JP2002189294A - Positive image forming material - Google Patents

Abstract

(57) [Problem] To provide a plate making method of a positive photosensitive lithographic printing plate having a large developing latitude and excellent processing stability. SOLUTION: In an image forming material having a positive photosensitive composition layer containing (A) a photothermal conversion substance and (B) an alkali-soluble resin on a support, the alkali-soluble resin is a novolak resin and / or a phenol resin. Containing
A positive-working image-forming material, wherein an alkali-soluble resin component having a weight average molecular weight of 2,000 or less accounts for 55% by weight or less of the whole alkali-soluble resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel positive type image forming material and an image forming method. For more details, see 8
The present invention relates to a positive image forming material and an image forming method which are exposed to laser light in a wavelength range of from 00 to 1100 nm and are suitable for direct plate making.

[0002]

2. Description of the Related Art With the advance of computer image processing technology, a photosensitive or heat-sensitive direct plate making in which a resist image is directly formed by a laser beam or a thermal head without outputting digital image information to a silver halide mask film. The system is drawing attention. In particular, realization of a high-resolution laser-sensitive direct plate making system using a high-output semiconductor laser or YAG laser has been strongly desired in view of miniaturization, environmental light during plate making work, and plate material cost.

Among printing plates for laser-sensitive direct plate making, recently, a method of forming a positive image by using an infrared laser and increasing the solubility of an exposed portion in a developing solution mainly by a change other than a chemical change has attracted attention. For example, JP-A-10-268512, JP-A-11-194504, and JP-A-11-2239
No. 36, JP-A-11-84657, JP-A-1
1-1174681, WO97 / 39894, WO
98/42507 and the like. Conventional positive-type photosensitive lithographic printing plates typically increase the solubility in a developing solution by photodecomposition of an o-quinonediazide compound, that is, by a chemical change, and use this for image formation. The positive-type photosensitive lithographic printing plate described in the literature has a main photosensitive layer component containing a substance that absorbs infrared light such as an infrared absorbing dye and converts it into heat and an alkali-soluble resin such as a novolak resin. The heat generated by the external laser light exposure causes a physical change such as a conformational change of the resin to increase the solubility in a developing solution.

[0004] Positive-type photosensitive lithographic printing plates utilizing the increase in solubility due to non-chemical changes do not require substances sensitive to white light such as o-quinonediazide compounds. It has the advantage that it can be done. However, such a printing plate has a printing durability, a sensitivity, and a development latitude (a time until the exposed portion is completely removed during development, since the photosensitive layer component does not substantially undergo a chemical change upon exposure, It is difficult to satisfy all of the basic performances of the printing plate, such as the difference in the time during which the residual film ratio of the unexposed portion is sufficiently ensured during the development. In particular, when image exposure is performed with a high exposure energy in order to widen the development latitude, excessive heat is generated by the photothermal conversion material in the photosensitive layer, and the heat causes the photosensitive layer to scatter (ablate).
There has been a problem that the optical system of the exposure apparatus is contaminated.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming material such as a photosensitive lithographic printing plate in which the photosensitive layer is less scattered during exposure. Another object of the present invention is to provide an image forming material having a wide development latitude.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that scattering of the photosensitive layer at the time of exposure can be reduced by controlling the molecular weight of the resin of the photosensitive layer, and reached the present invention. Note that controlling the molecular weight of the novolak resin in the photosensitive composition is described in, for example, JP-A-6-308.
No. 722, Japanese Unexamined Patent Publication No. 4-122938, etc., all of which are related to a photoresist for ultraviolet irradiation used for an integrated circuit or the like, and have properties and performance as an image forming material such as a printing plate. No composition is disclosed for irradiation with near-infrared light.

That is, the gist of the present invention resides in that
In an image forming material having a positive photosensitive composition layer containing (A) a photothermal conversion substance and (B) an alkali-soluble resin, the alkali-soluble resin contains a novolak resin and / or a phenol resin, and has a weight average molecular weight of 2,000. The positive-working image forming material is characterized in that the following alkali-soluble resin component accounts for 55% by weight or less of the whole alkali-soluble resin. Another gist of the present invention resides in an image forming method, which comprises exposing the above-mentioned positive image forming material to near-infrared laser light having a wavelength of 800 to 1100 nm, followed by developing with an alkali developing solution. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The image-forming material of the present invention contains (A) a photothermal conversion substance and (B) an alkali-soluble resin as essential components on a support, and further comprises a dissolution inhibitor and a heat-crosslinkable compound. And an image forming material having a positive photosensitive composition layer containing, as necessary, other additives.

