JPH07271019A - Positive photosensitive planographic printing plate - Google Patents

Abstract

PURPOSE:To improve adhesion property between a grained surface and a photosensitive layer, printing durability and reproducibility for min. dots, to obtain accurate reproducibility for the tone, and to suppress production of film edges by roughening and anodically oxidizing the surface of an aluminum plate, coloring the surface, and applying a specified positive photosensitive compsn. thereon. CONSTITUTION:The surface of an aluminum plate is roughened and anodically oxidized, and then colored with a soln. containing a UV-absorbing pigment having the max. absorption wavelength in 340 to 450nm region so that the absorption in the max. absorption wavelength is increased by >0.01. Then a positive photosensitive compsn. layer containing o-quinone diazide compd. is formed on the surface. It is preferable that the UV-absorbing pigment has the max. absorption wavelength in a shorter wavelength region (which does not give bad influences on a visualized image by exposed). Further, it is preferable that the UV-absorbing pigment is insoluble with the solvent used to form the positive photosensitive resin layer containing o-quinone diazide. by coating.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a positive-working photosensitive lithographic printing plate.

[0002]

BACKGROUND OF THE INVENTION A photosensitive lithographic printing plate is one in which a photosensitive layer is provided on a hydrophilic support. For example, in a positive type photosensitive lithographic printing plate, an actinic ray such as ultraviolet rays is provided on the hydrophilic support. An ink-receptive photosensitive layer that is solubilized by exposure to is formed.

Usually, an o-quinonediazide compound is used as a photosensitive component in the photosensitive layer of a positive type photosensitive lithographic printing plate. In addition, an alkali-soluble resin is usually used in combination as a component for increasing the film strength and alkali-solubility.

As the above-mentioned o-quinonediazide compound,
1,2-naphthoquinone-2-diazide-5-sulfonic acid ester compounds and 1,2-naphthoquinone-2-diazide-4-sulfonic acid ester compounds are generally used as useful compounds, and particularly, pyrogallol and aldehydes. Alternatively, an ester compound with a polycondensation resin with a ketone or the like is preferably used.

In such a positive-working photosensitive lithographic printing plate, when the photosensitive layer is imagewise exposed and then developed, the ink-receptive photosensitive layer in the exposed area is removed and the surface of the hydrophilic support is exposed. On the other hand, the non-exposed portion of the photosensitive layer which is ink-receptive remains on the support to form an ink-receptive layer. In lithographic printing, the difference in the property that the exposed portion is hydrophilic and the unexposed portion is lipophilic is used.

Image exposure of the photosensitive layer is carried out by bringing a positive original film into close contact with a positive type photosensitive lithographic printing plate and irradiating it with ultraviolet rays, but it is roughened and anodized on an aluminum support. A support that scatters light well like a body causes halation due to reflection from the support when exposed, especially when exposed for a long time, and reproducibility of small dots remarkably deteriorates. There was a problem that I could not get it.

[0007] In order to have faithful tone reproducibility, good reproduction of minimum halftone dots, and to prevent film edge marks from occurring easily, the surface of an anodized aluminum plate is dyed to obtain 340 to 450 nm. At the maximum wavelength of light absorption in the range, the reflection density DS is set to be 0.08 to 0.4 higher than that in the case without dyeing.
However, when the amount of dye adhering is increased and the reflection optical density DS is increased in order to bring out the effect more sufficiently, the exposure visibility and the sand formed on the surface of the aluminum plate are disclosed. Adhesion between the eyes and the photosensitive layer is reduced, and there are problems in plate inspection and printing durability. In addition, the publication also states that when a monobasic acid dye is used for dyeing the surface of an aluminum plate, residual color is reduced, image contrast is high, and erasing workability is very excellent. However, even in this case, the deposition amount of the dye is increased and the reflection optical density DS
When the value is increased, a problem remains in the adhesiveness between the grain formed on the surface of the aluminum plate and the photosensitive layer, and a residual film is generated to cause stains on the printing ground.

Further, the techniques disclosed in Japanese Patent Publication No. 59-26479 and Japanese Patent Laid-Open No. 57-118238 also have a problem that sensitivity is lowered.

