A light-sensitive composition which is developable with an aqueous alkaline solution, comprising (a) at least one light-sensitive resin obtained by adding an active mercaptocarboxylic acid to a part of carbon-carbon unsaturated bonds of a polymer having at least two photodimerizable unsaturated double bonds adjacent to an aromatic nucleus in the main chain thereof and (b) optionally at least one negative-working diazo resin. The light-sensitive composition makes it possible to prepare a light-sensitive plate capable of developing with an aqueous alkaline solution without forming insoluble substances in the developer during the development and the adhesive force between the substrate and the light-sensitive layer of the plate is increased, which in turn substantially improves the printing durability of the lithographic printing plate as a final product.

BACKGROUND OF THE INVENTION 
1. (Field of the Invention) 
The present invention relates to a light-sensitive composition suitable for 
preparing a presensitized plate for use in making a lithographic printing 
plate (hereunder referred to as "PS plate") and more particularly to a 
light-sensitive composition containing a photocrosslinkable polymer 
soluble in an aqueous alkaline solution and capable of getting swollen 
with the alkaline solution, which comprises cinnamate ester type 
photodimerizable groups and alkaline-soluble carboxyl groups in the main 
chain thereof and which has improved adhesion to an aluminum substrate. 
2. (Description of the Prior Art) 
Photocross-linkable materials (or light-sensitive resins) which are 
cross-linked by a ring-addition reaction have been well known in the art 
and these materials have been used as materials for forming images such as 
PS plates and Large Scale Integrated Circuit (LSI) elements. Among these 
photocross-linkable materials, useful ones are those having cinnamyl, 
cinnamylidene or chalcone groups carrying photocross-linkable unsaturated 
double bonds adjacent to an aromatic nucleus on the side chains or the 
main chain thereof and some of these have already been put into practical 
use. In particular, it is known that a light-sensitive polyester resin 
having, in the main chain of the molecule, cinnamic acid skeletal 
structures exhibits a rather high sensitivity. Such a light-sensitive 
polyester can be prepared by condensing a phenylene diacrylic acid or an 
alkyl ester thereof and glycol. In general, such a light-sensitive resin 
should be aqueous alkaline soluble in order to prevent environmental 
pollution from waste liqour when it is used as a PS plate by applying it 
on, for instance, an aluminum substrate. Moreover, it should be highly 
adherent to such a substrate as an aluminum plate to prevent images formed 
thereon from being peeled off by a brush or the like during development 
and from causing defects thereon and to impart sufficient printing 
durability to the final products such as lithographic printing plates. 
However, the aforementioned light-sensitive resins do not satisfy the 
foregoing requirements and, therefore, these resins have a limited 
application and cannot generally be used in obtaining light-sensitive 
layers of PS plates. 
In order to eliminate such disadvantages, many attempts have been directed 
to the development of the improved light-sensitive resins. For instance, 
U.S. Pat. No. 4,640,887 (Japanese Patent Un-examined Publication 
(hereinafter referred to as "J.P. KOKAI") No. 60-191244) discloses the use 
of an alkaline soluble light-sensitive composition composed of polymeric 
light-sensitive compounds obtained by reacting a polyester prepolymer 
which has photodimerizable unsaturated double bonds adjacent to an 
aromatic nucleus in the main chain thereof, carboxyl groups on the side 
chains thereof and hydroxyl groups at the termini, with a chain extender 
having at least two functional groups capable of reacting with the 
hydroxyl groups of the prepolymer, such as diisocyanate compounds, 
diphenyl terephthalate, diphenyl carbonate and 
terephthaloyl-bis(N-caprolactam); and a polymeric light-sensitive compound 
obtained by reacting a polyester or polyurethane prepolymer which has 
photocrosslinkable unsaturated double bonds adjacent to an aromatic 
nucleus in its main chain and hydroxyl groups at the termini thereof with 
a chain extender such as dianhydride of pyromellitic acid or cyclopentane 
tetracarboxylic acid to introduce carboxyl groups into the side chains 
thereof. 