As the support on which the photosensitive composition layer used in the present invention is provided, a metal plate such as aluminum, zinc, steel or copper, or chromium, zinc, copper, nickel, aluminum or iron is plated or deposited. Metal sheet, paper, plastic film and glass plate, paper coated with resin, paper covered with metal foil such as aluminum, sheet such as plastic film subjected to hydrophilic treatment, and the like. Of these, an aluminum plate is preferred when a photosensitive lithographic printing plate is manufactured as an image forming material. The support of the photosensitive lithographic printing plate is subjected to surface treatment such as graining by electrolytic etching or brush polishing in a hydrochloric acid or nitric acid solution, anodic oxidation in a sulfuric acid solvent, and sealing if necessary. It is more preferable to use an aluminum plate that has been used.

[0010] The surface roughness of a support is generally indicated by the value of surface roughness Ra. This can be measured using a surface roughness meter. The support used in the present invention has an average roughness Ra of 0.3 to 1.
0 μm aluminum plate is preferable,
0.8 μm is more preferable. This support can be used after further performing a surface treatment with an organic acid compound, if necessary.

The (A) “photothermal conversion material” which is the first component used in the positive photosensitive composition used in the present invention will be described. The photothermal conversion material is not particularly limited as long as it is a compound that can convert absorbed light into heat.
Among organic or inorganic pigments and dyes, organic dyes, metals, metal oxides, metal carbides, metal borides, etc., having an absorption band in part or all of the near infrared region of a wavelength range of 800 to 1100 nm, 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.

These light absorbing dyes include a nitrogen atom,
Representative examples include so-called cyanine dyes in a broad sense, in which a heterocyclic ring containing an oxygen atom or a sulfur atom or the like is bonded by polymethine (-CH =) n, and specifically, for example, quinoline ( So-called cyanine-based in a narrow sense, indole-based (so-called indocyanine-based), benzothiazole-based (so-called thiocyanine-based), oxazole-based (so-called oxacyanine-based), aminobenzene-based (so-called polymethine-based), pyrylium-based , Thiapyrylium, squarylium, croconium, azurenium, aminium, immonium, phthalocyanine, anthraquinone, etc., among which quinoline, indole, benzothiazole, aminobenzene, pyrylium,
Alternatively, a thiapyrylium-based, aminium-based, or immonium-based dye is preferable.

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

[0014]

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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. L1 represents a tri, penta, or heptamethine group which may have a substituent, and two substituents on the penta or heptamethine group are connected to each other to have 5 to 7 carbon atoms. The cycloalkene ring 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- represents a counter anion. ] Here, as the substituent in formula (Ia), R ¹ and R ² in (Ib), and (Ic), an 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, an amino group, and a halogen atom. Examples of the substituent in the quinoline ring include an alkyl group, an alkoxy group, a nitro group, and a halogen atom.

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

[0017]

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[In the formula (II), Y ¹ and Y ² are each independently
Represents a dialkylmethylene group, a sulfur atom or an oxygen atom,
R ³ and R ⁴ are each independently an alkyl group optionally having a substituent, an alkenyl group optionally having a substituent,
An alkynyl group which may have a substituent, or a phenyl group which may have a substituent; L ² represents a 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 condensed benzene ring may have a substituent, in which case May be linked to each other to form a fused benzene ring. X ^- is a counter anion. Here, examples of the substituent for R ³ and R ⁴ in the formula (II) include an alkoxy group, a phenoxy group, a hydroxy group, and a phenyl group. Examples of the substituent for L ² include an alkyl group and an amino group. And a substituent on the benzene ring, such as an alkyl group, an alkoxy group, a nitro group, or a halogen atom.

As the aminobenzene-based dye, those represented by the following general formula (III) are particularly preferred.