Then, the inventors of the present invention have studied and found that instead of the ultraviolet absorbing dye, an ultraviolet absorbing pigment, particularly an ultraviolet absorbing pigment which is insoluble in the solvent for coating the photosensitive liquid, is used for roughening and then anodizing treatment of aluminum. By coloring the surface of the plate, the orientation rate of the UV absorption function on the grain is increased, and even at low concentration (low absorption rate), it is effective for reproducing the minimum halftone dot, so it does not adversely affect the visibility of exposure. It is also possible to increase the amount of dye deposited and increase the reflection optical density DS.
When the value is increased, the problem that the adhesiveness between the grain formed on the surface of the aluminum plate and the photosensitive layer is lowered can be solved,
It has been found that good minimum dot reproducibility and adhesion can be obtained. Further, when a UV-absorbing pigment is used in combination with an alkaline aqueous solution-soluble or alkaline aqueous solution-swelling compound, residual color and background stain are reduced, image contrast is high, and a positive photosensitive lithographic printing plate excellent in erasing workability is obtained. I found that

[0010]

SUMMARY OF THE INVENTION Therefore, the first object of the present invention is to provide excellent adhesion between the grain formed on the surface of an aluminum plate and the photosensitive layer, to have excellent printing durability, and to reproduce faithful tones. Another object of the present invention is to provide a positive-working photosensitive lithographic printing plate which has good properties, good reproducibility of minimum halftone dots, and is less susceptible to film edge marks because of no deterioration in sensitivity.

A second object of the present invention is to provide a positive-working photosensitive lithographic printing plate which can suppress the coloring of the support at a low concentration, can obtain an excellent visible image property of exposure, and has a good plate inspection property. To do.

A third object of the present invention is to use an ultraviolet absorbing pigment in combination with an alkali aqueous solution-soluble or alkali aqueous solution swelling compound to reduce residual color, increase image contrast and provide excellent erasing workability. , In addition, the residual pigment film can be removed from the plate with ink tack,
An object of the present invention is to provide a positive photosensitive lithographic printing plate in which background stains due to a residual film do not occur on a printed matter.

[0013]

The above objects of the present invention are: (1) The surface of an aluminum plate which has been roughened and then anodized is treated with a solution containing an ultraviolet absorbing pigment having a maximum light absorption wavelength in the range of 340 to 450 nm. A positive photosensitive composition comprising a positive photosensitive composition layer containing an o-quinonediazide compound after being colored so that the light absorptance at the wavelength of maximum light absorption is 0.01 or higher. Sex lithographic printing plate. (2) The positive photosensitive material according to the above (1), wherein the ultraviolet absorbing pigment is a compound insoluble in the solvent used for coating the positive photosensitive composition layer containing the o-quinonediazide compound. Planographic printing plate. (3) The positive photosensitive lithographic printing plate as described in (1) or (2) above, wherein an ultraviolet absorbing pigment and an alkali aqueous solution-soluble or alkali aqueous solution swelling compound are used for coloring the surface of the aluminum plate. Can be achieved by

The present invention will be described in detail below.

First, the ultraviolet absorbing pigment having a maximum light absorption wavelength in the range of 340 to 450 nm of the present invention will be described.

The ultraviolet absorption pigment has a maximum light absorption wavelength of 34
Although any wavelength may be used as long as it is in the range of 0 to 450 nm, it is preferable that the maximum wavelength of light absorption is on the shorter wavelength side (which does not adversely affect the exposed visible image). Further, the ultraviolet absorbing pigment is preferably a compound insoluble in the solvent used for coating the positive photosensitive composition layer containing the o-quinonediazide compound.

Typical examples of the ultraviolet absorbing pigment that can be used in the present invention include β-naphthol monoazo pigments, naphthol AS monoazo (disazo) pigments, acetanilide monoazo pigments and acetanilide disazo as organic pigments. Examples thereof include pigments, pyrazolone-based monoazo pigments, disazo pigments, condensed azo pigments, and the like, and examples of inorganic pigments include yellow lead, titanium yellow, cadmium yellow, zinc white, and the like.

Among the above ultraviolet absorbing pigments, benzidine yellow (acetanilide type monoazo organic pigment) and titanium yellow (inorganic pigment) are particularly preferable.

The average particle size of the ultraviolet absorbing pigment is not particularly limited, but an average particle size of 0.5 μm or less is preferable.

