JPH0764279A - Photosensitive lithographic printing plate - Google Patents

Abstract

PURPOSE:To improve gradation without decreasing sensitivity and printing durability by successively forming specified two kinds of positive photosensitive layers on a supporting body. CONSTITUTION:A positive photosensitive layer (a) containing an o-quinone diazide compd. in which its diazo groups are isolated, and a positive photosensitive layer (b) containing an o-quinone diazide compd. are formed in the order of (a) and (b) on a supporting body. More preferably, the proportion of radicals of diazo groups in the o-quinone diazide compd. in the positive photosensitive layer (a) is 1-80mol% of the whole diazo groups in the o-quinone diazide compd. As for the coating method for the upper layer (b), it is preferable to use a water, hydrocarbon or alcohol-base solvent as a coating solvent to disperse the photosensitive liquid. The photosensitive liquid is dispersed, for example, by using a ball mill, sand grinder, roll mill, three-roll method, high pressure homogenizier, ultradisperser, bubble homogenizer or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive lithographic printing plate, and more specifically, it is a positive type photosensitive lithographic printing plate in which gradation is improved without lowering sensitivity and decreasing printing durability. It is about the print version.

[0002]

BACKGROUND OF THE INVENTION In a positive-working photosensitive lithographic printing plate containing a conventional o-quinonediazide compound, in order to obtain high contrast, there is a technique of adding a high contrast agent (surfactant etc.) to a photosensitive layer. . However, the addition of a surfactant or the like deteriorates the photosensitivity and lowers the sensitivity. Also,
Japanese Patent Application Laid-Open No. 4-44045 discloses a photosensitive layer containing a resin containing a presensitized photoreceptor and a photosensitive component for the purpose of enhancing gradation.
This also has a problem that the sensitivity is lowered and the film thickness of the unexposed portion is reduced.

Techniques for improving the sensitivity include adding an organic acid to the photosensitive layer, lowering the molecular weight of the binder resin in the composition, and forming the film of the photosensitive layer when the photosensitive liquid is applied to the support. There are technologies such as thinning,
In these known techniques, development tolerance (development latitude)
However, there is a problem that the film loss occurs mainly in the over-developing process, and it is not always possible to obtain a high contrast, and the printing durability is deteriorated.

Further, as a known example in the past, there is a known example in which a latex resin is provided on the surface of the photosensitive layer to improve long-term processing stability and printing durability (JP-A-4-3).
No. 28748), which has a problem that sensitivity is lowered by the upper latex resin layer.

[0005]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a photosensitive lithographic printing plate having improved gradation properties without lowering sensitivity and printing durability.

[0006]

The above object of the present invention is to provide a positive type photosensitive layer containing (a) an o-quinonediazide compound having a diazo group contained therein, and (b) a positive type photosensitive layer containing an o-quinonediazide compound. , (A), (b) in this order on the support to form a photosensitive lithographic printing plate, (a) o
The liberation of the diazo groups of the quinonediazide compound is achieved by each of the photosensitive lithographic printing plates according to claim 1, which is 1 mol% to 80 mol% of the total diazo groups in the o-quinonediazide compound.

For the method of coating the photosensitive layer and the coating solvent of the present invention, known coating techniques can be used for both the upper layer (b layer) and the lower layer (a layer).

As a method for coating the upper layer (layer b) of the present invention, it is preferable to disperse the photosensitive liquid using a solvent of water, hydrocarbon, or alcohol as a coating solvent. As a dispersing method, a ball mill or a sand grinder is used. , Roll mill,
A three-roll method, a high pressure homogenizer, an ultra disperser, a bubble homogenizer and the like can be mentioned. As a method for applying the dispersion liquid, an air spray method, an airless spray method, an electrostatic air spray method, an electrostatic atomization electrostatic coating method, or the like, is used as a dispersion liquid spray coating method (JP-A-57-24558).
No.) is disclosed, a known coating method (wire bar coating, spin coating, etc.) may be used.

A dispersing agent can be added as a dispersing technique, and preferred dispersing agents include water-soluble polymers and surfactants.

In the photosensitive composition of the present invention, the addition amount of the o-quinonediazide compound which forms an acid or a free radical upon exposure is preferably 0.01 to 30% by weight, more preferably 0.1 to 10% by weight. %.

The coating amount of the photosensitive layer on the support of the present invention is preferably 0.05 to 3.5 g / m ² as solid content in each of the upper layer (b layer) and the lower layer (a layer), and the total coating amount is 0.1 to 10 g / m ² (as solid content) is preferable.

