JP5496702B2 - Preparation method of lithographic printing plate - Google Patents

Description

  The present invention relates to a method for producing a lithographic printing plate, and more particularly to a method for producing a lithographic printing plate having excellent processability.

In general, a lithographic printing plate comprises an oleophilic image area that receives ink in the printing process and a hydrophilic non-image area that receives dampening water. Lithographic printing utilizes the property that water and printing ink repel each other, so that the oleophilic image area of the lithographic printing plate is the ink receiving area and the hydrophilic non-image area is dampened with the water receiving area (ink non-receiving area). As described above, a difference in ink adhesion is caused on the surface of a lithographic printing plate, and after ink is applied only to an image portion, the ink is transferred to a printing medium such as paper and printed.
In order to produce this lithographic printing plate, a lithographic printing plate precursor (PS plate) in which an oleophilic photosensitive resin layer (photosensitive layer, image recording layer) is provided on a hydrophilic support has been widely used. Yes. Usually, after the exposure process in which the lithographic printing plate precursor is subjected to image-like exposure through an original image such as a lithographic film, the image portion of the image recording layer remains, and other unnecessary image recording layers are formed. A lithographic printing plate is obtained by carrying out a development step of dissolving and removing with an alkaline developer or an organic solvent, and performing plate making by a method of forming a non-image portion by exposing the surface of the hydrophilic support.

  Thus, in the plate making process of the conventional lithographic printing plate precursor, after the exposure, a developing process for dissolving and removing unnecessary image recording layers with a developer or the like is required. It is desired to use an aqueous solution closer to the neutral range as an alkaline aqueous solution used in the above, or to reduce waste liquid in the development process. In particular, in recent years, disposal of waste liquid discharged with wet processing has become a major concern for the entire industry due to consideration for the global environment, and the demand for solving the above-mentioned problems has become stronger.

  On the other hand, in recent years, digitization technology for electronically processing, storing, and outputting image information by a computer has become widespread, and various new image output methods corresponding to such digitization technology will be put into practical use. It is becoming. Along with this, digitized image information is carried by high-convergence radiation such as laser light, and the lithographic printing plate precursor is scanned and exposed with the light, and directly through the lithographic printing plate Computer-to-plate (CTP) technology has been attracting attention. In particular, image recording materials compatible with infrared lasers have become widespread because they can be handled even under white light. As such an image recording material, a positive type image recording material utilizing a dissolution inhibiting effect on a developing solution expressed by an infrared absorbing dye having a photothermal conversion action and a phenol resin is attracting attention.

Usually, such a positive type image recording material is improved by the development process by eliminating the dissolution suppressing action in the exposed area by the infrared laser exposure and the heat generated by the photothermal conversion agent, thereby improving the solubility of the image recording layer. The area is removed and a lithographic printing plate is made. After the development, generally, a water washing treatment is performed to remove excess alkali developer, and then the lithographic printing plate is subjected to printing by gumming.
The development processing is usually performed in an automatic developing machine. However, when the image recording layer dissolved in the developer increases, the image is deposited and becomes development residue. When the development debris is remarkably generated, there is a concern that it may adhere to the lithographic printing plate after plate making and cause image failure. In particular, since a relatively high molecular weight photothermal conversion agent is used in the image recording layer corresponding to the infrared laser, there is a tendency that development residue is easily generated.

Furthermore, as an alkaline developer used in the development step, it is preferable to bring the pH close to neutral from the viewpoint of the environment, and various attempts have been made. For example, a plate making method has been proposed in which a lithographic printing plate precursor having a positive image recording layer having a multilayer structure is treated with a developer having a pH of 6 to 11 (see, for example, Patent Document 1). However, only by keeping the pH of the alkaline developer low, there is a problem in that when the plate is repeatedly made by an automatic processor, developability, in other words, development residue increases due to a decrease in solubility of the image recording layer. It has been found that there is a concern that the development residue may adhere to the plate surface and cause image failure.
Furthermore, in a lithographic printing plate, in order to increase the hydrophilicity of the non-image area and protect the plate surface, it is usually preferable to perform a hydrophilic treatment called a gumming treatment on the plate surface after development and washing with water. Since the processing is also a wet processing, there is a problem of waste liquid as in the development process.

International Publication No. 2009 / 094120A1 Pamphlet

The object of the present invention made in consideration of the above-mentioned problems is lithographic printing which has excellent developability and suppresses the development debris over time even when a relatively low pH alkaline developer is used. It is to provide a method for producing a plate.
It is a further object of the present invention to provide a method for preparing a lithographic printing plate that can be made by a one-bath treatment without requiring a water washing step or a gumming step after the development step with an alkaline aqueous solution.

The object of the present invention is achieved by the following means.
<1> On a support, (A) a water-insoluble and alkali-soluble resin, and (B) a lower layer containing an infrared absorber, (C) a water-insoluble and alkali-soluble polyurethane resin, and (D) a polyorganosiloxane. An exposure step for image exposure of a positive planographic printing plate precursor comprising an image recording layer having an upper layer,
A method for preparing a lithographic printing plate comprising a development step of developing an image-exposed positive lithographic printing plate precursor using an alkaline aqueous solution containing an anionic surfactant having a pH of 8.5 to 10.8 in this order.

<2> The (A) water-insoluble and alkali-soluble resin contains one or more selected from the group consisting of a phenolic hydroxyl group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a sulfonamide group, and an active imide group. The method for producing a lithographic printing plate according to <1>, which is a resin.
<3> The method for producing a lithographic printing plate according to <1> or <2>, wherein the (B) infrared absorber is a cyanine dye.

<4> The water-insoluble and alkali-soluble polyurethane resin (C) is a polyurethane resin having a carboxy group bonded to the polymer main chain through a single bond or a divalent linking group. <1> to <3> A method for producing a lithographic printing plate according to any one of the above.
<5> The (C) water-insoluble and alkali-soluble polyurethane resin comprises a diisocyanate compound represented by the following general formula (I) and a carboxy group represented by the following general formula (II) or general formula (III): The method for preparing a lithographic printing plate according to any one of <1> to <4>, which is a polyurethane resin having a reaction product of at least one diol compound having a basic skeleton as a basic skeleton.

[In General Formula (I), R ¹ represents a divalent linking group. In the general formula (II), R ² represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, an alkoxy group or an aryloxy group. In general formula (II) or (III), R ³ , R ⁴ , and R ⁵ may be the same or different and each represents a single bond or a divalent linking group. In general formula (III), Ar represents a trivalent aromatic hydrocarbon which may have a substituent. ]
< 6 > The method for producing a lithographic printing plate according to any one of <1> to < 5 >, wherein the upper layer further contains (B) an infrared absorber.

< 7 > The method for producing a lithographic printing plate according to any one of <1> to < 6 >, wherein the content of the water-soluble polymer compound in the alkaline aqueous solution is 10 ppm or less.
< 8 > The development step is a step in which the water washing step and the gumming step are not required as separate steps, and pre-water washing, development, and gumming are performed in one bath using the alkaline aqueous solution <1> to < 7 >. A method for producing a lithographic printing plate according to any one of the above.

According to the present invention, it is possible to provide a method for preparing a lithographic printing plate that is excellent in developability even when a relatively low pH alkaline developer is used, and that suppresses the development debris over time. it can.
Further, according to the present invention, it is possible to provide a method for preparing a lithographic printing plate capable of making a plate by one bath treatment without requiring a water washing step or a gumming step after the development step with an alkaline aqueous solution.

It is a schematic sectional drawing which shows the one aspect | mode of the structure of the automatic processor which can be used for the preparation method of the lithographic printing plate of this invention.

