JP2005280074A - Original plate of lithographic plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an original plate of a lithographic plate which enables improvement of plate wear resistance. <P>SOLUTION: This original plate of the lithographic plate is constituted in such a manner that the upper layer of an image recording layer 16 formed on a substrate 12 contains a pigment having a photothermal conversion rate not so high as that of dye, but being hardly discolored by light, while the lower layer of the layer 16 contains a dye having a high photothermal conversion efficiency, but tending to be discolored by the light. On the occasion when the image recording layer 16 is exposed to the image recording light, the temperature is raised by making the upper layer part hardly discolored by the light absorb the light so that the light be attenuated moderately, and the lower layer part is heated at once by the light passing through the upper layer and being attenuated, while the dye is kept from being discolored by the light. Thereby the temperature of the interface between the image recording layer 16 and the substrate 12 is raised efficiently. Thus the image recording layer 16 in the region of the interface is hardened firmly and the plate wear resistance is improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal recording type lithographic printing plate precursor that contains a polymerizable compound and a compound that generates a polymerization initiator in an image recording layer provided on a support, and is configured to be exposed.

  In general, a photosensitive lithographic printing plate precursor (so-called PS plate) is used for offset printing. In the field of lithographic printing, a lithographic printing plate precursor used for a CTP (Computer to Plate) system for directly making a printing plate by performing laser exposure processing based on digital data from a computer or the like has been proposed.

  Conventionally, in such a CTP system, an on-press development system has been proposed in which a lithographic printing plate precursor is exposed and developed without being subjected to development processing, and is mounted on a printing press for printing. In other words, the CTP system uses a recording layer (photosensitive layer) that can remove the non-image portion of the printing plate precursor in a normal printing process, and after the exposure on the printing machine without performing the development process. Development is performed to obtain a final printing plate (so-called on-press development system).

  In this on-press development system, an aluminum plate having a hydrophilic surface which is anodized and roughened is used as a support, and can be combined on the hydrophilic surface under the influence of heat. In addition, a recording layer (photosensitive layer) comprising hydrophobic thermoplastic polymer particles dispersed in a hydrophilic binder is formed, and the recording layer or a layer adjacent thereto contains a compound that converts light into heat. A lithographic printing plate which is a so-called thermal recording type (heat mode) printing plate is used.

  In this on-press development system, exposure processing for a lithographic printing plate precursor, which is a thermal recording type (heat mode) printing plate, is performed by, for example, infrared (IR) rays or a laser beam (LED, Using a laser diode).

  In the exposure process for the lithographic printing plate precursor which is a printing plate of the thermal recording type (heat mode), the laser beam irradiated on the recording layer corresponding to a required image is converted into heat and included in the recording layer. Hydrophobic thermoplastic polymer particles are heated to a temperature equal to or higher than the coagulation temperature to coagulate to form a hydrophobic agglomerate in the hydrophilic layer so that it becomes insoluble in ordinary water or an aqueous liquid and does not fall off and disperse.

  In this on-press development system, the lithographic printing plate precursor thus exposed is placed on, for example, a printing cylinder of a printing press, and then the printing press is started to record the recording layer of the lithographic printing plate precursor. The recording layer of the lithographic printing plate precursor is moved by rolling a dampening roller for supplying an aqueous dampening solution onto the recording layer, and the ink roller is further rolled on the recording layer of the lithographic printing plate precursor to perform the printing operation. Development is carried out by removing and dispersing the other hydrophilic layer portions in ordinary water or aqueous liquid, leaving the coagulated (cured) hydrophobic agglomerates. Normally, for example, after the rotation of the printing cylinder about 10 times, the first clean and useful printing is obtained (for example, see Patent Document 1).

  Furthermore, a conventional lithographic printing plate precursor that can be developed on a printing press (a lithographic printing plate precursor that forms an image by defilming and dispersing with water or a fountain solution after exposure) is provided on a support of the lithographic printing plate precursor. The recording layer of the image contains microcapsules containing at least an ethylenically unsaturated compound and a polymerization initiator as active substances, and there is an active substance diffused from the microcapsules on and near the surface of the microcapsules. The image recording layer is exposed to actinic rays to cure the image recording layer film to form a continuous strong film. The unexposed film is washed off with water or an aqueous liquid. It has been proposed to remove a membrane by removing the membrane with water or an aqueous liquid. (For example, refer to Patent Document 2).

  In the conventional on-press development system as described above, as shown in FIGS. 6B and 6C, an aluminum support is used as a support for the planographic printing plate 17 which is a thermal recording (heat mode) printing plate. No. 11 is used, and when laser exposure processing is further performed, high in a range that does not cause ablation (a phenomenon in which the irradiated portion is burned off with strong energy) in the vicinity of the upper surface in the thickness direction of the recording layer 15 of the planographic printing plate 17 Heat sufficiently above the solidification temperature by the laser beam irradiated at the output.

  However, the recording layer 15 of the lithographic printing plate 17 that is a conventional thermal recording type (heat mode) printing plate is uniformly composed of a material having a predetermined light absorption coefficient.

  For this reason, when the thermal recording type (heat mode) lithographic printing plate 17 is exposed to laser light, as shown in FIG. 6A, the light energy absorbed by the recording layer 15 is incident on the laser light. Since the recording layer 15 is larger on the upper surface (front surface) side in the thickness direction, and becomes smaller as it goes to the lower surface in the thickness direction (aluminum support side), the recording layer 15 in the recording layer 15 is exemplified as shown in FIG. It is difficult to sufficiently raise the temperature in the vicinity of the lower surface in the thickness direction of the layer. That is, it is difficult to increase the sensitivity of the lithographic printing plate 17 as the temperature in the vicinity of the lower surface in the thickness direction of the recording layer 15 can be sufficiently increased.

  Further, when the sensitivity of the planographic printing plate 17 is low, the heat converted from the irradiated laser light near the lower surface in the thickness direction of the recording layer 15 (near the hydrophilic surface 13 that is an anodized film). Even when the laser beam is irradiated with the maximum output that does not cause ablation because the energy is rapidly diffused and escapes toward the aluminum support 11 having a high thermal conductivity, the hydrophilic surface 13 and the recording layer 15 ( The temperature in the vicinity of the interface with the heating recording layer) is not sufficiently raised to the solidification temperature or higher, so that the curing of the recording layer 15 portion (image portion) irradiated with the laser beam does not proceed sufficiently and the strength of the image portion is insufficient. There is a risk of becoming.

In such a low-sensitivity lithographic printing plate, when an aqueous dampening liquid is applied on the recording layer 15 for printing, the recording layer 15 is cured by exposure processing near the bottom surface (interface) in the thickness direction of the layer. If the sensitivity is not high enough to proceed sufficiently, the developing action that drops and disperses the portion with insufficient strength in water or an aqueous liquid proceeds, and the exposure in the recording layer 15 increases as the number of printed sheets increases. The formed image portion is likely to be lost and the printing durability is lowered.
Japanese Patent No. 2938397 Japanese Patent No. 2639748

  In the present invention, when the thermal recording type lithographic printing plate precursor provided with an image recording layer for forming an image provided on a support is exposed, the image recording layer in the lithographic printing plate precursor is exposed. The lithographic printing plate precursor is configured to be hardened from the upper surface side in the thickness direction to the interface side with the support so that the printing durability of the thermal recording lithographic printing plate can be improved. Objective.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by changing the characteristics of absorbing image recording light between the upper layer and the lower layer in the image recording layer formed on the support, The present invention has been solved.

  That is, the lithographic printing plate precursor according to the first aspect of the present invention has an image recording layer containing a polymerizable compound and a compound that generates a polymerization initiator on a support, and an image recording layer on the image recording layer. It includes a pigment that absorbs recording light, and a dye that absorbs image recording light is included below the image recording layer.

  The invention described in claim 2 is characterized in that in the lithographic printing plate precursor described in claim 1, a dye contained in the lower layer of the image recording layer is encapsulated in a microcapsule.

  The invention according to claim 3 is the lithographic printing plate precursor according to claim 1 or 2, which is three laminar area portions having a uniform thickness in the depth direction from the surface of the image recording layer. When assuming a model divided into upper, middle, and lower parts, the depth from the surface is such that the amount of light energy absorbed by the assumed lower layer is greater than the amount of light energy absorbed by the upper and middle parts. The image recording layer is characterized in that the light absorption coefficient is distributed over the direction.

  According to a fourth aspect of the present invention, in the lithographic printing plate precursor according to the first or second aspect, the image recording layer is a lower layer assumed to be in the vicinity of the interface with the support, and has a light absorption coefficient. The light absorption coefficient is distributed over the depth direction from the surface so as to be the highest, and is characterized in that it is configured.

