JPS62284792A - Base for planographic plate and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide excellent printing properties and stability, by providing a water-retaining layer comprising a specified non-crosslinkable water-soluble acrylic acid polymer on a hydrophilic layer comprising a specified resin component while providing a crosslinked layer therebetween. CONSTITUTION:A hydrophilic layer 2 comprising a mixture of a resin component, which comprises 5-40pts.wt. of a urea resin and 60-95pts.wt. of a polyamide resin, with a pigment component is provided on a base layer 1. A water- retaining layer 3 comprising at least one non-crosslinkable water-soluble acrylic acid polymer containing at least one member selected from acrylic acid and alpha- and beta-substd. products thereof as a polymeric component is provided on the hydrophilic layer 2. At the interface of the hydrophilic layer 2 and the water-retaining layer 3, part of the constituents of the layer 2 and part of the constituents of the layer 3 coexist, and an interfacial cross-linked layer 5 is formed between the layers 2, 3. Thus, the hydrophilic layer and the water- retaining layer are firmly bonded to each other through the cross-linked layer, and the water-retaining layer and an image layer as provided thereon are firmly adhered to each other, so that a printing plate thus obtained has excellent plate wear property and stability.

Description

[Detailed description of the invention]

3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a lithographic printing plate support and a method for producing the same. The present invention relates to a lithographic printing plate support that has excellent adhesion to the image layer formed by the lithographic printing plate, and a method for producing the same. Gold plates such as metal plates, plastic films, paper, etc. are known.They differ in printing durability, difficulty in developing, quality of printed images, ease of staining during printing, and printing layers. Issues such as adhesive strength between and support layer,
Alternatively, an appropriate support has been selected depending on the purpose of printing in terms of plate cost, ease of handling, etc. Recently, with the development of automatic plate making and automatic printing methods, the popularity of simple lithographic printing plates has rapidly increased. . For these light printing applications, paper-based lithographic printing plates have come to be widely used because they are inexpensive, easy to cut and punch, and easy to handle. However, when a paper-based material is used as a lithographic printing plate, unlike a metal plate or plastic film, paper easily absorbs water, and as a result, the plate may expand or contract during printing, or the surface may be uneven. Unevenness occurs, or
It has disadvantages such as insufficient water resistance and printing durability, but it has adequate water retention fc to be used as a lithographic printing plate, and stains caused by printing ink may occur. Therefore, in order to use paper as a support for a lithographic printing plate, it is necessary to perform water resistance treatment. For example, processed paper is known, which is impregnated with a thick resin, coated, or laminated with an olefin resin such as polyethylene. A suitable printing plate has not yet been obtained.0 In order to solve the above problems,
Publication No. 202 and its improvement method as JP-A-55-404
No. 06 proposes photosensitive lithographic printing plates, that is, in these printing plates, a support and a photosensitive N7! I
(Image, 1) A hydrophilic layer is formed between the resin components, and the hydrophilic layer consists of a urea resin with a weight of 5 to 40 gB and a polyamide resin with a weight of 60 to 95 gB. This hydrophilic layer is characterized by being formed from a mixture containing a pigment component and a pigment component.Such a hydrophilic layer considerably improves the printing durability and printability of the resulting photosensitive lithographic printing plate. However, there is a desire for further improvement in basic properties such as printing durability, background smudge prevention, image quality, and development stability.
First, the hydrophilicity of the hydrophilic layer is not sufficient, and it is easy to cause scumming.
In addition, if the degree of heat curing of the hydrophilic layer is lowered to increase hydrophilicity,
In order to solve the above-mentioned problems, there was a drawback that developability and printing durability were deteriorated.
