JPH10244773A - Laser-direct photosensitive lithographic printing plate requiring no wetting water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser direct photosensitive lithographic printing plate requiring no wetting water which shows high sensitivity, superb print image reproducibility and also outstanding print suitability under the excellent balance of these elements. SOLUTION: In the laser direct photosensitive lithographic printing plate requiring not wetting water constructed of at least, a photosensitive layer containing a near infrared absorbent and a silicone rubber layer formed in that order on a base, titanium black is contained as the near infrared absorbent and 50% or more of the titanium black are of a particulate diameter ranging from 0.1 to 2.0μm and dispersed in the photosensitive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser direct dampening solution-free photosensitive lithographic printing plate capable of forming a printing plate directly from digital image data using a near-infrared semiconductor laser. More specifically, the present invention relates to a laser direct dampening solution-free photosensitive lithographic printing plate comprising a substrate and a photosensitive layer and a silicone rubber layer applied in this order.

[0002]

2. Description of the Related Art In recent years, with the progress of digital image processing technology using a near-infrared semiconductor laser and a computer, a photosensitive lithographic plate has been directly used from digital image data formed on a computer without using a silver halide film for a printing plate. The printing plate is subjected to scanning exposure with a near-infrared semiconductor laser to insolubilize the exposed portion, and then an image is formed by an aqueous solution development process (wet development process) to make a plate, or the exposed portion is deteriorated, sublimated, melted and removed. Laser direct plate making technology, in which an image is formed by performing a dry development process to make a plate, has attracted attention. In particular, there is no need to consider the balance between water and printing ink, the printing operation is easy, there is little wasted paper at the beginning of printing, and the printing time is short. It is expected as a new printing system because it can produce printed matter.

[0003] Various attempts have been made with respect to a laser-direct fountain-free photosensitive lithographic printing plate used in the fountain-free digital printing system.
(A) A photosensitive layer and a silicone rubber layer are applied in this order on a support, and the silicone rubber layer is simultaneously melted in response to heat generated by ablation of an exposed portion of the photosensitive layer.
Removed by volatilization or combustion (Japanese Patent Laid-Open No. 7-1
64773, 6-186750, 6-19906
(B) 7-309001), (b) those in which the silicone rubber layer is degraded in response to the heat generated by ablation of the exposed portion of the photosensitive layer, the adhesiveness to the support is reduced, and then the silicone rubber layer is scraped off. Kaihei 6-55723, 6-5586
9, 6-92050) and (c) a method of forming an ink-adhesive toner image on a support provided with a silicone rubber layer by an electrophotographic method (Japanese Patent Application Laid-Open No. 51-66008). I have. Among these methods, the method (a) is considered to be more preferable because the image forming process is the simplest and the image with the normal image quality is easily obtained.

However, a photosensitive lithographic printing plate that does not require a laser direct dampening solution using the above-described ablation requires a large number of high-power semiconductor lasers because of insufficient sensitivity in practice. Of the printing ink is low, and the reproducibility of the printed image cannot be said to be sufficient.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a photosensitive lithographic printing plate which has high sensitivity, good print image reproducibility, and excellent printability due to its excellent balance. It is intended to provide.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a laser-direct fountain-free photosensitive lithographic plate having, on a substrate, a photosensitive layer containing at least a near-infrared absorbent and a silicone rubber layer in this order from the substrate. The printing plate contains titanium black as a near-infrared absorbing agent, and 50% by weight or more of the titanium black is dispersed in the photosensitive layer with a particle size of 0.1 μm or more and 2.0 μm or less. Laser direct dampening solution is required for photosensitive lithographic printing plates.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. As the substrate used in the present invention, any substrate can be used as long as it has flexibility that can be set in a normal lithographic printing machine and can withstand the load applied during printing, and is not particularly limited, including the layer configuration. . For example,
Examples thereof include papers such as coated paper and synthetic paper, metal plates such as aluminum plates, plastic films such as polyethylene terephthalate, and foams thereof. Among these, polypropylene, expandable polypropylene, polyethylene terephthalate, expandable polyethylene terephthalate, aluminum plate, or aluminum foil and other composite materials are preferable, and the substrate is used for enhancing the ablation effect of the photosensitive layer and the silicone rubber layer. Then, a metal such as aluminum or chromium may be deposited on the substrate or mirror-polished to provide a surface that reflects near-infrared light.