  In the present invention, as described above, the upper layer of the image recording layer formed on the support has a light-to-heat conversion rate that is not as high as that of the dye, but includes a pigment that is not easily faded by light. By including a dye that is high but easily discolored by light, when the image recording layer is irradiated with image recording light, it is absorbed so that light is moderately attenuated in the upper layer portion that is difficult to photobleach. Efficiently raise the temperature of the interface between the image-recording layer and the support by raising the temperature and heating the lower layer at a stretch while preventing the dye from fading with light with light attenuated by passing through the upper layer Can do. By increasing the temperature of the interface portion in this way, the image recording layer in the interface region can be firmly solidified, the printing durability can be improved, and the sensitivity can be improved.

  According to the planographic printing plate precursor of the present invention, the exposed portion of the recording layer is cured by infrared scanning exposure based on a digital signal, and is cured from the upper surface side in the thickness direction to the interface side with the support. Thus, the printing durability of the lithographic printing plate can be improved.

A planographic printing plate precursor according to an embodiment of the present invention will be described with reference to the drawings.
(Lithographic printing plate precursor)
A schematic configuration of a cross section of the planographic printing plate precursor according to the present embodiment will be described with reference to FIG.

  This lithographic printing plate 10 uses a recording layer (photosensitive layer) that can remove a non-image portion of a printing plate precursor in a normal printing process, and after exposure, on a printing machine without performing a development process. This is a so-called on-press development system in which a final printing plate is obtained by developing the film.

  The planographic printing plate 10 includes an aluminum support 12 made of aluminum or an aluminum alloy, and an image recording layer 16 (photosensitive layer or recording layer) formed on an anodized film 14 formed on the surface of the aluminum support 12. The image recording layer 16 contains a hydrophobizing precursor and a compound that absorbs image recording light.

This lithographic printing plate 10 has a laser light absorption coefficient of the lower layer portion in the thickness direction of the image recording layer 16 so as to have a physical property of increasing the temperature of the interface portion between the image recording layer 16 and the anodized film 14 more efficiently. The laser light absorption coefficient is higher than that of the upper layer portion in the thickness direction.
(Physical properties of recording layer)
In the planographic printing plate 10, the image recording layer 16 is a layer having physical properties in which the light absorption coefficient is distributed along the depth direction from the surface (the direction from the surface toward the interface with the anodized film 14). The configuration. For example, in the image recording layer 16 of the planographic printing plate 10, the image recording layer 16 having a thickness of 1 μm is composed of a plurality of layers having different laser light absorption coefficients (the image recording layer 16 is subdivided into two or more layers). Configured).

  Here, as shown in FIGS. 3 and 5, assuming a model in which the image recording layer 16 is divided into three laminar area portions (upper, middle, and lower) having a uniform thickness in the depth direction. For example, as shown in FIG. 1 continuously from the surface or in the depth direction so that the amount of light energy absorbed by the lower layer is greater than or equal to the amount of light energy absorbed by the upper and middle portions, or FIG. As shown in FIG. 4, the layer structure is such that the light absorption coefficient is distributed in stages.

  As a specific configuration of the image recording layer 16, the configuration of the image recording layer 16 (for example, an oleophilic layer) is composed of an upper layer and a lower layer, and the entire thickness of the image recording layer 16 is 1 μm. The thickness of the upper and middle regions is 0.7 μm, and the thickness of the lower layer (lower region) is 0.3 μm.

  Here, for example, the light absorption coefficients of the upper layer (upper and middle regions) and the lower layer (lower region) are constant, respectively, and the upper layer and the entire lower layer (the entire thickness direction of the image recording layer 16) have 90% of incident light. %, And the amount of light energy absorbed in the upper and middle regions and the lower region in the image recording layer 16 is set to a, b, c, and d as shown in the table of FIG. Think. As a comparative example, e is configured such that the upper layer (upper and middle regions) and the lower layer (lower region) both have the same light absorption coefficient (the entire thickness direction of the image recording layer 16 is uniform. It is configured so that

Under the above-mentioned conditions, the heat transfer coefficient of the image recording layer 16 is set to 0.25 (W / m · K) which is the same heat transfer coefficient as that of the polymer material, and the heat transfer coefficient of the anodized film is set to 0.73 ( W / m · K), the heat transfer coefficient of aluminum is 237 (W / m · K), and the temperature rises when a 10 μm diameter (1 / e ² width) light beam is scanned and exposed at 2.5 m / sec. Was obtained by calculation, and the result shown in FIG. 5 was obtained. In the results shown in FIG. 5, the maximum temperature in the image recording layer 16 is standardized to 1 (therefore, the irradiation exposure amount is different for a, b, c, d, and e).

  From the results shown in FIG. 5, when e is the case where the light absorption coefficient of the image recording layer 16 is constant and a, b, c, d where the light absorption coefficient is distributed, the light absorption is compared. It can be seen that the temperature under the image recording layer 16 clearly rises in a, b, c, d where the coefficients are distributed. Therefore, theoretically, a layer configuration in which the light absorption coefficient is distributed by means such as adjusting the mixing state of the photothermal conversion agent so as to obtain an elevated temperature necessary for recording below the image recording layer 16 is designed. Thus, in this lithographic printing plate 10, when the image recording layer 16 is exposed to laser light, the temperature in the vicinity of the interface of the anodized film 14 in the image recording layer 16 is increased, and appropriate exposure processing is performed. You can do it.

  Further, in this image recording layer 16, as shown in FIG. 2, the image recording layer 16 is subdivided into two or more, and a layer having the highest absorption coefficient is provided in the vicinity of the interface side of the image recording layer 16 with the anodized film 14. It may be provided to constitute a distribution of the light absorption coefficient in the depth direction. In the example illustrated in FIG. 2, the lower dye density corresponding to the lower third of the image recording layer 16 is increased, and the upper 2/3 of the image recording layer 16 is configured to have a lower dye density.

  Also in the configuration of the image recording layer 16 illustrated in FIG. 2, the distribution of the light absorption coefficient is distributed so that an elevated temperature necessary for recording can be obtained at the lower portion of the image recording layer 16, similarly to the configuration shown in FIG. 1 described above. By designing the attached layer structure, when the image recording layer 16 is exposed to laser light, the temperature in the vicinity of the interface of the anodic oxide film 14 in the image recording layer 16 is increased, and appropriate exposure processing can be performed. It becomes like this.

Furthermore, in this image recording layer 16, as shown in FIG. 3, even if the amount of light energy absorbed by the upper surface is large, the amount of light energy absorbed by the lower layer is the amount of light energy absorbed by the upper and middle portions. By configuring the light absorption coefficient so as to be as described above, when the image recording layer 16 is exposed to laser light, the temperature in the vicinity of the interface of the anodized film 14 in the image recording layer 16 is increased. And appropriate exposure processing can be performed.
(Chemical composition of lithographic printing plate precursor)
Next, the chemical structure of the lithographic printing plate precursor according to the embodiment of the invention will be described.

[Image recording layer]
Examples of the hydrophobized precursor fine particles used in the recording layer (image recording layer) of the present invention include thermoplastic polymer fine particles, heat-reactive polymer fine particles, and microcapsules. Details will be described below.
As thermoplastic polymer fine particles used in the recording layer of the present invention, Research Disclosure No. 33303 of January 1992, JP-A Nos. 9-123387, 9-131850, 9-171249, 9 The thermoplastic polymer fine particles described in JP-A No.-171250, EP931647 and the like can be mentioned as preferable examples. Specific examples of the polymer constituting the polymer fine particle include homopolymers of monomers such as ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinyl carbazole, or the like. Mention may be made of copolymers or mixtures thereof. Among them, more preferred are polystyrene and polymethyl methacrylate.

  As a method for synthesizing such thermoplastic polymer fine particles, in addition to emulsion polymerization and suspension polymerization, these compounds are dissolved in a water-insoluble organic solvent, and this is mixed and emulsified with an aqueous solution containing a dispersant. Further, there is a method (solution dispersion method) in which heat is further applied to solidify into fine particles while the organic solvent is being blown away.

  Examples of the heat-reactive polymer fine particles used in the recording layer of the present invention include thermosetting polymer fine particles and polymer fine particles having a heat-reactive group.

  Examples of the thermosetting polymer include a resin having a phenol skeleton, a urea resin (for example, a urea derivative such as urea or methoxymethylated urea formed by resination with an aldehyde such as formaldehyde), a melamine resin (for example, melamine or Examples thereof include those obtained by converting the derivatives into resins with aldehydes such as formaldehyde, alkyd resins, unsaturated polyester resins, polyurethane resins, and epoxy resins. Among these, resins having a phenol skeleton, melamine resins, urea resins and epoxy resins are particularly preferable.

  Suitable resins having a phenol skeleton include, for example, phenol resins obtained by converting phenol, cresol and the like with aldehydes such as formaldehyde, hydroxystyrene resins, N- (p-hydroxyphenyl) methacrylamide, and p-hydroxyphenyl methacrylate. Examples thereof include a polymer or copolymer of methacrylamide or acrylamide or methacrylate or acrylate having a phenol skeleton.

