JPH11240266A - Lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a printing soil from being generated even during a long term storage, and hardly make a flaw by a handling applied for the completion of a gum-application by a method wherein on a metal supporting body having a hydrophilic face, an undercoat layer comprising a water-soluble compound, and a water-insoluble and photo-insensitive resin layer are provided. SOLUTION: In this lithographic printing plate, on a metal supporting body having a hydrophilic face, an undercoating of a water-soluble compound is applied. Then, continuing to the undercoat layer, a water-insoluble photo- insensate resin layer is provided. To the photo-insensitive resin layer, various kinds of additives, e.g. a coloring matter to discriminate the applied layers, a plasticizer or a low molecular oxide compound for the promotion of a dissolution, an applied surface quality improving agent such as a fluorine based interfacial active agent, and a matting agent for surface-matting or the like can be added. Then, it is preferable to provided a mat layer which is constituted of protuberances being provided independently from each other, on the non-photo- sensitive layer. The purposes of the mat layer are for an effect to improve a hard-to-damage property, and to prevent plate materials from sticking to each other when the plate materials are stored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate, and more particularly to a discarded lithographic printing plate used in a multicolor printing apparatus as a preferred mode of use. The discard system is described in detail in JP-A-3-175090.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 3-175090 discloses P
It is described that when the photosensitive layer of the S plate was entirely removed and the plate was discarded, the photosensitive layer could not be completely removed and printing stains occurred. Further, as a method for solving this problem, a discarding plate in which a protective film for preventing ink adhesion is provided on a base on which a photosensitive layer has not been applied has been proposed. However, such a discarded plate provided with a protective film in advance,
At the start of printing, there is a disadvantage that the number of prints (usually referred to as black loss) required to completely remove undesired ink adhered increases, and is completely accepted by the market. Not. The reason for the increase in black loss is that the protective film is usually much larger than the gumming amount of the PS plate so that printing stains do not occur even when stored for a long period of time. This is due to deterioration of solubility. For this reason, a base provided with no protective film at all is supplied from a PS plate maker to the market, and this base is used just before printing, subjected to the same hydrophilic treatment and gumming as the PS plate.
A disadvantage of such a non-applied plate is that printing stains are likely to occur due to various kinds of contamination during long-term storage. Furthermore, by handling until the gumming is completed,
It is easy to be scratched.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent printing stains from occurring even when stored for a long period of time, to prevent scratches due to handling until gumming is completed, and to allow handling under white light. To provide a lithographic printing plate.

[0004]

The above objects of the present invention have been attained by the following inventions. 1. A lithographic printing plate comprising a metal support having a hydrophilic surface, and an undercoat layer made of a water-soluble compound and a water-insoluble non-photosensitive resin layer provided on the metal support. 2. Item 4. The lithographic printing plate according to Item 1, wherein the undercoat layer is a water-soluble polymer having a sulfonic acid group. 3. Item 3. The lithographic printing plate according to Item 1 or 2, wherein the non-photosensitive resin layer is a resin obtained by solubilizing polyurethane with alkali. 4. A lithographic printing plate in which a plate having an image is attached to some plate cylinders using a multicolor printing device having two or more plate cylinders, and a discarded plate for multicolor printing having no image is attached to the remaining plate cylinders. A lithographic printing method, wherein the discarded plate is a lithographic printing plate according to any one of Items 1 to 3. The effect of the present invention is achieved by providing a water-insoluble non-photosensitive resin layer on the undercoat layer of a water-soluble compound,
The undercoat layer of the water-soluble compound is used as a shielding layer to prevent contaminants causing printing stains from sticking to the surface of the hydrophilic support. This is probably due to the function of preventing scratches.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The undercoat layer of the present invention will be described. The support having a hydrophilic surface is subbed with a water-soluble compound. Examples of the water-soluble compound used in the undercoat include carboxymethylcellulose, dextrin, gum arabic, phosphonic acids having an amino group such as 2-aminoethyl phononic acid, phenylphosphonic acid optionally having a substituent, naphthylphosphonic acid, Organic phosphonic acids such as alkyl phosphonic acid, glycerophosphonic acid, methylene diphosphonic acid and ethylene diphosphonic acid, phenylphosphoric acid which may have a substituent, naphthyl phosphoric acid, organic phosphoric acid such as alkyl phosphoric acid and glycerophosphoric acid, Organic phosphinic acids such as phenylphosphinic acid, naphthylphosphinic acid, alkylphosphinic acid and glycerophosphinic acid which may have a substituent, amino acids such as glycine and β-alanine, and hydroxyl groups such as triethanolamine hydrochloride To Hydrochloride salt of an amine, a water-soluble polymer and the like having a sulfonic acid group is preferably used, water-soluble polymer having a Above all sulfonic acid groups are particularly preferred.

