JP2006243464A - Lithographic printing plate material and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic printing plate material excellent in storage stability at high humidity, and also to provide an image forming method using the same. <P>SOLUTION: The lithographic printing plate material has, on an aluminum support: a photosensitive layer containing an acid generator composition to generate an acid upon irradiation with violet laser light; a compound having at least one acid decomposable bond; and an alkali-soluble polymeric binder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithographic printing plate material used in a computer-to-plate system (CTP) and an image forming method using the same.

  In recent years, CTP recording digital image data directly on a photosensitive printing plate with a laser light source has been developed and is being put to practical use in the technology for producing printing plates for offset printing.

  Among these, in the field of printing that requires relatively high printing durability, it is necessary to use a printing plate material having a negative photosensitive layer having an image recording layer containing a polymerizable compound on an aluminum support. Are known.

  On the other hand, as a photosensitive lithographic printing plate material for CTP for recording digital data with a laser, for example, it contains titanocene which is a polymerization initiator described in JP-A-9-80750 and JP-A-10-101719 and a specific dye. Those having a photopolymerization type photosensitive layer are known.

  In recent years, CTP using a violet laser beam that is available at a low cost is known (see, for example, Patent Document 1). The lithographic printing plate material described in Patent Document 1 uses a radical polymerization system for high sensitivity, and it is necessary to provide an oxygen blocking layer. This increases the cost during production, and this oxygen blocking layer during development processing. Therefore, an extra pre-wash process is required to remove the film, and a single layer is desired for cost reduction.

  On the other hand, single-layer image-forming materials containing a compound capable of generating an acid upon irradiation with actinic light and a compound having at least one bond that can be decomposed by an acid are known. (For example, refer to Patent Documents 2 and 3).

The above-described technique still has insufficient sensitivity, and the raw plate has poor storability at high humidity, and there is a problem that reproduction of the shadow portion deteriorates. Therefore, there has been a demand for a single-layer CTP printing plate having high sensitivity and good reproduction of the shadow portion when the raw plate is stored at high humidity.
JP 2000-35673 A Japanese Patent Laid-Open No. 9-171254 Japanese Patent Laid-Open No. 11-2894

  An object of the present invention is to provide a lithographic printing plate material excellent in storage stability at high humidity and an image forming method using the same.

  The object of the present invention is achieved by the following constitution.

(Claim 1)
It has an acid generator composition capable of generating an acid upon irradiation with a violet laser beam on an aluminum support, a compound having at least one bond that can be decomposed by an acid, and a photosensitive layer containing an alkali-soluble polymer binder. A planographic printing plate material.

(Claim 2)
2. The lithographic printing plate according to claim 1, wherein the acid generator composition capable of generating an acid upon irradiation with the violet laser beam is a dye having an absorption maximum between 350 and 440 nm and an iron arene complex compound. material.

(Claim 3)
The acid generator composition capable of generating an acid upon irradiation with the violet laser beam contains a dye having an absorption maximum between 350 nm and 440 nm and at least one halogen compound represented by the following general formula (I): 2. The lithographic printing plate material according to claim 1, wherein

Formula (I) R ¹ —CY ₂ — (C═O) —R ²
(Wherein R ¹ represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an acyl group, an alkylsulfonyl group, an arylsulfonyl group or a cyano group. R ² represents a monovalent substituent. R ¹ and R ² may be bonded to form a ring, and Y ₂ represents a halogen atom.)
(Claim 4)
The lithographic printing plate material according to claim 3, wherein the at least one halogen compound represented by the general formula (I) is represented by the following general formula (II).

Formula (II) CY ₃ — (C═O) —X—R ³
(In the formula, R ³ represents a monovalent substituent. X represents —O— or —NR ⁴ —. R ⁴ represents a hydrogen atom or an alkyl group. R ³ and R ⁴ are bonded to form a ring. (Y ₃ represents a halogen atom.)
(Claim 5)
Compound having at least one bond capable of being decomposed by the acid _{- (CH 2 CH 2 O)} n - group (n is an integer of 2 to 5) according to claim 1, characterized in that a compound having a 5. The lithographic printing plate material according to any one of 4 above.

(Claim 6)
The _{- (CH 2 CH 2 O)} n - group (n is an integer of 2 to 5) according to claim 5, the compound having the is characterized in that a compound represented by the following general formula (1) Lithographic printing plate material.

(In the formula, R, R ₁ and R ₂ each represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a sulfo group, a carboxyl group or a hydroxyl group. P, q And r each represents an integer of 1 to 3, and m and n each represents an integer of 1 to 5.)
(Claim 7)
The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (2).

Wherein R ^{1 to} R ⁶ are each a hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, heterocyclic group, alkoxy group, cycloalkoxy group, aryloxy group, alkylthio group Group, cycloalkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, acyl group, acyloxy group, amide group, carbamoyl group, ureido group, sulfinyl group, alkylsulfonyl group, arylsulfonyl group, amino group, Represents a halogen atom, a cyano group, a nitro group or a hydroxyl group, and these substituents may be further substituted with the above-mentioned substituents, and a plurality of these substituents are bonded to each other to form a ring. May be.)
(Claim 8)
The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (3).

(In the formula, R ^{1 to} R ³ each independently represents a hydrogen atom or a substituent, and at least R ¹ and R ² , or R ² and R ³ are linked to form a ring.)
(Claim 9)
The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (4).

(In the formula, A represents an S atom or NR ₁ , R ₁ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and Y represents a base of the dye in combination with the adjacent A and carbon atoms. X ₁ and X ₂ each independently represent a monovalent nonmetallic atomic group, and X ₁ and X ₂ may be bonded to each other to form an acidic nucleus of a dye. Good.)
(Claim 10)
The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (5).

Wherein R ¹ represents an alkyl group, aryl group, alkenyl group, cycloalkyl group, aralkyl group or heterocyclic group. R ² represents a hydrogen atom, alkyl group, aryl group, alkenyl group, cycloalkyl group or aralkyl group. R ^{3 to} R ⁵ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a dialkylamino group, or a diarylamino group, and R ^{1 to} R ^5. The above substituent represented by may further have a substituent.)
(Claim 11)
It has the process of removing an exposure part with an alkaline developer, after drawing an image using a violet laser beam on the photosensitive layer of the lithographic printing plate material according to any one of claims 1 to 10. Image forming method.

  According to the present invention, a lithographic printing plate material excellent in storage stability at high humidity can be provided, and an image from the lithographic printing plate material is excellent in reproducibility of a shadow portion.

  Hereinafter, the present invention will be described in detail.

  Specific examples of the compound having at least one bond that can be decomposed by an acid used in the present invention (hereinafter referred to as “acid-decomposing compound”) are disclosed in JP-A-48-89003, 51-120714, 53-. Compounds having a C—O—C bond described in JP-A Nos. 133429, 55-12995, 55-126236, and 56-17345, and JP-A-60-37549 and JP-A-60-121446. Compounds having a Si—O—C bond described in each of the publications, other acid-decomposing compounds described in the publications of JP-A-60-3625 and JP-A-60-10247, and Compounds having Si—N bond described in JP-A-62-222246, carbonates described in JP-A-62-251743, JP-A-62-228084 Orthosilicates described in Japanese Patent Publication No. JP-A-63-10153, acetals and ketals described in JP-A No. 63-10153, and compounds having a C—S bond described in JP-A No. 62-244038. Can be mentioned.

  Among the above, the C—O—C bond described in JP-A-53-133429, JP-A-56-17345, JP-A-60-112446, JP-A-60-37549, and JP-A-63-10153 , Compounds having an Si—O—C bond, orthocarbonates, acetals, ketals and silyl ethers are preferred.

  Among them, an organic polymerization compound having a repeating acetal or ketal moiety in the main chain described in JP-A-53-133429, and its solubility in a developer is increased by the action of an acid, and JP-A A compound having the following structural unit described in JP-A-63-10153 and capable of being decomposed by an acid is particularly preferable.

  Specific examples of the acid-decomposing compound used in the present invention include the compounds described in the above publications. Moreover, the synthesis method of this compound is described in said each gazette.

