JP2002333709A - Positive type image forming material and positive image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive type image forming material having high sensitivity to light in the near infrared region, excellent in contrast between image and non-image areas, ensuring a wide range of development conditions and excellent also in chemical resistance as a positive type image forming material obtained by forming a layer of a positive type photosensitive composition comprising a photothermal conversion material and an alkali-soluble resin on the surface of a support and to provide a positive image forming method using the material. SOLUTION: The positive type image forming material is obtained by forming a layer of a positive type photosensitive composition comprising a photothermal conversion material which absorbs light of a light source for imagewise exposure and converts it into heat and an alkali-soluble resin on the surface of a support, and the alkali- soluble resin is a phenolic resin in which o-cresol occupies 25-40 mol% of phenol components constituting molecules whose molecular weight is <=2,000 and o-cresol occupies <=25 mol% of phenol components constituting molecules whose molecular weight is >=10,000. In the positive image forming method, the positive type image forming material is subjected to scanning exposure with laser light in the wavelength range of 650-1,300 nm and developed with an alkali developing solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a positive image forming material having a layer of a positive photosensitive composition containing a photothermal conversion substance and an alkali-soluble resin on the surface of a support, and a positive image forming method using the same. Are in the wavelength range of 650 to 1,30
The present invention relates to a positive image forming material suitable for directly forming an image and making a plate by using light in a range of 0 nm, particularly a laser beam such as a semiconductor laser or a YAG laser, and a positive image forming method using the same.

[0002]

2. Description of the Related Art With the advance of computer image processing technology, digital image information is not directly output to a silver halide mask film, but an image is directly formed by laser light.
A TP (Computer to Plate) system has attracted attention. In particular, high power semiconductor lasers and Y
A CTP system using an AG laser, etc., is required to reduce the time required for the plate making process, the ambient light during operation, and the cost of plate making.
Its practical use is rapidly advancing.

Accordingly, as a lithographic printing plate for a CTP system, in recent years, a positive image is formed by using an infrared laser beam and increasing the solubility of an exposed portion in a developing solution mainly by a change other than a chemical change. Photosensitive lithographic printing plates having a layer of a photosensitive composition on the surface of a support have been proposed (for example, JP-A-10-268512, JP-A-11-84657, JP-A-11-174681,
JP-A-11-194504, JP-A-11-22393
No. 6, etc., WO 97/39894, WO 98/4
See each specification such as No. 2507. ).

[0004] In these positive photosensitive lithographic printing plates, conventional positive photosensitive lithographic printing plates typically have a solubility in an exposed part in a developing solution due to a chemical change such as photodecomposition of an o-quinonediazide compound. While a positive image was formed by increasing the amount, a substance that absorbs infrared light such as an infrared absorbing dye and converts it to heat and an alkali-soluble resin such as a novolak resin as main photosensitive components. A substance that is sensitive to white light, such as an o-quinonediazide compound, which increases the solubility of a light-exposed portion in a developer due to physical changes such as structural transition of a resin due to heat generated by exposure to infrared laser light. Lithographic printing plates have the advantage of being able to be handled under white light since they do not need to be contained, while generally the development latitude (exposed areas are completely removed during development) Time at, the difference between the time that the residual film ratio of the unexposed portion can be sufficiently secured) is to also have weaknesses developing narrow.

On the other hand, in a positive photosensitive composition containing a photothermal conversion substance and an alkali-soluble resin, a novolak resin composed of a phenol component having a high proportion of o-cresol may be used as an alkali-soluble resin. As proposed in Japanese Patent Application Laid-Open No. 2001-42519 and the like, a novolak resin having a high ratio of o-cresol tends to decrease the chemical resistance as a positive-type image forming material.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art. Therefore, the present invention provides a positive photosensitive composition comprising a photothermal conversion material and an alkali-soluble resin on the surface of a support. In the positive type image forming material in which the layer of the object is formed, it is highly sensitive to light in the near infrared region,
A positive-type image forming material having excellent contrast between an image portion (non-exposed portion) and a non-image portion (exposed portion), and thus has a wide range of developing conditions and excellent chemical resistance, and a positive image forming material using the same. It is an object to provide an image forming method.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by including a specific phenol resin as an alkali-soluble resin in a photosensitive composition. The present invention has been completed, that is, the present invention, on the surface of the support,
A positive-type image-forming material formed with a layer of a positive-type photosensitive composition containing a photothermal conversion substance that absorbs light from an image exposure light source and converts it into heat, and an alkali-soluble resin, wherein the alkali-soluble resin is The proportion of o-cresol in the phenol component constituting the molecule having a molecular weight of 2,000 or less is 2
A positive-type image forming material containing a phenolic resin having a molar ratio of 5 to 40 mol% and an o-cresol ratio of 25 mol% or less in a phenol component constituting a molecule having a molecular weight of 10,000 or more; Positive image forming material
A gist is a positive image forming method of performing scanning exposure with a laser beam having a wavelength range of 650 to 1,300 nm, and then developing with an alkali developing solution.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The photothermal conversion substance contained in the positive photosensitive composition in the positive image forming material of the present invention is a compound capable of absorbing light from an image exposure light source and converting it into heat. Although not particularly limited, the wavelength range of 650 to 1,30
Among the organic or inorganic dyes and pigments having an absorption band in part or all of the range of 0 nm, organic dyes, metals, metal oxides, metal carbides, metal borides, etc., the light absorbing dyes are particularly effective. . These light-absorbing dyes efficiently absorb light in the above-mentioned wavelength region, but hardly absorb light in the ultraviolet region, or do not substantially respond to absorption, and are weakly sensitive to ultraviolet light contained in white lamps. Is a compound having no action of modifying the photosensitive composition.

