Method of making lithographic printing plate and photopolymer composition

A method of making a lithographic printing plate by forming images at the surface of a lithographic printing plate precursor by means of a thermal head, with the lithographic printing plate precursor having on a support a recording layer comprising a polymer having at least either carboxylic acid or carboxylate groups capable of causing thermal decarboxylation; and a photopolymer composition for recording by exposure to infrared laser beams, wherein a thermally decarboxylation-causing polymer and a photothermal converter are comprised.

FIELD OF THE INVENTION
 The present invention relates to a method of making a lithographic printing
 plate and a photopolymer composition. In particular, the invention is
 concerned with a method of making a lithographic printing plate by the use
 of a lithographic printing plate precursor which comprises a support and
 an ink-receptive recording layer (image forming layer) and enables the
 platemaking to be performed by scanning exposure based on digital signals
 without additional wet processing, and further with a photopolymer
 composition used for the lithographic printing plate precursor.
 BACKGROUND OF THE INVENTION
 In general, the lithographic printing plate is constituted of a lipophilic
 imaging area to receive ink in the printing step and a hydrophilic
 non-imaging area to receive dampening water applied thereto prior to the
 inking step. For making such a lithographic printing plate, a
 presensitized plate (abbreviated as "PS plate" hereinafter) comprising a
 hydrophilic support and a ink-receptive photopolymer layer provided
 thereon has been widely used as a lithographic printing plate precursor.
 In a conventional method adopted therein for making the intended printing
 plate, mask exposure is generally carried out via a lith film, and then
 the non-imaging area is dissolved and removed with a developer.
 In recent years, the technology to digitize image information has been
 widely spread, wherein the image information is electronically processed,
 stored and outputted by the use of a computer. And a variety of new
 image-output systems which can keep up with such digitization technology
 have become practical. Under these circumstances, it has been anxiously
 awaited to develop the computer-to-plate technology which enables the
 direct platemaking to be performed by scanning highly directional actinic
 rays, such as laser beams, corresponding to the digitized image
 information, but not using a lith film. And the production of printing
 plate precursors suitable for such technology has been one of important
 technical problems.
 On the other hand, the conventional process of making a printing plate by
 the use of a PS plate necessitates a step of removing the non-imaging area
 by dissolution after exposure and, in general, further requires an
 after-processing step of washing the development-processed printing plate
 with wash water, a rinsing solution containing a surfactant or a
 desensitizing solution containing gum arabic and a starch derivative. Such
 an additional wet processing requirement has been recognized as leaving
 room for improvement. Lately in particular, consideration of global
 environment has been a matter of great concern of the whole industrial
 world. From the viewpoints of friendliness to the environment and
 streamlining the platemaking process accompanied by the digitization of
 image information, it has been desired more strongly than ever to render
 the processing steps for platemaking simple, dry or unnecessary.
 With respect to the method of making a printing plate by means of scanning
 exposure, the utilization of actinic rays having high energy density, such
 as electron beams and high-output laser, has been proposed in addition to
 the utilization of a high speed photosensitive material. In recent years,
 it has become possible to get high-output solid laser devices, such as a
 semiconductor laser device and a YAG laser device, at low prices. As a
 result, the bright future of computer-to-plate systems utilizing such
 solid laser devices has come to be understood. The characteristic of high
 energy density exposure systems consists in that various phenomena, other
 than the photo reactions taking place in the low to medium energy density
 exposure-utilized photosensitive materials, can be applied to development.
 Specifically, not only a chemical change but also a structural change,
 such as change in phase or form, can be utilized for development. In
 general, such a high energy density exposure-utilized recording system is
 referred to as heat mode recording. This is because, in many high energy
 density exposure systems, it is believed that the energy of light absorbed
 by a photosensitive material is converted into heat, and the heat thus
 produced causes the intended development. The heat mode recording system
 has a great advantage in having potentialities for making the processing
 steps simple, dry or unnecessary. These potentialities are based on that
 the phenomena utilized for the image recording in a heat mode
 photosensitive material don't occur in a substantial sense under exposure
 to ordinary intensity of light or under temperatures of ordinary
 environment, so that no step for fixing images is required after exposure.
 As a desirable method of making a lithographic printing plate on a basis of
 heat mode recording, a method proposal was advanced, wherein a precursor
 constituted of a water-receptive layer and an ink-receptive layer is
 subjected to heat mode exposure and only one layer of them is removed
 imagewise, thereby developing an imagewise difference between
 water-receptive and ink-receptive areas. This method can provide the
 precursor for printing plate showing relatively good printing properties
 in addition to the possibility of having scanning exposure suitability and
 rendering processing steps unnecessary or dry.
 With respect to examples of such a lithographic printing plate precursor,
 JP-A-5-77574, JP-A-4-125189, U.S. Pat. No. 5,187,047 and JP-A-62-195646
 (the term "JP-A" as used herein means an "unexamined published Japanese
 patent application") disclose using sulfonated polyolefin films as plate
 material requiring no development-processing and making printing plates
 through changes in hydrophilic properties of the film surface by thermal
 writing. More specifically, those systems form images through the
 desulfonation of sulfonic acid groups caused in the sensitive material
 surface by thermal writing.
 In addition, U.S. Pat. No. 4,081,572 discloses the method of forming images
 through the dehydration ring closure caused in the polymers having
 carboxylic acid groups by exposure to heat or laser beams.
 All those plate materials are hydrophilic films before exposure, but can be
 converted into hydrophobic ones by exposure. In other words, they are
 examples of the so-called polarity conversion negative press plate. The
 characteristic thereof is no need for development-processing.
 However, the plate materials used in those conventional arts are lacking in
 thermal reactivity, so that it takes a long time to form images therein
 due to low sensitivity. Further, those materials have small discrimination
 between hydrophilic and hydrophobic areas, so that the printing plates
 made therefrom have nothing but insufficient water-receptivity or low
 image strength. In other words, sensitive materials which can afford
 satisfying sensitivity, scum resistance and press life cannot be obtained
 by those conventional arts.
 SUMMARY OF THE INVENTION
 Therefore, an object of the invention is to provide a lithographic printing
 plate to be made by short scanning exposure, or by writing with low-energy
 heat mode exposure, and ensuring excellent image-area strength and scum
 resistance in the lithographic printing plate made.
 Another object of the invention is to provide a lithographic printing plate
 excellent in image-area strength and scum resistance by the use of a
 lithographic printing plate precursor which has excellent storage
 stability as well as high suitability for low-energy heat mode exposure,
 but does not necessarily require development-processing.
 As a result of our intensive research for solving the problems of the
 conventional arts, it has been found that a lithographic printing plate
 precursor suitable for making a lithographic printing plate by heat mode
 exposure can be obtained by introducing therein a recording layer
 comprising a photothermal converter and a polymer containing functional
 groups having excellent thermal reactivity and causing decarboxylation by
 heating, thereby achieving the present invention.
 More specifically, the objects of the invention are attained by the
 following embodiments (1) to (3):
 (1) A method of making a lithographic printing plate by exposing a
 lithographic printing plate precursor to infrared laser beams to form
 images at the surface thereof, with the lithographic printing plate
 precursor being provided with a recording layer comprising a photothermal
 converter and a polymer having at least either carboxylic acid or
 carboxylate groups capable of causing thermal decarboxylation.
 (2) A method of making a lithographic printing plate by forming images at
 the surface of a lithographic printing plate precursor by means of a
 thermal head, with the lithographic printing plate precursor being
 provided with a recording layer comprising a polymer having at least
 either carboxylic acid or carboxylate groups capable of causing thermal
 decarboxylation.
 (3) A photopolymer composition for recording images by exposure to infrared
 laser beams, with the composition comprising a photothermal converter and
 a thermal decarboxylation-causing polymer that comprises at least either
 constitutional repeating units represented by the following formula (1) or
 constitutional repeating units represented by the following formula (2):
 ##STR1##
 wherein X represents a group 4, 5 or 6 element, an oxide thereof, a sulfide
 thereof, a selenide thereof or a telluride thereof; P represents a
 repeating unit constituting the polymer main chain; --L-- represents a
 divalent linkage group; R.sup.1 and R.sup.2, which are the same or
 different, each represent a monovalent group; and M represents an alkali
 metal, an alkaline earth metal or an onium.
 DETAILED DESCRIPTION OF THE INVENTION
 The invention is described below in detail.
 The polymer used in the present image formation layer has no particular
 restrictions, provided that it has at least either carboxylic acid or
 carboxylate groups capable of causing thermal decarboxylation. Preferably,
 the polymer used in the invention is either a polymer comprising
 constitutional repeating units represented by the following formula (1) or
 a polymer comprising constitutional repeating units represented by the
 following formula (2), or a mixture thereof:
 ##STR2##
 wherein X represents a group 4, 5 or 6 element, an oxide thereof, a sulfide
 thereof, a selenide thereof or a telluride thereof; P represents a
 repeating unit constituting the polymer main chain; --L-- represents a
 divalent linkage group; R.sup.1 and R.sup.2, which are the same or
 different, each represents a hydrogen atom or a monovalent group; and M
 represents an alkali metal, an alkaline earth metal or an onium.
