The present invention relates to an image-forming layer which comprises a polymer having a carboxyl group-containing group which can be decarboxylated by exposure. According to the present invention, an image-forming layer having an improved coating strength and adhesion to a support, can be obtained.

FIELD OF THE INVENTION 
The present invention relates to a new image-forming layer. In particular, 
the present invention relates to an image-forming layer which is capable 
of forming a negative image for an original by decarboxylating a 
carboxylic acid in a polymer constituting the layer to change the 
solubility of the polymer in an alkali developer. 
BACKGROUND OF THE INVENTION 
Recently, an alkali development method which uses an aqueous alkali 
developer have been employed in place of a conventional development method 
in which a developer which mainly comprising an organic solvent is used in 
a step of forming printing plates or resists due to concerns associated 
with safety and sanitation. Therefore, a photosensitive layer suitable for 
the alkali development is necessitated and various polymers or resins 
containing a carboxyl group are used as binders. However, an image area 
remaining after the exposure and development is swollen with the alkaline 
developer due to the carboxylic acid contained therein. Therefore, when 
such materials are used for the printing plate or resist, the coating 
strength and the adhesion of the layer to a support are insufficient. This 
is an essential problem of the alkali development. 
SUMMARY OF THE INVENTION 
The object of the present invention is, therefore, to provide an 
image-forming layer having improved coating strength and adhesion to the 
support. 
After intensive investigations made for the purpose of attaining the 
above-mentioned object, the inventors have found out that the object can 
be attained by introducing, into a binder polymer, a carboxylic acid or an 
analogue thereto as described in Journal of Photochemistry, Vol. 33 (No. 
2), pages 237 to 255 (1986) and Journal of the Chemical Society, Section 
C, pages 1682 to 1689 (1972), as a carboxylic acid capable of being 
decarboxylated by exposure. The present invention has been completed on 
the basis of this finding. 
The present invention relates to an image-forming layer comprising a 
polymer having a group containing a carboxyl group which can be 
decarboxylated by exposure in the presence or absence of a sensitizer. 
DETAILED DESCRIPTION OF THE INVENTION 
Now, the detailed description will be made on the present invention. 
Preferred examples of the polymers having a group containing a carboxyl 
group which can be decarboxylated by exposure in the presence or absence 
of a sensitizer, which polymers are usable for forming the image-forming 
layer in the present invention (hereinafter referred to as "the present 
polymer"), include those in which the group containing a carboxyl group 
(hereinafter referred to as "carboxyl group-containing group") is 
represented by the formula: 
EQU Y.sub.l X--CH.sub.2 COOH (I) 
which carboxyl group-containing group is connected with the main chain of 
the polymer (P) directly or through a connecting group (Z). 
In the above formula (I), Y represents a substituted or unsubstituted 
alkylene, arylene, aralkylene or divalent heterocyclic ring, k represents 
0 or 1 and l represents 0 or 1. X represents a sulfur atom, an oxygen 
atom, a single bond, C.dbd.W or N--U (W represents an oxygen atom or a 
sulfur atom and U represents a substituted or unsubstituted aryl or alkyl 
group or a hydrogen atom). When k=l=0, X is C.dbd.W. Among X's, the sulfur 
atom, C.dbd.W or N--U is preferred from the viewpoint of the sensitivity. 
From the viewpoint of the sensitivity, it is preferred that the group 
-X--CH.sub.2 COOH is bonded with the aryl nucleus or aromatic heterocyclic 
nucleus when X is a sulfur atom, an oxygen atom, a single bond or N--U. 
This aryl nucleus or heterocyclic nucleus may be in either a side chain or 
the main chain of the polymer. 