In the present invention, these light-absorbing dyes have a structure in which a hetero atom such as a nitrogen atom, an oxygen atom or a sulfur atom is bonded by a polymethine (-CH =) _n chain. Means that the heteroatoms form a heterocycle,
A so-called structure in which a heterocycle is bonded via a polymethine chain,
Cyanine-based dyes in a broad sense, specifically, for example, quinoline-based (so-called cyanine-based in a narrow sense), indole-based (so-called,
Indocyanine-based), benzothiazole-based (so-called thiocyanine-based), pyrylium-based, thiapyrylium-based, squarylium-based, croconium-based, azurenium-based, and the like, and so-called structures in which acyclic heteroatoms are bonded via a polymethine chain. And polymethine dyes, among which cyanine dyes such as quinoline, indole, benzothiazole, pyrylium, and thiapyrylium dyes, and polymethine dyes are preferable.

Other typical examples include diiminium dyes and phthalocyanine dyes, among which diiminium dyes are preferred.

In the present invention, among the cyanine-based dyes, quinoline-based dyes are preferably represented by the following general formula (I)
Those represented by a), (Ib) or (Ic) are preferred.

[0012]

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[In the formulas (Ia), (Ib) and (Ic), R ¹ and R
² each independently has an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or a group which has a substituent. L ¹ represents a tri, penta, hepta, nona, or undecamethine group which may have a substituent, and two substituents on the penta, hepta, nona, or undecamethine group Are linked to each other to have 5 to 7 carbon atoms
May be formed, and the quinoline ring may have a substituent. In this case, two adjacent substituents may be connected to each other to form a fused benzene ring. X ^- is a counter anion. ]

Here, R ¹ in the formulas (Ia), (Ib) and (Ic)
And when R ² is an alkyl group, the number of carbon atoms is usually 1 to 1
5, preferably 1 to 10, the number of carbon atoms when it is an alkenyl group or an alkynyl group is usually 2 to 15, preferably 2 to 1.
0, as those substituents including phenyl groups, from 1 to 15 carbon atoms, preferably 1 to 10 alkoxy group, a phenoxy group, hydroxy group, or a phenyl group and the like, in L ¹ Examples of the substituent include an alkyl group having the same number of carbon atoms, an amino group, and a halogen atom.Examples of the substituent in the quinoline ring include an alkyl group having the same number of carbon atoms, an alkoxy group having the same number of carbon atoms, a nitro group, and a halogen atom. Atoms and the like.

The indole and benzothiazole dyes are particularly preferably those represented by the following general formula (II).

[0016]

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[In the formula (II), Y ¹ and Y ² each independently represent a dialkylmethylene group or a sulfur atom, and R ³ and R ⁴ each independently may have a substituent. An alkyl group, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or a phenyl group which may have a substituent, and L ² has a substituent Represents a tri, penta, hepta, nona, or undecamethine group which may be substituted, and two substituents on the penta, hepta, nona, or undecamethine group are linked to each other to have 5 carbon atoms.
To 7 may form a cycloalkene ring, and the condensed benzene ring may have a substituent. In this case, two adjacent substituents are connected to each other to form a condensed benzene ring. Is also good. X ^- is a counter anion. ]

Here, when R ³ and R ⁴ in the formula (II) are an alkyl group, the number of carbon atoms is usually 1 to 15, preferably 1 to 15.
, An alkenyl group or an alkynyl group usually has 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms.
To 15, preferably 1 to 10, an alkoxy group, a phenoxy group, a hydroxy group, or a phenyl group.
^As the substituent in ² , an alkyl group having the same number of carbon atoms as above,
Examples of an amino group or a halogen atom include substituents on the condensed benzene ring, such as an alkyl group having the same carbon number, an alkoxy group having the same carbon number, a nitro group, and a halogen atom.

Further, as the pyrylium-based and thiapyrylium-based dyes, the following general formulas (IIIa), (IIIb), and
Those represented by (IIIc) are preferred.

[0020]

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[In the formulas (IIIa), (IIIb) and (IIIc), Z ¹
And Z ² each independently represent an oxygen atom or a sulfur atom; R ⁵ , R ⁶ , R ⁷ , and R ⁸ each independently represent a hydrogen atom or an alkyl group, or R ⁵ and R ⁷ , and R ⁶ and R
⁸ may be linked to each other to form a cycloalkene ring having 5 or 6 carbon atoms, and L ³ represents a mono, tri, penta, or heptamethine group which may have a substituent; Two substituents on the penta or heptamethine group may be linked to each other to form a cycloalkene ring having 5 to 7 carbon atoms, and the pyrylium ring and the thiapyrylium ring may have a substituent, In this case, two adjacent substituents may be connected to each other to form a fused benzene ring. X ^- is a counter anion. ]

Here, when R ⁵ , R ⁶ , R ⁷ and R ⁸ in the formulas (IIIa), (IIIb) and (IIIc) are alkyl groups, the number of carbon atoms is usually 1 to 15, preferably 1 to 15. 1 to 10,
The substituent in L ^3, ibid alkyl group of carbon number, an amino group, or a halogen atom, and examples of the substituent in the pyrylium ring and thiapyrylium ring,
And an aryl group such as a phenyl group and a naphthyl group.

As the polymethine dye, those represented by the following general formula (IV) are particularly preferable.

[0024]

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[In the formula (IV), R ⁹ , R ¹⁰ , R ¹¹ and R ¹²
Each independently represents an alkyl group; R ¹³ and R ¹⁴ each independently represent an aryl group, a furyl group, or a thienyl group which may have a substituent; and L ⁴ represents a substituent. A mono-, tri-, penta- or heptamethine group which may be substituted with two substituents on the tri-, penta- or heptamethine group to form a cycloalkene ring having 5 to 7 carbon atoms The quinone ring and the benzene ring may have a substituent. X ^- is a counter anion. ]

The alkyl groups of R ⁹ , R ¹⁰ , R ¹¹ and R ¹² in the formula (IV) generally have 1 to 15, preferably 1 to 10, and R ¹³ and R ¹⁴ are aryl groups. Is usually from 6 to 20, preferably from 6 to 15, and R ¹³
And R ¹⁴ specifically include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-furyl group, a 3-furyl group,
-Thienyl group, 3-thienyl group, and the like. Examples of the substituent include an alkyl group having the same number of carbon atoms, an alkoxy group having the same number of carbon atoms, a dialkylamino group, a hydroxy group,
Or a halogen atom. Examples of the substituent in L ⁴ include an alkyl group having the same carbon number as described above, an amino group, and a halogen atom. Examples of the substituent in the quinone ring and the benzene ring include an alkyl group having the same number of carbon atoms as described above. Groups, alkoxy groups having the same number of carbon atoms, nitro groups, and halogen atoms.