 Specific examples of R.sup.1 and R.sup.2 include a hydrogen atom and
 monovalent groups constituted of nonmetal atoms, and preferred examples of
 the monovalent groups include a halogen atom (F, Br, Cl, I), a hydroxyl
 group, an alkoxy group, an aryloxy group, a mercapto group, an alkylthio
 group, an arylthio group, an alkyldithio group, an aryldithio group, an
 amino group, an N-alkylamino group, an N,N-diarylamino group, an
 N-alkyl-N-arylamino group, an acyloxy group, a carbamoyloxy group, an
 N-alkylcarbamoyloxy group, an N-arylcarbamoyloxy group, an
 N,N-dialkylcarbamoyloxy group, an N,N-diarylcarbamoyloxy group, an
 N-alkyl-N-arylcarbamoyloxy group, an alkylsulfoxy group, an arylsulfoxy
 group, an acylthio group, an acylamino group, an N-alkylacylamino group,
 an N-acrylacylamino group, a ureido group, an N'-alkylureido group, an
 N',N'-dialkylureido group, an N'-arylureido group, an N',N'-diarylureido
 group, an N'-alkyl-N'-arylureido group, an N-alkylureido group, an
 N-arylureido group, an N'-alkyl-N-alkylureido group, an
 N'-alkyl-N-arylureido group, an N',N'-dialkyl-N-alkylureido group,
 N',N'-dialkyl-N-arylureido group, an N'-aryl-N-alkylureido group, an
 N'-aryl-N-arylureido group, an N',N'-diaryl-N-alkylureido group, an
 N',N'-diaryl-N-arylureido group, an N'-alkyl-N'-aryl-N-alkylureido group,
 an N'-alkyl-N'-aryl-N-arylureido group, an alkoxycarbonylamino group, an
 aryloxycarbonylamino group, an N-alkyl-N-alkoxycarbonylamino group, an
 N-alkyl-N-aryloxycarbonylamino group, an N-aryl-N-alkoxycarbonylamino
 group, an N-aryl-N-aryloxycarbonylamino group, a formyl group, an acyl
 group, a carboxyl group, an alkoxycarbonyl group, an aryloxycarbonyl
 group, a carbamoyl group, an N-alkylcarbamoyl group, an N-dialkylcarbamoyl
 group, an N-arylcarbamoyl group, an N,N-diarylcarbamoyl group, an
 N-alkyl-N-arylcarbamoyl group, an alkylsulfinyl group, an arylsulfinyl
 group, an alkylsulfonyl group, an arylsulfonyl group, a sulfo group
 (--SO.sub.3 H) and a conjugate base group thereof (hereinafter referred to
 as "a sulfonato group"), an alkoxysulfonyl group, an arylsulfonyl group, a
 sulfinamoyl group, an N-alkylsulfinamoyl group, an N,N-dialkylsulfinamoyl
 group, an N-arylsulfinamoyl group, an N,N-diarylsulfinamoyl group, an
 N-alkyl-N-arylsulfinamoyl group, a sulfamoyl group, an N-alkylsulfamoyl
 group, N,N-dialkylsulfamoyl group, an N-arylsulfamoyl group, an
 N,N-diarylsulfamoyl group, an N-alkyl-N-arylsulfamoyl group, a phosphono
 group (--PO.sub.3 H.sub.2) and a conjugate base group thereof (hereinafter
 referred to as "a phosphonato group"), a dialkylphosphono group
 (--PO.sub.3 (alkyl).sub.2), a diarylphosphono group (--PO.sub.3
 (alkyl).sub.2), an alkylarylphosphono group (--PO.sub.3 (alkyl) (aryl)), a
 monoalkylphosphono group (--PO.sub.3 H(alkyl)) and a conjugate base group
 thereof (hereinafter referred to as "an alkylphosphonato group"), a
 monoarylphosphono group (--PO.sub.3 H(aryl)) and a conjugate base group
 thereof (hereinafter referred to as "an arylphosphonato group"), a
 phosphonoxy group (--OPO.sub.3 H.sub.2) and a conjugate base group thereof
 (hereinafter referred to as "a phosphonatoxy group"), a dialkylphosphonoxy
 group (--OPO.sub.3 (alkyl).sub.2), a diarylphosphonoxy group (--OPO.sub.3
 (aryl).sub.2), an alkylarylphosphonoxy group (--OPO.sub.3 (alkyl) (aryl)),
 a monoalkylphosphonoxy group (--OPO.sub.3 H(alkyl)) and a conjugate base
 group thereof (hereinafter referred to as "an alkylphosphonatoxy group"),
 a monoarylphosphonoxy group (--OPO.sub.3 H(aryl)) and a conjugate base
 group thereof (hereinafter referred to as "an arylphosphonatoxy group), a
 cyano group, a nitro group, an aryl group, an alkenyl group and an alkynyl
 group.
 Among the above-described specific examples of R.sup.1 and R.sup.2 more
 preferred are a hydrogen atom, an alkoxy group, an amino group, an aryl
 group and an alkyl group, and the specific examples of the alkyl group
 include straight-chain, branched and cyclic alkyl groups containing 1 to
 20 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl,
 heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl,
 octadecyl, eicosyl, ispropyl, isobutyl, s-butyl, t-butyl, isopentyl,
 neopentyl, 1-methylbutyl, isohexyl, 2-ethylhexyl, 2-methylhexyl,
 cyclohexyl, cyclopentyl and 2-norbornyl groups. Of these groups, the
 straight-chain alkyl groups containing 1 to 12 carbon atoms, the branched
 alkyl groups containing 3 to 12 carbon atoms and the cycloalkyl groups
 containing 5 to 10 carbon atoms are particularly preferred over the
 others. Further, these alkyl groups may have one or more substituents.
 As the substituents for the substituted alkyl groups, monovalent groups
 constituted of nonmetal atoms are used. Preferred examples include a
 halogen atom (F, Br, Cl, I), a hydroxyl group, an alkoxy group, an aryloxy
 group, a mercapto group, an alkylthio group, an arylthio group, an
 alkyldithio group, an aryldithio group, an amino group, an N-alkylamino
 group, an N,N-diarylamino group, an N-alkyl-N-arylamino group, an acyloxy
 group, a carbamoyloxy group, an N-alkylcarbamoyloxy group, an
 N-arylcarbamoyloxy group, an N,N-dialkylcarbamoyloxy group, an
 N,N-diarylcarbamoyloxy group, an N-alkyl-N-arylcarbamoyloxy group, an
 alkylsulfoxy group, an arylsulfoxy group, an acylthio group, an acylamino
 group, an N-alkylacylamino group, an N-acrylacylamino group, an ureido
 group, an N'-alkylureido group, an N',N'-dialkylureido group, an
 N'-arylureido group, an N',N'-diarylureido group, an
 N'-alkyl-N'-arylureido group, an N-alkylureido group, an N-arylureido
 group, an N'-alkyl-N-alkylureido group, an N'-alkyl-N-arylureido group, an
 N',N'-dialkyl-N-alkylureido group, N',N'-dialkyl-N-arylureido group, an
 N'-aryl-N-alkylureido group, an N'-aryl-N-arylureido group, an
 N',N'-diaryl-N-alkylureido group, an N',N'-diaryl-N-arylureido group, an
 N'-alkyl-N'-aryl-N-alkylureido group, an N'-alkyl-N'-aryl-N-arylureido
 group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, an
 N-alkyl-N-alkoxycarbonylamino group, an N-alkyl-N-aryloxycarbonylamino
 group, an N-aryl-N-alkoxycarbonylamino group, an
 N-aryl-N-aryloxycarbonylamino group, a formyl group, an acyl group, a
 carboxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a
 carbamoyl group, an N-alkylcarbamoyl group, an N-dialkylcarbamoyl group,
 an N-arylcarbamoyl group, an N,N-diarylcarbamoyl group, an
 N-alkyl-N-arylcarbamoyl group, an alkylsulfinyl group, an arylsulfinyl
 group, an alkylsulfonyl group, an arylsulfonyl group, a sulfo group
 (--SO.sub.3 H) and a conjugate base group thereof (hereinafter referred to
 as "a sulfonato group"), an alkoxysulfonyl group, an arylsulfonyl group, a
 sulfinamoyl group, an N-alkylsulfinamoyl group, an N,N-dialkylsulfinamoyl
 group, an N-arylsulfinamoyl group, an N,N-diarylsulfinamoyl group, an
 N-alkyl-N-arylsulfinamoyl group, a sulfamoyl group, an N-alkylsufamoyl
 group, N,N-dialkylsulfamoyl group, an N-arylsulfamoyl group, an
 N,N-diarylsulfamoyl group, an N-alkyl-N-arylsulfamoyl group, a phosphono
 group (--PO.sub.3 H.sub.2) and a conjugate base group thereof (hereinafter
 referred to as "a phosphonato group"), a dialkylphosphono group
 (--PO.sub.3 (alkyl).sub.2), a diarylphosphono group (--PO.sub.3
 (aryl).sub.2), an alkylarylphosphono group (--PO.sub.3 (alkyl) (aryl)), a
 monoalkylphosphono group (--PO.sub.3 H(alkyl)) and a conjugate base group
 thereof (hereinafter referred to as "an alkylphosphonato group"), a
 monoarylphosphono group (--PO.sub.3 H(aryl)) and a conjugate base group
 thereof (hereinafter referred to as "an arylphosphonato group"), a
 phosphonoxy group (--OPO.sub.3 H.sub.2) and a conjugate base group thereof
 (hereinafter referred to as "a phosphonatoxy group"), a dialkylphosphonoxy
 group (--OPO.sub.3 (alkyl).sub.2), a diarylphosphonoxy group (--OPO.sub.3
 (aryl).sub.2), an alkylarylphosphonoxy group (--OPO.sub.3 (alkyl) (aryl)),
 a monoalkylphosphonoxy group (--OPO.sub.3 H(alkyl)) and a conjugate base
 group thereof (hereinafter referred to as "an alkylphosphonatoxy group"),
 a monoarylphosphonoxy group (--OPO.sub.3 H(aryl)) and a conjugate base
 group thereof (hereinafter referred to as "an arylphosphonatoxy group), a
 cyano group, a nitro group, an aryl group, an alkenyl group and an alkynyl
 group.
 Examples of an alkyl moiety in those substituent groups include the alkyl
 groups recited above and those of an aryl moiety in those substituent
 groups include a phenyl group, a biphenyl group, a naphthyl group, a tolyl
 group, a xylyl group, a mesityl group, a cumenyl group, a chlorophenyl
 group, a bromophenyl group, a chloromethylphenyl group, a hydroxyphenyl
 group, a methoxyphenyl group, an ethoxyphenyl group, a phenoxyphenyl
 group, an acetoxyphenyl group, a benzoyloxyphenyl group, a
 methylthiophenyl group, a phenylthiophenyl group, a methylaminophenyl
 group, a dimethylaminophenyl group, an acetylaminophenyl group, a
 carboxyphenyl group, a methoxycarbonylphenyl group, an
 ethoxyphenylcarbonyl group, a phenoxycarbonylphenyl group, an
 N-phenylcarbamoylphenyl group, a phenyl group, a cyanophenyl group, a
 sulfophenyl group, a sulfonatophenyl group, a phosphonophenyl group and a
 phosphonatophenyl group. Examples of an alkenyl group include a vinyl
 group, a 1-propenyl group, a 1-butenyl group, a cinnamyl group and a
 2-chloro-1-ethenyl group. Examples of an alkynyl group include an ethynyl
 group, a 1-propynyl group, a 1-butynyl group and a trimethylsilylethynyl
 group. As examples of G.sup.1 in G.sup.1 CO-- representing an acyl group,
 mention may be made of a hydrogen atom and the above-recited alkyl and
 aryl groups. Of those substituent groups, halogen atoms (F, Br, Cl, I),
 alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups,
 N-alkylamino groups, N,N-dialkylamino group, acyloxy groups,
 N-alkylcarbamoyloxy groups, N-arylcarbamoyloxy group, acylamino groups, a
 formyl group, acyl groups, a carboxyl group, alkoxycarbonyl groups,
 aryloxycarbonyl groups, a carbamoyl group, N-alkylcarbamoyl groups,
 N,N-dialkylcarbamoyl groups, N-arylcarbamoyl groups,
 N-alkyl-N-arylcarbamoyl groups, a sulfo group, a sulfonato group, a
 sulfamoyl group, N-alkylsulfamoyl groups, N,N-dialkylsulfamoyl groups,
 N-arylsulfamoyl groups, N-alkyl-N-arylsulfamoyl groups, a phosphono group,
 a phosphonato group, dialkylphosphono groups, diarylphosphono groups,
 monoalkylphosphono groups, alkylphosphonato groups, monoarylphosphono
 groups, arylphosphonato groups, a phosphonoxy group, a phosphonatoxy
 group, aryl groups and alkenyl groups are much preferred over the others.