The thickness of the substrate is usually 10 μm to 1 mm, preferably 20 μm to 0.5 mm. The photosensitive layer used in the present invention efficiently absorbs near-infrared laser light, converts it into heat, causes ablation of the photosensitive layer and removes the photosensitive layer, and at the same time, responds to the heat generated by the silicone rubber layer. Contains titanium black as a near-infrared absorber having a function of inducing ablation, melting, volatilizing or burning, and / or removing the photosensitive layer by pressure during ablation.

The titanium black used in the present invention, in addition to the above-mentioned function as a near-infrared absorbing agent, also has a function of inducing an exothermic oxidation reaction by heat generated by photothermal conversion, thereby remarkably enhancing an ablation effect. Having. The titanium black having such a function is a titanium black containing a titanium atom that has not reached the highest oxidation number, such as titanium monoxide (TiO), and is composed of TiO crystals or TiO ₂ and TiO, TiN. Mixed crystals and the like can be mentioned. More specifically, titanium black M-13 manufactured by Mitsubishi Materials, titanium black S- manufactured by Mitsubishi Materials, Inc.
12 and the like.

The mixing ratio of the titanium black in the photosensitive layer is from 10 to 98% by weight, preferably from 20 to 90% by weight, more preferably from 20 to 80% by weight of the total solids of the photosensitive layer.
% By weight. If the blending ratio of titanium black is extremely low, the laser beam cannot be sufficiently absorbed, so that the efficiency of ablation tends to decrease. If the blending ratio of titanium black is higher than 98%, the film strength of the photosensitive layer decreases, and printing is performed. Occasionally, the silicone rubber layer and the photosensitive layer tend to peel off. In the photosensitive layer used in the present invention, in addition to the near-infrared absorber, coating properties, compatibility with the near-infrared absorber, film strength in the photosensitive layer, and enhance the effect of ablation For the purpose, organic polymeric substances can be added.

Examples of the organic polymer include unsaturated acids such as (meth) acrylic acid and itaconic acid;
Alkyl acrylate, phenyl (meth) acrylate,
Copolymers of benzyl (meth) acrylate, styrene, α-methylstyrene and the like; alkyl methacrylate and alkyl acrylate polymers represented by polymethyl methacrylate; alkyl (meth) acrylate and acrylonitrile, vinyl chloride, Copolymers of vinylidene chloride, styrene, etc .; Copolymers of acrylonitrile with vinyl chloride or vinylidene chloride; Modified cellulose having a carboxyl group in the side chain; Polyethylene oxide; Polyvinylpyrrolidone; Phenol, o-, m-, p -Cresol, and / or
Or a novolak resin obtained by the condensation reaction of xylesol with aldehyde, acetone, etc .; polyether of epichlorohydrin with bisphenol A; soluble nylon; polyvinylidene chloride; chlorinated polyolefin; copolymer of vinyl chloride and vinyl acetate Vinyl acetate polymer; copolymer of acrylonitrile and styrene; copolymer of acrylonitrile, butadiene and styrene; polyvinyl alkyl ether; polyvinyl alkyl ketone; polystyrene; polyurethane; polyethylene terephthalate isophthalate; acetyl cellulose; Cellulose; acetylbutoxycellulose; nitrocellulose; celluloid; polyvinyl butyral and the like are used. The compounding ratio of the organic polymer substance in the photosensitive layer is 1 to 60% by weight, preferably 2 to 50% by weight, and more preferably 2 to 40% by weight based on the total solids of the photosensitive layer.

When nitrocellulose is contained in the photosensitive layer among these organic high-molecular substances, nitrocellulose is decomposed at the time of exposure to light and gas is generated, so that the efficiency of ablation is increased, which is preferable. . Next, a method for producing the photosensitive layer used in the present invention will be described. Paint shaker, bead mill, ball mill, three rolls using titanium black as described above in an appropriate coating solvent,
Dispersion is performed using a pigment dispersion device such as a kneader to prepare a titanium black dispersion. At this time, in order to facilitate dispersion, an ethylenic compound, an organic polymer substance, an anionic, cationic or nonionic surfactant, a silane coupling agent, an aluminum coupling agent, a titanate coupling agent, etc. are added. Is preferred. In particular, it is preferable to carry out a dispersion treatment together with an ethylenic compound or an organic polymer substance since aggregation of titanium black in a subsequent step can be prevented.