Preferred examples of the carboxyl group-containing groups include residues 
having a skeleton of the following compounds: indole-3-acetic acid, 
phenoxyacetic acid, 2-methylphenoxyacetic acid, 3-methoxyphenoxyacetic 
acid., 2nitrophenoxyacetic acid, 3-chlorophenoxyacetic acid, 
4methylphenoxyacetic acid, n-butoxyacetic acid, thiophenoxyacetic acid, 
3-methoxythiophenoxyacetic acid, 2chlorothiophenoxyacetic acid, 
2-methylthiophenoxyacetic acid, 4-nitrothiophenoxyacetic acid, 
n-butylthioacetic acid, phenylacetic acid, 2-nitrophenylacetic acid, 
4nitrophenylacetic acid, 2,4-dinitrophenylacetic acid, benzoylformic acid, 
4-chlorobenzoylformic acid, thiobenzoylformic acid, pyruvic acid, 
N-phenylglycine, N-(3chlorophenyl)glycine, N-(2,4-dichlorophenyl)glycine, 
N-(4acetylphenyl)glycine, N-(2-nitrophenyl)glycine, 
N-(2,4dinitrophenyl)glycine, N-(4-cyanophenyl)glycine, 
N-(2bromophenyl)glycine, N-(2-methylphenyl)glycine, 
N-(2methoxyphenyl)glycine, N-(2,4-dimethoxyphenyl)glycine, 
N-(nbutyl)glycine, N-methyl-N-(2-methylphenyl)glycine, 
N-methyl-N(4-chlorophenyl)glycine, N-methyl-N-(2-nitrophenyl)glycine, 
N-methyl-N-(2-methoxyphenyl)glycine, N-(4carbamoylphenyl)glycine and 
N-(4-sulfamoylphenyl)glycine. 
The above-mentioned carboxyl group-containing group is bonded with the main 
chain of the polymer directly or through a connecting group Z. The 
connecting groups include an ether bond, amide bond, ester bond, urethane 
bond, ureide bond or a connecting group having such a bond. A part of the 
carboxylic acid-containing group may be contained in the main chain of the 
polymer. 
Preferably, the polymer has the following general formula (II): 
EQU P--(Z)--(Y)--X--(CH.sub.2)--COOH]n (II) 
wherein X, Y, l and m are defined as in formula (I) and Z represents a 
group connecting the main chain of the polymer, P, with the group of said 
general formula (I) and is selected from the group consisting of an ether, 
amide, ester, urethane or ureide or a group containing such a bond, m 
represents 0 or 1, n represents a numeral so that the acid content of the 
polymer is 0.01 meq/g to 6.0 meq/g, and when k=l=O, X is &gt;C.dbd.W. 
The connecting groups having the ether bond, amide bond, ester bond, 
urethane bond or ureide bond include those of the following general 
formulae (III), (IV), (V) and (VI): 
EQU --L--R--L).sub.n R-- (III) 
EQU --L--R--L).sub.n (IV) 
EQU --R--L--R).sub.n L-- (V) 
EQU --R--L--R).sub.n (VI) 
wherein R's may be the same or different from one another and each 
represents an alkylene group, arylene group, aralkylene group or divalent 
heterocyclic ring, L's may be the same or different from one another and 
each represents an ether bond, amide bond, ester bond, urethane bond or 
ureide bond, and n represents 0, 1 or 2. 
The polymers having the carboxyl group-containing group include, for 
example, acrylic resins, vinyl polymer resins including vinyl alcohol 
resins, polyurethane resins, polyurea resins, polyvinyl acetal resins, 
polyamide resins and epoxy resins. However, the polymers are not limited 
to them. 
For example, the acrylic resins include homopolymers of monomers of the 
following general formula (VII) and copolymers thereof with another 
monomer copolymerizable therewith (such as an acrylic ester or methacrylic 
ester): 
##STR1## 
The polyurethane resins can be produced by, for example, reacting a diol of 
the following general formula (VIII) with a diisocyanate: 
EQU (HOCH.sub.2 CH.sub.2).sub.2 N--.sub.l X--CH.sub.2).sub.k COOH(VII) 
The polyester resins can be produced by, for example, reacting a diol of 
the above general formula (VIII) with a compound having an acid chloride 
group at both ends. 
The polymer of the present invention has an acid value of preferably 6.0 
meq/g to 0.01 meq/g, particularly 2.0 meq/g to 0.1 meq/g. When it is lower 
than 0.01 meq/g, the developability with an alkali developer is reduced 
and, on the contrary, when it exceeds 6.0 meq/g, the coating strength and 
adhesion to the support are reduced. The resin may contain an additional 
carboxylic acid which does not participate in the decarboxylation induced 
by light. Two or more carboxylic acid-containing groups, which are 
decarboxylated by light, may be introduced into the polymer. 
The weight average molecular weight of the present polymer is 2,000 to 
1,000,000, preferably 8,000 to 200,000, as determined by a gel permeation 
chromatography. When the weight average molecular weight is less than 
8,000, the intensity of the image is reduced and, on the contrary, when it 
exceeds 200,000, the developability is reduced. 