The exposure light source of the lower layer (a layer) portion of the present invention is
A general actinic light source (described later) can be used. 500 n is required to release 1 to 80% of the total diazo groups of the o-quinonediazide compound described in claim 2.
It is preferably in the wavelength range of m or less, and the necessary amount of active ray energy is preferably 0.5 to 35 kw.

When the release rate of the diazo group in the lower layer (layer a) of the present invention is 1 mol% or less, the sensitivity becomes low, and 80 mol%
If the amount exceeds the range, the printing durability of the unexposed portion of the upper layer (layer b) deteriorates.

[0014]

The positive-working photosensitive lithographic printing plate is a photosensitive layer in which an exposed image is applied to the photosensitive layer from the original and then developed with an alkaline solution to remove the photosensitive layer in the exposed area to expose the surface of the hydrophilic support. On the other hand, the unexposed portion of the photosensitive layer is a printing plate on which the ink receiving layer is formed by remaining on the support. Conventionally, in the photosensitive lithographic printing plate, the difference between the ink repellent property of the exposed area and the ink receptivity of the unexposed area should be increased,
That is, it is required to increase the contrast between the image portion and the non-image portion. Further, it is also required to increase the sensitivity of the exposed portion, the chemical resistance of the unexposed portion (image portion), and the printing durability during printing.

In the present invention, the release of the diazo groups of the o-quinonediazide compound in the lower photosensitive layer is exposed to 1 to 80 mol% of the total diazo groups in the o-quinonediazide compound, and the upper layer is further exposed. By providing the photosensitive layer, high sensitivity can be obtained, and there is no deterioration such as film loss in the unexposed area and reduction in printing durability, and it is possible to always obtain high contrast and provide excellent gradation.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail below. The support used in any of the above-mentioned inventions (hereinafter referred to as the present invention) is preferably one that can be set in an ordinary lithographic printing plate and can withstand the load applied during printing, such as aluminum, magnesium, zinc, chromium and iron. Examples of the metal plate include copper, nickel, and the like, alloy plates of these metals, and the like. Further, a metal plate coated with chromium, zinc, copper, nickel, aluminum, iron, or the like by plating or vapor deposition may be used. Of these, the preferred support is aluminum or its alloy.

The support used in the present invention is subjected to degreasing treatment, graining treatment, anodizing treatment and the like which are commonly used in this technical field. At least graining treatment and anodizing treatment are performed in this order. It is preferred to use the support made in.

Degreasing treatment for removing rolling oil on the aluminum surface includes solvent degreasing with trichlene, thinner, etc., emulsion degreasing with kerosene and triethanol, etc. Further, in order to remove stains and natural oxide film which cannot be removed only by degreasing, an alkaline solution such as caustic soda having a concentration of 1 to 10% is added at 20 to 70 ° C. for 5 seconds to 10 seconds.
Examples include a method of dipping for a minute and then dipping in an acidic solution such as nitric acid or sulfuric acid having a concentration of 10 to 20% at 10 to 50 ° C. for 5 seconds to 5 minutes to neutralize and remove smut after alkali etching.

The graining treatment method carried out to improve the adhesion to the photosensitive layer and to improve the water retention is as follows:
There are a so-called mechanical surface-roughening method for mechanically roughening the surface and a so-called electrochemical surface-roughening method for electrochemically roughening the surface. Examples of the mechanical surface roughening method include ball polishing, brush polishing, blast polishing, buff polishing and the like. The electrochemical surface-roughening method includes, for example, a method of electrolytically treating the support with an alternating current or a direct current in an electrolytic solution containing hydrochloric acid, nitric acid, or the like. The support can be grained by using any one of these methods or a combination of two or more methods.

Since smut is formed on the surface of the support obtained by the graining treatment as described above, it is generally necessary to appropriately perform washing with water or alkali etching in order to remove the smut. preferable. Examples of such a treatment include the alkaline etching method described in Japanese Patent Publication No. 48-28123 and Japanese Patent Laid-Open No. 53-53.
Examples thereof include a treatment method such as a sulfuric acid desmutting method described in 12739.