In the present invention, a compound having a — (CH ₂ CH ₂ O) _n — group (n represents an integer of 2 to 5) is preferable as the acid-decomposing compound from the viewpoint of balance between sensitivity and developability. Of these compounds, compounds having an ethyleneoxy group chain number n of 3 or 4 are particularly preferred. The _{- (CH 2 CH 2 O)} n - Examples of the compound having a group, condensation of dimethoxy cyclohexane, and benzaldehyde and substituted derivatives thereof, diethylene glycol, triethylene glycol, tetraethylene glycol, either as pentaethylene glycol Products.

Moreover, in this invention, the compound represented by the said General formula (1) as an acid decomposition compound is preferable from the point of a sensitivity and developability. In the general formula (1), the alkyl group represented by R, R ₁ and R ₂ may be linear or branched. For example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, t-butyl group, pentyl group Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a t-butoxy group, and a pentoxy group. The sulfo group and the carboxyl group include salts thereof. To do. Of the compounds represented by the general formula (1), compounds in which m and n are 1 or 2 are particularly preferable. The compound represented by the general formula (1) can be synthesized by a known method.

  In the present invention, the content of the acid-decomposing compound is preferably 5 to 70% by mass, particularly preferably 10 to 50% by mass, based on the total solid content of the composition forming the photosensitive layer. The acid decomposition compound may be used alone or in combination of two or more.

  The photoacid generator contained in the acid generator composition capable of generating an acid upon irradiation with the violet laser beam according to the present invention will be described.

As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192). Examples of compounds suitable for the present invention are listed below. First, mention may be made of B (C ₆ F ₅ ) ⁴⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. Can do. Those having a borate compound as a counter anion are preferred because of their high acid generating ability. Specific examples of the onium compound are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned. Specific compounds are exemplified below.

  Thirdly, a halide that generates hydrogen halide can also be used. In the present invention, the halogen compound represented by the general formula (I) is preferably used. Among these, the halogen compound represented by the general formula (II) is particularly preferably used.

In the general formula (I), R ¹ represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an acyl group, an alkylsulfonyl group, an arylsulfonyl group or a cyano group. R ² represents a monovalent substituent. R ¹ and R ² may combine to form a ring. Y ₃ represents a halogen atom.

In the general formula (II), R ³ represents a monovalent substituent. X represents —O— or —NR ⁴ —. R ⁴ represents a hydrogen atom or an alkyl group. R ³ and R ⁴ may combine to form a ring. Y represents a halogen atom.

  Specific examples of the structure represented by the general formula (II) include compounds from BR1 to BR67. As these compounds, compounds in which the halogen atom is replaced from bromine to chlorine can also be suitably used in the present invention.

  Examples of other specific compounds are shown below.

  Fourthly, iron arene complex compounds can be mentioned. In the present invention, this iron arene complex compound is particularly preferably used. The iron arene complex compound used in the present invention is preferably a compound represented by the following general formula (a).

Formula (a) [A-Fe-B] + X ⁻
In the formula, A represents a cyclopentadienyl group or an alkyl-substituted cyclopentadienyl group. In the formula, B represents arene. In the formula, X ⁻ represents an anion. Arene represents a compound having an aromatic ring, and specific examples include benzene, toluene, xylene, cumene, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, biphenyl, fluorene and the like. Examples of X ⁻ include PF ₆ ⁻ , BF ₄ ⁻ , SbF ₆ ⁻ , AlF ₄ ⁻ , CF ₃ SO ₃ ^{− and the} like.

  It is preferable to contain an iron arene complex compound in the ratio of 0.1-20 mass% with respect to the compound which has a group which can superpose | polymerize, More preferably, it is 0.1-10 mass%.

  Examples of the iron arene complex compound include compounds described in JP-A-59-219307, and more preferable specific examples include η-benzene- (η-cyclopentadienyl) iron hexafluorophosphate, η -Cumene- (η-cyclopentadienyl) iron hexafluorophosphate, η-fluorene- (η-cyclopentadienyl) iron hexafluorophosphate, η-naphthalene- (η-cyclopentadienyl) iron hexafluorophosphate, η-xylene- (η-cyclopentadienyl) iron hexafluorophosphate, η-benzene- (η-cyclopentadienyl) iron tetrafluoroborate, and the like.

  As the dye having an absorption maximum between 350 to 440 nm according to the present invention, the compound represented by the general formula (2) is used.

In the formula, R ^{1 to} R ⁶ are hydrogen atoms, alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group). Group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aryl group ( For example, phenyl group, naphthyl group, etc.), heteroaryl group (for example, furyl group, thienyl group, pyridyl group, pyridazyl group, pyrimidyl group, pyrazyl group, triazyl group, imidazolyl group, pyrazolyl group, thiazolyl group, benzoimidazolyl group, benzo Oxazolyl group, quinazolyl group, phthalazyl group, etc.), hete Ring groups (eg, pyrrolidyl, imidazolidyl, morpholyl, oxazolidyl, etc.), alkoxy groups (eg, methoxy, ethoxy, propyloxy, pentyloxy, hexyloxy, octyloxy, dodecyloxy, etc.) ), A cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), an aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), an alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, Hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, Methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (For example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl Group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group) Cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group) Octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonyl) Amino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group Naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylamino) Carbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group) , Dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group) , Ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethyl Sulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group) , Ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2 Pyridylamino group), a halogen atom (e.g., fluorine atom, chlorine atom, bromine atom), a cyano group, a nitro group, a hydroxyl group, and the like. These substituents may be further substituted with the above substituents. In addition, a plurality of these substituents may be bonded to each other to form a ring.

Of these, coumarins having an amino group, an alkylamino group, a dialkylamino group, an arylamino group, a diarylamino group or an alkylarylamino group as R ⁵ are particularly preferred. In this case, it is also possible to preferably use those in which an alkyl group substituted with an amino group forms a ring with the substituents R ⁴ and R ⁶ .

Further, either R ¹ or R ² or both are alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, Tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), heteroaryl Group (for example, furyl group, thienyl group, pyridyl group, pyridazyl group, pyrimidyl group, pyrazyl group, triazyl group, imidazolyl group, pyrazolyl group, thiazolyl group, benzoimidazolyl group, benzoxazolyl group, quinazolyl group, phthalazyl group, etc.) A heterocyclic group (eg, pyrrolidyl group, imidazolid Group, morpholyl group, oxazolidyl group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, Phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group) Octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl) Group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, Butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, Phthalylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (Eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), cyano group, nitro group, halogenated alkyl group (eg, trifluoro) (Methyl group, tribromomethyl group, trichloromethyl group, etc.) are more preferable.

  Although the following compound is mentioned as a preferable specific example, it is not limited to this.

  In addition to the above specific examples, coumarin derivatives of B-1 to B-22 in JP-A-8-129258, coumarin derivatives of D-1 to D-32 in JP-A-2003-21901, JP-A-2002-363206 No. 1 to 21 Coumarin Derivatives, JP-A No. 2002-363207 No. 1 to 40 Coumarin Derivatives, JP-A No. 2002-363208 No. 1 to 34 Coumarin Derivatives, JP-A No. 2002-363209 No. 1 56 coumarin derivatives and the like can also be preferably used.

  The addition amount of the dye having an absorption maximum between 350 to 440 nm represented by the general formula (2) according to the present invention in the photosensitive layer is such that the reflection density of the printing plate at the recording light source wavelength is from 0.1. The amount is preferably in the range of 1.2. The mass ratio of the dye in the photosensitive layer within this range varies greatly depending on the molecular extinction coefficient of each dye and the degree of crystallinity in the photosensitive layer, but is generally from 0.5% by mass to 10% by mass. Often in the range.

In the dye represented by the general formula (3) and having an absorption maximum between 350 to 440 nm, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or a substituent, and at least R ¹ and R ² Or R ² and R ³ are linked to form a ring. Furthermore, the compound represented by the structure of General formula (6) is more preferable.

