JP2011197303A - Process for making lithographic printing plate and lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for making a lithographic printing plate in which the generation of development wastes is suppressed in mass processing and even a lithographic printing plate precursor allowed to stand for a long time can stably be developed, and a lithographic printing plate made by the process for making a lithographic printing plate.SOLUTION: The process for making a lithographic printing plate includes in sequence: an exposure step of imagewise exposing a positive-working lithographic printing plate precursor for infrared laser provided above a support and having a positive-working recording layer including (Component A) a (meth)acrylonitrile-derived constitutional unit- and styrene-derived constitutional unit-containing copolymer, (Component B) a water-insoluble and alkali-soluble resin, and (Component C) an infrared absorbing agent, the positive-working recording layer exhibiting increased solubility in an aqueous alkali solution upon exposure or heating; and a development step of developing, using an aqueous alkali solution including a betaine-based surfactant and having a pH of 8.5-10.8.

Description

  The present invention relates to a plate making method of a planographic printing plate and a planographic printing plate.

In the plate-making process of a lithographic printing plate, after exposure, a process of dissolving and removing unnecessary image recording layers with a developer or the like is necessary. However, in terms of environment and safety, processing with a developer closer to the neutral range is necessary. It is desired. In particular, in recent years, disposal of the waste liquid discharged with wet processing has become a major concern for the entire industry due to consideration of the global environment.
On the other hand, in recent years, digitization techniques for electronically processing, storing, and outputting image information by a computer have become widespread, and various new image output methods corresponding to such digitization techniques have been put into practical use. . Along with this, computer-to-plate (CTP) technology that scans and exposes a lithographic printing plate precursor with high-convergence radiation such as laser light and directly produces a lithographic printing plate without going through a lithographic film is attracting attention. Has been. Patent Documents 1 and 2 describe lithographic printing plate precursors for CTP.

JP 11-218914 A JP 2003-84430 A

  An object of the present invention is to prevent the generation of development debris when processed in a large amount, and to make a lithographic printing plate that can be stably developed even using a lithographic printing plate precursor that has been aged, and to make a plate by the plate making method. Is to provide a lithographic printing plate.

The above-described problems of the present invention have been solved by means described in the following <1> to <10>.
<1> On a support, a copolymer comprising (Component A) a structural unit derived from (meth) acrylonitrile and a structural unit derived from styrene, (Component B) a water-insoluble and alkali-soluble resin, and (Component C) an infrared absorber, and an exposure step for image exposure of a positive lithographic printing plate precursor for an infrared laser provided with a positive recording layer that improves solubility in an aqueous alkali solution by exposure or heating, and a betaine interface A plate-making method of a lithographic printing plate, comprising a development step containing an activator and developing using an alkaline aqueous solution having a pH of 8.5 to 10.8 in this order;
<2> The plate making method of a lithographic printing plate according to <1>, wherein the alkaline aqueous solution contains a compound represented by the formula <1> and / or a compound represented by the formula <2>.

（式＜１＞中、Ｒ⁸はアルキル基を表し、Ｒ⁹及びＲ¹⁰はそれぞれ独立に、水素原子又はアルキル基を表し、Ｒ¹¹はアルキレン基を表し、Ａはカルボン酸イオン又はスルホン酸イオンを表す。式＜２＞中、Ｒ¹⁸、Ｒ¹⁹及びＲ²⁰はそれぞれ独立に、水素原子又はアルキル基を表す。ただし、Ｒ¹⁸、Ｒ¹⁹及びＲ²⁰の全てが、水素原子であることはない。）

(In formula <1>, R ⁸ represents an alkyl group, R ⁹ and R ¹⁰ each independently represents a hydrogen atom or an alkyl group, R ¹¹ represents an alkylene group, and A represents a carboxylate ion or a sulfonate ion. In formula <2>, R ¹⁸ , R ¹⁹ and R ²⁰ each independently represent a hydrogen atom or an alkyl group, provided that all of R ¹⁸ , R ¹⁹ and R ²⁰ are hydrogen atoms. Absent.)

<3> The plate making method of a lithographic printing plate according to <1> or <2>, wherein the aqueous alkali solution contains a combination of carbonate ions and hydrogen carbonate ions,
<4> The plate-making method of a lithographic printing plate according to any one of <1> to <3>, wherein the development step is a step of performing development and gumming in one bath.
<5> The plate making method of a lithographic printing plate according to any one of <1> to <4>, wherein the water washing step is not performed before and after the development step,
<6> In any one of <1> to <5>, the positive recording layer is a layer composed of an upper layer containing the component A and a lower layer containing the component B and the component C. Plate making method of the lithographic printing plate as described,
<7> The plate making method of a lithographic printing plate according to any one of <1> to <6>, wherein the upper layer further contains an alkali-soluble resin,
<8> The component B is a copolymer including a structural unit derived from an N-substituted maleimide, a structural unit derived from (meth) acrylamide, and a structural unit derived from (meth) acrylic acid. <7> A method for making a lithographic printing plate according to any one of
<9> The plate-making method of a lithographic printing plate according to any one of <1> to <8>, wherein the component C is a cyanine dye,
<10> A lithographic printing plate produced by the lithographic printing plate making method according to any one of <1> to <9>.

  According to the present invention, the generation of development residue when processed in a large amount is suppressed, and a lithographic printing plate making method that can be stably developed even with the use of an aging lithographic printing plate precursor, and a lithographic plate made by the plate making method We were able to provide a printed version.

The method of the present invention comprises, on a support, a (component A) copolymer containing a structural unit derived from acrylonitrile and a structural unit derived from styrene, (component B) a water-insoluble and alkali-soluble resin, and (component C) an infrared absorber, and an exposure step for image exposure of a positive lithographic printing plate precursor for an infrared laser provided with a positive recording layer that improves solubility in an aqueous alkali solution by exposure or heating, and a betaine interface And a developing step of developing using an alkaline aqueous solution containing an activator and having a pH of 8.5 to 10.8. In addition, "A-B" etc. showing a numerical range are synonymous with "A or more and B or less", and it is the same below. In this specification, “(meth) acrylate” and the like mean “acrylate and methacrylate” and the like.
Hereinafter, after describing each constitution of the lithographic printing plate precursor according to the invention, a plate making method of the lithographic printing plate according to the invention will be explained.

I. Positive lithographic printing plate precursor for infrared laser (positive recording layer)
The positive lithographic printing plate precursor for infrared laser in the present invention (hereinafter also referred to as “lithographic printing plate precursor”) is a structural unit derived from (component A) acrylonitrile and a structural unit derived from styrene on a support. A positive-type recording layer containing (copolymer B), (component B) a water-insoluble and alkali-soluble resin, and (component C) an infrared absorber, and having improved solubility in an alkaline developer by exposure or heating ( Hereinafter, it is a planographic printing plate precursor provided with simply a “recording layer”.
The recording layer is preferably a layer composed of an upper layer containing at least the component A and a lower layer containing at least the component B and the component C. Hereinafter, each component contained in the upper layer and the lower layer will be described.

(Upper layer)
In the non-exposed portion (that is, the image portion), the upper layer protects the lower layer from the developer. The upper layer is insoluble in an alkaline developer before image formation (that is, before image exposure). However, the exposed areas of the upper layer can be removed by the developer after thermal exposure (ie thermal imaging). Without being bound by any theory or explanation, it is believed that upon image exposure, the upper layer dissolves or disperses more easily in the developer and / or weakens the adhesion between the upper and lower layers. Thereby, the developer penetrates into the upper layer and the lower layer, the lower layer is dissolved, and the surface of the support appears. Hereinafter, components contained in the upper layer will be described.

(Component A) Copolymer Comprising Structural Unit Derived from (Meth) acrylonitrile and Structural Unit Derived from Styrene In the present invention, the lithographic printing plate precursor has a positive recording layer containing component A. When the positive recording layer has an upper layer and a lower layer, the component A is preferably contained in the upper layer.
Component A may be insoluble in an aqueous alkaline developer. It is considered that when the developer penetrates into the upper layer in the exposure region and the lower layer is dissolved or dispersed in these regions, the upper layer and the lower layer are removed and dispersed in the developer.

From the viewpoint of development residue, acrylonitrile is preferred as the (meth) acrylonitrile serving as the constituent unit of component A.
As styrene which is a structural unit derived from styrene, not only a styrene monomer but also a styrene derivative having at least one substituent may be used. Examples of the substituent herein include a halogen atom (F atom, Cl atom, Br atom, I atom) and an alkyl group having 1 to 10 carbon atoms.
Specific examples of styrene and styrene derivatives include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, pn. -Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4- Examples include styrene such as dimethylstyrene and 3,4-dichlorostyrene. Among them, styrene is preferable.

In Component A, a monomer other than styrene or acrylonitrile may be copolymerized as the third component as another component. As the third component, an alkali-soluble group-containing ethylenically unsaturated monomer is preferable. Such ethylenically unsaturated monomers include, in addition to acrylic acid and methacrylic acid, compounds represented by the following formula and mixtures thereof. In each formula, R represents a hydrogen atom or a methyl group. In each formula, —OH, —SO ₂ NH ₂ , and —COOH bonded to the phenyl group are bonded to an arbitrary position of the phenyl group.