At the time of dispersion, it is preferable to carry out a preliminary dispersion treatment using a three-roll or kneader. Next, the remaining components of the photosensitive composition are mixed with the titanium black dispersion and stirred to produce a photosensitive composition. Using the photosensitive composition thus manufactured, 50% by weight or more of titanium black, which is a feature of the present invention, is dispersed in the photosensitive layer with a particle size of 0.1 μm to 2.0 μm. Form a photosensitive layer. The dispersion state is from 0.1 μm to 2.0 μm
The content of titanium black dispersed in the photosensitive layer having the following particle size is preferably 70% or more, and more preferably 90% or more.

It is considered that such a dispersed state facilitates the effect of reducing the shearing force of the photosensitive layer, facilitates efficient absorption of laser light, and increases the resolution. In addition, when the particle size is extremely small, the dispersion state tends to be unstable, the viscosity of the dispersion increases, and the resolution tends to decrease due to aggregation of titanium black in the photosensitive layer. The drop is likely to occur.
The photosensitive layer of the present invention usually has a thickness of 0.2 to 5 μm,
Preferably 0.2 to 3 μm, more preferably 0.3 to
2 μm. The transmission absorbance of the photosensitive layer at the wavelength of the laser beam is usually 0.3 or more, and preferably 0.5 or more, for the photosensitive layer having a thickness of 1 μm.

The silicone rubber layer used in the present invention comprises:
It can be appropriately selected from known ones as described in the above-mentioned Japanese Patent Application Laid-Open No. 7-164773, etc., and described below, a condensation crosslinking type for curing the silicone rubber layer composition by a condensation reaction, and an addition reaction. Two types of addition-crosslinking type for curing the silicone rubber layer composition are preferably used.

The condensation-crosslinking type silicone rubber layer used in the present invention comprises, as essential components, a linear organopolysiloxane having hydroxyl groups at both ends and a reactive silane compound capable of crosslinking with the organopolysiloxane to form a silicone rubber layer. Including. Examples of the linear organopolysiloxane having a hydroxyl group at both terminals used in the present invention include a linear organopolysiloxane represented by the following general formula (I).

[0017]

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(Wherein, two R ^1's each independently represent a hydrogen atom, a methyl group, a phenyl group, or a vinyl group, and y is 1
The following integers are shown. Of the compounds represented by formula (I), those in which R ¹ is a methyl group are preferred. The weight average molecular weight (hereinafter, abbreviated as Mw) of the organopolysiloxane is from 5,000 to
1,000,000, preferably 10,000 to
1,000,000. If the Mw is extremely low, the film strength of the silicone rubber layer will be reduced, and the printing resistance will be reduced. If the Mw is extremely high, the effect of removing the silicone rubber layer by ablation will be reduced, resulting in reduced sensitivity and reduced image reproducibility. Cheap.

Further, the reactive silane compound used in the present invention reacts with the hydroxyl group of the linear organopolysiloxane having a hydroxyl group at both terminals to form a deacetic acid type, a deoxime type, a dealcohol type, a deamino type or It is a reactive silane compound having a molecular weight of 2,000 or less and having at least two functional groups capable of causing cross-linking by causing condensation such as a dehydration type. Specific examples of the functional group include functional groups represented by the following formulas.

[0020]

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[0021] (wherein, R ² may be different if, even each the same there are two R ² is an alkyl group the same atomic having from 1 to 5 carbon atoms.) Of these, functional Group is an acyloxy group (—OCO
R ² ) having three or more functional groups, or a functional group having an alkoxy group (—OR ² ) having three or more functional groups,
It is preferable to form a silicone rubber layer in a short time after the drying treatment after the application. More preferably, the functional group is an acetoxy group and the number of functional groups is 3 or more, or the functional group is an alkoxy group and the number of functional groups is 6 or more.

Examples of the reactive silane compound include compounds represented by the following general formulas (II) to (V). In the formula, Q represents a group selected from the functional groups which react with the hydroxyl groups of the above-mentioned linear organopolysiloxane having hydroxyl groups at both ends, and Q has at least two in one molecule.