Further, as the diiminium-based dye, those represented by the following formula (Va) or (Vb) having at least one N, N-diaryliminium salt skeleton are particularly preferable.

[0028]

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[In the formulas (Va) and (Vb), R ¹⁵ , R ¹⁶ ,
R ¹⁷ and R ¹⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a group which may have a substituent. A good alkynyl group or an alkoxy group which may have a substituent, wherein R ¹⁹ and R ²⁰ each independently represent an alkyl group which may have a substituent, Alkenyl group which may have a substituent, alkynyl group which may have a substituent, alkoxy group which may have a substituent, acyloxy group which may have a substituent, or It shows a good phenyl group, and the benzene ring and the iminoquinone ring may have a substituent. X ^- is a counter anion. The electronic bond (dotted line) in the formula (Vb) indicates a resonance state with another electronic bond. ]

Here, R ¹⁵ in the formulas (Va) and (Vb),
When R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , and R ²⁰ are an alkyl group or an alkoxy group, the number of carbon atoms is usually 1 to 15, preferably 1 to 10, and the number of carbon atoms when an alkenyl group or an alkynyl group is used. Is usually 2 to 15, preferably 2 to 10, and the substituents therein include an alkyl group having the same number of carbon atoms, an alkoxy group having the same number of carbon atoms, a carboxy group, an acyloxy group, an alkoxycarbonyl group, a hydroxy group, and an amino group. An alkylamino group, a halogenated alkyl group, or a halogen atom.Examples of the substituent on the benzene ring and the iminoquinone ring include an alkyl group having the same carbon number, an alkoxy group having the same carbon number, an acyl group, a nitro group,
Or a halogen atom.

Among these diiminium-based dyes, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁵ in the above formulas (Va) and (Vb)
It is particularly preferred that ¹⁸ is an alkyl group and R ¹⁹ and R ²⁰ are also alkyl groups, or that R ¹⁹ and R ²⁰ are phenyl groups having a dialkylamino group as a substituent.

The compounds represented by the general formulas (Ia to c), (II), and (IIIa to
Examples of the counter anion X ⁻ in (c), (IV) and (Va to b) include, for example, Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , PF
_{^{6 -, SbF 6 -, AsF}} 6 -, and, BF ₄ ^-, BC
l ₄ ^- and inorganic acid anions of the inorganic boric acid or the like, such as, benzene sulfonic acid, toluene sulfonic acid, naphthalene sulfonic acid, acetic acid, and methyl, ethyl, propyl, butyl, phenyl, methoxyphenyl, naphthyl, fluorophenyl, difluorophenyl Organic acid anions such as organic boric acid having an organic group such as phenyl, pentafluorophenyl, thienyl and pyrrolyl can be mentioned.

The quinoline compounds represented by the above formulas (Ia to c), the indole compounds or benzothiazole compounds represented by the above formula (II), and the pyrylium compounds represented by the above formulas (IIIa to c) Or cyanine dyes such as thiapyrylium,
Among the polymethine dyes represented by the general formula (IV), and the diiminium dyes represented by the general formulas (Va to b),
In the present invention, an indole or benzothiazole cyanine dye represented by the general formula (II) is particularly preferable.

The quinoline compounds represented by the general formulas (Ia to c), the indole compounds or benzothiazole compounds represented by the general formula (II), and the pyrylium compounds represented by the general formulas (IIIa to c) Specific examples of a cyanine dye such as a dye or a thiapyrylium dye, a polymethine dye represented by the general formula (IV), and a diiminium dye represented by the general formula (Va to b) are shown below.

[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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In the present invention, the content ratio of the photothermal conversion substance in the positive photosensitive composition is preferably 0.5 to 30% by weight, more preferably 1 to 20% by weight, and 2 to 20% by weight. Particularly preferred is 10% by weight.

As the alkali-soluble resin contained in the positive photosensitive composition in the positive image forming material of the present invention, the proportion of o-cresol in the phenol component constituting a molecule having a molecular weight of 2,000 or less is preferred. The ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 10,000 or more is 25 to 40 mol% and is 2 to 40 mol%.
It is essential to contain a phenol resin of 5 mol% or less.

Here, the phenolic resin includes a novolak resin and a resol resin, and a novolak resin is particularly preferable.

Novolak resins include, for example, phenol,
o-cresol, m-cresol, p-cresol,
2,5-xylenol, 3,5-xylenol, o-ethylphenol, m-ethylphenol, p-ethylphenol, propylphenol, n-butylphenol, t-butylphenol, 1-naphthol, 2-naphthol, 4,4 ′ -At least one phenol such as biphenyldiol, bisphenol-A, pyrocatechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol, phloroglucinol, etc. under the acid catalyst, for example, formaldehyde, acetaldehyde, propion Aldehydes such as aldehyde, benzaldehyde and furfural (paraformaldehyde may be used in place of formaldehyde and paraaldehyde in place of acetaldehyde), or acetone, methylethyl A resin which is polycondensed with at least one of ketones and ketones such as methyl isobutyl ketone, and in the present invention, phenols as phenols, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,5-
Xylenol, resorcinol and formaldehyde, acetaldehyde as aldehydes or ketones,
Polycondensates with propionaldehyde are preferred.

The resole resin is a resin that has been polycondensed in the same manner except that an alkali catalyst is used instead of the acid catalyst in the polycondensation of the novolak resin. Phenols and their mixed compositions, and aldehydes or ketones are preferred.