In the present invention, the ultraviolet absorbing pigment may be used alone or in combination of two or more kinds.

The solution containing the ultraviolet absorbing pigment used for coloring the surface of the aluminum plate contains the ultraviolet absorbing pigment,
For example, water, an organic solvent (for example, methyl ethyl ketone,
It can be obtained by dispersing in a solvent such as methanol).

The pH of the solution containing the ultraviolet absorbing pigment is p
It is preferably in the range of H2.5 to 8.0.

The coating amount of the ultraviolet absorbing pigment is 0.5.
It is preferably g / m ² or less. In addition, in terms of light absorptance of 340 to 450 nm, it is 0.02 as compared with the case of not coloring.
It is preferable to color it so that it becomes 0.5 higher.

The compound soluble in alkaline aqueous solution or swellable in alkaline aqueous solution used in combination with the ultraviolet absorbing pigment is p
Dissolved in alkaline solution of H8.0-pH13 or p
A compound that swells in an alkaline aqueous solution having a pH of 8.0 to 13 and is, for example, a novolac resin, a vinyl resin, a polymer latex described in JP-A-4-328748, an alkali-soluble starch that is a water-soluble polymer. , Gelatin, hydroxypropyl cellulose, carboxymethyl cellulose and the like, and inclusion compounds such as cyclodextrin described in JP-A-5-17333. Examples of the novolac resin or vinyl polymer resin include the novolac resin and vinyl resin described later.

As the vinyl resin, polyvinyl alcohol, carboxyvinyl polymer and the like are preferable.

Hydroxypropyl cellulose is particularly preferable as the alkali aqueous solution-soluble or alkali aqueous solution swellable compound used in combination with the ultraviolet absorbing pigment used in the present invention.

In the present invention, the compounds which are soluble in the alkaline aqueous solution or swellable in the alkaline aqueous solution may be used alone or in combination of two or more kinds.

The compound soluble in the alkali aqueous solution or swellable in the alkali aqueous solution is 0.01% to 5% in the solution containing the ultraviolet absorbing pigment used for coloring the surface of the aluminum plate.
It is preferable to contain 0% by weight.

For coating the solution containing the ultraviolet absorbing pigment, a conventionally known coating method such as a dip method, a roll call method or a bar code method can be used.

Next, the o-quinonediazide compound used in the positive photosensitive composition layer of the present invention will be described.

The orthoquinonediazide compound is a compound having an orthoquinonediazide group in the molecule, and the orthoquinonediazide compound that can be used in the present invention is not particularly limited, and examples thereof include o-naphthoquinonediazide compounds, Examples thereof include ester compounds of a polycondensation resin of o-naphthoquinonediazide sulfonic acid with phenols and aldehydes or ketones.

Examples of the phenols in the polycondensation resin with the above-mentioned phenols and aldehydes or ketones include phenol, o-cresol, m-cresol,
Examples include monohydric phenols such as p-cresol, 3,5-xylenol, carvacrol, thymol, dihydric phenols such as catechol, resorcin, and hydroquinone, and trihydric phenols such as pyrogallol and phloroglucin. Examples of the aldehyde include formaldehyde,
Examples thereof include benzaldehyde, acetaldehyde, crotonaldehyde, furfural and the like. Of these, preferred are formaldehyde and benzaldehyde. Examples of ketones include acetone and methyl ethyl ketone.

Specific examples of polycondensation resins with phenols and aldehydes or ketones include phenol-formaldehyde resin, m-cresol-formaldehyde resin, m- and p-mixed cresol-formaldehyde resin, resorcin-benzaldehyde resin, Examples include pyrogallol / acetone resin.

In the o-naphthoquinonediazide compound, the condensation rate of o-naphthoquinonediazide sulfonic acid with respect to the OH groups of phenols (reaction rate with respect to one OH group) is preferably 15% to 80%, more preferably 2%.
It is 0% to 45%.

