cresol purple, Rhodamine B, Auramine, 4-
Dyes such as triphenylmethane-based, diphenylmethane-based, oxazine-based, xanthene-based, iminonaphthoquinone-based, azomethine-based and anthraquinone-based dyes such as p-diethylaminophenyliminonaphthoquinone and cyano-p-diethylaminophenylacetanilide can be given. .

In the photosensitive layer of the present invention, the photoacid generating compound represented by the general formula (I) is mixed.

Examples of the photoacid generating compound include trichloromethyl-phenylsulfone, tribromomethyl-phenylsulfone, trichloromethyl-p-chlorophenylsulfone, tribromomethyl-p-nitrophenylsulfone,
Trichloromethyl-p-nitrophenylsulfone, trichloromethyl-2,4-dichlorophenylsulfone, tribromomethyl-2,4-dichlorophenylsulfone, 2-
Trichloromethylbenzothiazole-sulfone, 4,6-dimethylpyridine-2-tribromomethylsulfone, 4,6-
Dimethyl-3-cyanpyridine-2-tribromomethylsulfone and the like can be mentioned.

The photoacid generating compound is mixed in the range of 0.3 to 10% by weight based on the total weight of the photosensitive layer for a lithographic printing plate of the present invention.
If the amount is less than 0.3% by weight, an excellent bakeout effect cannot be obtained. On the other hand, when the content is 10% by weight or more, an excellent print-out effect is exhibited, but the printing durability deteriorates.

Other lipophilic high molecular weight polymers or copolymers can be added to the photosensitive layer of the present invention.

Examples include phenolic resins, substituted phenolic resins, polyhydroxystyrenes, halogenated polyhydroxystyrenes, copolymers of hydroxystyrene and acrylic compounds, styrene-maleic anhydride copolymers, acrylic resins, modified acrylic copolymers And the like.

Further, a preservative may be added to the photosensitive layer of the present invention.

Preservatives include, 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
Preferably about 0.1 to 4.0% by weight based on the total weight in the photosensitive layer
And more preferably 0.5 to 3.0% by weight.

Further, a plasticizer or a surfactant may be added to improve the inking property of the photosensitive layer or to obtain a uniform coated surface.

Examples of the plasticizer include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, diisononiel phthalate, and ethyl phthalyl ethyl glycol And dimethyl isophthalate.

The content of the plasticizer is about
0.5 to 3.0% by weight, more preferably 0.6 to 2.0% by weight
Range.

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 above surfactant is about 0.4 to 2.0% by weight, more preferably 0.6 to 1.6% by weight, based on the total weight in the photosensitive layer.

When the photosensitive layer of the present invention is formed on a support, an acrylic copolymer, an organic acid salt of a diazo resin, a dye, a photoacid generating compound, and a preservative, a plasticizer, a surfactant, and the like added as necessary. With an organic solvent such as methanol, methylene chloride, ethyl acetate, tetrahydrofuran, N-
1 such as N-dimethylformamide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether;
Dissolved in a kind or a mixed solvent of two or more kinds, and applied to various coating machines (for example, Wheeler, roll coater, bar coater,
Using an extrusion coater)
dry.

As a support on which the photosensitive layer of the present invention is applied, paper, a plastic film, or copper, zinc, aluminum,
It is possible to use a metal plate such as stainless steel, and a composite material in which two or more of these are combined.
In particular, brush or ball polished aluminum plate, brush polished and then anodized aluminum plate,
An aluminum plate subjected to electrolytic polishing and then anodized, or an aluminum plate subjected to a combination of these processes is preferred.

The aluminum plate that has undergone such pretreatment is further subjected to a chemical conversion treatment with alkali silicate, zirconium fluoride, alkyl titanate, trihydroxybenzoic acid, etc., boehmite treatment or strontium acetate, zinc acetate, magnesium acetate, calcium benzoate. Coating with an aqueous solution such as polyvinylpyrrolidone, polyaminesulfonic acid, polyacrylic acid, polymethacrylic acid, poly-2-hydroxyethyl acrylate, or the like can also be performed as a post-treatment.

An image can be obtained by exposing the photosensitive layer of the present invention coated on the support to actinic rays such as ultraviolet rays and developing using an alkaline aqueous solution as a developing solution.

Examples of the alkaline aqueous solution used as the developer include (1) sodium hydroxide and potassium hydroxide; (2) metal salts of weak acids, for example, silicic acid, metasilicic acid, orthosilicic acid, phosphoric acid, pyrophosphoric acid, metaphosphoric acid, Sodium salts such as hexametaphosphoric acid, carbonic acid, tartaric acid, and boric acid, and metal salts such as lithium salts and potassium salts; (3) ammonia and its derivatives such as alkylamic acids (eg, monomethyl, dimethyl, trimethyl,
An aqueous solution of an alkaline compound such as an amine compound such as monoethyl, diethyl, or triethyl) or an alkanolamine (for example, monoethanolamine, diethanolamine, triethanolamine, or diisopropanolamine).

An activator and / or a solvent can be added to the above alkaline aqueous solution. As the activator, an anionic surfactant or an amphoteric surfactant can be used.

As the anionic surfactant, for example, the carbonic acid number is 8 to 22.
Alcohol sulfates (eg, polyoxyethylene alkyl sulfate sodium salt), alkylaryl sulfonates (eg, sodium dodecyl benzene sulfonate, polyoxyethylene dodecyl phenyl sulfate sodium, alkyl naphthalene sulfonate),
Sodium naphthalene sulfonate, formalin condensate of sodium naphthalene sulfonate), sodium dialkyl sulfosuccinate, fatty acid amide sulfonate, alkyl phosphate, alkyl ether phosphate and the like can be used.