In Japanese Patent No. 14794, it was proposed to further provide a water-retaining layer on the above-mentioned hydrophilic layer.The water-retaining layer contains acrylic acid or its α- or β-substituted product as a polymerization component on the hydrophilic layer. Apply a mixture of water-soluble acrylic acid polymer and crosslinking agent. Obtained by infiltration and then heating crosslinking.1. It is something that However, in the lithographic printing plate support having the water-retaining layer described above, when a photosensitive layer, especially a negative photosensitive layer, is provided on the water-retaining layer, the adhesion and contact stability between the photosensitive layer and the water-retaining layer are insufficient. [Problems to be solved by the invention] The present invention solves the above-mentioned problems in conventional lithographic printing plate supports. This is an attempt to address the following points, namely, the lack of contact stability between the support and the photosensitive layer (image film), and the lack of printing durability of the resulting printing plate. tth means for doing so, 2 and its effects] The lithographic printing support according to the present invention is formed on at least one surface of the supporting layer and the support gpr-, and at least a portion of 5 to 40 fl. one kind of urea-based fat and 60 to 95 parts by weight of at least 1v
a hydrophilic layer consisting of a mixture containing a four-finger component consisting of a polyamide-based fat of M and one pigment component, and a hydrophilic layer formed on the hydrophilic layer and containing acrylic acid and its a water-retaining layer comprising at least one non-crosslinked water-soluble acrylic acid polymer containing at least nine members selected from substituents as a polymerization component, and at the interface between the hydrophilic layer and the water-retaining layer, A portion of the acrylic acid polymer and a portion of the urea resin. The method of the present invention for producing the lithographic printing plate support includes: , 5 to 40 parts by weight of at least one urea resin on at least one side of the support layer, and 60 to 951iLi
At least 1 part? A hydrophilic layer consisting of a mixture containing a base portion made of polyamide resin and a pigment fraction is formed, and a mixture of acrylic acid and its α- and β-substituted products is formed on the hydrophilic layer. at least one selected
A coating layer of a coating solution containing at least one water-soluble acrylic acid polymer contained as a synthetic component is formed, and the resulting laminate is heat-treated to a temperature of 120 to 200°C, thereby coating the coating solution. The layer solidifies to form a water retention layer and before

[At the interface between the hydrophilic layer and the water-retaining layer, a portion of the acrylic acid polymer, a portion of the urea-based μS resin, and a portion of the polyamide resin are intermingled with each other, and This feature is characterized in that *a, M conjunction is formed between them. In the present invention, the surface distribution of the water-retaining layer is made of a water-soluble acrylic acid polymer and is not three-dimensionally crosslinked. Therefore, when a photosensitive layer, especially a photosensitive resin layer, is formed on a water-retaining layer, the water-retaining layer is easily swollen or dissolved by the 6 medium in the photosensitive oil-containing coating solution, and the photosensitive l! ! What are the lubricant-containing coating liquid layer and water-retaining layer? At the interface, the photosensitive t# (a stone in which part of the fat and part of the acrylic acid polymer crystallize together. Therefore, when the solvent evaporates from these two layers and both layers solidify, the photosensitive layer and water retention Furthermore, in the invention, the hydrophilic layer and the water-retaining layer include a portion of the acrylic acid polymer, a portion of the urea resin, and
In the lithographic printing plate of the present invention, the hydrophilic layer and the water-retaining layer can be bonded very firmly together, with a part of the polyamide resin mixed therein and cross-linked bonds formed between them. The printing plate produced from the support may exhibit extremely high printing durability and stability. is support layer 1
A hydrophilic rft2 is provided on the upper surface, a water retaining layer 3 is formed on the hydrophilic wi2, and a backing layer 4 for imparting water resistance is provided on the lower surface of the support layer 1.
! An interfacial cross-linked layer 5 is formed at the interface between the support layer 1 and the water-retaining layer 3. In the planographic plate shown in FIG. A hydrophilic layer 2 and a water retaining layer 3 are provided on the upper surface, a backing layer 4 is formed on the lower surface of the support layer 1, and an interfacial crosslinked layer 5 is formed at the interface between the hydrophilic layer 2 and the water retaining layer 3. . The support layer of the photosensitive lithographic printing plate support of the present invention is as follows. Generally aluminum plate, zinc plate, copper plate, iron plate, resin plate,
It can be formed using plastic film, paper, or a composite of two or more of these, especially in the case of paper paste, water-resistant paper coated with sphere resin, polyethylene laminated paper, various plastic film laminated papers, aluminum, etc. Foil laminated paper, synthetic paper, etc. can be suitably used. In the present invention, a hydrophilic layer is provided on the support layer to form a highly adhesive surface of the support. This hydrophilic layer contains 5 to 40 parts by weight of urea resin and 60 to 40 parts by weight of urea resin.