Further, as the orthoquinonediazide compound used in the present invention, the following compounds described in JP-A-58-43451 can also be mentioned. That is, for example, 1,2-benzoquinone diazide sulfonic acid ester, 1,2-naphthoquinone diazide sulfonic acid ester, 1,2-benzoquinone diazide sulfonic acid amide,
Known 1,2-quinonediazide compounds such as 1,2-naphthoquinonediazide sulfonic acid amide, and more specifically, J. Kosar's "Light-
Sensitive Systems "(Light-Sensi
three Systems, pages 339-352 (19)
1965, John Willie and Sons (Joh
n Willey & Sons (New York)
And W S D Forest (WS De
Forest) "Photoresist" (Photor)
Esist) Volume 50 (1975), 1,2-benzoquinonediazide-4-sulfonic acid phenyl ester, 1,2,1 ', 2'-di-, described in McGraw Hill, Inc. (New York). (Benzoquinonediazide-4-sulfonyl) -dihydroxybiphenyl, 1,2-benzoquinonediazide-4- (N
-Ethyl-N-β-naphthyl) -sulfonamide, 1,
2-naphthoquinonediazide-5-sulfonic acid cyclohexyl ester, 1- (1,2-naphthoquinonediazide-
5-sulfonyl) -3,5-dimethylpyrazole, 1,
2-naphthoquinonediazide-5-sulfonic acid-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-sulfonic acid-2,4-dihydroxybenzophenone ester, 1,2-naphthoquinonediazide-5-sulfonic acid-2,3,4-trihydroxybenzophenone ester, condensation of 2 mol of 1,2-naphthoquinonediazide-5-sulfonic acid chloride and 1 mol of 4,4'-diaminobenzophenone 1,2-naphthoquinonediazide-5
A condensate of 2 mol of sulfonic acid chloride and 1 mol of 4,4'-dihydroxy-1,1'-diphenylsulfonic acid,
1,2-naphthoquinonediazide-5-sulfonic acid chloride 1 mol condensate with purpurogallin 1 mol, 1,2-
A 1,2-quinonediazide compound such as naphthoquinonediazide-5- (N-dihydroabietyl) -sulfonamide can be exemplified. In addition, Japanese Examined Japanese Patent Publication 37-19
No. 53, No. 37-3627, No. 37-13109,
40-26126, 40-4001, 45-
No. 5604, No. 45-27345, No. 51-1301
3, JP-A-48-96575 and 48-63802.
No. 1,2-described in each publication of the same No. 48-63803
A quinonediazide compound can also be mentioned.

Of the above orthoquinonediazide 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.

In the present invention, as the orthoquinonediazide compound, the above compounds may be used alone or in combination of two or more kinds.

The content of the orthoquinonediazide compound in the photosensitive composition is preferably 5 to 60% by weight, and particularly preferably 10 to 50% by weight.

To the photosensitive composition forming the photosensitive layer of the present invention, it is preferable to further add an alkali-soluble resin in order to enhance film strength and alkali solubility.

The alkali-soluble resin that can be used in the present invention is not particularly limited, and examples thereof include novolac resins, vinyl polymers having a phenolic hydroxyl group, and those described in JP-A-55-57841. Examples thereof include condensation resins of polyphenols with aldehydes or ketones.

Examples of the novolak resin which can be used in the present invention include phenol / formaldehyde resin, cresol / formaldehyde resin, JP-A-55.
-57841, a phenol-cresol-formaldehyde copolymer resin, as described in JP-A-55-127553.
Copolymer resins of substituted phenol and phenol or cresol and formaldehyde can be used.

The molecular weight (polystyrene standard) of the novolac resin is preferably 3.00 × 10 in terms of number average molecular weight Mn.
^{2 to} 7.50 × 10 ³ , weight average molecular weight Mw of 1.00 ×
10 ^{3 to} 3.00 × 10 ⁴ , more preferably Mn of 5.0
0 × 10 ^{2 to} 4.00 × 10 ³ , Mw of 3.00 × 10 ^3.
˜2.00 × 10 ⁴ .

The above novolak resins may be used alone or in combination of two or more kinds.

The novolac resin is contained in the photosensitive composition in an amount of 5 to 9
It is preferable to contain 5% by weight.

The vinyl polymer having a phenolic hydroxyl group is a polymer having a unit having the phenolic hydroxyl group in its molecular structure and is represented by the following general formula [I] to general formula [V]. Polymers containing at least one structural unit are preferred.