In the formula, R ⁴ has a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. Represents an optionally substituted heterocyclic group. R ⁵ and R ⁶ each represent a substituent that can be linked to form a ring. X ¹ and X ² each independently represent —CR ⁷ R ⁸ —, —O—, —S—, —NR ⁹ —. R ⁷ , R ⁸ , and R ⁹ are each independently a hydrogen atom, an alkyl group that may have a substituent, an alkenyl group that may have a substituent, or an aryl group that may have a substituent. Represents a heterocyclic group which may have a substituent.

  Typical examples of the above compounds are as follows.

  The dye represented by the general formula (4) having an absorption maximum between 350 to 440 nm is more preferably a dye represented by the general formula (7), (8) or (9).

In general formulas (7), (8), and (9), A and Y have the same meanings as in general formula (4), and X ₃ , X ₄ , and Z each independently represent an O atom, S atom, or NR ₅ . R ₅ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, R ₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, an aryloxy group, an aryl Represents a carbonyl group, an arylthiocarbonyl group, an alkylthio group, an arylthio group, an alkylamino group or an arylamino group, and R ₃ represents a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group Group, an alkylthio group, an arylthio group, an alkylamino group or an arylamino group, wherein R ₄ represents a hydrogen atom, a substituted or unsubstituted alkyl group. Represents an aryl group, an aryl group or a heteroaryl group.

  General formulas (4), (7), (8), and (9) will be described in more detail.

A represents an S atom or NR ₁ , R ₁ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and Y, together with the adjacent A and carbon atoms, forms the basic nucleus of the dye Represents a nonmetallic atomic group. Next, preferred examples of R ₁ will be specifically described.

  Examples of preferable alkyl groups include linear, branched, and cyclic alkyl groups having 1 to 20 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, a propyl group, Butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, s-butyl, Examples thereof include t-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl group and 2-norbornyl. Of these, linear alkyl groups having 1 to 12 carbon atoms, branched alkyl groups having 3 to 12 carbon atoms, and cyclic alkyl groups having 5 to 10 carbon atoms are more preferable.

As the substituent of the substituted alkyl group, a monovalent nonmetallic atomic group excluding hydrogen is used, and preferred examples include a halogen atom (—F, —Br, —Cl, —I), a hydroxyl group, an alkoxy group, Aryloxy group, mercapto group, alkylthio group, arylthio group, alkyldithio group, aryldithio group, amino group, N-alkylamino group, N, N-dialkylamino group, N-arylamino group, N, N-diarylamino group N-alkyl-N-arylamino group, acyloxy group, carbamoyloxy group, N-alkylcarbamoyloxy group, N-arylcarbamoyloxy group, N, N-dialkylcarbamoyloxy group, N, N-diarylcarbamoyloxy group, N-alkyl-N-arylcarbamoyloxy group, alkylsulfoxy group, Reelsulfoxy group, acylthio group, acylamino group, N-alkylacylamino group, N-arylacylamino group, ureido group, N'-alkylureido group, N ', N'-dialkylureido group, N'-arylureido Group, N ′, N′-diarylureido group, N′-alkyl-N′-arylureido group, N-alkylureido group, N-arylureido group, N′-alkyl-N-alkylureido group, N′- Alkyl-N-arylureido group, N ', N'-dialkyl-N-alkylureido group, N', N'-dialkyl-N-arylureido group, N'-aryl-N-alkylureido group, N'- Aryl-N-arylureido group, N ′, N′-diaryl-N-alkylureido group, N ′, N′-diaryl-N-ary Luureido group, N′-alkyl-N′-aryl-N-alkylureido group, N′-alkyl-N′-aryl-N-arylureido group, alkoxycarbonylamino group, aryloxycarbonylamino group, N-alkyl- N-alkoxycarbonylamino group, N-alkyl-N-aryloxycarbonylamino group, N-aryl-N-alkoxycarbonylamino group, N-aryl-N-aryloxycarbonylamino group, formyl group, acyl group, carboxyl group , Alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N-alkylcarbamoyl group, N, N-dialkylcarbamoyl group, N-arylcarbamoyl group, N, N-diarylcarbamoyl group, N-alkyl-N-arylcarbamoyl group , Alkylsul Finyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, sulfo group (—SO ₃ H) and its conjugate base group (hereinafter referred to as sulfonate group), alkoxysulfonyl group, aryloxysulfonyl group, sulfinamoyl group, N -Alkylsulfinamoyl group, N, N-dialkylsulfinamoyl group, N-arylsulfinamoyl group, N, N-diarylsulfinamoyl group, N-alkyl-N-arylsulfinamoyl group, sulfamoyl group, N-alkylsulfamoyl group, N, N-dialkylsulfamoyl group, N-arylsulfamoyl group, N, N-diarylsulfamoyl group, N-alkyl-N-arylsulfamoyl group, phosphono group (-PO ₃ H ₂₎ and its conjugated base group (hereinafter, phosphonato And referred), a dialkyl phosphono group _{(-PO 3 (alkyl) 2)} , diaryl phosphono group _{(-PO 3 (aryl) 2)} , alkyl aryl phosphono group _{(-PO 3 (alkyl) (aryl} )), mono Alkyl phosphono group (—PO ₃ H (alkyl)) and its conjugate base group (hereinafter referred to as alkyl phosphonate group), monoaryl phosphono group (—PO ₃ H (aryl)) and its conjugate base group (hereinafter referred to as “alkyl phosphonate group”) , Arylphosphonate group), phosphonooxy group (—OPO ₃ H ₂ ) and its conjugate base group (hereinafter referred to as phosphonateoxy group), dialkylphosphonooxy group (—OPO ₃ (alkyl) ₂ ). , diaryl phosphonooxy group _{(-OPO 3 (aryl) 2)} , alkylaryl phosphonooxy group (-OPO ₃ (alky ) (Aryl)), monoalkyl phosphonooxy group (-OPO ₃ H (alkyl)) and its conjugated base group (hereinafter referred to as alkyl phosphonophenyl group), monoaryl phosphonooxy group (-OPO ₃ H ( aryl)) and conjugated base groups thereof (hereinafter referred to as arylphosphonatooxy groups), cyano groups, nitro groups, aryl groups, heteroaryl groups, alkenyl groups, and alkynyl groups.

  Specific examples of the alkyl group in these substituents include the aforementioned alkyl groups, and specific examples of the aryl group include a phenyl group, a biphenyl group, a naphthyl group, a tolyl group, a xylyl group, a mesityl group, a cumenyl group, Chlorophenyl group, bromophenyl group, chloromethylphenyl group, hydroxyphenyl group, methoxyphenyl group, ethoxyphenyl group, phenoxyphenyl group, acetoxyphenyl group, benzoyloxyphenyl group, methylthiophenyl group, phenylthiophenyl group, methylaminophenyl Group, dimethylaminophenyl group, acetylaminophenyl group, carboxyphenyl group, methoxycarbonylphenyl group, ethoxyphenylcarbonyl group, phenoxycarbonylphenyl group, N-phenylcarbamoylphenyl group, phenyl group, Anofeniru group, sulfophenyl group, sulfonatophenyl group, phosphonophenyl phenyl group, and a phosphonophenyl phenyl group. As the heteroaryl group, a monocyclic or polycyclic aromatic ring containing at least one of nitrogen, oxygen, and sulfur atoms is used, and preferably 5-membered or 6-membered aromatic substitution such as furan, pyrrole, or pyridine. Groups can be used.

Examples of alkenyl groups include vinyl group, 1-propenyl group, 1-butenyl group, cinnamyl group, 2-chloro-1-ethenyl group, and the like. Examples of alkynyl groups include ethynyl group, 1- A propynyl group, a 1-butynyl group, a trimethylsilylethynyl group, etc. are mentioned. Examples of G ₁ in the acyl group (G ₁ CO—) include hydrogen and the above alkyl groups and aryl groups. Among these substituents, even more preferred are halogen atoms (—F, —Br, —Cl, —I), alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, N-alkylamino groups, N, N— Dialkylamino group, acyloxy group, N-alkylcarbamoyloxy group, N-arylcarbamoyloxy group, acylamino group, formyl group, acyl group, carboxyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N-alkylcarbamoyl group N, N-dialkylcarbamoyl group, N-arylcarbamoyl group, N-alkyl-N-arylcarbamoyl group, sulfo group, sulfonate group, sulfamoyl group, N-alkylsulfamoyl group, N, N-dialkylsulfamoyl group Group, N-arylsulfa Yl group, N-alkyl-N-arylsulfamoyl group, phosphono group, phosphonate group, dialkyl phosphono group, diaryl phosphono group, monoalkyl phosphono group, alkyl phosphonate group, monoaryl phosphono group, aryl phosphine group Examples include an onato group, a phosphonooxy group, a phosphonateoxy group, an aryl group, and an alkenyl group.