However, the following complicated steps must be required to prepare the 
aforementioned light-sensitive polymeric compounds: 
(1) reacting a polybasic carboxylic acid component such as a dicarboxylic 
acid having a light-sensitive unsaturated double bonds adjacent to an 
aromatic nucleus with a polyol component to form an oligoester having 
hydroxyl groups at the termini thereof; 
(2) reacting the oligoester having hydroxyl groups at the termini with a 
cyclic acid anhydride while adjusting the ratio therebetween so that the 
hydroxyl groups at the termini of the oligoester certainly remains 
unchanged; then 
(3) reacting the oligoester obtained in the step (2) with a chain extender 
capable of reacting with the hydroxyl groups of the oligoester to form a 
polymer. These steps require very delicate operations in selecting the 
concentrations of the chemicals to be reacted and reaction temperature and 
involve side reactions which provide by-products in addition to the 
desired product, which in turn causes gelation to form insoluble 
substances during development of the light-sensitive layer formed 
therefrom. Therefore, such a process cannot appropriately provide 
light-sensitive polymers having desired properties. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
light-sensitive composition which has high sensitivity and can be 
developed with an aqueous alkaline developer. 
Another object of the present invention is to provide a light-sensitive 
composition which does not cause the formation of insoluble substances 
during the development. 
A further object of the present invention is to provide a light-sensitive 
composition useful in preparing a light-sensitive final product which has 
high adhesion between the light-sensitive layer and an aluminum substrate 
and exhibits excellent printing durability. 
The aforementioned objects of the present invention can effectively be 
achieved by providing a light-sensitive composition which can be developed 
with an aqueous alkaline developer and which comprises at least one 
light-sensitive resin obtained by adding an active mercaptocarboxylic acid 
to a part of carbon-carbon unsaturated double bonds of a polymer having at 
least two photodimerizable unsaturated double bonds adjacent to an 
aromatic nucleus in the main chain thereof. 
According to another aspect of the present invention, there is further 
provided a light-sensitive composition which can be developed with an 
aqueous alkaline developer and which comprises (a) at least one 
light-sensitive resin obtained by adding an active mercaptocarboxylic acid 
to a part of carbon-carbon unsaturated double bonds of a polymer having at 
least two photodimerizable unsaturated double bonds adjacent to an 
aromatic nucleus in the main chain thereof; and (b) at least one 
negative-working diazo resin. 
DETAILED EXPLANATION OF THE INVENTION 
The light-sensitive composition of the present invention will hereunder be 
explained in more detail. 
I. Polymer 
Polymers having at least two photodimerizable unsaturated double bonds 
adjacent to an aromatic nucleus in the main chain thereof used in the 
composition of the present invention are those having the following 
light-sensitive groups: 
##STR1## 
in the main chain thereof, such as polyesters, polycarbonates and 
polysulfonates. 
Examples of such polymers having the foregoing light-sensitive groups in 
the main chain thereof are polyesters as disclosed in U.S. Pat. No. 
3,030,208; and U.S. Pat. Nos. 3,453,237 and 3,622,320. These polyesters 
may be prepared by condensing an appropriate polycarboxylic acid or a 
lower alkyl ester or chloride thereof with a polyol in the presence of an 
esterifying catalyst. The polycarbonates may be prepared by reacting one 
or more of polyols with phosgene; or reacting a bischloroformate of polyol 
with another polyol. The foregoing light-sensitive groups can be present 
in either the polycarboxylic acid or the polyol. 