A water-soluble polymer having a sulfonic acid group is a water-soluble polymer compound containing at least one monomer unit having a sulfonic acid group as a repeating unit in a molecule. Column 3, line 22-
Column 4, line 41). As the monomer unit having a sulfonic acid group, for example, p-styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, ethylenesulfonic acid and the like are preferable, and one or two or more of these are selected and polymerized. Or copolymerized with other monomers. When copolymerized with another monomer, the partner monomer may be any monomer as long as it can be copolymerized with a monomer having a sulfonic acid group. Specific examples include, for example, methyl methacrylate / ethyl acrylate / 2-acrylamide-2-methylpropane sodium sulfonate, methyl methacrylate /
Methyl acrylate / sodium p-styrenesulfonate, sodium polystyrenesulfonate and the like. The molecular weight range of the water-soluble compound of the present invention is not limited as long as it is water-soluble, but if a general standard is shown, a weight average molecular weight of about 1,000 to 1,000,000 is appropriate, preferably 2,000 to 100,000, and most preferably. Is in the range of 10,000 to 100,000.

The undercoat layer is formed by dissolving the above compound in water, methanol, ethanol, isopropyl alcohol, methyl ethyl ketone or the like or a mixed solvent thereof,
It can be provided by coating and drying on a support. Coating layer after drying of the undercoat layer is, 10 to 500 mg / m ² are suitable, preferably 50-200 mg / m ^2. 1 undercoat layer
When the amount is less than 0 mg / m ^{2, the} ability to prevent printing stains is insufficient. When the amount of the undercoat layer is more than 500 mg / m ^2, the film strength of the non-photosensitive resin layer to be applied later decreases, and the ability to prevent scratches due to handling decreases.

Following the undercoat layer, a water-insoluble non-photosensitive resin layer is provided. Preferred as the resin is an acid content of 0.1 to 3.0 meq / g, preferably 0.2 to 2.0 meq / g.
g, which is a substantially water-insoluble (ie, insoluble in a neutral or acidic aqueous solution), film-forming organic polymer compound, but preferably a compound capable of dissolving or swelling in an alkaline aqueous solution. In addition, acid content 0.1meq / g
If it is less than 3.0 meq / g, the strength of the film becomes extremely weak especially when stored at high temperature and high humidity. The molecular weight of the non-photosensitive resin is not limited as long as it dissolves in a coating solvent and dissolves or swells in an aqueous alkali solution, but the weight average molecular weight is 1,000 to 1,000,000, preferably 1,000.
0 to 500,000. When the molecular weight is low, the film strength is low, and when the molecular weight is high, the solubility is deteriorated.