  On the other hand, examples of the alkylene group in the substituted alkyl group include a divalent organic residue obtained by removing any one of the hydrogen atoms on the alkyl group having 1 to 20 carbon atoms. Preferred examples include linear alkylene groups having 1 to 12 carbon atoms, branched chains having 3 to 12 carbon atoms, and cyclic alkylene groups having 5 to 10 carbon atoms.

Specific examples of preferred substituted alkyl groups as R ₁ obtained by combining a substituent and an alkylene group include chloromethyl group, bromomethyl group, 2-chloroethyl group, trifluoromethyl group, methoxymethyl group, methoxyethoxyethyl group, Allyloxymethyl group, phenoxymethyl group, methylthiomethyl group, tolylthiomethyl group, ethylaminoethyl group, diethylaminopropyl group, morpholinopropyl group, acetyloxymethyl group, benzoyloxymethyl group, N-cyclohexylcarbamoyloxyethyl group, N -Phenylcarbamoyloxyethyl group, acetylaminoethyl group, N-methylbenzoylaminopropyl group, 2-oxoethyl group, 2-oxopropyl group, carboxypropyl group, methoxycarbonylethyl group, allyl Xoxycarbonylbutyl group, chlorophenoxycarbonylmethyl group, carbamoylmethyl group, N-methylcarbamoylethyl group, N, N-dipropylcarbamoylmethyl group, N- (methoxyphenyl) carbamoylethyl group, N-methyl-N- (sulfo) Phenyl) carbamoylmethyl group, sulfobutyl group, sulfonatobutyl group, sulfamoylbutyl group, N-ethylsulfamoylmethyl group, N, N-dipropylsulfamoylpropyl group, N-tolylsulfamoylpropyl group, N-methyl -N- (phosphonophenyl) sulfamoyloctyl group, phosphonobutyl group, phosphonatohexyl group, diethylphosphonobutyl group, diphenylphosphonopropyl group, methylphosphonobutyl group, methylphosphonatobutyl group, tolylphospho Nohexyl group, tolylphosphonatohexyl group, phosphonooxypropyl group, phosphonatoxybutyl group, benzyl group, phenethyl group, α-methylbenzyl group, 1-methyl-1-phenylethyl group, p-methylbenzyl group, cinnamyl Group, allyl group, 1-propenylmethyl group, 2-butenyl group, 2-methylallyl group, 2-methylpropenylmethyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group and the like.

Specific examples of preferred aryl groups as R ₁ include those in which 1 to 3 benzene rings form a condensed ring, and those in which a benzene ring and a 5-membered unsaturated ring form a condensed ring. Examples include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, an acenaphthenyl group, and a fluorenyl group. Among these, a phenyl group and a naphthyl group are more preferable.

As a specific example of a substituted aryl group preferable as R ₁ , those having a monovalent nonmetallic atomic group excluding hydrogen as a substituent on the ring-forming carbon atom of the aforementioned aryl group are used. Examples of preferred substituents include the alkyl groups, substituted alkyl groups, and those previously shown as substituents in the substituted alkyl group. Preferable specific examples of such a substituted aryl group include a biphenyl group, a tolyl group, a xylyl group, a mesityl group, a cumenyl group, a chlorophenyl group, a bromophenyl group, a fluorophenyl group, a chloromethylphenyl group, a trifluoromethylphenyl group, Hydroxyphenyl group, methoxyphenyl group, methoxyethoxyphenyl group, allyloxyphenyl group, phenoxyphenyl group, methylthiophenyl group, tolylthiophenyl group, ethylaminophenyl group, diethylaminophenyl group, morpholinophenyl group, acetyloxyphenyl group, benzoyl Oxyphenyl group, N-cyclohexylcarbamoyloxyphenyl group, N-phenylcarbamoyloxyphenyl group, acetylaminophenyl group, N-methylbenzoylaminophenyl group, carbo Cyphenyl group, methoxycarbonylphenyl group, allyloxycarbonylphenyl group, chlorophenoxycarbonylphenyl group, carbamoylphenyl group, N-methylcarbamoylphenyl group, N, N-dipropylcarbamoylphenyl group, N- (methoxyphenyl) carbamoylphenyl group N-methyl-N- (sulfophenyl) carbamoylphenyl group, sulfophenyl group, sulfonatophenyl group, sulfamoylphenyl group, N-ethylsulfamoylphenyl group, N, N-dipropylsulfamoylphenyl group, N-tolylsulfamoylphenyl group, N-methyl-N- (phosphonophenyl) sulfamoylphenyl group, phosphonophenyl group, phosphonatophenyl group, diethylphosphonophenyl group, diphenylphosphono Enyl group, methylphosphonophenyl group, methylphosphonatophenyl group, tolylphosphonophenyl group, tolylphosphonatophenyl group, allyl group, 1-propenylmethyl group, 2-butenyl group, 2-methylallylphenyl group, 2- Examples thereof include a methylpropenylphenyl group, a 2-propynylphenyl group, a 2-butynylphenyl group, and a 3-butynylphenyl group.

  Next, Y in the general formula (4) will be described. Y represents a nonmetallic atomic group necessary for forming a heterocyclic ring together with the above-mentioned A and adjacent carbon atoms. Examples of such heterocycle include 5-, 6-, and 7-membered nitrogen-containing or sulfur-containing heterocycles, and preferably 5- or 6-membered heterocycles.

  Examples of nitrogen-containing heterocycles include L.I. G. Brooker et al. , J .; Am. Chem. Soc. 73, 5326-5358 (1951) and those known to constitute basic nuclei in the merocyanine dyes described in the references can be suitably used.

  Specific examples include thiazoles (for example, thiazole, 4-methylthiazole, 4-phenylthiazole, 5-methylthiazole, 5-phenylthiazole, 4,5-dimethylthiazole, 4,5-diphenylthiazole, 4,5- Di (p-methoxyphenylthiazole), 4- (2-thienyl) thiazole, etc.), benzothiazoles (for example, benzothiazole, 4-chlorobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chloro Benzothiazole, 4-methylbenzothiazole, 5-methylbenzothiazole, 6-methylbenzothiazole, 5-bromobenzothiazole, 4-phenylbenzothiazole, 5-phenylbenzothiazole, 4-methoxybenzothiazole, 5-methoxybenzothiazole Z , 6-methoxybenzothiazole, 5-iodobenzothiazole, 6-iodobenzothiazole, 4-ethoxybenzothiazole, 5-ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6-dimethoxybenzothiazole, 5,6-dioxy Methylenebenzothiazole, 5-hydroxybenzothiazole, 6-hydroxybenzothiazole, 6-dimethylaminobenzothiazole, 5-ethoxycarbonylbenzothiazole, etc.), naphthothiazoles (for example, naphtho [1,2] thiazole, naphtho [2, 1] thiazole, 5-methoxynaphtho [2,1] thiazole, 5-ethoxynaphtho [2,1] thiazole, 8-methoxynaphtho [1,2] thiazole, 7-methoxynaphtho [1,2] thiazole, etc.) , Chianafuteno 7 ', 6', 4,5-thiazole (for example, 4'-methoxythianaphtheno-7 ', 6', 4,5-thiazole, etc.), oxazole (for example, 4-methyloxazole, 5-methyloxazole) 4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole, 5-phenyloxazole, etc.), benzoxazoles (for example, benzoxazole, 5-chlorobenzoxazole, 5-methyl Benzoxazole, 5-phenylbenzoxazole, 6-methylbenzoxazole, 5,6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, 6-methoxybenzoxazole, 5-methoxybenzoxazole, 4-ethoxybenzoxazole, 5 - Lorobenzoxazole, 6-methoxybenzoxazole, 5-hydroxybenzoxazole, 6-hydroxybenzoxazole, etc.), naphthoxazoles (eg, naphtho [1,2] oxazole, naphtho [2,1] oxazole, etc.), selenazoles (For example, 4-methylselenazole, 4-phenylselenazole, etc.), benzoselenazoles (for example, benzoselenazole, 5-chlorobenzoselenazole, 5-methoxybenzoselenazole, 5-hydroxybenzoselenazole, tetrahydro Benzoselenazole etc.), naphthoselenazoles (eg naphtho [1,2] selenazole, naphtho [2,1] selenazole etc.), thiazolines (eg thiazoline, 4-methylthiazoline etc.), 2-quinolines ( For example, Kinori 3-methylquinoline, 5-methylquinoline, 7-methylquinoline, 8-methylquinoline, 6-chloroquinoline, 8-chloroquinoline, 6-methoxyquinoline, 6-ethoxyquinoline, 6-hydroxyquinoline, 8-hydroxyquinoline Etc.), 4-quinolines (eg quinoline, 6-methoxyquinoline, 7-methylquinoline, 8-methylquinoline etc.), 1-isoquinolines (eg isoquinoline, 3,4-dihydroisoquinoline etc.), 3-isoquinoline (Eg, isoquinoline), benzimidazoles (eg, 1,3-diethylbenzimidazole, 1-ethyl-3-phenylbenzimidazole, etc.), 3,3-dialkylindolenins (eg, 3,3-dimethyl) Indolenine, 3,3,5, -trimethylindolenine, , 3,7, - trimethyl indolenine, etc.), 2-pyridines (e.g., pyridine, 5-methyl-pyridine, etc.), 4-pyridine (for example, a pyridine, etc.) or the like.