II. Polycarboxylic Acids 
Preferred specific examples of such polycarboxylic acids having such 
light-sensitive groups include those represented by the following general 
formulas (1) to (7): 
##STR2## 
in the above general formulas (1) to (7), R.sub.1 and R.sub.1 ' represent 
independently an alkyl group having 1 to 4 carbon atoms, an alkoxy group 
having 1 to 4 carbon atoms, a halogen atom or a nitro group; R.sub.3 
represents an alkylene group having 2 to 4 carbon atoms; and n and n' are 
independently an integer of 1 to 4, provided that if n or n' is 2 to 4, 
R.sub.1 and R.sub.1 ' may be the same or different. 
Suitable examples of the foregoing dicarboxylic acids or derivatives 
thereof are p-phenylenediacryl acid, 2,5-dimethoxy-p-phenylenediacrylic 
acid, p-carboxycinnamic acid and bis(p-cinnamic acid)-diethylene glycol 
ether. 
III. Polyols 
If one of the foregoing compounds represented by the general formulas (1) 
to (7) is used as the dicarboxylic acid component, various polyols may be 
employed as the polyol component without any restriction and examples 
thereof include ethylene glycol, diethylene glycol, triethylene glycol, 
propylene glycol, dipropylene glycol, polyethylene glycol, polypropylene 
glycol, neopentyl glycol, 1,3-butylene glycol, 1,6-hexanediol, 
2-butene-1,4-diol, 2,2,4-trimethyl-1,3-pentanediol, 
1,4-bis-.beta.-hydroxyethoxycyclohexane, cyclohexanedimethanol, 
tricyclodecanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol 
F, ethylene oxide adduct of bisphenol A, propylene oxide adduct of 
bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A and 
propylene oxide adduct of hydrogenated bisphenol A. 
The molecular weight of these polymeric light-sensitive compounds 
preferably ranges from 2,000 to 1,000,000 and more preferably from 5,000 
to 200,000 (expressed in weight average molecular weight measured by GPC). 
IV. Active Mercaptocarboxylic Acids 
The active mercaptocarboxylic acids as used herein are compounds 
represented by the following general formula: 
EQU HS--R--COOH 
wherein R represents an alkylene group having 1 to 11 carbon atoms. 
Suitable examples of such active mercaptocarboxylic acids include 
mercaptoacetic acid, 3-mercaptopropionic acid, 2-mercaptopropionic acid, 
6-mercaptocaproic acid, 11-mercaptoundecanoic acid, 12-mercaptododecanoic 
acid, mercaptosuccinic acid, mono-butyl mercaptosuccinate and 
4-mercaptomethylphenyl-propionic acid. 
The addition reaction of the active mercaptocarboxylic acid with the 
foregoing photocross-linkable polymer may be carried out by heating these 
reagents in a proper solvent in the presence of a radical initiator. 
Examples of such radical initiators usable in the addition reaction are 
those commonly used in such a reaction, such as N,N'-azobisisobutyronitril 
e, benzoyl peroxide, acetyl peroxide, succinyl peroxide, cumene peroxide 
and N,N'-azobisvaleronitrile. In addition, examples of the solvents used 
in the reaction include methyl ethyl ketone, methyl isobutyl ketone, ethyl 
cellosolve, methyl cellosolve, dioxane, 2-methoxyethyl acetate and 
2-ethoxyethyl acetate. 
The thiol groups of the active mercaptocarboxylic acids are added to 
photocross-linkable unsaturated double bonds of the polymer due to this 
addition reaction to form thioether bonds and carboxyl groups are thereby 
introduced into the polymer as substituents in the polymer chain. 
The mercaptocarboxylic acid used to introduce carboxyl groups into the 
polymer chains should be used in an amount sufficient to form polymers 
having a desired number of carboxyl groups therein. In general, the amount 
thereof desirably ranges from about 1 to about 10 times the equivalent 
weight of the carboxyl groups to be added. 
Carboxyl groups are preferably introduced into the polymer in an amount 
such that the acid value of the light-sensitive polymer ranges from 15 to 
200. This is because, if the acid value is less than 15, the solubility of 
the polymer in an aqueous alkaline solution is lowered while if it is more 
than 200, the resultant light-sensitive layer extremely gets swollen with 
an aqueous alkaline solution when it is photohardened. 