 Further, the monovalent group as R.sup.1 and R.sup.2 each may be a
 substituted alkyl group. Examples of an alkylene moiety in such a
 substituted alkyl group include divalent organic residues formed by
 removing one hydrogen atom from each of the C.sub.1-20 alkyl groups as
 recited above, preferably C.sub.1-12 straight-chain alkylene groups,
 C.sub.3-12 branched alkylene groups and C.sub.5-10 cycloalkylene groups.
 Suitable examples of a substituted alkyl group formed by combining a
 substituent and an alkylene group include chloromethyl, bromomethyl,
 2-chloroethyl, trifluoromethyl, methoxymethyl, methoxyethoxyethyl,
 allyloxymethyl, phenoxymethyl, methylthiomethyl, tolylthiomethyl,
 ethylaminoethyl, diethylaminopropyl, morpholinopropyl, acetyloxymethyl,
 benzoyloxymethyl, N-cyclohexylcarbamoyloxyethyl,
 N-phenylcarbamoyloxyethyl, acetylaminoethyl, N-ethylbenzoylaminopropyl,
 2-hydroxyethyl, 2-hydroxypropyl, carboxypropyl, methoxycarbonylethyl,
 allyloxycarbonylbutyl, chlorophenoxycarbonylmethyl, carbamoylmethyl,
 N-methylcarbamoylethyl, N,N-dipropyl-carbamoylmethyl,
 N-(methoxyphenyl)carbamoylethyl, N-methyl-N-(sulfophenyl)carbamoylmethyl,
 sulfobutyl, sulfonatobutyl, sulfamoylbutyl, N-ethylsulfamoylmethyl,
 N,N-dipropylsulfamoylpropyl, N-tolylsulfamoylpropyl,
 N-methyl-N-(phosphonophenyl)sulfamoyloctyl, phosphonobutyl,
 phosphonatohexyl, diethylphosphonobutyl, diphenylphosphono-propyl,
 methylphosphonobutyl, methylphosphonatobutyl, triphosphonohexyl,
 tolylphosphonatohexyl, phosphonoxy-propyl, phosphonatooxybutyl, benzyl,
 phenetyl, .alpha.-methylbenzyl, 1-methyl-1-phenylethyl, p-methylbenzyl,
 cinnamyl, allyl, 1-propenylmethyl, 2-butenyl, 2-methylallyl,
 2-methyl-propenylmethyl, 2-propenyl, 2-butynyl and 3-butynyl groups.
 The aryl group as a monovalent group represented by R.sup.1 and R.sup.2
 each includes a group having one benzene ring, a group in which two or
 three benzene rings are condensed, and a group in which a benzene ring and
 a 5-membered unsaturated ring are condensed. As examples of such a group,
 mention may be made of a phenyl group, a naphthyl group, an anthryl group,
 a phenanthryl group, an indenyl group, an acenaphthenyl group and a
 fluorenyl group. Of these groups, a phenyl group and a naphthyl group are
 preferred over the others. Besides the carbocyclic aryl groups as recited
 above, the aryl group can include heterocyclic aryl groups. In such
 heterocyclic aryl groups, 3 to 20 carbon atoms and 1 to 5 hetero atoms are
 contained, and further a benzene ring may be contained in a condensed
 state. Examples of such a heterocyclic aryl group include a pyridyl group,
 a furyl group, a quinolyl group, a benzofuryl group, a thioxanthone group
 and a carbazole group.
 Those aryl groups each can have a monovalent nonmetal atomic group as
 substituent group on a ring-forming carbon atom. Suitable examples of such
 a substituent group include the alkyl groups as recited above, the
 substituted alkyl groups as recited above and the substituent groups
 present therein. As appropriate examples of such a substituted aryl group,
 mention may be made of biphenyl, tolyl, xylyl, mesityl, cumenyl,
 chlorophenyl, bromophenyl, fluorophenyl, chloromethylphenyl,
 trifluoromethylphenyl, hydroxyphenyl, methoxyphenyl, methoxyethoxyphenyl,
 allyloxyphenyl, phenoxyphenyl, methylthiophenyl, tolylthiophenyl,
 ethylaminophenyl, diethylaminophenyl, morpholinophenyl, acetyloxyphenyl,
 benzoyloxyphenyl, N-cyclohexylcarbamoyloxyphenyl,
 N-phenylcarbamoyloxyphenyl, acetylaminophenyl, N-methylbenzoylaminophenyl,
 carboxyphenyl, methoxycarbonyl-phenyl, allyloxycarbonylphenyl,
 chlorophenoxycarbonylphenyl, carbamoylphenyl, N-methylcarbamoylphenyl,
 N,N-dipropyl-carbamoylphenyl, N-(methoxyphenyl)carbamoylphenyl,
 N-methyl-N-(sulfophenyl)carbamoylphenyl, sulfophenyl, sulfonatophenyl,
 sulfamoylphenyl, N-ethylsulfamoylphenyl, N,N-dipropylsulfamoylphenyl,
 N-tolylsulfamoylphenyl, N-methyl-N-(phosphonophenyl)sulfamoylphenyl,
 phosphonophenyl, phosphonatophenyl, diethylphosphonophenyl,
 diphenylphosphonophenyl, methylphosphonophenyl, methylphosphonatophenyl,
 tolylphosphonophenyl, tolylphosphonatophenyl, allylphenyl,
 1-propenylmethylphenyl, 2-butenylphenyl, 2-methylallylphenyl,
 2-methylpropenylphenyl, 2-propynylphenyl, 2-butynylphenyl and
 3-butynylphenyl groups.
 Suitable examples of --X-- include --O--, --S--, Se--, --NR.sup.3 --,
 --CO--, --SO--, --SO.sub.2 --, and --PO--. Of these groups, --CO--, --SO--
 and --SO.sub.2 -- are preferred in particular over the others from the
 viewpoint of thermal reactivity.
 The group appropriate for R.sup.3 may be the same as or different from
 R.sup.1 or R.sup.2, and it can be selected from the groups recited above
 as examples of R.sup.1 or R.sup.2.
 The divalent linkage group represented by L is constituted of 1 to 60
 carbon atoms, 0 to 10 nitrogen atoms, 0 to 50 oxygen atoms, 1 to 100
 hydrogen atoms and 0 to 20 sulfur atoms. Examples of such a divalent
 linkage group include groups formed by combining two or more of the
 following structural units:
 ##STR3##
 M has no particular restriction as far as it is a cation, but it is
 desirable for M to be a monovalent to tetravalent metal cation or an
 ammonium ion represented by the following formula (3):
 ##STR4##
 wherein R.sup.4, R.sup.5, R.sup.6 and R.sup.7, which may be the same or
 different, each represent a monovalent group.
 Examples of a monovalent to tetravalent metal cation represented by M
 include Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Fr.sup.+,
 Be.sup.2+, Mg.sup.2+, Ca.sup.2+, Sr.sup.2+, Ba.sup.2+, Ra.sup.2+,
 Cu.sup.+, Cu.sup.2+, Ag.sup.+, Zn.sup.2+, Al.sup.3+, Fe.sup.2+, Fe.sup.3+,
 Co.sup.2+, Ni.sup.2+, Ti.sup.4+, and Zr.sup.4+. Of these cations,
 Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Fr.sup.+, Cu.sup.+ and
 Ag.sup.+ are preferred over the others.
 Examples of groups represented by R.sup.4 to R.sup.7 in the ammonium ion of
 formula (3) include the same groups as recited as examples of R.sup.1 to
 R.sup.3. The following are examples of an ammonium ion represented by
 formula (3):
 ##STR5##
 The repeating units constituting the polymer main chain, which are
 represented by P in formulae (1) and (2), can be selected from the
 following structural moieties:
 ##STR6##
 Specific examples of monomers having at least either carboxylic acid groups
 or carboxylate groups are shown below.
 ##STR7##
 ##STR8##
 ##STR9##
 The present polymer having at least either carboxylic acid groups or
 carboxylate groups may be a homopolymer constituted of the same repeating
 units of formula (1) or (2) or a copolymer constituted of two or more
 kinds of repeating units selected from those represented by formulae (1)
 and (2). Further, the present polymer may be a copolymer having different
 constitutional repeating units derived from other monomers.
 Examples of the other monomers usable in the invention include known
 monomers, such as acrylic acid esters, methacrylic acid esters,
 acrylamides, methacrylamides, vinyl esters, styrenes, acrylic acid,
 methacrylic acid, acrylonitrile, maleic anhydride and maleimide. By the
 use of such monomers as comonomers, various properties, including film
 formability, film strength, water wettability, hydrophobicity, solubility,
 reactivity and stability, can be improved.
 Examples of acrylic acid esters include methyl acrylate, ethyl acrylate,
 (n- or i-)propyl acrylate, (n-, i-, sec- or t-)butyl acrylate, amyl
 acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, chloroethyl acrylate,
 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypentyl
 acrylate, cyclohexyl acrylate, allyl acrylate, trimethylolpropane
 monoacrylate, pentaerythrithol monoacrylate, benzyl acrylate,
 methoxybenzyl acrylate, chlorobenzyl acrylate, hydroxybenzyl acrylate,
 hydroxyphenetyl acrylate, dihydroxyphenetyl acrylate, furfuryl acrylate,
 tetrahydrofurfuryl acrylate, phenyl acrylate, hydroxyphenyl acrylate,
 chlorophenyl acrylate, sulfamoylphenyl acrylate and
 2-(hydroxyphenylcarbonyloxy)ethyl acrylate.
 Examples of methacrylic acid esters include methyl methacrylate, ethyl
 methacrylate, (n- or i-)propyl methacrylate, (n-, i-, sec- or t-)butyl
 methacrylate, amyl methacrylate, 2-ethylhexylmethacrylate,
 dodecylmethacrylate, chloroethyl methacrylate, 2-hydroxyethylmethacrylate,
 2-hydroxypropyl methacrylate, 2-hydroxypentyl methacrylate, cyclohexyl
 methacrylate, allyl methacrylate, trimethylolpropane monomethacrylate,
 pentaerythritol monomethacrylate, benzyl methacrylate, methoxybenzyl
 methacrylate, chlorobenzyl methacrylate, hydroxybenzyl methacrylate,
 hydroxyphenetyl methacrylate, dihydroxyphenetyl methacrylate, furfuryl
 methacrylate, tetrahydrofurfuryl methacrylate, phenyl methacrylate,
 hydroxyphenyl methacrylate, chlorophenyl methacrylate, sulfamoylphenyl
 methacrylate and 2-(hydroxyphenylcarbonyloxy)ethyl methacrylate.
 Examples of acrylamides include acrylamide, N-methylacrylamide,
 N-ethylacrylamide, N-propylacrylamide, N-butylacrylamide,
 N-benzylacrylamide, N-hydroxyethyl-acrylamide, N-phenylacrylamide,
 N-tolylacrylamide, N-(hydroxyphenyl)acrylamide,
 N-(sulfamoylphenyl)acrylamide, N-(phenylsulfonyl)acrylamide,
 N-(tolylsulfonyl)acrylamide, N,N-dimethylacrylamide,
 N-methyl-N-phenylacrylamide and N-hydroxyethyl-N-methylacrylamide.
