JP2005274695A - Photosensitive lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photosensitive lithographic printing plate for CTP which is superior in small-dot reproducibility and further has high sensitivity and high printing durability and a photosensitive lithographic printing plate for CTP with high sensitivity and high printing durability which is excellent in small-dot reproducibility and senses a violet laser. <P>SOLUTION: Disclosed is the photosensitive lithographic printing plate having a photopolymerizable photosensitive layer containing a compound which has at least two ethylenenic unsaturated double bonds and is capable of additional polymerization, an alkali-soluble or swelling binder, and a photopolymerization initiation system on a support, the photosensitive lithographic printing plate being characterized in that the photopolymerizable photosensitive layer contains a compound selected from (a) a compound which has three or more ethylenic unsaturated groups in one molecule and a ≤800 molecular weight and is selected from acrylate and methacrylate and (b) a compound selected from an epoxy acrylate compound and a methacrylate compound which have two or three ethylenic unsaturated groups in one molecule as the compound which has at least ethylenenic unsaturated double bonds on a base and is capable of additional polymerization. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photosensitive lithographic printing plate using a photopolymerizable composition. In particular, the present invention relates to a photosensitive lithographic printing plate for direct drawing excellent in reproduction of small dots and fine lines.

Negative photosensitive lithographic printing plates generally apply a photosensitive composition onto a roughened aluminum plate or other support, expose the desired image, and polymerize the image area (light-irradiated area). Alternatively, image formation is performed by a process of crosslinking and insolubilizing with a developer, and eluting non-image areas with the developer. Conventionally, photopolymerizable compositions are well known as photosensitive compositions used for such purposes.
In recent years, digitization technology for electronically processing, storing, and outputting image information by a computer has become widespread. For example, CTP (Computor-To-Plate) technology for scanning a highly directional light such as a laser beam according to digitized image information and directly manufacturing a printing plate without using a lith film is desired. Development of high-sensitivity printing original plates adapted to the above has progressed.

  As this light source, an Ar ion laser (488 nm) or an FD-YAG laser (532 nm) is used, and a photosensitive lithographic printing plate having a photopolymerizable photosensitive layer suitable for these light sources has been developed and put into practical use. . Recently, an InGaN-based semiconductor laser (violet laser, 350 nm to 450 nm) has been developed, and a bright room, lower cost of the exposure machine, and higher productivity are expected. The development of lithographic printing plates having a polymerizable photosensitive layer has been accelerated. As a photopolymerizable composition sensitive to Ar ion laser and FD-YAG laser, a composition containing a combined initiation system of titanocene and coumarin dye described in Patent Documents 1 and 2, etc., and a styryl system described in Patent Document 3 As a composition containing a combination initiation system of a dye and titanocene, and a photopolymerizable composition sensitive to a violet laser, a photopolymerizable composition having a carbazolyl styryl dye described in Patent Document 4 is known. .

When these photopolymerizable compositions are applied as lithographic printing plates, these photopolymerizable photosensitive layers are usually provided on a support, and polyvinyl alcohol or the like for the purpose of preventing oxygen that inhibits polymerization thereon. It is used in a form provided with an oxygen barrier layer. With the photopolymerizable composition, it has become possible to obtain a high-sensitivity and clear relief image, but when a high-definition halftone image of 175 lines or more is created, a small dot of about 1 to 5% It was difficult to reproduce and improvement was desired. Further, the reproduction of small points has been found to have problems that cause variations due to the effects of temperature and humidity during exposure and the time between exposure and development, and improvements have been desired. In addition to the conventional area modulation AM network, the density modulation FM network is also used for the halftone dots used for printing, and the problem of reproducing this small dot becomes large, and an urgent improvement is required. .
JP-A-9-268185 Japanese Patent Laid-Open No. 10-204085 Japanese Patent Laid-Open No. 9-80750 JP 2001-42524 A

  Accordingly, an object of the present invention is to provide a photosensitive lithographic printing plate having excellent small dot reproducibility, and further, a photosensitive lithographic plate having excellent small dot reproducibility and high sensitivity and high printing durability. The present invention is to provide a printing plate and a photosensitive lithographic printing plate for CTP having a high sensitivity and high printing durability that is sensitive to a violet laser having good small dot reproducibility.

The present inventor has found out that the dissolved oxygen in the photopolymerizable photosensitive layer has a great influence on the small-point reproducibility degradation of the lithographic printing plate provided with the photopolymerizable photosensitive layer, and has taken measures to reduce the influence. As a result of intensive studies, the sensitivity and printing durability of the photopolymerizable photosensitive layer are lowered by tackling the photopolymerizable photosensitive layer with a di- or trifunctional epoxy acrylate having a small influence of oxygen in the polymerization reaction of a compound having an ethylenically unsaturated group. However, the present inventors have found that the reproduction of small dots is greatly improved and reached the present invention.
That is, the photosensitive lithographic printing plate according to the present invention is a light containing an addition-polymerizable compound having at least two ethylenically unsaturated double bonds, an alkali-soluble or swellable binder, and a photopolymerization initiation system on a support. A photosensitive lithographic printing plate having a polymerizable photosensitive layer, wherein the photopolymerizable photosensitive layer is selected from acrylates and methacrylates having 3 or more ethylenically unsaturated groups in one molecule and a molecular weight of 800 or less. It contains a compound (a) and a compound (b) selected from an epoxy acrylate compound and an epoxy methacrylate compound having 2 or 3 ethylenically unsaturated groups in one molecule.

The photosensitive lithographic printing plate of the present invention will be described in detail.
The photosensitive lithographic printing plate of the present invention has a photopolymerizable photosensitive layer and a protective layer (oxygen barrier layer) on a support. Moreover, you may provide an undercoat layer between a support body and a photopolymerizable photosensitive layer as needed.

<1. Support>
In order to obtain a lithographic printing plate which is one of the main objects of the present invention, it is desirable to provide the photosensitive layer on a support having a hydrophilic surface. As the hydrophilic support, a conventionally known hydrophilic support used in a lithographic printing plate can be used without limitation. The support used is preferably a dimensionally stable plate, for example, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc). , Copper, etc.), plastic films (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), Paper or plastic film, etc., laminated or vapor-deposited with such metals is included, and appropriate physical and chemical treatments are applied to these surfaces for the purpose of imparting hydrophilicity and improving strength as necessary. You may give it.

  In particular, preferred supports include paper, polyester film or aluminum plate, among which dimensional stability is good, relatively inexpensive, and a surface with excellent hydrophilicity and strength is provided by surface treatment as required. An aluminum plate which can be used is particularly preferred. A composite sheet in which an aluminum sheet is bonded on a polyethylene terephthalate film as described in Japanese Patent Publication No. 48-18327 is also preferable.

  The aluminum substrate is a metal plate mainly composed of dimensionally stable aluminum. In addition to a pure aluminum plate, an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements, or aluminum (alloy) is laminated or Selected from vapor-deposited plastic film or paper.