Hereinafter, a method for producing a planographic printing plate of the present invention will be described in detail.
The method for producing a lithographic printing plate of the present invention comprises: (A) a water-insoluble and alkali-soluble resin, and (B) a lower layer containing an infrared absorber on a support; and (C) a water-insoluble and alkali-soluble polyurethane resin. And (D) an exposure step of image-exposing a positive lithographic printing plate precursor comprising an image recording layer having an upper layer containing polyorganosiloxane, an image-exposed positive lithographic printing plate precursor containing an anionic surfactant A developing step of developing using an alkaline aqueous solution of pH 8.5 to 10.8 is included in this order.
Hereinafter, the constitution of the lithographic printing plate precursor to which the production method of the present invention can be applied, the exposure process, and the development process will be described in order.

<Lithographic printing plate precursor>
The lithographic printing plate precursor used in the production method of the present invention comprises, on a support, (A) a water-insoluble and alkali-soluble resin, and (B) a lower layer containing an infrared absorber, and (C) a water-insoluble and alkali-soluble material. A positive lithographic printing plate precursor comprising an image recording layer having a polyurethane resin and an upper layer containing (D) polyorganosiloxane.

The image recording layer in the present invention will be described below. The image recording layer of the present invention has a lower layer and an upper layer.
First, the components contained in the lower layer and the upper layer will be described in order.

<(A) Water-insoluble and alkali-soluble resin>
The (A) water-insoluble and alkali-soluble resin that can be used in the lower layer in the present invention is not particularly limited as long as it is insoluble in water and has a property of dissolving when contacted with an alkaline developer. A homopolymer containing an acidic group in the main chain and / or side chain thereof, a copolymer thereof, or a mixture thereof is preferable.
Examples of the alkali-soluble resin having such an acidic group include —COOH, —SO ₃ H, —OSO ₃ H, —PO ₃ H ₂ , —OPO ₃ H ₂ , —CONHSO ₂ , —SO ₂ NHSO ₂ —, phenol. A functional group such as —COOH, —SO ₃ H, —OPO ₃ H ₂ , —SO ₂ NHSO ₂ —, etc., particularly preferably —COOH.

Accordingly, such a resin is suitably obtained by polymerizing a mixture containing a monomer containing one or more ethylenically unsaturated monomers having the above functional group (hereinafter also referred to as “monomer that imparts alkali solubility”). be able to. The monomer imparting alkali solubility includes, in addition to acrylic acid and methacrylic acid, a compound represented by the following formula and a mixture thereof. Each R ⁴ in the following formula is a hydrogen atom or CH ₃ .
In this specification, when referring to either or both of acrylate and methacrylate, (meth) acrylate and when referring to either or both of acryl and methacryl may be described as (meth) acryl.

  The (A) water-insoluble and alkali-soluble resin in the lower layer of the present invention is preferably a polymer compound obtained by copolymerizing other polymerizable monomers in addition to a monomer that imparts alkali solubility. As a copolymerization ratio in this case, it is preferable to contain the monomer which provides alkali solubility 10 mol% or more and 70 mol% or less, and what contains 20 mol% or more is more preferable. When the copolymerization component of the monomer imparting alkali solubility is within this range, it is insoluble in water and becomes soluble in an alkaline developer, resulting in good developability.

Here, as the other polymerizable monomer (A) that can be used for the preparation of the water-insoluble and alkali-soluble resin, the following compounds can be exemplified.
Alkyl acrylates and alkyl methacrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. Acrylic acid esters and methacrylic acid esters having an aliphatic hydroxyl group such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate. Acrylamide or methacrylamide such as acrylamide, methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-phenylacrylamide, etc. Vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl butyrate and vinyl benzoate. Styrenes such as styrene, α-methylstyrene, methylstyrene, and chloromethylstyrene. Other nitrogen atom-containing monomers such as N-vinylpyrrolidone, N-vinylpyridine, acrylonitrile and methacrylonitrile. N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-phenylmaleimide, N-2-methylphenylmaleimide, N-2,6-diethylphenylmaleimide, N-2-chlorophenylmaleimide, Maleimides such as N-cyclohexylmaleimide, N-laurylmaleimide, N-hydroxyphenylmaleimide and the like.
Among these other ethylenically unsaturated comonomer monomers, (meth) acrylic acid esters, (meth) acrylamides, maleimides, and (meth) acrylonitrile are preferably used.

  Specific examples of the copolymer of (A) water-insoluble and alkali-soluble resin are shown below. The weight average molecular weights of the following specific examples are all in the range of 20000 to 50000. However, the present invention is not limited by the following specific examples.

  As another form of (A) water-insoluble and alkali-soluble resin, a resin having a phenolic hydroxyl group is also preferable. Examples of the resin having a phenolic hydroxyl group include phenol formaldehyde resin, m-cresol formaldehyde resin, p-cresol formaldehyde resin, m- / p-mixed cresol formaldehyde resin, phenol / cresol (m-, p-, or m- Any of / p-mixing may be used) and novolak resins such as mixed formaldehyde resins.

Further, a t-butylphenol formaldehyde resin described in US Pat. No. 4,123,279 or a condensate of phenol and formaldehyde having an alkyl group having 3 to 8 carbon atoms as a substituent, such as octylphenol formaldehyde resin, is used in combination. Also good.
These resins having a phenolic hydroxyl group may be used alone or in combination of two or more.

  The (A) water-insoluble and alkali-soluble resin used in the lower layer of the image recording layer in the present invention preferably has a weight average molecular weight of 2,000 or more and a number average molecular weight of 500 or more, and a weight average molecular weight of 5,000 to 300. The number average molecular weight is 800 to 250,000, and the dispersity (weight average molecular weight / number average molecular weight) is more preferably 1.1 to 10. As these molecular weight values, values calculated in terms of molecular weight of polystyrene standards by GPC (gel permeation chromatography) measurement are used.

The (A) water-insoluble and alkali-soluble resin used for the lower layer of the image recording layer in the present invention may be one type, or two or more types.
The content of the (A) water-insoluble and alkali-soluble resin in the total solid content of the lower layer of the image recording layer is preferably 50 to 98% by mass, more preferably 65 to 95% by mass. (A) When the content of the water-insoluble and alkali-soluble resin is within this range, the sensitivity of the image recording layer is high and the durability is good.

<(B) Infrared absorber>
The lower layer of the image recording layer in the present invention contains (B) an infrared absorber. (B) The infrared absorber is not particularly limited as long as it is a dye or pigment that absorbs infrared light and generates heat, and various dyes or pigments known as infrared absorbers can be used.

  Examples of such dyes as infrared absorbers include cyanine described in JP-A-58-125246, JP-A-59-84356, JP-A-59-202829, JP-A-60-78787, and the like. Dyes, methine dyes described in JP-A-58-173696, JP-A-58-181690, JP-A-58-194595, etc., JP-A-58-112793, JP-A-58-224793, Naphthoquinone dyes described in JP-A-59-48187, JP-A-59-73996, JP-A-60-52940, JP-A-60-63744, etc., described in JP-A-58-112792, etc. And the cyanine dye described in British Patent 434,875.

As the dye as the infrared absorber, a near infrared absorption sensitizer described in US Pat. No. 5,156,938 is also preferably used, and a substituted dye described in US Pat. No. 3,881,924 is used. Arylbenzo (thio) pyrylium salt, trimethine thiapyrylium salt described in JP-A-57-142645 (US Pat. No. 4,327,169), JP-A-58-181051, 58-220143, 59 No. 41363, 59-84248, 59-84249, 59-146063, 59-146061, cyanine dyes described in JP-A-59-216146, US patents No. 4,283,475, the pentamethine thiopyrylium salt and the like disclosed in Japanese Patent Publication Nos. 5-13514 and 5-19702. Potassium compounds, etc., as commercially available products, Eporin Co. Epolight III-178, 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.

Preferred infrared absorbers for the lower layer of the image recording layer in the invention are preferably the following compounds.
Of these, particularly preferred infrared absorber dyes are cyanine dyes A and F.