  Such thermosetting polymer fine particles can be easily obtained by a solution dispersion method, but may be formed into fine particles when the thermosetting polymer is synthesized. However, it is not restricted to these methods.

  The thermally reactive group of the polymer fine particle having a thermally reactive group used in the present invention may be any functional group that performs a reaction as long as a chemical bond is formed, but is an ethylenically unsaturated group that performs a radical polymerization reaction. Group (for example, acryloyl group, methacryloyl group, vinyl group, allyl group, etc.), cationically polymerizable group (for example, vinyl group, vinyloxy group, etc.), isocyanate group that performs addition reaction or its block, epoxy group, vinyloxy group And a functional group having an active hydrogen atom as a reaction partner (for example, an amino group, a hydroxyl group, a carboxyl group, etc.), a carboxyl group for performing a condensation reaction, a hydroxyl group or an amino group as a reaction partner, a ring-opening addition reaction The acid anhydride to be used and the amino group or hydroxyl group as the reaction partner may be mentioned as suitable ones Kill.

  The introduction of these functional groups into the polymer fine particles may be performed at the time of polymerization, or may be performed using a polymer reaction after the polymerization.

  When introduced at the time of polymerization, it is preferable to carry out emulsion polymerization or suspension polymerization of the monomer having the above functional group. Specific examples of the monomer having the above functional group include allyl methacrylate, allyl acrylate, vinyl methacrylate, vinyl acrylate, 2- (vinyloxy) ethyl methacrylate, p-vinyloxystyrene, p- {2- (vinyloxy) ethyl} styrene, Block isocyanate with glycidyl methacrylate, glycidyl acrylate, 2-isocyanatoethyl methacrylate or alcohol thereof, block isocyanate with 2-isocyanate ethyl acrylate or alcohol thereof, 2-aminoethyl methacrylate, 2-aminoethyl acrylate, 2- Hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid, maleic anhydride, bifunctional acrylate, 2 officers Methacrylate, and the like, but not limited thereto.

  In the present invention, a copolymer of these monomers and a monomer that is copolymerizable with these monomers and does not have a thermally reactive group can also be used. Examples of the copolymer monomer having no heat-reactive group include styrene, alkyl acrylate, alkyl methacrylate, acrylonitrile, vinyl acetate, and the like. It is not limited to.

  Examples of the polymer reaction used when the heat-reactive group is introduced after polymerization include a polymer reaction described in WO96-34316.

  Among the polymer fine particles having a heat-reactive group, those in which the polymer fine particles are coalesced by heat are preferable, and those having a hydrophilic surface and being dispersed in water are particularly preferable. The contact angle (water droplets) of the film prepared by applying only polymer fine particles and drying at a temperature lower than the solidification temperature is higher than the contact angle (water droplets) of the film prepared by drying at a temperature higher than the solidification temperature. It is preferable to lower. In order to make the surface of the polymer fine particles hydrophilic in this way, a hydrophilic polymer or oligomer such as polyvinyl alcohol or polyethylene glycol or a hydrophilic low molecular weight compound may be adsorbed on the surface of the polymer fine particles. However, the surface hydrophilization method is not limited to this.

  The solidification temperature of the polymer fine particles having these thermoreactive groups is preferably 70 ° C. or higher, but more preferably 100 ° C. or higher in view of the stability over time. Within this range, good resolution and stability over time can be obtained.

  The microcapsule used in the recording layer of the present invention includes a hydrophobic compound, preferably a compound having a heat-reactive group. As this heat-reactive group, the same heat-reactive group as that used for the polymer fine particles having the heat-reactive group can be mentioned as a preferable one. Hereinafter, the compound having a thermally reactive group will be described in more detail.

  Preferred examples of the compound having a radically polymerizable unsaturated group include a compound having at least one, preferably two or more, ethylenically unsaturated bonds such as acryloyl group, methacryloyl group, vinyl group and allyl group. . Such a group of compounds is widely known as a monomer or a crosslinking agent for the polymerizable composition in the industrial field, and these can be used in the present invention without any particular limitation. The chemical form is a monomer, a prepolymer, that is, a dimer, a trimer, an oligomer, a polymer or a copolymer, or a mixture thereof.

  Specific examples include compounds described in JP-A-2001-277740 as compounds having a polymerizable unsaturated group. Typical compound examples include trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, di Examples include pentaerythritol di (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and adducts of trimethylolpropane diacrylate and xylylene diisocyanate. However, it is not limited to these.

  An example of a polymer or copolymer having an ethylenically polymerizable unsaturated group is a copolymer of allyl methacrylate. For example, allyl methacrylate / methacrylic acid copolymer, allyl methacrylate / ethyl methacrylate copolymer, allyl methacrylate / butyl methacrylate copolymer and the like can be mentioned.

  Examples of the compound having a vinyloxy group suitable for the present invention include compounds described in JP-A No. 2002-29162. Specific examples include tetramethylene glycol divinyl ether, trimethylolpropane trivinyl ether, tetraethylene glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, 1,4-bis {2- (vinyloxy) ethyloxy} Benzene, 1,2-bis {2- (vinyloxy) ethyloxy} benzene, 1,3-bis {2- (vinyloxy) ethyloxy} benzene, 1,3,5-tris {2- (vinyloxy) ethyloxy} benzene, 4 , 4′-bis {2- (vinyloxy) ethyloxy} biphenyl, 4,4′-bis {2- (vinyloxy) ethyloxy} diphenyl ether, 4,4′-bis {2- (vinyloxy) ester Ruoxy} diphenylmethane, 1,4-bis {2- (vinyloxy) ethyloxy} naphthalene, 2,5-bis {2- (vinyloxy) ethyloxy} furan, 2,5-bis {2- (vinyloxy) ethyloxy} thiophene, , 5-bis {2- (vinyloxy) ethyloxy} imidazole, 2,2-bis [4- {2- (vinyloxy) ethyloxy} phenyl] propane {bis (vinyloxyethyl) ether of bisphenol A}, 2,2- Examples include, but are not limited to, bis {4- (vinyloxymethyloxy) phenyl} propane, 2,2-bis {4- (vinyloxy) phenyl} propane, and the like.

  As the compound having an epoxy group suitable for the present invention, a compound having two or more epoxy groups is preferable, and a glycidyl ether compound obtained by reaction of a polyhydric alcohol or a polyhydric phenol with epichlorohydrin or a prepolymer thereof. Furthermore, a polymer or copolymer of glycidyl acrylate or glycidyl methacrylate can be used.

  Specific examples include propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether of hydrogenated bisphenol A, hydroquinone diglycidyl. Ether, resorcinol diglycidyl ether, diglycidyl ether or epichlorohydrin polyadduct of bisphenol A, diglycidyl ether or epichlorohydrin polyadduct of bisphenol F, diglycidyl ether or epichlorohydride of halogenated bisphenol A Phosphorus polyadduct, diglycidyl ether of biphenyl type bisphenol or epichlorohydrin polyadduct, novolak tree Etc. glycidyl ethers, furthermore, methyl methacrylate / glycidyl methacrylate copolymer, methacrylic acid ethyl / glycidyl methacrylate copolymer, and the like.

  Commercially available products of the above compounds include, for example, Epicoat 1001 (molecular weight: about 900, epoxy equivalent: 450 to 500), Epicoat 1002 (molecular weight: about 1600, epoxy equivalent: 600 to 700), Epicoat 1004 (about) manufactured by Japan Epoxy Resin Co., Ltd. 1060, epoxy equivalent 875-975), Epicoat 1007 (molecular weight about 2900, epoxy equivalent 2000), Epicoat 1009 (molecular weight about 3750, epoxy equivalent 3000), Epicoat 1010 (molecular weight about 5500, epoxy equivalent 4000), Epicoat 1100L (epoxy equivalent) 4000), Epikote YX31575 (epoxy equivalent 1200), Sumitomo Chemical Co., Ltd. Sumiepoxy ESCN-195XHN, ESCN-195XL, ESCN-195XF, and the like.

  Suitable isocyanate compounds for the present invention include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, xylylene diisocyanate, naphthalene diisocyanate, cyclohexanephenylene diisocyanate, isophorone diisocyanate, Examples include hexamethylene diisocyanate, cyclohexyl diisocyanate, and compounds obtained by blocking these with alcohol or amine.

  Suitable amine compounds for the present invention include ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, propylenediamine, polyethyleneimine and the like.

  Examples of the compound having a hydroxyl group suitable for the present invention include a compound having a terminal methylol group, a polyhydric alcohol such as pentaerythritol, and bisphenol / polyphenols.

  Examples of the compound having a carboxyl group suitable for the present invention include aromatic polyvalent carboxylic acids such as pyromellitic acid, trimellitic acid and phthalic acid, and aliphatic polyvalent carboxylic acids such as adipic acid.