[0046]

[Chemical 1]

In the general formulas [I] to [V], 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, and preferably a hydrogen atom.
A represents an alkylene group, which connects a nitrogen atom or an oxygen atom and an aromatic carbon atom, and may have a substituent,
m represents an integer of 0 to 10, and B represents a phenylene group which may have a substituent or a naphthylene group which may have a substituent.

The vinyl polymer having a phenolic hydroxyl group used in the present invention preferably has a copolymer type structure having the structural units represented by the above general formulas [I] to [V], As the monomer to be copolymerized,
For example, ethylene, propylene, isobutylene, butadiene, isoprene and other ethylenically unsaturated offylenes,
For example, styrenes such as styrene, α-methylstyrene, p-methylstyrene, and p-chlorostyrene, for example,
Acrylic acids such as acrylic acid and methacrylic acid, for example,
Itaconic acid, maleic acid, unsaturated aliphatic dicarboxylic acids such as maleic anhydride, for example, methyl acrylate, ethyl acrylate, acrylate n-butyl, isobutyl acrylate, dodecyl acrylate, 2-chloroethyl acrylate, Phenyl acrylate, α-methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, esters of α-methylene aliphatic monocarboxylic acid such as ethyl ethacrylate, for example, acrylonitrile, nitriles such as methacrylonitrile, for example, acrylamide. Amides such as, for example, acrylanilide, p-chloroacrylanilide, m-nitroacrylanilide, m-
Anilides such as methoxyacrylanilide, for example, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl esters such as 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, for example, 1-methyl-1-methoxyethylene, 1,1-dimethoxyethylene, 1,2-dimethoxyethylene, 1,1-dimethoxycarbonylethylene, 1-methyl-1-nitro Ethylene derivatives such as ethylene, for example, N-vinyl-based monomers such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidene and N-vinylpyrrolidone. These monomers are present in the polymer compound in a structure in which the unsaturated double bond is cleaved.

Among the above-mentioned monomers, aliphatic monocarboxylic acid esters and nitriles exhibit excellent performance for the purpose of the present invention and are preferable.

These monomers may be bonded to the polymer used in the present invention in either a block or random state.

The vinyl polymer having a phenolic hydroxyl group is preferably contained in the photosensitive composition in an amount of 0.5 to 70% by weight.

As the vinyl polymer having a phenolic hydroxyl group, 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.

The positive type photosensitive composition layer containing the o-quinonediazide compound of the present invention is coated on a support with a coating solution prepared by dissolving or dispersing the positive type photosensitive composition containing the o-quinonediazide compound in a solvent. And then dried.

Examples of the solvent that can be used for dissolving the photosensitive composition include, for example, 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 dimethyl ether, dipropylene glycol methyl ethyl ether, ethyl formate, propylic acid formate , Butyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate,
Examples thereof include ethyl butyrate, dimethylformamide, dimethylsulfoxide, dioxane, acetone, methylethylketone, cyclohexanone, methylcyclohexanone, diacetone alcohol, acetylacetone, and γ-butyrolactone. These solvents may be used alone or in admixture of two or more.

The coating method used for coating the photosensitive composition is a conventionally known method, for example, spin coating, wire bar coating, dip coating, air knife coating, spray coating, air spray coating, electrostatic air spray. Methods such as coating, roll coating, blade coating and curtain coating are used. At this time, the coating amount depends on the application,
For example, a coating amount of 0.05 to 5.0 g / m ² is preferable as the solid content.

To the photosensitive composition containing the o-quinonediazide compound of the present invention, a visible image forming agent capable of forming a visible image upon exposure can be added in order to enhance the exposure visible imageability.

The visible agent is composed of a compound which forms an acid or a free radical upon exposure to light and an organic dye which changes its color tone by interacting with the generated acid or a free radical. Examples of the compound that produces the compound include, for example, o-naphthoquinonediazide-4-sulfonic acid halogenide described in JP-A-50-36209, trihalomethyl-2-pyrone and trihalogen described in JP-A-53-36223. Methyl-triazine, ester compound or amide compound of o-naphthoquinonediazide-4-sulfonic acid chloride described in JP-A-55-6244 and a phenol or aniline having an electron-withdrawing substituent, JP-A-55- 77742
Examples thereof include halomethylvinyloxadiazole compounds and diazonium salts described in JP-A No. 57-148784 and the like, and as the organic dye,
For example, Victoria Pure Blue BOH (Hodogaya Chemical Co., Ltd.), Patent Pure Blue (Sumitomo Mikuni Chemical Co., Ltd.), Oil Blue # 603 (Orient Chemical Co., Ltd.), Sudan Blue II (BASF), Crystal violet, malachite green, fuchsin,
Methyl violet, ethyl violet, methyl orange, brilliant green, congo red, eosin, rhodamine 66 and the like can be mentioned.