Particularly preferred non-photosensitive resins include copolymers containing acrylic acid, methacrylic acid, crotonic acid or maleic acid as essential components, for example, JP-A-50-1188.
Multi-component copolymerization with 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, acrylonitrile or methacrylonitrile, acrylic acid or methacrylic acid and optionally other copolymerizable monomers as described in JP-A-02 Coupling, JP-A-53-12
Acrylic or methacrylic acid, acrylic acid, or methacrylic acid whose terminal is a hydroxy group and esterified with a group containing a dicarboxylic acid ester residue as described in JP-A-0903 Multi-component copolymer with copolymerizable monomer, JP-A-54-986
No. 14, a monomer having an aromatic hydroxyl group at its terminal (for example, N- (4-hydroxyphenyl) methacrylamide, etc.), acrylic acid or methacrylic acid and, if necessary, other copolymers Examples include a multi-component copolymer with a possible monomer, and a multi-component copolymer comprising an alkyl acrylate, acrylonitrile or methacrylonitrile and an unsaturated carboxylic acid as described in JP-A-56-4144. In addition, acidic polyvinyl alcohol derivatives and acidic cellulose derivatives are also useful. Japanese Patent Publication No. 54-19773 in which polyvinyl acetal or polyurethane is alkali-solubilized,
JP-A-57-94747 and JP-A-60-182437,
The binders described in JP-A-62-58242 and JP-A-62-123453 are also useful, and a resin obtained by solubilizing polyurethane with alkali is particularly preferable because of its high film strength.

The non-photosensitive resin layer composition is dissolved in various known coating solvents, and has a dry coating weight of 0.2 to 3.0 g / m ² on an aluminum support having a hydrophilic surface and an undercoat layer. In this case, it is preferably applied so as to have a thickness of 0.3 to 1.5 g / m ² and dried to obtain a discarded plate for lithographic printing. If the coating amount is less than 0.2 g / m ² , the ability to prevent scratches is insufficient, and if it is 3.0 g / m ² or more, the ability to prevent scratches is sufficient, and the dissolution speed at the time of dissolving and removing may decrease. As a result, the processing ability of the solution is reduced. The solid content concentration of the resin layer composition at the time of application is suitably from 1.0 to 50% by weight, preferably from 2.0 to 30% by weight. As a method of applying the resin composition on the support, conventionally known methods, for example, roll coating, bar coating,
Methods such as spray coating, curtain coating, and spin coating can be used. The applied resin layer composition solution is preferably dried at 50 to 150 ° C.
As a drying method, after preliminarily drying at a lower temperature, drying may be performed at a high temperature or directly at a high temperature.

In the non-photosensitive resin layer, various additives, for example, a dye for determining a coating layer, a plasticizer or a low molecular acid compound for accelerating dissolution, an improvement in coating surface quality such as a fluorine-based surfactant, etc. And a matting agent for surface matting can be added. In particular, dipicolinic acid, malic acid,
Low molecular acid compounds containing a carboxylic acid group or a sulfonic acid group, such as sulfosalicylic acid, sulfophthalic acid, and tricarballylic acid, are preferred because they have a dissolution accelerating action and an action of preventing printing stains during long-term storage. In addition, a fluorine-based surfactant is preferable because it has an effect of improving not only the quality of the coated surface but also the effect of preventing scratches. The low molecular acid compound is added in an amount of 1 to 20% by weight and the fluorine-based surfactant is added in an amount of 0.1 to 5% by weight based on the non-photosensitive resin layer.

It is preferable to provide a mat layer composed of protrusions provided independently of each other on the non-photosensitive layer. The purpose of the mat layer is to improve the resistance to scratching and to prevent the plate materials from adhering to each other during storage of the plate material. As a method for applying the mat layer, Japanese Patent Laid-Open No. 55-1
No. 2974, a method of heat-sealing powdered solid powder, and a method of spraying and drying polymer-containing water described in JP-A-58-182636. Can also be used. The mat layer is desirably dissolved in an alkaline aqueous solution for removing the resin layer, or made of a substance that can be removed by the solution.