Cyanine dye F

  In addition, as pigments, commercially available pigments and color index (CI) manual, “Latest Pigment Handbook” (edited by Japan Pigment Technology Association, published in 1977), “Latest Pigment Applied Technology” (published by CMC, published in 1986) For example, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments , Isoindolinone pigments, quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black and the like, and carbon black is particularly preferably used.

By including the infrared absorber in the lower layer of the image recording layer, the balance between the sensitivity and the ablation resistance during image recording is improved.
As addition amount of an infrared absorber, 0.01-50 mass% with respect to the total solid in a lower layer
, Preferably 0.1 to 30% by mass, particularly preferably 1.0 to 30% by mass. By setting the content in this range, sufficient sensitivity can be obtained while lowering the reaching temperature of the upper layer during image recording and suppressing ablation.
The lower layer of the image recording layer can further contain other additives described later.

<(C) Water-insoluble and alkali-soluble polyurethane resin>
The upper layer of the image recording layer in the invention contains (C) a water-insoluble and alkali-soluble polyurethane resin.
The polyurethane resin contained in the upper layer is not particularly limited as long as it is insoluble in water and soluble in an alkaline aqueous solution, but among them, it is bonded to the polymer main chain with a single bond or a divalent linking group. Those having a carboxy group are preferred. Specifically, a diisocyanate compound represented by the following general formula (I) and a diol compound having a carboxy group represented by the following general formula (II) or general formula (III) And a polyurethane resin having a reaction product of at least one of the above as a basic skeleton.

In general formula (I), R ¹ represents a divalent linking group.
Examples of the divalent linking group that R ¹ can take include aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons, preferably alkylene groups having 2 to 10 carbon atoms, and 6 to 30 carbon atoms. Of the arylene group.
R ¹ may have another functional group that does not react with the isocyanate group.

In the general formula (II), R ² represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, an alkoxy group or an aryloxy group. Here, R ² may have a substituent.
Preferable R ² includes a hydrogen atom, an unsubstituted alkyl group having 1 to 8 carbon atoms, and an unsubstituted aryl group having 6 to 15 carbon atoms.
In general formula (II) or (III), R ³ , R ⁴ , and R ⁵ may be the same or different and each represents a single bond or a divalent linking group.
Examples of the divalent linking group that R ³ , R ⁴ , and R ⁵ can take include aliphatic hydrocarbons and aromatic hydrocarbons. Here, R ³ , R ⁴ , and R ⁵ may have a substituent. Preferred examples of R ³ , R ⁴ , and R ⁵ include an unsubstituted alkylene group having 1 to 20 carbon atoms and an unsubstituted arylene group having 6 to 15 carbon atoms. ˜8 unsubstituted alkylene groups.
R ³ , R ⁴ , and R ⁵ may have another functional group that does not react with the isocyanate group.
In general formula (III), Ar represents a trivalent aromatic hydrocarbon which may have a substituent, and preferably an arylene group having 6 to 15 carbon atoms.

Specific examples of the diisocyanate compound represented by the general formula (I) include those shown below, but the present invention is not limited thereto.
2,4-tolylene diisocyanate, dimer of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-xylylene diisocyanate, metaxylylene diisocyanate, 4,4'-diphenylmethane Aromatic diisocyanate compounds such as diisocyanate, 1,5-naphthylene diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate; hexamethylene diisocyanate, trimethylhexamethylene diisocyanate Aliphatic diisocyanate compounds such as narate, lysine diisocyanate, dimer acid diisocyanate; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4 (or 2,6 ) Diisocyanate, 1,3- (isocyanate) An alicyclic diisocyanate compound such as natomethyl) cyclohexane; a diisocyanate which is a reaction product of a diol and a diisocyanate such as an adduct of 1 mol of 1,3-butylene glycol and 2 mol of tolylene diisocyanate Compounds and the like.
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 the general formula (II) or (III) include those shown below, but the present invention is not limited thereto.
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 and the like.
Among these, 2,2-bis (hydroxymethyl) propionic acid and 2,2-bis (hydroxyethyl) propionic acid are preferable from the viewpoint of reactivity with isocyanate.

The (C) water-insoluble and alkali-soluble polyurethane resin according to the present invention is prepared by adding the above-mentioned diisocyanate compound and diol compound to an aprotic solvent and adding a known catalyst having an activity corresponding to the respective reactivity. Can be synthesized.
The molar ratio of the diisocyanate to be used and the diol compound is preferably 0.8: 1 to 1.2: 1, and when an isocyanate group remains at the polymer terminal, it is treated with an alcohol or an amine. As a result, the compound is finally synthesized in a form in which no isocyanate group remains.
The (C) water-insoluble and alkali-soluble polyurethane resin according to the present invention preferably has an aromatic skeleton from the viewpoint of chemical resistance.

  Specific examples of the water-insoluble and alkali-soluble polyurethane resin (C) in the present invention include the following reactants of isocyanate compounds and diol compounds. The composition ratio can be freely set as long as it can be synthesized and can maintain alkali solubility.

  Of these, 1, 3, 4, 7, 8, 9, 11, 13, 15, 18, 20, 21 are particularly preferable.

  The molecular weight of the (C) water-insoluble and alkali-soluble polyurethane resin according to the present invention is preferably 1,000 or more in terms of weight average molecular weight, and more preferably in the range of 5,000 to 100,000. These (C) water-insoluble and alkali-soluble polyurethane resins may be used alone or in admixture of two or more.

  The content of these polyurethane resins contained in the upper layer component according to the present invention is preferably 2 to 99.5% by mass, more preferably 5 to 99% by mass, and particularly preferably 10 to 10% by mass in the total solid content of the upper layer. It is 98 mass%. By setting the amount within this range, the balance between the effect of suppressing development residue with time, the image forming property, and the printing durability is improved.

<(D) Polyorganosiloxane>
The upper layer of the image recording layer used in the present invention contains (D) polyorganosiloxane.
(D) The polyorganosiloxane is not particularly limited as long as it contains a non-polar part composed of siloxane and a polar part having an oxygen atom, for example, polyether-modified polyorganosiloxane, alcohol-modified polyorgano Siloxane, carboxyl-modified polyorganosiloxane, and the like can be used.

As a specific example of such a polyorganosiloxane, a polyorganosiloxane produced by hydrolytic condensation of an alkoxysilane in a compound represented by the following general formula is preferable.
RSi (OR ') ₃
[In the above formula, R represents an alkyl group or an aryl group, and R ′ represents an alkyl group. ]
Of the above general formulas R, preferred is a phenyl group. Preferable R ′ is a methyl group, an ethyl group, and a propyl group, and R ′ may be the same or different.
Further, a graft block polysiloxane represented by the following formula (1) and a block polysiloxane represented by the formula (2) are also preferably used.
In the following formulas (1) and (2), n, p, and q are each independently an integer of 1 or more.

A specific production method of the organopolysiloxane resin is described in WO2000 / 035994.
Examples of commercially available polyorganosiloxanes include polyether-modified polydimethylsiloxane BYK-333 (manufactured by BYK Chemie) and polysiloxane polyether copolymer TEGO Glide 410 (available from TegoChemie Service GmbH). It is done.

The content of (D) polyorganosiloxane contained in the upper layer of the image recording layer according to the present invention is preferably 0.01 to 10% by mass, more preferably 0.03 to 5% by mass in the total solid content of the upper layer. Especially preferably, it is 0.1-3 mass%.
By setting it within this range, scratch resistance is improved by a low coefficient of friction, and dispersion of a polyurethane resin as a dispersant in the developer is promoted, and an effect of suppressing development residue with time can be obtained.

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 express alkali solubility particularly in the non-image 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 water-insoluble and alkali-soluble resins.
Examples of the water-insoluble and alkali-soluble resin that may be added to the upper layer include (A) the water-insoluble and alkali-soluble resin described as an essential component in the lower layer. The structure may be the same as or different from the lower layer.
In addition, the content of the water-insoluble and alkali-soluble resin is preferably 50% or less in terms of mass with respect to the (C) water-insoluble and alkali-soluble polyurethane resin.