In the following description, the above-mentioned substrates made of aluminum or an aluminum alloy are generically used as an aluminum substrate. Examples of the foreign element contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of the foreign element in the alloy is 10% by mass or less. In the present invention, a pure aluminum plate is suitable. However, since pure aluminum is difficult to manufacture in terms of refining technology, it may contain slightly different elements.
Thus, the composition of the aluminum plate applied to the present invention is not specified, and conventionally known and used materials such as JIS A 1050, JIS A 1100, JIS A 3103, and JIS A 3005 are appropriately used. It can be used. The thickness of the aluminum substrate used in the present invention is about 0.1 mm to 0.6 mm, preferably 0.15 mm to 0.4 mm, particularly preferably 0.2 mm to 0.3 mm. This thickness can be appropriately changed according to the size of the printing press, the size of the printing plate, and the user's desire. The aluminum substrate may be subjected to a substrate surface treatment described later as necessary. Of course, it may not be applied.

(Roughening treatment)
The aluminum substrate is usually roughened. Examples of the roughening treatment method include mechanical roughening, chemical etching, and electrolytic grain as disclosed in JP-A-56-28893. Electrochemical roughening method that further electrochemically roughens in hydrochloric acid or nitric acid electrolyte solution, and a wire brush grain method in which the aluminum surface is scratched with a metal wire, and a pole in which the aluminum surface is grained with a polishing ball and an abrasive. A mechanical roughening method such as a grain method or a brush grain method in which the surface is roughened with a nylon brush and an abrasive can be used, and the above roughening methods can be used alone or in combination. Among them, a method usefully used for roughening is an electrochemical method in which roughening is chemically roughened in hydrochloric acid or nitric acid electrolyte, and a suitable amount of electricity at the time of anode is 50 C / dm ^{2 to} 400 C / d ² . It is a range. More specifically, in the electrolytic solution containing from 0.1 to 50% hydrochloric acid or nitric acid, the temperature 20 to 80 ° C., for 1 second to 30 minutes, alternating at a current density of 100C / dm ² ~400C / dm ² It is preferable to perform direct current electrolysis.

  The roughened aluminum substrate may be chemically etched with acid or alkali. Etching agents suitably used are caustic soda, sodium carbonate, sodium aluminate, sodium metasilicate, sodium phosphate, potassium hydroxide, lithium hydroxide, and the like. Preferred ranges of concentration and temperature are 1 to 50% and 20%, respectively. ~ 100 ° C. Pickling is performed to remove dirt (smut) remaining on the surface after etching. As the acid used, nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrofluoric acid, borohydrofluoric acid and the like are used. In particular, as a method for removing smut after the electrochemical surface roughening treatment, contact with 15 to 65 mass% sulfuric acid at a temperature of 50 to 90 ° C. as described in JP-A-53-12739 is preferable. And the alkali etching method described in Japanese Patent Publication No. 48-28123. After the processing as described above, the method condition is not particularly limited as long as the center line average group Ra Ra of the processing surface is 0.2 to 0.5 μm.

[Anodizing treatment]
The aluminum substrate that has been roughened as described above is then anodized to form an oxide film. In the anodizing treatment, sulfuric acid, phosphoric acid, oxalic acid, or an aqueous solution of boric acid / sodium borate is used alone or in combination as a main component of an electrolytic bath. In this case, the electrolyte solution may of course contain at least components normally contained in at least an Al alloy plate, an electrode, tap water, groundwater and the like. Further, the second and third components may be added. Here, the second and third components are, for example, metal ions such as Na, K, Mg, Li, Ca, Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, and ammonium ions. Examples include cations, nitrate ions, carbonate ions, chloride ions, phosphate ions, fluorine ions, sulfite ions, titanate ions, silicate ions, borate ions and the like, and the concentration is 0 to 10,000 ppm. May be included. There are no particular limitations on the conditions for the anodizing treatment, but the treatment is preferably performed by direct current or alternating current electrolysis at a treatment liquid temperature of 10 to 70 ° C. and a current density of 0.1 to 40 A / m ² at 30 to 500 g / liter. . The thickness of the formed anodic oxide film is in the range of 0.5 to 1.5 μm. Preferably it is the range of 0.5-1.0 micrometer.

  Furthermore, after performing these treatments, water-soluble resins such as polyvinylphosphonic acid, polymers and copolymers having sulfonic acid groups in the side chain, polyacrylic acid, water-soluble metal salts (for example, zinc borate) or Those having a primer such as a yellow dye or an amine salt are also suitable. Further, a sol-gel treated substrate in which a functional group capable of causing an addition reaction by a radical as disclosed in JP-A-7-159983 is covalently used.

  As another preferred example, a substrate provided with a water-resistant hydrophilic layer as a surface layer on an arbitrary support can be raised. Examples of such a surface layer include a layer composed of an inorganic pigment and a binder described in US Pat. No. 3,055,295 and JP-A-56-13168, and a hydrophilic swelling described in JP-A-9-80744. A layer, a sol-gel film made of titanium oxide, polyvinyl alcohol, silicic acid or the like described in JP-A-8-507727 can be raised. These hydrophilic treatments are performed to make the surface of the support hydrophilic, in order to prevent harmful reaction of the photopolymerizable composition provided thereon, and to improve the adhesion of the photosensitive layer. It is given for the purpose.

<2. Undercoat layer>
A water-soluble resin such as polyvinylphosphonic acid, a polymer or copolymer having a sulfonic acid group in the side chain (JP-A-59-101651), polyacrylic acid, water-soluble as an undercoat layer on the support. A metal salt (for example, zinc borate), a yellow dye, an amine salt, or the like can be provided. Further, a sol-gel treated substrate in which a functional group capable of causing an addition reaction by a radical as disclosed in JP-A-7-159983 is covalently used.

Other preferred examples include an undercoat layer having an onium group described in JP-A No. 2003-021908, and a substrate provided with a water-resistant hydrophilic layer as a surface layer on an arbitrary support. Examples of such a surface layer include a layer comprising an inorganic pigment and a binder described in US3055295 and JP-A-56-13168, a hydrophilic swelling layer described in JP-A-9-80744, and JP-A-8-507727. The sol-gel film made of titanium oxide, polyvinyl alcohol, silicic acid or the like described in the above can be raised. These hydrophilic treatments are performed to make the surface of the support hydrophilic, in order to prevent harmful reactions of the photosensitive composition provided thereon, and to improve the adhesion of the photosensitive layer, etc. It is given for.
The coating amount of the undercoat layer is a dry weight, generally 0.5 to 500 mg / m ^2, preferably from 1 to 100 mg / m ^2.

<3. Photopolymerizable photosensitive layer>
The photopolymerizable composition for coating the photopolymerizable photosensitive layer of the photosensitive lithographic printing plate of the present invention comprises an addition-polymerizable compound having at least one ethylenically unsaturated double bond (hereinafter referred to as “ethylenic”). In some cases, it is abbreviated as “unsaturated bond-containing compound”), an alkaline water-soluble or swellable binder, and a photopolymerization initiator as essential components, and if necessary, a colorant, a plasticizer, a thermal polymerization inhibitor, etc. Various compounds can be used in combination.