  Examples of the sulfur-containing heterocycle include a dithiol partial structure in dyes described in JP-A-3-296759. Specific examples include benzodithiols (for example, benzodithiol, 5-t-butylbenzodithiol, 5-methylbenzodithiol, etc.), naphthodithiols (for example, naphtho [1,2] dithiol, naphtho [2,1] Dithiols, etc.), dithiols (for example, 4,5-dimethyldithiols, 4-phenyldithiols, 4-methoxycarbonyldithiols, 4,5-dimethoxycarbonylbenzodithiols, 4,5-ditrifluoromethyldithiols, 4 , 5-dicyanodithiol, 4-methoxycarbonylmethyldithiol, 4-carboxymethyldithiol, etc.).

  In the general formulas (4), (7), (8), and (9) described above, among the examples of the nitrogen-containing or sulfur heterocycle formed by Y together with the above-mentioned A and the adjacent carbon atom, A dye having a structure represented by the following partial structural formula (1-A) is particularly preferable because it provides a photopolymerizable composition having high sensitizing ability and extremely excellent storage stability.

In the partial structural formula (1-A), A has the same meaning as in the general formula (4), X ₅ and X ₆ each independently represent a substituted or unsubstituted alkyl group, aryl group or heteroaryl group, ₅ , X ₆ may be bonded to each other to form a 5-, 6- or 7-membered ring. Specific examples of X ₅ and X ₆ include the examples of the substituted or unsubstituted alkyl group and aryl group previously mentioned as examples of R ₂ .

Next, X ₁ and X ₂ in the general formula (4) will be specifically described.

X ₁ and X ₂ are each independently a monovalent non-metallic atomic group such as a hydrogen atom, a halogen atom (—F, —Br, —Cl, —I), a hydroxyl group, an alkoxy group, an aryloxy group, a mercapto group , Alkylthio group, arylthio group, alkyldithio group, aryldithio group, amino group, N-alkylamino group, N, N-dialkylamino group, N-arylamino group, N, N-diarylamino group, N-alkyl- N-arylamino group, acyloxy group, carbamoyloxy group, N-alkylcarbamoyloxy group, N-arylcarbamoyloxy group, N, N-dialkylcarbamoyloxy group, N, N-diarylcarbamoyloxy group, N-alkyl-N -Arylcarbamoyloxy group, alkylsulfoxy group, arylsulfoxy group, Ruthio group, acylamino group, N-alkylacylamino group, N-arylacylamino group, ureido group, N′-alkylureido group, N ′, N′-dialkylureido group, N′-arylureido group, N ′, N'-diarylureido group, N'-alkyl-N'-arylureido group, N-alkylureido group, N-arylureido group, N'-alkyl-N-alkylureido group, N'-alkyl-N-aryl Ureido group, N ′, N′-dialkyl-N-alkylureido group, N ′, N′-dialkyl-N-arylureido group, N-aryl-N-alkylureido group, N′-aryl-N-arylureido N ', N'-diaryl-N-alkylureido group, N', N'-diaryl-N-arylureido group, N'-alkyl -N'-aryl-N-alkylureido group, N'-alkyl-N'-aryl-N-arylureido group, alkoxycarbonylamino group, aryloxycarbonylamino group, N-alkyl-N-alkoxycarbonylamino group, N-alkyl-N-aryloxycarbonylamino group, N-aryl-N-alkoxycarbonylamino group, N-aryl-N-aryloxycarbonylamino group, formyl group, acyl group, carboxyl group, alkoxycarbonyl group, aryloxy Carbonyl group, carbamoyl group, N-alkylcarbamoyl group, N, N-dialkylcarbamoyl group, N-arylcarbamoyl group, N, N-diarylcarbamoyl group, N-alkyl-N-arylcarbamoyl group, alkylsulfinyl group, arylsulfuric group Group, an alkylsulfonyl group, an arylsulfonyl group, a sulfo group (-SO ₃ H) and its conjugated base group (hereinafter referred to as sulfonato group), alkoxy sulfonyl group, aryloxy sulfonyl group, sulfinamoyl group, N- alkylsulfamoyl Fina Moyl group, N, N-dialkylsulfinamoyl group, N-arylsulfinamoyl group, N, N-diarylsulfinamoyl group, N-alkyl-N-arylsulfinamoyl group, sulfamoyl group, N-alkylsulfato group Famoyl group, N, N-dialkylsulfamoyl group, N-arylsulfamoyl group, N, N-diarylsulfamoyl group, N-alkyl-N-arylsulfamoyl group, phosphono group (—PO ₃ H ₂ ) and its conjugate base group (hereinafter referred to as phosphonate group), dialkylphosphine Ion group (—PO ₃ (alkyl) ₂ ), diaryl phosphono group (—PO ₃ (aryl) ₂ ), alkylaryl phosphono group (—PO ₃ (alkyl) (aryl)), monoalkyl phosphono group ( -PO ₃ H (alkyl)) and its conjugated base group (hereinafter referred to as alkyl phosphonophenyl group), monoaryl phosphono group (-PO ₃ H (aryl)) and its conjugated base group (hereinafter, aryl phosphonophenyl group ), Phosphonooxy group (—OPO ₃ H ₂ ) and its conjugate base group (hereinafter referred to as phosphonatoxy group), dialkyl phosphonooxy group (—OPO ₃ (alkyl) ₂ ), diarylphosphonooxy group _{(-OPO 3 (aryl) 2)} , alkylaryl phosphonooxy group _{(-OPO 3 (alkyl) (aryl} )), Monoaru Le phosphonooxy group (-OPO ₃ H (alkyl)) and its conjugated base group (hereinafter referred to as alkyl phosphonophenyl group), monoaryl phosphonooxy group (-OPO ₃ H (aryl)) and its conjugate base Groups (hereinafter referred to as arylphosphonatooxy groups), cyano groups, nitro groups, substituted or unsubstituted aryl groups, heteroaryl groups, alkenyl groups, and alkynyl groups. This has been explained for R ₁ .

X ₁ and X ₂ are bonded to each other, and L. G. Brooker et al. , J .; Am. Chem. Soc. 73, 5326-5358 (1951) and the merocyanine dyes described in the references may constitute an acidic nucleus.