  Furthermore, an infrared absorber can be added to the upper layer component according to the present invention within a range not impairing the effects of the present invention. By adding to the upper layer, thermal diffusion to a metal substrate having high thermal conductivity during exposure can be suppressed, resulting in high sensitivity. (B) Those described in the infrared absorber can be used in the same manner.

[Other ingredients]
The upper and lower layers of the image recording layer in the present invention can contain other additives depending on the purpose, if desired.
Examples of other components include various additives such as onium salts, o-quinonediazide compounds, aromatic sulfone compounds, aromatic sulfonic acid ester compounds, and the like (A) Examples thereof include substances that substantially reduce the solubility of water-insoluble and alkali-soluble resins. By using the additive, it is possible to improve the dissolution inhibition property of the image portion in the developer.

Examples of the onium salt include diazonium salt, ammonium salt, phosphonium salt, iodonium salt, sulfonium salt, selenonium salt, arsonium salt and the like.
Examples of onium salts include S.I. I. Schlesinger, Photogr. Sci. Eng. , 18, 387 (1974), T.A. S. Bal et al, Polymer, 21, 423 (1980), diazonium salts described in JP-A-5-158230, U.S. Pat. Nos. 4,069,055, 4,069,056, and JP-A-3-140140. Ammonium salts described in the specification of C. Necker et al, Macromolecules, 17, 2468 (1984), C.I. S. Wen et al, Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988), U.S. Pat. Nos. 4,069,055 and 4,069,056; V. Crivello et al, Macromolecules, 10 (6), 1307 (1977), Chem. &Amp; Eng. News, Nov. 28, p31 (1988), European Patent No. 104,143, U.S. Pat. Nos. 339,049, 410,201, JP-A-2-150848, JP-A-2-296514,

J. et al. V. Crivello et al, Polymer J. et al. 17, 73 (1985), J. Am. V. Crivello et al. J. et al. Org. Chem. 43, 3055 (1978); R. Watt et al. Polymer Sci. , Polymer Chem. Ed. , 22, 1789 (1984), J. Am. V. Crivello et al, Polymer Bull. 14, 279 (1985), J. Am. V. Crivello et al, Macromolecules, 14 (5), 1141 (1981), J. MoI. V. Crivello et al, J.A. Polymer Sci. , Polymer Chem. Ed. 17, 2877 (1979), European Patents 370,693, 233,567, 297,443, 297,442, U.S. Pat. Nos. 4,933,377, 3,902,114 Nos. 410, 201, 339, 049, 4,760, 013, 4, 734, 444, 2, 833, 827, German Patent No. 2,904, 626, Sulfonium salts described in JP-A Nos. 3,604,580 and 3,604,581; V. Crivello et al, Macromolecules, 10 (6), 1307 (1977), J. MoI. V. Crivello et al, J.A. Polymer Sci. , Polymer Chem. Ed. , 17, 1047 (1979), a selenonium salt described in C.I. S. Wen et al, Teh, Proc. Conf. Rad. Preferred examples include arsonium salts described in Curing ASIA, p478 Tokyo, Oct (1988).
Among these, a diazonium salt is particularly preferable, and the diazonium salt described in JP-A-5-158230 is preferable.

  Counter ions of onium salts include tetrafluoroboric acid, hexafluorophosphoric acid, triisopropylnaphthalenesulfonic acid, 5-sulfosalicylic acid, 2,5-dimethylbenzenesulfonic acid, 2,4,6-trimethylbenzenesulfonic acid 2-nitrobenzenesulfonic acid, 3-bromobenzenesulfonic acid, 2-fluorocaprylnaphthalenesulfonic acid, dodecylbenzenesulfonic acid, 1-naphthol-5-sulfonic acid, 2-methoxy-4-hydroxy-5-benzoyl-benzenesulfone An acid, p-toluenesulfonic acid, etc. can be mentioned. Among these, particularly preferred are alkyl aromatic sulfonic acids such as hexafluorophosphoric acid, triisopropylnaphthalenesulfonic acid and 2,5-dimethylbenzenesulfonic acid.

  Examples of the o-quinonediazide compound include compounds having various structures as long as they are compounds having one or more o-quinonediazide groups and increase alkali solubility by thermal decomposition. The o-quinonediazide has both the effect of losing the ability to suppress the dissolution of the binder by thermal decomposition and the effect of the o-quinonediazide itself changing to an alkali-soluble substance. Can act as an accelerator.

  The amount of additives other than the o-quinonediazide compound added to the upper or lower layer of the image recording layer is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, and particularly preferably 10 to 30% by mass. The additive and the binder are preferably contained in the same layer.

Further, for the purpose of further improving sensitivity, cyclic acid anhydrides, phenols, and organic acids can be added. Examples of the cyclic acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, succinic anhydride, pyromellitic anhydride, and the like.
Examples of the phenols include bisphenol A, p-ethoxyphenol, 2,4,4′-trihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 4-hydroxybenzophenone, 4,4 ′, 4 ″ -trihydroxy. Examples include triphenylmethane, 4,4 ′, 3 ″, 4 ″ -tetrahydroxy-3,5,3 ′, 5′-tetramethyltriphenylmethane.

Examples of the acids include sulfonic acids, sulfinic acids, alkylsulfuric acids, phosphonic acids, phosphate esters, and carboxylic acids. Specifically, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfinic acid , Ethyl sulfate, 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- Examples include cyclohexene-1,2-dicarboxylic acid, erucic acid, lauric acid, n-undecanoic acid, and ascorbic acid.
The proportion of the cyclic acid anhydride, phenol or organic acid in the upper layer or the lower layer of the image recording layer is preferably 0.05 to 20% by mass, more preferably 0.1 to 15% by mass, 10% by mass is particularly preferred.

  In order to improve the coating property, the image recording layer may contain a surfactant, for example, a fluorine-based surfactant described in JP-A No. 62-170950. The content of the surfactant is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass of the coating solution composition of the upper layer or lower layer of the image recording layer, or both layers. Further, in order to broaden the processing stability with respect to the developing conditions, nonionic surfactants such as those described in JP-A Nos. 62-251740 and 3-208514, JP-A No. 59-121044 are disclosed. , Amphoteric surfactants as described in JP-A-4-13149 can be contained.

Examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether and the like. Examples of the double-sided activator include alkyldi (aminoethyl) glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine and N-tetradecyl-N, N-betaine type. Is mentioned.
The content of the nonionic surfactant and amphoteric surfactant in the upper or lower layer of the image recording layer or the coating liquid composition of both layers is preferably 0.05 to 15% by mass, and 0.1 to 5% by mass. More preferred.

  The image recording layer can contain a printing-out agent for obtaining a visible image immediately after heating by exposure, or a dye or pigment as an image colorant. Typical examples of the printing-out agent include 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. Specifically, combinations of o-naphthoquinonediazide-4-sulfonic acid halides and salt-forming organic dyes described in JP-A-50-36209 and JP-A-53-8128, No. -36223, 54-74728, 60-3626, 61-143748, 61-151644 and 63-58440, and trihalomethyl compounds and salt-forming organic dyes Can be mentioned. Such trihalomethyl compounds include oxazole-based compounds and triazine-based compounds, both of which have excellent temporal stability and give clear printout images.

Various dyes can be used as the colorant used for improving the visibility of the image area. Suitable dyes include oil-soluble dyes and basic dyes. Specifically, brilliant green, oil green BG, oil blue BOS, oil blue # 603, oil black BY, oil black BS, oil black T-505 (manufactured by Orient Chemical Co., Ltd.), Victoria Pure Blue, Crystal Examples include violet (CI42555), methyl violet (CI42535), ethyl violet, rhodamine B (CI145170B), malachite green (CI42000), methylene blue (CI522015), and the like. The dyes described in JP-A-62-293247 are particularly preferred.
The content of these dyes is preferably 0.01 to 10% by mass and more preferably 0.1 to 3% by mass with respect to the upper or lower layer of the image recording layer or the total solid content of both layers.