The metal support having a hydrophilic surface includes:
Aluminum and an aluminum-coated composite support are preferred, with 0.1-0.5% by weight of iron, 0.03-0.3% by weight of silicon, 0.001-0.03% by weight of copper, furthermore A 1S aluminum plate containing 0.002 to 0.1% by weight of titanium is preferred. The surface of the aluminum material is desirably surface-treated for the purpose of increasing water retention. Alkali, preferably in an aqueous solution of 1 to 30% by weight of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate or the like at a temperature of 20 to 80 ° C for 5 seconds to 2 hours.
Etching may be performed by dipping for 50 seconds. Aluminum ions may be added to the etching bath in an amount of about one-fifth of alkali. Then, it is immersed in an aqueous solution of 10 to 30% by weight of nitric acid or sulfuric acid at a temperature of 20 to 70 ° C. for 5 to 25 seconds to neutralize and remove smut after alkali etching. For example, as the surface roughening method, generally known brush polishing method, ball polishing method, electrolytic etching, chemical etching, liquid honing, sand blasting and the like and combinations thereof, and preferably, brush polishing method, electrolytic etching, Chemical etching and liquid honing are mentioned, of which the surface roughening method including the use of electrolytic etching is preferred. Further, Japanese Unexamined Patent Publication No.
As described in JP-A-63902, a method of carrying out brush polishing and then electrolytic etching is also preferable.

As the electrolytic bath used in the electrolytic etching, an aqueous solution containing an acid, an alkali or a salt thereof or an aqueous solution containing an organic solvent is used. Electrolytes containing salts are preferred. For brush polishing, it is preferable to use a pamistone-water suspension and a nylon brush, and the average surface roughness is preferably 0.25 to 0.9 μm.

The electrolytic solution used in the electrolytic etching process is an aqueous solution of hydrochloric acid or nitric acid, and has a concentration of 0.01 to 3%.
%, Preferably in the range of 0.05 to
More preferably, it is 2.5% by weight. In addition, a corrosion inhibitor (or stabilizer) such as nitrate, chloride, monoamines, diamines, aldehydes, phosphoric acid, chromic acid, boric acid, ammonium oxalate, etc., if necessary, A graining agent and the like can be added. Further, the electrolyte may contain an appropriate amount (1 to 10 g / liter) of aluminum ions.

The electrolytic etching process is usually performed at 10 to 60 ° C.
At the temperature of the electrolyte. If the alternating current used at this time is one in which the positive and negative polarities are alternately exchanged,
Any of a rectangular wave, a trapezoidal wave, and a sine wave can be used, and normal commercial AC single-phase and three-phase AC currents can be used. The current density is 5 to 100 A / dm ² and 1
It is desirable to process for 0 to 300 seconds.

The surface roughness of the aluminum alloy support in the present invention is adjusted by the quantity of electricity and is 0.2 to 0.8 μm.
m. Further, the roughened aluminum plate is desmutted with an acid or alkali aqueous solution as required. The grained aluminum alloy is made of 10 to 50% by weight of hot sulfuric acid (40 to 60% by weight).
℃) or dilute alkali (such as sodium hydroxide)
The smut adhered to the surface is preferably removed and etched (preferably in the range of 0.01 to 2.0 g / m ² ). If the smut has been removed and etched with an alkali, it is subsequently neutralized by immersion in an acid (nitric acid or sulfuric acid) for cleaning.

After de-smutting the surface, an anodic oxide coating is provided. As the anodic oxidation method, a conventionally well-known method can be used, but sulfuric acid is used as the most useful electrolytic solution. Subsequently, phosphoric acid is also a useful electrolyte. Further, a mixed acid of sulfuric acid and phosphoric acid disclosed in JP-A-55-28400 is also useful.

In the sulfuric acid method, the treatment is usually performed with a direct current, but an alternating current can also be used. Sulfuric acid concentration 5-3
Electrolysis treatment is performed at 0% by weight in a temperature range of 20 to 60 ° C. for 5 to 250 seconds, and an oxide film of 1 to 10 g / m ² is provided on the surface. The electrolyte preferably contains aluminum ions. At this time, the current density is 1-2.
0 A / dm ² is preferred. In the case of the phosphoric acid method, a phosphoric acid concentration of 5 to 50% by weight and a temperature of 30 to 60 ° C. and 10 to 300%
It is processed at a current density of 1 to 15 A / dm ^{2 for} a ^second .