  In the present invention, (meth) acrylic acid is preferable as the third component, and methacrylic acid is more preferable.

In the component A, the proportion of the structural unit derived from (meth) acrylonitrile is preferably 10 to 40 mol%, more preferably 15 to 35 mol%, and still more preferably 20 to 30 mol% from the viewpoint of development residue. .
In the component A, the proportion of the structural unit derived from styrene is preferably 55 to 85 mol%, more preferably 60 to 80 mol%, and still more preferably 65 to 75 mol%, from the viewpoint of the inking property.
The proportion of the structural unit derived from the third component in Component A is preferably 15 mol% or less, more preferably 10 mol% or less, and even more preferably 6 mol% or less.

  The weight average molecular weight of Component A is preferably 1,000 to 1,000,000, more preferably 3,000 to 300,000, and still more preferably 10,000 to 50,000.

The content of Component A in the recording layer is preferably from 5 to 70% by weight, more preferably from 20 to 55% by weight, more preferably from 35 to 45% by weight, based on the total solid content excluding volatile components in the recording layer. Is more preferable.
The content of component A in the upper layer is preferably 10 to 80% by weight, more preferably 40 to 75% by weight, and further 60 to 70% by weight, based on the total solid content excluding the volatile components of the upper layer. preferable.

  The upper layer may contain a resin other than component A, such as (meth) acrylic polymers and copolymers; polystyrene; styrene / acrylic copolymers; polyesters; polyamides; polyurea; polyurethanes; nitrocellulose; You may mix | blend a mixture.

(Alkali-soluble resin)
The recording layer preferably contains an alkali-soluble resin other than Component B. In particular, when the recording layer is a multilayer composed of an upper layer and a lower layer, it is more preferable that the upper layer contains an alkali-soluble resin. Examples of such alkali-soluble resins include alkali-soluble polyurethane resins, alkali-soluble phenol resins, and alkali-soluble resins having a urea bond in the side chain.

  The alkali-soluble polyurethane resin used in the present invention preferably has a carboxy group in the polymer main chain. Specifically, the diisocyanate compound represented by the formula (I) and the formula (II) or the formula (III) are used. The polyurethane resin which uses the reaction product with the diol compound which has a carboxy group represented by these as a basic skeleton is mentioned.

In the formula (I), R ¹ represents a divalent hydrocarbon group. R ¹ is preferably an alkylene group having 2 to 10 carbon atoms or an arylene group having 6 to 30 carbon atoms. R ¹ may be substituted with another functional group that does not react with the isocyanate group.
In formula (II), R ² represents a hydrogen atom or a hydrocarbon group. R ² is preferably a hydrogen atom, an unsubstituted alkyl group having 1 to 8 carbon atoms, or an unsubstituted aryl group having 6 to 15 carbon atoms.
In formula (II) and formula (III), R ³ , R ⁴ and R ⁵ each independently represents a single bond or a divalent linking group. Examples of the divalent linking group include aliphatic hydrocarbons and aromatic hydrocarbons, and preferably an unsubstituted alkylene group having 1 to 20 carbon atoms and an unsubstituted arylene group having 6 to 15 carbon atoms. More preferred are unsubstituted alkylene groups having 1 to 8 carbon atoms.
In formula (III), Ar represents a trivalent aromatic hydrocarbon, preferably a trivalent aromatic hydrocarbon having 6 to 15 carbon atoms.
R ^{1 to} R ⁵ and Ar may have a substituent that does not react with the isocyanate group.

  Specific examples of the diisocyanate compound represented by the formula (I) include 2,4-tolylene diisocyanate, dimer of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-xylylene diisocyanate, meta Aromatic diisocyanate compounds such as xylylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate; hexamethylene diisocyanate, trimethylhexamethylene diisocyanate Aliphatic diisocyanate compounds such as lysine diisocyanate and dimer acid diisocyanate; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane Alicyclic diisocyanate compounds such as sun-2,4 (or 2,6) diisocyanate, 1,3- (isocyanatomethyl) cyclohexane; adducts of 1 mol of 1,3-butylene glycol and 2 mol of tolylene diisocyanate, etc. And a diisocyanate compound which is a reaction product of a diol and a diisocyanate. Among these, those having an aromatic ring such as 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and tolylene diisocyanate are preferable from the viewpoint of printing durability.

  Specific examples of the diol compound having a carboxy group represented by formula (II) or formula (III) include 3,5-dihydroxybenzoic acid, 2,2-bis (hydroxymethyl) propionic acid, 2,2- Bis (hydroxyethyl) propionic acid, 2,2-bis (3-hydroxypropylpropionic acid, 2,2-bis (hydroxymethyl) acetic acid, bis- (4-hydroxyphenyl) acetic acid, 4,4-bis- (4 -Hydroxyphenyl) pentanoic acid, tartaric acid, etc. Among them, 2,2-bis (hydroxymethyl) propionic acid and 2,2-bis (hydroxyethyl) propionic acid are preferable from the viewpoint of reactivity with isocyanate.

The polyurethane resin can be synthesized by adding the above-mentioned diisocyanate compound and diol compound in an aprotic solvent to a known catalyst having an activity corresponding to the reactivity and heating.
The molar ratio of the diisocyanate and the diol compound to be used is preferably 0.8: 1 to 1.2: 1. When an isocyanate group remains at the polymer terminal, the final treatment is performed with an alcohol or an amine. Thus, it is synthesized in a form in which no isocyanate group remains.

  The weight average molecular weight of the polyurethane resin is preferably 1,000 or more, and more preferably in the range of 5,000 to 100,000. These polyurethane resins may be used in combination of two or more.

  As the alkali-soluble phenol resin, for example, an alkali-soluble novolak resin is suitable. Examples of the alkali-soluble novolak resin include phenol formaldehyde novolak resin, m-cresol formaldehyde novolak resin, p-cresol formaldehyde novolak resin, m- / p-mixed cresol formaldehyde novolak resin, phenol / cresol (m-, p-, m Any of-/ p- may be used) Alkali-soluble novolak resins such as mixed formaldehyde novolak resins may be mentioned. Moreover, you may use together the condensate of phenol and formaldehyde which has a C3-C8 alkyl group as a substituent, such as t-butyl phenol formaldehyde resin and octyl phenol formaldehyde resin.

  The weight average molecular weight of the alkali-soluble phenol resin is preferably 500 to 20,000, more preferably 1,000 to 10,000, and further preferably 2,000 to 8,000.

  As the alkali-soluble resin having a urea bond in the side chain, a polymer of an acrylic monomer having a urea bond having a phenolic hydroxyl group as a substituent is preferable. For example, a polymer of a compound represented by the formula (IV) is preferable. Can be mentioned.

In the formula (IV), R represents a hydrogen atom or an alkyl group.
X represents a divalent linking group, and examples thereof include an alkylene group and a phenylene group. X is preferably an alkylene group, more preferably a linear or branched alkylene group having 1 to 10 carbon atoms, and still more preferably an alkylene group having 1 to 4 carbon atoms.
Y represents a divalent aromatic group which may have a substituent, and examples thereof include a phenylene group or a naphthylene group which may have a substituent. Examples of the substituent include an alkyl group having 1 to 3 carbon atoms and an aryl group having 6 to 20 carbon atoms.

  From the viewpoint of development latitude, the content of the structural unit derived from the compound represented by the formula (IV) in the alkali-soluble resin is 10 to 80 mol%, based on 100 mol% of all monomer units of the alkali-soluble resin. Is preferable, 15-70 mol% is more preferable, and 20-60 mol% is especially preferable.

  The polymer of a monomer having a urea bond with a phenolic hydroxyl group as a substituent is preferably a copolymer with a compound having a polymerizable unsaturated bond and not containing a urea bond. The copolymer is preferably obtained by copolymerizing a polymerizable monomer that does not contain a urea bond using 10 to 80 mol% with the total number of structural units contained in the copolymer being 100 mol%. .

As such a monomer, an N-phenylmaleimide derivative or an acrylic monomer having a sulfonamide group in the side chain is particularly preferable. Examples of the N-phenylmaleimide derivative include N-phenylmaleimide, N-2-methylphenylmaleimide, N-2,6-diethylphenylmaleimide, N-2-chlorophenylmaleimide, N-hydroxyphenylmaleimide and the like.
Examples of the (meth) acrylic monomer having a sulfonamide group in the side chain include m-aminosulfonylphenyl (meth) acrylate, N- (p-aminosulfonylphenyl) (meth) acrylamide, N- (p-aminosulfonylphenyl) ( And (meth) acrylamide.

The weight average molecular weight of the alkali-soluble resin having a urea bond in the side chain is preferably 2,000 or more, and more preferably 3,000 to 500,000.
Further, the number average molecular weight is preferably 1,000 or more, more preferably 2,000 to 400,000.