  Suitable acid anhydrides for the present invention include pyromellitic acid anhydride and benzophenone tetracarboxylic acid anhydride.

  As a method for microencapsulating the above compound having a thermoreactive group, a known method can be applied. For example, as a method for producing microcapsules, a method using coacervation as shown in U.S. Pat. Nos. 2,800,547 and 2,800,498, British Patent 990443, U.S. Pat. No. 42-711, interfacial polymerization method, US Pat. No. 3,418,250, US Pat. No. 3,660,304, method of polymer precipitation, US Pat. No. 3,796,669, method using isocyanate polyol wall material, US Pat. US Pat. No. 3,914,511 shows a method using an isocyanate wall material, US Pat. Nos. 4001140, 4087376, and 4089802 use a urea-formaldehyde system or a urea formaldehyde-resorcinol wall forming material A method using a wall material such as melamine-formaldehyde resin and hydroxycellulose, as shown in U.S. Pat. No. 4,025,445, an in situ method by monomer polymerization as shown in JP-B Nos. 36-9163 and 51-9079, British Patent No. 930422, US Pat. No. 3,111,407 And the like, but are not limited thereto, such as the spray drying method found in British Patent Nos. 952807 and 967074.

  A preferable microcapsule wall used in the present invention has a three-dimensional cross-linking and has a property of swelling with a solvent. From such a viewpoint, the wall material of the microcapsule is preferably polyurea, polyurethane, polyester, polycarbonate, polyamide, and a mixture thereof, and particularly preferably polyurea and polyurethane. A compound having a thermally reactive group may be introduced into the microcapsule wall.

  Such microcapsules may be combined with each other by heat or may not be combined. In short, among the microcapsule inclusions, the one that oozes out of the capsule surface or outside the microcapsule at the time of application, or the one that enters the microcapsule wall may cause a chemical reaction by heat. You may react with the added hydrophilic resin or the added low molecular weight compound. Alternatively, two or more types of microcapsules may be reacted with each other by providing functional groups that can thermally react with different functional groups. Therefore, it is preferable for image formation that the microcapsules are fused and united by heat, but it is not essential.

  The amount of the polymer fine particles and microcapsules added to the recording layer is preferably 50% by mass or more, and more preferably 70 to 98% by mass in terms of solid content in any fine particle. Within this range, a good image can be formed and good printing durability can be obtained.

  When the recording layer of the present invention contains microcapsules, a solvent that dissolves the inclusions and swells the wall material can be added to the microcapsule dispersion medium. By such a solvent, diffusion of the encapsulated compound having a thermally reactive group to the outside of the microcapsule is promoted. Such a solvent depends on the microcapsule dispersion medium, the material of the microcapsule wall, the wall thickness, and the inclusion, but can be easily selected from many commercially available solvents. For example, in the case of a water-dispersible microcapsule comprising a crosslinked polyurea or polyurethane wall, alcohols, ethers, acetals, esters, ketones, polyhydric alcohols, amides, amines, fatty acids and the like are preferable.

  Specific compounds include methanol, ethanol, tertiary butanol, n-propanol, tetrahydrofuran, methyl lactate, ethyl lactate, methyl ethyl ketone, propylene glycol monomethyl ether, ethylene glycol diethyl ether, ethylene glycol monomethyl ether, γ-butyl lactone, N, There are N-dimethylformamide, N, N-dimethylacetamide, and the like, but not limited thereto. Two or more of these solvents may be used. A solvent that does not dissolve in the microcapsule dispersion but dissolves when the solvent is mixed can also be used.

  The amount of the solvent added is determined by the combination of materials, but usually 5 to 95% by mass of the coating solution is effective, and a preferable range is 10 to 90% by mass, and a more preferable range is 15 to 85%. % By mass.

  The recording layer of the present invention can contain a binder having on-press developability and alkali developability depending on the type of developability.

  As the binder having on-press developability, a hydrophilic resin can be used to improve on-press developability and film strength of the recording layer itself. As hydrophilic resin, what has hydrophilic groups, such as a hydroxyl group, an amino group, a carboxyl group, a phosphoric acid group, a sulfonic acid group, an amide group, is preferable, for example. In addition, the hydrophilic resin reacts with the heat-reactive group of the lipophilic compound included in the microcapsule and crosslinks to increase the image strength and increase the printing durability. Therefore, the hydrophilic resin is a group that reacts with the heat-reactive group. It is preferable to have. For example, when the lipophilic compound has a vinyloxy group or an epoxy group, the hydrophilic resin preferably has a hydroxyl group, a carboxyl group, a phosphoric acid group, a sulfonic acid group, or the like. Among these, a hydrophilic resin having a hydroxyl group or a carboxyl group is preferable.

  Specific examples of hydrophilic resins include gum arabic, casein, gelatin, starch derivatives, soya gum, hydroxypropylcellulose, methylcellulose, carboxymethylcellulose and its sodium salt, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymers, styrene-malein Acid copolymers, polyacrylic acids and their salts, polymethacrylic acids and their salts, homopolymers and copolymers of hydroxyethyl methacrylate, homopolymers and copolymers of hydroxyethyl acrylate, homopolymers and copolymers of hydroxypropyl methacrylate, hydroxypropyl acrylate Homopolymers and copolymers, hydroxybutyl methacrylate homopolymers and copolymers, Homopolymers and copolymers of butyl acrylate, polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, hydrolyzed polyvinyl acetate having a degree of hydrolysis of at least 60% by weight, preferably at least 80% by weight, polyvinyl formal, polyvinyl pyrrolidone, acrylamide Homopolymers and copolymers, methacrylamide homopolymers and copolymers, N-methylolacrylamide homopolymers and copolymers, 2-acrylamido-2-methyl-1-propanesulfonic acid homopolymers and copolymers, 2-methacryloyloxyethylphosphonic acid And homopolymers and copolymers thereof.

  The amount of the hydrophilic resin added to the recording layer is preferably 20% by mass or less, and more preferably 10% by mass or less.

Further, the hydrophilic resin may be used after being cross-linked to such an extent that an unexposed portion can be developed on-press on a printing press. Cross-linking agents include aldehydes such as glyoxal, melamine formaldehyde resin, urea formaldehyde resin, methylol compounds such as N-methylol urea, N-methylol melamine, and methylolated polyamide resin, divinyl sulfone and bis (β-hydroxyethylsulfonic acid) Active vinyl compounds such as, epoxy compounds such as epichlorohydrin and polyethylene glycol diglycidyl ether, polyamides, polyamines, epichlorohydrin adducts, polyamide epichlorohydrin resins, ester compounds such as monochloroacetic acid esters and thioglycolic acid esters, Polycarboxylic acids such as polyacrylic acid and methyl vinyl ether / maleic acid copolymer, inorganic such as boric acid, titanyl sulfate, Cu, Al, Sn, V, Cr salts Crosslinking agents, such as modified polyamide polyimide resin. In addition, a crosslinking catalyst such as ammonium chloride, a silane coupling agent, a titanate coupling agent, or the like can be used in combination.
As the binder having alkali developability, a linear organic polymer is preferably used, and a linear organic polymer that is soluble or swellable in water or weak alkaline water is selected. Of these, a (meth) acrylic resin having a benzyl group or an allyl group and a carboxy group in the side chain is particularly preferable because of its excellent balance of film strength, sensitivity, and developability.

The recording layer of the present invention contains a photothermal conversion agent having a function of converting light into heat in order to increase sensitivity. Examples of the photothermal conversion agent (infrared absorber) include the following.
<Infrared absorber>
When forming an image of the lithographic printing plate precursor according to the present invention with a laser that emits infrared rays of 760 to 1200 nm using a light source, it is usually essential to use an infrared absorber. The infrared absorber has a function of converting absorbed infrared rays into heat. Due to the heat generated at this time, a polymerization initiator (radical generator) described later is thermally decomposed to generate radicals. The infrared absorber used in the present invention is a dye or pigment having an absorption maximum at a wavelength of 760 to 1200 nm.

  As the dye, commercially available dyes and known dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Is mentioned.

  Examples of preferable dyes include cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-60-78787, JP-A-58-173696, 58-181690, JP-A-58-194595, etc., methine dyes, JP-A-58-112793, JP-A-58-224793, JP-A-59-48187, JP-A-59- No. 73996, JP-A-60-52940, JP-A-60-63744 and the like, Naphthoquinone dyes described in JP-A-58-112792, etc., British Patent 434,875 And cyanine dyes.