  Furthermore, a plasticizer may be added to the upper layer or the lower layer of the image recording layer, or both layers, if necessary, in order to impart flexibility or the like of the image recording layer. Examples of the plasticizer include 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 oligomers and polymers are used.

[Formation of planographic printing plate precursor]
The positive type lithographic printing plate precursor used in the production method of the present invention comprises an upper layer and a lower layer image recording layer coating solution prepared by dissolving each component of the upper layer and the lower layer in a solvent. It is formed by applying in this order.

[Support]
As the support used for the lithographic printing plate precursor, a dimensionally stable plate-like material is preferable. For example, paper, paper laminated with plastic, metal plate (for example, aluminum, copper, etc.), plastic film (for example, Cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, polyethylene terephthalate, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic film on which a metal as described above is laminated or deposited.
Among them, an aluminum plate that has good dimensional stability and is relatively inexpensive is particularly preferable. Suitable aluminum plates are a pure aluminum plate and an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is at most 10% by mass. The thickness of the aluminum plate is preferably about 0.1 to 0.6 mm, more preferably 0.15 to 0.4 mm, and particularly preferably 0.2 to 0.3 mm.

The aluminum plate is subjected to various surface treatments such as roughening and anodizing treatment.
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 roughened aluminum plate is subjected to an alkali etching treatment and a neutralization treatment as necessary, and then anodized to enhance the water retention and wear resistance of the surface as desired. 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, or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte.

The conditions for the anodizing treatment vary depending on the electrolyte used, and thus cannot be specified in general. In general, however, the electrolyte concentration is 1 to 80% by mass solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 It is preferable that it is -60A / dm < ² >, a voltage is 1-100V, and electrolysis time is 10 second-5 minutes. The amount of the anodized film by the anodization is preferably 1.0 g / m ² or more. When the amount of the anodic oxide film is less than 1.0 g / m ² , the printing durability is insufficient, or when used as a lithographic printing plate, the non-image area may be easily damaged. As a result, a so-called “scratch stain” in which ink adheres to a scratched part during printing may be likely to occur.

  After the anodizing treatment, the aluminum surface is subjected to a hydrophilic treatment as necessary. The hydrophilization treatment method is disclosed in US Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and 3,902,734. The alkali metal silicate (for example, sodium silicate aqueous solution) method is mentioned. 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 And a method of treating with polyvinyl phosphonic acid as disclosed in the literature.

  The solvent is not particularly limited, and known solvents such as 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, dimethoxyethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene, etc. Is mentioned. These solvents may be used alone or in a combination of two or more.

The concentration of each component (total solid content including additives) of the upper and lower image recording layer coating solutions in the solvent is preferably 1 to 50% by mass in the lower image recording layer coating solution. The layer coating solution is preferably 1 to 50% by mass.
The image recording layer of the lithographic printing plate precursor according to the present invention has a coating amount after drying of the lower image recording layer provided on the side close to the support to ensure the printing durability and the remaining film during development. From the viewpoint of suppressing generation, it is preferably in the range of 0.5 to 1.5 g / m ² , more preferably in the range of 0.7 to 1.2 g / m ² .
The coating amount after drying of the upper image recording layer is preferably in the range of 0.05 to 1.0 g / ^{m 2,} more preferably in the range of 0.07~1.0g / ^{m 2.}
As the coating amount decreases, the apparent sensitivity increases, but the film characteristics of the image recording layer decrease.

  The method for coating the upper and lower image recording layers is not particularly limited, and known coating methods such as bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, Examples thereof include roll coating.

  In the lithographic printing plate precursor according to the invention, an undercoat layer can be provided as desired between the support and the lower layer of the image recording layer. As the component of the undercoat layer, various organic compounds are used. For example, phosphonic acids having an amino group such as carboxymethylcellulose, dextrin, gum arabic, 2-aminoethylphosphonic acid, and optionally substituted phenyl Organic phosphonic acids such as phosphonic acid, naphthylphosphonic acid, alkylphosphonic acid, glycerophosphonic acid, methylenediphosphonic acid and ethylenediphosphonic acid, optionally substituted phenylphosphoric acid, naphthylphosphoric acid, alkylphosphoric acid and glyceroline Organic phosphoric acid such as acid, optionally substituted phenylphosphinic acid, naphthylphosphinic acid, organic phosphinic acid such as alkylphosphinic acid and glycerophosphinic acid, amino acids such as glycine and β-alanine, and triethanolamine Hydride such as hydrochloride Hydrochloride salts of amines having a carboxy group. These may be used individually by 1 type and may use 2 or more types together.

  The undercoat layer can be provided by the following method. That is, a method in which 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 to provide a solution, or water, methanol, ethanol, methyl ethyl ketone, or the like. For example, an aluminum plate is immersed in a solution in which the organic compound is dissolved in an organic solvent or a mixed solvent thereof to adsorb the compound, and then washed and dried with water or the like.

  In the former method, the concentration of the organic compound in the solution in which the organic compound is dissolved is preferably 0.005 to 10% by mass. In the latter method, the concentration of the organic compound in the solution in which the organic compound is dissolved is preferably 0.01 to 20% by mass, more preferably 0.05 to 5% by mass, The temperature is preferably 20 to 90 ° C, more preferably 25 to 50 ° C, and the immersion time is preferably 0.1 second to 20 minutes, and more preferably 2 seconds to 1 minute.

The solution in which the organic compound is dissolved may contain a basic substance such as ammonia, triethylamine or potassium hydroxide, or an acidic substance such as hydrochloric acid or phosphoric acid to adjust the pH to 1 to 12. A yellow dye can also be added to improve the tone reproducibility of the image forming material.
The coating amount of the organic undercoat layer is preferably ² to 200 mg / m ^{2 and} more preferably 5 to 100 mg / m ² . If the coating amount is out of the numerical range, sufficient printing durability may not be obtained.

In the lithographic printing plate precursor according to the invention, an overcoat can be provided on the upper layer of the image recording layer as desired. The overcoat component is preferably an alkali-soluble polyurethane resin. Among them, a polyurethane resin having a carboxyl group in the polymer main chain, which is a reaction product of an isocyanate compound and a diol compound having a carboxyl group, can be mentioned. The isocyanate for producing the polyurethane resin is preferably an aromatic diisocyanate such as tolylene diisocyanate, and the diol is preferably 3,5-dihydroxybenzoic acid or 2,2-bis (hydroxymethyl) propionic acid. .
In this way, a lithographic printing plate precursor used in the lithographic printing plate preparation method of the present invention is obtained.

<Preparation method of lithographic printing plate>
The lithographic printing plate precursor obtained as described above is usually subjected to image exposure and development treatment to produce a lithographic printing plate. That is, in a negative lithographic printing plate precursor exposed to a desired image quality, the solubility of the exposed area in an alkaline developer is improved, and it is removed by development to form a non-image area. The recording layer becomes the image portion of the lithographic printing plate.
[Exposure process]
Examples of the active light source used for exposure include a mercury lamp, a metal halide lamp, a xenon lamp, a chemical lamp, and a carbon arc lamp. Examples of radiation include electron beams, X-rays, ion beams, and far infrared rays. Also, g-line, i-line, deep-UV light, and high-density energy beam (laser beam) are used. Examples of the laser beam include a helium / neon laser, an argon laser, a krypton laser, a helium / cadmium laser, and a KrF excimer laser.
The image-like exposure may be performed by exposure through a mask such as a lith film, or may be performed by scanning exposure.
In the present invention, a light source having a light emission wavelength from the near infrared region to the infrared region is preferable, and a solid laser or a semiconductor laser is particularly preferable.