  The alkali-soluble resin contained in the upper layer is preferably an alkali-soluble polyurethane resin or an alkali-soluble phenol resin, and more preferably an alkali-soluble polyurethane resin.

The content of the alkali-soluble resin other than Component B in the recording layer is preferably 40% by weight or less, more preferably 10 to 35% by weight, based on the total solid content excluding the volatile components of the recording layer. More preferred is ˜30% by weight.
The content of the alkali-soluble resin other than component B in the upper layer is preferably 50% by weight or less, more preferably 15 to 45% by weight, more preferably 20 to 40% by weight based on the total solid content excluding the volatile component of the upper layer. More preferred is weight percent.

(Underlayer)
Next, the lower layer in the recording layer will be described. The lower layer preferably contains (Component B) a water-insoluble and alkali-soluble resin, and (Component C) an infrared absorber. The lower layer exists between the upper layer and the support. After imaging, the lower layer is removed with an aqueous alkaline solution along with the upper layer in the imaging area to expose the underlying support. The lower layer is preferably soluble in an aqueous alkali solution in order to avoid the generation of residue in the developer.

(Component B) Water-insoluble and alkali-soluble resin The recording layer contains (Component B) a water-insoluble and alkali-soluble resin. Here, “water-insoluble” means that when an approximate resin is applied to the recording layer of a positive photosensitive lithographic printing plate, development is performed under conditions of a developer temperature of 25 to 35 ° C., a developer pH of 6 to 8, and 30 seconds. Is also insoluble, and “alkali-soluble” means that when developed under conditions of a developer temperature of 25 ° C. to 35 ° C. and a developer pH of 8.5 to 10.8 for 60 seconds, it exhibits solubility. .
When the recording layer is composed of an upper layer and a lower layer, component B may be contained in either the upper layer or the lower layer, and is preferably contained only in the lower layer.

Examples of water-insoluble and alkali-soluble resins include alkali-soluble acrylic resins and the alkali-soluble phenol resins, and alkali-soluble acrylic resins are preferred. As the alkali-soluble acrylic resin, a polymer produced by polymerizing a monomer mixture containing one or more ethylenically unsaturated monomers having an acidic group is suitably used.
As an ethylenically unsaturated monomer which has an acidic group, the alkali-soluble group containing ethylenically unsaturated monomer which can be copolymerized as a 3rd component in the component A is mentioned. Of these, (meth) acrylic acid is preferable, and methacrylic acid is more preferable.

  Since it is excellent in developability, the content of the ethylenically unsaturated monomer having an acidic group imparting alkali solubility is preferably 1 to 30 mol%, with the structural unit contained in Component B being 100 mol%, 25 mol% is more preferable, and 10 to 20 mol% is more preferable.

  Other polymerizable monomers other than ethylenically unsaturated monomers having acidic groups include alkyl (meth) acrylates, (meth) acrylic acid esters having an aliphatic hydroxyl group, (meth) acrylamides, vinyl esters, styrenes. , N-vinyl pyrrolidone and other nitrogen atom-containing monomers and maleimides. Among these other polymerizable monomers, (meth) acrylic acid esters, (meth) acrylamides, maleimides, and (meth) acrylonitrile are preferably used, and (meth) acrylamide is more preferable. , Maleimides.

  As maleimides, N-substituted maleimides are preferable. Examples of N-substituted maleimides include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, and Nn-butyl. Mention may be made of maleimide, Nt-butylmaleimide, Nn-hexylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-1-naphthylmaleimide and the like. Among these, N-cyclohexylmaleimide and N-phenylmaleimide are preferable, and N-phenylmaleimide is more preferable. The N-substituted maleimide may be used alone or in combination of two or more.

  The content of the structural unit derived from the N-substituted maleimide is preferably 75 mol% or less, more preferably 45 to 75 mol%, more preferably 50 to 70 mol%, based on 100 mol% of the structural unit contained in Component B. Further preferred.

  Component B preferably contains a structural unit derived from (meth) acrylamide, and the content of the structural unit derived from (meth) acrylamide is 40 mol, with the structural unit contained in Component B being 100 mol%. % Or less is preferable, 10 to 40 mol% is more preferable, and 20 to 30 mol% is more preferable.

The weight average molecular weight of the alkali-soluble acrylic resin of Component B is preferably 2,000 or more, more preferably 10,000 to 100,000, and still more preferably 30,000 to 60,000.
The number average molecular weight of component B is preferably 500 to 250,000.
Those having a dispersity (weight average molecular weight / number average molecular weight) of 1.1 to 10 are preferred.

The content of Component B in the recording layer is preferably 30 to 60% by weight, more preferably 35 to 55% by weight, and more preferably 40 to 50% by weight, based on the total solid content excluding the volatile components of the recording layer. Is more preferable.
The content of the component B in the lower layer is preferably 20 to 98% by weight, more preferably 60 to 98% by weight, and further 80 to 98% by weight based on the total solid content excluding the volatile components of the lower layer. preferable.

(Component C) Infrared Absorber In the lithographic printing plate precursor, it is necessary to add (Component C) an infrared absorber to the recording layer. When the recording layer is a multilayer, it is necessary to add it to the lower layer, and it may be added to the upper layer. As Component C, various dyes known as infrared absorbers can be used.

  As the infrared absorber, known ones can be used, and examples thereof include azo dyes, metal complex azo dyes, pyrazolone azo dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, and cyanine dyes. In the present invention, among these dyes, those that absorb infrared light or near-infrared light are preferred because they are suitable for use in lasers that emit infrared light or near-infrared light, and cyanine dyes are particularly preferred. .

Examples of the dye that absorbs at least infrared light or near infrared light include, for example, JP-A-58-125246, JP-A-59-84356, JP-A-59-202829, JP-A-60-. Cyanine dyes described in each publication such as 78787, methine dyes described in each publication such as JP-A-58-173696, JP-A-58-181690, JP-A-58-194595, Japanese Laid-Open Patent Publication Nos. 58-112793, 58-224793, 59-48187, 59-73996, 60-52940, 60-63744, etc. Naphthoquinone dyes described in JP-A-58-112792, squarylium dyes described in JP-A-58-112792, cyanine dyes described in British Patent 434,875, etc. Can.
Further, near-infrared absorption sensitizers described in US Pat. No. 5,156,938 are also preferably used as dyes, and substituted arylbenzoates described in US Pat. No. 3,881,924 are also preferred. (Thio) pyrylium salt, trimethine thiapyrylium salt described in JP-A-57-142645 (U.S. Pat. No. 4,327,169), JP-A-58-181051, JP-A-58-2220143, 59-41363, 59-84248, 59-84249, 59-146063, 59-146061, and pyrium compounds described in JP-A-59-216146. Cyanine dyes, pentamethine thiopyrylium salts described in US Pat. No. 4,283,475, etc., and Japanese Patent Publication Nos. 5-13514 and 5-19702 Pyrylium compounds disclosed in distribution is, as commercially available products, Epolight III-178 of Eporin Co., Epolight III-130, Epolight III-125 and the like are particularly preferably used.
Another particularly preferable example of the dye is a near-infrared absorbing dye described as formulas (I) and (II) in US Pat. No. 4,756,993.
Among them, cyanine dyes are preferable, and examples include cyanine dyes represented by general formula (I) in JP-A No. 2001-305722 and compounds shown in [0096] to [0103] in JP-A No. 2002-079772. Can do. Particularly preferred dyes are the following cyanine dye A.

  The amount of the infrared absorber added is 0.01 to 50% by weight, preferably 0.1 to 30% by weight, particularly preferably 1.0 to 30% by weight, based on the total solid content of the lower layer. Can do.

Furthermore, in the upper layer component according to the present invention, other resins can be used in combination as long as the effects of the present invention are not impaired. Since the upper layer itself needs to be dissolved or dispersed in the developer, particularly in the non-image area (ie, the exposed area), it is necessary to select a resin that does not impair this property.
From this viewpoint, examples of resins that can be used in combination include alkali-soluble resins. Among them, for example, polyamide resin, epoxy resin, polyacetal resin, acrylic resin, methacrylic resin, polystyrene resin and the like can be preferably exemplified.
The amount to be mixed is preferably 50% by weight or less based on 100% by weight of the water-insoluble and alkali-soluble resin.

<Other additives>
In forming the lower layer and the upper layer of the recording layer, in addition to the essential components described above, various additives can be added as necessary as long as the effects of the present invention are not impaired. The additives listed below may be added only to the lower layer, may be added only to the upper layer, or may be added to both layers.