  Specific examples of the acidic nucleus include a 1,3-dicarbonyl nucleus (for example, 1,3-indandione, 1,3-cyclohexanedione, 5,5-dimethylcyclohexanedione, 1,3-dioxane-4,6- Dione etc.), pyrazolinone nucleus (for example, 3-methyl-1-phenyl-2-pyrazolin-5-one, 1-phenyl-2-pyrazolin-5-one, 1- (2-benzothiazolyl) -3-methyl-2 -Pyrazolin-5-one etc.), isoxazolinone nuclei (eg 3-phenyl-2-isoxazolin-5-one, 3-methyl-2-isoxazolin-5-one etc.), oxindole nuclei (eg 1-alkyl-2,3-dihydro-2-oxindole, etc.), 2,4,6-trioxohexahydropyrimidine nuclei (for example, barbituric acid or 2-thio Barbituric acid and its N-substituted derivatives, such as 1,3-diethylbarbituric acid, 1,3-diethyl-2-thiobarbituric acid, 1,3-dibutylbarbituric acid, 1,3-dibutyl-2-thiobarbituric acid, 1,3-diphenylbarbituric acid, 1,3-diphenyl-2-thiobarbituric acid, 1,3-dimethoxycarbonylmethylbarbituric acid, 1,3-dimethoxycarbonylmethyl-2-thiobarbituric acid, etc.), 2-thio- 2,4-thiazolidinedione nuclei (eg, rhodanine and its N-substituted derivatives such as 3-methylrhodanine, 3-ethylrhodanine, 3-phenylrhodanine, 3-allylrhodanine, 3-benzylrhodanine, 3 -Carboxymethyl rhodanine, 3-carboxyethyl rhodanine, 3-methoxycarbonylmethyl rho Nin, 3-hydroxyethylrhodanine, 3-morpholinoethylrhodanine, etc.), 2-thio-2,4-oxazolidinedione nucleus (ie 2-thio-2,4- (3H, 4H) -oxazoledione nucleus) , For example, 2-ethyl-2-thio-2,4-oxazolidinedione), thianaphthenone nucleus (for example, 3 (2H) -thianaphthenone, 3 (2H) -thianaphthenone-1,1-dioxide, etc.), 2- Thio-2,5-thiazolidinedione nucleus (eg, 3-ethyl-2-thio-2,5-thiazolidinedione, etc.), 2,4-thiazolidinedione nucleus (eg, 2,4-thiazolidinedione, 3-ethyl-2) , 4-thiazolidinedione, 3-phenyl-2,4-thiazolidinedione, etc.), thiazolidinone nucleus (for example, 4-thiazolidinone, 3-ethyl-4- Thiazolidinone, 2-ethylmercapto-4-thizolidinone, 2-methylphenylamino-4-thizolidinone, etc.), 2-imino-2-oxazolin-4-one nucleus (ie, pseudohydantoin nucleus), 2,4-imidazolidinedione Nucleus (ie, hydantoin nucleus such as 2,4-imidazolidinedione, 3-ethyl-2,4-imidazolidinedione, 1,3-diethyl-2,4-imidazolidinedione, etc.), 2-thio-2 , 4-imidazolidinedione nuclei (ie thiohydantoin nuclei such as 2-thio-2,4-imidazolidinedione, 3-ethyl-2-thio-2,4-imidazolidinedione, 1,3-diethyl- 2-thio-2,4-imidazolidinedione, etc.), imidazolin-5-one nucleus (for example, 2-propylmercapto-2-imidazoline-5 ON), furan-5-one nucleus, 4-hydroxy-2 (1H) -pyridinone nucleus (for example, N-methyl-4-hydroxy-2 (1H) -pyridinone, N-methyl-4-hydroxy-2 ( 1H) -quinolinone, N-butyl-4-hydroxy-2 (1H) -quinolinone, etc.), 4-hydroxy-2H-pyran-2-one nucleus (eg 4-hydroxycoumarin etc.), thioindoxyl nucleus (eg , 5-methylthioindoxyl, etc.) and the like, and these acidic nuclei may further have a substituent.

Of these partial structures consisting of X ₁ and X ₂ , dyes having the following partial structural formulas (1-B), (1-C), and (1-D) are particularly preferable.

In the partial structural formulas (1-B), (1-C) and (1-D), X ₃ , X ₄ and Z each independently represent an O atom, an S atom or NR ₅ , and R ₅ represents a substituted or non-substituted group. Represents a substituted alkyl group, a substituted or unsubstituted aryl group, and R ₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylamino group Represents an arylamino group, and R ₃ represents a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group, an arylcarbonyl group, an arylthiocarbonyl group, an alkylthio group, an arylthio group, Represents an alkylamino group or an arylamino group, and R ₄ represents a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, or a heteroaryl group. Represents. As specific examples of each substituent, those already described can be arbitrarily used. Among these, the dye having the structural formula (1-C) is most preferable.

  Although the example of the pigment | dye which concerns on this invention by chemical structural formula E1-E60 below is shown, this invention is not restrict | limited by the following chemical structural formulas.

  The dyes represented by the general formulas (4), (7), (8) and (9) according to the present invention are F.I. M.M. The method described in Hammer et al., “The Cyanine Soybean and Relaminated Compounds” (FM Hamer et al., “The Cyanine Dyes and Related Compounds”), pages 511-611 (1964), KAI ARNE JENSEN and LARS HENRIKSEN and others can be synthesized with reference to the method described in ACTACHEMICA SCANDINAVICA, Vol. 22, pages 1107 to 1128 (1968).

In the dye having an absorption maximum between 350 to 440 nm represented by the general formula (5), R ¹ represents an alkyl group, an aryl group, an alkenyl group, a cycloalkyl group, an aralkyl group, or a heterocyclic group. R ² represents a hydrogen atom, an alkyl group, an aryl group, an alkenyl group, a cycloalkyl group, an aralkyl group or a heterocyclic group. R ^{3 to} R ⁵ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a dialkylamino group or a diarylamino group. The above substituents represented by R ^{1 to} R ⁵ may further have a substituent. Specific compounds are shown below.

  With respect to the dye having an absorption maximum between 350 to 440 nm according to the present invention, various chemical modifications for further improving the characteristics of the photosensitive layer can be performed. For example, by combining a dye and an addition polymerizable compound structure (for example, acryloyl group or methacryloyl group) by a method such as covalent bond, ionic bond, hydrogen bond, etc. Unnecessary precipitation suppression of the dye can be performed.

  Furthermore, in order to enhance the suitability for processing in an alkaline aqueous developer, it is effective to introduce a hydrophilic portion (carboxyl group and its ester, sulfonic acid group and its ester, or an acid group or polar group such as an ethylene oxide group). In particular, ester-type hydrophilic groups have a relatively hydrophobic structure in the photosensitive layer, so that they are excellent in compatibility, and in the developer, acid groups are generated by hydrolysis to increase hydrophilicity.

  In addition, for example, a substituent can be appropriately introduced in order to improve compatibility in the photosensitive layer and to suppress crystal precipitation. For example, in some types of photosensitive systems, unsaturated bonds such as aryl groups and allyl groups may be very effective for improving compatibility, and steric hindrance between the dye π planes may be reduced by introducing a branched alkyl structure. By introducing it, crystal precipitation can be remarkably suppressed. Further, by introducing a phosphonic acid group, an epoxy group, a trialkoxysilyl group, or the like, adhesion to an inorganic substance such as a metal or a metal oxide can be improved. In addition, a method such as polymerization of a sensitizing dye can be used depending on the purpose.

  The usage of these dyes can be arbitrarily set according to the performance design of the light-sensitive material, like the above-mentioned addition polymerizable compound. For example, the compatibility with the photosensitive layer can be enhanced by using two or more dyes in combination. In addition to photosensitivity, the selection of the dye is an important factor in terms of the molar extinction coefficient at the emission wavelength of the light source used. By using a dye having a large molar extinction coefficient, the amount of the dye added can be made relatively small, which is economical and advantageous from the viewpoint of film properties of the photosensitive layer. Since the photosensitivity and resolution of the photosensitive layer and the physical properties of the exposure film are greatly affected by the absorbance at the light source wavelength, the addition amount of the sensitizing dye is appropriately selected in consideration of these. For example, the sensitivity decreases in a low region where the absorbance is 0.1 or less. Also, the resolution becomes low due to the influence of halation. However, for example, for the purpose of curing a thick film having a thickness of 5 μm or more, such a low absorbance may be used instead.