[Development process]
Next, the development process will be described in detail.
(Specific developer)
A processing solution (hereinafter also referred to as a specific developing solution) used in the developing step is an alkaline aqueous solution having a pH of 8.5 to 10.8 containing an anionic surfactant. An anionic surfactant contributes to the improvement of processability.

The anionic surfactant used in the specific developer in the present invention contributes to the improvement of the processability.
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, N-alkyl sulfosuccinic acid monoamide disodium salts, petroleum sulfonates, sulfated castor oil , Sulfated beef tallow oil, fatty acid alkyl ester sulfates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fatty acid monoglyceride sulfates Tell salt, polyoxyethylene alkylphenyl ether sulfate ester salt, polyoxyethylene styryl phenyl ether sulfate ester salt, alkyl phosphate ester salt, polyoxyethylene alkyl ether phosphate ester salt, polyoxyethylene alkylphenyl ether phosphate ester salt, styrene-anhydrous Partially saponified products of maleic acid copolymer, partially saponified products of olefin-maleic anhydride copolymer, naphthalene sulfonate formalin condensates, aromatic sulfonates, aromatic substituted polyoxyethylene sulfonates, etc. Is mentioned.
Among these, dialkyl sulfosuccinates, alkyl sulfate esters and alkyl naphthalene sulfonates are particularly preferably used.

As the anionic surfactant used in the treatment liquid of the present invention, an anionic surfactant containing a sulfonic acid or a sulfonate is particularly preferable.
Anionic surfactants can be used alone or in combination.
The content of the anionic surfactant in the developer is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and most preferably 2 to 10% by mass.

The specific developer according to the present invention needs to have a pH of 8.5 to 10.8. In order to keep the pH of the developer in the above range, it is preferable that carbonate ions and hydrogen carbonate ions exist as buffering agents. Due to the functions of carbonate ions and hydrogen carbonate ions, it is considered that the change in pH can be suppressed even when the developer is used for a long period of time, and the development loss due to the change in pH, the development of development residue, etc. 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 hydrogen carbonate that can be used for adjusting the pH 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 pH of the developer may be any pH that causes a buffering action, and specifically needs to be in the range of pH 8.5 to 10.8. When the pH is lower than 8.5, the developability of the non-image area is lowered, and when the pH is higher than 10.8, the processing ability is lowered due to the influence of carbon dioxide in the air.

  0.3-20 mass% is preferable with respect to the mass of alkaline aqueous solution, and, as for the total amount of carbonate and hydrogencarbonate, 0.5-10 mass% is more preferable, and 1-5 mass% is especially preferable. When the total amount is 0.3% by mass or more, developability and processing capacity do not decrease, and when it is 20% by mass or less, it becomes difficult to form precipitates and crystals. 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. Examples of inorganic salts include primary sodium phosphate, secondary sodium phosphate, primary potassium phosphate, secondary potassium phosphate, sodium tripolyphosphate, potassium pyrophosphate, sodium hexametaphosphate, and the like.
These other alkaline agents are used alone or in combination of two or more. In addition to the above, the treatment liquid of the present invention may contain a wetting agent, preservative, chelate compound, antifoaming agent, organic acid, organic solvent, inorganic acid, inorganic salt, and the like.

  However, if the specific developer contains a water-soluble polymer compound, there is a concern that the plate surface is likely to be sticky especially when the processing solution is fatigued, so the content of the water-soluble polymer compound in the specific developer according to the present invention is It is preferably 10 ppm or less, more preferably 5 ppm or less, and most preferably not contained. As used herein, the “water-soluble polymer compound” includes, for example, a hydroxyl group, a carboxyl group, a carboxylate group, a hydroxyethyl group, a polyoxyethyl group, a hydroxypropyl group, a polyoxypropyl group, an amino group, an aminoethyl group, Examples thereof include those having hydrophilic groups such as aminopropyl group, ammonium group, amide group, carboxymethyl group, sulfo group, and phosphate group.

  Specific examples include gum arabic, casein, gelatin, starch derivatives, carboxymethylcellulose and its sodium salt, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymers, styrene-maleic acid copolymers, polyacrylic acids and their salts, Polymethacrylic acids and their salts, hydroxyethyl methacrylate homopolymers and copolymers, hydroxyethyl acrylate homopolymers and copolymers, hydroxypropyl methacrylate homopolymers and copolymers, hydroxypropyl acrylate homopolymers and copolymers, hydroxybutyl methacrylate homopolymers Polymers and copolymers, homopolymers and copolymers of hydroxybutyl acrylate, polyethylene glycol Alcohols, hydroxypropylene polymers, polyvinyl alcohols, hydrolyzed polyvinyl acetate, polyvinyl formal, polyvinyl butyral, polyvinyl pyrrolidone, acrylamide homopolymers and copolymers having a hydrolysis degree of 60 mol% or more, preferably 80 mol% or more, methacryl Homopolymers and polymers of amides, homopolymers and copolymers of N-methylolacrylamide, polyvinylpyrrolidone, alcohol-soluble nylon, polyethers of 2,2-bis- (4-hydroxyphenyl) -propane and epichlorohydrin, etc. It is done.

  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. Generally, the wetting agent is used in an amount of 0.1 to 5% by weight based on the total weight of the treatment liquid.

  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, derivatives such as pyridine, quinoline, guanidine, diazine, triazole derivatives, oxazole, oxazine derivatives, nitrobromoalcohol-based 2-bromo-2-nitropropane-1,3diol, 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 stably exerts an effect on bacteria, mold, yeast, etc., and varies depending on the type of bacteria, mold, yeast, but 0.01 to 4 relative to the treatment liquid. A range of mass% is preferred.

  Examples of the chelate compound include 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 Nitrilotriacetic acid, sodium salt; 1-hydroxyethane-1,1-diphosphonic acid, potassium salt, sodium salt; aminotri (methylenephosphonic acid), potassium salt, sodium salt And organic phosphonic acids and phosphonoalkanetricarboxylic acids. Organic amine salts are also effective in place of the sodium and potassium salts of the chelating agents. A chelating agent is selected that is stably present in the treatment liquid composition and does not impair the printability. The addition amount is preferably 0.001 to 1.0% by mass with respect to the treatment liquid.

  As the antifoaming agent, a general silicon-based self-emulsifying type, emulsifying type, nonionic HLB 5 or less compound can be used. Silicon antifoaming agents 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 mass% with respect to the treatment liquid.

  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 mass with respect to the treatment liquid.

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

Polar solvents include alcohols (methanol, ethanol, isopropanol, benzyl alcohol, 2-ethoxyethanol, diethylene glycol monoethyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monobenzyl ether, ethylene Glycol monophenyl ether, methylphenyl carbinol, n-amyl alcohol, methyl amyl alcohol, etc.), ketones (acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (ethyl acetate, propyl acetate, butyl acetate, benzyl acetate, methyl lactate, Propylene glycol monomethyl ether acetate, diethyl phthalate, butyl levulinate, etc. Other (triethyl phosphate, tricresyl phosphate, N- phenylethanolamine, N- phenyldiethanolamine, etc.) and the like.
Examples of inorganic acids and inorganic salts include phosphoric acid, metaphosphoric acid, primary ammonium phosphate, secondary ammonium phosphate, magnesium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate, sodium sulfate, potassium sulfate, ammonium sulfate, sodium sulfite, ammonium sulfite, Examples thereof include sodium hydrogen sulfate and nickel sulfate. The content of the inorganic salt is preferably 0.01 to 0.5% by mass based on the total mass of the treatment liquid.

  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 mass from the viewpoint of safety and flammability.