Two or more of the polymers can be used together, or a mixture of the 
polymer with another polymer containing a carboxylic acid which is not 
decarboxylated by light can be used. 
In the latter case, the mixing amount of the other polymer is 95 wt.% or 
less based on the total photosensitive composition. When it exceeds 95 
wt.%, the characteristic feature of the present invention obtained by 
using the special polymer of the present invention is impaired. The 
polymers which can be introduced into the composition together with the 
present polymer include, for example, polyamide, epoxy, polyurethane, 
acrylic, polyester and polyvinyl acetal resins. 
The sensitivity of the composition can be increased by adding a 
photosensitizer. The photosensitizers usable in the present invention 
include, for example, aromatic ketone compounds such as xanthone, 
fluorenone, benzophenone, thioxanthone, 2-methylthioxanthone, 
2-chlorothioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 
acetophenone, naphthylacetone, 4,4'-bisdimethylaminobenzophenone, 
trinitrofluorenone, dibenzosuberone, 
2,5-bis(4'-diethylaminobenzal)cyclopentanone, 
.alpha.,.alpha.-dichloro-4-phenoxyacetophenone and 1-hydroxycyclohexyl 
phenyl ketone; aromatic thioketone compounds such as 
4,4'-bisdimethylaminothiobenzophenone; quinone compounds such as 
benzoquinone, dichlorobenzoquinone, tetrachlorobenzoquinone, 
dichloronaphthoquinone, anthraquinone, phenanthrenequinone, 
dichloroanthraquinone, dinitroanthraquinone, alizarin and 
benzanthraquinone; aromatic nitro compounds such as nitrobenzene, 
1-nitronaphthalene, 4-nitrobiphenyl, 4-nitrotoluene, 1,3-dinitrobenzene 
and 2,4,6-trinitroaniline; aromatic hydrocarbons such as naphthalene, 
anthracene, phenanthrene, benzanthracene and benzpyrene; triarylpyrazoline 
compounds such as triphenylpyrazoline; monoimidazole compounds such as 
tetraphenylimidazole and triphenylimidazole; xanthene compounds such as 
fluoresceine, Eosine Y, Rose Bengal, Erythrosine B and Phloxine; acridine 
compounds such as acriflavine, riboflavin, acridine, 9-phenylacridine, 
N-phenylacridine, phenazine, 2,3-diphenylquinoxaline and 
acenaphtho[1,2-b]quinoxaline; coumarin compounds described in U.S. Pat. 
No. 4,289,844 such as 7-N,N-diethylaminoketocoumarin, 
3-benzoyl-7-diethylaminocoumarin, 3-benzoyl-7-methoxycoumarin and 
3,3'-carbonylbis(7-diethylaminocoumarin); triphenylmethane compounds such 
as Thymol Blue, Bromothymol Blue and Bromocresol Green; and quinazolinone 
compounds such as 2-methyl-3-benzenesulfonyloxy-4(3H)-quinazolinone and 
2-(.beta.-styryl)-3-benzenesulfonyloxy-4(3H)-quinazolinone. A combination 
of two or more of these sensitizers can also be used. 
The photosensitizer is preferably used in an amount of 0.01 to 50 wt.%, 
particularly 0.1 to 30 wt.%, based on the total composition. When the 
amount is less than 0.1 wt.%, the effect of the photosensitizer cannot be 
obtained sufficiently and, on the contrary, when it exceeds 30 wt.%, the 
coating strength and the sensitivity are reduced. 
If necessary, additives such as a dye, pigment, stabilizer, filler, 
surfactant, plasticizer, anti-staining agent and ink-receptivity providing 
agent can be incorporated into the photosensitive composition of the 
present invention to improve the properties thereof. Preferred dyes 
include oil-soluble dyes such as C.I. 26105 (Oil Red RR), C.I. 21260 (Oil 
Scarlet #308), C.I. 74350 (Oil Blue), C.I. 52015 (Methylene Blue), C.I. 
42555 (Crystal Violet) and C.I. 42595 (Victoria Pure Blue). 
The photosensitive composition of the present invention is usually 
dissolved in a solvent. The solution is applied to a suitable support and 
dried. The application amount of the composition is about 0.01 to 500 
g/m.sup.2, preferably 0.1 to 200 g/m.sup.2 (on dry basis). 