[0020]

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[In the formula (III), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent an alkyl group, and R 9 and R 10 each independently represent a substituent. A good aryl group, a furyl group, or a thienyl group; L ³ represents a mono-, tri-, or pentamethine group which may have a substituent, and two substituents on the tri- or pentamethine group are linked to each other; May form a cycloalkene ring having 5 to 7 carbon atoms, and the quinone ring and the benzene ring may have a substituent. X ^- is a counter anion. Here, specifically, as R ⁹ and R ¹⁰ in the formula (III),
A phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-furyl group, a 3-furyl group, a 2-thienyl group, a 3-thienyl group, and the like. Examples of such substituents include an alkyl group, an alkoxy group, dialkylamino group, hydroxy group, or a halogen atom, and examples of the substituent in L ^3, alkyl group, amino group, or a halogen atom, and examples of the substituent in the quinone ring and the benzene ring, an alkyl group , An alkoxy group, a nitro group, or a halogen atom.

Further, as the pyrylium-based and thiapyrylium-based dyes, the following general formulas (IVa), (IVb), and
Those represented by (IVc) are preferred.

[0023]

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In the formulas (IVa), (IVa) and (IVc), Y ³
And Y ⁴ each independently represent an oxygen atom or a sulfur atom, and R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ each independently represent a hydrogen atom or an alkyl group, or R ¹¹ and R ¹³ , and R ¹² and R
¹⁴ may be linked to each other to form a cycloalkene ring having 5 or 6 carbon atoms, and L ⁴ represents a mono, tri, or pentamethine group which may have a substituent, and the tri or pentamethine group The above two substituents may be connected 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. Two substituents may be linked to each other to form a fused benzene ring. X- represents a counter anion. Here, examples of the substituent in L ⁴ of formulas (IVa), (IVa), and (IVc) include an alkyl group, an amino group, and a halogen atom, and examples of the substituent in the pyrylium ring and the thiapyrylium ring include And an aryl group such as a phenyl group and a naphthyl group.

Further, as the aminium-based and immonium-based dyes, those having at least one N, N-diaryliminium salt skeleton are preferable.
Those represented by (Va) or (Vb) are preferred.

[0026]

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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. In addition, the electronic bond (─) in the formula (Vb) indicates a resonance state with another electronic bond. Here, as the substituents on the quinone ring and the benzene ring in the formulas (Va) and (Vb), an alkyl group, an alkoxy group,
Examples include an acyl group, a nitro group, and a halogen atom.

The above-mentioned general formulas (Ia to c), (II), (III),
Examples of the counter anion X ⁻ in (IVa to c) and (Va to b) include, for example, Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , PF ₆ ⁻ ,
And, BF ₄ ^- inorganic acid anion, benzenesulfonic acid inorganic borate such as, p- toluenesulfonic acid, naphthalenesulfonic acid, acetic acid, and methyl, ethyl, propyl, butyl, phenyl, methoxyphenyl, naphthyl, difluorophenyl And organic acid anions such as organic boric acid having an organic group such as pentafluorophenyl, thienyl and pyrrolyl.

As described above, the quinoline-based dyes represented by the general formulas (Ia to c), the indole-based or benzothiazole-based dyes represented by the general formula (II), and the amino groups represented by the general formula (III) Benzene-based dyes, pyrylium-based or thiapyrylium-based dyes represented by the general formulas (IVa to c), and aminium- or immonium-based dyes represented by the general formulas (Va to b) are excellent in sensitivity. I have. Specific examples of the photothermal conversion material preferably used are shown below.

[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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[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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The content ratio of these photothermal conversion materials in the positive photosensitive composition of the present invention is usually 0.5% by weight.
~ 30%, preferably 1-20%, more preferably 2 ~
10%, especially 3-10%. In particular, in combination with the surfactant described below, the content of the light-to-heat conversion substance can be relatively increased, and as a result, sensitivity and development latitude are particularly improved, which is preferable.

Next, the second component (B) “alkali-soluble resin” used in the positive photosensitive composition of the present invention.
(Hereinafter, may be referred to as a polymer or a resin) will be described. The alkali-soluble resin is basically composed of a combination of the component (A) and the photothermal conversion substance, wherein the exposed portion and the unexposed portion are mainly changed by a change other than a chemical change.
It is a polymer that can cause a difference in solubility in an alkali developing solution, and naturally includes the case where the polymer itself is a polymer compound whose solubility in an alkali developing solution is changed mainly by a change other than a chemical change. Examples of such a polymer include a novolak resin, a resol resin, a polyvinylphenol resin, an alkali-soluble resin such as a copolymer of an acrylic acid derivative, and the like. Among these, it is preferable to include a novolak resin and / or a phenol resin. preferable.