The support used in the present invention is usually formed with an oxide film by anodic oxidation in order to improve abrasion resistance, chemical resistance and water retention. In this anodization, generally, an aqueous solution containing sulfuric acid and / or phosphoric acid or the like at a concentration of 10 to 50% is used as an electrolytic solution and a current density is 1 to 10 A /
The method of electrolyzing with dm ² is preferably used, but the method of electrolyzing with high current density in sulfuric acid described in US Pat. No. 1,412,768 and US Pat.
There is a method of electrolysis using phosphoric acid described in the specification of No. 11,661.

The support used in the present invention is preferably subjected to a surface treatment such as a sealing treatment with hot water or the like or an immersion in an aqueous solution of potassium fluorozirconate after the anodizing treatment.

Next, the lower layer (a layer) and the upper layer (b layer) of a photosensitive layer made of a photosensitive composition are coated on the surface-treated support of the present invention to form the photosensitive lithographic printing plate of the present invention. A plate is obtained. The photosensitive substance used in this photosensitive layer (a layer, b layer) is not particularly limited, and various kinds of substances usually used in photosensitive lithographic printing plates, for example, the following various substances are used. To be done.

Photosensitive composition containing o-quinonediazide compound In the photosensitive composition containing an o-quinonediazide compound used in the present invention, it is preferable to use an o-quinonediazide compound and an alkali-soluble resin in combination. o
Examples of the quinonediazide compound include ester compounds of o-naphthoquinonediazidesulfonic acid and a polycondensation resin of phenols and aldehydes or ketones.

The above-mentioned phenols include, for example, monovalent phenols such as phenol, o-cresol, m-cresol, p-cresol, 3,5-xylenol, carvacrol and thymol, and divalent ones such as catechol, resorcinol and hydroquinone. Examples include trihydric phenols such as phenol, pyrogallol, and phloroglucin. Examples of the aldehyde include formaldehyde, benzaldehyde, acetaldehyde, crotonaldehyde, and furfural. Preferred of these are formaldehyde and benzaldehyde. Examples of the ketone include acetone and methyl ethyl ketone.

Specific examples of the polycondensation resin include phenol / formaldehyde resin, m-cresol / formaldehyde resin, m- and p-mixed cresol / formaldehyde resin, resorcin / benzaldehyde resin, pyrogallol / acetone resin. To be OH of phenols of the o-naphthoquinonediazide compound
The condensation rate of o-naphthoquinonediazide sulfonic acid with respect to the group (reaction rate with respect to one OH group) is preferably 15 to 80%, and more preferably 20 to 45%.

Further, as the o-quinonediazide compound used in the present invention, the following compounds described in JP-A-58-43451 can also be used. That is, for example, 1, 2
-Benzoquinone diazide sulfonate, 1,2-
Known 1,2-naphthoquinone diazide sulfonic acid ester, 1,2-benzoquinone diazide sulfonic acid amide, 1,2-naphthoquinone diazide sulfonic acid amide, etc.
Quinone diazide compounds, more specifically J. Kosar "Light-Sensitive Systems" (Light-Sensitive System)
ems) pp. 339-352 (1965), John.
Willie & Sons (John Willey &
Sons, Inc. (New York) and W. S. De Forest, "Photoresist", Volume 50 (1975), McGraw H
ill) (New York) 1,2-
Benzoquinonediazide-4-sulfonic acid phenyl ester, 1,2,1 ', 2'-di- (benzoquinonediazide-4-sulfonyl) -dihydroxybiphenyl, 1,2
-Benzoquinonediazide-4- (N-ethyl-M-β-
Naphthyl) -sulfonamide, 1,2-naphthoquinonediazide-5-sulfonic acid cyclohexyl ester, 1-
(1,2-naphthoquinonediazide-5-sulfonyl)-
3,5-Dimethylpyrazole, 1,2-naphthoquinonediazide-5-sulfone-4'-hydroxydiphenyl-
4'-azo-β-naphthol-ester, N, N-di-
(1,2-naphthoquinonediazide-5-sulfonyl)-
Aniline, 2 '-(1,2-naphthoquinonediazide-5
-Sulfonyloxy) -1-hydroxy-anthraquinone, 1,2-naphthoquinonediazide-5-sulfone-
2,4-dihydroxybenzophenone ester, 1,2
-Naphthoquinonodiazide-5-sulfonic acid-2,3,4
-Trihydroxybenzophenone ester, a condensate of 2 mol of 1,2-naphthoquinonediazide-5-sulfonic acid chloride and 1 mol of 4,4'-diaminobenzophenone,
Condensate of 2 mol of 1,2-naphthoquinonediazide-5-sulfonic acid chloride and 1 mol of 4,4′-dihydroxy-1,1′-diphenylsulfone, 1 mol of 1,2-naphthoquinonediazide-5-sulfonic acid chloride Examples thereof include a 1,2-quinonediazide compound such as a condensate of 1 mol of purpurogallin and 1,2-naphthoquinonediazide-5- (N-dihydroabietyl) -sulfonamide. In addition, Japanese Examined Patent Publications No. 37-1953 and 37-3627
Nos. 37-13109, 40-26126, 40-3801, 45-5604, 45-27.
No. 345, No. 51-13013, JP-A-48-965.
The 1,2-quinonediazide compounds described in JP-A No. 75, 48-63802 and 48-63803 can also be mentioned.