V. Negative-working Diazo Resins 
Preferred negative-working diazo resins as used herein are those 
substantially insoluble in water and soluble in an organic solvent. 
Examples of such diazo resins are acid addition salts of products obtained 
by condensing, in an ordinary manner, a diazo monomer such as 
4-diazo-diphenylamine, 1-diazo-4-N,N-dimethylaminobenzene, 
1-diazo-4-N,N-diethylaminobenzene, 
1-diazo-4-N-ethyl-N-hydroxyethylaminobenzene, 
1-diazo-4-N-methyl-N-hydroxyethylaminobenzene, 
1-diazo-2,5-diethoxy-4-benzoylaminobenzene, 
1-diazo-4-N-benzylaminobenzene, 1-diazo-4-morpholinobenzene, 
1-diazo-2,5-dimethoxy-4-p-tolymercaptobenzene, 
1-diazo-2-ethoxy-4-N,N-dimethylaminobenzene, p-diazo-dimethylaniline, 
1-diazo-2,5-dibutoxy-4-morpholinobenzene, 
1-diazo-2,5-diethoxy-4-morpholinobenzene, 
1-diazo-2,5-dimethoxy-4-morpholinobenzene, 
1-diazo-2,5-diethoxy-4-morpholinobenzene, 
1-diazo-2,5-diethoxy-4-p-tolymercaptobenzene, 
1-diazo-3-ethoxy-4-N-methyl-N-benzylaminobenzene, 
1-diazo-3-chloro-4-N,N-diethylaminobenzene, 
1-diazo-3-methyl-4-pyrrolidinobenzene, 
1-diazo-2-chloro-4-N,N-dimethylamino-5-methoxybenzene, 
1-diazo-3-methoxy-4-pyrrolidinobenzene, 3-methoxy-4-diazodiphenylamine, 
3-ethoxy-4-diazodiphenylamine, 3-(n-propoxy)-4-diazodiphenylamine, and 
3-(isopropoxy)-4-diazodiphenylamine; and a condensing agent such as 
formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, 
isobutylaldehyde or benzaldehyde in an molar ratio ranging from 1:1 to 
1:0.5, preferably from 1:0.8 to 1:0.6. Examples of the acids are 
tetrafluoroboric acid, hexafluorophosphoric acid, triisopropylnaphthalene 
sulfonic acid, 5-nitro-o-toluene sulfonic acid, 5-sulfosalicylic acid, 
2,5-dimethylbenzene sulfonic acid, 2,4,6-trimethylbenzene sulfonic acid, 
2-nitrobenzene sulfonic acid, 3-chlorobenzene sulfonic acid, 
3-bromobenzene sulfonic acid, 2-fluorocaprylnaphthalene sulfonic acid, 
dodecylbenzene sulfonic acid, 1-naphthol-5-sulfonic acid, 
2-methoxy-4-hydroxy-5-benzoyl-benzene sulfonic acid and p-toluene sulfonic 
acid. Inter alia, preferred are hexafluorophosphoric acid and alkyl 
aromatic sulfonic acids such as triisopropylnaphthalene sulfonic acid and 
2,5-dimethylbenzene sulfonic acid. 
These diazo resins are incorporated into the light-sensitive composition of 
the present invention in an amount ranging from 0.1 to 15% by weight and 
preferably from 0.3 to 5% by weight with respect to the total amount of 
the composition. 
VI. Light-sensitive Composition 
The light-sensitive composition of the present invention may preferably 
comprise, in addition to the photocross-linkable polymer soluble in an 
aqueous alkaline solution thus prepared, sensitizers and heat 
polymerization inhibitors according to need. In addition, the foregoing 
polymer is neutralized with an alkali such as sodium hydroxide and 
potassium hydroxide prior to use the same when the resultant product is 
developed with water. The composition may optionally comprise dyes and/or 
pigments for the purpose of coloring the light-sensitive layer and pH 
indicators as agents or compositions for obtaining a visible image 
immediately after imagewise exposure to light. 