The visible image agents described in JP-A-55-3207 and JP-A-60-88942 can be preferably used in the present invention.

To the photosensitive composition containing the o-quinonediazide compound of the present invention, a plasticizer, a surfactant, an organic acid, an acid anhydride, etc. may be added, if necessary, in addition to the above materials. You can

Further, the photosensitive composition containing the o-quinonediazide compound of the present invention may contain, for example, p-tert-butylphenol formaldehyde resin, pn-, in order to improve the oil sensitivity of the photosensitive composition. Octylphenol formaldehyde resin or these resins
A resin partially esterified with a quinonediazide compound may be added.

The photosensitive composition layer containing the o-quinonediazide compound of the present invention has a maximum light absorption wavelength of 34.
It is preferable not to use a dye near 0 to 450 nm.

Next, the support used in the photosensitive lithographic printing plate of the present invention will be described.

The support preferably has flexibility so that it can be set in an ordinary printing machine and can withstand a load applied during printing. For example, a metal plate of aluminum, magnesium, zinc, chromium, iron, copper, nickel or the like, An alloy plate of these metals, or a metal plate coated with chromium, zinc, copper, nickel, aluminum, iron or the like by plating or vapor deposition can be used. Of these, the support is preferably one using aluminum or its alloy.

Various kinds of aluminum alloys can be used, for example, silicon, copper, manganese, magnesium,
Examples include alloys of metals such as chromium, zinc, lead, bismuth, and nickel with aluminum.

The support made of aluminum or its alloy or the like is usually subjected to a degreasing treatment prior to the graining treatment in order to remove oil and fat components such as rolling oil adhering to the surface of the support. As the degreasing treatment, degreasing treatment using a solvent such as trichlene and thinner, emulsion degreasing treatment using an emulsion of kesilon and triethanol, and the like are used. In addition, an alkaline aqueous solution such as caustic soda can be used for the degreasing treatment. When an alkaline aqueous solution such as caustic soda is used for the degreasing treatment, it is possible to remove stains and oxide films which cannot be removed only by the above degreasing treatment.

The graining treatment (roughening treatment) of the present invention is
So-called mechanical surface-roughening method for mechanically roughening the surface, so-called chemical surface-roughening method for chemically selective surface melting to roughen the surface, so-called electrochemical surface-roughening for the surface electrochemically It can be performed using a known method such as a surface roughening method.

Mechanical graining methods include, for example, ball polishing, brush polishing, blast polishing, buff polishing, etc., and electrochemical graining methods include hydrochloric acid, nitric acid, etc. There is a method of electrolytically treating with an alternating current or a direct current in an electrolytic solution containing the same.

The graining treatment of the present invention can be carried out by any one of these methods or by using two or more methods in combination, but in the present invention, since the residual film is reduced, electrochemical treatment is carried out. It is preferable to perform graining treatment by a roughening method.

Since smut is formed on the surface of the support obtained by the graining treatment, it is generally preferable to appropriately perform washing with water or alkali etching in order to remove the smut. Examples of such a treatment include the alkali etching method described in Japanese Patent Publication No. 48-28123 and JP-A No. 53-12739.
Examples thereof include a treatment method such as a sulfuric acid desmutting method described in Japanese Patent Publication No. 1994-242242.

The support treated as described above is then anodized. Wear resistance due to anodizing treatment,
The chemical resistance and water retention can be improved. A known method can be used for the anodizing treatment. For example, a method of electrolyzing with an aqueous solution containing sulfuric acid and / or phosphoric acid or the like at a concentration of 10 to 50% at a current density of 1 to 10 A / dm ² is used. It is preferably used, but is not limited to US Pat.
No. 4,511,66, and a method of electrolyzing in sulfuric acid at a high current density described in US Pat. No. 3,511,66.
It is also possible to use the method of electrolyzing with phosphoric acid described in No. 1 specification.