Of the above o-quinonediazide compounds,
An o-quinone diazide ester compound obtained by reacting 1,2-benzoquinone diazide sulfonyl chloride or 1,2-naphthoquinone diazide sulfonyl chloride with pyrogallol-acetone condensation resin or 2,3,4-trihydroxybenzophenone is particularly preferable. As the o-quinonediazide compound used in the present invention, the above compounds may be used alone or in combination of two or more kinds.

The proportion of the o-quinonediazide compound in the photosensitive composition is preferably 6 to 60% by weight, and particularly preferably 10 to 50% by weight. Examples of the alkali-soluble resin include novolac resins, vinyl polymers having a phenolic hydroxyl group, and condensation resins of polyhydric phenols and aldehydes or ketones described in JP-A-55-57841.

The novolac resin used in the present invention includes, for example, phenol / formaldehyde resin, cresol / formaldehyde resin, JP-A-55-57841.
Phenol-cresol-formaldehyde copolymer resin as described in JP-A-55-127
Examples thereof include copolymer resins of p-substituted phenol and phenol or cresol and formaldehyde as described in Japanese Patent No. 553.

The novolak resin preferably has a number average molecular weight Mn of 3.00 × (polystyrene standard).
10 ^{2 to} 7.50 × 10 ³ , and the weight average molecular weight Mw is 1.
00 × 10 ^{3 to} 3.00 × 10 ⁴ , more preferably Mn
Is 5.00 × 10 ^{2 to} 4.00 × 10 ³ , and Mw is 3.0.
It is 0 × 10 ^{3 to} 2.00 × 10 ⁴ . The above novolak resins may be used alone or in combination of two or more.

The proportion of the novolak resin in the photosensitive composition is 5 to 95% by weight. Further, the vinyl copolymer having a phenolic hydroxyl group preferably used in the present invention is a polymer having a unit having the phenolic hydroxyl group in the molecular structure, and is represented by the following general formula [I] to
Polymers containing at least one structural unit of [V] are preferred.

[0033]

[Chemical 1]

[In the formula, R ₁ and R ₂ each represent a hydrogen atom, an alkyl group or a carboxyl group, preferably a hydrogen atom. R ₃ represents a hydrogen atom, a halogen atom or an alkyl group, preferably a hydrogen atom or an alkyl group such as a methyl group or an ethyl group. R ₄ represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, preferably a hydrogen atom. A represents an optionally substituted alkylene group connecting a nitrogen atom or an oxygen atom and an aromatic carbon atom, m represents an integer of 0 to 10, and B represents
Represents a phenylene group which may have a substituent or a naphthylene group which may have a substituent. ]

The polymer used in the present invention is preferably one having a copolymer type structure, and is represented by the above general formula [I].
~ Examples of the monomer unit that can be used in combination with the structural unit represented by the general formula [V] include ethylenically unsaturated offylenes such as ethylene, propylene, isobutylene, butadiene, and isoprene, for example, styrene and α-. Styrenes such as methylstyrene, p-methylstyrene and p-chlorostyrene, acrylic acids such as acrylic acid and methacrylic acid, and unsaturated aliphatic dicarboxylic acids such as itacone, maleic acid and maleic anhydride,
For example, methyl acrylate, ethyl acrylate, -n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, Α such as ethyl methacrylate
-Esters of methylene aliphatic monocarboxylic acid, for example, nitriles such as acrylonitrile, methacrylonitrile, etc., amides such as acrylamide, such as acrylanilide, p-chloroacrylanilide, m-nitroacrylanilide, m-methoxyacrylanilide, etc. Anilides such as vinyl acetate, vinyl propionate,
Vinyl esters such as vinyl benzoate and vinyl acetate,
For example, methyl vinyl ether, ethyl vinyl ether,
Isobutyl vinyl ether, vinyl ethers such as β-chloroethyl vinyl ether, vinyl chloride, vinylidene chloride, vinylidene cyanide, such as 1-methyl-1-methoxyethylene, 1,1-dimethoxyethylene, 1,2-dimethoxyethylene, 1,1 -Dimethoxycarbonylethylene, ethylene derivatives such as 1-methyl-1-nitroethylene, such as N-vinylpyrrole, N
There are N-vinyl type monomers such as -vinylcarbazole, N-vinylindole, N-vinylpyrrolidene and N-vinylpyrrolidone. These vinyl-based monomers are present in the polymer compound with a structure in which the unsaturated double bond is cleaved.