[0023]

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Wherein X is an alkyl group having 1 to 5 carbon atoms;
Phenyl group, vinyl _{group, H 2 N- (CH 2)} h -, CH
₂ ＣC (CH ₃ ) CO—, CH ₂ ＣＨCHCO—,

[0025]

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Wherein R ² has 1 to 5 carbon atoms as described above.
R ³ represents an allyl group or — (CH ₂ )
It indicates _{^{q -SiR 2 3-p Q p}} , R 4 is a hydrogen atom, a carbon number 1
5 alkyl group, or a phenyl group, R ^2, R
^When each of ³ and R ⁴ is present in a plurality in the same molecule,
Each of the plurality may be the same or different,
h, j and q each represent an integer of 1 to 5, p and r each represent an integer of 1 to 3, s represents an integer of 2 to 4, t and u each represent an integer of 0 to 5 . Table 1 shows more specific examples of the reactive silane compound used in the present invention, but it is not limited to these.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

The condensation-crosslinking type silicone rubber layer used in the present invention is composed of an organic carboxylic acid, a titanium compound, and a silane compound in order to increase the reaction efficiency of the condensation crosslinking reaction between the organopolysiloxane having hydroxyl groups at both ends and the reactive silane compound. A condensation catalyst such as an acid ester, a stannate, an aluminum organic ether, and a platinum-based catalyst is appropriately mixed, and a condensation reaction is performed to cure the mixture.

The mixing ratio of the organopolysiloxane having a hydroxyl group at both terminals used in the present invention, the reactive silane compound and the condensation catalyst in the silicone rubber layer is such that the hydroxyl groups at both terminals are based on the solid content of the entire silicone rubber layer. The organopolysiloxane has 80 to 98% by weight, preferably 85 to 98% by weight, and the reactive silane compound usually has
20% by weight, preferably 2 to 15% by weight, more preferably 2 to 7% by weight, and the condensation catalyst is 0.05 to 5% by weight, preferably 0.1 to 3% by weight, more preferably 0.1 to 3% by weight.
1% by weight.

If the ratio of the reactive silane compound or the condensation catalyst is extremely high, the ink repellency decreases, and it becomes difficult to remove the silicone rubber layer during ablation.
Sensitivity and image reproducibility decrease. On the other hand, when it is extremely low, the film strength of the silicone rubber layer is reduced, and the printing durability is reduced.

In order to increase the ink repellency of the silicone rubber layer, a polysiloxane other than the above-mentioned polyorganosiloxane having a hydroxyl group at both ends is added to the silicone rubber layer. 2 to 15% by weight, preferably 3 to 12% by weight based on the solid content
% By weight. As the polysiloxane, for example, Mw1 in which both terminals are trimethylsilylated
And a polydimethylsiloxane of 000 to 1,000,000.

Next, an addition-crosslinking type silicone rubber layer used in the present invention comprises an organopolysiloxane having at least two aliphatic unsaturated groups in one molecule, and a silicone rubber layer formed by crosslinking with the organopolysiloxane. An organopolysiloxane having at least two Si—H bonds in one molecule to be formed is contained as an essential component.

The organopolysiloxane having at least two aliphatic unsaturated groups in one molecule used in the present invention may have any of a linear, cyclic or branched structure, but is preferably a linear structure. Examples of the aliphatic unsaturated group include alkenyl groups such as vinyl group, allyl group, butenyl group, pentenyl group and hexenyl group; cycloalkenyl groups such as cyclopentenyl group, cyclohexenyl group, cycloheptenyl group and cyclooctenyl group; ethynyl group And alkynyl groups such as propynyl group, butynyl group, pentynyl group and hexynyl group. Among these, an alkenyl group having an unsaturated bond at a terminal is preferable from the viewpoint of reactivity,
Vinyl groups are particularly preferred. The remaining substituents other than the aliphatic unsaturated groups are preferably methyl groups in order to obtain good printing ink repellency.

At least two aliphatic unsaturated groups are present in one molecule.
Mw of the organopolysiloxane having a number of
500,000, preferably 1,000 to 3.0
00,000. When the Mw is extremely low, the strength of the silicone rubber layer is reduced, the silicone rubber layer is easily damaged at the time of printing, and the printing ink repellency of the portion is reduced,
Ink easily adheres, causing printing stains. Further, when Mw is extremely high, the removal of the silicone rubber layer by ablation becomes poor, which tends to cause a decrease in sensitivity and a decrease in image reproducibility.

The organopolysiloxane having at least two Si—H bonds in one molecule used in the present invention is
The structure may be chain, cyclic, or branched,
A chain is preferred. The Si-H bond may be at the terminal or the middle of the siloxane skeleton, and the ratio of hydrogen atoms to the total number of substituents is usually 1 to 60%, preferably 2 to 50%. The remaining substituents other than hydrogen atoms are preferably methyl groups in order to obtain good printing ink repellency. The Mw of an organopolysiloxane having at least two Si—H bonds in one molecule is usually 3
00 to 300,000, preferably 500 to 20
It is 0000. If the Mw is extremely high, the sensitivity and the image reproducibility tend to decrease.