[0051] The phenolic resin these novolak resins, resol resins, the weight average molecular weight in terms of polystyrene by gel permeation chromatography measurement (M _W) is, preferably has 1,000 to 15,000, 1,500 10,000 is more preferred.

In the present invention, the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 2,000 or less is 25 to 25.
It is essential that the amount is 40 mol%, and
Preferably it is mol%. When the proportion of o-cresol in the phenol component constituting the molecule having a molecular weight of 2,000 or less is less than the above range, the contrast between the image area and the non-image area is inferior as a positive-type image forming material, and therefore, the range of development conditions is low. On the other hand, if it exceeds the above range, the chemical resistance will be inferior.

Furthermore, in the present invention, it is essential that these phenolic resins have a ratio of o-cresol of 25 mol% or less in a phenol component constituting a molecule having a molecular weight of 10,000 or more, It is preferably at most 24 mol%. If the proportion of o-cresol in the phenol component constituting the molecule having a molecular weight of 10,000 or more exceeds the above range, the chemical resistance of the positive type image forming material will be poor.

In the present invention, these phenolic resins have a content of molecules having a molecular weight of 2,000 or less of 45 to 45.
It is preferably 75% by weight, more preferably 50-70% by mole. Further, the content of molecules having a molecular weight of 10,000 or more is preferably 5 to 25% by weight.
More preferably, it is 20% by weight or less.

In the present invention, the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 2,000 or less is as follows.
The proportion of o-cresol in the phenol component constituting the molecule having a molecular weight of 10,000 or more, and preferably, the content of the molecule having a molecular weight of 2,000 or less, and the content of the molecule having a molecular weight of 10,000 or more are as described above. As long as the range is satisfied, one kind of novolak resin or resol resin may be a mixture of two or more kinds of novolak resin or / and resol resin, and in the case of the latter mixture, each before mixing is not necessarily Even if the above range is not satisfied, it suffices if the mixture is satisfied.

The phenolic resin in the present invention includes
For example, a resin having a weight average molecular weight of about 7,000 or more is dissolved in an immiscible mixed solvent of a ketone solvent such as acetone and methyl ethyl ketone and a saturated aliphatic hydrocarbon solvent such as pentane, hexane and heptane. After separation into two layers, a mixture of a resin from which a low molecular weight component is removed by removing a solution phase of a ketone solvent and a resin having a weight average molecular weight of about 2,000 to 6,000. Is preferred.

The positive photosensitive composition of the present invention contains the phenolic resin as an alkali-soluble resin, and the proportion of the phenolic resin in the alkali-soluble resin is at least 80% by weight. Preferably, all the alkali-soluble resins are all the phenolic resins. Examples of the alkali-soluble resin other than the phenol resin include a polyvinyl phenol resin and a copolymer of an acrylic acid derivative having a phenolic hydroxyl group.

In the present invention, the content of the alkali-soluble resin in the positive photosensitive composition is from 50 to 99.
%, More preferably from 60 to 98% by weight, particularly preferably from 70 to 97% by weight.

In the present invention, the positive photosensitive composition containing the photothermal conversion substance and the alkali-soluble resin is used for the purpose of increasing the difference in solubility between exposed and unexposed areas in an alkali developing solution. A dissolution inhibitor which is not decomposed by light in the infrared region may be contained.

Examples of the dissolution inhibitor include sulfonic acid esters described in detail in JP-A-10-268512 and JP-A-11-288089.
Phosphates, aromatic carboxylic esters, aromatic disulfones, carboxylic anhydrides, aromatic ketones,
Aromatic aldehydes, aromatic amines, aromatic ethers, compounds having a triarylmethane skeleton, etc., are described in detail in JP-A-11-190903,
Acid-coloring dyes having a lactone skeleton, an N, N-diarylamide skeleton, and a diarylmethylimino skeleton; bases having a lactone skeleton, a thiolactone skeleton, and a sulfolactone skeleton described in detail in JP-A-11-143076. Color-forming dyes and the like can be mentioned.

Further, as dissolution inhibitors, for example, polyethylene glycols, polyethylene glycol polypropylene glycol block copolymers, polyethylene glycol alkyl ethers, polyethylene glycol polypropylene glycol alkyl ethers, polyethylene glycol alkyl phenyl ethers, polyethylene glycol fatty acid esters , Polyethylene glycol alkyl amines, polyethylene glycol alkyl amino ethers, glycerin fatty acid esters and their polyethylene oxide adducts, sorbitan fatty acid esters and their polyethylene oxide adducts, sorbite fatty acid esters and their polyethylene oxide adducts, pentaerythritol Fatty acid esters and their polyethylene Oxide adducts, nonionic surfactants such as polyglycerol fatty acid esters.

In the present invention, the content of the dissolution inhibitor in the positive photosensitive composition is preferably 50% by weight or less, more preferably 0.01 to 30% by weight, and more preferably 0.1 to 30% by weight. It is particularly preferred that the amount is 20% by weight.

In the present invention, the positive photosensitive composition containing the photothermal conversion substance and the alkali-soluble resin preferably has a pKa of 2 for the purpose of improving developability such as imparting underdevelopability. The above organic acids and anhydrides of the organic acids may be contained.