Of the above-mentioned monomers, aliphatic monocarboxylic acid esters and nitriles are preferable because they exhibit excellent performance for the purpose of the present invention. These monomers may be bound to the polymer used in the present invention in either a block or random state.

The proportion of the vinyl polymer used in the present invention in the photosensitive composition is 0.5 to 70% by weight.
As the vinyl polymer, the above polymers may be used alone or in combination of two or more kinds. It can also be used in combination with other polymer compounds.

A printout material capable of forming a visible image upon exposure can be added to the photosensitive composition.
The printout material comprises an organic dye which changes its color tone by interacting with a compound which forms an acid or a free radical upon exposure. Examples of the compound which forms an acid or a free radical upon exposure include, for example, JP-A-50- Three
O-naphthoquinonediazide-4 described in Japanese Patent No. 6209
-Sulfonic acid halogenide, o-naphthoquinonediazide-4-sulfonic acid chloride described in JP-A-53-36223 and phenols having an electron-withdrawing substituent, or an ester compound or amide compound of aniline acid, JP-A-55-77742, JP-A-5
Examples thereof include halomethylvinyloxadiazole compounds and diazonium salts described in JP-A No. 7-148784.

As the above-mentioned organic dye, Victoria Pure Blue BOH (Hodogaya Chemical Co., Ltd.), Patent Pure Blue (Sumitomo Mikuni Chemical Co., Ltd.), Oil Blue # 6
03 (manufactured by Orient Chemical Industry Co., Ltd.), Sudan Blue II
(Manufactured by BASF), crystal violet, malachite green, fuchsin, methyl violet, ethyl violet, methyl orange, brilliant green, congo red, eosin, rhodamine 66 and the like. Further, the photosensitive composition, in addition to the above materials,
If necessary, a plasticizer, a surfactant, an organic acid, an acid anhydride and the like can be added.

Further, in order to improve the oil sensitivity of the photosensitive composition, the photosensitive composition used in the present invention is, for example,
It is also possible to add a p-tert-butylphenol formaldehyde resin, a pn-octylphenol formaldehyde resin, or a resin in which these resins are partially esterified with an o-quinonediazide compound. Dissolve each of these components in the following solvent,
By coating and drying the support surface according to the present invention,
The photosensitive lithographic printing plate of the present invention can be produced by providing photosensitive layers (a layer and b layer).

Solvents that can be used to dissolve the photosensitive composition used in the present invention include methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, Diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, diethylene glycol monoisopropyl ether, propylene glycol, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dicarboxylic acid methyl ether, dipropylene glycol methyl ethyl ether, Gi Ethyl, propyl formate, butyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, dimethylformamide, dimethyl sulfoxide, dioxane, acetone, methyl ethyl ketone, cyclohexanone , Methylcyclohexanone, diacetone alcohol, acetylacetone,
γ-butyrolactone and the like can be mentioned. These solvents are
They can be used alone or in combination of two or more.

As the coating method used for coating the surface of the support with the photosensitive composition, there are conventionally known methods such as spin coating, wire bar coating, dip coating, air knife coating, roll coating, blade coating and curtain coating. Coating or the like is used. At this time, the coating amount varies depending on the application, but for example, a coating amount of 0.05 to 3.5 g / m ² is preferable for each of the upper layer (b layer) and the lower layer (a layer) as a solid content, and the total coating amount is 0. 1 to 10 g / m ² is preferable.

In the present invention, in order to release 1 to 80% of all diazo groups in the lower layer (a layer) of the o-quinonediazide compound, it is preferable that the wavelength range is 500 nm or less, and the necessary actinic ray Energy amount is 0.5 ~
35 kW is preferable.