The anodized support may be sealed if necessary. These sealing treatments can be performed by using known methods such as hot water treatment, boiling water treatment, steam treatment, sodium silicate treatment, dichromate aqueous solution treatment, and nitrite treatment.

It is preferable that the support is further provided with a hydrophilic layer. For the formation of the hydrophilic layer, US Pat.
Alkali metal silicates described in US Pat. No. 1,461, hydrophilic celluloses described in US Pat. No. 1,860,426, JP-A-60-149491 and JP-A-63.
-165183 gazette amino acid and its salt,
Hydroxyl group-containing amines and salts thereof described in JP-A-60-232998, phosphates described in JP-A-62-19494, and monomers having a sulfo group described in JP-A-59-101651. A polymer compound containing a unit can be used.

The positive-working photosensitive lithographic printing plate of the present invention can be made into a plate by exposing and developing it in a usual manner. For example, a transparent original image having a line image, a halftone dot image, etc. is brought into close contact with the photosensitive surface for exposure, and then the photosensitive layer in the non-image area is removed using an appropriate developing solution to obtain a relief image. .

Suitable light sources for exposure include mercury lamps, metal halide lamps, xenon lamps, chemical lamps,
Examples include carbon arc lamps. The developer used for development is preferably an aqueous alkali solution, and examples thereof include alkali metal silicates such as sodium silicate and potassium silicate, sodium hydroxide, potassium hydroxide, sodium triphosphate, and dibasic sodium phosphate. An aqueous alkaline solution such as an aqueous solution of sodium carbonate, potassium carbonate or the like can be used. The concentration of the alkaline aqueous solution at this time varies depending on the type of the photosensitive composition and the alkali,
Generally, a range of 0.1 to 10% by weight is suitable. Also,
If necessary, an organic solvent such as a surfactant or alcohol may be added to the alkaline aqueous solution.

[0075]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 [Preparation of support] An aluminum plate (material 1050, temper H16) having a thickness of 0.24 mm was kept at 60 ° C. for 5 minutes.
After degreasing treatment in an aqueous solution of sodium hydroxide of 1 wt% for 1 minute, in an aqueous solution containing 0.5 mol of hydrochloric acid in 1 liter, the temperature was 25 ° C. and the current density was 60 A / d.
The electrolytic etching treatment was performed under the conditions of m ² and a treatment time of 30 seconds. Then, 6% in 5% by weight sodium hydroxide aqueous solution
After performing desmutting treatment at 0 ° C. for 10 seconds, in a 20 wt% sulfuric acid solution, the temperature was 20 ° C., the current density was 3 A / dm ² ,
Anodizing treatment is performed under the condition that the treatment time is 1 minute.
A hot water sealing treatment was performed with hot water at 0 ° C. for 20 seconds to prepare a support 1.

A coating liquid having a composition shown in Table 1 prepared by dispersing it on a support 1 was applied with a wire bar at a coating amount shown in Table 1, and 90
Supports 2 to 6 were produced by drying at 2 ° C. for 2 minutes.

The maximum light absorption wavelength (peak max) of the obtained support and the wavelength of 400 n obtained by applying the coating solution
The increase in light absorptance (ΔAbs) at m was as shown in Table 1.

To measure the maximum wavelength of light absorption and the light absorption rate,
A spectrophotometer U-3210 (manufactured by Hitachi Ltd.) was used.

[0080]

[Table 1] [Application of Photosensitive Composition Coating Liquid] Support 1 Obtained Above
The following photosensitive composition coating liquids were applied to Nos. 6 to 6 using a wire bar and dried at 90 ° C. for 1 minute to prepare photosensitive planographic printing plate samples 1 to 6. At this time, the coating amount of the photosensitive composition was set to be 2.0 g / m ² as a dry weight.