Further, if necessary, US Pat.
No. 14,066 and US Pat. No. 3,181,461.
Silicate (sodium silicate,
Potassium silicate) treatment, US Pat. No. 2,946,638
Potassium fluoride zirconate described in US Pat. No. 3,201,247; phosphomolybdate described in US Pat. No. 3,201,247; British Patent 1,10
No. 8,559, the alkyl titanate treatment, the German Patent 1,091,433, the polyacrylic acid treatment, and the German Patent 1,13.
No. 4,093 and British Patent No. 1,230,447, polyvinyl phosphonic acid treatment, Japanese Patent Publication No. 44-6409, phosphonic acid treatment, U.S. Pat. No. 3,307 , Phytic acid treatment described in the specification of JP-A-58-16993 and the hydrophilic organic polymer compound described in JP-A-58-181891 and divalent metals. Hydrophilic treatment can be performed by treatment with a salt. Silicate treatment is particularly preferred because of its high hydrophilizing ability and simple treatment.

As another hydrophilic treatment method, there can be mentioned silicate electrodeposition described in US Pat. No. 3,658,662. After the graining treatment and the anodic oxidation, a sealing treatment can be performed. Such a sealing treatment is performed by immersion in hot water and a hot aqueous solution containing an inorganic salt or an organic salt, a steam bath, or the like.

A lithographic printing plate having a non-photosensitive resin layer coated and dried on a support having a hydrophilic surface layer and an undercoat layer can be obtained by dissolving it with an aqueous alkali solution.

As the alkaline aqueous solution, Japanese Patent Laid-Open No. 51-7 / 1979
No. 7401, No. 51-80228, No. 53-4420
A photosensitive lithographic printing plate developer as described in JP-A Nos. 2 and 55-52054.
13. It is preferable that water contains 75% by weight or more. If necessary, an organic solvent (benzyl alcohol, ethylene glycol monophenyl ether) having a solubility in water of 10% by weight or less at room temperature, an alkali agent (triethanolamine, diethanolamine, monoethanolamine, sodium phosphate, sodium carbonate), an anionic interface Surfactants (aromatic sulfonates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, alkyl sulfates), nonionic surfactants (polyoxyethylene alcohol ether, polyoxyethylene alkyl aryl ether, polyoxyethylene) Polyoxypropylene block polymer), antifouling agents (sodium sulfite, sodium salt of sulfopyrazolone) and water softeners (ethylenediaminetetraacetic acid tetrasodium salt, nitrile triacetic acid sodium salt) Potassium salt) can be added.

However, when an organic solvent or the like is contained, toxicity during operation, sanitary problems such as odor, safety problems such as fire and gas explosion, workability problems such as generation of bubbles, pollution by waste liquid, etc. Therefore, those which do not substantially contain an organic solvent are more preferable because of the problems described above, costs, and the like. Examples of such an aqueous alkaline developer substantially free of an organic solvent include JP-A-59-84241 and JP-A-57-1929.
Developer compositions described in JP-A No. 52 and JP-A-62-24263 can be used.

The discarded lithographic printing plate of the present invention is disclosed in
No. 8002, No. 55-115045, No. 59-584
The plate-making process may be performed by the method described in each gazette of No. 31. That is, after development processing, washing with water and then desensitization processing,
Alternatively, a desensitizing treatment, a treatment with an aqueous solution containing an acid, or a treatment with an aqueous solution containing an acid may be followed by a desensitizing treatment.

Furthermore, in the developing process of this type of lithographic printing plate, an alkaline aqueous solution is consumed depending on the processing amount to reduce the alkali concentration, or the alkali concentration is reduced by air due to long-time operation of the automatic developing machine. Therefore, the processing capacity may be reduced by using a replenisher as described in JP-A-54-62004. In this case, it is preferable to replenish by the method described in U.S. Pat. No. 4,882,246.