Examples of the organic acid and its anhydride include those described in JP-A-60-88942 and JP-A-63-2760.
48, JP-A-2-96754 and the like, and specifically, glyceric acid, methylmalonic acid, dimethylmalonic acid, propylmalonic acid, succinic acid, malic acid, mesotartaric acid, Glutaric acid, β-methylglutaric acid, β, β-dimethylglutaric acid, β-ethylglutaric acid, β, β-diethylglutaric acid, β-propylglutaric acid, β, β-methylpropylglutaric acid, pimelic acid, suberin Acid, aliphatic saturated carboxylic acid such as sebacic acid, aliphatic unsaturated carboxylic acid such as maleic acid, fumaric acid, glutaconic acid, 1,1-cyclobutanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,1-cyclohexane Pentanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, 1,1-cyclohexanedicarboxylic acid, 1,
Carbocyclic saturated carboxylic acids such as 2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexenedicarboxylic acid, 2,3-dihydroxybenzoic acid, 3,
4-dimethylbenzoic acid, 3,4-dimethoxybenzoic acid,
3,5-dimethoxybenzoic acid, p-toluic acid, 2-hydroxy-p-toluic acid, 2-hydroxy-m-toluic acid, 2-hydroxy-o-toluic acid, mandelic acid, gallic acid, phthalic acid, isophthalic acid Acids, carbocyclic unsaturated carboxylic acids such as terephthalic acid, and Meldrum's acid,
Ascorbic acid, succinic anhydride, glutaric anhydride, maleic anhydride, cyclohexenedicarboxylic anhydride, cyclohexanedicarboxylic anhydride, phthalic anhydride and the like can be mentioned.

In the present invention, the content of the organic acid or its anhydride in the positive photosensitive composition is preferably at most 30% by weight, more preferably at most 20% by weight, and preferably at most 10% by weight. It is particularly preferred that:

In the present invention, the positive photosensitive composition containing the photothermal conversion substance and the alkali-soluble resin may be, for example, Victoria Pure Blue (4259).
5), crystal violet (42555), crystal violet lactone, auramine O (4100
0), Kachiron Brilliant Flavin (Basic 1)
3), Rhodamine 6 GCP (45160), Rhodamine B (45170), Safranin OK 70: 100 (50
240), Erioglaucine X (42080), Fast Black HB (26150), No. 120 / Lionol Yellow (21090), Lionol Yellow G
RO (21090), Shimla First Yellow 8G
F (21105), Benzidine Yellow 4T-564D
(21095), Shimla Fast Red 4015
(12355), Lionol Red B4401 (158)
50), Fast Gen Blue TGR-L (7416
0) and a colorant such as a pigment or a dye such as Lionol Blue SM (26150). Here, the numbers in parentheses above indicate the color index (C.I.
I. ).

In the present invention, the content of the colorant in the positive photosensitive composition is preferably 50% by weight or less, more preferably 0.5 to 30% by weight, and more preferably 2 to 20% by weight. % Is particularly preferred.

In the present invention, the positive-type photosensitive composition containing the photothermal conversion substance and the alkali-soluble resin is cross-linked with the phenol resin by post-heating after exposure and development to give a positive image with chemical resistance. For the purpose of imparting printing properties and printing durability, a crosslinking agent having an action of crosslinking the phenolic resin may be contained, and as the crosslinking agent, typically, a methylol group as a functional group,
Examples thereof include an alkoxymethyl group obtained by alcohol condensation modification thereof, and other amino compounds having at least two acetoxymethyl groups and the like. Specifically, melamine derivatives,
For example, methoxymethylated melamine [manufactured by Mitsui Cytec Co., Ltd., Cymel 300 series (1), etc.], benzoguanamine derivative [methyl / ethyl mixed alkoxylated benzoguanamine resin (manufactured by Mitsui Cytec Co., Ltd., Cymel 1100)
Series (2) etc.], glycoluril derivatives [tetramethylol glycoluril resin (manufactured by Mitsui Cytec Co., Ltd., Cymel 1100 series (3) etc.)], urea resin derivatives, resole resins and the like.

In the present invention, the content of the crosslinking agent in the positive photosensitive composition is preferably 20% by weight or less, more preferably 10% by weight or less.
It is particularly preferred that the content be 5% by weight or less.

In the present invention, the positive photosensitive composition containing the photothermal conversion substance and the alkali-soluble resin may be nonionic, anionic, or anionic for the purpose of improving sensitivity and developing property. A surfactant such as amphoteric may be contained.

Examples of the nonionic surfactant include polyethylene glycols such as polyethylene glycol and polyethylene glycol polypropylene block copolymer, polyethylene glycol cetyl ether, polyethylene glycol stearyl ether, polyethylene glycol oleyl ether, polyethylene glycol behenyl ether and the like. Polyethylene glycol polypropylene glycol alkyl ethers such as polyethylene glycol alkyl ethers, polyethylene glycol polypropylene glycol cetyl ether, polyethylene glycol polypropylene glycol decyl tetradecyl ether, polyethylene glycol octyl phenyl ether, polyethylene glycol nonyl phenyl ether Polyethylene glycol alkyl phenyl ethers such as ter, ethylene glycol monostearate, ethylene glycol distearate, diethylene glycol stearate, polyethylene glycol distearate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol such as polyethylene glycol monooleate Fatty acid esters, glyceryl monomyristate, glyceryl monostearate, glyceryl monoisostearate, glyceryl distearate, glyceryl monooleate, glyceryl dioleate and the like, and their polyethylene oxide adducts and polyglycerin fatty acid esters , Pentaerythritol monostearate, bird Stearate pentaerythritol monooleate and pentaerythritol,
Pentaerythrit fatty acid esters such as pentaerythritol trioleate, and polyethylene oxide adducts thereof, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, etc. Fatty acid esters, and their polyethylene oxide adducts, sorbitol monolaurate, sorbit tetrastearate, sorbit hexastearate, sorbit tetraoleate, and the like, and their oxidized fatty acid esters, polyethylene oxide adducts, and polyethylene glycol alkylamines , Polyethylene glycol alkyl amino ethers, castor oil polyethylene oxide adducts, lanolin with polyethylene oxide Mention may be made of things, and the like.