 Examples of methacrylamides include methacrylamide, N-methylmethacrylamide,
 N-ethylmethacrylamide, N-propylmethacrylamide, N-butylmethacrylamide,
 N-benzylmethacrylamide, N-hydroxyethylmethacrylamide,
 N-phenylmethacrylamide, N-tolylmethacrylamide,
 N-(hydroxyphenyl)-methacrylamide, N-(sulfamoylphenyl)methacrylamide,
 N-(phenylsulfonyl)methacrylamide, N-(tolylsulfonyl)methacrylamide,
 N,N-dimethylmethacrylamide, N-methyl-N-phenylmethacrylamide and
 N-hydroxyethyl-N-methylmethacrylamide.
 Examples of vinyl esters include vinyl acetate, vinyl butyrate and vinyl
 benzoate.
 Examples of styrenes include styrene, methylstyrene, dimethylstyrene,
 trimethylstyrene, ethyl styrene, propylstyrene, cyclohexylstyrene,
 chloromethylstyrene, trifluoromethylstyrene, ethoxymethylstyrene,
 acetoxymethylstyrene, methoxystyrene, dimethoxystyrene, chlorostyrene,
 dichlorostyrene, bromostyrene, iodostyrene, fluorostyrene and
 carboxystyrene.
 In synthesizing copolymers according to the invention, those monomers are
 used in their respective proportions sufficient for improvements in
 various physical properties. When other monomers are used in too large
 proportions, the function of the present monomer containing a carboxylic
 acid group or a carboxylate group becomes insufficient. Therefore, it is
 desirable that the total proportion of the other monomers be at most 80
 weight %, preferably at most 50 weight %.
 Examples of a polymer according to the invention, which has at least either
 carboxylic acid or carboxylate groups capable of causing thermal
 decarboxylation, are illustrated below:
 ##STR10##
 ##STR11##
 ##STR12##
 ##STR13##
 ##STR14##
 ##STR15##
 ##STR16##
 Synthesis Example
 Synthesis of Monomer (1)
 Into a 3-liter three-necked flask were charged 1,000 ml of water, 100 g of
 p-styrenesulfonyl chloride, 126 g of sodium sulfite, 106 g of sodium
 carbonate and hydroquinone in a catalytic amount. These components were
 then heated with stirring with the internal temperature being kept at
 45.degree. C. After 1 hour, 174 g of sodium chloroacetate and 12 g of
 potassium iodide were added to the mixture. The internal temperature was
 raised to 70.degree. C. where the mixture was then stirred for 5 hours.
 After reaction, the reaction mixture was allowed to cool to room
 temperature. Concentrated hydrochloric acid was then added dropwise to the
 reaction mixture over an ice bath until the pH value of the solution
 reached 1. As a result, precipitation of a solid matter was observed. The
 precipitate was filtered off, thoroughly washed with water, and then dried
 to obtain 95 g of a white powder. The product showed a purity of 99% as
 determined by HPLC.
 Synthesis of Monomers (2) to (4), (8) and (9)
 Monomers (2) to (4), (8) and (9) were prepared in the same manner as in the
 synthesis of Monomer (1) except that the corresponding p-styrenesulfonyl
 chloride and sodium chloroacetate were used, respectively. The purity of
 these monomers as determined by HPLC are listed below.

Monomer No. Purity
 (2) 98%
 (3) 97%
 (4) 97%
 (8) 99%
 (9) 98%
 Synthesis of Monomer (5)
 Into a 3-liter three-necked flask were charged 1,000 ml of water, 113 g of
 3-methacryloxypropylsulfonyl chloride, 126 g of sodium sulfite, 106 g of
 sodium carbonate and hydroquinone in a catalytic amount. These components
 were then heated with stirring with the internal temperature being kept at
 45.degree. C. After 1 hour, 174 g of sodium chloroacetate and 12 g of
 potassium iodide were added to the mixture. The internal temperature was
 raised to 70.degree. C. where the mixture was then stirred for 5 hours.
 After reaction, the reaction mixture was allowed to cool to room
 temperature. Concentrated hydrochloric acid was then added dropwise to the
 reaction mixture over an ice bath until the pH value of the solution
 reached 1. As a result, precipitation of a solid matter was observed. The
 precipitate was filtered off, thoroughly washed with water, and then dried
 to obtain 98 g of a white powder of Monomer (5). The product showed a
 purity of 98% as determined by HPLC.
 Synthesis of Monomer (6)
 Into a 2-liter three-necked flask were charged 1,600 ml of water, 250 g of
 N-acetylsulfanilyl chloride, 270 g of sodium sulfite and 227 g of sodium
 carbonate. These components were then heated with stirring with the
 internal temperature being kept at 45.degree. C. After 1 hour, 250 g of
 sodium chloroacetate and 27 g of potassium iodide were added to the
 mixture. The internal temperature was raised to 70.degree. C. where the
 mixture was then stirred for 5 hours. After reaction, the reaction mixture
 was allowed to cool to room temperature. Concentrated hydrochloric acid
 was then added dropwise to the reaction mixture over an ice bath until the
 pH value of the solution reached 1. As a result, precipitation of a solid
 matter was observed. The precipitate was filtered off, thoroughly washed
 with water, and then dried to obtain 250 g of N-acetylsulfanylacetic
 acid(white solid matter).
 Subsequently, into a 2-liter three-necked flask were charged 1,000 ml of
 water and 250 g of N-acetylsulfanylacetic acid thus obtained. To the
 mixture was then slowly added dropwise 105 of concentrated sulfuric acid.
 After the dropwise addition, the reaction mixture was heated with stirring
 under reflux for 4 hours. Thereafter, the reaction mixture was allowed to
 cool to room temperature where water was then removed therefrom. The
 residue was then thoroughly washed with acetonitrile to obtain 200 g of
 p-aminobenzensulfonyl acetosulfate (white solid matter).
 Subsequently, into a 3-liter three-necked flask were charged 1,500 ml of
 water and 200 g of p-aminobenzenesulfonyl acetosulfate thus obtained. 90 g
 of sodium hydroxide was then added to the reaction mixture over ice bath.
 Thereafter, to the reaction mixture was slowly added dropwise 200 g of
 methacrylic acid chloride. After the dropwise addition, the reaction
 mixture was stirred at room temperature for 5 hours. After reaction,
 concentrated hydrochloric acid was added dropwise to the reaction solution
 over an ice bath until the pH value of the reaction solution reached 1.
 The resulting precipitate was filtered off, and then thoroughly washed
 with water to obtain a white solid matter. The white solid matter thus
 obtained was then recrystallized from a mixture of methanol and water so
 that it was purified to obtain 210 g of Monomer (6) in the form of white
 solid matter (purity: 99% as determined by HPLC).
 Synthesis of Monomers (10) to (13)
 Monomers (10) to (13) were prepared in the same manner as in the synthesis
 of Monomer (6) except that the corresponding N-acetylsulfamyl chloride and
 sodium chloroacetate were used, respectively. The purity of these monomers
 as determined by HPLC are listed below.

Monomer No. Purity
 (10) 99%
 (11) 99%
 (12) 99%
 (13) 98%
 Synthesis of Monomer (7)
 Into a 500 ml three-necked flask were charged 60 ml of water, 120 ml of
 methanol and 75 g of sodium hydroxide. 75 g of 4-aminothiphenol and 85 g
 of sodium chloroacetate were then slowly added to the mixture over an ice
 bath. Thereafter, the reaction mixture was allowed to cool to room
 temperature where it was then stirred for 6 hours. After reaction,
 concentrated hydrochloric acid was added dropwise to the reaction mixture
 over an ice bath until the pH value of the solution reached 1. As a
 result, precipitation of a solid matter was observed. The precipitate was
 filtered off, thoroughly washed with water, and then dried to obtain 95 g
 of 4-aminophenylsulfanylacetic acid (white powder).
 Subsequently, into a 1-liter three-necked flask were charged 820 ml of
 water and 95 g of N-aminophenylsulfanylacetic acid thus obtained. To the
 mixture were then slowly added dropwise 62 g of sodium hydroxide and 93 g
 of methacryloyl chloride over an ice bath. Thereafter, the reaction
 mixture was allowed to cool to room temperature where it was then stirred
 for 6 hours. After reaction, concentrated hydrochloric acid was added
 dropwise to the reaction mixture until the pH value of the solution
 reached 1. As a result, precipitation of a solid matter was observed. The
 resulting precipitate was filtered off, and then thoroughly washed with
 water to obtain a white solid matter. The white solid matter thus obtained
 was then recrystallized from a mixture of ethanol and water so that it was
 purified to obtain 98 g of Monomer (7) in the form of white solid matter
 (purity: 99% as determined by HPLC).
 Synthesis of Monomers (14) to (18)
 Monomers (14) to (18) were prepared in the same manner as in the synthesis
 of Monomer (7) except that the corresponding sodium chloroacetate was
 used, respectively. The purity of these monomers as determined by HPLC are
 listed below.

Monomer No. Purity
 (14) 99%
 (15) 98%
 (16) 99%
 (17) 98%
 (18) 97%
 Synthesis of Monomer (19)
 Into a 1-liter three-necked flask were charged 50 g of
 4-nitro-phenylaminoacetic acid and 600 ml of 2-propanol. To the mixture
 were then added 71 g of reduced iron and an aqueous solution of ammonium
 chloride obtained by dissolving 15.2 g of ammonium chloride in 60 ml of
 water. The reaction mixture was allowed to undergo reaction at a
 temperature of 90.degree. C. for 5 hours, extracted with dichloromethane,
 and then subjected to silica gel chromatography to obtain 29 g of
 4-amino-phenylaminoacetic acid.
 Subsequently, into a 500 ml three-necked flask were charged 250 ml of water
 and 29 g of 4-amino-phenylaminoacetic acid thus obtained. To the mixture
 were then slowly added dropwise 15 g of sodium hydroxide and 35 g of
 methacryloyl chloride over ice bath. Thereafter, the reaction mixture was
 allowed to cool to room temperature where it was then stirred for 6 hours.
 After reaction, concentrated hydrochloric acid was added dropwise to the
 reaction mixture until the pH value of the solution reached 1. As a
 result, precipitation of a solid matter was observed. The resulting
 precipitate was filtered off, and then thoroughly washed with water to
 obtain a white solid matter. The white solid matter thus obtained was then
 recrystallized from a mixture of ethanol and water so that it was purified
 to obtain 31 g of Monomer (19) in the form of white solid matter (purity:
 99% as determined by HPLC).
 Synthesis of Monomers (20) to (24)
 Monomers (20) to (24) were prepared in the same manner as in the synthesis
 of Monomer (19) except that the corresponding 4-nitro-phenylaminoacetic
 acid was used, respectively. The purity of these monomers as determined by
 HPLC are listed below.