As the novolak resin, phenol, m
-Cresol, o-cresol, p-cresol, 2,
5-xylenol, 3,5-xylenol, resorcinol, pyrogallol, bisphenol, bisphenol-
A, at least one kind of aromatic hydrocarbons such as trisphenol, o-ethylphenol, m-ethylphenol, p-ethylphenol, propylphenol, n-butylphenol, t-butylphenol, 1-naphthol and 2-naphthol; Polycondensation with aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde and furfural and at least one aldehyde or ketone selected from ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone under an acidic catalyst Is mentioned.

Instead of formaldehyde and acetaldehyde, paraformaldehyde and paraaldehyde, respectively, may be used. Weight average molecular weight in terms of polystyrene by gel permeation chromatography (hereinafter abbreviated as GPC) measurement of the novolak resin (hereinafter, the weight average molecular weight as measured by GPC is abbreviated as Mw).
Is preferably 1,000 or more, more preferably 1.5
Those having a molecular weight of 00 or more, preferably 15,000 or less, more preferably 10,000 or less are used.

The aromatic hydrocarbons of the novolak resin are more preferably phenol, o-cresol, m
-Cresol, p-cresol, 2,5-xylenol, and 3,5-xylenol, at least one phenol selected from resorcinol, formaldehyde,
Novolak resins polycondensed with at least one selected from aldehydes such as acetaldehyde and propionaldehyde are exemplified.

Among them, the mixing ratio of m-cresol: p-cresol: 2,5-xylenol: 3,5-xylenol: resorcin was 40 to 100: 0 to 5 in molar ratio.
Phenols of 0: 0 to 20: 0 to 20: 0 to 20 or phenols and aldehydes having a molar ratio of phenol: m-cresol: p-cresol of 1 to 100: 0 to 70: 0 to 60 Novolak resins which are polycondensates with the compounds are preferred. Of the aldehydes, formaldehyde is particularly preferred. As described later, the photosensitive composition of the present invention may further contain a dissolution inhibitor. In this case, m-cresol: p-cresol: 2,5-xylenol: 3,5-xylenol: resorcinol Are mixed in a molar ratio of 70 to 100: 0 to 30: 0 to 20: 0.
Phenols or phenol: m-cresol: p-cresol in a molar ratio of 10 to 10
Novolak resins, which are polycondensates of phenols and aldehydes at 0: 0 to 60: 0 to 40, are preferred.

As the phenol resin, at least one kind selected from aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde and furfural and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone in the presence of phenol in the presence of an acidic catalyst. And those polycondensed with aldehydes or ketones.

Instead of formaldehyde and acetaldehyde, paraformaldehyde and paraaldehyde, respectively, may be used. Weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (hereinafter abbreviated as GPC) of phenolic resin (hereinafter, weight average molecular weight measured by GPC is abbreviated as Mw)
Is preferably 1,000 or more, more preferably 1.5
Those having a molecular weight of 00 or more, preferably 15,000 or less, more preferably 10,000 or less are used.

Examples of the resin other than the novolak resin include an alkali-soluble resin described in JP-A-2000-105454. These resins may be used alone or as a mixture.

The alkali-soluble resin used in the present invention is an alkali-soluble resin having a molecular weight of 2000 or less (hereinafter, referred to as an alkali-soluble resin).
The weight ratio of the low-molecular-weight resin component is 55% or less based on the whole alkali-soluble resin. The weight ratio of the low molecular weight resin component is preferably 50% or less, more preferably 45% or less. If it is 55% or more,
The amount of ablation during exposure increases. The weight ratio of the low molecular weight resin component is preferably 10% or more,
It is more preferably at least 5%, particularly preferably at least 20%.
If it is significantly smaller than the above range, the sensitivity tends to decrease.