The anionic surfactants include:
For example, sodium laurate, sodium stearate, higher fatty acid salts such as sodium oleate, alkyl sulfonates such as sodium lauryl sulfonate,
Alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, alkylnaphthalene sulfonates such as sodium isopropylnaphthalenesulfonate, alkyldiphenylether disulfonates such as sodium alkyldiphenyletherdisulfonate,
Polyoxyethylene alkyl ether sulfonates such as sodium polyoxyethylene lauryl ether sulfonate, alkyl sulfates such as sodium lauryl sulfate and sodium stearyl sulfate, sodium octyl alcohol sulfate, sodium lauryl alcohol sulfate, ammonium lauryl alcohol sulfate Higher alcohol sulfates such as sodium acetyl alcohol sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene lauryl ether ammonium sulfate, polyoxyethylene lauryl ether triethanolamine sulfate and the like. Ethylene alkyl ether sulfates, polyoxyethylene nonylphenyl Polyoxyethylene alkyl phenyl ether sulfates such as sodium tere sulfate, alkyl phosphate salts such as sodium lauryl phosphate and sodium stearyl phosphate, and polyoxyethylene alkyl ethers such as sodium polyoxyethylene lauryl ether and sodium polyoxyethylene stearyl ether phosphate. Phosphates, polyoxyethylene alkyl phenyl ether phosphates such as sodium polyoxyethylene nonyl phenyl ether phosphate, sulfosuccinic acids, unsaturated fatty acid sulfated oils, taurine salts, castor oil sulfate salts and the like can be mentioned.

Examples of the amphoteric surfactant include N-lauryl-N, N-dimethyl-N-carboxymethylammonium, N-stearyl-N, N-dimethyl-N-carboxymethylammonium and N-lauryl. Betaine-type compounds such as -N, N-dihydroxyethyl-N-carboxymethylammonium, N-lauryl-N, N, N-tris (carboxymethyl) ammonium, 2-alkyl-N-carboxymethyl-N-hydroxyethyl Examples include imidazolium salts such as imidazolium, imidazolines such as imidazoline-N-sodium ethylsulfonate, imidazoline-N-sodium ethylsulfate, aminocarboxylic acids, and aminosulfates.

In the present invention, the content of the surfactant in the positive photosensitive composition is preferably 0.001 to 5% by weight, more preferably 0.002 to 3% by weight. It is particularly preferred that the content is 0.005 to 1% by weight.

In the present invention, in addition to the above-mentioned components, the positive type photosensitive composition may further comprise, for example, a dye, a pigment, a coating improver, an adhesion improver, a sensitivity improver, a sensitizer, a developing agent. Various additives usually used in the photosensitive composition such as an improving agent may be further contained in a range of 20% by weight or less, preferably 10% by weight or less.

In general, when the positive photosensitive composition does not contain a compound having sensitivity to light in the ultraviolet region, the sensitivity and the contrast between the image area and the non-image area tend to be poor. Therefore, the positive photosensitive composition of the present invention does not include a compound having sensitivity to light in the ultraviolet region, such as an onium salt, a diazonium salt, and a compound containing a quinonediazide group. It is preferable that the compound has no sensitivity, since the effect of the present invention in terms of the sensitivity and the contrast between the image portion and the non-image portion can be more remarkably exhibited. Here, the term "substantially insensitive to light in the ultraviolet region" means that there is no substantially significant difference in solubility in an alkali developer before and after irradiation with light having a wavelength of 360 to 450 nm. Means that it has no image forming ability in a practical sense.

The positive type image forming material of the present invention is usually coated on a support surface as a coating solution obtained by dissolving or dispersing each of the above-mentioned components in an appropriate solvent, and then heated and dried to form a coating on the support surface. In the present invention, a lithographic printing plate is particularly preferred as the positive-type image forming material having the positive-type photosensitive composition layer formed thereon.

Here, the support may be a metal plate of aluminum, zinc, copper, steel, etc., aluminum, zinc,
Metal plates, paper, paper coated with resin, paper coated with metal foil such as aluminum, plastic films, plastic films subjected to hydrophilization, glass plates, etc. plated or deposited with copper, iron, chromium, nickel, etc. No. Among them, an aluminum plate is preferable, and surface treatment such as graining treatment by electrolytic etching or brush polishing in a hydrochloric acid or nitric acid solution, anodizing treatment in a sulfuric acid solution, and, if necessary, sealing treatment is performed. A coated aluminum plate is more preferred. The surface roughness of the support is JIS
The average roughness R _a as defined in B0601, usually 0.3
It is 1.0 μm, preferably about 0.4 to 0.8 μm.

The solvent is not particularly limited as long as it has sufficient solubility for the components used and gives good coating properties. Examples of the solvent include methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, and the like. Cellosolve solvents such as ethyl cellosolve acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol dimethyl ether, etc. Propylene glycol solvent, butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate,
Ester solvents such as ethyl pyruvate, ethyl-2-hydroxybutyrate, ethyl acetoacetate, methyl lactate, ethyl lactate, and methyl 3-methoxypropionate; and alcohol solvents such as heptanol, hexanol, diacetone alcohol, and furfuryl alcohol. , Cyclohexanone, ketone solvents such as methyl amyl ketone,
Highly polar solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone and the like, or a mixed solvent thereof, and further a mixture thereof with an aromatic hydrocarbon may be used. The usage ratio of the solvent is usually in the range of about 1 to 20 times by weight based on the total amount of the photosensitive composition.

As the coating method, conventionally known methods, for example, spin coating, wire bar coating, dip coating, air knife coating, roll coating, blade coating, curtain coating and the like can be used. The coating amount varies depending on the application, but is usually 0.3 to 7 μm as a dry film thickness.
m, preferably 0.5-5 μm, particularly preferably 1-3
μm range. The drying temperature at that time is, for example, about 60 to 170 ° C, preferably 70 to 150 ° C.
The drying time is about 5 seconds to 10 minutes, preferably about 10 seconds to 5 minutes.

In the method of forming a positive image of the present invention, the positive image forming material having the layer of the positive photosensitive composition on the surface of a support is image-exposed and then developed with an alkali developing solution to form a positive image. Forming.