  In the region where the absorbance is as high as 3 or more, most of the light is absorbed on the surface of the photosensitive layer, and the internal curing is inhibited. For example, when used as a printing plate, the film strength and the substrate adhesion are poor. It will be insufficient. When used as a lithographic printing plate used in a relatively thin film thickness, the amount of dye added is such that the absorbance of the photosensitive layer is in the range of 0.1 to 1.5, preferably in the range of 0.25 to 1. It is preferable to set. When used as a lithographic printing plate, this is usually 0.05 to 30 parts by weight, preferably 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the photosensitive layer component. It is a range.

  An alkali-soluble polymer binder is used for the photosensitive layer of the lithographic printing plate material of the present invention. Examples of the alkali-soluble polymer binder include a novolak resin, a polymer having a hydroxystyrene unit, a polymer having a structural unit represented by the following general formula (10), and other known acrylic resins. it can.

  Examples of the novolak resin include phenol / formaldehyde resins, cresol / formaldehyde resins, phenol / cresol / formaldehyde copolycondensation resins described in JP-A-55-57841, and JP-A-55-127553. And a copolycondensation resin of p-substituted phenol and phenol, or cresol and formaldehyde, as described in Japanese Patent Application Publication No. Gazette. Examples of the polymer having a hydroxystyrene unit include polyhydroxystyrene and hydroxystyrene copolymer described in JP-B-52-41050.

  The polymer having the structural unit represented by the general formula (10) is a homopolymer having a repeating structure of only the structural unit, or an unsaturated double bond of the structural unit and another vinyl monomer. A copolymer in which one or more structural units represented by a cleaved structure are combined.

In the general formula (10), R ₁ and R ₂ each represent a hydrogen atom, an alkyl group such as a methyl group or an ethyl group, or a carboxyl group, preferably a hydrogen atom. R ₃ represents a hydrogen atom, a halogen atom such as a chlorine atom or a bromine atom, or an alkyl group such as a methyl group or an ethyl group, preferably a hydrogen atom or a methyl group. R ₄ represents a hydrogen atom, an alkyl group such as a methyl group or an ethyl group, a phenyl group, or a naphthyl group. Y represents a phenylene group or a naphthylene group including those having a substituent. Examples of the substituent include an alkyl group such as a methyl group and an ethyl group, a halogen atom such as a chlorine atom and a bromine atom, a carboxyl group, a methoxy group, and an ethoxy group. The alkoxy group, the hydroxyl group, the sulfo group, the cyano group, the nitro group, the acyl group, and the like are preferable, but those having no substituent or substituted with a methyl group are preferable. X is a divalent organic group for linking a nitrogen atom and an aromatic carbon atom, n represents an integer of 0 to 5, and preferably n is 0.

  More specifically, the polymer having the structural unit represented by the general formula (10) can be represented by, for example, the following (a) to (f).

In (a) to (f), R _{1 to} R ₅ each represent a hydrogen atom, an alkyl group, or a halogen atom, and m, n, l, k, and s each represent mol% of each structural unit.

  A novolac resin, a polymer having a hydroxystyrene unit, a polymer having a structural unit represented by the general formula (10), and an acrylic resin can also be used in combination.

  A preferable embodiment of the present invention includes an embodiment in which the photosensitive layer contains a novolac resin and an acrylic resin. The acrylic resin is a polymer having a structural unit of acrylic acid, methacrylic acid, or esters thereof, and is preferably a polymer having a monomer unit represented by the general formula (10) described above. The novolak resin is preferably contained in the range of 20 to 80% by mass with respect to the photosensitive layer, and the acrylic resin is preferably contained in the range of 1 to 50% by mass with respect to the photosensitive layer. A range is more preferred.

  A preferred embodiment of the present invention includes an embodiment in which the photosensitive layer contains a novolac resin and a nonionic surfactant. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters. Glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, alkylalkanolamide, polyethylene glycol and the like. The novolak resin is preferably contained in the range of 20 to 80% by mass relative to the photosensitive layer, and the nonionic surfactant is preferably contained in the range of 0.01 to 10% by mass relative to the photosensitive layer. The range of 1-1.0 mass% is more preferable.

  Further, an oleophilic resin can be added to the photosensitive layer according to the present invention in order to improve the sensitivity of the photosensitive layer. Examples of the lipophilic resin include condensates of phenols and aldehydes substituted with an alkyl group having 3 to 15 carbon atoms as described in JP-A-50-125806, for example, t- Butylphenol formaldehyde resin can be used.

  If necessary, the photosensitive layer of the lithographic printing plate material of the present invention may further contain a dye, pigment, sensitizer and the like other than those described above.

  The violet laser beam used in the present invention is preferably a laser beam having a wavelength of 350 to 440 nm. As an available laser light source having an emission wavelength of 350 to 440 nm, for example, a combination of a waveguide type wavelength conversion element and AlGaAs, an InGaAs semiconductor (380 to 440 nm), AlGaInN (350 to 440 nm), and a pulse laser XeF (351 nm, pulse 10 to 250 mJ) and the like can be mentioned, and a semiconductor laser is preferably used.

  Scanning methods in laser irradiation include cylindrical outer surface scanning, cylindrical inner surface scanning, and planar scanning. In the cylindrical outer surface scanning, laser exposure is performed while rotating a drum around which the recording material is wound, and the rotation of the drum is the main scanning and the movement of the laser light is the sub scanning. In cylindrical inner surface scanning, a recording material is fixed to the inner surface of a drum, a laser beam is irradiated from the inside, and a main scanning is performed in the circumferential direction by rotating part or all of the optical system. Is linearly moved parallel to the axis of the drum to perform sub-scanning in the axial direction. In plane scanning, a laser beam main scan is performed by combining a polygon mirror, a galvanometer mirror, and an fθ lens, and a sub-scan is performed by moving a recording medium. Cylindrical outer surface scanning and cylindrical inner surface scanning are easier to increase the accuracy of the optical system and are suitable for high-density recording.

  In the present invention, it is preferable to heat-treat the lithographic printing plate material after exposing the image to the lithographic printing plate material and before or during development. By performing the heat treatment in this manner, the adhesion between the photosensitive layer and the support is improved, and the effect of the invention according to the present invention can be improved.

  The preheating according to the present invention is performed by, for example, a preheating roller that heats a photosensitive lithographic printing plate carried during development processing to a predetermined temperature range before development in an automatic developing apparatus that develops photosensitive lithographic printing plate material. The method of heating can be mentioned. For example, the preheat roller is composed of a pair of rollers including at least one roller having heating means inside, and the roller having the heating means includes a hollow pipe made of a metal having high thermal conductivity (for example, aluminum, iron, etc.). In this case, a nichrome wire or the like is embedded as a heating element inside, and the outer surface of the metal pipe is covered with a plastic sheet such as polyethylene, polystyrene, or Teflon (registered trademark). For details of such a preheat roller, reference can be made to JP-A No. 64-80962. The preheating in the present invention is preferably performed at 70 to 180 ° C. for about 3 to 120 seconds.

  The exposed portion of the image-exposed photosensitive layer can be dissolved in the developer. By developing this with an alkaline developer, the exposed portion is removed and image formation becomes possible. As such a developer, a conventionally known alkaline aqueous solution can be used. For example, sodium silicate, same potassium, same ammonium; dibasic sodium phosphate, same potassium, same ammonium; sodium bicarbonate, same potassium, same ammonium; sodium carbonate, same potassium, same ammonium; sodium bicarbonate, same potassium, same Ammonium; sodium borate, potassium, ammonium; alkaline developers using an inorganic alkaline agent such as sodium hydroxide, potassium, ammonium, and lithium.