When the release rate of the diazo group in the lower layer (a layer) of the present invention is less than 1 mol%, the sensitivity is lowered, and 80 mol%
If the amount exceeds the range, the printing durability of the unexposed portion of the upper layer (layer b) deteriorates.

When the photosensitive lithographic printing plate thus obtained is used, a conventionally used method can be applied. For example, a transparent original image having a line image, a halftone dot image or the like is adhered to the photosensitive surface. A relief image is obtained by exposing to light and then removing the photosensitive layer in the non-image area with a suitable developing solution. As a light source suitable for exposure, various actinic rays, for example, a mercury lamp, a metal halide lamp,
Xenon lamps, chemical lamps, carbon arc lamps, etc. are used, and as the developer used for development,
Alkaline aqueous solution is preferable, for example, sodium silicate,
There are aqueous alkaline solutions such as aqueous solutions of potassium silicate, sodium hydroxide, potassium hydroxide, sodium triphosphate, dibasic sodium phosphate, sodium carbonate, potassium carbonate and the like. The concentration of the alkaline aqueous solution at this time varies depending on the type of the photosensitive composition and the alkali, but is generally 0.
The range of 1 to 10% by weight is suitable, and if necessary, an organic solvent such as a surfactant or alcohol can be added to the acid-alkali aqueous solution.

[0046]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Unless otherwise specified,% means% by weight. Example 1 (Preparation of Aluminum Plate) An aluminum plate (material 1050, temper H16) having a thickness of 0.24 mm was subjected to degreasing treatment at 60 ° C. for 1 minute in a 5% aqueous sodium hydroxide solution, and then,
Electrolytic surface roughening (etching) was performed for 30 seconds at a current density of 60 A / dm ² in 1 liter of a 0.5 mol% hydrochloric acid aqueous solution, and then 60% in a 5% sodium hydroxide aqueous solution.
Desmut treatment is performed at 10 ° C. for 10 seconds, and then anodization treatment is performed in a 20% sulfuric acid solution at a temperature of 20 ° C., an electric density of 3 A / dm ² , and a treatment time of 1 minute. Further, hot water sealing treatment was performed with hot water at 80 ° C. for 20 seconds to obtain an aluminum plate for a lithographic printing plate. (Application of Photosensitive Composition Coating Liquid) The aluminum plate was coated with a photosensitive composition coating liquid having the following composition by a wire bar, and 9
It was dried at 0 ° C. for 1 minute. The film thickness of the coating film after exposure is 0.6
It was g / m ² .

Photosensitive Solution 1 Novolak resin (phenol / m-cresol / p-cresol molar ratio 10/54/36 and Mw 4000) 6.7 g o-naphthoquinonediazide compound (pyrogallolacetone resin (Mw 3000)) Condensate of o-naphthoquinonediazide-5-sulfonyl chloride: Esterification rate 30%) 1.5 g Polyethylene glycol # 2000 0.2 g Victoria Pure Blue BOH (Hodogaya Chemical Co., Ltd.) 0.08 g 2,4-bis (trichloro) Methyl) -6- (p-methoxystyryl) -S-triazine 0.15 g FC-430 (Sumitomo 3M) 0.03 g cis-1,2-cyclohexanedicarboxylic acid 0.2 g Methyl cellosolve 100 ml

The entire surface of the plate provided with the above-mentioned photosensitive layer was exposed for 20 seconds from a distance of 90 cm by using a 2 kw metal halide lamp (Idlefin 2000 manufactured by Iwasaki Electric Co., Ltd.) as a light source. When the IR spectrum of the surface of this photosensitive layer was measured, it was confirmed that 40 mol% of diazo groups were liberated. Then, on the photosensitive layer (a layer) exposed as described above, a photosensitive solution 2 having the following composition was ball-mill dispersed, spray-coated using an air sprayer, and dried at 90 ° C. for 2 minutes to form a photosensitive layer ( Layer b) was provided to prepare a positive photosensitive lithographic printing plate A. Total dry coating film thickness is 2.2 g / m ²
Met.