[Development accelerator]
For the purpose of improving sensitivity, acid anhydrides, phenols, and organic acids may be added to the upper layer and / or the lower layer.
As the acid anhydrides, cyclic acid anhydrides are preferable. Specific examples of the cyclic acid anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, and hexahydro anhydride described in US Pat. No. 4,115,128. Phthalic acid, 3,6-endooxytetrahydrophthalic anhydride, tetrachlorophthalic anhydride, maleic anhydride, chloromaleic anhydride, α-phenylmaleic anhydride, succinic anhydride, pyromellitic anhydride and the like can be used. Examples of acyclic acid anhydrides include acetic anhydride.
Examples of phenols include bisphenol A, 2,2′-bishydroxysulfone, p-nitrophenol, p-ethoxyphenol, 2,4,4′-trihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 4- Examples include hydroxybenzophenone, 4,4 ′, 4 ″ -trihydroxytriphenylmethane, 4,4 ′, 3 ″, 4 ″ -tetrahydroxy-3,5,3 ′, 5′-tetramethyltriphenylmethane. .
Examples of the organic acids are described in JP-A-60-88942, JP-A-2-96755, and the like. Specifically, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfinic acid, Ethyl sulfuric acid, phenylphosphonic acid, phenylphosphinic acid, phenyl phosphate, diphenyl phosphate, benzoic acid, isophthalic acid, adipic acid, p-toluic acid, 3,4-dimethoxybenzoic acid, phthalic acid, terephthalic acid, 4-cyclohexene Examples include -1,2-dicarboxylic acid, erucic acid, lauric acid, n-undecanoic acid, ascorbic acid and the like.
The proportion of the acid anhydride, phenols and organic acids in the total solid content of the lower or upper layer is preferably 0.05 to 20% by weight, more preferably 0.1 to 15% by weight, and more preferably 0.1 to 10%. Weight percent is particularly preferred.

[Surfactant]
The upper layer and / or the lower layer are described in JP-A Nos. 62-251740 and 3-208514 in order to improve the coatability and to increase the stability of processing with respect to development conditions. Such nonionic surfactants, amphoteric surfactants as described in JP-A-59-121044 and JP-A-4-13149, JP-A-62-170950, JP-A-11-288093 And a monomer copolymer containing fluorine as described in JP-A-2003-57820.
Specific examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether and the like.
Specific examples of amphoteric activators include alkyldi (aminoethyl) glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine and N-tetradecyl-N, N-betaine. Type (for example, trade name “Amorgen K” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).
The proportion of the surfactant in the total solid content of the lower layer or upper layer is preferably 0.01 to 15% by weight, more preferably 0.1 to 5% by weight, and even more preferably 0.05 to 2.0% by weight.

[Bakeout agent / colorant]
To the upper layer and / or the lower layer, a printing out agent for obtaining a visible image immediately after heating by exposure, or a dye or pigment as an image colorant can be added.
A representative example of the printing-out agent is a combination of a compound that releases an acid by heating by exposure (photoacid releasing agent) and an organic dye that can form a salt. Examples of the photoacid releasing agent include o-naphthoquinonediazide-4-sulfonic acid halide, and triazine compounds and trihalomethyl compounds as oxazole compounds.

As the colorant, other known dyes can be used in addition to the aforementioned salt-forming organic dyes. Examples of suitable dyes including salt-forming organic dyes include oil-soluble dyes and basic dyes. Specifically, Oil Yellow # 101, Oil Yellow # 103, Oil Pink # 312, Oil Green BG, Oil Blue BOS, Oil Blue # 603, Oil Black BY, Oil Black BS, Oil Black T-505 (orientated chemistry) Kogyo Co., Ltd.), Victoria Pure Blue, Crystal Violet Lactone, Crystal Violet (CI42555), Methyl Violet (CI42535), Ethyl Violet, Rhodamine B (CI145170B), Malachite Green (CI42000), Methylene Blue (CI52015), etc. Can do. Further, the dyes described in JP-A-62-293247 are particularly preferred.
These dyes are preferably added at a rate of 0.01 to 10% by weight, more preferably at a rate of 0.1 to 3% by weight, based on the total solid content of the lower or upper layer.

[Plasticizer]
A plasticizer may be added to the upper layer and / or the lower layer in order to impart flexibility or the like of the coating film. For example, butylphthalyl, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate, acrylic acid or methacrylic acid These oligomers and polymers are used.
These plasticizers are preferably added at a rate of 0.5 to 10% by weight, more preferably 1.0 to 5% by weight, based on the total solid content of the lower layer or upper layer.

[Wax agent]
In the upper layer, a compound that lowers the static friction coefficient of the surface can be added for the purpose of imparting resistance to scratches. Specifically, as described in US Pat. No. 6,117,913, JP-A No. 2003-149799, JP-A No. 2003-302750, or JP-A No. 2004-12770, A compound having an ester of a long-chain alkyl carboxylic acid can be exemplified.
The amount added is preferably 0.1 to 10% by weight and more preferably 0.5 to 5% by weight in the upper layer.

<Formation of lower layer and upper layer>
The lower layer and the upper layer in the lithographic printing plate precursor are preferably formed by dissolving the above-described components in a solvent and coating the solution on a suitable support.
Solvents used here include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxy Examples include ethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and toluene. It is not limited to. These solvents are used alone or in combination.

  In principle, the lower layer and the upper layer are preferably formed by separating two layers. As a method for forming the two layers separately, for example, a method using a difference in solvent solubility between a component contained in the lower layer and a component contained in the upper layer, or after applying the upper layer, a solvent is rapidly used. For example, a method of drying and removing. Hereinafter, although these methods are explained in full detail, the method of isolate | separating and apply | coating two layers is not limited to these.

As a method of utilizing the difference in solvent solubility between the component contained in the lower layer and the component contained in the upper layer, a solvent system in which any of the components contained in the lower layer is insoluble is used when the upper layer coating solution is applied. Is. Thereby, even if it carries out 2 layer application | coating, it becomes possible to isolate | separate each layer clearly and to make a coating film.
For example, as the solvent for the upper layer, 3-pentanone and propylene glycol monomethyl ether-2-acetate that dissolves the alkali-soluble resin as the upper layer component and does not dissolve the lower layer component are selected. A solvent system mainly composed of γ-butyrolactone that dissolves the solution is selected, applied and dried. Thereafter, the upper layer mainly composed of an alkali-soluble resin is dissolved in 3-pentanone, propylene glycol monomethyl ether-2-acetate or the like, and applied and dried, whereby two layers can be formed.

  After applying the second layer (upper layer), the solvent can be dried very quickly by blowing high-pressure air from a slit nozzle installed almost perpendicular to the web running direction, or by using a heating medium such as steam. It can be achieved by applying thermal energy as conduction heat from the lower surface of the web from the roll (heating roll) supplied to the above or a combination thereof.

  Moreover, in order to provide a new function, the upper layer and the lower layer may be partially miscible in a range where the effects of the present invention are sufficiently exhibited. Such a method can be achieved by adjusting the degree of any of the above methods using the difference in solvent solubility and the method of drying the solvent very quickly after the second layer is applied.

The concentration of the above-described components (total solid content including additives) in the lower layer / upper layer coating solution to be coated on the support is preferably 1 to 50% by weight.
Various methods can be used as the coating method, and examples thereof include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.
In particular, in order to prevent damage to the lower layer during the upper layer coating, the upper layer coating method is preferably a non-contact type. Moreover, although it is a contact type, it is also possible to use bar coater coating as a method generally used for solvent-based coating, but it is preferable to apply by forward driving in order to prevent damage to the lower layer.

Coating amount after drying of a lower layer component applied onto the support of the lithographic printing plate precursor is preferably in the range of ^{0.5~4.0g / m 2, 0.6~2.5g / m} 2 It is more preferable that it is in the range. When it is 0.5 g / m ² or more, printing durability is excellent, and when it is 4.0 g / m ² or less, image reproducibility and sensitivity are excellent.
The coating amount after drying of the upper layer component is preferably in the range of 0.05 to 1.0 g / m ^2, and more preferably in the range of 0.08 to 0.7 g / m ^2. If it is 0.05 g / m ² or more, development latitude, and excellent scratch resistance, if it is 1.0 g / m ² or less, excellent sensitivity.
The lower layer and the coating amount after drying of the combined upper layer, preferably in the range of 0.6~4.0g / m ^2, more preferably in the range of 0.7 to 2.5 g / m ² . When it is 0.6 g / m ² or more, printing durability is excellent, and when it is 4.0 g / m ² or less, image reproducibility and sensitivity are excellent.

<Support>
The support is not particularly limited as long as it is a dimensionally stable plate having necessary strength and durability. For example, paper, plastic (for example, polyethylene, polypropylene, polystyrene, etc.) is laminated. Paper, metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene , Polycarbonate, polyvinyl acetal, etc.), paper on which a metal as described above is laminated or vapor-deposited, or a plastic film.

  Among them, in the present invention, a polyester film or an aluminum plate is preferable, and among them, an aluminum plate that has good dimensional stability and is relatively inexpensive is particularly preferable. A suitable aluminum plate is a pure aluminum plate or an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements, and may be a plastic film on which aluminum is laminated or vapor-deposited. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is preferably 10% by weight or less.

Particularly suitable aluminum in the present invention is pure aluminum, but completely pure aluminum is difficult to produce in the refining technique, and may contain slightly different elements.
Thus, the composition of the aluminum plate applied to the present invention is not specified, and an aluminum plate made of a publicly known material can be appropriately used. The thickness of the aluminum plate used in the present invention is preferably 0.1 to 0.6 mm, more preferably 0.15 to 0.4 mm, and particularly preferably 0.2 to 0.3 mm.