In a preferred embodiment of the present invention, a novolak resin and / or a phenol resin containing relatively few low molecular weight components are used as a main component so that the weight ratio of the low molecular weight components is 55% or less. The case where a novolak resin and / or a phenol resin is mainly used as a component of the alkali-soluble resin is preferable in terms of sensitivity and development latitude. The proportion of the novolak resin in the alkali-soluble resin is preferably 40 to 100%, more preferably 50 to 90%, and particularly preferably 60 to 80%. The ratio of the phenol resin in the alkali-soluble resin is 0 to 60.
%, Preferably 10 to 50%, and 20 to 40%
Is particularly preferred. The total amount of the novolak resin and the phenol resin is 40 to 100 in the alkali-soluble resin.
% Is preferable, 60 to 100% is more preferable, and 80 to
100% is particularly preferred.

As a method of reducing the low molecular weight resin component of the novolak resin, the low molecular weight resin component is generally separated from the low molecular weight resin component by using various methods, utilizing the fact that the low molecular weight resin component has higher solubility in an organic solvent. It is possible.
For example, dissolving the novolak resin in a two-layer solvent of a ketone-based solvent and a hydrocarbon-based solvent that are not completely mixed with each other,
There is a method of reducing the low molecular weight resin component by separating and obtaining a novolak resin dissolved in a ketone solvent. As the ketone solvent, acetone or methyl ethyl ketone is preferable. As the hydrocarbon solvent, a saturated aliphatic hydrocarbon having 5 to 8 carbon atoms is preferable.
The novolak resin thus obtained preferably has a low molecular weight resin component of 10 to 50% of the novolak resin.
It is.

The content of these alkali-soluble resins in the positive photosensitive composition is preferably 50% by weight.
To 99%, more preferably 60% to 99%, particularly preferably 70 to 98%.

The photosensitive composition layer of the present invention may contain a dissolution inhibitor having a property of reducing the solubility of the photosensitive composition in an alkali developing solution. Examples of the dissolution inhibitor used in the present invention include JP-A-10-2684.
12, sulfonic acid esters, phosphoric acid esters, aromatic carboxylic acid esters, aromatic disulfones, carboxylic acid anhydrides described in JP-A-11-288089, and the like.
Examples thereof include aromatic ketones, aromatic aldehydes, aromatic amines and aromatic ether compounds, and compounds having a triarylmethane skeleton. Also, JP-A-11-1
Lactone skeleton, N, N-diarylamide skeleton, acid-color-forming dye having diarylmethylimino skeleton, lactone skeleton, thiolactone skeleton described in JP-A-90903 and the like.
Base coloring dyes having a sulfolactone skeleton can also be mentioned.

The photosensitive layer of the present invention may contain a compound capable of crosslinking an alkali-soluble resin by the action of heat (hereinafter, may be abbreviated as a thermally crosslinkable compound). When a heat-crosslinking compound is contained in the photosensitive layer, the alkali-soluble resin can be crosslinked by performing post-heating treatment after exposure, and as a result, it is possible to improve chemical resistance and printing durability. it can. As such a thermally crosslinkable compound, a compound which can crosslink an alkali-soluble resin by heating to 150 ° C to 300 ° C is usually mentioned.

Examples of the thermally crosslinkable compound include a nitrogen-containing compound having thermal crosslinkability, preferably a compound containing an amino group, and more specifically, for example, a methylol group as a functional group and an alcohol thereof. Examples thereof include condensation-modified alkoxymethyl groups, and other amino compounds having at least two acetoxymethyl groups. Among the compounds having an amino group, the compound preferably has a heterocyclic structure, particularly a nitrogen-containing heterocyclic structure, and more preferably a compound having a melamine skeleton. Specifically, for example, as such a thermally crosslinkable compound, a thermally crosslinkable compound described in JP-A-11-202481 and the like can be mentioned.