  Also, a near infrared absorption sensitizer described in US Pat. No. 5,156,938 is preferably used, and a substituted arylbenzo (thio) pyrylium salt described in US Pat. No. 3,881,924, Trimethine thiapyrylium salts described in JP-A-57-142645 (US Pat. No. 4,327,169), JP-A-58-181051, 58-220143, 59-41363, 59-84248 Nos. 59-84249, 59-146063, 59-146061, pyranlium compounds, cyanine dyes described in JP-A-59-216146, US Pat. No. 4,283,475 The pentamethine thiopyrylium salts described above and the pyrylium compounds disclosed in Japanese Patent Publication Nos. 5-13514 and 5-19702 are also preferably used. . Another example of a preferable dye is a near-infrared absorbing dye described in US Pat. No. 4,756,993 as formulas (I) and (II).

  Other preferable examples of the infrared absorbing dye of the present invention include specific indolenine cyanine dyes described in Japanese Patent Application Nos. 2001-6326 and 2001-237840 as exemplified below.

これらの染料のうち特に好ましいものとしては、シアニン色素、スクワリリウム色素、ピリリウム塩、ニッケルチオレート錯体、インドレニンシアニン色素が挙げられる。さらに、シアニン色素やインドレニンシアニン色素が好ましく、特に好ましい一つの例として下記一般式（ｉ）で示されるシアニン色素が挙げられる。

Among these dyes, cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes are particularly preferable. Further, cyanine dyes and indolenine cyanine dyes are preferred, and one particularly preferred example is a cyanine dye represented by the following general formula (i).

一般式（ｉ）中、Ｘ¹は、水素原子、ハロゲン原子、−ＮＰｈ₂、Ｘ²−Ｌ¹又は以下に示す基を表す。ここで、Ｘ²は酸素原子、窒素原子、又は硫黄原子を示し、Ｌ¹は、炭素原子数１〜１２の炭化水素基、ヘテロ原子を有する芳香族環、ヘテロ原子を含む炭素原子数１〜１２の炭化水素基を示す。なお、ここでヘテロ原子とは、Ｎ、Ｓ、Ｏ、ハロゲン原子、Ｓｅを示す。Ｘ_a ^-は後述するＺ₁ ^-と同様に定義され、Ｒ_aは、水素原子、アルキル基、アリール基、置換又は無置換のアミノ基、ハロゲン原子より選択される置換基を表す。

In formula (i), X ¹ represents a hydrogen atom, a halogen atom, -NPh _2, X ² -L ¹ or a group shown below. Here, X ² represents an oxygen atom, a nitrogen atom, or a sulfur atom, and L ¹ represents a hydrocarbon group having 1 to 12 carbon atoms, an aromatic ring having a hetero atom, or 1 to 1 carbon atom containing a hetero atom. 12 hydrocarbon groups are shown. Here, the hetero atom represents N, S, O, a halogen atom, or Se. X _a ^- is Z ₁ to be described later ^- has the same definition as, R _a represents a hydrogen atom, an alkyl group, an aryl group, a substituted or unsubstituted amino group, substituted or unsubstituted amino group and a halogen atom.

Ｒ¹及びＲ²は、それぞれ独立に、炭素原子数１〜１２の炭化水素基を示す。記録層塗布液の保存安定性から、Ｒ¹及びＲ²は、炭素原子数２個以上の炭化水素基であることが好ましく、更に、Ｒ¹とＲ²とは互いに結合し、５員環又は６員環を形成していることが特に好ましい。

R ¹ and R ² each independently represents a hydrocarbon group having 1 to 12 carbon atoms. From the storage stability of the recording layer coating solution, R ¹ and R ² are preferably hydrocarbon groups having 2 or more carbon atoms, and R ¹ and R ² are bonded to each other to form a 5-membered ring or It is particularly preferable that a 6-membered ring is formed.

Ar ¹ and Ar ² may be the same or different and each represents an aromatic hydrocarbon group which may have a substituent. Preferred aromatic hydrocarbon groups include a benzene ring and a naphthalene ring. Moreover, as a preferable substituent, a C12 or less hydrocarbon group, a halogen atom, and a C12 or less alkoxy group are mentioned. Y ¹ and Y ² may be the same or different and each represents a sulfur atom or a dialkylmethylene group having 12 or less carbon atoms. R ³ and R ⁴ may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferred substituents include alkoxy groups having 12 or less carbon atoms, carboxyl groups, and sulfo groups. R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 12 or less carbon atoms. From the availability of raw materials, a hydrogen atom is preferred. Z _a ^- represents a counter anion. However, when the cyanine dye represented by formula (i) has an anionic substituent in the structure thereof, Z _a is does not require charge neutralization ^- is not necessary. Preferred Z _a ⁻ is a halogen ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ion, particularly preferably a perchlorate ion, in view of storage stability of the recording layer coating solution. Hexafluorophosphate ions and aryl sulfonate ions.

  Specific examples of cyanine dyes represented by formula (i) that can be suitably used in the present invention include those described in paragraph numbers [0017] to [0019] of JP-A No. 2001-133969. Can do.

  Further, other particularly preferable examples include specific indolenine cyanine dyes described in Japanese Patent Application Nos. 2001-6326 and 2001-237840 described above.

  Examples of the pigment used in the present invention include commercially available pigments and color index (CI) manual, “Latest Pigment Handbook” (edited by Japan Pigment Technology Association, published in 1977), “Latest Pigment Application Technology” (CMC Publishing, 1986), “Printing Ink Technology”, CMC Publishing, 1984) can be used.

  Examples of the pigment include black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and other polymer-bonded dyes. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments In addition, quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like can be used. Among these pigments, carbon black is preferable.

  These pigments may be used without surface treatment, or may be used after surface treatment. The surface treatment method includes a method of surface coating with a resin or wax, a method of attaching a surfactant, a method of bonding a reactive substance (eg, silane coupling agent, epoxy compound, polyisocyanate, etc.) to the pigment surface, etc. Can be considered. The above-mentioned surface treatment methods are described in “Characteristics and Applications of Metal Soap” (Shobobo), “Printing Ink Technology” (CMC Publishing, 1984) and “Latest Pigment Application Technology” (CMC Publishing, 1986). Yes.

  The particle size of the pigment is preferably in the range of 0.01 μm to 10 μm, more preferably in the range of 0.05 μm to 1 μm, and particularly preferably in the range of 0.1 μm to 1 μm. Within this range, good stability of the pigment dispersion in the image recording layer coating solution and good uniformity of the image recording layer can be obtained.

  As a method for dispersing the pigment, a known dispersion technique used in ink production, toner production, or the like can be used. Examples of the disperser include an ultrasonic disperser, a sand mill, an attritor, a pearl mill, a super mill, a ball mill, an impeller, a disperser, a KD mill, a colloid mill, a dynatron, a three-roll mill, and a pressure kneader. Details are described in "Latest Pigment Applied Technology" (CMC Publishing, 1986).

  These infrared absorbers may be added to the same layer as other components, or may be added to another layer provided, but when a negative planographic printing plate precursor is prepared, image recording is performed. The layer is added so that the absorbance at the maximum absorption wavelength in the wavelength range of 760 nm to 1200 nm is in the range of 0.3 to 1.2 by the reflection measurement method. Preferably, it is the range of 0.4-1.1. Within this range, a uniform polymerization reaction proceeds in the depth direction of the image recording layer, and good film strength of the image area and adhesion to the support can be obtained.

  The absorbance of the image recording layer can be adjusted by the amount of infrared absorber added to the image recording layer and the thickness of the image recording layer. Absorbance can be measured by a conventional method. As a measuring method, for example, on a reflective support such as aluminum, an image recording layer having a thickness appropriately determined in a range in which the coating amount after drying is necessary as a lithographic printing plate is formed, and the reflection density is set to the optical density. And a method of measuring with a spectrophotometer by a reflection method using an integrating sphere.

一般に、染料は、光熱変換効率は高いが光で退色しやすく、顔料は光熱変換率が染料ほど高くないが、光で退色しにくいという性質を有している。

In general, a dye has a high photothermal conversion efficiency but is easily faded by light, and a pigment has a property that the photothermal conversion is not as high as that of a dye, but is difficult to fade by light.

  In the present invention, the recording layer is divided into an upper layer and a lower layer, and the ratio of the thickness of the upper layer and the lower layer is preferably 2 to 1, and the lower layer contains a dye that is a material having high photothermal conversion efficiency. In addition, the upper layer contains a pigment that has a relatively low photothermal conversion efficiency compared to the dye and is less likely to photobleach.

  As a result, the temperature is increased while absorbing light entirely in the upper layer portion that is difficult to photobleach, and the lower layer portion is heated at once with the light that has passed through the upper layer and attenuated, so that the interface temperature between the recording layer and the support Can be raised efficiently. By increasing the temperature of the interface portion, the recording layer in the interface region can be firmly solidified, and printing durability and sensitivity can be improved.