The above-mentioned organopolysiloxane having at least two aliphatic unsaturated groups in one molecule and S in one molecule
In order to carry out the addition reaction of the organopolysiloxane having at least two i-H bonds, an addition reaction catalyst is usually used. The addition reaction catalyst can be arbitrarily selected from known catalysts, but a platinum-based catalyst is preferable, and one or a mixture of two or more selected from platinum group metals and platinum group compounds is used. Examples of the platinum group metal include a simple substance of platinum (for example, platinum black), a simple substance of palladium (for example, palladium black), and a simple substance of rhodium. Examples of the platinum group compounds include chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, platinum-ketone complexes, complexes of platinum and vinylsiloxane, tetrakis (triphenylphosphine) platinum, tetrakis (triphenylphosphine) palladium and the like. Is exemplified. Among these, chloroplatinic acid or a platinum-olefin complex is used as an alcohol-based solvent,
A solvent dissolved in a ketone solvent, an ether solvent, a hydrocarbon solvent or the like is particularly preferable.

The compounding ratio of each composition for forming the above-mentioned silicone rubber layer is such that the organopolysiloxane having at least two aliphatic unsaturated groups in one molecule is 80% based on the total solid content of the silicone rubber layer. To 98% by weight, preferably 85 to 98% by weight, and the organopolysiloxane having at least two Si—H bonds in one molecule is 2% by weight.
-20% by weight, preferably 2-15% by weight, and the addition reaction catalyst is 0.00001-10% by weight, preferably 0.0001-5% by weight.

If the compounding ratio of the organopolysiloxane having at least two Si-H bonds in one molecule is extremely low, the film strength of the silicone rubber layer is reduced, and the repellency and printing resistance of the printing ink are reduced. Is extremely high, sensitivity and image reproducibility decrease. In addition, in addition to the above composition, the addition-crosslinking type silicone rubber layer used in the present invention, for the purpose of further increasing the film strength of the silicone rubber layer,
An amino-based organosilicon compound having a hydrolyzable group represented by the following general formula (VII) can be added.

[0041]

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(In the formula (VI), Z represents a hydrolyzable group,
R ⁵ represents a divalent hydrocarbon group; R ⁶ represents a monovalent optionally substituted hydrocarbon group; and two R ^{7 s} each independently represent a hydrogen atom or a monovalent substituted group. a group represented by the good hydrocarbon group or _{^{-R 5 -SiR 6 3-p Z}} p, p is an integer of 1-3. )

The hydrolyzable group represented by Z includes, for example, an alkoxy group such as a methoxy group, an ethoxy group and a propoxy group; an alkenyloxy group such as a 2-propenyloxy group; an aryloxy group such as a phenoxy group; And an acyloxy group such as a group. Among these, a methoxy group, an ethoxy group, and an acetyloxy group are preferred in terms of stability, curability, and the like. Examples of the divalent hydrocarbon group for R ⁵ include:

[0044]

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Is preferred. Examples of the monovalent hydrocarbon group which may be substituted among the substituents represented by R ⁶ and R ⁷ include, for example, alkyl groups such as methyl group, ethyl group, propyl group and butyl group; cyclopropyl group, cyclobutyl Group,
Cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group such as cyclooctyl group; vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, etc. alkenyl group; cyclopentenyl group, cyclohexenyl group, cycloheptenyl group, Cycloalkenyl groups such as cyclooctenyl group; substituted alkyl groups such as glycidoxypropyl group, acryloxypropyl group, methacryloxypropyl group and aminoethyl group. From the viewpoint of curability, R ⁶ and R ⁷ are preferably a vinyl group, an allyl group, a glycidyl group, a methacryl group, or a γ-glycidoxypropyl group.

Specific examples of the amino silicon compound include, for example, 3- [N-allyl-N- (2-aminoethyl)] aminopropyltrimethoxysilane and 3- (N-
Allyl-N-glycidyl) aminopropyltrimethoxysilane, 3- (N-allyl-N-methacryl) aminopropyltrimethoxysilane, N-glycidyl-N, N-
Bis [3- (methyldimethoxysilyl) propyl] amine, N-glycidyl-N, N-bis [3- (trimethoxysilyl) propyl] amine, aminopropyltrimethoxysilane, aminopropyltriacetyloxysilane, 3- [ N-allyl-N- (2-aminoethyl)] aminopropyltriacetyloxysilane, 3- (N-allyl-N-glycidyl) aminopropyltriacetyloxysilane, 3- (N-allyl-N-methacryl) amino And propyltriacetyloxysilane.
These may be used as a mixture of two or more.