The photosensitive composition of the present invention may contain various additives such as dyes, pigments,
It may also contain a coating improver, a development improver, an adhesion improver, a sensitivity improver, a sensitizer, and the like. It is also possible that the cause of color formation includes an ionic dye due to non-polarization of a cation or an anion.Specifically, a cyanine dye, an azurenium dye, a squarium dye, a croconium dye, a diphenylmethane dye, a triphenylmethane dye, Oxazine dyes, azine dyes, pyrylium dyes,
And thiopyrium dyes, viologen dyes, xanthene dyes, rhodocyanine dyes, styryl dyes, and the like. It should be noted that such ionic dyes are distinguished from dyes that can be used as a light-to-heat conversion material, and are dyes having an absorption maximum (λmax) of 700 nm or less. Of these, preferred are triphenylmethane dyes having a triphenylmethyl group as a partial structure in the structure thereof. I. No. When represented by C. I.
BasicViolt3, C.I. I. BasicBlue
5, C.I. I. Basic Green 1, C.I. I. Bas
icBlue 26, C.I. I. AcidBlue1, C.I.
I. solventBlue2, C.I. I. BasicB
lue7 and the like; Crystal Violet manufactured by Tokyo Kasei Co., Ltd .; Primocyanin manufactured by Sumitomo Chemical Co., Ltd.
eBxconc. AizenDi manufactured by Hodogaya Chemical Co., Ltd.
amondGreenGH, Aizen Victory
aBlueBH, AizenBrilliantAci
dPureBlueVH, Aizen Victoria Pia Blue BOH, Victoria Blue4RB manufactured by BASF
case and the like.

The photosensitive lithographic printing plate of the present invention is prepared by dissolving the light-to-heat conversion material of the above components, an alkali-soluble resin, and, if necessary, a dissolution inhibitor and other additives in a suitable solvent, And dried. The solvent is not particularly limited as long as it has a sufficient solubility for the components used and gives good coating properties, but it is a cellosolve-based solvent such as methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, and ethyl cellosolve acetate. Propylene glycol solvents such as 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, butyl acetate, Amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxy Ester solvents such as tylate, ethyl acetoacetate, methyl lactate, ethyl lactate, and methyl 3-methoxypropionate; alcohol solvents such as heptanol, hexanol, diacetone alcohol, and furfuryl alcohol; ketone solvents such as cyclohexanone and methyl amyl ketone Solvents, high-polarity solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, or a mixed solvent thereof, and further a mixture of these with an aromatic hydrocarbon are given. 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 used when the photosensitive composition used in the present invention is provided on the surface of the support, conventionally known methods, for example, spin coating, wire bar coating, dip coating, air knife coating, roll coating, It is possible to use blade coating, curtain coating and the like. The photosensitive layer has a thickness of 1 to 3 μm, and a weight thickness of 13 to 30 mg / dm ^2.
Is more preferred, and more preferably 1-2 μm, 16-28 m
g / dm ² is preferred.

The positive photosensitive lithographic printing plate obtained as described above is exposed to an image with a laser beam and then developed with an alkali developing solution to form a positive image. Here, the light source for imagewise exposing the positive photosensitive lithographic printing plate is mainly a HeNe laser, an argon ion laser,
YAG laser, HeCd laser, semiconductor laser,
Although a laser light source such as a ruby laser is mentioned, particularly, when an image is formed by heat generated by absorbing light, a light source that generates a near-infrared laser beam in a wavelength range of 650 to 1,300 nm is preferable, For example, solid-state lasers such as a ruby laser, a YAG laser, a semiconductor laser, and an LED can be used. In particular, a small-sized and long-life semiconductor laser or a YAG laser is preferable.

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 responds to the scanning. 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 an 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 plate making method of the present invention, the light intensity of the light source is preferably 2.0 × 10 ⁶ mJ / s · cm ² or more, and 1.0 × 10 ⁷ mJ / s · cm ² or more. It is particularly preferred to do so. If the light intensity is within 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 practical advantage.

Next, in the plate making method of the present invention, the above-described photosensitive lithographic printing plate is exposed to near-infrared light, preferably in the range of 800 to 1100 nm, and then developed with an alkali developing solution.

Examples of the alkali component used in the developing solution and the developing replenisher include sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, and lithium hydroxide. Inorganic alkali salts such as sodium carbonate, sodium bicarbonate, potassium carbonate, dibasic sodium phosphate, sodium tertiary phosphate, ammonium dibasic phosphate, ammonium tertiary phosphate, sodium borate, potassium borate, ammonium borate, monomethylamine, dimethylamine , Trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine,
Organic amine compounds such as diisopropylamine, monobutylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and the like. These alkali components are preferably used as an aqueous solution of about 0.1 to 5% by weight, Used as an alkaline developer.