  The recording layer of the present invention may contain a reaction accelerator that initiates or accelerates the reaction of the thermally reactive group. Further, since the reaction accelerator generates an acid or a radical, it can form a print-out system in combination with a dye that changes color with the generated acid or radical. Suitable examples of the reaction accelerator include known acid precursors, acid generators, and compounds called thermal radical generators. For example, a photoinitiator for photocationic polymerization, a photoinitiator for radical photopolymerization, an acid generator for printout image formation, an acid generator used for microresist, and the like.

  More specifically, organic halogen compounds typified by trihalomethyl-substituted heterocyclic compounds described in JP-A-2002-29162, JP-A-2002-46361, JP-A-2002-137562, etc., iminosulfonates, etc. And compounds capable of generating a sulfonic acid by photolysis represented by (2), disulfone compounds, onium salts (for example, iodonium salts, diazonium salts, sulfonium salts, etc.). Moreover, the compound which introduce | transduced the group or compound which generate | occur | produces these acids or radicals into the principal chain or side chain of a polymer can also be used. Although the example of a compound is given to the following, it is not limited to these.

上記反応促進剤は２種以上を組み合わせて用いることもできる。また、反応促進剤の記録層への添加は、記録層塗布液への直接添加でも、ポリマー微粒子やマイクロカプセル中に含有させた形での添加でもよい。記録層中の反応促進剤の含有量は、記録層全固形分の０．０１〜２０質量％が好ましく、より好ましくは０．１〜１０質量％である。この範囲内で、機上現像性を損なわず、良好な反応開始又は促進効果が得られる。

Two or more kinds of the reaction accelerators can be used in combination. The reaction accelerator may be added directly to the recording layer coating solution or may be added in the form of polymer fine particles or microcapsules. The content of the reaction accelerator in the recording layer is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, based on the total solid content of the recording layer. Within this range, good reaction initiation or acceleration effect can be obtained without impairing on-press developability.

  In the recording layer of the present invention, a compound that is discolored by an acid or a radical can be added in order to generate a printout image. As such a compound, various dyes such as diphenylmethane, triphenylmethane, thiazine, oxazine, xanthene, anthraquinone, iminoquinone, azo, and azomethine are effectively used.

  Specific examples include brilliant green, ethyl violet, methyl green, crystal violet, basic fuchsin, methyl violet 2B, quinaldine red, rose bengal, methanyl yellow, thymol sulfophthalein, xylenol blue, methyl orange, paramethyl red, Congo Fred, Benzopurpurin 4B, α-Naphthyl Red, Nile Blue 2B, Nile Blue A, Methyl Violet, Malachide Green, Parafuchsin, Victoria Pure Blue BOH [manufactured by Hodogaya Chemical Co., Ltd.], Oil Blue # 603 [Orient Chemical Kogyo Co., Ltd.], Oil Pink # 312 [Orient Chemical Co., Ltd.], Oil Red 5B [Orient Chemical Co., Ltd.], Oil Scarlet # 308 [Orient Gaku Kogyo Co., Ltd.], Oil Red OG [Orient Chemical Co., Ltd.], Oil Red RR [Orient Chemical Co., Ltd.], Oil Green # 502 [Orient Chemical Co., Ltd.], Spiron Red BEH Special [made by Hodogaya Chemical Co., Ltd.], m-cresol purple, cresol red, rhodamine B, rhodamine 6G, sulforhodamine B, auramine, 4-p-diethylaminophenyliminonaphthoquinone, 2-carboxyanilino-4-p- Diethylaminophenyliminonaphthoquinone, 2-carboxystearylamino-4-pN, N-bis (hydroxyethyl) amino-phenyliminonaphthoquinone, 1-phenyl-3-methyl-4-p-diethylaminophenylimino-5-pyrazolone, 1-β-naphthyl-4- - dyes and p of diethylamino phenyl imino-5-pyrazolone, p ', p "- hexamethyl triamnotriphenylmethane (leuco crystal violet), and a leuco dye such as Pergascript Blue SRB (manufactured by Ciba-Geigy).

  In addition to the above, a leuco dye known as a material for thermal paper or pressure-sensitive paper is also suitable. Specific examples include crystal violet lactone, malachite green lactone, benzoylleucomethylene blue, 2- (N-phenyl-N-methylamino) -6- (Np-tolyl-N-ethyl) amino-fluorane, 2-anilino. -3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3,6-dimethoxyfluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) ) -Fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -6-methyl-7-anilinofluorane, 3 -(N, N-diethylamino) -6-methyl-7-xylidinofluorane, 3- (N, N-diethylamino) -6-methyl-7-chloro Fluorane, 3- (N, N-diethylamino) -6-methoxy-7-aminofluorane, 3- (N, N-diethylamino) -7- (4-chloroanilino) fluorane, 3- (N, N-diethylamino) -7-chlorofluorane, 3- (N, N-diethylamino) -7-benzylaminofluorane, 3- (N, N-diethylamino) -7,8-benzofluorane, 3- (N, N-dibutyl) Amino) -6-methyl-7-anilinofluorane, 3- (N, N-dibutylamino) -6-methyl-7-xylidinofluorane, 3-piperidino-6-methyl-7-anilinofluorane 3-pyrrolidino-6-methyl-7-anilinofluorane, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-n-butyl- -Methylindol-3-yl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl- 2-methylindol-3-yl) -4-zaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, and the like.

  A suitable addition amount of the dye that changes color by an acid or a radical is 0.01 to 10% by mass with respect to the solid content of the recording layer.

  In addition to the above, various compounds may be added to the recording layer of the present invention as necessary. For example, a polyfunctional monomer can be added to the recording layer matrix in order to further improve the printing durability. As this polyfunctional monomer, those exemplified as the monomer put in the microcapsule can be used. Among them, preferable monomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, and the like.

  In the present invention, it is desirable to add a small amount of a thermal polymerization inhibitor in order to prevent unnecessary thermal polymerization of the ethylenically unsaturated compound during the preparation or storage of the recording layer coating solution. Suitable thermal polymerization inhibitors include hydroquinone, 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-nitroso-N-phenylhydroxylamine aluminum salt and the like. The addition amount of the thermal polymerization inhibitor is preferably 0.01 to 5% by mass with respect to the weight of the total composition.

  If necessary, higher fatty acids such as behenic acid and behenic acid amide or derivatives thereof are added to prevent polymerization inhibition by oxygen, and are unevenly distributed on the surface of the recording layer during the drying process after coating. Also good. The amount of the higher fatty acid or derivative thereof added is preferably 0.1 to about 10% by mass of the solid content of the recording layer.

  In addition, inorganic fine particles may be added to the first recording layer of the present invention. Examples of suitable inorganic fine particles include silica, alumina, magnesium oxide, titanium oxide, magnesium carbonate, calcium alginate, or a mixture thereof. Even if they are not photothermally convertible, they can be used for strengthening the film and enhancing interfacial adhesion by surface roughening.

  The average particle size of the inorganic fine particles is preferably 5 nm to 10 μm, more preferably 10 nm to 1 μm. Within this range, the resin fine particles and the photothermal conversion agent metal fine particles are both stably dispersed in the hydrophilic resin, the film strength of the recording layer is sufficiently maintained, and the non-hydrophilic material having excellent hydrophilicity that hardly causes printing stains. An image portion can be formed.

  Such inorganic fine particles can be easily obtained as a commercial product such as a colloidal silica dispersion. The content of the inorganic fine particles in the recording layer is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total solid content of the recording layer.

  In the recording layer of the present invention, in order to improve the dispersion stability of the recording layer, the plate making and printing performance, and the coating property, JP-A-2-195356, JP-A-59-121044, JP-A-4-13149. And nonionic, anionic, cationic, amphoteric or fluorine surfactants described in Japanese Patent Application No. 2001-169931. A suitable addition amount of these surfactants is 0.005 to 1% by mass of the total solids of the recording layer.

  Furthermore, a plasticizer can be added to the recording layer of the present invention as needed in order to impart flexibility of the coating film. For example, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate and the like are used.

  The recording layer of the present invention is coated by preparing a coating solution by dissolving the necessary components described above in a solvent. Solvents used here include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxy Examples include ethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyllactone, toluene, water, and the like. However, the present invention is not limited to this. These solvents are used alone or in combination. The solid content concentration of the coating solution is preferably 1 to 50% by mass.

Coating, the underlying coating amount of the recording layer obtained after drying (solid content) is preferably from ^{0.1~1.5g / m 2, 0.3~0.7g / m} 2 is more preferable. Further, the upper layer of the coating amount of the recording layer is preferably ^{0.3~3.0g / m 2, 0.6~1.4g / m} 2 is more preferable. The ratio of the coating amount of the upper layer and the lower layer of the recording layer is preferably 2 to 1, and the combined coating amount of the upper layer and the lower layer of the recording layer is preferably 0.4 to 4.5 g / m ² , 0.9 ˜2.1 g / m ² is more preferred. When the coating amount is less than this range, the apparent sensitivity increases, but the film characteristics of the recording layer that performs the function of image recording deteriorate. When the coating amount is larger than this range, image formation at the substrate interface becomes insufficient. Various methods can be used as a coating method. Examples thereof include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.