Monomer No. Purity
 (20) 98%
 (21) 98%
 (22) 99%
 (23) 98%
 (24) 99%
 Synthesis of Polymer (P-6)
 Into a 200 ml three-necked flask were charged 20 g of Monomer (6) and 40 g
 of dimethylacetamide. To the mixture was then added 0.2 g of
 2,2'-azobis(2,4-dimethylvaleronitrile) at a temperature of 65.degree. C.
 in a stream of nitrogen. The reaction mixture was then stirred at the same
 temperature for 6 hours. Thereafter, the reaction mixture was allowed to
 cool to room temperature where it was then subjected to reprecipitation in
 1 liter of water to obtain a polymer solid. The polymer was found to have
 a weight-average molecular weight of 12,000 as determined by GPC.
 Synthesis of Polymers (P-1) to (P-5), and (P-7) to (P-24)
 Polymers (P-1) to (P-5) and (P-7) to (P-24) were prepared in the same
 manner as in the synthesis of Polymer (P-6) except that Monomer (6) was
 replaced by the monomers set forth in Table 1, respectively. The
 weight-average molecular weight of Polymers (P-1) to (P-5) and (P-7) to
 (P-24) thus prepared are set forth in Table 1.
 TABLE 1
 Weight-average
 molecular weight (.times.
 Monomer structure Polymer structure 10,000)
 1 P-1 1.04
 2 P-2 1.11
 3 P-3 1.23
 4 P-4 1.59
 5 P-5 1.42
 7 P-7 0.89
 8 P-8 1.11
 9 P-9 1.65
 10 P-10 1.47
 11 P-11 1.58
 12 P-12 1.00
 13 P-13 1.02
 14 P-14 1.05
 15 P-15 1.33
 16 P-16 1.41
 17 P-17 1.23
 18 P-18 1.00
 19 P-19 1.02
 20 P-20 0.89
 21 P-21 0.99
 22 P-22 0.85
 23 P-23 1.25
 24 P-24 1.12
 Synthesis of Polymer (P-25)
 To a mixture of 10 g of Polymer (P-1) and 44 ml of methanol was slowly
 added dropwise 8.5 g of sodium methoxide (28% methanol solution) over ice
 bath. The reaction mixture was then stirred for 5 minutes. The resulting
 solid matter was filtered off, and then dried to obtain 9.1 g of Polymer
 (P-25).
 Synthesis of Polymers (P-26) to (P-42)
 Polymers (P-26) to (P-42) were prepared in the same manner as in synthesis
 of Polymer (P-25) except that Polymer (P-1) and sodium methoxide were
 replaced by the polymers and bases in Table 2 below.
 TABLE 2
 Polymer
 Synthetic used in
 polymer synthesis Base
 P-26 P-2 Potassium methoxide
 P-27 P-1 Tetramethylammonium hydroxide
 P-28 P-1 Tetrabutylammonium hydroxide
 P-29 P-5 Sodium methoxide
 P-30 P-5 Tetramethylammonium hydroxide
 P-31 P-6 Sodium methoxide
 P-32 P-6 Potassium methoxide
 P-33 P-6 Tetramethylammonium hydroxide
 P-34 P-6 Tetraethylammonium hydroxide
 P-35 P-6 Tetraphenylammonium hydroxide
 P-36 P-7 Sodium methoxide
 P-37 P-15 Potassium methoxide
 P-38 P-16 Tetramethylammonium hydroxide
 P-39 P-17 Tetraethylammonium hydroxide
 P-40 P-18 Tetrabutylammonium hydroxide
 P-41 P-19 Tetraphenylammonium hydroxide
 P-42 P-20 Sodium methoxide
 Synthesis of Polymer (P-43)
 Into a 200 ml three-necked flask were charged 20 g of Monomer (1), 2.6 g of
 2-hydroxyethyl acrylate and 45.2 g of water. To the mixture was then added
 0.33 g of 2,2'-azobis(2,4-dimethylvaleronitrile) at a temperature of
 65.degree. C. in a stream of nitrogen. The reaction mixture was then
 stirred at the same temperature for 6 hours. Thereafter, the reaction
 mixture was allowed to cool to room temperature where it was then
 subjected to reprecipitation in 1 liter of water to obtain a polymer
 solid. The polymer was found to have a weight-average molecular weight of
 13,700 as determined by GPC.
 Synthesis of Polymers (P-44) to (P-49)
 Polymers (P-44) to (P-49) were prepared in the same manner as in the
 synthesis of Polymer (P-43) except that the monomers set forth in Table 3
 below were used, respectively. The weight-average molecular weight of
 Polymers (P-44) to (P-49) prepared are set forth in Table 3 below.
 TABLE 3
 Weight-
 average
 Monomer Polymer molecular
 No. Monomer structure weight
 1 Methyl acrylate P-44 1.10
 5 2-Hydroxyethyl P-45 1.04
 methacrylate
 5 Ethyl acrylate P-46 0.98
 6 2-Hydroxyethyl P-47 1.54
 methacrylate
 6 Methyl methacrylate P-48 1.11
 6 Ethyl methacrylate P-49 1.25
 Synthesis of Polymers (P-50) to (P-57)
 Polymers (P-50) to (P-57) were prepared in the same manner as in the
 synthesis of Polymer (P-25) except that Polymer (P-1) and sodium methoxide
 were replaced by the polymers and bases set forth in Table 4 below.
 TABLE 4
 Polymer
 Synthetic used in
 polymer synthesis Base
 P-50 P-43 Sodium methoxide
 P-51 P-44 Tetramethylammonium hydroxide
 P-52 P-47 Sodium methoxide
 P-53 P-47 Tetramethylammonium hydroxide
 P-54 P-48 Sodium methoxide
 P-55 P-48 Tetramethylammonium hydroxide
 P-56 P-49 Sodium methoxide
 P-57 P-49 Tetramethylammonium hydroxide
 The photothermal converter usable in the invention has no particular
 restriction as far as it can absorb radiation of light energy used for
 recording. In making a printing plate by the use of infrared laser, which
 is a preferred mode for carrying out the invention, it is desirable to use
 an infrared absorber as the photothermal converter. Suitable examples of
 an infrared absorber are illustrated below:
 [Infrared Absorber]
 In applying the lithographic printing plate of the present invention to the
 image formation by infrared irradiation (heat mode exposure) as a
 lithographic printing plate precursor, an infrared absorber is
 incorporated into a recording layer of the lithographic printing plate.
 The infrared absorbers used to advantage in the invention are dyes or
 pigments effectively absorbing infrared rays of wavelengths ranging from
 760 nm to 1,200 nm. In particular, the dyes and pigments having their
 absorption maxima in the wavelength range of 760 to 1,200 nm are
 preferable.
 As these dyes, commercially available dyes and dyes known in literature
 (e.g., Senryo Binran (which means "Handbook of Dyes"), compiled by Yuki
 Gousei Kagaku Kyokai, published in 1970) can be employed. Examples thereof
 include azo dyes, metal complex azo dyes, pyrazolone azo dyes,
 anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine
 dyes, methine dyes, cyanine dyes and metal thiolate complexes.
 More specifically, the cyanine dyes disclosed in, e.g., JP-A-58-125246,
 JP-A-59-84356, JP-A-59-202829 and JP-A-60-78787, the methine dyes
 disclosed in, e.g., JP-A-58-173696, JP-A-58-181690 and JP-A-58-194595, the
 naphthoquinone dyes disclosed in, e.g., JP-A-58-112793, JP-A-58-224793,
 JP-A-59-48187, JP-A-59-73996, JP-A-60-52940 and JP-A-60-63744, the
 squarylium dyes disclosed in, e.g., JP-A-58-112792 and the cyanine dyes
 disclosed in British Patent 434,875 can be used as desirable dyes.
 Further, the use of the near infrared absorption sensitizers disclosed in
 U.S. Pat. No. 5,156,938 is also well suited. In addition, the substituted
 arylbenzo(thio)-pyrylium salts disclosed in U.S. Pat. No. 3,881,924, the
 trimethinethiapyrylium salts disclosed in JP-A-57-142645 (U.S. Pat. No.
 4,327,169), the pyrylium compounds disclosed in JP-A-58-181051,
 JP-A-58-220143, JP-A-59-41363, JP-A-59-84248, JP-A-59-84249,
 JP-A-59-146063 and JP-A-59-146061, the cyanine dyes disclosed in
 JP-A-59-216146, the pentamethinethio-pyrylium salts disclosed in U.S. Pat.
 No. 4,283,475, and the pyrylium compounds disclosed in JP-B-5-13514 and
 JP-B-5-19702 (the term "JP-B" as used herein means an "examined Japanese
 patent publication") can also be used to advantage.
 As another suitable examples of dyes, mention may be made of the near
 infrared absorbing dyes defined as formulae (I) and (II) in U.S. Pat. No.
 4,756,993.
 Of those dyes, the cyanine dyes, the squarylium dyes, the pyrylium dyes and
 the nickel thiolate complexes are preferred in particular.
 As examples of pigments usable in the invention, mention may be made of
 commercially available pigments and the pigments described in Colour Index
 (C.I.) Handbook, Saishin Ganryo Binran (which means "Newest Handbook of
 Pigments"), compiled by Nippon Ganryo Gijutu Kyokai, published in 1977,
 Saishin Ganryo Ohyo Gijutu (which means "Newest Application Arts of
 Pigments"), published by CMC Shuppan in 1986, and Insatu Ink Gijutu (which
 means "Techniques for Printing Ink"), published by CMC Shuppan in 1984.
 As to the type of pigment, black pigments, yellow pigments, orange
 pigments, brown pigments, red pigments, violet pigments, blue pigments,
 green pigments, fluorescent pigments, metallic powder pigments and
 polymer-bonded dyes are examples thereof. Specifically, the usable
 pigments include insoluble azo pigments, azo lake pigments, condensed azo
 pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone
 pigments, perylene and perynone 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 and carbon black. Of these pigments, carbon black is
 preferred over the others.
 These pigments may be used without surface treatment, but they may be used
 after undergoing surface treatment. Examples of a surface treatment method
 include the method of coating resin or wax on the pigment surface, the
 method of making a surfactant adhere to the pigment surface, and the
 method of making a reactive substance (e.g., a silane coupling agent, an
 epoxy compound, polyisocyanate) fuse with the pigment surface. These
 surface treatment methods are described in Kinzoku Sekken no Seishitu to
 Ohyo (which means "Properties of Metallic Soap and Application thereof"),
 published by Sachi Shobo, Insatu Ink Gijutu (which means "Techniques for
 Printing Ink"), published by CMC Shuppan in 1984, and Saishin Ganryo Ohyo
 Gijutu (which means "Newest Application Arts of Pigments"), published by
 CMC Shuppan in 1986.
 For the grain size, it is desirable to be in the range of 0.01 to 10 .mu.m,
 preferably 0.05 to 1 .mu.m, particularly preferably 0.1 to 1 .mu.m. When
 the grain size of a pigment is smaller than 0.01 .mu.m, the resulting
 pigment dispersion is undesirable from the viewpoint of the stability in
 the coating solution of a photosensitive composition; while, when the
 pigment grain size is greater than 10 .mu.m, the image recording layer
 formed by coating is inferior in uniformity.