The solvents include, for example, methanol, ethanol, isopropanol, 
n-butanol, t-butanol, 2-methoxyethanol, 2-ethoxyethanol, 2-methoxyethyl 
acetate, ethylene glycol, tetrahydrofuran, dioxane, dimethyl sulfoxide, 
N,N-dimethylformamide, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 
2-methoxy-1-propanol, 1-methoxy-2-acetoxypropane, 
2-methoxy-1-acetoxypropane, ethyl acetate, methyl acetate, toluene, xylene 
and mixtures of them. 
The supports to which the photosensitive composition of the present 
invention can be applied include, for example, papers; papers laminated 
with a plastic (such as polyethylene, polypropylene or polystyrene); 
plates of metals such as aluminum (including aluminum alloys), zinc and 
copper; films of plastics such as cellulose diacetate, cellulose 
triacetate, cellulose propionate, cellulose butyrate, cellulose acetate 
butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, 
polystyrene, polypropylene, polycarbonate and polyvinyl acetal; and papers 
and plastic films laminated with the above-mentioned metals or 
vapor-deposited with the metals. Among them, an aluminum plate is 
particularly preferred when it is used as a printing plate, since it has a 
quite high dimensional stability and is inexpensive. Further, composite 
sheets comprising a combination of a polyethylene terephthalate film and 
an aluminum sheet, as described in Japanese Patent Publication for 
Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") No. 
48-18327, are also preferred. 
Supports having a metal surface, particularly aluminum surface, are 
preferably subjected to a surface treatment such as an electrolytic 
graining treatment, composite graining treatment, sand graining treatment, 
immersion treatment in an aqueous solution of sodium silicate, potassium 
fluorozirconate or a phosphate, or anodic oxidation treatment. Preferred 
anodic oxidation treatment methods include a method wherein the anodic 
oxidation is conducted in sulfuric acid with a high current density as 
described in British Patent No. 1,412,768, a method wherein the anodic 
oxidation is conducted by using phosphoric acid as the electrolytic bath 
as described in U.S. Pat. No. 3,511,661, and a method wherein the anodic 
oxidation is conducted in a mixture of phosphoric acid and sulfuric acid 
as described in Japanese Patent Publication for Opposition Purpose 
(hereinafter referred to as "J.P. KOKOKU") No. 46-43124 and Japanese 
Patent Unexamined Published Application (hereinafter referred to as "J.P. 
KOKAI") Nos. 52-103208 and 55-28400. Aluminum plates which were grained 
with sand and then immersed in an aqueous sodium silicate solution, and 
aluminum plates which were subjected to the anodic oxidation and then 
immersed in an aqueous alkali metal silicate solution as described in J.P. 
KOKOKU No. 47-5125 are also preferred. The anodic oxidation is conducted 
by application of electric current in an electrolytic solution comprising 
an aqueous or non-aqueous solution of an inorganic acid such as 
phosphoric, chromic, sulfuric or boric acid or an organic acid such as 
oxalic or sulfamic acid or a salt of such an acid or two or more of the 
solutions, using an aluminum plate as an anode. 
It is also preferred to conduct a sealing treatment after the graining and 
anodic oxidation. The sealing treatment is conducted by immersion in an 
aqueous sodium silicate solution, aqueous polyvinylphosphonic acid 
solution, hot water or hot aqueous solution of an inorganic salt or 
organic salt or by the treatment in a steam bath. 
Further, a silicate electrodeposition method as described in U.S. Pat. No. 
3,658,662 is also effective. 
The photosensitive composition of the present invention applied to the 
support is exposed through a transparent original image having a line or 
halftone dot image and then developed with an aqueous developer to obtain 
a negative relief image for the original. 
The light sources usable for the exposure include, for example, carbon arc 
lamp, mercury lamp, xenon lamp, tungsten lamp, metal halide lamp, argon 
laser and excimer laser. 
The polymer of the present invention is mainly used as a material for 
printing plates and resists.

The following Examples will further illustrate the present invention, which 
by no means limit the invention. In the Examples, percentages and parts 
are given by weight unless otherwise stated. 
[EXAMPLES ] 
(Preparation Example 1) 
Preparation of: 
##STR2## 
16.7 parts of ethyl bromoacetate was added dropwise to a mixture of 17.6 
parts of m-aminomethacrylic anilide, 6.9 parts of potassium carbonate and 
25 parts of N,N-dimethylformamide under stirring and cooling at 0.degree. 