The plate making process described above is disclosed in
It is preferably carried out with an automatic developing machine as described in JP-A-7054 and JP-A-2-32357. Examples of the desensitized gum that is applied as required in the final step of the plate making process include JP-B-62-16834 and JP-B-62-2511.
No. 8, No. 63-52600, JP-A-62-7595
And those described in JP-A-62-11693 and JP-A-62-83194 are preferred.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto. (Examples 1 to 3, Comparative Examples 1 to 5) The following discarded lithographic printing plates were prepared and used as evaluation materials. 0.30 mm thickness of JIS A1050 aluminum material containing 0.01 wt% of copper, 0.03 wt% of titanium, 0.3 wt% of iron, and 0.1 wt% of silicon in 99.5 wt% aluminum A rolled plate was prepared by using a 400 mesh 20% by weight aqueous suspension of pumicestone (manufactured by Kyoritsu Ceramics) and a rotating nylon brush (6.1).
0-nylon) and the surface is grained,
Washed well with water.

This was immersed in a 15% by weight aqueous sodium hydroxide solution (containing 4.5% by weight of aluminum) and etched so that the amount of aluminum dissolved was 5 g / m ² .
It was washed with running water. Further, the mixture was neutralized with 1% by weight of nitric acid, and then, in an aqueous solution of 0.7% by weight of nitric acid (containing 0.5% by weight of aluminum), the voltage at the time of anode was 10.5 volts and the voltage at the time of cathode was 9.
3 volt square wave alternating waveform voltage (current ratio r = 0.90,
The electrolytic surface roughening treatment was carried out using a current waveform described in Examples of JP-B-58-5796) at an anode electricity of 160 coulomb / dm ² . After washing with water, 10% by weight at 35 ° C
After being immersed in an aqueous sodium hydroxide solution and etched so that the amount of aluminum dissolved was 1 g / m ² , the substrate was washed with water. Next, it is immersed in a 30% by weight aqueous sulfuric acid solution at 50 ° C.
After desmutting, it was washed with water.

Further, a porous anodic oxide film forming treatment was carried out in a 20% by weight aqueous sulfuric acid solution (containing 0.8% by weight of aluminum) at 35 ° C. using a direct current. That is, electrolysis was performed at a current density of 13 A / dm ² , and the anodic oxide film weight was adjusted to 2.7 g / m ² by adjusting the electrolysis time. After washing the support with water, the support was added to a 3% by weight aqueous solution of sodium silicate at 70 ° C. for 30 minutes.
It was immersed for 2 seconds, washed and dried.

The aluminum support obtained as described above had a reflection density of 0.30 and a center line average roughness of 0.58 μm as measured with a Macbeth RD920 reflection densitometer. Next, methyl methacrylate / ethyl acrylate / 2-acrylamido-2-methylpropanesulfonic acid (prepared by weight ratio 65/20/15) copolymer was partially converted to a sodium salt, and 1.0% by weight methanol / A 90/10 solution was prepared in water and applied by a bar coater so that the applied amount after drying was 0.1 g / m ² .

Further, the composition shown in Table 1 was prepared by adding methanol / methyl ethyl ketone / 1-methoxy-2-propanol /
Dissolve in a mixed solvent of methyl methyl lactate = 30 g / 30 g / 25 g / 12 g and apply using a bar coater.
Dry at 0 ° C. for 45 seconds. The dry coating amount was 1.0 g / m ² .

Further, as a resin solution for forming a mat layer, a 12% by weight aqueous solution of the copolymer previously used for the undercoat layer was prepared, and the number of revolutions was 25,000 rpm and the amount of liquid sent was 4 ml by a rotary atomizing electrostatic coating machine.
/ Min, applied voltage of -90 kV, ambient environment of 25 ° C and 50% RH, steam is sprayed on the coated surface 2.5 seconds after application, and then 3 seconds after wetting, the temperature is 60 ° C and the humidity is 10% RH.
H air was blown for 5 seconds to dry. The average height of the mat is about 6 μm, the average size is about 30 μm, and the coating amount is 1
It was 50 mg / m ² .