Here, the light source for imagewise exposing the positive photosensitive composition layer is mainly a HeNe laser,
A laser light source such as an argon ion laser, a YAG laser, a HeCd laser, a semiconductor laser, and a ruby laser may be used. In particular, when an image is formed by absorbing light and generating heat, a wavelength range of 650 to 1,30 is used.
A light source that emits near-infrared laser light in a range of 0 nm is preferable, and examples thereof include a solid-state laser such as a ruby laser, a YAG laser, a semiconductor laser, and an LED. Is preferred. Usually, after scanning exposure by these light sources, an image is formed by developing with an alkali developing solution.

The laser light source usually scans the surface of the photosensitive composition layer as a high-intensity light beam (beam) condensed by a lens, and the sensitivity of the photosensitive composition layer according to the present invention is responsive thereto. The characteristic (mJ / cm ² ) may depend on the light intensity (mJ / s · cm ² ) of the received laser beam. Here, the light intensity of the laser beam is obtained by dividing the amount of energy per unit time (mJ / s) of the laser beam measured by the optical power meter by the irradiation area (cm ² ) of the laser beam on the surface of the photosensitive composition layer. Can be obtained by The irradiation area of the laser beam is usually defined as the area of a portion exceeding 1 / e ² intensity of the laser peak intensity, but it can be simply measured by exposing a photosensitive composition exhibiting a reciprocity law. .

In the present invention, the light intensity of the light source is
It is preferably at least 2.0 × 10 ⁶ mJ / s · cm ^2, more preferably at least 1.0 × 10 ⁷ mJ / s · cm ² . When the light intensity is in the above range, the sensitivity characteristics of the positive photosensitive composition layer in the present invention can be improved, and the scanning exposure time can be shortened, which is a great advantage practically.

Examples of the developing solution used for developing the positive type photoreceptor obtained by imagewise exposing the positive type image forming material of the present invention include sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium metasilicate and potassium metasilicate. , Sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, dibasic sodium phosphate, tertiary sodium phosphate, dibasic ammonium phosphate, ammonium tertiary phosphate, sodium borate, potassium borate, boric acid Inorganic alkali salts such as ammonium, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, monobutylamine, monoethanolamine, diethanolamine, triethanolamine Ethanolamine, mono-isopropanolamine, an alkali developer comprising an aqueous solution of about 0.1 to 5% by weight of an organic amine compound diisopropanolamine used. Among them, alkali metal silicates such as sodium silicate and potassium silicate which are inorganic alkali salts are preferable. In the developer, the same nonionic surfactants, anionic surfactants, and amphoteric surfactants as those described as the surfactant component of the photosensitive composition are used in terms of, for example, stably expanding the range of development conditions. A surfactant such as a surfactant or an organic solvent such as alcohol can be added.

The development is usually performed by immersion development, spray development, brush development, ultrasonic development, or the like.
It is carried out at a temperature of about 50 to about 50C, particularly preferably about 15 to 45C.

[0087]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

Example 1 An aluminum plate (0.24 mm thick) was degreased in a 5% by weight aqueous sodium hydroxide solution at 60 ° C. for 1 minute, and then a 0.5 mol / liter aqueous hydrochloric acid solution was used. In, at a temperature of 28 ° C., a current density of 60 A / dm ² , and a processing time of 4
Electrolytic etching was performed under the condition of 0 second. Next, after a desmut treatment at 60 ° C. for 12 seconds in a 4% by weight aqueous sodium hydroxide solution, a 20% by weight sulfuric acid solution at a temperature of 20 ° C., a current density of 3.5 A / dm ² and a treatment time of 1 minute. For anodizing treatment. In addition, 2
Hot water sealing treatment was performed for 0 second to produce an aluminum plate for a lithographic printing plate support. Surface roughness meter (Kosaka Laboratory,
The average roughness Ra value of this plate according to “SE-3DH”) was 0.60 μm.

On the surface of the obtained aluminum plate support, 4 parts by weight of the cyanine dye shown in the above specific example (II-9) as a photothermal conversion substance, and phenol / o-cresol / m-cresol as an alkali-soluble resin / mixing ratio of p- cresol was measured by novolak resin a (gel permeation chromatography from polycondensate to remove low molecular weight components of the mixed phenols and formaldehyde 22/22/34/22 in molar ratio M _W 16,0
00, content of molecules having a molecular weight of 2,000 or less 51.0% by weight, content of molecules having a molecular weight of 10,000 or more 22.3
Wt%) 70 parts by weight, and, M _W 3,400 mixing ratio of phenol / o-cresol was measured by novolak resin B (ibid consisting polycondensate of mixed phenols and formaldehyde 50/50 molar ratio , Molecular weight 2,
71.0% by weight of molecules having a molecular weight of not more than 000,
30% by weight of a content of 0,000 or more molecules 0% by weight)
As a dissolution inhibitor, a polyethylene oxide adduct of sorbite tetraoleate (“GO” manufactured by Nikko Chemicals Co., Ltd.)
-4 ") 4 parts by weight, 1,2-cyclohexenedicarboxylic acid 8 parts by weight as an organic acid, crystal violet lactone 10 parts by weight as a colorant, methoxymethylated melamine as a cross-linking agent (" Cymel C-3 manufactured by Mitsui Cytec Co., Ltd. "
00 ") 1 part by weight, 800 parts by weight of methyl cellosolve,
A coating solution prepared by adding to 200 parts by weight of ethyl cellosolve and stirring at room temperature to prepare a solution was applied using a wire bar,
And then heat-treated at 60 ° C. and 40% RH for 24 hours to obtain a coating amount of 2.5 g / m 2.
A positive photosensitive lithographic printing plate having the positive photosensitive composition layer of No. ² was prepared.

Here, as shown in the following Table 1, the proportion of o-cresol in the phenol component constituting a molecule having a molecular weight of 2,000 or less in the mixture of novolak resin A and novolak resin B was 32.5 mol. %, And the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 10,000 or more is 21.8 mol%.

With respect to the obtained positive photosensitive lithographic printing plate,
An exposure apparatus using a 830 nm semiconductor laser as a light source (“Trend Setter 3244, manufactured by Creo Corporation”).
T "), image exposure was performed at an exposure energy of 113 mJ / cm ² , and then development processing was performed at 28 ° C. using the following developer to produce a lithographic printing plate.