  Also, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-i-propylamine, di-i-propylamine, tri-i-propylamine, butylamine, monoethanolamine, diethanolamine, triethanolamine, Organic alkali agents such as mono-i-propanolamine, di-i-propanolamine, ethyleneimine, ethylenediamine, and pyridine can also be used.

  These alkaline agents are used alone or in combination of two or more. In addition, an anionic surfactant, an amphoteric surfactant, and an organic solvent such as alcohol can be added to the developer as necessary.

The aqueous solution according to the present invention is basically an aqueous solution having a silicic acid concentration in terms of SiO ₂ of 1.0 mass% and a pH in the range of 8.5 to 12.9, and the aqueous solution contains other additives. It may be. Further, an aqueous solution further containing a surfactant in the range of 0.1% by mass to 5.0% by mass in the aqueous solution is more preferable. The aqueous solution according to the present invention preferably contains the components of the developer described above.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.

Example 1
[Preparation of lithographic printing plate materials]
<Production of support>
An aluminum plate (material 1050, tempered H16) having a thickness of 0.3 mm was immersed in a 5% aqueous sodium hydroxide solution maintained at 65 ° C., degreased for 1 minute, and then washed with water. This degreased aluminum plate was neutralized by immersing it in a 10% sulfuric acid aqueous solution kept at 25 ° C. for 1 minute, and then washed with water. Next, this aluminum plate was subjected to an electrolytic surface roughening treatment for 20 seconds in an alternating current having a hydrochloric acid concentration of 11 g / L, a temperature of 25 ° C., a frequency of 50 Hz, and 50 A / dm ² . After electrolytic surface roughening, it was washed with water, desmutted for 10 seconds in a 1% aqueous sodium hydroxide solution maintained at 50 ° C., washed with water, and then washed in 30% sulfuric acid maintained at 50 ° C. for 30 seconds. Neutralization treatment was performed and washed with water. Next, anodization was performed for 30 seconds in a 30% sulfuric acid solution at 25 ° C., a current density of 30 A / dm ² , and a voltage of 25 V, followed by washing with water. Further, a 0.44% polyvinylphosphonic acid aqueous solution was dipped at 75 ° C. for 30 seconds, then washed with distilled water and dried with cold air at 25 ° C. to obtain a photopolymerizable lithographic printing plate support. At this time, the center line average roughness (Ra) of the surface was 0.50 μm.

<< Photosensitive coating liquid >>
A photosensitive coating solution having the following composition was applied to the support so that the film thickness after drying was 2.0 g / m ² and dried at 95 ° C. for 1 minute to obtain lithographic printing plate materials 1 to 8. .

Novolak resin (novolak resin co-condensed with phenol and m-, p-mixed cresol and formaldehyde: Mw = 4000, molar ratio of phenol / m-cresol / p-cresol is 5/76/19, respectively) 75 parts Acid decomposition Compound A 15 parts Acid generator (Table 1) 5 parts Dye (Table 1) 3 parts Crystal violet 1.8 parts Silicon surfactant (Edaplan LA411) 0.2 parts PGM (propylene glycol monomethyl ether) 500 parts MEK (Methyl ethyl ketone) 400 parts

[Exposure and development]
The obtained lithographic printing plate material is divided into two, one is stored in an environment of 23 ° C. and 55% RH, and the other is stored in an environment of 40 ° C. and 80% RH for 3 days, and an image is formed by the following method. did. The photosensitive layer was exposed imagewise using a laser exposure machine equipped with a 405 nm violet laser with an output of 150 mW. In the comparative example, a laser exposure machine equipped with an infrared semiconductor laser with an output of 500 mW and a wavelength of 830 nm was used. The exposed image includes a solid exposure portion and a 1 to 99% halftone dot image.

  Development was performed at 30 ° C. for 20 seconds with a developer having the following composition.

A Potassium silicate 116 parts KOH aqueous solution (45%) 27 parts Water 715 parts At that time, the unexposed part corresponding to the image part was not dissolved by the development treatment, and a clear image was obtained. The halftone dot% at which the halftone dot image in the shadow portion was clearly removed was evaluated. The larger the value, the better the reproducibility. The results are shown in Table 1.

  From Table 1, it can be seen that the lithographic printing plate material of the present invention is excellent in storage stability at high humidity, and as a result, is excellent in reproducibility of shadow portions.

Claims (11)

It has an acid generator composition capable of generating an acid upon irradiation with a violet laser beam on an aluminum support, a compound having at least one bond that can be decomposed by an acid, and a photosensitive layer containing an alkali-soluble polymer binder. A planographic printing plate material. 2. The lithographic printing plate according to claim 1, wherein the acid generator composition capable of generating an acid upon irradiation with the violet laser beam is a dye having an absorption maximum between 350 and 440 nm and an iron arene complex compound. material. The acid generator composition capable of generating an acid upon irradiation with the violet laser beam contains a dye having an absorption maximum between 350 nm and 440 nm and at least one halogen compound represented by the following general formula (I): 2. The lithographic printing plate material according to claim 1, wherein
Formula (I) R ¹ —CY ₂ — (C═O) —R ²
(Wherein R ¹ represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an acyl group, an alkylsulfonyl group, an arylsulfonyl group or a cyano group. R ² represents a monovalent substituent. R ¹ and R ² may be bonded to form a ring, and Y ₂ represents a halogen atom.) The lithographic printing plate material according to claim 3, wherein the at least one halogen compound represented by the general formula (I) is represented by the following general formula (II).
Formula (II) CY ₃ — (C═O) —X—R ³
(In the formula, R ³ represents a monovalent substituent. X represents —O— or —NR ⁴ —. R ⁴ represents a hydrogen atom or an alkyl group. R ³ and R ⁴ are bonded to form a ring. (Y ₃ represents a halogen atom.) Compound having at least one bond capable of being decomposed by the acid _{- (CH 2 CH 2 O)} n - group (n is an integer of 2 to 5) according to claim 1, characterized in that a compound having a 5. The lithographic printing plate material according to any one of 4 above. The _{- (CH 2 CH 2 O)} n - group (n is an integer of 2 to 5) according to claim 5, the compound having the is characterized in that a compound represented by the following general formula (1) Lithographic printing plate material.

(In the formula, R, R ₁ and R ₂ each represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a sulfo group, a carboxyl group or a hydroxyl group. P, q And r each represents an integer of 1 to 3, and m and n each represents an integer of 1 to 5.) The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (2).

Wherein R ^{1 to} R ⁶ are each a hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, heterocyclic group, alkoxy group, cycloalkoxy group, aryloxy group, alkylthio group Group, cycloalkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, acyl group, acyloxy group, amide group, carbamoyl group, ureido group, sulfinyl group, alkylsulfonyl group, arylsulfonyl group, amino group, Represents a halogen atom, a cyano group, a nitro group or a hydroxyl group, and these substituents may be further substituted with the above-mentioned substituents, and a plurality of these substituents are bonded to each other to form a ring. May be.) The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (3).

(In the formula, R ^{1 to} R ³ each independently represents a hydrogen atom or a substituent, and at least R ¹ and R ² , or R ² and R ³ are linked to form a ring.) The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (4).

(In the formula, A represents an S atom or NR ₁ , R ₁ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and Y represents a base of the dye in combination with the adjacent A and carbon atoms. X ₁ and X ₂ each independently represent a monovalent nonmetallic atomic group, and X ₁ and X ₂ may be bonded to each other to form an acidic nucleus of a dye. Good.) The lithographic printing plate material according to any one of claims 2 to 6, wherein the dye having an absorption maximum between 350 to 440 nm is represented by the following general formula (5).

Wherein R ¹ represents an alkyl group, aryl group, alkenyl group, cycloalkyl group, aralkyl group or heterocyclic group. R ² represents a hydrogen atom, alkyl group, aryl group, alkenyl group, cycloalkyl group or aralkyl group. R ^{3 to} R ⁵ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a dialkylamino group, or a diarylamino group, and R ^{1 to} R ^5. The above substituent represented by may further have a substituent.) It has the process of removing an exposure part with an alkaline developer, after drawing an image using a violet laser beam on the photosensitive layer of the lithographic printing plate material according to any one of claims 1 to 10. Image forming method.