C. or below. After completion of the addition, the mixture was stirred at 
room temperature for 3 hours, 80 parts by weight of water was added to the 
mixture. After extraction with ethyl acetate, the ethyl acetate layer was 
washed with dilute hydrochloric acid and then with saturated aqueous 
common salt solution and dried over magnesium sulfate. The product was 
concentrated by means of an evaporator and a solid thus obtained was 
recrystallized from methanol to obtain 15.0 parts of Compound (B) having 
the following structural formula (B): 
##STR3## 
15.0 parts of Compound (B) was dissolved in 20 parts of ethanol. The 
solution was cooled with ice. A solution of 2.3 parts of sodium hydroxide 
in 60 parts of water was added dropwise to the cooled solution. The 
mixture was stirred at 20.degree. C. for 30 minutes and then washed with 
ethyl acetate. pH of the mixture was adjusted at 2 with a 1 N-aqueous 
hydrochloric acid solution. After washing with ethyl acetate, a 1 
N-aqueous sodium hydroxide solution was added thereto to adjust pH of the 
aqueous layer at 3. After extraction with ethyl acetate followed by drying 
over magnesium sulfate, the product was concentrated by means of an 
evaporator to obtain 9.0 parts of Compound (C) having the following 
structural formula (C): 
##STR4## 
2.34 parts of Compound (C) and 10.28 parts of ethyl methacrylate were 
dissolved in 38.0 parts of methyl cellosolve under a nitrogen atmosphere. 
The solution was stirred and heated at 70.degree. C. 0.164 part of 
azobisisobutyronitrile (AIBN) was added to the solution and the mixture 
was stirred for 5 hours and then at 85.degree. C. for 3 hours to obtain 
Polymer (A) having a weight average molecular weight of 58,000. 
(Preparation Example 2) 
Preparation of: 
##STR5## 
1.6 parts of sodium hydroxide was dissolved in ethanol. A solution of 5 
parts of p-aminothiophenol in 20 parts of ethanol was added to the 
solution. The mixture thus obtained was cooled at 0.degree. C. or below. A 
solution of 3.8 parts of chloroacetic acid and 3.4 parts of sodium 
hydrogencarbonate in 10 parts of water was added dropwise to the mixture, 
while the mixture was kept at 0.degree. C. or below. After completion of 
the addition, the mixture was stirred at 0.degree. C. for 3 hours and then 
adjusted at pH 3. A solid thus formed was filtered to obtain 5.4 parts of 
p-aminothiophenoxyacetic acid. 
5 parts of p-aminothiophenoxyacetic acid and 2.7 parts of pyridine were 
dissolved in 40 parts of DMF. 3.2 parts of methacryloyl chloride was added 
dropwise to the solution at 0.degree. C. or below. After completion of the 
addition, the mixture was stirred at 0.degree. C. for 1 hour and then at 
25.degree. C. for 2 hours. Then, the reaction mixture thus obtained was 
added to 500 parts of an aqueous hydrochloric acid solution having a pH of 
1. After extraction with ethyl acetate, the ethyl acetate layer was dried 
over magnesium sulfate and the concentration was conducted. The crystals 
thus formed were recrystallized from ethyl acetate to obtain 1.26 parts of 
Compound (E) having the following formula (E): 
##STR6## 
1.26 parts of Compound (E) and 5.14 parts of methacrylate were dissolved in 
25 parts of methyl cellosolve under a nitrogen atmosphere. The solution 
was stirred under heating at 70.degree. C. for 5 hours and then at 
80.degree. C. for 3 hours to obtain Polymer (D) having a weight average 
molecular weight of 40,000. 
(Preparation Example 3) 
Preparation of: 
##STR7## 
20.8 parts of a polystyrene having a weight average molecular weight of 
10,000 and 13.5 parts of ethyloxalyl chloride were dissolved in 500 parts 
of carbon disulfide. 18.22 parts of aluminum chloride was slowly added to 
the solution under stirring. The mixture was stirred under reflux for 1.5 
hour and then 70% of carbon disulfide was distilled off. The residue was 
added to a mixture of 40 parts of concentrated hydrochloric acid and 100 
parts of ice. After decantation, water was added to the residue and this 
mixture was decanted. A solid residue thus obtained was dissolved in 
acetone. After reprecipitation from methanol followed by filtration, 11.5 
g of Polymer (G) was obtained. 