Developer 21 parts by weight of potassium silicate, 3.1 parts by weight of potassium hydroxide, and 0.2 parts by weight of polyethylene oxide adduct of alkyl ether phosphate (“NIKKOL DLP10” manufactured by Nikko Chemicals Co., Ltd.) as an anionic surfactant Parts and 0.07 parts by weight of oleic acid highly sulfated oil ("Pionin A15" manufactured by Takemoto Yushi Co., Ltd.) and a betaine-type compound ("Amogen K" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an amphoteric surfactant 0 An alkaline developer obtained by dissolving 3 parts by weight in 76 parts by weight of demineralized water.

At this time, the exposed portion (non-image portion) and the non-exposed portion
(Reflection densitometer)
("RD-514" manufactured by Macbeth)
By calculating the remaining film ratio based on the following formula, the exposure
Time when the residual film ratio of the part reaches 0% [T₁(Seconds)]
And the developing time at which the residual film ratio of the unexposed area can maintain 90% [T
_Two(Sec)], and the obtained lithographic printing
After immersing the plate in Ultra Plate Cleaner for 10 minutes
The percentage of remaining film (%) was measured to evaluate the chemical resistance.
The results are shown in Table 1.

Remaining film ratio (%) = [(reflection density of exposed or unexposed area after development−reflection density of support surface) / (reflection density of plate surface before development−reflection density of support surface)] × 100

Comparative Example 1 As the alkali-soluble resin in the positive photosensitive composition, 70 parts by weight of the same novolak resin A as in Example 1 and a mixed phenol having a mixing ratio of phenol / o-cresol of 20/80 in molar ratio were used. polycondensate M _W 2,200 as measured by novolak resin C (ibid consisting, content 80 wt% of a molecular weight of 2,000 or less molecular, content 0 weight molecular weight of 10,000 or more molecules of the class and formaldehyde %) Except that 30 parts by weight were used, a positive photosensitive lithographic printing plate was prepared in the same manner as in Example 1, and the developability and the chemical resistance were evaluated. The results are shown in Table 1 below. .

Here, as shown in the following Table 1, the proportion of o-cresol in the mixture of novolak resin A and novolak resin C in the phenol component constituting the molecule having a molecular weight of 2,000 or less was 45.2 mol. %, And the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 10,000 or more is 21.8 mol%.

Comparative Example 2 As an alkali-soluble resin in a positive photosensitive composition
Phenol / o-cresol / m-cresol / p
-The mixing ratio of cresol is 22/22/34 /
Polycondensation of 22 mixed phenols with formaldehyde
Novolak resin D (gel permeation
M measured by chromatography_W15,000, min
Content of molecules having a molecular weight of 2,000 or less, 61.0% by weight,
Content of molecules having a molecular weight of 10,000 or more 14.1% by weight)
80 parts by weight, and phenol and formaldehyde
Novolak resin E consisting of a polycondensate (measured as described above)
M _W8,200, containing molecules with molecular weight of 2,000 or less
% Of molecules having a molecular weight of 10,000 or more.
Example 1 except that 20 parts by weight were used.
Produce a positive photosensitive lithographic printing plate in the same manner as in
Then, the developability and the chemical resistance were evaluated, and the results are shown in Table 1 below.
did.

Here, as shown in the following Table 1, the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 2,000 or less in the mixture of novolak resin D and novolak resin E was 17.4 mol. %, And the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 10,000 or more is 19.4 mol%.

[0099]

[Table 1]

[0100]

According to the present invention, in a positive-type image forming material in which a layer of a positive-type photosensitive composition comprising a light-to-heat conversion material and an alkali-soluble resin is formed on a support-resistant surface, light in the near infrared region is obtained. Positive image forming material having high sensitivity to the image, excellent contrast between the image area and the non-image area, and thus having a wide range of developing conditions and excellent chemical resistance, and a positive image forming material using the same. An image forming method can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H025 AA01 AA04 AB03 AC08 AD03 CB29 CB56 CC11 FA10 FA17 2H096 AA06 BA20 EA04 EA23 GA08 2H114 AA04 AA22 AA24 BA01 BA10 DA59 DA64 EA01 EA02 FA06 FA10 FA16

Claims (8)

[Claims] 1. A positive image forming material comprising a support having thereon a layer of a positive photosensitive composition containing a photothermal conversion material that absorbs light from an image exposure light source and converts it into heat, and an alkali soluble resin. Wherein the alkali-soluble resin has a ratio of o-cresol of 25 to 40 mol% in a phenol component constituting a molecule having a molecular weight of 2,000 or less,
A positive type image forming material characterized by containing a phenol resin in which the ratio of o-cresol to the phenol component constituting the molecule having a molecular weight of 10,000 or more is 25 mol% or less. 2. The phenolic resin has a content of molecules having a molecular weight of 2,000 or less of 45 to 75% by weight and a molecular weight of 1
2. The positive image forming material according to claim 1, wherein the content of the molecule having a molecular weight of 000 or more is 5 to 25% by weight. 3. The positive image forming material according to claim 1, wherein the alkali-soluble resin is a phenol resin. 4. The positive image forming material according to claim 1, wherein the phenol resin is a novolak resin. 5. The light-to-heat conversion material has a wavelength range of 650 to 1,3.
The positive image-forming material according to any one of claims 1 to 4, which is a light-absorbing dye having a near-infrared absorbing ability of 00 nm. 6. The positive image forming material according to claim 5, wherein the light absorbing dye is a cyanine dye having a basic structure in which a heterocyclic ring is bonded via a polymethine chain. 7. The positive image forming material according to claim 1, wherein the image forming material is a photosensitive lithographic printing plate. 8. The positive image forming material according to claim 1, which is scanned and exposed with a laser beam having a wavelength range of 650 to 1,300 nm, and then developed with an alkali developing solution. Positive image forming method.