Examples of such sensitizers include benzophenone derivatives, benzanthrone 
derivatives, quinones, aromatic nitro compounds, naphthothiazoline 
derivatives, benzothiazoline derivatives, thioxanthones, naphthothiazole 
derivatives, ketocoumarin compounds, benzothiazole derivatives, 
naphthofuranone compounds, pyrylium salts and thiapyrylium salts. Specific 
examples thereof include Michler's ketone, N,N'-diethylaminobenzophenone, 
benzanthrone, (3-methyl-1,3-diaza-1,9-benz) anthrone, picramide, 
5-nitroacenaphthene, 2-chlorothioxanthone, 2-isopropylthioxanthone, 
dimethylthioxanthone, methylthioxanthone-1-ethylcarboxylate, 
2-nitrofluorene, 2-dibenzoylmethylene-3-methylnaphthothiazoline, 
3,3-carbonyl-bis(7-diethylaminocoumarin), 2,4,6-triphenylthiapyrylium 
perchlorate and 2-(p-chlorobenzoyl)-naphthothiazole. The amount of these 
sensitizers ranges from about 1 to 20% by weight, preferably 3 to 10% by 
weight on the basis of the total amount of the light-sensitive 
composition. 
Examples of the heat polymerization inhibitors useful in the composition 
include hydroquinone, p-methoxyphenol, di-tert-butyl-p-cresol, pyrogallol, 
tert-butylcatechol, benzoquinone, 
4,4'-thiobis(3-methyl-6-tert-butylphenol), 
2,2'-methylene-bis(4-methyl-6-tert-butylphenol) and 
2-mercaptobenzimidazole. 
The light-sensitive composition of the present invention may further 
comprise plasticizers or the like. Examples of such plasticizers are 
dialkyl phthalates such as dibutyl phthalate and dihexyl phthalate; 
oligoethylene glycol alkyl ester and phosphoric acid ester type 
plasticizers. 
The light-sensitive composition of the present invention may optionally 
contain stabilizers for the diazo resins such as phosphoric acid, 
phosphorous acid, tartaric acid, citric acid, malic acid, dipicolinic 
acid, polynuclear aromatic sulfonic acids and salts thereof, and 
sulfosalicylic acid. 
VII. PS Plates (Presensitized Plates for Use in Making Lithographic 
Printing Plates) 
PS plates may be prepared by applying, onto a substrate, a solution of the 
aforementioned light-sensitive composition in a suitable solvent. Examples 
of solvents usable in the invention include 2-methoxyethanol, 
2-methoxyethyl acetate, propylene glycol monomethyl ether, 
3-methoxypropanol, 3-methoxypropyl acetate, methyl ethyl ketone, ethylene 
dichloride, methyl butyrate and ethyl butyrate, which may be used alone or 
in combination. The coated amount of the light-sensitive composition 
preferably ranges from about 0.1 to 10 g/m.sup.2, more preferably from 0.5 
to 5 g/m.sup.2 expressed in the amount weighed after drying. 
Preferred substrates to which the light-sensitive composition of the 
present invention is applied are plate-like materials exhibiting good 
dimensional stability. Any conventional substrates for lithographic 
printing plates which are known to have good dimensional stability may 
desirably be used in the present invention. Examples of such substrates 
include paper, paper which has been laminated with a plastic film such as 
polyethylene, polypropylene and polystyrene films, metal plates such as 
aluminum (inclusive of aluminum alloy), zinc and copper plates, plastic 
films such as cellulose diacetate, cellulose triacetate, cellulose 
propionate, cellulose butyrate, cellulose acetate butyrate, cellulose 
nitrate, polyethylene terephthalate, polyethylene, polystyrene, 
polypropylene, polycarbonate and polyvinyl acetal films, and paper and 
plastic films which have been laminated with films of the foregoing metals 
or on which layers of the foregoing metals are deposited. Particularly 
preferred are aluminum plates because of its high dimensional stability 
and low cost. In addition, composite sheets comprised of, for instance, 
polyethylene terephthalate to which an aluminum plate has been bonded as 
disclosed in J.P. KOKOKU No. 48-18327 may also preferably be used in the 
invention. 