Such an aluminum plate may be subjected to a surface treatment such as a roughening treatment or an anodizing treatment as necessary. Hereinafter, such a surface treatment will be briefly described.
Prior to roughening the aluminum plate, a degreasing treatment with, for example, a surfactant, an organic solvent, or an alkaline aqueous solution for removing rolling oil on the surface is performed as desired. The surface roughening treatment of the aluminum plate is performed by various methods. For example, a method of mechanically roughening, a method of electrochemically dissolving and roughening a surface, and a method of selectively dissolving a surface chemically. This is done by the method of As the mechanical method, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, or a buff polishing method can be used. Further, as an electrochemical surface roughening method, there is a method of performing alternating current or direct current in hydrochloric acid or nitric acid electrolyte. Further, as disclosed in JP-A-54-63902, a method in which both are combined can also be used.
The aluminum plate roughened as described above is subjected to an alkali etching treatment and neutralization treatment as necessary, and then subjected to an anodizing treatment if desired in order to enhance the water retention and wear resistance of the surface. As the electrolyte used for the anodizing treatment of the aluminum plate, various electrolytes that form a porous oxide film can be used. In general, sulfuric acid, phosphoric acid, oxalic acid, chromic acid, or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte.

The anodizing treatment conditions vary depending on the electrolyte used and cannot be specified in general, but in general, the electrolyte concentration is 1 to 80% by weight solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 to 60 A / dm ^2. The voltage is preferably in the range of 1 to 100 V and the electrolysis time of 10 seconds to 5 minutes. The amount of the anodized film is preferably 1.0 g / m ² or more. When it is 1.0 g / m ² or more, the printing durability is excellent, the non-image portion of the lithographic printing plate is hardly scratched, and so-called “scratch stain” in which ink adheres to the scratched portion during printing is suppressed. it can.
After the anodizing treatment, the aluminum surface is subjected to a hydrophilic treatment if necessary.

  Examples of the hydrophilization treatment used in the present invention include U.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and 3,902,734. There are alkali metal silicate (e.g., aqueous sodium silicate) methods as disclosed in the specification. In this method, the support is immersed in an aqueous sodium silicate solution or electrolytically treated. In addition, potassium fluoride zirconate disclosed in Japanese Patent Publication No. 36-22063 and U.S. Pat. Nos. 3,276,868, 4,153,461, and 4,689,272 For example, a method of treating with polyvinylphosphonic acid as disclosed in the literature is used.

<Undercoat layer>
In the lithographic printing plate precursor, an undercoat layer can be provided between the support and the recording layer as necessary.
Various organic compounds are used as an undercoat layer component, for example, phosphonic acids having an amino group such as carboxymethylcellulose, dextrin, gum arabic, 2-aminoethylphosphonic acid, phenylphosphonic acid, naphthylphosphonic acid, alkylphosphonic acid , Organic phosphonic acids such as glycerophosphonic acid, methylenediphosphonic acid and ethylenediphosphonic acid, organic phosphoric acids such as phenylphosphoric acid, naphthylphosphoric acid, alkylphosphoric acid and glycerophosphoric acid, phenylphosphinic acid, naphthylphosphinic acid, alkylphosphinic acid And organic phosphinic acids such as glycerophosphinic acid, amino acids such as glycine and β-alanine, and hydrochlorides of amines having a hydroxy group such as hydrochloride of triethanolamine. These undercoat layer components may be used singly or in combination of two or more.

  This organic undercoat layer can be provided by the following method. That is, a method in which a solution obtained by dissolving the above organic compound in water or an organic solvent such as methanol, ethanol, methyl ethyl ketone, or a mixed solvent thereof is applied on an aluminum plate and dried, and water, methanol, ethanol, methyl ethyl ketone, etc. In this method, an aluminum plate is immersed in a solution obtained by dissolving the above organic compound in an organic solvent or a mixed solvent thereof to adsorb the above compound, and then washed with water and dried to provide an organic undercoat layer. . In the former method, a solution having a concentration of 0.005 to 10% by weight of the organic compound can be applied by various methods. In the latter method, the concentration of the solution is preferably 0.01 to 20% by weight, more preferably 0.05 to 5% by weight, and the immersion temperature is preferably 20 to 90 ° C, more preferably 25 to 50 ° C. The immersion time is preferably 0.1 second to 20 minutes, more preferably 2 seconds to 1 minute. The solution used for this can be adjusted to a pH range of 1 to 12 with basic substances such as ammonia, triethylamine, potassium hydroxide, and acidic substances such as hydrochloric acid and phosphoric acid. A yellow dye can also be added to improve the tone reproducibility of the image recording material.

The coverage of the organic undercoat layer is preferably 2 to 200 mg / m ^2, and more preferably 5 to 100 mg / m ^2. When the coating amount is in the above range, sufficient printing durability can be obtained. The lithographic printing plate precursor produced as described above is imagewise exposed and then developed.

<Back coat layer>
A back coat layer is provided on the back surface of the support of the lithographic printing plate precursor according to the invention, if necessary. Such a back coat layer comprises a metal oxide obtained by hydrolysis and polycondensation of an organic polymer compound described in JP-A-5-45885 and an organic or inorganic metal compound described in JP-A-6-35174. A coating layer is preferably used. Among these coating layers, silicon alkoxy compounds such as Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Si (OC ₃ H ₇ ) ₄ , and Si (OC ₄ H ₉ ) ₄ are available at a low price. The coating layer of the metal oxide obtained therefrom is particularly preferable because of its excellent developer resistance.

(Plate making method of lithographic printing plate)
The plate making method of the lithographic printing plate of the present invention includes an exposure step for image exposure of the positive type lithographic printing plate precursor for infrared laser and a development step for developing using a developer in this order.

<Exposure process>
The plate-making method of the lithographic printing plate of the present invention includes an exposure step of image-exposing the positive lithographic printing plate precursor for infrared laser.
As a light source of actinic rays used for image exposure of a lithographic printing plate precursor, a light source having an emission wavelength in the near infrared to infrared region is preferable, and a solid laser or a semiconductor laser is particularly preferable. Among them, in the present invention, it is particularly preferable that the image exposure is performed by a solid laser or a semiconductor laser that emits infrared rays having a wavelength of 750 to 1,400 nm.

The laser output is preferably 100 mW or more, and a multi-beam laser device is preferably used in order to shorten the exposure time. The exposure time per pixel is preferably within 20 μsec.
The energy applied to the planographic printing plate precursor is preferably 10 to 300 mJ / cm ² . When it is in the above range, curing can proceed sufficiently, and laser ablation can be suppressed and image damage can be prevented.

  The exposure in the present invention can be performed by overlapping the light beams of the light sources. Overlap means that the sub-scanning pitch width is smaller than the beam diameter. The overlap can be expressed quantitatively by FWHM / sub-scanning pitch width (overlap coefficient), for example, when the beam diameter is expressed by the full width at half maximum (FWHM) of the beam intensity. In the present invention, the overlap coefficient is preferably 0.1 or more.

  The scanning method of the light source of the exposure apparatus that can be used in the present invention is not particularly limited, and a cylindrical outer surface scanning method, a cylindrical inner surface scanning method, a planar scanning method, and the like can be used. The channel of the light source may be a single channel or a multi-channel, but the multi-channel is preferably used in the case of a cylindrical outer surface type.

<Development process>
The plate making method of the lithographic printing plate of the present invention uses an alkaline aqueous solution (hereinafter also referred to as “developing solution” or “processing solution”) containing a betaine surfactant and having a pH of 8.5 to 10.8. Development step of developing. When the pH is less than 8.5, the developability of the non-image area is lowered. The pH of the developer is preferably from 9.0 to 10.8, more preferably from 9.5 to 10.7.
The developer preferably contains a surfactant from the viewpoint of improving processability. Examples of the surfactant used in the present invention include anionic, nonionic, cationic, and amphoteric surfactants. Of these, amphoteric surfactants are preferred. In addition, the surfactant preferably has an HLB value of 6 or more, more preferably 8 or more, from the viewpoint of stable solubility or turbidity in water.

As well known in the field of surfactants, amphoteric surfactants are compounds having an anionic site and a cationic site in the same molecule, such as amino acids, betaines, and amine oxides. Amphoteric surfactants are included, and betaine amphoteric surfactants are preferred.
The betaine surfactant is preferably a compound represented by the formula <1> or a compound represented by the formula <2>.

In formula <1>, R ⁸ represents an alkyl group, R ⁹ and R ¹⁰ each independently represents a hydrogen atom or an alkyl group, R ¹¹ represents an alkylene group, and A represents a carboxylate ion or a sulfonate ion. To express.
In formula <2>, R ¹⁸ , R ¹⁹ and R ²⁰ each independently represents a hydrogen atom or an alkyl group. However, not all of R ¹⁸ , R ¹⁹ and R ²⁰ are hydrogen atoms.