A resin component consisting of 95 parts by weight of a polyamide resin;
If the amount of the four fingers from the mixture containing the pigment and the pigment fraction exceeds 95 double residues, the adhesion between the image formed from the photosensitive layer and the hydrophilic layer will be poor, and the printing plate obtained will have poor printing durability. Also, if the amount of the urea resin is greater than 40 parts by weight, and therefore the amount of the polyamide resin is less than 60 parts by weight, the developability will decrease and the printing durability of the resulting printing plate will be poor. This results in disadvantages such as the tendency for background stains to occur. Urea resin is unmodified urea-formaldehyde resin,
A cation-modified urea-formaldehyde resin that has been F-functionalized with one or more polyfunctional basic compounds having a plurality of basic groups in an amount of 5 to 20% based on the weight of urea, and one type of resin that is 5 to 15% based on the total amount of urea. At least one selected from the group consisting of nonionic modified urea-formaldehyde resins modified with the above polyol compounds, and anionic modified urea-formaldehyde resins modified with 5 to 15 acidic sulfites based on the weight of urea. Preferably, the polyfunctional basic compound may be selected from, for example, dimethylaminoethanol, jetanolamine, oxazolidine, polyphenylbiguanide, tetraethylenepentamine, and guanylurea. For example, ethylene glycol,
The polyamide resin selected from glycerin and useful in the present invention includes a polyamide such as nylon 6, nylon/66, and nylon 610, and at least one of the polyamides and formaldehyde, or formaldehyde and alcohol. Modified polyamide resin modified with a modifier consisting of at least one of the polyamides described above was modified with a modifier consisting of an epoxy compound. It is preferably selected from the group consisting of epoxy-modified polyamide prongs, and modified polyamide prongs such as polyamine-epichlorohydrin-modified polyamide prongs obtained by modifying at least one of the polyamides with a modifier consisting of epichlorohydrin and a polyamine compound. In each of the above-mentioned polyamide resins, 2 to 30 hydrogen atoms of the amide group are converted to fgf by the modifier residue.
The pigment fraction to be mixed with the resin component to form the hydrophilic layer of the lithographic printing plate support of the present invention, which is preferably 1%, is, for example, titanium dioxide, zinc oxide, acid clay, or , clay, etc. can be selected arbitrarily. In general, the pigment component is effective for improving the hydrophilicity and coating properties of the resin component, and is preferably used in an amount of (J, 5 to 2.5 times the weight of the four-fingered component, and from ] to 1.
．． It is more preferable to use 5 times the amount.0 The above-mentioned Ill fat fraction and pigment components are mixed with a suitable solvent 1, if necessary, such as water, methanol, cellosolve, dimethylformamide, methyl ethyl ketone, acetone,
By mixing with xylene, ethyl acetate, or a mixture of 2 fg or more of the above-mentioned compounds, and applying the resulting coating liquid to the support layer, a hydrophilic layer is formed. To the resin component as described above, supplements such as polyvinyl alcohol, various modified polyhinyl alcohols, casein, acrylic acid amide-acrylic acid ester copolymer, modified polyacrylic acid, etc. in an amount of 1 J, OL or more are added. Resins may be mixed or a small amount of sulfuric acid may be added. In the present invention, the hydrophilicity of the hydrophilic layer is further increased to 120
Heat treatment is performed at a temperature of ~200° C., thereby solidifying the coating liquid coating layer to form a water-retaining layer, and forming an interfacial crosslinked layer at the interface between the hydrophilic layer and the water-retaining layer. In the present invention, the polymer compound of acrylic acid or its α- or β-substituted product used for the water-retaining layer bottom is polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymer, polyacrylic acid These polymeric compounds can be selected from any water bathable polymeric compounds such as acid ester partial oxides, polymethacrylic acid ester partial oxides, and mixtures of two or more of the above polymers.
It is preferable that the average degree of polymerization is within the range of 500 to 2000, and in order to impregnate the cured hydrophilic layer with the water-soluble acrylic acid polymer, it is preferable to use a mixed solvent of water and a water-soluble organic solvent. . There is no particular restriction on the blending ratio of the organic solvent, and it may be selected so that the acrylic acid polymer can appropriately penetrate into the hydrophilic layer. The following are suitable as such organic solvents. Acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isobutyl ketone, schif-lohexanone, ethyl acetate, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, methyl cellosolve acetate, methanol, ethanol, propanol,
Improper tool, butanol, cyclohexanol,
These are dimethylformamide and dimethylacetamide. Before applying the water-retaining layer forming coating solution, the dry solid weight is generally 0.
．． 01-1. Oji/rr? It is preferably within the range of υ, Q5-=0.5. It is more preferable that it is in the range of u/-, and even more preferable that it is in the range of 0.05 to 112.9/-. If nl is smaller than 9/-, the effect of improving long-term storage stability and scumming prevention may be unsatisfactory. The coating solution for forming a water-retaining layer may be applied onto the hydrophilic layer, and the resulting laminate may be heated while the solvent is evaporated or removed. This heat treatment is preferably carried out at a temperature of 120 to 200°C for several seconds to 20 minutes.If the heating temperature is lower than 120°C, the crosslinking reaction between the acrylic acid polymer and the hydrophilic layer may not occur. If the heating temperature exceeds 200°C, the entire laminate may become deformed or warped.