Among the above, in the present invention, inorganic alkali salts such as hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and sodium silicate, potassium silicate and lithium silicate The alkali developer containing the alkali metal silicate is preferred.

[0066]

EXAMPLE 30 g of novolak resin (MK-01: weight average molecular weight Mw = 9000) made of Asahi organic material was mixed with acetone 100
g, and the solution was washed with 100 g of heptane. The acetone layer was re-precipitated with 800 ml of water, and the precipitate was filtered and dried. After performing the above operations, a molecular weight of about 2
The ratio of the low molecular weight component of 2,000 or less is 62
% Was reduced to 46% by gel permeation chromatography (GPC). The weight average molecular weight of the obtained polymer was Mw = 120.
00. A printing plate using a coating solution using ordinary novolak resin MK-01 and a printing plate using a coating solution using novolak resin treated as described above were prepared.

The following coating solutions 1 and 2 were applied on an anodized and grained aluminum plate using a wire bar so as to have a dry film thickness of 2.1 g / m ^2.
Drying was performed at ℃ for 3 minutes. After drying, an interleaving paper containing 4% of water is overlaid on the surface of the photosensitive layer, and several dozens of similar plates and interleaving papers are overlaid on top of and under the tape, and the sides are taped.
The lithographic printing plate was obtained by treating for 24 hours in a thermo-hygrostat at a humidity of 40%.

[0068]

[Coating solution 1] Photothermal conversion substance: 6 parts by weight of the following cyanine dye (a) Novolak resin: Novolak resin (MK-01) manufactured by Asahi Organic Materials Phenol / m-cresol / p-cresol = 50/30 / 20 condensed with formaldehyde (Mw = 9000: 62% of a component having a molecular weight of 2,000 or less) 100 parts by weight Dissolution inhibitor 1: Acid-color-forming dye (b) having a lactone skeleton and having the following structure 10 parts by weight Dissolution inhibition Agent 2: Novolac resin and the following compound (c) in an ester bond: 10 parts by weight Lipophilic surfactant: GO-4 (manufactured by Nikko Chemical Co., Ltd.) 4 parts by weight Organic acid: 1,2-cyclohexanedicarboxylic acid 6 parts by weight Crosslinking agent: 1 part by weight, Cymel C-300 (melamine-based crosslinking agent) manufactured by Mitsui Cytec Co., Ltd. Basic surfactant) 0.25 parts by weight Solvent 1: 800 parts by weight methylcellosolve Solvent 2: 200 parts by weight ethylcellosolve

[0069]

Embedded image

[0070]

[Coating solution 2] Photothermal conversion substance: 6 parts by weight of the above-mentioned cyanine dye (a) Novolak resin: Novolak resin (MK-01) made by Asahi Organic Materials Phenol / m-cresol / p-cresol = 50/30 / 20 condensed with formaldehyde (Mw = 12000: 46% of a component having a molecular weight of 2,000 or less) 100 parts by weight Dissolution inhibitor 1: Acid-color-forming dye (b) having a lactone skeleton and having the above structure, 10 parts by weight Dissolution inhibitor 2: Novolak resin and the above compound (c) ester-bonded 10 parts by weight Lipophilic surfactant: GO-4 (manufactured by Nikko Chemical Co., Ltd.) 4 parts by weight Organic acid: 1,2-cyclohexanedicarboxylic acid 6 parts by weight Crosslinking 1 part by weight of Cymel C-300 (melamine-based cross-linking agent) manufactured by Mitsui Cytec Co., Ltd. 0.25 parts by weight Solvent 1: 800 parts by weight methylcellosolve Solvent 2: 200 parts by weight ethylcellosolve

[0071]