As the amphoteric surfactant, for example, an alkyl betaine type or an alkyl imidazoline type active agent can be used.

As the solvent, alcohols and ethers are preferable, but a solvent that does not dissolve in water (20 ° C.) by 10% or more is most preferable. Examples of this type of solvent include benzyl alcohol, DL-α-phenylethyl alcohol and 2-phenylethyl alcohol as alcohols, and phenyl glycol and propylene glycol monobutyl ether as ethers.

As the composition of the developer, the above alkaline compound 0.5 to 1
Those containing 0% by weight, 0 to 10% of a surfactant, and 0 to 10% by weight of a solvent are preferred.

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

e. Action In the photosensitive layer for a lithographic printing plate of the present invention, the change in hue between an unexposed portion and an exposed portion is remarkable. Therefore, the image can be easily recognized, and the deterioration of the photosensitive layer with the passage of time is less than that of the conventional one.

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

Examples 1 to 3 and Comparative Example 1 A web-like aluminum plate (material: 1050) having a thickness of 0.24 mm and a width of 1000 mm was alkali-degreased, and then polished with a nylon brush while applying an aqueous suspension of permiston. Washed with water.

Then, 70 ° C, 20% caustic soda solution was poured over 5 seconds, the surface was etched at 3 g / m ^2, and then washed with running water,
It was electropolished in an electrolytic solution consisting of hydrochloric acid (35 g / l), boric acid (20 g / l) and aluminum ions (20 g / l) at 25 ° C. at an electrolytic density of 23 A / dm ² for 6 seconds and washed with water.

Next, the surface is etched by pouring a 20% caustic soda solution at 70 ° C., followed by washing with water, and then at 30 ° C.
A solution oxidation treatment was performed in a 10% sulfuric acid aqueous solution to obtain 2.0 g / m ²
Was formed.

Next, after washing with water, it was permeated with an aqueous solution containing 5% of JIS No. 3 sodium silicate at 70 ° C. for 10 seconds, washed with water and dried.
The thus obtained aluminum plate was coated with a photosensitive layer having the following composition so as to have a dry coating weight of 1.8 g / m ² and dried at 100 ° C. for 1 minute to obtain a photosensitive lithographic printing plate. .

The acrylic copolymer (1) was produced as follows.

Dimethylformamide as the reaction solvent under a nitrogen stream
To 150 g, add 0.3 g of azobisisobutyronitrile, and add
The mixture was heated to 8585 ° C., and the mixture having the following composition was dropped therein while stirring.

After completion of the dropwise addition, stirring was continued for 5 hours, 150 g of dimethylformamide was added, and the mixture was poured into water to precipitate a copolymer. The precipitate was redissolved in 2-methoxyethanol, dropped into water, purified, and vacuum-dried (70 ° C) to obtain an acrylic copolymer (1).

The weight average molecular weight of this copolymer was measured by gel permeation chromatography (GPPC).
It was 2,000.

The resulting photosensitive lithographic printing plate was exposed to a 2KW high-pressure mercury lamp at a distance of 1m for 30 seconds, and the surface reflectance of the exposed and unexposed portions of the photosensitive layer was measured using a Murakami Color Research Laboratory CM-53P. did. Table 1 shows the results.

In Comparative Example 1, a comparative photosensitive solution to which the compound of the general formula (I) was not added was used.

As is clear from the results shown in Table 1, by adding the compound represented by the general formula (I) to the photosensitive solution,
The difference ΔR in the reflectance increases, and the image becomes clear.

Example 4, Comparative Example 2 The following photosensitive solution 4 was added to the aluminum plate used in Examples 1 to 3.
Alternatively, Comparative Photosensitive Liquid 2 was applied so that the dry coating weight became 1.8 g / m ^2, and dried at 100 ° C. for 1 minute to obtain a photosensitive lithographic printing plate.

The photosensitive layer lithographic printing plate thus obtained was exposed to a 2 kw high-pressure mercury lamp under a distance of 1 m for 30 seconds, and the surface reflectance of the photosensitive layer in the exposed and unexposed areas was the same as in Examples 1 to 3. It was measured. Table 2 shows the results.

In addition, these photosensitive layer lithographic printing plates are exposed to high temperature and high humidity (35
(80 ° C, 80%) for several days, expose as above, develop with the following developer at 25 ° C for 30 seconds, wash with water, desensitize with gum arabic, and apply to a printing machine The presence or absence was checked. Table 2 shows the number of days of storage (storability) until contamination occurs
Shown in It can be said that the longer the number of days of standing, the more excellent the photosensitive layer printing plate is over time stability.

As is clear from the results shown in Table 2, the photosensitive layer for a lithographic printing plate of Example 4 had a more unexposed part than the photosensitive layer of Comparative Example 2 in which a halogenated Lewis acid salt of a diazo resin was used as a photosensitive agent. The difference ΔR in the reflectance of the exposed portion is large, and the printout image is clear. Further, the stability with time is also excellent.

f. Effects of the Invention According to the present invention, a photosensitive layer for a lithographic printing plate having a sharp printout image and excellent stability over time can be obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03F 7/004 G03F 7/021 G03F 7/033

Claims (1)

(57) [Claims] 1. A photoacid generator represented by the following general formula (I) in a lithographic printing plate photosensitive layer containing an acrylic copolymer having a hydroxyl group and a carboxylic acid group, an organic acid salt of a diazo resin and a dye. A photosensitive layer for a lithographic printing plate, comprising 0.3 to 10% by weight of a compound. General formula: (Wherein, R represents a substituted or unsubstituted alkyl group, an aryl group or a heterocyclic compound residue; X ₁ , X ₂ and X
₃ represents a halogen atom. )