 In dispersing pigment grains, conventional dispersing techniques used for
 ink production or toner production can be adopted. Examples of a
 dispersing machine usable therein include an ultrasonic disperser, a sand
 mill, an attriter, a pearl mill, a super mill, a ball mill, an impeller, a
 disperser, a KD mill, a colloid mill, a Dynatron, a three-rod roll mill
 and a pressurized kneader. Details thereof are described in Saishin Ganryo
 Ohyo Gijutu (which means "Newest Application Arts of Pigments"), published
 by CMC Shuppan in 1986.
 Those dyes and pigments are incorporated in a proportion of 0.01 to 50
 weight %, preferably 0.1 to 10 weight %, particularly preferably 0.5 to 10
 weight % in the case of dyes and 1.0 to 10 weight % in the case of
 pigments, to the total solids in the composition for forming the recording
 layer of a lithographic printing plate. When the proportion of dye(s) or
 pigment(s) incorporated is lower than 0.01 weight %, the sensitivity
 becomes low; while, when it is increased beyond 50 weight %, scum tends to
 develop in the non-imaging area upon printing.
 To the recording layer of the present lithographic printing plate, the
 nonionic surfactants as disclosed in JP-A-62-251740 and JP-A-3-208514 and
 the amphoteric surfactants as disclosed in JP-A-59-121044 and JP-A-4-13149
 can be added for the purpose of improving the stability to variation of
 printing conditions.
 Examples of a nonionic surfactant include sorbitan tristearate, sorbitan
 monopalmitate, sorbitan trioleate, stearic acid monoglyceride and
 polyoxyethylene nonyl phenyl ether.
 Examples of an amphoteric surfactant include alkyldi(aminoethyl)glycines,
 alkylpolyaminoethylglycine hydrochlorides,
 2-alkyl-N-carboxyethyl-N-hydroxyethyl-imidazolium betaines and
 N-tetradecyl-N,N-betaine (e.g., Amorgen K, trade name, produced by Daiichi
 Seiyaku Co., Ltd.)
 The proportion of such nonionic and amphoteric surfactants in the total
 solids of the image forming material is from 0.05 to 15 weight %,
 preferably from 0.1 to 5 weight %.
 To the recording layer of the present lithographic printing plate, if
 needed, plasticizers can further be added for conferring pliability on the
 coated layer. Examples of a plasticizer usable for such a purpose include
 polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl
 phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate,
 tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate, and
 acrylic or methacrylic acid oligomer and polymer.
 The recording layer of the present lithographic printing plate can be
 generally formed by dissolving the foregoing ingredients in a solvent and
 coating the solution on an appropriate support. Examples of a solvent
 usable therein include ethylene dichloride, cyclohexanone, methyl ethyl
 ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether,
 1-methoxy-2-propanol, 2-methoxyethylacetate, 1-methoxy-2-propylacetate,
 dimethoxyethane, methyl lactate, ethyl lactate, N,N-dimethylacetamide,
 N,N-dimethylformamide, tetramethyl-urea, N-methylpyrrolidone, dimethyl
 sulfoxide, sulfolane, .gamma.-butyrolactone, toluene and water. However,
 these examples should not be construed as limiting the scope of the
 invention.
 The above-described solvents are used singly or in admixture thereof. The
 concentration of the above-described ingredients (total solids content
 including additives) in the solvent is preferably from 1 to 50% by weight.
 The coating amount (solids content) coated on the support obtained after
 coating or drying is preferably from 0.5 to 5.0 g/m.sup.2. As the coating
 method, various coating methods such as bar coating, rotary coating, spray
 coating, curtain coating, dip coating, air knife coating, blade coating,
 and roll coating, etc.
 In the recording layer of the present lithographic printing plate, a
 surfactant for improving coating property, for example a fluorinated
 surfactant as disclosed in JP-A-62-170950, may be used. The amount added
 is preferably from 0.01 to 1% by weight, more preferably from 0.05 to 0.5%
 by weight, based on the total solids content in the photosensitive layer
 of the photosensitive lithographic printing plate.
 The support (substrate) which is coated with the present image forming
 material (recording layer) to provide a lithographic printing plate
 precursor is a dimensionally stable sheet-form material, including all
 materials which have hitherto been used as support for printing plate.
 Suitable examples of such a material include paper, paper laminated with
 plastic (e.g., polyethylene, polypropylene, polystyrene), a metal sheet
 such as a sheet of aluminum (including aluminum alloys), zinc, iron or
 copper, a plastic film such as a film of cellulose diacetate, cellulose
 triacetate, cellulose propionate, cellulose butyrate, cellulose
 acetobutyrate, cellulose nitrate, polyethylene terephthalate,
 polyethylene, polystyrene, polypropylene, polycarbonate or polyvinyl
 acetal, and paper or a plastic film on which the metal as recited above is
 laminated or deposited. Of these materials, the aluminum sheets, including
 aluminum alloy sheets as well as a pure aluminum sheet, are preferred over
 the others. As to the aluminum alloys, various alloys of aluminum and
 other metals, such as silicon, copper, manganese, magnesium, chromium,
 zinc, lead, bismuth and nickel, can be employed. In these compositions,
 some quantities of iron and titanium or negligible quantities of other
 impurities are further contained.
 The support is subjected to a surface treatment, e.g., a treatment for
 conferring water wettability on the support surface, if needed.
 When the support has a metal surface, especially an aluminum surface, it is
 desirable for the support to undergo a surface treatment, such as a
 graining treatment, an immersion treatment in an aqueous solution of
 sodium silicate, potassium fluorozirconate or phosphate, or an anodic
 oxidation treatment. Further, it is also favorable to use the aluminum
 sheet subjected to a graining treatment and then to an immersion treatment
 in an aqueous solution of sodium silicate, as disclosed in U.S. Pat. No.
 2,714,066, or the aluminum sheet subjected to an anodic oxidation
 treatment and then to an immersion treatment in an aqueous solution of
 alkali metal silicate, as disclosed in U.S. Pat. No. 3,181,461. The anodic
 oxidation treatment can be effected by sinking an aluminum sheet as anode
 into an electrolyte and passing current therethrough. As to the
 electrolyte, aqueous or non-aqueous solutions of inorganic acids, such as
 phosphoric acid, chromic acid, sulfuric acid and boric acid, organic
 acids, such as oxalic acid and sulfaminic acid, or salts thereof can be
 used alone or as combination of two or more thereof.
 In addition, as disclosed in U.S. Pat. No. 3,658,682, it is also effective
 to carry out the electrodeposition of silicate.
 Besides rendering the support surface wettable with water, those
 water-wettability providing treatments are performed for prevention of a
 harmful reaction between support surface and the recording layer and
 elevation of adhesiveness to the recording layer.
 Prior to the graining treatment, the aluminum sheet may undergo
 pre-treatments for removing the rolling oil from the sheet surface and
 making the sheet surface clean, if desired. For the former pre-treatment,
 a solvent, such as trichlene, and a surfactant are used; while, for the
 latter pre-treatment, the use of an alkali etching agent, such as sodium
 hydroxide or potassium hydroxide, is prevailing.
 In graining the metal surface, any of mechanical, chemical and
 electrochemical methods can be adopted effectively. Examples of a
 mechanical graining method include a ball abrasion method, a blast
 abrasion method and a brush abrasion method wherein the slurry as aqueous
 dispersion of abrasive, such as pumice, is rubbed with a nylon brush. As
 to the chemical graining method, the method of immersing in a saturated
 water solution of aluminum salt of mineral acid is advantageous. As an
 electrochemical graining method, the method of performing AC electrolysis
 in an acidic electrolyte, such as hydrochloric acid, nitric acid or a
 mixture thereof, is favorably adopted. Of those surface roughening
 methods, the combined use of mechanical and electrochemical roughening
 methods as disclosed in JP-A-55-137993 is preferable, because it can
 ensure strong adhesiveness of the support to ink-receptive images.
 It is desirable that the graining treatment according to any of the
 above-cited methods be performed so that the aluminum sheet surface has a
 center line average roughness (Ra) in the range of 0.3 to 1.0 .mu.m.
 The thus grained aluminum sheet is washed and chemically etched, if needed.
 The etching treatment solution is generally selected from aqueous solutions
 of bases or acids capable of dissolving aluminum. For this treatment,
 however, it is necessary that no film, excepting an aluminum film, be
 formed from the etching component on the etched surface. As examples of a
 suitable base for etching agent, mention may be made of sodium hydroxide,
 potassium hydroxide, trisodium phosphate, disodium phosphate, tripotassium
 phosphate and dipotassium phosphate. As examples of a suitable acid as
 etching agent, mention may be made of sulfuric acid, persulfuric acid,
 phosphoric acid, hydrochloric acid and salts thereof. On the other hand,
 the salts of metals having weaker tendency to ionization than aluminum,
 e.g., the salts of zinc, chromium, cobalt, nickel and copper, are
 unsuitable for etching component, because they form an unnecessary film on
 the etched surface.
 In performing the etching treatment, it is most desirable to control the
 etching agent concentration and the etching temperature so that the
 dissolution rate of the aluminum or alloy used is from 0.3 to 40 g/m.sup.2
 per minute of immersion time. However, the dissolution rates above or
 below the foregoing limits may be all right.
 The etching treatment is carried out by immersing an aluminum sheet in an
 etching solution or applying an etching solution to an aluminum sheet.
 Therein, it is desirable that the amount etched be controlled to the range
 of 0.5 to 10 g/m.sup.2.
 As to the etching agent, aqueous solutions of bases are preferred because
 of their high etching speeds. However, these solutions generate smut, so
 that a desmutting treatment is usually carried out. For the desmutting
 treatment, acids such as nitric acid, sulfuric acid, phosphoric acid,
 chromic acid, hydrogen fluoride and hydrogen borofluoride can be employed.
 The etched aluminum sheet is subjected to washing and anodic oxidation
 treatments, if needed. The anodic oxidation can be effected by
 conventional methods. Specifically, DC or AC current is sent into an
 aluminum sheet immersed in an aqueous or non-aqueous solution of sulfuric
 acid, phosphoric acid, chromic acid, oxalic acid, sulfaminic acid,
 benzenesulfonic acid or a mixture of two or more thereof, and thereby a
 film is formed anodically on the aluminum sheet surface.
 The conditions for anodic oxidation treatment change variously depending on
 the electrolyte used, so they cannot be generalized. However, by the
 normal standards of anodic oxidation, it would be appropriate that the
 electrolyte concentration be from 1 to 30 weight %, the electrolyte
 temperature be from 5 to 70.degree. C., the current density be from 0.5 to
 60 ampere/dm.sup.2, the voltage be from 1 to 100 V and the electrolysis
 time be 30 seconds to 50 minutes.
 Of those anodic oxidation treatments, the method of performing anodic
 oxidation in sulfuric acid under a high current density, which is
 disclosed in U.K. Patent 1,412,768, and the method of using phosphoric
 acid as an electrolytic bath for anodic oxidation, which is disclosed in
 U.S. Pat. No. 3,511,661, are preferred over the others.