(Development conditions)
The development temperature is usually 60 ° C. or lower, preferably about 15 to 40 ° C. In the developing process using an automatic developing machine, the developing solution may be fatigued depending on the amount of processing, and thus the processing capability may be restored by using a replenishing solution or a fresh developing solution.
In the normal development processing step, alkali development is performed, alkali is removed in the post-water washing step, gum processing is performed in the gumming step, and drying is performed in the drying step. By using an aqueous solution containing hydrogen ions and an anionic surfactant, pre-water washing, development and gumming are performed simultaneously. Therefore, the pre-water washing step is not particularly required, and the drying step can be performed only by using one liquid, and further after performing pre-water washing, development and gumming in one bath. After development, it is preferable to dry after removing excess processing liquid 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 stiffness of the support 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, as described in Japanese Patent Application Laid-Open Nos. 58-159533 and 3-100554, or as disclosed in Japanese Utility Model Publication No. 62-167253, metal or plastic in which brush materials are implanted in rows A brush roll can be used in which the groove mold material is radially wound around a plastic or metal roll as a core without a gap.
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 is developed and gummed in the developing tank 20 and dried in the drying unit 10.

The lithographic printing plate obtained as described above can be subjected to a printing process. However, when it is desired to obtain a lithographic printing plate having a higher printing durability, a burning process is performed. In the case of burning a lithographic printing plate, the preparation as described in JP-B-61-2518, JP-A-55-28062, JP-A-62-31859, JP-A-61-159655 is performed before the burning. It is preferable to treat with a surface liquid. The lithographic printing plate coated with the surface-adjusting liquid is dried if necessary and then heated to a high temperature with a burning processor (for example, a burning processor sold by FUJIFILM Corporation: “BP-1300”). The The heating temperature and time in this case are preferably about 1 to 20 minutes at a temperature of 180 to 300 ° C., although it depends on the type of components forming the image.
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 thus obtained is loaded on an offset printing machine and used for printing a large number of sheets.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

[Synthesis of polyurethane resin]
<Synthesis Example 1>
In a 500 ml three-necked flask, 125 g of 4,4′-diphenylmethane diisocyanate and 67 g of 2,2-bis (hydroxymethyl) propionic acid were dissolved in 290 ml of dioxane. After adding 1 g of N, N-diethylaniline, the mixture was stirred for 6 hours under reflux of dioxane. After the reaction, the polymer was precipitated little by little into a solution of 4 L of water and 40 ml of acetic acid. This solid was vacuum-dried to obtain 185 g of polyurethane resin (1). The acid content was 2.47 meq / g. When the molecular weight was measured by GPC, the weight average molecular weight (polystyrene standard) was 28,000.

<Synthesis Examples 2-7>
Polyurethane resins (2) to (7) were synthesized in the same manner as in Synthesis Example 1 except that the starting materials in Synthesis Example 1 were changed to the diisocyanate compounds and diol compounds described below.

[Lithographic printing plate precursor 1]
[Production of support]
0.24 mm thick aluminum plate (Si: 0.06 mass%, Fe: 0.30 mass%, Cu: 0.014 mass%, Mn: 0.001 mass%, Mg: 0.001 mass%, Zn : 0.001% by mass, Ti: 0.03% by mass, with the balance being aluminum and an inevitable impurity aluminum alloy), the following surface treatment was continuously performed.

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 mass% of ammonium ions) at a temperature of 80 ° C. After washing with water, the aluminum plate was etched by spraying at 32 ° C. with a caustic soda concentration of 26 mass% and an aluminum ion concentration of 6.5 mass%, the aluminum plate was dissolved at 0.20 g / m ² , and washed with water. Thereafter, a desmut treatment by spraying was performed with a 25% by weight aqueous solution of sulfuric acid having a temperature of 60 ° C. (containing 0.5% by weight of aluminum ions), and washing with water by spraying 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 anodizing treatment is immersed in a treatment tank of 1 mass% aqueous solution of sodium silicate No. 3 at a temperature of 30 ° C. for 10 seconds for alkali metal silicate treatment (silicate treatment). It was. 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 0.5g
・ Methanol 95g
・ Water 5g

[Formation of recording layer]
After applying the lower layer coating solution 1 having the following composition to the support obtained as described above with a bar coater so that the coating amount becomes 1.5 g / m ² , it is dried at 160 ° C. for 44 seconds and immediately 17 to 20 ° C. The support was cooled to 35 ° C. with cold air.
-Lower layer coating solution 1-
N-phenylmaleimide / methacrylic acid / methacrylamide copolymer 1.0 g
(Molar ratio: 45/20/35, Mw: 50000)
-Cyanine dye A 0.017 g represented by the following structural formula
・ Crystal Violet (Hodogaya Chemical Co., Ltd.) 0.015g
・ Megafac F-177 (manufactured by DIC Corporation, fluorosurfactant) 0.05 g
・ Γ-Butyllactone 10g
・ Methyl ethyl ketone 10g
・ 8g of 1-methoxy-2-propanol

Thereafter, a coating solution 1 for the upper layer having the composition shown below was applied by a bar coater so that the coating amount was 0.5 g / m ² , dried at 130 ° C. for 40 seconds, and further slowly cooled by wind at 20 to 26 ° C. A printing plate precursor 1 was prepared.
-Coating liquid for upper layer 1-
-Polyurethane resin (1) of Synthesis Example 1 30.0 g
BYK-333 (polyether-modified polydimethylsiloxane manufactured by BYK Chemie)
0.3g
・ Ethyl violet 0.03g
・ Megafac F-177 (Fluorosurfactant) 0.05g
・ 3-Pentanone 60g
・ Propylene glycol monomethyl ether acetate 8g

[Lithographic printing plate precursors 2-7]
Except that the polyurethane resin (1) used in the upper layer coating liquid 1 in the lithographic printing plate precursor 1 was changed to the polyurethane resins (2) to (7) obtained in the above synthesis example, the same as in the lithographic printing plate precursor 1 Thus, lithographic printing plate precursors 2 to 7 were prepared.

[Lithographic printing plate precursor 8]
The same as lithographic printing plate precursor 1, except that the polyorganosiloxane used in coating solution 1 for the upper layer in lithographic printing plate precursor 1 was changed to TEGO Glide 410 (polysiloxane polyether copolymer available from TegoChemie Service GmbH). A lithographic printing plate precursor 8 was prepared.
[Lithographic printing plate precursor 9]
A lithographic printing plate precursor 9 was prepared in the same manner as the lithographic printing plate precursor 1, except that the upper layer coating solution in the lithographic printing plate precursor 1 was changed to the following upper layer coating solution 2.
-Upper layer coating solution 2-
・ Polyurethane (1) of Synthesis Example 1 30.0 g
BYK-333 (polyether-modified polydimethylsiloxane manufactured by BYK Chemie)
0.3g
・ 1.5 g of cyanine dye A used in lower layer coating solution 1
・ Ethyl violet 0.03g
・ Megafac F-177 (Fluorosurfactant) 0.05g
・ 3-Pentanone 60g
・ Propylene glycol monomethyl ether acetate 8g

[Lithographic printing plate precursor 10]
In the preparation of the upper layer coating liquid 1 in the lithographic printing plate precursor 1, an upper layer coating liquid was prepared without adding polyorganosiloxane, and the rest was the same as the lithographic printing plate precursor 1 to produce a lithographic printing plate precursor 10. .

[Lithographic printing plate precursor 11]
In the preparation of the upper layer coating liquid 1 in the lithographic printing plate precursor 1, the polyurethane resin was changed to the comparative resin (1) (weight average molecular weight: 50000) which is an alkali-soluble polymer having the following structure to prepare an upper layer coating liquid. Otherwise, the lithographic printing plate precursor 11 was produced in the same manner as the lithographic printing plate precursor 1.

Comparative resin (1)

[Lithographic printing plate precursor 12]
In the preparation of the lower layer coating solution 1 in the lithographic printing plate precursor 9, a lower layer coating solution was prepared without adding the cyanine dye A, and the lithographic printing plate precursor 12 was prepared in the same manner as in the lithographic printing plate precursor 9. .