Photosensitive Solution 2 Novolak resin (phenol / m-cresol / p-cresol molar ratio 10/54/36 and Mw 4000) 6.7 g o-naphthoquinonediazide compound (pyrogallolacetone resin (Mw 3000)) Condensate of o-naphthoquinonediazide-5-sulfonyl chloride: Esterification rate 30%) 1.5 g Polyethylene glycol # 2000 0.2 g Victoria Pure Blue BOH (Hodogaya Chemical Co., Ltd.) 0.08 g 2,4-bis (trichloro) Methyl) -6- (p-methoxystyryl) -S-triazine 0.15 g FC-430 (Sumitomo 3M) 0.03 g cis-1,2-cyclohexanedicarboxylic acid 0.2 g water 20 ml benzyl alcohol 80 ml Dispersion aid (Polyvinyl sulfonic acid) 1.5g

Example 2 In Example 1, the entire surface of the plate provided with the photosensitive layer of the photosensitive solution 1 was changed to 5
It was exposed for 0 seconds. When the IR spectrum of the surface of this photosensitive layer was measured, it was confirmed that 60 mol% of diazo groups were liberated. The upper layer was applied in the same manner as in Example 1 to prepare a positive photosensitive lithographic printing plate B.

Comparative Example 1 The support of Example 1 was coated with the photosensitive solution 1 of Example 1 with a wire bar and dried at 90 ° C. for 4 minutes to prepare a positive photosensitive lithographic printing plate C. The thickness of the dry coating film is 2.2
It was g / m ² .

Comparative Example 2 The support of Example 1 was coated with the photosensitive solution 1 of Example 1 using a wire bar so that the thickness of the coating film when dried was 1.8 g / m ² , and the temperature was 90 ° C. And dried for 4 minutes to prepare a positive photosensitive lithographic printing plate D. Photosensitive planographic printing plates A, B, C and D obtained in Examples 1 and 2 and Comparative Examples 1 and 2.
A step tablet for sensitivity measurement (No. 2, Eastman Kodak Co., Ltd., 21-step gray scale with a density difference of 0.15 each) was closely attached, and exposed for 1 minute from a distance of 90 cm using a 2 kw metal halide lamp as a light source. Next, the exposed photosensitive lithographic printing plate was subjected to 2 times at 27 ° C. with a developer obtained by diluting SDR-1 (manufactured by Konica) developer 6 times with water.
It was developed for 0 seconds.

[Evaluation of Sensitivity and Gradation] In the evaluation of gradation, the "clear step number" refers to the step number of the step tablet which has been completely developed, and the "solid step number" refers to the complete step tablet. It refers to the number of stages that have not been developed. The sensitivity is evaluated by the value of the number of clear steps, and the higher the number of clear steps at the same exposure amount, the higher the sensitivity. The gradation is evaluated by the value of the number of solid steps-the number of clear steps. The smaller this value is, the better the gradation is.

[Evaluation of Printing Durability] The planographic printing plate obtained by the above-mentioned exposure and development method was coated on a printing machine (Heidel GTO) with coated paper printing ink (New Bright Red manufactured by Toyo Ink Mfg. Co.) and fountain solution (SEU- 3; 2.5%, manufactured by Konica), and printing is continued until defective solidification appears in the solid part of the image part of the printed matter, or ink adheres to the non-image part, at which time I counted the number of prints. The evaluation results are shown in Table 1.

[0055]

[Table 1]

* Gradation Number of solid steps-number of clear steps = 7.0 or less ○ Number of solid steps-number of clear steps = 7.0 to 10.0 Δ Number of solid steps-number of clear steps = greater than 10.0 ×

Comparative Examples 3 and 4 Regarding the layer b in Example 1, by changing the exposure distance and the exposure time, the diazo group was released in an amount of 0.5 mol% and the diazo group was released in an amount of 85 mol%. Then, the same evaluation was performed, and the former had low sensitivity, and the latter had a decrease in printing durability.

[0058]

According to the present invention, a photosensitive lithographic printing plate having improved gradation can be obtained without lowering the sensitivity and the printing durability.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Matsubara 1 Sakura-cho, Hino City, Tokyo Konica Co., Ltd. In-house (72) Inventor Katsuko Ota 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Co., Ltd. In the laboratory

Claims (2)

[Claims] 1. A positive type photosensitive layer containing an o-quinonediazide compound in which (a) itself has a diazo group liberated,
A photosensitive lithographic printing plate comprising: (b) a positive photosensitive layer containing an o-quinonediazide compound, which is provided on a support in the order of (a) and (b). 2. The photosensitive lithographic printing plate according to claim 1, wherein the release of the diazo groups of the o-quinonediazide compound (a) is 1 to 80 mol% of all the diazo groups in the o-quinonediazide compound.