  The lithographic printing plate precursor according to the present invention is provided on the recording layer in order to protect the hydrophilic recording layer surface from contamination with lipophilic substances during storage and fingerprint trace contamination due to finger contact during handling. An overcoat layer containing a water-soluble resin described in JP-A-162961 and JP-A-2002-19318 can be provided.

  Specific examples of water-soluble resins used in the overcoat layer include natural gums such as gum arabic, water-soluble soybean polysaccharide, fiber derivatives (eg, carboxymethyl cellulose, carboxyethyl cellulose, methyl cellulose, etc.), modified products thereof, For synthetic polymers such as white dextrin, pullulan, and enzymatically degraded etherified dextrin, polyvinyl alcohol (polyvinyl acetate having a hydrolysis rate of 65% or more), polyacrylic acid, its alkali metal salt or amine salt, and polyacrylic acid Polymer, alkali metal salt or amine salt thereof, polymethacrylic acid, alkali metal salt or amine salt thereof, vinyl alcohol / acrylic acid copolymer and alkali metal salt or amine salt thereof, polyacrylamide, copolymer thereof, polyhydroxy Ethyl acrylate, Polyvinyl Lupyrrolidone, its copolymer, polyvinyl methyl ether, vinyl methyl ether / maleic anhydride copolymer, poly-2-acrylamido-2-methyl-1-propanesulfonic acid, its alkali metal salt or amine salt, poly-2 -Acrylamido-2-methyl-1-propanesulfonic acid copolymer, its alkali metal salt or amine salt. Depending on the purpose, two or more of these resins may be mixed and used. However, the present invention is not limited to these examples.

  The overcoat layer may contain a photothermal conversion agent in order to improve sensitivity. A preferable photothermal conversion agent includes a water-soluble infrared absorbing dye. For example, (IR-1) to (IR-11) shown in the description of the recording layer are preferably used.

  In addition, a nonionic surfactant can be mainly added to the overcoat layer in the case of aqueous solution coating for the purpose of ensuring the uniformity of coating. Specific examples of such nonionic surfactants include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecyl ether and the like. . The proportion of the nonionic surfactant in the overcoat layer in the total solid is preferably 0.05 to 5 mass%, more preferably 1 to 3 mass%.

  Furthermore, the overcoat layer can contain a compound having any one of fluorine atoms and silicon atoms described in JP-A No. 2001-341448 in order to prevent sticking between plates during stacking and storage.

  The thickness of the overcoat layer of the present invention is preferably 0.1 to 4.0 μm, and more preferably 0.1 to 1.0 μm. Within this range, it is possible to prevent the recording layer from being contaminated by an oleophilic substance without impairing the removability of the overcoat layer on the printing press.

  In the lithographic printing plate precursor according to the present invention, the support on which the recording layer can be applied is a dimensionally stable plate-like material, for example, paper, plastic (for example, polyethylene, polypropylene, polystyrene, etc.) is laminated. Paper, metal plates (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 on which a metal as described above is laminated or vapor-deposited. A preferable support includes a polyester film or an aluminum plate.

  The aluminum plate is a pure aluminum plate and an alloy plate containing aluminum as a main component and containing a trace amount of different elements. Further, a plastic is laminated on a thin film of aluminum or an aluminum alloy. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is at most 10% by mass. Further, it may be an aluminum plate from an aluminum ingot using a DC casting method or an aluminum plate from an ingot by a continuous casting method. However, as the aluminum plate applied to the present invention, conventionally known and publicly available aluminum plates can be used as appropriate.

  The thickness of the substrate used in the present invention is 0.05 mm to 0.6 mm, preferably 0.1 mm to 0.4 mm, and particularly preferably 0.15 mm to 0.3 mm.

  Prior to using the aluminum plate, it is preferable to perform a surface treatment such as roughening the surface or anodizing. By the surface treatment, it is easy to improve hydrophilicity and secure adhesion to the recording layer.

  The surface of the aluminum plate is roughened by various methods. For example, a method of mechanically roughening, a method of electrochemically dissolving and roughening the surface, and a method of selectively dissolving the surface chemically. By the method. As the mechanical method, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, or a buff polishing method can be used. As a chemical method, a method of immersing in a saturated aqueous solution of an aluminum salt of a mineral acid as described in JP-A No. 54-31187 is suitable. In addition, as an electrochemical surface roughening method, there is a method of performing alternating current or direct current in an electrolytic solution containing an acid such as hydrochloric acid or nitric acid. Further, as disclosed in JP-A-54-63902, an electrolytic surface roughening method using a mixed acid can also be used. The roughening by the method as described above is preferably performed in such a range that the center line average roughness (Ra) of the surface of the aluminum plate is 0.2 to 1.0 μm.

  The roughened aluminum plate is subjected to alkali etching treatment using an aqueous solution of potassium hydroxide or sodium hydroxide as necessary, and further neutralized, and then anodized to increase wear resistance as desired. Processing is performed.

As the electrolyte used for the anodizing treatment of the aluminum plate, various electrolytes that form a porous oxide film can be used. In general, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid, or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte. The treatment conditions for anodization vary depending on the electrolyte used, and thus cannot be specified in general. However, in general, the electrolyte concentration is 1 to 80% by mass solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 to 60 A / day. dm ² , voltage 1 to 100 V, and electrolysis time 10 seconds to 5 minutes are suitable. The amount of the oxide film to be formed is preferably 1.0 to 5.0 g / m ² , particularly 1.5 to 4.0 g / m ² .

  As the support used in the present invention, the substrate having the above-mentioned surface treatment and having an anodized film may be used as it is, but for further improvement in adhesion to the upper layer, hydrophilicity, resistance to contamination, heat insulation and the like. If necessary, an aqueous solution containing an anodized film micropore enlargement treatment, micropore sealing treatment, and a hydrophilic compound described in JP-A Nos. 2001-253181 and 2001-322365 The surface hydrophilization treatment to be immersed can be appropriately selected and performed.

  Suitable hydrophilic compounds for the hydrophilization treatment include polyvinylphosphonic acid, sulfonic acid group-containing compounds, saccharide compounds, citric acid, alkali metal silicates, potassium zirconium fluoride, phosphate / inorganic fluorine compounds, and the like. Can be mentioned.

  When using a support with insufficient surface hydrophilicity such as a polyester film as the support of the present invention, it is desirable to apply a hydrophilic layer to make the surface hydrophilic. As the hydrophilic layer, at least one element selected from beryllium, magnesium, aluminum, silicon, titanium, boron, germanium, tin, zirconium, iron, vanadium, antimony and transition metal described in JP-A-2001-199175 is used. A hydrophilic layer formed by applying a coating solution containing an oxide or hydroxide colloid is preferred. Among these, a hydrophilic layer formed by applying a coating solution containing a silicon oxide or hydroxide colloid is preferable.

In the present invention, before applying the recording layer, an inorganic undercoat layer such as a water-soluble metal salt such as zinc borate described in JP-A No. 2001-322365 or, for example, carboxymethylcellulose, if necessary. An organic subbing layer containing dextrin, polyacrylic acid or the like can be provided. The undercoat layer can contain the infrared absorbing dye.
[Plate making and printing]
The lithographic printing plate precursor of the present invention is image-formed by heat. Specifically, direct image-like recording by a thermal recording head or the like, scanning exposure by an infrared laser, high-illuminance flash exposure such as a xenon discharge lamp, infrared lamp exposure, or the like is used, but a semiconductor that emits infrared light having a wavelength of 700 to 1200 nm. Exposure with a solid high-power infrared laser such as a laser or YAG laser is preferred.

  The lithographic printing plate precursor of the present invention that has been image-exposed can be mounted on a printing machine without further processing and printed in the usual procedure using ink and fountain solution. In addition, as described in Japanese Patent No. 2938398, these lithographic printing plate precursors are mounted on a printing machine cylinder, exposed by a laser mounted on the printing machine, and then dampened with water. It is also possible to perform on-press development with ink applied. Further, these lithographic printing plate precursors can be used for printing after developing with water or a suitable aqueous solution as a developer.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
[Example of support production]
Purify the molten metal of JIS A1050 alloy containing 99.5 mass% or more of aluminum and Fe 0.30 mass%, Si 0.10 mass%, Ti 0.02 mass%, Cu 0.013 mass%, Casted. In the cleaning process, a degassing process was performed to remove unnecessary gases such as hydrogen in the molten metal, and a ceramic tube filter process was performed. The casting method was a DC casting method. The solidified 500 mm thick ingot was chamfered 10 mm from the surface and homogenized at 550 ° C. for 10 hours so as not to coarsen the intermetallic compound. Next, after hot rolling at 400 ° C. and intermediate annealing at 500 ° C. for 60 seconds in a continuous annealing furnace, cold rolling was performed to obtain an aluminum rolled plate having a plate pressure of 0.30 mm. By controlling the roughness of the rolling roll, the centerline average surface roughness Ra after cold rolling was controlled to 0.2 μm. Then, it applied to the tension leveler in order to improve planarity.