##STR8## 
Then, 10 parts of Polymer (G) was dissolved in 600 parts of THF. 50 parts 
of a 1 N aqueous sodium hydroxide solution and 150 parts of water were 
added to the solution and the mixture was refluxed for 2 hours. After 
completion of the reaction, 28.8 parts of acetic acid was added to the 
reaction mixture. The product was reprecipitated from methanol and dried 
to obtain 4.0 parts of Polymer (F). 
Examples 1 to 10 
The surface of an aluminum plate having a thickness of 0.24 mm was grained 
with a nylon brush and an aqueous suspension of 400 mesh pumice powder and 
then thoroughly washed with water. It was immersed in 10% aqueous sodium 
hydroxide solution at 70.degree. C. for 60 second to conduct etching. It 
was washed with running water and then with a 20% nitric acid solution to 
neutralize it. The plate surface was electrolytically roughened by an 
electrochemical surface-roughening method described in J.P. KOKAI No. 
53-67507, viz., the plate was grained in a 1% aqueous sulfuric acid 
solution using alternating sinusoidal current under conditions of V.sub.A 
=12.7 V and V.sub.c =9.1 V so that the quantity of electricity was 160 
C/dm.sup.3. The product was then immersed in a 30% aqueous sulfuric acid 
solution to remove smuts at 55.degree. C. for 2 minutes and then subjected 
to the anodic oxidation in 7% aqueous sulfuric acid solution in order to 
have a thickness of 2.0 g/m.sup.2. The plate was immersed in a 3% aqueous 
sodium silicate solution at 70.degree. C. for 1 minute, washed with water 
and dried. 
A sensitizing solution having the following composition was applied to the 
thus obtained aluminum plate by means of whirler and dried at 80.degree. 
C. for 2 minutes. The dry weight was 2.0 g/m.sup.2. 
______________________________________ 
Composition of the sensitizing solution 
Amount 
______________________________________ 
25% solution of Polymer (A) 
2 g 
in methyl cellosolve 
sensitizer (Table 1) Table 1 
Victoria Pure Blue BOH 0.018 g 
2-methoxyethanol 8.5 g 
______________________________________ 
TABLE 1 
______________________________________ 
Amount 
Example 
Sensitizer (mg) 
______________________________________ 
1 1-nitronaphthalene 17.3 
2 2,4-diethylthioxanthone 26.8 
3 phenanthrenonequinone 20.8 
4 acridine 17.9 
5 phenazine 18.0 
6 anthracene 17.8 
7 3,3'-carbonylbis(7-diethylaminocoumarin) 
46.0 
8 2-methyl-3-benzenesulfonyloxy-4(3H)- 
quinazolinone 40.4 
9 Michler's ketone 26.8 
10 none -- 
______________________________________ 
The photosensitive lithographic plate thus prepared was subjected to an 
image-forming exposure through a step wedge with PS Light (a product of 
Fuji Photo Film Co., Ltd.) at a distance of 1 m for 5 minutes. The plate 
was immersed in a developer having the following composition at room 
temperature for 1 minute and washed with water to remove an unexposed 
region and to obtain lithographic plates (1) to (10) (Examples 1 to 10), 
each having a light blue image. 
______________________________________ 
Composition of the developer 
Amount 
______________________________________ 
sodium sulfite 5 g 
benzyl alcohol 30 g 
sodium carbonate 5 g 
sodium isopropylnaphthalenesulfonate 
12 g 
water 1000 g 
______________________________________ 
The results were shown in the following Table 2. 
TABLE 2 
______________________________________ 
Example Clear step number 
______________________________________ 
1 7 
2 4 
3 12 
4 11 
5 5 
6 2 
7 3 
8 2 
9 10 
10 1 
______________________________________ 
Examples 11 to 20 
The surface of an aluminum plate having a thickness of 0.24 mm was grained 
with a nylon brush and an aqueous suspension of 400 mesh pumice powder and 
then thoroughly washed with water. It was immersed in a 10% aqueous sodium 
hydroxide solution at 70.degree. C. for 60 seconds to conduct etching. It 
was washed with running water and then with a 20% nitric acid solution to 
neutralize it. The plate surface was electrolytically roughened by an 
electrochemical surface-roughening method described in J.P. KOKAI No. 