-Evaluation-
(Exposure process)
The obtained lithographic printing plate precursors 1 to 12 were exposed (laser power: 8.5 W, rotation speed: 185 rpm) using an exposure device (Trendsetter F, manufactured by Kodak).
For evaluation of development residue, the entire surface was exposed to produce a clear image.
(Development process)
The exposed lithographic printing plate precursor is an automatic development processor shown in FIG. 1 [developing tank 25L, plate conveyance speed 100 cm / min, brush having an outer diameter of 50 mm in which polybutylene terephthalate fibers (hair diameter 200 μm, hair length 17 mm) are implanted. One roll is 200 revolutions per minute in the same direction as the conveying direction (peripheral speed of brush tip 0.52 m / sec), drying temperature 80 ° C.], and the developer combinations shown in Table 1 at a temperature of 30 ° C. The development processing was performed until the processing amount reached 20 m ² / L.

(Specific developer 1)
・ Water 8963.8g
・ 200g sodium carbonate
・ Sodium bicarbonate 100g
・ New call B4SN (61% aqueous solution) 656g
(Polyoxyethylene naphthyl ether sulfate, anionic surfactant manufactured by Nippon Emulsifier Co., Ltd.)
・ EDTA 4Na 80g
・ 2-Bromo-2-nitropropane-1,3diol 0.1g
・ 0.1g of 2-methyl-4-isothiazolin-3-one
(PH: 9.7)

(Specific developer 2)
・ Water 8665g
・ 150g sodium carbonate
・ Sodium carbonate 80g
-745 g of Eleminol MON (47% aqueous solution)
(Sodium dodecyl diphenyl ether disulfonate, anionic surfactant manufactured by Sanyo Chemical Co., Ltd.)
・ 180g of primary ammonium phosphate
・ Sodium hexametaphosphate 180g
(PH: 9.3)

(Specific developer 3)
・ Water 8150.8g
・ 200g sodium carbonate
・ Sodium bicarbonate 80g
・ Perex NBL (35% aqueous solution) 1429g
(Sodium alkylnaphthalene sulfonate, anionic surfactant manufactured by Kao Corporation)
・ Citric acid 40g
・ Primary ammonium phosphate 20g
・ Propylene glycol 80g
・ 2-bromo-2-nitropropane-1,3-diol 0.1 g
・ 0.1g of 2-methyl-4-isothiazolin-3-one
(PH: 9.8)

(Specific developer 4)
・ Water 8665g
・ Sodium carbonate 242g
・ Sodium bicarbonate 12g
-745 g of Eleminol MON (47% aqueous solution)
(Sodium dodecyl diphenyl ether disulfonate, anionic surfactant manufactured by Sanyo Chemical Co., Ltd.)
・ 180g of primary ammonium phosphate
・ Sodium hexametaphosphate 180g
(PH: 8.8)

(Specific developer 5)
・ Water 8665g
・ Sodium carbonate 12g
・ Sodium bicarbonate 242g
-745 g of Eleminol MON (47% aqueous solution)
(Sodium dodecyl diphenyl ether disulfonate, anionic surfactant manufactured by Sanyo Chemical Co., Ltd.)
・ 180g of primary ammonium phosphate
・ Sodium hexametaphosphate 180g
(PH: 10.3)

(Comparative developer 1)
・ 9779.8g of water
・ Sodium carbonate 130g
・ Sodium bicarbonate 70g
・ Primary ammonium phosphate 20g
・ 2-bromo-2-nitropropane-1,3-diol 0.1 g
・ 0.1g of 2-methyl-4-isothiazolin-3-one
(PH: 9.7)

(Comparative developer 2)
・ Water 8665g
・ Boric acid 74g
・ Sodium hydroxide 126g
-745 g of Eleminol MON (47% aqueous solution)
(Sodium dodecyl diphenyl ether disulfonate, anionic surfactant manufactured by Sanyo Chemical Co., Ltd.)
・ 180g of primary ammonium phosphate
・ Sodium hexametaphosphate 180g
(PH: 8.4)

[Evaluation]
Each lithographic printing plate precursor and each developer were used as shown in Table 1 below, evaluated as follows, and the results are summarized in Table 1.
[Evaluation of development residue]
The entire exposed lithographic printing plate precursor for developing debris evaluation was developed by an automatic developing machine, and the number of debris adhering to the lithographic printing plate precursor was visually measured after the developing treatment. The unit is pieces / m ² .

[Evaluation of developability]
The lithographic printing plate obtained by imagewise exposure and then development is attached to a printing machine SOR-M manufactured by Heidelberg, and dampening solution (EU-3 (Etchi solution manufactured by FUJIFILM Corporation) / water / Using isopropyl alcohol = 1/89/10 (volume ratio)) and Fusion G (N) black ink (manufactured by DIC Corporation), printing was performed at a printing speed of 6000 sheets per hour. At this time, it was visually confirmed whether or not scumming occurred in the non-image area of the printed matter obtained.

  From the results of Table 1, according to the lithographic printing plate preparation method of the present invention, despite the one-bath treatment with a weak alkaline developer, the generation of debris in the developing tank is suppressed, and the development processability is excellent. According to the planographic printing plate obtained by this production method, a high quality printed matter was obtained. On the other hand, Comparative Example 1 containing no polyorganosiloxane, Comparative Example 2 containing no polyurethane, Comparative Example 3 containing no infrared absorber in the lower layer, and Comparative Examples 4 and 5 using a developer outside the scope of the present invention In addition, development debris and scumming were observed.

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 (8)

On the support, (A) a water-insoluble and alkali-soluble resin, and (B) a lower layer containing an infrared absorber, (C) a water-insoluble and alkali-soluble polyurethane resin, and (D) an upper layer containing a polyorganosiloxane. An exposure process for image exposure of a positive planographic printing plate precursor comprising an image recording layer having
A method for preparing a lithographic printing plate comprising a development step of developing an image-exposed positive lithographic printing plate precursor using an alkaline aqueous solution containing an anionic surfactant having a pH of 8.5 to 10.8 in this order.   The (A) water-insoluble and alkali-soluble resin is a resin containing one or more selected from the group consisting of phenolic hydroxyl groups, carboxy groups, sulfonic acid groups, phosphoric acid groups, sulfonamide groups, and active imide groups. The method for producing a lithographic printing plate according to claim 1.   The method for preparing a lithographic printing plate according to claim 1, wherein the (B) infrared absorber is a cyanine dye. The (C) water-insoluble and alkali-soluble polyurethane resin is a polyurethane resin having a carboxy group bonded to the polymer main chain through a single bond or a divalent linking group . 2. A method for producing a lithographic printing plate as described in item 1. The (C) water-insoluble and alkali-soluble polyurethane resin is a diol having a diisocyanate compound represented by the following general formula (I) and a carboxy group represented by the following general formula (II) or general formula (III) The method for preparing a lithographic printing plate according to any one of claims 1 to 4, which is a polyurethane resin having a basic skeleton as a reaction product of at least one compound.

[In general formula (I), R ¹ Represents a divalent linking group. In general formula (II), R ² Represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, an alkoxy group, or an aryloxy group. In the general formula (II) or (III), R ³ , R ⁴ And R ⁵ May be the same or different and each represents a single bond or a divalent linking group. In general formula (III), Ar represents a trivalent aromatic hydrocarbon which may have a substituent. ] The method for producing a lithographic printing plate according to any one of claims 1 to 5 , wherein the upper layer further contains (B) an infrared absorber. The method for preparing a lithographic printing plate according to any one of claims 1 to 6 , wherein a content of the water-soluble polymer compound in the alkaline aqueous solution is 10 ppm or less. The developing step is not required for the water washing step and gumming step as a separate process, any one of claims 1 to 7 pre-water washing, a step of performing development and gumming in one bath using the alkaline aqueous solution 2. A method for producing a lithographic printing plate as described in item 1.