Or cracks occur in the hydrophilic layer. The mechanism of the crosslinking reaction between the acrylic acid polymer and the urea resin and polyamide resin due to the heat treatment described above is not yet fully clear, or it is thought that it is basically caused by the following reaction. It will be done. In the method of the present invention, the water-retaining layer-forming coating liquid may contain at least one inorganic acid, and the water-retaining layer formed by solidifying and heating the applied coating liquid layer may contain this inorganic acid. , Inorganic acids include salt e, sulfuric acid, nitric acid, phosphoric acid, phosphorous acid, hydrofluoric acid, boric acid, hydrogen iodide, iodic acid, periodic acid, salt acid, perchloric acid, hydrogen bromide, Selenite, hydrogen cyanide, etc. can be mentioned, and the amount of the critical acid added depends on its concentration, but it is generally preferably 20% or less based on the weight of the water-soluble acrylic acid polymer. It is more preferable to range from 5 to 15 inches; if the amount of inorganic acid added is more than 20 inches, the multi-F-acid will be eluted during printing, which may reduce the printing durability of the printing plate. When a laminate having a support layer/hydrophilic layer/water retaining layer is heated in the presence of an inorganic acid, the formation of interfacial crosslinking between the acrylic acid polymer in the water retaining layer and the resin component in the hydrophilic layer is promoted. Heating AV to 120-150℃ 8F
ITt4@ is achieved by reducing the temperature to a relatively low temperature. In addition, the inorganic acid contained in the water-retaining layer improves the stability of the bright resin component of the photosensitive resin layer formed thereon, and also improves the stability of the bright resin component of the photosensitive resin layer formed thereon. In order to produce a lithographic printing plate which has the effect of neutralizing the alkaline developer 1 remaining in one layer and improving the stability of the 1liIiii gap 1-, the water retention layer of the lithographic printing plate support of the present invention is A TA + fat layer 1 containing a fat-sensitive component and capable of forming an image, for example, a photosensitive resin i-1, a heat-sensitive resin layer, an electrostatic toner transfer layer, etc., is formed on the heat-sensitive resin layer. wax. It contains a carbon blank, a mixture of pigments or dyes, and is used to form the desired image using a thermal printer. The photosensitive four-fingered material forming the photosensitive 1-sword resin is, for example, a mixture of 7-enol, diazo, and acrylic acid polymers described in JP-A No. 55-40406. Oil-soluble diazo! represented by formaldehyde condensate of p-diazodiphenylamine is also acceptable. 11 and JP-A-5O-3 (16 (No. 14 or Hibiki-kai tl&
50-1188 (which may be a mixture with the cutting composition described in Publication No. 12). It may have a water-resistant layer provided between the surface and the hydrophilic layer and/or a water-resistant backing layer formed on the back surface of the support layer.In the planographic plate of FIG. 2, the support layer] Waterproof layer 6 on the top surface of
is formed, and on its upper surface, 1 m of hydrophilic layer 2 interfacial bridge! 5
In the printing plate shown in FIG. 3, the upper surface of the water-retaining layer 3 forms a hydrophilic surface on which a photosensitive layer can be formed. The image 7 is formed on top, and the hydrophilic surface of the water-retaining layer 3 is exposed, and this water-resistant layer, which acts as a water-retaining surface for dampening water during printing, is made of an aldehyde condensate of polyvinyl chloride, polyurethane, and polyvinyl alcohol. , acrylic ester-styrene copolymer, methacrylic ester-styrene copolymer, or styrene-butadiene copolymer, or aluminum foil. The support l used in the printing plate of this embodiment may be any of the above-mentioned materials for the support layer, but
In particular, support layer materials with relatively low water resistance, such as paper, can also be used. The water-resistant resin contains 0.3 to 4.0 times the solid content of the resin in order to improve workability and smoothness.