 The surface-roughened and anodically oxidized aluminum sheet may be
 subjected to water-wettablity providing treatment, if desired. In a
 suitable method for such a treatment, the alkali metal silicates, such as
 sodium silicate, disclosed in U.S. Pat. Nos. 2,714,066 and 3,181,461, the
 potassium fluorozirconate disclosed in JP-A-36-22063 or the polyvinyl
 phosphonate disclosed in U.S. Pat. No. 4,153,461 is used as treatment
 agent.
 In making the present lithographic printing plate, it is desirable to
 provide an organic subbing layer before coating the recording layer from
 the viewpoint of lessening the residue in the non-imaging area of
 photosensitive layer. The organic compounds used for the organic subbing
 layer can be selected from, e.g., carboxymethyl cellulose, dextrin, gum
 arabic, amino group-containing phosphonic acids such as
 2-aminoethylphosphonic acid, organic phosphonic acids which may be
 substituted, such as phenylphosphonic acid, naphthylphosphonic acid,
 alkyl-phosphonic acids, glycerophosphonic acid, methylene-diphosphonic
 acid and ethylenediphosphonic acid, organic phosphoric acids which may be
 substituted, such as phenylphosphoric acid, naphthylphosphoric acid,
 alkyl-phosphoric acids and glycerophosphoric acid, organic phosphinic
 acids which may be substituted, such as phenylphosphinic acid,
 naphthyl-phosphinic acid, alkyl-phosphinic acids and glycerophosphinic
 acid, amino acids, such as glycine and .beta.-alanine, or hydroxyl
 group-containing amine hydrochlorides such as ethanolamine hydrochloride.
 These compounds may be used alone or as a mixture of two or more thereof.
 Besides the compounds recited above, high molecular compounds having
 poly(p-vinylbenzoate) as constitutional repeating units can be used.
 Such an organic subbing layer can be provided in the manners described
 below: In one manner, the organic compound is dissolved in water, an
 organic solvent, such as methanol, ethanol or methyl ethyl ketone, or a
 mixture thereof, coated on the aluminum sheet, and then dried; and, in
 another manner, the aluminum sheet is immersed into a solution of organic
 compound in water, an organic solvent, such as methanol, ethanol or methyl
 ethyl ketone, or a mixture thereof, thereby adsorbing the organic compound
 onto the aluminum sheet, and then washed with, e.g., water, followed by
 drying. More specifically, the organic compound solution used in the
 former manner ranges in concentration from 0.005 to 10 weight %, and it
 may be coated using any of conventional methods, including a bar coater
 method, a spin coating method, a spray coating method or a curtain coating
 method may be used. On the other hand, the solution concentration suitable
 for the latter manner is from 0.01 to 20 weight %, preferably from 0.05 to
 5 weight %, the immersion temperature is from 20 to 90.degree. C.,
 preferably from 25 to 50.degree. and the immersion time is from 0.1 second
 to 20 minutes, preferably from 2 seconds to 1 minutes.
 The solution used therein can be adjusted to the pH range of 1-12 by the
 use of a basic substance such as ammonia, triethylamine or potassium
 hydroxide, or an acidic substance such as hydrochloric acid or phosphoric
 acid. In addition, yellow dyes can further be added to the solution with
 the intention of improving the tone reproduction of the lithographic
 printing plate precursor.
 The suitable dry coverage of the organic subbing layer is from 2 to 200
 mg/m.sup.2, preferably from 5 to 100 mg/m.sup.2. The dry coverage smaller
 than 2 mg/m.sup.2 cannot ensure sufficient press life for the lithographic
 printing plate. In addition, one cannot ensure a dry coverage greater than
 200 mg/m.sup.2.
 On the back of the support, a backcoat is provided, if needed. Examples of
 a coating material suitable for the backcoat include the organic high
 molecular compounds disclosed in JP-A-5-45885 and the metal oxides
 produced by hydrolysis or polycondensation of organic or inorganic metal
 compounds disclosed in JP-A-6-35174.
 In particular, the metal oxides prepared from alkoxy compounds of silicon,
 such as Si(OCH.sub.3).sub.4, Si(OC.sub.2 H.sub.5).sub.4, Si(OC.sub.3
 H.sub.7).sub.4 and Si(OC.sub.4 H.sub.9).sub.4, are preferred over the
 others because these compounds are available at low prices and ensure high
 water wettability in the coatings thereof.
 In accordance with the embodiments mentioned above, the lithographic
 printing plate precursors of the present invention can be prepared. Each
 lithographic printing plate is subjected directly to imagewise
 heat-sensitive recording by means of, e.g., a heat recording (thermal)
 head, or undergoes imagewise exposure by means of a solid or semiconductor
 laser device emitting infrared rays of wavelengths ranging from 760 to
 1,200 nm. After heat-sensitive recording or irradiation with laser beams,
 the plate is subjected to development with water and, if desired, to
 gumming, and then loaded in a press, followed by printing operations. In
 another way, the plate is loaded in a press just after heat-sensitive
 recording or irradiation with laser beams, and undergoes printing
 operations. In both ways, however, it is desirable that the heating
 treatment be carried out after heat-sensitive recording or irradiation
 with laser beams. As to the conditions appropriate for heat treatment, the
 treatment time is from 10 seconds to 5 minutes under the temperature of
 80-150.degree. C. By this heat treatment, the heat or laser energy
 required for heat-sensitive or laser-irradiation recording respectively
 can be reduced.
 The lithographic printing plate which has received such a heat treatment is
 loaded in an offset press or the like after water development or as it is,
 and undergoes printing operations to provide a great number of prints.
 Additionally, in the case of performing heat-sensitive recording on the
 present lithographic printing plate precursor by means of a thermal head
 or the like, the infrared absorbers as recited above may not be
 incorporated in the recording layer.
 The thermal head usable therein has no particular restriction. For
 instance, simple and compact thermal printers for word processor use and
 thermal facsimile are applicable.

The present invention will be further described in the following examples,
 but the present invention should not be construed as being limited
 thereto. (Preparation of support)
 A 0.30 mm-thick aluminum plate (quality grade: 1050) was degreased by
 cleaning with trichloroethylene, grained on the surface thereof using a
 nylon brush and a 400-mesh pumice stone-water suspension, and washed
 thoroughly with water. This plate was etched by 9-second dipping in a 25%
 aqueous solution of sodium hydroxide kept to 45.degree. C., washed with
 water, immersed for 20 seconds in 2% HNO.sub.3, and further washed with
 water. Therein, the etched amount at the grained surface was about 3
 g/m.sup.2. Further, this aluminum plate was immersed in 7% H.sub.2
 SO.sub.4 as electrolyte and anodically oxidized with DC current density of
 15 A/dm.sup.2 to form an anodic oxidation film of 3 g/m.sup.2. The thus
 treated aluminum sheet was washed with water and dried.
 EXAMPLES 1 TO 5
 Five kinds of solutions, (A-1) to (A-5), were prepared so as to have the
 following Composition (A), wherein the present polymer having carboxylic
 acid or carboxylate groups was changed as shown in Table 5. These
 solutions were each applied to the aluminum sheet prepared above, and
 dried for 2 minutes at 100.degree. C. Thus, lithographic printing plate
 precursors, (A-1) to (A-5), were prepared. The weight of each plate after
 drying was 1.1 g/m.sup.2.

Composition (A)
 Polymer having carboxylic acid 1.0 g
 groups (Table 5)
 Infrared absorber NK-3508 (made by 0.15 g
 Nippon Kanko Shikiso Kenkyujo K.K.)
 Megafac F-177 (fluorine-containing 0.06 g
 surfactant, made by Dainippon Ink
 and Chemicals Inc.)
 Methyl ethyl ketone 20 g
 Methyl alcohol 7 g
 The lithographic printing plate precursors (A-1) to (A-5) thus obtained
 were each exposed by means of a semiconductor laser device emitting the
 infrared beam of 830 nm, and loaded in a Hidel KOR-D printing machine
 without undergoing development. The fountain solution used therein will be
 described below.
 Fountain solution: pH 8.8 (H.sub.2 O: 84.7%; IPA: 10%; Triethylamine: 5%,;
 Concentrated hydrochloric acid: 0.3%)
 After printing, the image areas of prints were evaluated as to whether or
 not they had sufficient inking. The inking quality during the printing
 operations was examined at the stages of obtaining 1,000 sheets of prints
 and 20,000 sheets of prints respectively. The results obtained are shown
 in Table 5. In every case, prints of good inking quality were obtained.
 Comparative Examples 1
 A lithographic printing plate precursor (C-1) was prepared in the same
 manner as in Examples 1 to 5, except that the present polymer having
 carboxylic acid or carboxylate groups was replaced by polyacrylic acid.
 This plate underwent plate-making processing and printing operations under
 the same conditions as in Examples 1 to 5. The results obtained are also
 shown in Table 5. No prints were obtained because bad inking of the
 imaging area.
 EXAMPLES 6 TO 10
 Five kinds of solutions, (B-1) to (B-5), were prepared so as to have the
 following Composition (B), wherein the present polymer having carboxylic
 acid or carboxylate groups was changed as shown in Table 5. These
 solutions were each applied to the aluminum sheet prepared above, and
 dried for 2 minutes at 100.degree. C. Thus, lithographic printing plate
 precursors, (B-1) to (B-5), were prepared. The weight of each plate after
 drying was 1.1 g/m.sup.2.

Composition (B)
 Polymer having carboxylic acid 1.0 g
 groups (Table 5)
 Himicron K Black (made by Mikuni Color 0.30 g
 Ltd.)
 Water 18 g
 Acetonitrile 9 g
 The lithographic printing plate precursors (B-1) to (B-5) thus obtained
 were each exposed by means of a semiconductor laser device emitting the
 infrared beam of 830 nm, and loaded in a Hidel KOR-D printing machine
 without undergoing development. As the fountain solution therein there was
 used tap water.
 After printing, the image areas of prints were evaluated as to whether or
 not they had sufficient inking. The inking quality during the printing
 operations was examined at the stages of obtaining 1,000 sheets of prints
 and 20,000 sheets of prints respectively. The results obtained are shown
 in Table 5. In every case, prints of good inking quality were obtained.
 Comparative Example 2
 A lithographic printing plate precursor (C-2) was prepared in the same
 manner as in Examples 6 to 10, except that the present polymer having
 carboxylic acid or carboxylate groups was replaced by sodium polyacrylate.
 This plate underwent plate-making processing and printing operations under
 the same conditions as in Examples 6 to 10. The results obtained are also
 shown in Table 5. No prints were obtained because bad inking of the
 imaging area.