[Coating solution 3] Photothermal conversion substance: 6 parts by weight of the above cyanine dye (a) Novolak resin: Novolak resin (MK-01) made by Asahi Organic Materials Phenol / m-cresol / p-cresol = 50/30 / 20 is condensed with formaldehyde (Mw = 12000: 46% of components having a molecular weight of 2,000 or less) 80 parts by weight Phenol resin: Asahi Organic Materials phenolic resin (SP1006: 63% of components having a molecular weight of 2,000 or less) 20 parts by weight ( (A low molecular weight component is 49% as a total of the novolak resin and the phenol resin.) Dissolution inhibitor 1: 10 parts by weight of acid-color-forming dye (b) having a lactone skeleton having the above structure Dissolution inhibitor 2: Novolak resin and compound (c) 10 parts by weight Lipophilic surfactant: GO-4 (manufactured by Nikko Chemical Co., Ltd.) 4 parts by weight Organic acid: 1 , 2-cyclohexanedicarboxylic acid 6 parts by weight Crosslinking agent: Cymel C-300 (Melamine type crosslinking agent) manufactured by Mitsui Cytec Co., Ltd. 1 part by weight Coatability improver: Surflon S-381 (Fluorine type surfactant) manufactured by Asahi Glass Co., Ltd. 0 .25 parts by weight Solvent 1: 800 parts by weight methylcellosolve Solvent 2: 200 parts by weight ethylcellosolve

The photosensitive lithographic printing plate was subjected to 160 mJ / cm with a laser exposure machine (Trendsetter) manufactured by Creo.
Exposure was at an intensity of ² . A suction device was attached to the exposure machine in order to measure the amount of scattered matter due to ablation when the printing plate was previously exposed to a laser before exposure. The components adhering to the filter of the suction device were extracted with acetone and dried under vacuum, and the weight of the adhering matter on the filter was measured as the amount of flying matter. In addition, a similar printing plate is
After exposure with er, developer DR for thermal positive made by Mitsubishi Chemical Corporation
The film was immersed for a predetermined time at -6 and developed, and the residual film ratio was evaluated. The results are shown in Table 1.

[0073]

[Table 4]

A: Amount of filter deposit per exposed area (mg / m ² ) B: Time required for developing exposed area (113 mJ / cm ² ) (s) C: Remaining photosensitive layer ratio of unexposed area: 90% Retention time (s)

[0075]

According to the present invention, it is possible to provide a positive type image forming material which is excellent in balance between scattering (ablation) of a photosensitive layer in an exposed portion and development latitude.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H025 AA01 AA04 AA12 AB03 AC08 AD03 BJ10 CB29 CB55 CC11 DA36 FA17 2H096 AA06 BA09 BA20 EA04 EA23 GA08 2H114 AA04 AA14 AA22 AA24 BA01 BA10 DA26 DA52 DA59 DA64 FA06 EA09 EA09

Claims (11)

[Claims] 1. An image forming material having a positive photosensitive composition layer containing (A) a photothermal conversion substance and (B) an alkali-soluble resin on a support, wherein the alkali-soluble resin is a novolak resin and / or a phenol. Contains resin,
A positive-working image-forming material, wherein an alkali-soluble resin component having a weight average molecular weight of 2,000 or less accounts for 55% by weight or less of the whole alkali-soluble resin. 2. The positive image forming material according to claim 1, wherein the light-to-heat conversion substance contains a cyanine dye. 3. The positive type image forming material according to claim 1, wherein the positive type photosensitive composition layer is substantially insensitive to ultraviolet light. 4. The positive image forming material according to claim 1, wherein the positive photosensitive composition layer contains substantially no quinonediazide compound. 5. The positive image forming material according to claim 1, wherein the support is an aluminum plate that has been subjected to a surface roughening treatment and an anodic oxidation treatment. 6. The novolak resin according to claim 1, wherein the novolak resin is mixed and separated in a solvent comprising a ketone and an aliphatic hydrocarbon which are incompatible with each other, and a component dissolved in the ketone is taken out. The positive image forming material according to any one of the above. 7. The positive image forming material according to claim 6, wherein the ketone is acetone, ethyl methyl ketone, or a mixture thereof. 8. The positive image forming material according to claim 6, wherein the aliphatic hydrocarbon is a saturated aliphatic hydrocarbon having 5 to 8 carbon atoms. 9. A photosensitive composition comprising 30 novolak resins.
The positive image forming material according to any one of claims 1 to 8, wherein the content of the positive type image forming material is from 80 to 80% by weight. 10. A phenol resin in a photosensitive composition.
The positive-type image forming material according to any one of claims 1 to 9, which contains 0 to 40% by weight. 11. The positive image forming material according to claim 1, wherein the material is exposed to near-infrared laser light having a wavelength of 800 to 1100 nm, and then developed with an alkali developing solution. Image forming method.