In the above formula <1>, the alkyl group in R ⁸ , R ⁹ or R ¹⁰ and the alkylene group in R ¹¹ may be linear or branched, and may have a linking group in the chain. In addition, it may further have a substituent. As the linking group, those containing a hetero atom such as an ester bond, an amide bond, or an ether bond are preferable. Moreover, as a substituent, a hydroxyl group, ethylene oxide group, a phenyl group, an amide group, a halogen atom, etc. are preferable.
R ⁸ , R ⁹ or R ¹⁰ may be connected to each other in a cyclic manner. As a form connected cyclically, a form forming a 5-membered ring or a 6-membered ring is preferable, and it is particularly preferable that the ring is a heterocycle containing a hetero atom. As a hetero atom, an oxygen atom, a nitrogen atom, and a sulfur atom are preferable. In particular, a cation structure such as a substituted imidazole ring, a substituted imidazoline ring, and a substituted imidazolidine is preferable.
In the compound represented by the formula <1>, the total number of carbon atoms of R ^{8 to} R ¹¹ is preferably 8 to 25, and more preferably 11 to 21. Within the above range, the hydrophobic portion is appropriate and the solubility in an aqueous developer is excellent.

In the formula <2>, the alkyl group represented by R ¹⁸ , R ¹⁹ or R ²⁰ may be linear or branched, and may have a linking group in the chain. You may have. As the linking group, those containing a hetero atom such as an ester bond, an amide bond, or an ether bond are preferable. Moreover, as a substituent, a hydroxyl group, ethylene oxide group, a phenyl group, an amide group, a halogen atom, etc. are preferable.
In the compound represented by the formula <2>, the total number of carbon atoms of R ^{18 to} R ²⁰ is preferably 8 to 22, and more preferably 10 to 20. Within the above range, the hydrophobic portion is appropriate and the solubility in an aqueous developer is excellent.
It is also possible to increase the solubility of the surfactant in an aqueous developer by adding an organic solvent, for example, a solubilizing agent such as alcohol.

  The total carbon number of the amphoteric surfactant may be affected by the material used for the photosensitive layer, particularly the properties of the binder. In the case of a binder having a high degree of hydrophilicity, those having a relatively small total carbon number are preferred.

  Preferable specific examples of the amphoteric surfactant that can be used in the developer are shown below, but the present invention is not limited thereto.

Surfactants can be used alone or in combination.
The content of the surfactant in the developer is preferably from 0.01 to 10% by weight, and more preferably from 0.01 to 5% by weight.

  In order to maintain the pH of the developer at pH 8.5 to 10.8, it is preferable to add carbonate ions or hydrogen carbonate ions. Since carbonate ions and hydrogen carbonate ions are present as buffering agents, fluctuations in pH can be suppressed even when the developer is used for a long period of time, and development loss due to fluctuations in pH, development debris generation, and the like can be suppressed. In order to allow carbonate ions and hydrogen carbonate ions to be present in the developer, carbonate and hydrogen carbonate may be added to the developer, or by adjusting the pH after adding carbonate or bicarbonate, Ions and bicarbonate ions may be generated. The carbonate and bicarbonate are not particularly limited, but are preferably alkali metal salts. Examples of the alkali metal include lithium, sodium, and potassium, and sodium is particularly preferable. These may be used alone or in combination of two or more.

  The total amount of carbonate and bicarbonate is preferably 0.3 to 20% by weight, more preferably 0.5 to 10% by weight, and particularly preferably 1 to 5% by weight based on the total weight of the developer. When the total amount is 0.3% by weight or more, developability and processing capacity do not deteriorate, and when it is 20% by weight or less, it becomes difficult to form precipitates and crystals, and further, during the processing of the waste liquid of the developer, and during neutralization It becomes difficult to gel and does not interfere with waste liquid treatment.

  Further, for the purpose of assisting the fine adjustment of the alkali concentration and the dissolution of the non-image area photosensitive layer, another alkali agent such as an organic alkali agent may be supplementarily used together. Examples of the organic alkali agent include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, Examples thereof include diisopropanolamine, ethyleneimine, ethylenediamine, pyridine, tetramethylammonium hydroxide and the like. These other alkaline agents are used alone or in combination of two or more.

  In addition to the above, the developer may contain a wetting agent, preservative, chelate compound, antifoaming agent, organic acid, organic solvent, inorganic acid, inorganic salt, and the like. However, when a water-soluble polymer compound is added, the plate surface tends to become sticky especially when the developer is fatigued, so it is preferable not to add it.

Other surfactants may contain any of anionic, nonionic, and cationic types.
Anionic surfactants include fatty acid salts, abietic acid salts, hydroxyalkane sulfonates, alkane sulfonates, dialkyl sulfosuccinates, linear alkyl benzene sulfonates, branched alkyl benzene sulfonates, alkyl naphthalene sulfonates. Alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyl taurine sodium, disodium N-alkylsulfosuccinate monoamide, petroleum sulfonates, sulfate esters, Sulfuric acid ester salts, phosphoric acid ester salts, partial saponification products of styrene-maleic anhydride copolymer, partial saponification products of olefin-maleic anhydride copolymer, naphthalenesulfonic acid Formalin condensates, aromatic sulfonic acid salts, aromatic substituted polyoxyethylene sulfonic acid salts, and the like. Among these, dialkyl sulfosuccinates, alkyl sulfate esters, and alkyl naphthalene sulfonates are preferably used.

  Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.

  Nonionic surfactants include polyethylene glycol type higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, polyethylene glycol adducts of aromatic compounds, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, Higher alkylamine ethylene oxide adduct, fatty acid amide ethylene oxide adduct, oil and fat ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, dimethylsiloxane-ethylene oxide block copolymer, dimethylsiloxane- (propylene oxide-ethylene oxide) block copolymer, etc. And polyhydric alcohol glycerol fatty acid ester, pentaerythritol fatty acid ester, Rubitoru and fatty acid esters of sorbitan, fatty acid esters of sucrose, alkyl ethers of polyhydric alcohols, fatty acid amides of alkanolamines.

  As the wetting agent, ethylene glycol, propylene glycol, triethylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, diglycerin and the like are preferably used. The wetting agent may be used alone or in combination of two or more. The wetting agent is preferably used in an amount of 0.1 to 5% by weight relative to the total weight of the developer.

  Preservatives include phenol or derivatives thereof, formalin, imidazole derivatives, sodium dehydroacetate, 4-isothiazolin-3-one derivatives, benzoisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, benztriazole derivatives Amiding anidine derivatives, quaternary ammonium salts, pyridine, quinoline, guanidine and other derivatives, diazines, triazole derivatives, oxazoles, oxazine derivatives, nitrobromoalcohol-based 2-bromo-2-nitropropane-1,3diols, 1 1,1-dibromo-1-nitro-2-ethanol, 1,1-dibromo-1-nitro-2-propanol and the like can be preferably used. It is preferable to use two or more kinds of preservatives in combination so as to be effective against various molds and sterilization. The addition amount of the preservative is an amount that exhibits a stable effect on bacteria, molds, yeasts, etc., and varies depending on the types of bacteria, molds, yeasts, but is 0% relative to the total weight of the developer. A range of 0.01 to 4% by weight is preferred.

  Examples of the chelate compound include ethylenediamine disuccinate, ethylenediaminetetraacetic acid, potassium salt thereof, sodium salt thereof; diethylenetriaminepentaacetic acid, potassium salt thereof, sodium salt thereof; triethylenetetraminehexaacetic acid, potassium salt thereof, sodium salt thereof, Hydroxyethylethylenediaminetriacetic acid, potassium salt thereof, sodium salt thereof; nitrilotriacetic acid, sodium salt thereof; 1-hydroxyethane-1,1-diphosphonic acid, potassium salt thereof, sodium salt thereof; aminotri (methylenephosphonic acid), potassium thereof Mention may be made of organic phosphonic acids or phosphonoalkanetricarboxylic acids such as salts, their sodium salts and the like. An organic amine salt is also effective in place of the sodium salt and potassium salt of the chelating agent. A chelating agent is selected that is stably present in the developer composition and does not impair the printability. The addition amount is preferably 0.001 to 1.0% by weight with respect to the total weight of the developer.

  As the antifoaming agent, a general silicone-based self-emulsifying type, emulsifying type, or nonionic compound can be used, and a compound having an HLB value of 5 or less is preferable. Silicone defoamers are preferred. Among them, emulsification dispersion type and solubilization can be used. The content of the antifoaming agent is preferably in the range of 0.001 to 1.0% by weight with respect to the total weight of the developer.

  Examples of organic acids include citric acid, acetic acid, succinic acid, malonic acid, salicylic acid, caprylic acid, tartaric acid, malic acid, lactic acid, levulinic acid, p-toluenesulfonic acid, xylenesulfonic acid, phytic acid, and organic phosphonic acid. . The organic acid can also be used in the form of its alkali metal salt or ammonium salt. The content of the organic acid is preferably 0.01 to 0.5% by weight with respect to the total weight of the developer.