Preferably, titanium dioxide or the like may be mixed in an amount of 0.8 to zO times the weight, and the amount of replacement of the water-resistant layer is preferably 5 to 209/rr, preferably %8 to 129/rr? [Examples] The present invention will be explained below with reference to Examples. “Part” in Examples
Unless otherwise specified, "scratches" and "scratches" are due to the weight of Example 1, which has a basis weight of 150. ! //FFg” paper (N/L
=! To form a water-resistant layer using '5o15(1), apply an acrylic resin emulsion to both sides of the paper on one side. Apply it evenly and dry. On one side of this coated paper, a hydrophilic layer coating solution with the following composition was prepared and applied onto the water-resistant layer, followed by heat treatment at 150°C for 3 minutes.The dry solid content of the thus formed hydrophilic layer The weight was ]3y/ze. Set FR part anatase type Tie, 50n polyacrylic acid soda 2 water
1200 water-soluble polyamide dark fat
400 (solid content) (10th scale methylol-modified nylon 6) Cation modified urea resin 200 (solid content) (
Section 10 diethanolamine modified urea resin) N) i4C1
10 Apply water retention 1 coating liquid with the following composition on the hydrophilic stone: o, 11/
rr? The coating solution coating layer was dried and heated at 140°C for 5 minutes to form a water-retaining layer. Composition Water-soluble acrylic acid polymer 5.0 (methacrylic acid group 3
0Lfb Polymerization degree 1.0110') Phosphoric acid (85T)
1.5 Water 100 Methyl ethyl ketone 25 Inglobil alcohol 25 An image was formed on the water-retaining layer by an electrostatic dry toner transfer method using a commercially available copying machine. The obtained lithographic printing plate was installed in a normal offset master printing machine, and the plate surface was wiped with a 0.11 aqueous solution of potassium hydroxide to make the water-retaining layer hydrophilic. As a result of printing using this printing plate, fi119 copies were obtained.3 ．． (1n0 clear printed matter with no background stains was obtained. Example 2 The same operation as in Example 1 was carried out. However, the coating liquid for the water-retaining layer formed on Hydrophilic 1 had the following composition. Hydrochloric acid (2N aqueous solution) 1.0 Water Inn Methyl ethyl ketone 25 Isopropyl alcohol 25 The water-retaining layer coating liquid layer is dried and heated at 5°C for 30 seconds, and the resulting water-retaining layer is dried 4 & solid II
The amount was U, 05.9/-. A photosensitive layer coating solution was applied to the water retaining layer. A photosensitive layer coating solution was prepared as follows. 4-diazodiphenylamine @acid 2 in 200 parts of phosphoric acid
Add 30 parts with stirring and disperse well.Next, add 30 parts of paraformaldehyde and heat at 24% at 40°C.
Stir for a time to react fcn then phenol 94
Then add 15 parts of paraformaldehyde and 200 parts of phosphoric acid, and react at 50°C for 24 hours while stirring well.9 Disperse the resulting reaction mixture in a large amount of water, filter the precipitate, and wash with water. Then, 310 parts of yellow photosensitive diazo resin was obtained.The storage stability of this diazo resin was good, and no change was observed even after it was left at room temperature for 6 months. Textured photosensitive diazo resin and methyl cellulose are dissolved in a solid ratio of 3:1 in a mixed solvent of 60 parts water, 25 parts methyl ethyl ketone, 10 parts isopropyl alcohol, and 5 parts ethanol to prepare a photosensitive composition coating solution. made. This coating solution was coated on the water-retaining layer with a dry solid MKt of 0.7 M/m'', and a coating solution layer of 1 (a negative foam photosensitive lithographic plate prepared by drying at 10° C. for 2 minutes) was applied. A negative film was brought into close contact with the printing plate, and exposed for 20 seconds from a distance of lWL using a 2kW metal halide light source.Next, the exposed plate surface was evenly wetted with a urethane sponge containing a sodium carbonate IJium bath solution for ZO, and This printing plate was attached to an offset printing machine and printed, and a clear image with no background smudges was obtained, and even after printing 10,000 sheets, no image was observed to fall off. Example 3 Paper with a basis weight of 150 F/-, which has excellent size and water resistance, was used as the support layer material of the support, and one side of this paper was laminated with υ high-density polyethylene to a thickness of 15 μ by an extruder method. A corona discharge was applied to this polyethylene laminate 1 on which a water-resistant layer was formed, and the surface energy was 40 d.
It was activated to become in/cm. The following fEi [hydrophilic layer coating solution] is applied on the water-resistant layer and heat treated at 150°C for 2 minutes to form a parent layer and its dry solid content 1.