<Photosensitive Composition Coating Liquid> Novolac resin (phenol / m-cresol / p-cresol molar ratio is 10/54/36 and Mw is 40,000) 6.7 g o-naphthoquinonediazide compound (pyrogallolacetone resin Condensate of Mw3000 and o-naphthoquinonediazide-5-sulfonyl chloride: esterification rate 30%) 1.5 g Polyethylene glycol # 2000 0.2 g Victoria Pure Blue BOH (manufactured by Hodogaya Chemical Co., Ltd.) 0.08 g 2, 4-bis (trichloromethyl) -6- (p-methoxystyryl) -s-triazine 0.15 g FC-430 (Sumitomo 3M Ltd.) 0.03 g cis-1,2-cyclohexanedicarboxylic acid 0.2 g Methyl cellosolve 100 ml Photosensitive lithographic printing plate samples 1 to 6, Step tablet for sensitivity measurement (Eastman Kodak Co., Ltd. No. 2,
21 steps of gray scale with a density difference of 0.15 each and Brunner small dots (check the reproducibility of small dots at halftone dot area 0.5 to 5%). It was exposed from a distance for 20 seconds. Next, the exposed photosensitive lithographic printing plate was treated with a developer obtained by diluting SDR-1 (manufactured by Konica Corp.) developer 6 times with water at 27 ° C.
And developed for 20 seconds.

<Evaluation of Sensitivity> The number of gray scale steps that completely clear the obtained gray scale phenomenon image was determined, and the sensitivity was evaluated by the number of steps. The larger the number of stages, the higher the sensitivity.

<Evaluation of reproduction of small dots> The Brunner small dots on the plate of the obtained lithographic printing plate were visually observed for the completely reproduced halftone dot area using a magnifying glass having a magnification of 25 times.

<Evaluation of printing durability> The obtained lithographic printing plate was printed with a printing machine (GTO manufactured by Heidel Co.), a coated paper printing ink (High Plus M red manufactured by Toyo Ink Mfg. Co., Ltd.) and a fountain solution (SEU- 3; 2.5%, using Konica Corp.) to print, and continue to print until the solid part of the image part of the printed matter appears defective in ink, or ink is inked in the non-image area, The number of prints at that time was counted.

<Evaluation of residual color> The completely clear portion of the obtained gray scale phenomenon image was observed and the residual color was visually evaluated.

<Evaluation of Visibility of Exposure Visibility> When the photosensitive lithographic printing plate exposed by closely contacting the step tablet for sensitivity measurement was developed under the above-mentioned developing conditions, it was exposed under the exposure condition where 4 clear steps were obtained. The difference in optical density (ΔD) between the exposed layer and the unexposed portion of the photosensitive lithographic printing plate was measured using PDA65.
It measured using the visual filter (made by Konica Corporation).

The results are shown in Table 2.

[0088]

[Table 2]

[0089]

The positive-working photosensitive lithographic printing plate of the present invention has excellent adhesion between the photosensitive layer and the grain formed on the surface of the aluminum plate, has excellent printing durability, and has a faithful tone. It has reproducibility, good reproduction of minimum halftone dots, film edge marks are less likely to occur because sensitivity is not reduced, and it is possible to suppress the coloring of the support to a low density, and obtain excellent exposure visibility. Good plate inspection. Furthermore, by using a UV-absorbing pigment in combination with an alkali aqueous solution-soluble or alkali aqueous solution swelling compound, the residual color is reduced, the image contrast is high, and the erasing workability is very excellent. Since it can be removed from the plate with, the background film does not cause background stain.

Front page continued (72) Inventor Shinichi Matsubara 1 Sakura-cho, Hino-shi, Tokyo Konica stock company (72) Inventor Mitsuru Sasaki 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd. (72) ) Inventor Daisuke Kanazawa 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd.

Claims (3)

[Claims] 1. The surface of an aluminum plate that has been roughened and then anodized is treated with a solution containing an ultraviolet absorbing pigment having a maximum light absorption wavelength in the range of 340 to 450 nm so that the light absorption coefficient at the maximum light absorption wavelength is increased. A positive-working photosensitive lithographic printing plate comprising a positive-working photosensitive composition layer containing an o-quinonediazide compound, which has been colored to a level of 0.01 or more. 2. The positive photosensitive material according to claim 1, wherein the ultraviolet absorbing pigment is a compound which is insoluble in the solvent used for coating the positive photosensitive composition layer containing the o-quinonediazide compound. Sex lithographic printing plate. 3. The positive photosensitive lithographic printing plate as claimed in claim 1, wherein an ultraviolet absorbing pigment and an alkali aqueous solution-soluble or alkali aqueous solution swelling compound are used for coloring the surface of the aluminum plate.