  Examples of the organic solvent include aliphatic hydrocarbons (hexane, heptane, “Isopar E, H, G” (Esso Chemical Co., Ltd.), gasoline, kerosene, etc.), aromatic hydrocarbons (toluene, Xylene, etc.), halogenated hydrocarbons (methylene dichloride, ethylene dichloride, trichlene, monochlorobenzene, etc.) and polar solvents.

  Polar solvents include alcohols (methanol, ethanol, propanol, isopropanol, benzyl alcohol, ethylene glycol monomethyl ether, 2-ethoxyethanol, etc.), ketones (methyl ethyl ketone, cyclohexanone, etc.), esters (ethyl acetate, methyl lactate, propylene) Glycol monomethyl ether acetate, etc.) and others (triethyl phosphate, tricresyl phosphate, N-phenylethanolamine, N-phenyldiethanolamine, etc.).

  When the organic solvent is insoluble in water, it can be used after being solubilized in water using a surfactant or the like. When the developer contains an organic solvent, the concentration of the solvent is preferably less than 40% by weight from the viewpoints of safety and flammability.

  Examples of inorganic acids and inorganic salts include phosphoric acid, metaphosphoric acid, primary ammonium phosphate, secondary ammonium phosphate, primary sodium phosphate, secondary sodium phosphate, primary potassium phosphate, secondary potassium phosphate, Examples thereof include sodium tripolyphosphate, potassium pyrophosphate, sodium hexametaphosphate, magnesium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate, sodium sulfate, potassium sulfate, ammonium sulfate, sodium sulfite, ammonium sulfite, sodium hydrogen sulfate, nickel sulfate and the like. The content of the inorganic salt is preferably 0.01 to 0.5% by weight based on the total weight of the developer.

  The development temperature is not particularly limited as long as development is possible, but it is preferably 60 ° C. or lower, more preferably 15 to 40 ° C. In the development processing using an automatic developing machine, the developing solution may be fatigued depending on the processing amount. Therefore, the processing capability may be restored using a replenishing solution or a fresh developing solution. An example of development and post-development processing is a method in which alkali development is performed, alkali is removed in a post-water washing step, gumming is performed in a gumming step, and drying is performed in a drying step. As another example, a method in which pre-water washing, development and gumming are simultaneously performed by using an aqueous solution containing carbonate ions, hydrogen carbonate ions and a surfactant can be preferably exemplified. Therefore, it is not necessary to perform the pre-water washing step, and it is preferable to perform the drying step after performing pre-water washing, development and gumming in one bath only by using one liquid. After development, it is preferable to dry after removing excess developer using a squeeze roller or the like.

  The development process can be preferably carried out by an automatic processor equipped with a rubbing member. As an automatic processor, for example, an automatic processor described in JP-A-2-220061 and JP-A-60-59351, which performs a rubbing process while conveying a lithographic printing plate precursor after image exposure, or a cylinder Examples thereof include an automatic processor described in US Pat. Nos. 5,148,746, 5,568,768 and British Patent 2,297,719, which rub the lithographic printing plate precursor after image exposure set above while rotating a cylinder. Among these, an automatic processor using a rotating brush roll as the rubbing member is particularly preferable.

The rotating brush roll used in the present invention can be appropriately selected in consideration of the difficulty of scratching the image area and the strength of the waist of the lithographic printing plate precursor. As the rotating brush roll, a known one formed by planting a brush material on a plastic or metal roll can be used. For example, a metal or plastic in which brush materials are implanted in a row, as described in JP-A-58-159533, JP-A-3-100554, or JP-A-62-167253 A brush roll in which the groove mold material is radially wound around a plastic or metal roll as a core without any gap can be used.
Examples of brush materials include plastic fibers (for example, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon 6.6 and nylon 6.10, polyacrylics such as polyacrylonitrile and poly (meth) acrylate). , Polyolefin synthetic fibers such as polypropylene and polystyrene). For example, fibers having a hair diameter of 20 to 400 μm and a hair length of 5 to 30 mm can be preferably used.
The outer diameter of the rotating brush roll is preferably 30 to 200 mm, and the peripheral speed at the tip of the brush rubbing the plate surface is preferably 0.1 to 5 m / sec. It is preferable to use a plurality of rotating brush rolls.

  The rotating direction of the rotating brush roll may be the same or opposite to the conveying direction of the lithographic printing plate precursor. However, when two or more rotating brush rolls are used, at least one rotating brush roll is used. It is preferred that the rotating brush rolls rotate in the same direction and at least one rotating brush roll rotates in the opposite direction. This further ensures the removal of the photosensitive layer in the non-image area. It is also effective to swing the rotating brush roll in the direction of the rotation axis of the brush roll.

  It is preferable to provide a drying step continuously or discontinuously after the development step. Drying is performed by hot air, infrared rays, far infrared rays, or the like.

  An example of the structure of an automatic processor suitably used in the method for producing a lithographic printing plate of the present invention is schematically shown in FIG. The automatic processor shown in FIG. 1 basically includes a developing unit 6 and a drying unit 10, and the lithographic printing plate precursor 4 performs development and gumming in the developing tank 20 and is dried in the drying unit 10.

Further, for the purpose of improving printing durability, the developed printing plate can be heated under very strong conditions. The heating temperature is usually in the range of 200 to 500 ° C. If the temperature is low, sufficient image strengthening action cannot be obtained, and if it is too high, problems such as deterioration of the support and thermal decomposition of the image area may occur.
The lithographic printing plate obtained in this way is applied to an offset printing machine and is suitably used for printing a large number of sheets.

  EXAMPLES Hereinafter, although this invention is demonstrated according to an Example, the scope of the present invention is not limited to these Examples. Unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”.

The materials used in the examples are shown below.
(Component A)
(A-1): Styrene / acrylonitrile / methacrylic acid copolymer (copolymerization ratio 69 mol% / 25 mol% / 6 mol%, weight average molecular weight 45,000)
(A-2): Styrene / acrylonitrile copolymer (copolymerization ratio 73.5 mol% / 26.5 mol%, SAN32, manufactured by Bayer)
(Component B)
(B-1): N-phenylmaleimide / methacrylic acid / methacrylamide copolymer (copolymerization ratio 60 mol% / 15 mol% / 25 mol%, weight average molecular weight = 50,000)
(B-2) Styrene / acrylonitrile / methacrylic acid copolymer (composition ratio 69 mol% / 25 mol% / 6 mol% weight average molecular weight 45,000)
(Component C)
(C-1): The following cyanine dye A

(Alkali-soluble resin)
-Polyurethane 1 (weight average molecular weight 36,000) shown below obtained by polymerizing isocyanate and diol so as to have a molar ratio of 1: 1.

M, p-cresol novolak 1 (m / p ratio = 6/4, weight average molecular weight 4,500, containing 0.8% unreacted cresol)
(Other ingredients)
・ Ethyl violet ・ Crystal violet (Hodogaya Chemical Co., Ltd.)
・ Megafac F-177 (manufactured by DIC Corporation, fluorosurfactant)

(solvent)
・ 3-pentanone ・ propylene glycol monomethyl ether-2-acetate ・ γ-butyrolactone ・ methyl ethyl ketone ・ 1-methoxy-2-propanol ・ water

Example 1
<Production of support>
0.24 mm thick aluminum plate (Si: 0.06%, Fe: 0.30%, Cu: 0.014%, Mn: 0.001%, Mg: 0.001%, Zn: 0.001% , Ti: 0.03%, and the balance was continuously subjected to the following surface treatment on Al and an inevitable impurity aluminum alloy).

An electrochemical surface roughening treatment was continuously performed using an alternating voltage of 60 Hz. The electrolytic solution at this time was a nitric acid 10 g / liter aqueous solution (containing 5 g / liter of aluminum ions and 0.007% ammonium ions) at a temperature of 80 ° C. After washing with water, the aluminum plate was etched by spraying at a caustic soda concentration of 26% and an aluminum ion concentration of 6.5% at 32 ° C., 0.20 g / m ^{2 of the} aluminum plate was dissolved, and then washed with water by spraying. Thereafter, a desmut treatment by spraying was performed with a 25% sulfuric acid concentration aqueous solution (containing 0.5% of aluminum ions) at a temperature of 60 ° C., and washing with water was performed.

Anodization was performed using an anodizing apparatus of a two-stage power supply electrolytic treatment method. Sulfuric acid was used as the electrolytic solution supplied to the electrolysis unit. Then, water washing by spraying was performed. The final oxide film amount was 2.7 g / m ² .
The aluminum support obtained by the anodic oxidation treatment was immersed in a treatment tank of 1% aqueous solution of sodium silicate No. 3 at a temperature of 30 ° C. for 10 seconds to perform alkali metal silicate treatment (silicate treatment). . Then, water washing by spraying was performed.