Next, the surface treatment for making a lithographic printing plate support was performed. First, in order to remove the rolling oil on the surface of the aluminum plate, degreasing treatment was carried out with a 10% by mass sodium aluminate aqueous solution at 50 ° C. for 30 seconds, and neutralization and smut removal treatment were carried out with a 30% by mass sulfuric acid aqueous solution at 50 ° C. for 30 seconds. Next, in order to improve the adhesion between the support and the recording layer and to provide water retention to the non-image area, a so-called graining treatment was performed to roughen the surface of the support. An aqueous solution containing 1% by mass of nitric acid and 0.5% by mass of aluminum nitrate is kept at 45 ° C., and an aluminum web is allowed to flow in the aqueous solution, while an indirect power feeding cell has a current density of 20 A / dm ² and a duty ratio of 1: 1. Electrolytic graining was performed by applying an anode side electric quantity of 240 C / dm ² in an alternating waveform. Thereafter, an etching treatment was performed with a 10% by mass aqueous sodium aluminate solution at 50 ° C. for 30 seconds, and a 30% by mass sulfuric acid aqueous solution was subjected to neutralization and smut removal treatment at 50 ° C. for 30 seconds. Furthermore, in order to improve wear resistance, chemical resistance and water retention, an oxide film was formed on the support by anodic oxidation. An anodization of 2.5 g / m ² by using a 20% by weight sulfuric acid aqueous solution as an electrolyte at 35 ° C. and carrying out an aluminum web through the electrolyte and performing an electrolytic treatment at a direct current of 14 A / dm ² by an indirect power supply cell. A film was created.

Thereafter, a silicate treatment was performed in order to ensure hydrophilicity as a non-image portion of the printing plate. The treatment was carried in such a way that a No. 3 sodium silicate 1.5 mass% aqueous solution was kept at 70 ° C. so that the contact time of the aluminum web was 15 seconds and further washed with water. The adhesion amount of Si was 10 mg / m ² . The center line surface roughness Ra of the support produced as described above was 0.25 μm.
[Example of recording layer upper and lower layers]
[Lower layer formation]
[Synthesis example of type a]
As an oil phase component, 6.0 g of bis (vinyloxyethyl) ether of bisphenol A, an adduct of trimethylolpropane and xylylene diisocyanate (Takenate D-110N manufactured by Mitsui Takeda Chemical Co., Ltd., microcapsule wall material) 6 0.9 g, 2.1 g of the following infrared absorbing dye (1), and 0.1 g of Pionein A41C were dissolved in 17.7 g of ethyl acetate. As an aqueous phase component, 37.5 g of a 4 mass% aqueous solution of PVA205 (Kuraray polyvinyl alcohol) was prepared. The oil phase component and the aqueous phase component were emulsified for 10 minutes under the condition of 12000 rpm using a homogenizer. Thereafter, 24.5 g of water was added, and the mixture was further stirred at 40 ° C. for 3 hours while cooling with water.

［タイプｂ〜ｅの合成例］
油相成分のビスフェノールＡのビス（ビニルオキシエチル）エーテルおよび赤外線吸収色素（１）の添加量を表１のように変更した以外は、タイプａと同様にタイプｂ〜ｅを合成した。

[Synthesis examples of types b to e]
Types b to e were synthesized in the same manner as type a except that the addition amounts of bis (vinyloxyethyl) ether of bisphenol A and the infrared absorbing dye (1) as oil phase components were changed as shown in Table 1.

上記製造例で得たアルミニウム基板上に、合成例のタイプａ〜ｄの成分を含有する感熱層塗布液を各々調製した後、塗布量０．３３ｇ／ｍ²になるようバー塗布し、７０℃９０秒でオーブン乾燥することにより、第一の感熱層を得る。
タイプｅは塗布量１．０ｇ／ｍ²になるようバー塗布し、同様の乾燥を行って感熱層を得る。

感熱層塗布液
合成例で得たマイクロカプセル（固形分換算） ９．０ｇ
酸前駆体（下記の酸前駆体（１）） ０．２４ｇ
水 ３５．４ｇ

On the aluminum substrate obtained in the above production example, each heat-sensitive layer coating solution containing the components of types a to d in the synthesis example was prepared, and then applied to a bar so that the coating amount became 0.33 g / m ^2. The first thermosensitive layer is obtained by oven drying in 90 seconds.
For type e, a bar is applied so that the application amount is 1.0 g / m ^2, and the same drying is performed to obtain a heat-sensitive layer.

Microcapsules (solid content conversion) 9.0g obtained in the heat-sensitive layer coating liquid synthesis example
0.24 g of acid precursor (the following acid precursor (1))
35.4 g of water

［タイプａ〜ｄの上層の形成］
下記の混合液を各々、ガラスビーズとともにペイントシェーカーにて３０分間攪拌しカーボンブラックを分散させ、ガラスビーズを濾別した後、フッ素系界面活性剤メガファックＦ１７７（大日本インキ化学工業(株)製）を０．００５ｇ添加、攪拌し、上層塗布液a〜dを作成した。

[Formation of upper layers of types a to d]
Each of the following mixed liquids was stirred with a glass shaker for 30 minutes in a paint shaker to disperse the carbon black, and the glass beads were separated by filtration. Then, the fluorosurfactant Megafac F177 (manufactured by Dainippon Ink & Chemicals, Inc.) ) Was added and stirred to prepare upper layer coating liquids a to d.

This coating solution was applied onto the lower layer so as to have a dry coating amount of 0.67 g / m ² and dried by heating (80 ° C., 2 minutes) to form an upper layer.
(Upper layer coating solution)
・ 35% methyl ethyl ketone solution of polyurethane resin Table 2 listed (Nipporan, Nipponran 2304)
Carbon black listed in Table 2 (Mitsubishi Chemical Corporation, MA600)
・ Dispersant (Solsperse S24000R, ICI) 0.2g
-Bisphenol A bis (vinyloxyethyl) ether 3.0 g
・ Diphenyliodonium trifluoromethanesulfonate 1.0g
・ Propylene glycol monomethyl ether 40g
・ Methyl ethyl ketone 60g

It is explanatory drawing which illustrates the state distributed so that the light absorption coefficient in the image recording layer of the lithographic printing plate concerning embodiment of this invention may change continuously. It is explanatory drawing which illustrates the state distributed so that the light absorption coefficient in the image recording layer of the lithographic printing plate concerning embodiment of this invention may change in two steps. It is explanatory drawing which illustrates distribution of light absorption energy when the lithographic printing plate which concerns on embodiment of this invention is exposed with a laser beam. It is a table | surface which shows the setting value of the light energy amount absorbed in the area | region of the upper part of the lithographic printing plate which concerns on embodiment of this invention, and an intermediate | middle part, and a lower part in a comparative example. It is explanatory drawing which shows temperature distribution when it exposes with the laser beam corresponding to the model of the longitudinal section in the lithographic printing plate which concerns on embodiment of this invention. (A) is a diagram showing a temperature distribution when a conventional lithographic printing plate is exposed with a laser beam, and (B) is a schematic configuration diagram showing an enlarged longitudinal section of a main part in the conventional lithographic printing plate. (C) is a schematic block diagram which shows a state when the conventional lithographic printing plate is developed.

Explanation of symbols

10 Planographic printing plate 12 Aluminum support 14 Anodized film 16 Image recording layer

Claims (4)

It has an image recording layer containing a polymerizable compound and a compound that generates a polymerization initiator on a support, and an upper layer of the image recording layer contains a pigment that absorbs image recording light, and is a lower layer of the image recording layer A lithographic printing plate precursor comprising a dye that absorbs image recording light. 2. The lithographic printing plate precursor as claimed in claim 1, wherein the dye contained in the lower layer of the image recording layer is encapsulated in a microcapsule. Assuming a model in which the image recording layer is divided into an upper part, a middle part, and a lower part, which are three thin-layered areas having a uniform thickness in the depth direction from the surface, absorption is assumed in the assumed lower layer. The image recording layer is configured by distributing the light absorption coefficient from the surface in the depth direction so that the amount of light energy to be absorbed is equal to or greater than the amount of light energy absorbed by the upper part and the middle part. The lithographic printing plate precursor as claimed in claim 1 or 2, wherein: The image recording layer distributes the light absorption coefficient from the surface to the depth direction so that the light absorption coefficient becomes the highest in the assumed lower layer, which is in the vicinity of the interface with the support. The lithographic printing plate precursor as claimed in claim 1 or 2, wherein the lithographic printing plate precursor is configured as described above.

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