Thereafter, in order to evaluate the printing as a discarded print, immediately after the production of the produced sheet, after storage for 3 months, and
After storage at 80 ° C. and 80% RH, DN-3C (alkali aqueous developer for negative PS plate manufactured by Fuji Photo Film Co., Ltd.) was made 1: 1 with water at 800 H (automatic developing machine manufactured by Fuji Photo Film Co., Ltd.). Elution was performed with the diluted solution, and immediately FN-2
(Gum manufactured by Fuji Photo Film Co., Ltd.) diluted 1: 1 with water was applied and dried. This discarded plate was printed on a rotary offset press using a newspaper ink of Sakata Ink Co., Ltd. and a Toyo Ink Co., Ltd. Toyo Ink fountain solution.
20,000 sheets were printed at a speed of 0 sheets / hour, and the stain condition was evaluated. Table 1 shows the results.

[0035]

[Table 1]

In Table 1, the meanings of ○, ○ △, ×, XX are as follows. ：: Not generated at all ○ △: Almost not generated ×: Very poor XX: Extremely poor

In Examples 1 to 3, good results were obtained as discarded plates for lithographic printing. In particular, Example 1 is difficult to scratch,
Good storage stability is preferable. On the other hand, the black loss of Comparative Example 1 was very poor. Comparative Example 2 was an uncoated plate, but was very easily scratched, and wrinkle-like stains on the interleaf occurred when stored over the interleaf. Comparative Examples 4 and 5 are PS plates, but Example 1 has better results. In the case of the PS plate, fogging occurs when handled and stored under a white light. However, in the present invention, since it is non-photosensitive, there is no problem even when handled and stored under a white light. In Comparative Example 3 in which the diazo resin was removed from Comparative Example 4, the background was stained immediately after the preparation without aging, whereas in Example 1 in which the diazo resin was removed from Comparative Example 5, the stain resistance was very low. It was found for the first time in the present invention that good results were obtained.

(Examples 4 and 5) In Example 1, discarded plates for lithographic printing were prepared by changing the resin layer composition as follows.・ Alkali-soluble urethane binder 5.0 g (weight average molecular weight 85,000, acid content 1.64 meq / g) 4,4-diphenylmethane diisocyanate 37.5 mol% hexamethylene diisocyanate 12.5 mol% 2,2-bis ( (Hydroxymethyl) propionic acid 32.5 mol% Tetraethylene glycol 17.5 mol% ・ Victoria Pure Blue BOH 0.05 g ・ Sulfophthalic acid 0.3 g ・ FC-430 (manufactured by 3M) 0.05 g

The coating amount of the resin layer was 1.0 g / m ² in Example 4,
Example 5 was 0.5 g / m ² . The scratch resistance was better in Example 4 than in Example 1, and equivalent to Example 5. In addition, the resistance to soiling was equal to or higher than that of Example 1 in both Examples 4 and 5, and good results were obtained.

[0040]

As described above, according to the present invention, a lithographic printing plate which does not generate printing stains even when stored for a long period of time, is hardly scratched by handling until gumming is completed, and can be handled with a white lamp. Can be provided.

Claims (4)

[Claims] 1. A lithographic printing plate comprising a metal support having a hydrophilic surface, an undercoat layer made of a water-soluble compound and a water-insoluble non-photosensitive resin layer provided on the metal support. 2. The lithographic printing plate according to claim 1, wherein the undercoat layer is a water-soluble polymer having a sulfonic acid group. 3. The lithographic printing plate according to claim 1, wherein the non-photosensitive resin layer is a resin obtained by solubilizing polyurethane with alkali. 4. A multi-color printing apparatus having two or more plate cylinders is used to attach a plate having an image to some plate cylinders, and to remove a plate for multi-color printing having no image on the remaining plate cylinders. A lithographic printing method for attaching and printing, wherein the discarded plate is the lithographic printing plate according to claim 1.