(A. Ethylenically unsaturated bond-containing compound)
In the present invention, as the ethylenically unsaturated bond-containing compound, a compound selected from acrylates and methacrylates having 3 or more ethylenically unsaturated groups in one molecule and having a molecular weight of 800 or less (an ethylenically unsaturated bond-containing compound ( a)) and a compound selected from an epoxy acrylate compound and an epoxy methacrylate compound having two or three ethylenically unsaturated groups in one molecule (an ethylenically unsaturated bond-containing compound (b)) are used in combination.
In order to produce a cured film having high sensitivity and high printing durability, a compound in which an ethylenically unsaturated group is clogged with nectar, for example, compound (a) is considered advantageous. When these compounds are used alone, characters with little influence of oxygen and large halftone dots can provide sufficient image formation and sufficient printing durability, but small dot image formation with great influence of oxygen is not possible. The dot reproducibility was insufficient. There is also a problem that it is easily affected by the environment (temperature, humidity) during exposure.

On the other hand, as an ethylenically unsaturated compound that is relatively less susceptible to oxygen, epoxy acrylates such as the compound (b) having a high polymerization rate and a hydroxyl group in the molecule are known. The exposure dose (30 to 200 μJ / cm ² ) used in CTP and the like has problems such as reproducibility of small dots and low printing durability, and is difficult to put to practical use.
Therefore, in order to improve the reproducibility of small spots, we searched for various ethylenically unsaturated compounds. However, by mixing both of the above ethylenic compounds, photopolymerization can be achieved even in small spots where oxygen is greatly affected. It has been found that sufficient sensitivity and printing durability can be obtained at the same time as showing good reproducibility. The reason is not clear, but it is presumed that it is induced by the polymerization of epoxy acrylates with little influence of oxygen, and the polymerization of ethylenically unsaturated compounds with a high density of unsaturated groups is promoted to form a tough polymer film. The

(Ethylene unsaturated bond-containing compound (a))
As the compound (a) which is an acrylate or methacrylate having 3 or more ethylenically unsaturated groups in one molecule and a molecular weight of 800 or less, unsaturated carboxylic acid (for example, acrylic acid, methacrylic acid, itaconic acid, croton) Acid, isocrotonic acid, maleic acid, etc.) with aliphatic polyhydric alcohol compounds, amides of unsaturated carboxylic acids with aliphatic polyvalent amine compounds, and the like.
The molecular weight of the ethylenically unsaturated bond-containing compound (a) is preferably 267 to 800, and the number of ethylenically unsaturated groups is preferably 3 to 8.

Specific examples of the monomer of an ester of an aliphatic polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as trimethylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, Pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligomer Etc.
Methacrylic acid esters include trimethylolpropane trimethacrylate, trimethylolpropane tri (methacryloyloxypropyl) ether, trimethylolethane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexa Examples include methacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, sorbitol pentamethacrylate, sorbitol hexamethacrylate, tri (methacryloyloxyethyl) isocyanurate, and polyester methacrylate oligomers.

Examples of the itaconic acid ester include trimethylolpropane triitaconate, pentaerythritol triitaconate, pentaerythritol tetritaconate, dipentaerythritol hexaitaconate, sorbitol triitaconate, tri (itaconeyloxyethyl) isocyanurate, and the like.
Examples of crotonic acid esters include trimethylolpropane tricrotonate, pentaerythritol tricrotonate, pentaerythritol tetracrotonate, dipentaerythritol hexacrotonate, sorbitol tricrotonate, and tri (crotonyloxyethyl) isocyanurate.
As isocrotonic acid ester, trimethylolpropane triisocrotonate, pentaerythritol triisocrotonate, pentaerythritol tetraisocrotonate, dipentaerythritol hexaisocrotonate, sorbitol triisocrotonate, tri (isocrotonyloxyethyl) Isocyanurate and the like.

The maleic acid esters, trimethylolpropane trimmer rates, pentaerythritol trimmer rates, pentaerythritol tetra iso malate, dipentaerythritol hexa maleate, sorbitol bets malate, tri (Murray oxy ethyl) isocyanurate.
Specific examples of amide monomers of aliphatic polyvalent amine compounds and unsaturated carboxylic acids include diethylenetriamine trisacrylamide, diethylenetriamine trismethacrylamide, triethylenetetramine trisacrylamide, triethylenetetramine trismethacrylamide, triethylenetetramine tetraacrylamide. And triethylenetetramine tetramethacrylamide.
Other examples include polyisocyanate compounds having 3 or more isocyanate groups in one molecule described in Japanese Patent Publication No. 48-41708, such as ethyloxyacrylic acid and ethyloxymethacrylic acid. Examples thereof include vinylurethane compounds having 3 or more polymerizable vinyl groups in one molecule, to which a vinyl monomer having a hydroxyl group is added.

  Also, urethane acrylates described in JP-A-51-37193 and JP-B-2-32293, JP-A-48-64183, JP-B-49-43191, JP-B-52-30490 Among the polyester acrylates described in 1), those having a trifunctional or higher functionality and a molecular weight of 800 or lower can be selected and used.

(Ethylene unsaturated bond-containing compound (b))
The ethylenically unsaturated bond-containing compound (b) is a compound selected from an epoxy acrylate compound and an epoxy methacrylate compound having two or three ethylenically unsaturated groups in one molecule. For example, an epoxy compound and (meth) Mention may be made of polyfunctional acrylates and methacrylates such as epoxy acrylates reacted with acrylic acid.
The molecular weight of the ethylenically unsaturated bond-containing compound (b) is preferably 304 to 2000, more preferably 350 to 1000.
Examples of specific compounds are not limited to the following compounds.

The total amount of the ethylenically unsaturated bond-containing compounds (a) and (b) is preferably in the range of 10 to 80% by mass, more preferably 30 to 70% by mass, based on the total solid content constituting the photopolymerizable photosensitive layer. used.
The mixing ratio (a: b) of the ethylenically unsaturated bond-containing compounds (a) and (b) is preferably in the range of 9: 1 to 2: 8, and in the range of 8: 2 to 3: 7. Is more preferable.

(B. Binder)
The binder used in the photopolymerizable composition of the present invention is an alkaline water-soluble or swellable binder that not only functions as a film-forming agent but also needs to be dissolved in an alkaline developer, so that it is soluble in alkaline water. Alternatively, an organic polymer that is swellable is used. For example, when the water-soluble organic polymer is used as the organic polymer, water development is possible. Examples of such an organic polymer include addition polymers having a carboxylic acid group in the side chain, such as JP-A-59-44615, JP-B-54-34327, JP-B-58-12577, JP-B-54- No. 25957, JP-A-54-92723, JP-A-59-53836, JP-A-59-71048, that is, methacrylic acid copolymer, acrylic acid copolymer, Examples thereof include an itaconic acid copolymer, a crotonic acid copolymer, a maleic acid copolymer, and a partially esterified maleic acid copolymer.

  Similarly, there is an acidic cellulose derivative having a carboxylic acid group in the side chain. In addition, those obtained by adding a cyclic acid anhydride to an addition polymer having a hydroxyl group are useful. Among these, [benzyl (meth) acrylate / (meth) acrylic acid / other addition-polymerizable vinyl monomers as required] copolymers and [allyl (meth) acrylate (meth) acrylic acid / as required Other addition polymerizable vinyl monomers] copolymers are preferred. In addition, polyvinyl pyrrolidone, polyethylene oxide, and the like are useful as the water-soluble organic polymer. In order to increase the strength of the cured film, alcohol-soluble polyamide, polyether of 2,2-bis- (4-hydroxyphenyl) -propane and epichlorohydrin, etc. are also useful. JP-B-7-120040, JP-B7-120041, JP-B7-120042, JP-B-8-12424, JP-A-63-287944, JP-A-63-287947, JP-A1-271741 And polyurethane resins described in JP-A-11-352691 are also useful for the use of the present invention.