The content of the amino organosilicon compound is 0 to 10% by weight, preferably 0 to 5% by weight, based on the total solid content of the silicone rubber layer. In addition, a curing retarder can be added to the addition-crosslinking type silicone rubber layer used in the present invention in order to prevent rapid curing of the silicone layer composition when the silicone rubber layer is applied. The curing retarder can be arbitrarily selected from commonly known acetylenic alcohols, maleic esters, silylated acetylenic alcohols, silylated maleic acids, triallyl isocyanurate, vinyl siloxane, and the like.

The amount of the curing retarder to be added varies depending on the desired curing speed, but is usually 0.0001 to 1.0 part by weight based on the total solid content of the silicone rubber layer. The condensation-crosslinking type and addition-crosslinking type silicone rubber layers used in the present invention may be added with an inorganic filler such as silica, titanium oxide, and aluminum oxide for the purpose of improving the strength. Is preferably used. As such a filler, those having an average particle diameter of 500 μm or less are preferred from the viewpoint of dispersibility or dispersion stability.

These silicone rubber layers have excellent printing ink repellency and printing resistance, are easily removed by ablation, and have a function of providing high sensitivity and high image reproducibility. The silicone rubber layer has a scratch strength of 10 to 1
It is preferably 00 g. However, the scratch strength means the weight (g) required to generate a scratch when a 0.2 mm sapphire needle is moved at a speed of 10 cm / min while applying a load on the printing plate. Represent. When the scratch strength is in the above range, printability such as repellency, printing resistance, sensitivity, and image reproducibility of the printing ink becomes good. The thickness of the silicone rubber layer used in the present invention is 0.1 to 10
μm, preferably 0.2 to 5 μm, more preferably 0.3 to 2 μm.

The photosensitive layer composition and silicone rubber layer composition described above are dissolved in a suitable solvent to form a solution,
After applying this on the substrate by various coating devices such as a wire bar, a spinner and a roll coater on the support,
After drying, a photosensitive layer and a silicone rubber layer can be respectively formed. Examples of the coating solvent for the photosensitive layer include ketones such as methyl ethyl ketone and cyclohexanone; esters such as butyl acetate, amyl acetate and ethyl propionate; and hydrocarbons such as toluene, xylene, monochlorobenzene, carbon tetrachloride, trichloroethylene, and trichloroethane. And halogenated hydrocarbons, methylcellosolve, ethylcellosolve, ethers such as tetrahydrofuran, and further, propylene glycol monomethyl ether acetate, bentoxone, dimethylformamide and the like can be used in common use.As a coating solvent for the silicone rubber layer, n-hexane, cyclohexane,
Petroleum ether, aliphatic hydrocarbon solvent Exxon Chemical Co., Ltd .: Isopar E, H, G, and a mixed solvent of these solvents and the above-mentioned photosensitive layer coating solvent can be used.

When the silicone rubber layer used in the present invention is applied, an adhesive layer is provided between the photosensitive layer and the silicone rubber layer in order to enhance the adhesiveness between the photosensitive layer and the silicone rubber layer. Can be provided. In this adhesive layer,
In general, the organic polymer substance described in the description of the photosensitive layer and the silicone rubber described in the description of the silicone rubber layer can be appropriately selected and used. A combination composition of a molecular substance or a condensation-type reactive silane compound such as a polyfunctional alkoxysilane or a polyfunctional acetoxysilane, and polydimethylsiloxane having a reactive group such as a hydroxyl group at both terminals or in the main chain is used. More specifically, Toyobo Co., Ltd. Byron 300, Byron UR8200, Toray Silicone Co., Ltd. Primer A, Primer B, Primer C, Primer D, Primer D2, Primer E, Takeda Pharmaceutical Takenate A367H and Takenate A- 7, Takenate A-9690 and Takenate A-
5, a combination of Takenate A-968 and Takenate A-8, and the like. These adhesive layers are usually applied and dried so as to have a dry film thickness of 0.05 to 10 μm, preferably 0.1 to 2 μm.