 TABLE 5
 Polymer
 having
 Lithographic carboxylic
 printing acid or Inking of imaging area upon
 plate carboxylate printing
 precursor groups 1000th print 20000th print
 Example 1 (A-1) P-1 good good
 Example 2 (A-2) P-6 good good
 Example 3 (A-3) P-7 good good
 Example 4 (A-4) P-47 good good
 Example 5 (A-5) P-48 good good
 Example 6 (B-1) P-25 good good
 Example 7 (B-2) P-31 good good
 Example 8 (B-3) P-33 good good
 Example 9 (B-4) P-35 good good
 Example 10 (B-5) P-52 good good
 Comparative (C-1) Polyacrylic No prints No prints
 Example 1 acid were were
 obtained obtained
 Comparative (C-2) Sodium No prints No prints
 Example 2 polyacrylate were were
 obtained obtained
 EXAMPLES 11 TO 13
 Three kinds of solutions, (A-6) to (A-8), were prepared in the same manner
 as in the preparation of Composition (A), except that the present polymer
 having carboxylic acid or carboxylate groups in Composition (A) was
 changed as set forth in Table 6. Each of these solutions was applied to
 the same surface-treated aluminum sheet as used in Examples 1 to 5, and
 then dried for 2 minutes at 100.degree. C. Thus, lithographic printing
 plate precursors, (A-6) to (A-8), were prepared. The weight of each plate
 after drying was 1.2 g/m.sup.2.
 Each of the lithographic printing plate precursors (A-6) to (A-8) was
 exposed using a semiconductor laser device emitting the infrared ray with
 wavelength of 830 nm under the condition that the output was kept constant
 but the scanning speed was changed. Additionally, the total output applied
 to the plate surface in this exposure step was 169 mW and the beam
 diameter (1/e.sup.2) was 12 .mu.m. Before and after exposure, the contact
 angle of a water drop made with the surface of each plate in the air was
 measured. The water drop used therein had the pH value of 8.8, and was
 constituted of 84.7% of water, 10% of IPA, 5% of triethylamine and 0.3% of
 concentrated hydrochloric acid. The results obtained are shown in Table 7.
 As can be seen from Table 7, even when the scanning speed was increased,
 the contact angle represented an increase over that before exposure. In
 other words, the data shows that a discrimination between water-receptive
 and ink-receptive areas can be made even when the exposure energy is
 small.
 EXAMPLES 14 TO 16
 Three kinds of solutions were prepared so as to have the foregoing
 Composition (B), wherein the present polymer having carboxylic acid or
 carboxylate groups in Composition (B) was changed as shown in Table 6
 respectively. Each of these solutions was applied to the same
 surface-treated aluminum sheet as mentioned above, and then dried for 2
 minutes at 100.degree. C. Thus, lithographic printing plate precursors,
 (B-6) to (B-8), were prepared. The weight of each plate after drying was
 1.2 g/m.sup.2.
 Each of the lithographic printing plate precursors (B-6) to (B-8) was
 exposed using a semiconductor laser device emitting the infrared ray with
 wavelength of 830 nm under the condition that the output was kept constant
 but the scanning speed was changed. Additionally, the total output applied
 to the plate surface in this exposure step was 169 mW and the beam
 diameter (1/e.sup.2) was 12 .mu.m. Before and after exposure, the contact
 angle of a water drop made with the surface of each plate in the air was
 measured. The water drop used therein was tap water. The results obtained
 are shown in Table 7. As can be seen from Table 7, even when the scanning
 speed was increased, the contact angle represented an increase over that
 before exposure. In other words, the data shows that a discrimination
 between water-receptive and ink-receptive areas can be made even when the
 exposure energy is small.
 TABLE 6
 Lithographic Polymer containing
 printing plate carboxylic acid or
 precursor carboxylate groups
 Example 11 (A-6) P-6
 Example 12 (A-7) P-19
 Example 13 (A-8) P-49
 Example 14 (B-6) P-31
 Example 15 (B-7) P-34
 Example 16 (B-8) P-56
 TABLE 6
 Lithographic Polymer containing
 printing plate carboxylic acid or
 precursor carboxylate groups
 Example 11 (A-6) P-6
 Example 12 (A-7) P-19
 Example 13 (A-8) P-49
 Example 14 (B-6) P-31
 Example 15 (B-7) P-34
 Example 16 (B-8) P-56
 EXAMPLES 17 TO 19
 Three kinds of solutions, (A-9) to (A-11), were prepared so as to have the
 foregoing Composition (A), wherein the present polymer having carboxylic
 acid or carboxylate groups was changed as shown in Table 8. These
 solutions were each applied to the aluminum sheet prepared above, and
 dried for 2 minutes at 100.degree. C. Thus, lithographic printing plate
 precursors, (A-9) to (A-11), were prepared The weight of each plate after
 drying was 1.2 g/m.sup.2.
 After storage for 3 days under the high temperature-humidity condition of
 40.degree. C.-70% RH, the lithographic printing plate precursors (A-9) to
 (A-11) thus obtained were each exposed by means of a semiconductor laser
 device emitting the infrared beam of 830 nm, and loaded in a Hidel KOR-D
 printing machine without undergoing development. The fountain solution
 used therein will be described below.
 Fountain solution: pH 8.8 (H.sub.2 O: 84.7%; IPA: 10%; Triethylamine: 5%;
 Concentrated hydrochloric acid: 0.3%)
 After printing, the non-image areas of prints were examined for scumming.
 The scumming properties in the non-imaging area during the printing
 operations were evaluated by the scums on the 1,000th print and 20,000th
 print. The results obtained are shown in Table 8. In every case, prints of
 good inking quality on the imaging area were obtained.
 EXAMPLES 20 To 22
 Three kinds of solutions, (B-9) to (B-11), were prepared so as to have the
 foregoing Composition (B), wherein the present polymer having carboxylic
 acid or carboxylate groups was changed as shown in Table 8. These
 solutions were each applied to the aluminum sheet prepared above, and
 dried for 2 minutes at 100.degree. C. Thus, lithographic printing plate
 precursors, (B-9)to (B-11), were prepared. The weight of each plate after
 drying was 1.2 g/m.sup.2.
 After storage for 3 days under the high temperature-humidity condition of
 40.degree. C.-70% RH, the lithographic printing plate precursors (B-9) to
 (B-11) thus obtained were each exposed by means of a semiconductor laser
 device emitting the infrared beam of 830 nm, and loaded in a Hidel KOR-D
 printing machine without undergoing development. As the fountain solution
 there was used tap water.
 After printing, the non-image areas of prints were examined for scumming.
 The scuming properties in the non-imaging area during the printing
 operations were evaluated by the scums on the 1,000th print and 20,000th
 print. The results obtained are shown in Table 8. In every case, prints of
 good inking quality on the imaging area were obtained.
 TABLE 8
 Polymer
 having Scumming in non-
 Lithographic carboxylic imaging area during
 printing acid or printing
 plate carboxylate 1,000th 20,000th
 precursor groups print print
 Example 17 (A-9) P-5 no scum no scum
 Example 18 (A-10) P-13 no scum no scum
 Example 19 (A-11) P-45 no scum no scum
 Example 20 (B-9) P-29 no scum no scum
 Example 21 (B-10) P-30 no scum no scum
 Example 22 (B-11) P-39 no scum no scum
 EXAMPLES 23 TO 25
 Three kinds of solutions, (D-1) to (D-3), were prepared so as to have the
 following Composition (D), wherein the present polymer having carboxylic
 acid or carboxylate groups in Composition (B) was changed as shown in
 Table 9 respectively. Each of these solutions was applied to the same
 surface-treated aluminum sheet as mentioned above, and then dried for 2
 minutes at 100.degree. C. Thus, lithographic printing plate precursors,
 (D-1) to (D-3), were prepared. The weight of each plate after drying was
 1.1 g/m.sup.2.

Composition (D)
 Polymer having carboxylic acid or 1.0 g
 carboxylate groups (Table 9)
 Megafac F-177 (fluorine-containing 0.06 g
 surfactant, made by Dainippon Ink
 & Chemicals, Inc.)
 Methyl ethyl ketone 20 g
 Methyl alcohol 7 g
 The typing was carried out on each of the lithographic printing plate
 precursors (D-1) to (D-3) thus obtained with a thermal head installed in a
 word processor, Shoin, (trade name, made by Sharp Corporation). The thus
 made lithographic printing plates were each evaluated using the same
 printing machine in the same way as in Examples 1 to 5. The results
 obtained are shown in Table 9. In every case, prints without scumming were
 obtained even after not only 1,000 sheets but also 20,000 sheets were
 printed.
 Comparative Example 3
 A lithographic printing plate (C-3) was prepared in the same manner as in
 Examples 23 to 25, except that the present polymer having carboxylic acid
 or carboxylate groups was replaced by polyacrylic acid. This plate
 underwent plate-making processing and printing operations under the same
 conditions as in Examples 23 to 25. The results obtained are also shown in
 Table 9.
 EXAMPLES 26 TO 28
 Three kinds of solutions, (E-1) to (E-3), were prepared so as to have the
 following Composition (E), wherein the present polymer having carboxylic
 acid or carboxylate groups in Composition (E) was changed as shown in
 Table 9 respectively. Each of these solutions was applied to the same
 surface-treated aluminum sheet as mentioned above, and then dried for 2
 minutes at 100.degree. C. Thus, lithographic printing plate precursors,
 (E-1) to (E-3), were prepared. The weight of each plate after drying was
 1.1 g/m.sup.2.

Composition (E)
 Polymer having carboxylic acid or 1.0 g
 carboxylate groups (Table 9)
 Water 18 g
 Acetonitrile 9 g
 The typing was carried out on each of the lithographic printing plate
 precursors (E-1) to (E-3) thus obtained with a thermal head installed in a
 word processor, Shoin, (trade name, made by Sharp Corporation). The thus
 made lithographic printing plates were each evaluated using the same
 printing machine in the same way as in Examples 6 to 10. The results
 obtained are shown in Table 9. In every case, prints without scumming were
 obtained even after not only 1,000 sheets but also 20,000 sheets were
 printed.
 Comparative Example 4
 A lithographic printing plate (C-4) was prepared in the same manner as in
 Examples 26 to 28, except that the present polymer having carboxylic acid
 or carboxylate groups was replaced by sodium polyacrylate. This plate
 underwent plate-making processing and printing operations under the same
 conditions as in Examples 26 to 28. The results obtained are also shown in
 Table 9.
 TABLE 9
 Polymer
 having
 Lithographic carboxylic
 printing acid or Inking of imaging area upon
 plate carboxylate printing
 precursor groups 1,000th print 20,0000th print
 Example 23 (D-1) P-2 good good
 Example 24 (D-2) P-7 good good
 Example 25 (D-3) P-47 good good
 Example 26 (E-1) P-25 good good
 Example 27 (E-2) P-34 good good
 Example 28 (E-3) P-45 good good
 Comparative (C-3) Polyacrylic No prints No prints
 Example 3 acid were were
 obtained obtained
 Comparative (C-4) Sodium No prints No prints
 Example 4 polyacrylate were were
 obtained obtained
 As demonstrated above, the present invention can provide a lithographic
 printing plate precursor and a photopolymer composition which enable the
 writing by short-duration scanning exposure, namely low-energy heat mode
 exposure, and the making of lithographic printing plate having excellent
 imaging area strength and scumming resistance. Further, the invention can
 provide a lithographic printing plate which does not necessarily require
 development-processing.