If the substrate has a metal, in particular aluminum surface, such a 
surface is preferably subjected to a surface treatment such as graining, 
dipping in an aqueous solution of sodium silicate, potassium 
fluorozirconate or a phosphate, or anodization. Another examples of 
substrates usable in the invention include an aluminum plate which is 
grained and then dipped in an aqueous sodium silicate solution as 
disclosed in U.S. Pat. No. 2,714,066 and an aluminum plate which is 
anodized and then dipped in an aqueous solution of an alkali metal 
silicate as disclosed in J.P. KOKOKU No. 47-5125. As such surface 
treatment, it is also effective to use silicate electrodeposition as 
described in U.S. Pat. No. 3,658,662. 
The anodization treatment can be carried out by passing an electric current 
through the aluminum plate serving as an anode in an electrolyte such as 
an aqueous or non-aqueous solution of an inorganic acid, for instance, 
phosphoric acid, chromic acid, sulfuric acid and boric acid; or an organic 
acid, for instance, oxalic acid and sulfamic acid, or a mixed solution 
thereof. 
It is suitable in the invention to use an electolytically grained 
substrates disclosed in J.P. KOKOKU No. 46-27481 and J.P. KOKAI Nos. 
52-58602 and 52-30503 which have been subjected to a combination of the 
foregoing anodization and dipping in a sodium silicate solution; and 
substrates which have been grained with a brush, electrolytically grained, 
anodized and then dipped in an aqueous solution of sodium silicate in this 
order, such as those disclosed in J.P. KOKAI No. 56-28893. 
It is also preferable to apply an underlying layer onto the substrates thus 
surface treated. Examples of materials for such an underlying coating 
include water-soluble resins such as polyvinyl phosphonic acid, polymers 
or copolymers having sulfonic acid groups in the side chains thereof and 
polyacrylic acid. These hydrophilizing treatments are carried out to make 
the surface of the substrate hydrophilic, to prevent the occurrence of a 
detrimental reaction between the substrate and the light-sensitive 
composition applied thereon and to enhance the adhesive force between the 
substrate and the light-sensitive layer. 
A lithographic printing plate can be produced by imagewise exposing a 
light-sensitive plate such as a PS plate composed of a substrate provided 
thereon with the light-sensitive composition of the present invention to 
light from a light source enriched in ultraviolet rays such as metal 
halide lamps and high-pressure mercury lamp; developing the exposed plate 
with a developer to remove unexposed portions of the light-sensitive layer 
and then applying a desensitizing gum thereto. 
Preferred developers as used herein are aqueous alkaline solutions 
containing a small amount of an organic solvent such as benzyl alcohol, 
2-phenoxy ethanol and 2-butoxy ethanol. Examples of such developers are 
disclosed in U.S. Pat. Nos. 3,475,171 and 3,615,480. In addition, those 
disclosed in J.P. KOKAI No. 50-26601 and J.P. KOKOKU Nos. 56-39464 and 
56-42860 are likewise excellent as the developers for developing PS plates 
in which the light-sensitive composition of the present invention is used. 
As explained above in detail, the light-sensitive composition of the 
present invention is soluble in an aqueous alkaline solution and capable 
of getting swollen. Therefore, light-sensitive materials obtained from 
such a light-sensitive composition can easily be developed with an 
alkaline water without forming any insoluble substances in the developer 
during the development thereof. In addition, the light-sensitive materials 
can be improved in their adhesive force between the substrate and the 
light-sensitive layer and hence the printing durability. 