If necessary, for the purpose of protecting the silicone rubber layer, various release plastic sheets such as a polypropylene sheet, a polyethylene sheet, a release-treated polyethylene terephthalate, a release-treated paper, aluminum, iron,
It can be provided by laminating a metal sheet such as copper on the silicone rubber layer. The photosensitive printing plate provided with the photosensitive layer and the silicone rubber layer on the substrate is usually 680 to 680.
Scanning exposure is performed by a beam spot in which a semiconductor laser light emitting near-infrared light of 1200 nm is condensed to a diameter of 5 to 30 μm, and the exposed portion is ablated, and then used as a printing plate without post-processing. To remove the fine particles of the photosensitive layer or silicone rubber layer generated by ablation attached to the exposed printing plate, brush, pad, ultrasonic Post-treatment for giving a physical stimulus such as spray or the like may be performed.

Another method for removing fine particles generated by the ablation is as follows. A cover sheet having a surface having a higher adhesiveness to the fine particles than the silicone rubber layer is exposed to the silicone rubber layer of a photosensitive printing plate. On top, after laminating so that the silicone rubber surface and the adhesive cover sheet surface match, before peeling off or before exposure,
A method of laminating a cover sheet that transmits laser light in the same manner as described above, peeling after exposure, and removing fine particles on the silicone rubber layer may be used.
Examples of the cover sheet include a base plate made of polyethylene terephthalate, polypropylene, polycarbonate, paper, and the like, on which an adhesive layer made of silicone rubber, ionomer, vinyl acetate, or the like is provided as necessary.

[0054]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. Examples 1 to 7, Comparative Examples 1 to 3 A titanium black dispersion having the following composition was
After kneading, mixing, and degreasing for a period of time, the mixture was passed through a roll 14 times by a three-roll mill to perform a dispersion treatment.

[Titanium Black Dispersion Composition] Titanium Black; Titanium Black described in Table 2 Amount shown in Table 2 Organic polymer substance A; Compound shown in Table 2 Amount shown in Table 2 Coating solvent: 100 parts by weight of propylene glycol monomethyl ether acetate Subsequently, 0.5 m of 3.6 times by weight with respect to the dispersion.
Dispersion treatment was performed for 5 hours using a paint shaker containing m-diameter zirconia beads to prepare a titanium black dispersion. Next, the following photosensitive layer coating solution components were added to the dispersion, and after stirring for 30 minutes, ultrasonic stirring was performed for 1 hour using an ultrasonic cleaning device to prepare a photosensitive layer coating solution.

[Components of coating solution for photosensitive layer] Organic polymer substance B; compounds listed in Table 2 Amounts listed in Table 2 Coating solvent: propylene glycol monomethyl ether acetate 900 parts by weight Photosensitized in this manner Coating liquid having a thickness of 140
Coated with a wire bar coater on a foamed polypropylene sheet having a thickness of 1 μm (Synthetic paper manufactured by Oji Yuka Synthetic Paper Co., Ltd., Yupo GWG), and dried at 85 ° C. for 3 minutes.
Was provided. Subsequently, a silicone rubber layer composition having the following composition was applied on the photosensitive layer.

[Silicone Rubber Layer Composition] Polydimethylsiloxane having hydroxyl groups at both ends: The following compound (y represents an integer of 1 or more)

[0058]

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Reactive silane compound: 7 parts by weight of Si4 shown in Table 1 Condensation catalyst: 0.8 part by weight of cibutyltin dilaurate Coating solvent: 900 parts by weight of Isopar E (manufactured by Exxon Chemical Co., Ltd.) After drying for 1 minute, a silicone rubber layer having a dry film thickness of 1 μm was provided to prepare a photosensitive sample.

The photosensitive sample was fixed on a rotating drum having a circumference of 20 cm so that the silicone rubber layer was on the outside, and the drum was rotated. Next, 830 is placed on the rotating sample.
nm, 30mW semiconductor laser light (Hitachi, Ltd.,
HL8325G) was condensed to a beam diameter of 15 μm, and scanning exposure was performed. Subsequently, the following items were evaluated. Table 2 shows the results.

[Sensitivity] The surface of the printing plate image-exposed at various scanning speeds was lightly rubbed with absorbent cotton soaked in water to remove the scattered silicone rubber layer residue by ablation.
The printing plate was mounted on a Mitsubishi Heavy Industries printing machine DAIER 1F-2, and 3000 sheets were printed on Mitsubishi Toshibishi Art Paper using printing ink for lithographic printing plates (Aqualess Echo Red manufactured by Toyo Ink Co., Ltd.). And find the one with the highest scanning speed among the print images reproduced on the 3000th art paper,
The sensitivity was evaluated using the scanning speed at that time. The higher the scanning speed, the higher the sensitivity.