  These organic polymer polymers can improve the strength of the cured film by introducing a radical reactive group into the side chain. Functional groups that can undergo an addition polymerization reaction include ethylenically unsaturated bond groups, amino groups, and epoxy groups, and functional groups that can become radicals upon light irradiation include mercapto groups, thiol groups, halogen atoms, triazine structures, and onium salt structures. In addition, examples of the polar group include a carboxyl group and an imide group. The functional group capable of undergoing addition polymerization reaction is particularly preferably an ethylenically unsaturated bond group such as an acryl group, a methacryl group, an allyl group, or a styryl group, but also an amino group, a hydroxy group, a phosphonic acid group, a phosphoric acid group, or a carbamoyl group. A functional group selected from an isocyanate group, a ureido group, a ureylene group, a sulfonic acid group, and an ammonio group is also useful.

  In order to maintain the developability of the photosensitive layer, the binder preferably has an appropriate molecular weight and acid value, and a high molecular weight polymer having a mass average molecular weight of 5000 to 300,000 and an acid value of 20 to 200 is effectively used. The These polymer binders can be mixed in an arbitrary amount in the composition of the present invention. In particular, if it is 90% by mass or less, a preferable result is given in terms of the strength of the formed image. Preferably it is 10-90 mass%, More preferably, it is 30-80 mass%. The photopolymerizable ethylenically unsaturated bond-containing compound and the polymer binder are preferably in the range of 1/9 to 9/1 by mass ratio. A more preferred range is 2/8 to 8/2, and even more preferred is 3/7 to 7/3.

(C. Photopolymerization initiator)
Depending on the wavelength of the light source used, the photopolymerization initiator contained in the photopolymerizable photosensitive layer may be various photoinitiators known in patents, literature, etc., or a combined system of two or more photoinitiators (photoinitiation System) can be appropriately selected and used. Specific examples are listed below, but are not limited thereto.
Various photoinitiating systems have been proposed in the case of using visible light of 400 nm or more, Ar laser, second harmonic of a semiconductor laser, and SHG-YAG laser as a light source, for example, US Pat. No. 2,850,445. Certain photoreductive dyes described in No. 1, for example, rose bengal, eosin, erythrosine, etc., or a combination of a dye and an initiator, for example, a combined initiator system of a dye and an amine (Japanese Patent Publication No. 44-20189) , Hexaarylbiimidazole, radical generator and dye combination system (Japanese Examined Patent Publication No. 45-37377), hexaarylbiimidazole and p-dialkylaminobenzylidene ketone (Japanese Examined Patent Publication No. 47-2528, Japanese Patent Laid-Open Publication No. 54- 155292), a system of a cyclic cis-α-dicarbonyl compound and a dye (Japanese Patent Laid-Open No. 48-84183), Azine and merocyanine dye systems (Japanese Patent Laid-Open No. 54-151024), 3-ketocoumarin and activator systems (Japanese Patent Laid-Open Nos. 52-111261, 58-15503), biimidazole, styrene derivatives, and thiols System (Japanese Patent Laid-Open No. 59-140203), organic peroxide and dye system (Japanese Patent Laid-Open No. 59-1504, Japanese Patent Laid-Open No. 59-140203, Japanese Patent Laid-Open No. 59-189340, Japanese Patent Laid-Open No. 62-174203) No. 6, JP-B 62-1641, US Pat. No. 4,766,055), dyes and active halogen compounds (JP-A 63-258903, JP-A 2-63054, etc.), dyes and borate compounds (JP, A, etc.) JP-A-62-143044, JP-A-62-1050242, JP-A-64-13140, JP-A-64-13141, JP-A-64-13142, JP-A-64- 13143, JP-A-64-13144, JP-A-64-17048, JP-A-1-229003, JP-A-1-298348, JP-A-1-138204, etc.) Dye having a rhodanine ring and radical generator Systems (JP-A-2-17943, JP-A-2-244050), titanocene and 3-ketocoumarin dye systems (JP-A 63-221110), titanocene and xanthene dyes, addition polymerization containing amino groups or urethane groups A combination of possible ethylenically unsaturated compounds (JP-A-4-221958, JP-A-4-219756), titanocene and a specific merocyanine dye system (JP-A-6-295061), having a titanocene and a benzopyran ring Examples thereof include dye systems (JP-A-8-334897).

Recently, a laser having a wavelength of 400 to 410 nm (violet laser) has been developed, and a photoinitiating system exhibiting high sensitivity at a wavelength of 450 nm or less that responds to it has been developed, and these photoinitiating systems are also used.
For example, a cationic dye / borate system (JP-A-11-84647), a merocyanine dye / titanocene system (JP-A 2000-147663), a carbazole type dye / titanocene system (Japanese Patent Application No. 11-212480) and the like can be mentioned. .
In the present invention, a system using a titanocene compound is particularly preferable in view of sensitivity.

Various titanocene compounds can be used. For example, various titanocene compounds described in JP-A-59-152396 and JP-A-61-151197 can be appropriately selected and used. . More specifically, di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, di-cyclopentadienyl-Ti-bis-2,3,4,5 , 6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2 , 4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,6-di-fluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2, 4-di-fluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti -Bis-2, - difluoro-1-yl, di - cyclopentadienyl -Ti- bis-2,6-difluoro-3- (pyrr-1-yl) - can be exemplified 1-yl and the like.
Further, if necessary for the above photoinitiator, thiol compounds such as 2-mercaptobenzthiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, amines such as N-phenylglycine, N, N-dialkylamino aromatic alkyl ester, etc. It is known that the photoinitiating ability can be further enhanced by adding a hydrogen-donating compound such as a compound.
The amount of the photopolymerization initiator (system) used is generally 0.05 to 100 parts by weight, preferably 0.1 to 70 parts by weight, more preferably 100 parts by weight of the ethylenically unsaturated bond-containing compound. It is used in the range of 0.2 to 50 parts by mass.

  The photosensitive lithographic printing plate of the present invention is particularly effective in a photopolymerization initiation system having a photosensitive wavelength in the range of 350 to 450 nm. Examples of the photopolymerization initiation system having a photosensitive wavelength in the range of 350 nm to 450 nm include a complex initiation system of a sensitizing dye having a maximum absorption at 350 to 400 nm and an active initiator as described above.

  In addition to the above-mentioned ethylenically unsaturated group-containing compound, a binder that can be dissolved or swelled in an alkali developer, and a photopolymerization initiator, a photopolymerizable composition for forming a photopolymerizable photosensitive layer of the present invention, Various compounds such as a thermal polymerization inhibitor, a colorant, and a plasticizer can be used in combination.