The light-sensitive composition of the present invention will hereunder be 
explained in more detail with reference to the following non-limitative 
working examples. Moreover, the effects practically attained by the 
invention will also be discussed in comparison with Comparative Examples 
given below. In the following Examples, the term "%" means "% by weight" 
unless otherwise specified.

EXAMPLE 1 
An aluminum plate of 3 mm thick was grained with a nylon brush and an 
aqueous suspension of pumice stone and then washed with water 
sufficiently. The aluminum plate was etched by immersing it in 10% aqueous 
sodium hydroxide solution at 70.degree. C. for 60 seconds, washed with 
running water, neutralized and washed with 20% nitric acid solution and 
again washed with water. The plate thus treated was electrolytically 
roughened in 1% nitric acid aqueous solution utilizing sign wave 
alternating waved current (V.sub.A =12.7 V) at a quantity of electricity 
of 160 coulomb/dm.sup.2. At this stage, the surface roughness thereof was 
found to be 0.6.mu. (expressed in R.sub.a). The plate was then immersed 
in 30% sulfuric acid solution at 55.degree. C. for 2 minutes to desmut it 
and then anodized for 2 minutes at a current density of 2A/dm.sup.2 in 20% 
sulfuric acid solution so that 2.7 g/m.sup.2 of anodized coating was 
obtained. The plate was then immersed in 2.5% aqueous sodium silicate 
solution maintained at 70.degree. C. for one minute, washed with water and 
dried. 
A solution of a light-sensitive polyester (10 g) obtained by condensing 100 
mole % of p-phenylenediethoxy acrylate and 100 mole % of 
1,4-di-.beta.-hydroxyethoxycyclohexane in the same manner as that 
disclosed in U.S. Pat. No. 3,030,208, 
2,2'-azobis(2,4-dimethylvaleronitrile) (0.5 g) and 3-mercaptopropionic 
acid (2.0 g) in 24.0 g of methyl ethyl ketone and 36.0 g of ether was 
reacted at 60.degree. C. for 5 hours. After the reaction was completed, 60 
g of methyl ethyl ketone was added to the reaction solution to dilute it 
and then the solution was poured into water to precipitate polymers 
formed. The acid value of the polymer thus obtained was 25 and the weight 
averaged molecular weight thereof measured by gel permeation 
chromatography (GPC) was 25,000. This polymer is hereunder referred to as 
"Polymer A". 
Using Polymer A, the following light-sensitive solution (1) was prepared. 
______________________________________ 
Polymer A 3.0 g 
##STR3## 0.3 g 
Dihexyl phthalate 0.2 g 
Megafac F177 (fluorine type nonionic surfactant 
0.02 g 
available from DAINIPPON INK AND CHEMICALS, INC.) 
Methyl ethyl ketone 50.0 g 
Ethylene glycol monomethyl ether 
20.0 g 
Ethylene glycol monomethyl ether acetate 
20.0 g 
______________________________________ 
The light-sensitive solution thus prepared was applied to the substrate 
with a whirler so that the coated amount thereof weighed after drying was 
2.0 g/m.sup.2. The plate was dried at 100.degree. C. for 2 minutes. 
The light-sensitive plate was imagewise exposed to light through a negative 
film closely adhered thereto for 40 counts with a printer available from 
NuArc Co., Ltd. in U.S.A. (provided with a metal halide lamp of 2 KW). 
After the exposure to light, the light-sensitive plate was developed with 
a developer having the following composition at 25.degree. C. for one 
minute. No insoluble substance was observed in the developer during the 
development. 
______________________________________ 
Developer 
______________________________________ 
Benzyl alcohol 4.5 g 
38% Aqueous solution of sodium isopropyl- 
4.5 g 
naphthalene sulfonate 
Triethanolamine 1.5 g 
Monoethanolamine 0.1 g 
Sodium sulfite 0.3 g 
Pure Water 100 g 
______________________________________ 
The resultant lithographic printing plate was set on a printing machine, 
Hidel SOR Printer, and as a result, it was found that the plate provided 
100,000 printed matters without any troubles. 