On the aluminum support after the alkali metal silicate treatment obtained as described above, an undercoat solution having the following composition was applied and dried at 80 ° C. for 15 seconds to form a coating film. The coating amount of the coating film after drying was 15 mg / m ² .
-Undercoat liquid-
・ Β-Alanine 0.5 part ・ Methanol 95 parts ・ Water 5 parts

<Formation of recording layer>
The lower layer coating solution 1 having the following composition was coated on the support obtained as described above with a bar coater so that the coating amount became 1.5 g / m ² , dried at 160 ° C. for 44 seconds, and immediately subjected to 17-20 ° C. The support was cooled to 35 ° C. with cold air.
-Lower layer coating solution 1-
Water-insoluble and alkali-soluble resin (b) -1 (N-phenylmaleimide / methacrylic acid / methacrylamide copolymer) 5.21 parts Cyanine dye A 0.94 parts Crystal violet (manufactured by Hodogaya Chemical Co., Ltd.) 08 parts ・ Megafac F-177 (manufactured by DIC Corporation, fluorosurfactant) 0.05 parts ・ γ-butyrolactone 10 parts ・ methyl ethyl ketone 61 parts ・ 1-methoxy-2-propanol 14 parts ・ water 9.34 Part

Then, after coating the upper layer coating solution 1 having the following composition with a bar coater so that the coating amount becomes 0.5 g / m ² , the coating solution is dried at 130 ° C. for 40 seconds, and further slowly cooled with air at 20 to 26 ° C. The planographic printing plate precursor of Example 1 was prepared.
-Coating liquid for upper layer 1-
Styrene / acrylonitrile / methacrylic acid copolymer (composition ratio 69 mol% / 25 mol% / 6 mol%, weight average molecular weight 45,000) 20 parts Alkali-soluble resin: 10 parts of the polyurethane 1 Ethyl violet 0.03 parts Megafac F -177 (manufactured by DIC Corporation, fluorosurfactant) 0.05 parts, 3-pentanone 60 parts, propylene glycol monomethyl ether-2-acetate 8 parts

(Plate making and evaluation of planographic printing plate precursor)
Using the obtained lithographic printing plate precursors of Examples 1 to 5 and the lithographic printing plate precursors of Comparative Examples 1 and 2, after performing the plate making process by the exposure step and the development step according to the production method of the present invention, the following Each evaluation shown in FIG. The details of the exposure process, development process, and evaluation method applied to each evaluation are as follows. The evaluation results are shown in Table 1.

1. Evaluation of development residue adhesion during large-scale plate making (exposure process)
The obtained lithographic printing plate precursor of Example 1 was cut into a size of 1,030 mm × 800 mm, and the exposure energy was 150 mJ / cm ² using an infrared semiconductor laser (Trendsetter 3244VX manufactured by Creo: equipped with a water-cooled 40 W infrared semiconductor laser). A test pattern was drawn in an image.

(Development process)
Thereafter, using a specific developer A having the following composition, an automatic developing processor (developing tank 25L, plate conveyance speed 100 cm / min, outer diameter in which polybutylene terephthalate fibers (hair diameter 200 μm, hair length 17 mm) are implanted as shown in FIG. One 50 mm brush roll was developed at 200 revolutions per minute in the same direction as the transport direction (peripheral speed of brush tip 0.52 m / sec), drying temperature 80 ° C.) to obtain a lithographic printing plate .

(Composition of specific developer A)
-Water 796 parts-Sodium carbonate 12.8 parts-Sodium hydrogen carbonate 7.0 parts-Sodium gluconate 15.5 parts-Softazoline LPB-R (30% aqueous solution) 154.0 parts-Softazoline LAO (30% aqueous solution) 38 0.0 part ethylenediamine disuccinate 6.7 parts pH 9.85

  The exposure process and the development process described above were performed continuously at 100 plates / day for 5 days. Thereafter, the automatic development processor was stopped for 3 days and then restarted, and exposure processing and development processing were performed under the same exposure processing and development processing conditions as described above. About the whole area of the non-image part formed in the 1st lithographic printing plate after restart, the number of deposits resulting from the deposit which generate | occur | produced in the developing tank of an automatic processor was visually counted. The results are shown in Table 1.

2. Development evaluation using a lithographic printing plate precursor subjected to forced aging (exposure process)
The obtained lithographic printing plate precursors of Examples 1 to 5 and the lithographic printing plate precursors of Comparative Examples 1 and 2 were cut into 500 mm × 600 mm, and protective scissors were put between the lithographic printing plate precursors. However, it was set as the laminated body which piled up 30 sheets. Thereafter, the upper and lower sides of the laminate were sandwiched with cardboard laminated with polyethylene, and packaged so as to block outside air with aluminum kraft paper. The packaged product was placed in a Thermocelco (Enomoto Kasei Co., Ltd., FX224P type) at 40 ° C. for 24 hours, and then subjected to power exposure at intervals of 0.5 W from 0 W to 10 W using a Trend setter manufactured by Creo.

(Development process)
Thereafter, development processing was performed in the same manner as in the evaluation of development residue adhesion to obtain a lithographic printing plate.
Each lithographic printing plate after the development treatment was visually observed with a magnifying glass to determine how many W the non-image area was completely exposed. Hereinafter, the exposure amount at which the non-image part is completely exposed is referred to as clear sensitivity. At this time, the clear sensitivity (W) was similarly determined for the lithographic printing plate precursor not placed in the thermocelco at 40 ° C., and the clear sensitivity difference between the one put in the thermocellco and the one not put in was found.
The smaller the clear sensitivity difference, the better the developability. The results are shown in Table 1.

(Examples 2 to 5 and Comparative Examples 1 and 2)
The lithographic printing plate precursors of Examples 2 to 5 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the upper layer coating solution and the lower layer coating solution were changed to the compositions shown in Table 1. .

(Examples 6 and 7 and Comparative Examples 3 and 4)
Evaluation was conducted in the same manner as in Example 1 except that the developer A used in Example 1 was changed to the developers B to E. The evaluation results are shown in Table 2.

The surfactants listed in Table 2 are as follows.
Softazoline LPB-R (30%): lauric acid amidopropyl betaine aqueous solution (manufactured by Kawaken Fine Chemical Co., Ltd.)
-Softazoline LAO (30%): Lauramidopropylamine oxide aqueous solution (manufactured by Kawaken Fine Chemical Co., Ltd.)
・ Takesurf C-157-L: 30% by weight aqueous solution of amphoteric surfactant (W-2) (manufactured by Takemoto Yushi Co., Ltd.)

  From the results of the table, according to the plate making method of the lithographic printing plate of the present invention, there is no residue in the developing tank despite the one-bath treatment with a weakly alkaline developer, which is excellent in processability. Furthermore, there is almost no decrease in printing durability due to the plate after development.

It is explanatory drawing which shows the structure of an automatic developing processor.

4 Planographic printing plate precursor 6 Developing unit 10 Drying unit 16 Transport roller 20 Developing tank 22 Transport roller 24 Brush roller 26 Squeeze roller 28 Backup roller 36 Guide roller 38 Skewer roller

Claims (10)

On the support, (Component A) a copolymer containing a structural unit derived from (meth) acrylonitrile and a structural unit derived from styrene, (Component B) a water-insoluble and alkali-soluble resin, and (Component C) infrared An exposure step of image-exposing a positive planographic printing plate precursor for infrared laser, comprising a positive recording layer containing an absorbent, and having improved solubility in an aqueous alkali solution by exposure or heating; and
A plate making method of a lithographic printing plate comprising a development step in which a betaine surfactant is contained and development is performed using an alkaline aqueous solution having a pH of 8.5 to 10.8. The plate making method of a lithographic printing plate according to claim 1, wherein the alkaline aqueous solution contains a compound represented by the formula <1> and / or a compound represented by the formula <2>.

(In formula <1>, R ⁸ represents an alkyl group, R ⁹ and R ¹⁰ each independently represents a hydrogen atom or an alkyl group, R ¹¹ represents an alkylene group, and A represents a carboxylate ion or a sulfonate ion. In formula <2>, R ¹⁸ , R ¹⁹ and R ²⁰ each independently represent a hydrogen atom or an alkyl group, provided that all of R ¹⁸ , R ¹⁹ and R ²⁰ are hydrogen atoms. Absent.)   The lithographic printing plate making method according to claim 1 or 2, wherein the aqueous alkaline solution contains a combination of carbonate ions and hydrogen carbonate ions.   The lithographic printing plate making method according to any one of claims 1 to 3, wherein the development step is a step of performing development and gumming in one bath.   The lithographic printing plate making method according to any one of claims 1 to 4, wherein a water washing step is not performed before and after the developing step.   The lithographic printing plate according to any one of claims 1 to 5, wherein the positive recording layer is a layer comprising an upper layer containing the component A and a lower layer containing the component B and the component C. Plate making method.   The lithographic printing plate making method according to any one of claims 1 to 6, wherein the upper layer further contains an alkali-soluble resin.   The component B is a copolymer including a structural unit derived from N-substituted maleimide, a structural unit derived from (meth) acrylamide, and a structural unit derived from (meth) acrylic acid. A method for making a lithographic printing plate according to any one of the above.   The lithographic printing plate making method according to any one of claims 1 to 8, wherein the component C is a cyanine dye. A lithographic printing plate produced by the lithographic printing plate making method according to any one of claims 1 to 9.

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