In the present invention, in addition to the above basic components, in order to prevent unnecessary thermal polymerization of the ethylenically unsaturated bond-containing compound that can be polymerized during the production or storage of the photopolymerizable composition used in the photopolymerization layer. It is desirable to add a small amount of a thermal polymerization inhibitor. Suitable thermal polymerization inhibitors include haloid quinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,4-thiobis (3-methyl-6-t-butylphenol) 2,2′-methylenebis (4-methyl-6-t-butylphenol), N-nitrosophenylhydroxylamine cerium salt, N-nitrosophenylhydroxylamine aluminum salt, and the like. The addition amount of the thermal polymerization inhibitor is preferably about 0.01% by mass to about 5% by mass with respect to the total solid content of the composition. If necessary, a higher fatty acid derivative such as behenic acid or behenamide is added to prevent polymerization inhibition by oxygen, and it is unevenly distributed on the surface of the photopolymerizable photosensitive layer in the process of drying after coating. May be. The addition amount of the higher fatty acid derivative or the like is preferably about 0.5 mass% to about 10 mass% of the total solid content of the composition.

  Further, a coloring agent may be added for the purpose of coloring the photopolymerizable photosensitive layer. Examples of the colorant include phthalocyanine pigments (CIPigment Blue 15: 3, 15: 4, 15: 6, etc.), azo pigments, pigments such as carbon black and titanium oxide, ethyl violet, crystal violet, azo dyes, There are anthraquinone dyes and cyanine dyes. The addition amount of the dye and the pigment is preferably about 0.5% by mass to about 20% by mass of the total composition. In addition, in order to improve the physical properties of the cured film, an additive such as an inorganic filler or a plasticizer such as dioctyl phthalate, dimethyl phthalate, or tricresyl phosphate may be added. These addition amounts are preferably 10% by mass or less based on the total solid content (total composition) of the composition.

  When applying the photopolymerizable composition, it is dissolved in various organic solvents and used. Solvents used here include acetone, methyl ethyl ketone, cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 3-methoxypropanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, di Ethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate-3-methoxypropyl acetate, N, N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, methyl lactate, lactic acid There are ethyl and the like. These solvents can be used alone or in combination. And the density | concentration of the solid content in a coating solution is 1-50 mass% generally.

A surfactant can be added to the photopolymerizable composition in order to improve the coating surface quality. The coating amount of the mass after drying, preferably about 0.1 g / m ² ~ about 10 g / m ^2, more preferably 0.3 to 5 g / m ^2, more preferably 0.5 to 3 g / m ² .

<4. Protective layer>
In the photosensitive lithographic printing plate of the present invention, since exposure is usually performed in the air, it is preferable to further provide a protective layer on the layer of the photopolymerizable composition. The protective layer prevents exposure of low molecular weight compounds such as oxygen and basic substances present in the atmosphere that hinder the image formation reaction caused by exposure in the photosensitive layer, and enables exposure in the atmosphere. To do. Therefore, the properties desired for such a protective layer are low permeability of low-molecular compounds such as oxygen, and further, transmission of light used for exposure is not substantially inhibited, and adhesion to the photosensitive layer is excellent. And it is desirable that it can be easily removed in the development process after exposure. Such a device for the protective layer has been conventionally devised, which is described in detail in US Pat. No. 3,458,311 and JP-A-55-49729.

  As a material that can be used for the protective layer, for example, a water-soluble polymer compound having relatively excellent crystallinity is preferably used. Specifically, polyvinyl alcohol, polyvinyl pyrrolidone, acidic celluloses, gelatin, gum arabic, Water-soluble polymers such as acrylic acid are known, but among these, the use of polyvinyl alcohol as a main component gives the best results in terms of basic properties such as oxygen barrier properties and development removability. The polyvinyl alcohol used for the protective layer may be partially substituted with an ester, an ether, and an acetal as long as it contains an unsubstituted vinyl alcohol unit for having necessary oxygen barrier properties and water solubility. Similarly, some of them may have other copolymer components. Specific examples of polyvinyl alcohol include those having a hydrolysis rate of 71 to 100% and a molecular weight in the range of 300 to 2400.

  Specifically, Kuraray Co., Ltd. PVA-105, PVA-110, PVA-11 17, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST, PVA-HC , PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220, PVA-224, PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-405, PVA -420, PVA-613, L-8 and the like.

  Components of the protective layer (selection of PVA, use of additives), coating amount, and the like are selected in consideration of fogging, adhesion, and scratch resistance in addition to oxygen barrier properties and development removability. In general, the higher the hydrolysis rate of the PVA used (the higher the content of the unsubstituted vinyl alcohol unit in the protective layer), the thicker the film thickness, the higher the oxygen barrier property, which is advantageous in terms of sensitivity. However, when the oxygen barrier property is extremely increased, there arises a problem that unnecessary polymerization reaction occurs during production and raw storage, and unnecessary fogging and image line thickening occur during image exposure. In addition, adhesion to the image area and scratch resistance are extremely important in handling the plate. That is, when a hydrophilic layer made of a water-soluble polymer is laminated on an oleophilic polymer layer, film peeling due to insufficient adhesion tends to occur, and the peeled part causes defects such as poor film hardening due to inhibition of oxygen polymerization.

  On the other hand, various proposals have been made to improve the adhesion between these two layers. For example, in US Pat. No. 292,501 and US Pat. No. 44,563, an acrylic emulsion or a water-insoluble vinyl pyrrolidone-vinyl acetate copolymer is added to a hydrophilic polymer mainly composed of polyvinyl alcohol in an amount of 5 to 80. It is described that sufficient adhesion can be obtained by mixing by mass% and laminating on a polymerized layer. Any of these known techniques can be applied to the protective layer in the present invention. Such a coating method of the protective layer is described in detail in, for example, US Pat. No. 3,458,311 and JP-A-55-49729.

  Furthermore, other functions can be imparted to the protective layer. For example, by adding a colorant (such as a water-soluble dye) that is excellent in the transmission of light from 350 nm to 450 nm and that can absorb light of 500 nm or more, which is used for exposure, it is safe light without causing a decrease in sensitivity. The aptitude can be further enhanced.

The coating amount of the protective layer is generally about 0.1 g / m ² to about 15 g / m ² , preferably 1.0 g / m ² to about 5.0 g / m ² in terms of the mass after drying.

<5. Plate making method>
The photosensitive lithographic printing plate of the present invention is usually subjected to image exposure, and then an unexposed portion of the photosensitive layer is removed with a developer to obtain an image.

  In addition, as the plate making process of the photosensitive lithographic printing plate of the present invention, the entire surface may be heated before exposure, during exposure, and between exposure and development, if necessary. By such heating, the image forming reaction in the photosensitive layer is promoted, and advantages such as improvement in sensitivity and printing durability and stabilization of sensitivity may occur. Further, for the purpose of improving the image strength and printing durability, it is also effective to perform the entire post-heating or the entire exposure on the developed image. Usually, the heating before development is preferably performed under a mild condition of 150 ° C. or less. If the temperature is too high, problems such as covering up to the non-image area occur. Very strong conditions are used for heating after development. Usually, it is the range of 200-500 degreeC. If the temperature is low, sufficient image strengthening action cannot be obtained. If the temperature is too high, problems such as deterioration of the support and thermal decomposition of the image area occur.

  As a method for exposing a scanning exposure lithographic printing plate according to the present invention, a known method can be used without limitation. Desirably, the wavelength of the light source is 350 nm to 450 nm, and specifically, an InGaN-based semiconductor laser is suitable. The exposure mechanism may be any of an internal drum system, an external drum system, a flat bed system, and the like. The photosensitive layer component of the present invention can be made soluble in neutral water or weak alkaline water by using a highly water-soluble component. A lithographic printing plate having such a structure is used in a printing machine. After loading on top, exposure-development can be performed on the machine.