EXAMPLE 2 
A solution which comprises 10 g of the light-sensitive polyester used in 
Example 1, 0.5 g of 2,2'-azobis(2,4-dimethylvaleronitrile), 3.0 g of 
mercaptosuccinic acid, 24.0 g of methyl ethyl ketone and 36.0 g of 
ethylene glycol monomethyl ether acetate was reacted at 60.degree. C. for 
5 hours. After the reaction, 60 g of methyl ethyl ketone was added to the 
solution to dilute it and then the diluted solution was poured into water 
to precipitate polymers formed. The acid value of this polymer was 33 and 
the weight average molecular weight thereof was found to be 38,000 by GPC 
measurement. This polymer is hereunder referred to as "Polymer B". A 
lithographic printing plate was prepared in the same manner as in Example 
1 except for using Polymer B instead of Polymer A. Likewise, the printing 
operation was effected as in Example 1 and thus 100,000 printed matters 
were obtained without any troubles. In this Example, any insoluble 
substance was not observed in the developer during the development. 
EXAMPLE 3 
Polymer C was prepared in the same manner for preparing Polymer A as in 
Example 1 except for substituting 1.2 g of 11-mercaptoundecanoic acid for 
3-mercaptopropionic acid. The acid value of this polymer was 28 and the 
weight average molecular weight thereof measured by GPC was 32,000. 
A lithographic printing plate was prepared in the same manner as in Example 
1 except for using Polymer C instead of Polymer A. Likewise, printing 
operation was effected as in Example 1 and thus 100,000 printed matters 
were obtained without any troubles. In this Example, any insoluble 
substance was not observed in the developer during the development. 
EXAMPLES 4 TO 6 
The same procedures as in Example 1 were repeated except that 0.15 g of 
each diazo resin listed in Table I given below was incorporated into 
light-sensitive solutions to prepare lithographic printing plates. Each 
printing plate was set on a printing machine, Hidel SOR Printer, to obtain 
printed matters. The results thus obtained are summarized in Table I. 
TABLE I 
__________________________________________________________________________ 
Printing dura- 
bility (number 
of printed 
Ex. No. 
Diazo resin used in the Solution 
matters) 
__________________________________________________________________________ 
4 PF.sub.6 salt of the condensate of p-diazo- 
250,000 
diphenylamine and formaldehyde 
5 Dodecylbenzene sulfonate of the condensate 
200,000 
of p-diazodiphenylamine and formaldehyde 
6 2-Methoxy-4-hydroxy-5-benzoylbenzene sulfonate 
250,000 
of the condensate of p-diazodiphenylamine 
and formaldehyde 
__________________________________________________________________________ 
EXAMPLES 7 TO 9 
The same procedures as in Example 2 were repeated except that 0.15 g of 
each diazo resin listed in Table II given below was incorporated into 
light-sensitive solutions to prepare lithographic printing plates. Each 
printing plate was set on a printing machine, Hidel SOR Printer, to obtain 
printed matters. The results thus obtained are summarized in Table II. 
TABLE II 
__________________________________________________________________________ 
Printing dura- 
bility (number 
of printed 
Ex. No. 
Diazo resin used in the Solution 
matters) 
__________________________________________________________________________ 
7 PF.sub.6 salt of the condensate of p-diazo- 
220,000 
diphenylamine and formaldehyde 
8 Dodecylbenzene sulfonate of the condensate 
180,000 
of p-diazodiphenylamine and formaldehyde 
9 2-Methoxy-4-hydroxy-5-benzoylbenzene sulfonate 
200,000 
of the condensate of p-diazodiphenylamine 
and fomaldehyde 
__________________________________________________________________________