[Printed Image Reproducibility] In the same manner as in the sensitivity evaluation, scanning exposure was performed at the maximum scanning speed, 3000 sheets were printed, and a fine line image reproduced on art paper was observed with a microscope of 400 times magnification. Was evaluated. A: A fine line image of 90% or more was reproduced. B: A fine line image of 70% or more and less than 90% was reproduced. C: A fine line image of 50% or more and less than 70% was reproduced. D: Reproducibility of the fine line was 30% or less.

[Dispersion state] The surface of the unexposed printing plate was set at 40
Observed with a microscope of 0 magnification, and further, the cross section of the sample was 1000
The dispersion state of titanium black in the photosensitive layer was evaluated by observing with a transmission microscope at a magnification of 00. A: 90% by weight or more of titanium black contained in the photosensitive layer had a particle size of 0.1 to 2.0 μm. B: 70% by weight or more and less than 90% by weight of titanium black had a particle size of 0.1 to 2.0 μm. C: 50% by weight or more and less than 70% by weight of titanium black had a particle size of 0.1 to 2.0 μm. D: 50% by weight or less of titanium black is 0.1 to 2.0.
The particle size was μm.

[0064]

[Table 4]

[0065]

[Table 5] * 1: The values in parentheses indicate the mixing ratio (parts by weight).

In Table 2, the abbreviations in the column of the near-infrared absorbing agent are (S
-1, S-2, and S-3) represent the following, respectively. S-1: Titanium black 13M manufactured by Mitsubishi Materials Corporation S-2: Titanium black 12S manufactured by Mitsubishi Materials Corporation S-3: Carbon black MA-100 manufactured by Mitsubishi Chemical Corporation In Table 2, abbreviations in the column of organic polymer substance (P -1, P-
2, P-3 and P-4) respectively represent the following. P-1:

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Each of the above units represented by a: b: c:
d ≒ Mw = 100 contained in a molar ratio of 55:20:10
00: 30 parts by weight The unit described in P-2: P-1 is a: b: c: d ≒ 5
Mw = 6000 polymer substance contained at a molar ratio of 5: 30: 0 P-3: phenoxy resin (manufactured by Union Carbide Co., Ltd .;
KH-J) P-4: polyhydroxystyrene (Mw = 5000)

Example 8 In Example 1, Toray Co. primer D was applied on the photosensitive layer and dried to form a primer layer having a dry film thickness of 0.3 μm. The substitute was applied and dried to provide a silicone rubber layer having a dry film thickness of 1 μm. Other than that, the exposure and evaluation were performed in the same manner as in Example 1. As a result, a sensitivity of 80 cm / s and a print image reproducibility A were obtained.

[Silicone Rubber Layer Composition] Polydimethylsiloxane having hydroxyl groups at both ends: The following compound (y represents an integer of 1 or more)

[0071]

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Reactive silane compound: 7 parts by weight of Si23 shown in Table 1 Condensation catalyst: 0.8 part by weight of dibutyltin diurarate Coating solvent: 900 parts by weight of Isopar E (manufactured by Exxon Chemical Co.)

[0073]

According to the present invention, it is possible to provide a photosensitive lithographic printing plate which is excellent in sensitivity and image reproducibility and requires no laser dampening solution.

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Claims (5)

[Claims] 1. A laser-direct fountain-free photosensitive lithographic printing plate having a photosensitive layer containing at least a near-infrared absorbing agent and a silicone rubber layer in this order on a substrate, wherein the near-infrared absorbing agent is used. Contains titanium black, and 50% by weight or more of the titanium black is 0.1 μm
A photosensitive lithographic printing plate requiring no laser direct dampening solution, wherein the photosensitive lithographic printing plate is dispersed in the photosensitive layer with a particle size of 2.0 μm or less. 2. The photosensitive material according to claim 1, wherein said silicone rubber layer contains a linear organopolysiloxane having hydroxyl groups at both ends and a reactive silane compound. Sexographic printing plate. 3. The photosensitive lithographic printing plate according to claim 2, wherein the reactive silane compound has six or more alkoxy groups in one molecule. 4. The photosensitive lithographic printing plate according to claim 2, wherein the reactive silane compound has three or more acetoxy groups in one molecule. 5. The photosensitive lithographic printing plate according to claim 1, wherein the photosensitive layer contains nitrocellulose.