Further, as other exposure light rays for the photopolymerizable composition according to the present invention, ultrahigh pressure, high pressure, medium pressure, and low pressure mercury lamps, chemical lamps, carbon arc lamps, xenon lamps, metal halide lamps, various visible and ultraviolet lasers. A lamp, a fluorescent lamp, a tungsten lamp, sunlight, etc. can also be used. As available laser light sources of 350 nm to 450 nm, the following can be used.
As a gas laser, Ar ion laser (364 nm, 351 nm, 10 mW to 1 W), Kr ion laser (356 nm, 351 nm, 10 mW to 1 W), He—Cd laser (441 nm, 325 nm, 1 mW to 100 mW), and solid laser as Nd: YAG (YVO ₄ ) and SHG crystal × 2 combinations (355 nm, 5 mW to 1 W), Cr: LiSAF and SHG crystal combination (430 nm, 10 mW), KNbO ₃ ring resonator (430 nm, 30 mW) as a semiconductor laser system A combination of a waveguide type wavelength conversion element and AlGaAs, InGaAs semiconductor (380 nm to 450 nm, 5 mW to 100 mW), a combination of a waveguide type wavelength conversion element, AlGaInP and AlGaAs semiconductor (300 nm to 350 nm, 5 mW to 10 mW) 0 mW), AlGaInN (350 nm to 450 nm, 5 mW to 30 mW), and other pulse lasers include N ₂ laser (337 nm, pulse 0.1 to 10 mJ) and XeF (351 nm, pulse 10 to 250 mJ). In particular, an AlGaInN semiconductor laser (commercially available InGaN-based semiconductor laser 400 to 410 nm, 5 to 30 mW) is preferable in terms of wavelength characteristics and cost.

Further, as the lithographic printing plate exposure apparatus of the scanning exposure method, there are an inner drum method, an outer drum method, and a flat bed method as an exposure mechanism, and a light source that can continuously oscillate among the light sources can be preferably used. . Practically, the following exposure apparatus is particularly preferable in terms of the relationship between the photosensitive material sensitivity and the plate making time.

To achieve a semiconductor laser with a total output of 20 mW or more with the internal drum method, a total output of 20 mW or more with a single beam to triple beam exposure apparatus / flatbed method using one or more gas lasers or solid laser light sources, One semiconductor laser, gas laser, or solid-state laser so that the total output is 20 mW or more with a multi-beam (1-10) exposure device and external drum system that uses one or more semiconductor lasers, gas lasers, or solid-state lasers. Multi-beam (1 to 9) exposure apparatus used above ・ Multi-beam (10 or more) exposure apparatus using one or more semiconductor lasers or solid-state lasers so that the total output is 20 mW or more with the external drum system. In the case of laser direct-drawing lithographic printing plates such as m ^2), the exposure area S (cm ² of photosensitive material), the laser light source 1 power q (W), the laser number n, the formula (eq 1) is established between the total exposure time t (s).
X · S = n · q · t-(eq 1)
i) In the case of the internal drum (single beam) system, the laser rotation speed f (radians / s), the sub-scanning length Lx (cm) of the photosensitive material, the resolution Z (dots / cm), and the total exposure time t (s) In general, equation (eq 2) holds.
f.Z.t = Lx-(eq 2)

ii) In the case of the external drum (multi-beam) system, the drum rotation speed F (radians / s), the photosensitive material sub-scanning length Lx (cm), the resolution Z (dots / cm), the total exposure time t (s), the number of beams In general, the equation (eq 3) is established during (n).
F.Z.n.t = Lx-(eq 3)

iii) In the case of the flat head (multi-beam) method, the rotational speed H (radians / s) of the polygon mirror, the sub-scanning length Lx (cm) of the photosensitive material, the resolution Z (dots / cm), the total exposure time t (s), Equation (eq 4) is generally established between the number of beams (n).
F.Z.n.t = Lx-(eq 4)

Resolution (2560 dpi) required for an actual printing plate, plate size (A1 / B1, sub-scanning length 42 inch), exposure conditions of about 20 sheets / hour and photosensitive characteristics of the photosensitive composition of the present invention (photosensitive wavelength, By substituting (sensitivity: about 0.1 mJ / cm ² ) into the above equation, it can be understood that a combination with a multi-beam exposure method using a laser having a total output of 20 mW or more is preferable in the photosensitive material of the present invention. However, when a laser having a necessary and sufficient output (30 mW or more) is used, a combination with an internal drum type semiconductor laser single beam exposure apparatus is most preferable in terms of operability and cost.

  In addition, a heating process is performed at a temperature of 50 ° C. to 150 ° C. for a period of 1 second to 5 minutes in order to increase the curing rate of the photopolymerization type photosensitive layer after image exposure with conventionally known actinic light and development. Thus, the curability of the non-image area can be improved and the printing durability can be further improved, which is more preferable.

Further, the developed photosensitive lithographic printing plate is washed with water, a surfactant and the like as described in JP-A Nos. 54-8002, 55-1115045 and 59-58431. And a desensitizing solution containing gum arabic, starch derivatives and the like. These treatments can be used in various combinations for the post-treatment of the photosensitive lithographic printing plate of the present invention.
The lithographic printing plate obtained by such treatment is applied to an offset printing machine and used for printing a large number of sheets.

  The above-mentioned photosensitive lithographic printing plate can be developed using a conventionally known developer to form an image. These conventionally known developers are described in JP-B-57-7427. Developers such as sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, tribasic sodium phosphate, dibasic sodium phosphate, tribasic ammonium phosphate, dibasic phosphate Aqueous solutions of inorganic alkali agents such as ammonium, sodium metasilicate, sodium bicarbonate, aqueous ammonia, and organic alkali agents such as monoethanolamine or diethanolamine are suitable. The alkali solute concentration of the developer is generally 0.1 to 10% by mass, preferably 0.5 to 5% by mass.

  Such an alkali developer may contain a small amount of an organic solvent such as a surfactant, benzyl alcohol, 2-phenoxyethanol, and 2-butoxyethanol as necessary. Examples thereof include those described in US Pat. Nos. 3,375,171 and 3,615,480. Furthermore, the developing solution described in each gazette of Unexamined-Japanese-Patent No. 50-26601, 58-54341, Japanese Patent Publication No. 56-39464, and 56-42860 can also be mentioned.

  The developer used for the plate making of the photosensitive lithographic printing plate of the present invention is a nonionic interface having a polyoxyalkylene ether group from the point of deterioration of dots such as halftone dots and solid fine lines as described above. An alkaline developer containing an activator and having a pH of 10.5 to 13.5 (more preferably pH 1.0 to 12.5) is preferred.

  By containing a nonionic surfactant having a polyoxyalkylene ether group, dissolution of the photosensitive layer in the unexposed area can be promoted, and the permeability of the developer into the exposed area can be reduced. As the surfactant containing a polyoxyalkylene ether group, one having a structure of the following general formula (B) is preferably used.