The amount was 20.1//rrt''.The following is the bottom aluminum hydroxide 500 valve handle (Fetus)
1 (1 water 1
20ONH4C/15 On the hydrophilic layer thus formed, a water retaining layer identical to that described in Example 2 was formed under the same conditions. On this water-retaining layer, apply the negative-tone photosensitive layer coating solution shown below using a Mayer par.Margin composition: Part β-hydroxyethyl methacrylate/Solution p-Hexafluorinated triphosphoric acid of a condensate of diazodiphenylamine and paraformaldehyde. Salt methyl seronurup 100 Dimethyl sulfoxide 20 Dry the photosensitive layer coating solution layer at 90°C for 3 minutes to give a concentration of 1.0.9 to 1.0 g/m2r.
? The lower surface of the support layer on which the photosensitive layer of
4 lum was attached to form a water-resistant layer. A negative film (having a predetermined pattern) was vacuum-adhered onto the photosensitive layer of the obtained lithographic printing plate material, and a J&I high-pressure mercury lamp 2
kW, 1 minute from a distance of 171 & 3! I paid it back. The exposed plate surface was developed using a commercially available water-soluble alkaline developer to form a face stone to obtain a printing plate. When this printing plate was installed in an ordinary offset printing machine and printed in a conventional manner, more than 10,000 clear and smear-free prints were successively obtained. [Effects of the Invention] In the lithographic printing plate support of the present invention, the hydrophilic layer and the water-retaining layer are strongly bonded via a special crosslinked layer, and the water-retaining layer and the water-retaining layer are bonded together with the image layer formed thereon. The lithographic printing plate support of the present invention is particularly useful as a printing plate support for light printing. Extremely useful for the body 0

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of one embodiment of the planographic printing plate of the present invention, FIG. 2 is an explanatory cross-sectional view of another embodiment of the planographic printing plate of the present invention, and FIG. FIG. 2 is a cross-sectional explanatory diagram after exposure and development when a lithographic printing plate is used as a printing plate. 1...Supporting layer, 2...Hydrophilic layer, 3...
...Water retention fd h4...Backing layer, 5...
...Interfacial crosslinked layer, 6...Waterproof layer, 7...
・Image ri

Claims (1)

[Scope of Claims] 1. a support layer; formed on at least one surface of the support layer;
40 parts by weight of at least one urea resin, and 6
a hydrophilic layer made of a mixture containing 0 to 95 parts by weight of a resin component made of at least one polyamide resin, and a pigment component; and a hydrophilic layer formed on the hydrophilic layer and containing acrylic acid;
a water-retaining layer containing at least one non-crosslinked water-soluble acrylic acid polymer containing at least one member selected from α- and β-substituted products thereof as a polymerization component, the hydrophilic layer and the water-retaining layer. A portion of the acrylic acid polymer, a portion of the urea resin, and a portion of the polyamide resin are mixed at the interface with the acrylic acid polymer, and a crosslink is formed between them. A lithographic printing support. 2. The support according to claim 1, wherein the water-retaining layer contains at least one inorganic acid. 3. Claim 2, wherein the amount of the inorganic acid is within the range of 1 to 20% based on the weight of the acrylic acid polymer.
Support described in Section. 4. The inorganic acid may be hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphorous acid, hydrofluoric acid, boric acid, hydrogen iodide, iodic acid, periodic acid, chloric acid, perchloric acid, hydrogen bromide, or The support according to claim 1, which is selected from selenic acid and hydrogen cyanide. 5. The support according to claim 1, wherein the weight of the water retaining layer is within the range of 0.01 to 1.0 g/m^2. 6. On at least one surface of the support layer, a resin component consisting of 5 to 40 parts by weight of at least one urea resin and 60 to 95 parts by weight of at least one polyamide resin, and a pigment component. forming a hydrophilic layer consisting of a mixture containing, on the hydrophilic layer, at least one water-soluble acrylic acid containing at least one selected from acrylic acid and its α- and β-substituted products as a polymerization component; A coating layer of a coating liquid containing a system polymer is formed, and the resulting laminate is heated to 120~
Heat treatment is performed at a temperature of 200° C., thereby solidifying the coating liquid coating layer to form a water-retaining layer, and at the interface between the hydrophilic layer and the water-retaining layer, a portion of the acrylic acid polymer and the urea 1. A method for producing a support for a lithographic printing plate, comprising: allowing a portion of the resin and a portion of the polyamide resin to interpenetrate with each other, and forming a crosslinking bond therebetween. 7. The method according to claim 6, wherein the water retaining layer contains at least one inorganic acid, and the heat treatment is performed at a temperature of 120 to 150°C.