R ³ —O— (R ⁴ —O) qH (B)
Wherein, R ³ has an alkyl group which may having 3 to 15 carbon atoms which may have a substituent, an aromatic hydrocarbon group which may having from 6 to 15 carbon atoms which may have a substituent, or a substituent A heteroaromatic cyclic group having 4 to 15 carbon atoms (wherein the substituent is an alkyl group having 1 to 20 carbon atoms, a halogen atom such as Br, Cl, or I, or an aromatic hydrocarbon having 6 to 15 carbon atoms) Group, an aralkyl group having 7 to 17 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, and an acyl group having 2 to 15 carbon atoms), and R ⁴ is C1-C100 alkylene group which may have a substituent (In addition, as a substituent, a C1-C20 alkyl group and a C6-C15 aromatic hydrocarbon group are mentioned.). Q represents an integer of 1 to 100.

  In the definition of the above formula (B), specific examples of the “aromatic hydrocarbon group” include phenyl group, tolyl group, naphthyl group, anthryl group, biphenyl group, phenanthryl group and the like, and “heteroaromatic ring” Specific examples of the “group” include furyl group, thionyl group, oxazolyl group, imidazolyl group, pyranyl group, pyridinyl group, acridinyl group, benzofuranyl group, benzothionyl group, benzopyranyl group, benzooxazolyl group, benzoimidazolyl group, and the like. It is done.

In addition, the (R ⁴ —O) q moiety of the formula (I) may be two or three groups as long as it is in the above range. Specific examples include a combination of random or block combinations of ethyleneoxy and propyleneoxy, ethyleneoxy and isopropyloxy, ethyleneoxy and butyleneoxy, ethyleneoxy and isobutylene, and the like. . In the present invention, the surfactant having a polyoxyalkylene ether group is used alone or in a composite system, and it is effective to add 1 to 30% by mass, preferably 2 to 20% by mass in the developer. If the addition amount is small, the developability is deteriorated. On the other hand, if the amount is too large, the development damage becomes strong and the printing durability of the printing plate is lowered.

  Examples of the nonionic surfactant having a polyoxyalkylene ether group represented by the above formula (B) include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, and polyoxyethylene stearyl ether. Polyoxyethylene aryl ethers such as polyoxyethylene phenyl ether and polyoxyethylene naphthyl ether, polyoxyethylene alkyl aryl ethers such as polyoxyethylene methyl phenyl ether, polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether Kind.

  Further, other surfactants described below may be added. Other surfactants include polyoxyethylene alkyl esters such as polyoxyethylene stearate, sorbitan monolaurate, sorbitan monostearate, sorbitan distearate, sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate Nonionic surfactants such as sorbitan alkyl esters such as glycerol monostearate and monoglyceride alkyl esters such as glycerol monooleate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; sodium butylnaphthalenesulfonate; pentylnaphthalenesulfonic acid Alkylnaphthalenesulfonic acid such as sodium, sodium hexylnaphthalenesulfonate, sodium octylnaphthalenesulfonate , Alkyl sulfates such as sodium lauryl sulfate, alkyl sulfonates such as sodium dodecyl sulfonate, sulfosuccinic acid ester salts such as sodium dilauryl sulfosuccinate; alkyl betaines such as lauryl betaine and stearyl betaine Amphoteric surfactants such as amino acids can be used, and anionic surfactants such as alkylnaphthalene sulfonates are particularly preferred.

  Surfactants can be used alone or in combination. Further, the content of the surfactant in the developer is preferably in the range of 0.1 to 20% by mass in terms of active ingredient.

  This alkaline developer usually contains an inorganic alkali salt. The inorganic alkali salt can be appropriately selected. For example, sodium hydroxide, potassium, ammonium, lithium, sodium silicate, potassium, ammonium, lithium, tribasic sodium phosphate, potassium, ammonium Inorganic alkaline agents such as sodium carbonate, potassium, ammonium, sodium hydrogencarbonate, potassium, ammonium, sodium borate, potassium, and ammonium. These may be used alone or in combination of two or more.

In the case of using silicate, developability is achieved by adjusting the mixing ratio and concentration of silicon oxide SiO ₂ which is a component of silicate and alkali oxide M ₂ O (M represents an alkali metal or ammonium group). Can be easily adjusted. Among the alkaline aqueous solutions, those having a mixing ratio (SiO ₂ / M ₂ O: molar ratio) of the silicon oxide SiO ₂ and the oxide M ₂ O of 0.5 to 3.0 are preferable and 1.0 to 1.0. Those of 2.0 are preferred. When the SiO ₂ / M ₂ O is less than 0.5, it is preferably 1 to 10% by mass, more preferably 3 to 8% by mass, and most preferably 4 to 7% by mass with respect to the mass of the alkaline aqueous solution. If this concentration is less than 1% by mass, developability and processing ability may be lowered. If it exceeds 10% by mass, precipitation and crystals are likely to be generated, and further gelation tends to occur during neutralization in the waste liquid. Therefore, the waste liquid treatment may be hindered.

In addition, an organic alkali agent may be supplementarily used for the purpose of finely adjusting the alkali concentration and assisting the solubility of the photosensitive layer. Examples of the organic alkali agent include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, Examples thereof include diisopropanolamine, ethyleneimine, ethylenediamine, pyridine, tetramethylammonium hydroxide and the like. These alkali agents are used alone or in combination of two or more.

  The conductivity of the developer used in the present invention is preferably 3 to 30 mS / cm. If it is below, usually the elution of the photosensitive composition on the surface of the aluminum plate support becomes difficult, and printing is accompanied by stains.On the other hand, if the range is exceeded, the salt concentration is high, so the elution rate of the photosensitive layer is extremely high. This is because the film is delayed and a remaining film may be formed in the unexposed area. Particularly preferred conductivity is in the range of 5-20 mS / cm.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
[Examples 1 to 10 and Comparative Examples 1 to 5]
(Method for making aluminum support)
An aluminum plate having a thickness of 0.3 mm was etched by being immersed in 10% by mass sodium hydroxide at 60 ° C. for 25 seconds, washed with running water, neutralized with 20% by mass nitric acid, and then washed with water. This was subjected to an electrolytic surface roughening treatment in a 1% by mass nitric acid aqueous solution using a sinusoidal alternating waveform current at an anode time electricity of 300 coulomb / dm ² . Subsequently, after dipping in a 1% by mass aqueous sodium hydroxide solution at 40 ° C. for 5 seconds and then in a 30% by mass sulfuric acid aqueous solution and desmutting at 60 ° C. for 40 seconds, the current density in a 20% by mass sulfuric acid aqueous solution was 2A / current density. At dm ² , the anodization treatment was performed for 2 minutes so that the thickness of the anodized film was 2.7 g / m ² . When the surface roughness was measured, it was 0.3 μm (Ra display according to JIS B0601).

[Coating undercoat layer]
Next, an undercoat layer coating solution of the following composition was applied to the aluminum support with a wire bar, and dried at 90 ° C. for 30 seconds using a hot air dryer. The coating amount after drying was 10 mg / m ² .

(Coating liquid for undercoat layer coating)
Ethyl methacrylate and 2-acrylamido-2-methyl-1-
Propanesulfonic acid sodium salt copolymer with a molar ratio of 75:25 (molecular weight 18,000) 0.1 g
2-Aminoethylphosphonic acid 0.1g
50g of methanol
Ion exchange water 50g

[Coating of photosensitive layer]
On the undercoat layer, a photosensitive layer coating solution having the following composition was prepared, applied with a wheeler so that the film thickness after drying was 0.15 g / m ^2, and dried at 100 ° C. for 1 minute.

(Photosensitive layer coating solution)
Ethylenically unsaturated bond-containing compound: Compounds listed in Table 1 and amounts added Binder: 1.8 g of the following structure

Sensitizing dye: 0.1 g of the compounds in Table 1
Polymerization initiator: 0.15 g of the following structure

  Sensitization aid: 0.2g

Colored pigment dispersion: 1.5 g of the following composition
Thermal polymerization inhibitor: 0.01 g of N-nitrosophenylhydroxylamine
Surfactant: Dainippon Ink & Chemicals, Inc. Megafac F176 0.02g
Methyl ethyl ketone 20.0g
Propylene glycol monomethyl ether 20.0g

<Composition of pigment dispersion>
Pigment Blue 15: 6 15 parts by mass Allyl methacrylate / methacrylic acid copolymer 10 parts by mass (copolymerization molar ratio 83/17) Thermal polymerization Cyclohexanone 15 parts by mass Methoxypropyl acetate 20 parts by mass Propylene glycol monomethyl ether 40 parts by mass

[Coating of protective layer]
A protective layer coating solution having the following composition was coated on the photosensitive layer so that the dry coating mass was 2 g / m ² and dried at 100 ° C. for 2 minutes.
<Coating solution composition of protective layer>
4 g of polyvinyl alcohol (degree of saponification 98 mol%, degree of polymerization 550)
Polyvinylpyrrolidone (molecular weight 100,000) 1g
95g of water

The photosensitive lithographic printing plate obtained above was made by the following method and evaluated for sensitivity and printing durability.
(exposure)
For Examples 8 to 10 and Comparative Examples 4 and 5, the amount of light was adjusted so that the amount of light on the plate surface was 0.2 mJ / cm ² with an internal drum type experimental machine equipped with a 100 mW FD-YAG laser (532 nm). Then, a gray scale was pasted on the printing plate and exposed from above. The gray scale is made so that the amount of light changes by 1 / √2, and the higher the number of gray scale steps, the higher the sensitivity. At the same time, a GATF chart with 1 to 99% halftone dots (200 lines) was exposed.
For Examples 1 to 7 and Comparative Examples 1 to 3, the amount of light on the plate surface was adjusted to 0.1 mJ / cm ² with an internal drum type experimental machine equipped with a 30 mW violet laser (405 nm). The same exposure was performed.

(Development / plate making)
Fuji Photo Film Co., Ltd. automatic processor LP-850P2 (preheat temperature is 100 ° C.) was charged with the following developer and Fuji Photo Film Co., Ltd. finisher FP-2W, each having a developer temperature of 30 ° C. and a development time of 18 seconds. The plate exposed under the conditions was developed / plate making to obtain a lithographic printing plate.

(PH 11.6 aqueous solution having the following composition)
Sodium hydroxide 0.15 parts by mass The following structural compound 5.0 parts by mass Ethylenediaminetetraacetic acid / 4Na salt 0.1 parts by mass Water 94.75 parts by mass

The sensitivity measurement was performed under the above conditions.
For evaluation with a small dot, the image of the small dot portion of the GATF chart was enlarged with a loupe, and the minimum halftone dot remaining as a clear dot was examined.
The printing durability was determined by examining the number of printed sheets in which a solid image produced under the above conditions was worn away in the printing process and no ink was applied. The printer used was a R201 type printer manufactured by Man Roland, and the ink used was GEOS G black (N) manufactured by Dainippon Ink.
The evaluation results are shown in Table 1.

ATMMT: Pentaerythritol tetraacrylate TMP-A: Trimethylolpropane triacrylate

  From Table 1, it became clear that the present invention has higher sensitivity and higher printing durability than the comparative examples, and good dot marks.

[Examples 11 to 16, Comparative Examples 6 to 7]
(Method for making aluminum support)
An aluminum plate of material 1S having a thickness of 0.30 mm was used with a No. 8 nylon brush and an 800 mesh Bamiston water suspension, and the surface was grained and washed thoroughly with water. Etching was performed by immersing in 10% sodium hydroxide at 70 ° C. for 60 seconds, washing with running water, neutralizing and washing with 20% HNO ₃ , and washing with water. This was subjected to an electrolytic surface roughening treatment in a 1% nitric acid aqueous solution with a galvanostatic quantity of 300 coulomb / dm ² using a sinusoidal alternating current under the condition of V _A = 12.7V. When the surface roughness was measured, it was 0.45 μm (Ra indication). Subsequently, after dipping in 30% H ₂ SO ₄ aqueous solution and desmutting at 55 ° C. for 2 minutes, a cathode was placed on the grained surface in 33 ° C. and 20% H ₂ SO ₄ aqueous solution to obtain a current density. When anodized at 5 A / dm ² for 50 seconds, the thickness was 2.7 g / m ² .

[Coating undercoat layer]
Next, an undercoat layer coating solution of the following composition was applied to the aluminum support with a wire bar, and dried at 90 ° C. for 30 seconds using a hot air dryer. The coating amount after drying was 10 mg / m ² .
(Coating liquid for undercoat layer coating)
90g of methanol
10g of pure water
0.01g of the following structural compound

[Coating of photosensitive layer]
A photosensitive solution having the following composition was prepared on the undercoat layer, applied with a wheeler so that the film thickness after drying was 0.15 g / m ^2, and dried at 120 ° C. for 2 minutes.

(Photosensitive layer coating solution (photopolymerizable composition): details are given in Table 2)

Binder: The binder in Example 1 was changed to the following.
Urethane resin (the following structure) 1.5g

Coating of the protective layer, plate making and evaluation were carried out in the same manner as in Example 1. Examples 11-14 and Comparative Example 6 were exposed with a 30 mW violet laser, and Examples 15-16 and Comparative Example 7 were exposed with a 100 mW FD-YAG laser.
The results are shown in Table 2.

  From Table 2, it was found that the present invention has higher sensitivity and higher printing durability than the comparative examples, and has good dot marks.

Claims (3)

  In a photosensitive lithographic printing plate having a photopolymerizable photosensitive layer containing an addition-polymerizable compound having at least two ethylenically unsaturated double bonds, an alkali-soluble or swellable binder, and a photopolymerization initiation system on a support The photopolymerizable photosensitive layer as an addition-polymerizable compound having at least two ethylenically unsaturated double bonds (a) having 3 or more ethylenically unsaturated groups in one molecule and a molecular weight of 800 A compound selected from the following acrylates and methacrylates and (b) a compound selected from epoxy acrylate compounds and epoxy methacrylate compounds having 2 or 3 ethylenically unsaturated groups in one molecule, Photosensitive lithographic printing plate.   2. The photosensitive lithographic printing plate according to claim 1, wherein the photosensitive wavelength of the photopolymerization initiation system is in the range of 350 nm to 450 nm.   (A) a compound selected from acrylates and methacrylates having 3 or more ethylenically unsaturated groups in one molecule and a molecular weight of 800 or less; and (b) 2 or 3 ethylenically unsaturated groups in one molecule. 2. The photosensitive lithographic printing plate according to claim 1, wherein the mass ratio of the epoxy acrylate compound to the compound selected from the epoxy methacrylate compound is in the range of 9: 1 to 2: 8.