53-67507, wherein the plate was grained in a 1% aqueous sulfuric acid 
solution using alternating sinusoidal current under conditions of V.sub.A 
=12.7 V and V.sub.c =9.1 V so that the quantity of electricity was 160 
C/dm.sup.3. The product was then immersed in a 30% aqueous sulfuric acid 
solution to remove smuts at 55.degree. C. for 2 minutes and then subjected 
to the anodic oxidation in a 7% aqueous sulfuric acid solution in order to 
provide a thickness of 2.0 g/m.sup.2. The plate was immersed in a 3% 
aqueous sodium silicate solution at 70.degree. C. for 1 minute, washed 
with water and dried. A sensitizing solution having the following 
composition was applied to the thus obtained aluminum plate by means of a 
whirler and dried at 80.degree. C. for 2 minutes. The dry weight was 2.0 
g/m.sup.2. 
______________________________________ 
Composition of the sensitizing solution 
Amount 
______________________________________ 
25% solution of Polymer (D) 
2 g 
in methyl cellosolve 
sensitizer (Table 3) Table 3 
Oil Blue 0.018 g 
2-methoxyethanol 8.5 g 
______________________________________ 
TABLE 3 
______________________________________ 
Amount 
Example 
Sensitizer (mg) 
______________________________________ 
11 1-nitronaphthalene 17.3 
12 2,4-diethylthioxanthone 26.8 
13 phenanthrenequinone 20.8 
14 acridine 17.9 
15 phenazine 18.0 
16 anthracene 17.8 
17 3,3'-carbonylbis(7-diethylaminocoumarin) 
46.0 
18 2-methyl-3-benzenesulfonyloxy-4(3H)- 
quinazolinone 40.4 
19 Michler's ketone 26.8 
20 none -- 
______________________________________ 
The photosensitive lithographic plate thus prepared was subjected to an 
image-forming exposure through a step wedge with PS Light (a product of 
Fuji Photo Film Co., Ltd.) at a distance of 1 m for 10 minutes. The plate 
was immersed in a developer having the following composition at room 
temperature for 1 minute and then washed with water to remove an unexposed 
region and to obtain lithographic plates (11) to (20) (Examples 11 to 20), 
each having a light blue image. 
______________________________________ 
Composition of the developer 
Amount 
______________________________________ 
sodium sulfite 5 g 
benzyl alcohol 30 g 
sodium carbonate 5 g 
sodium isopropylnaphthalenesulfonate 
12 g 
water 1000 g 
______________________________________ 
The results were shown in the following Table 4. 
TABLE 4 
______________________________________ 
Example Clear step number 
______________________________________ 
11 7 
12 4 
13 9 
14 10 
15 5 
16 2 
17 2 
18 2 
19 6 
20 1 
______________________________________ 
Examples 21 to 30 
The surface of an aluminum plate having a thickness of 0.24 mm was grained 
with a nylon brush and an aqueous suspension of 400 mesh pumice powder and 
then thoroughly washed with water. It was immersed in a 10% aqueous sodium 
hydroxide solution at 70.degree. C. for 60 seconds to conduct etching. It 
was washed with running water and then with a 20% nitric acid solution to 
neutralize it. The plate surface was electrolytically roughened by an 
electrochemical surface-roughening method described in J.P. KOKAI No. 
53-67507, wherein the plate was grained in 1% aqueous sulfuric acid 
solution using alternating sinusoidal current under conditions of V.sub.A 
=12.7 V and V.sub.c =9.1 V so that the quantity of electricity was 160 
C/dm.sup.3. The product was then immersed in a 30% aqueous sulfuric acid 
solution to remove smuts at 55.degree. C. for 2 minutes and then subjected 
to the anodic oxidation in a 7% aqueous sulfuric acid solution in order to 
have a thickness of 2.0 g/m.sup.2. The plate was immersed in a 3% aqueous 
sodium silicate solution at 70.degree. C. for 1 minute, washed with water 
and dried. A sensitizing solution having the following composition was 
applied to the thus obtained aluminum plate by means of a whirler and 
dried at 80.degree. C. for 2 minutes. The dry weight was 2.0g/m.sup.2. 
______________________________________ 
Composition of the sensitizing solution 
Amount 
______________________________________ 
Polymer (F) 0.5 g 
sensitizer (Table 5) Table 5 
Victoria Pure Blue B-OH 0.018 g 
tetrahydrofuran 10 g 
______________________________________ 
TABLE 5 
______________________________________ 
Amount 
Example Sensitizer (mg) 
______________________________________ 
21 1-nitronaphthalene 17.3 
22 2,4-diethylthioxanthone 
26.8 
23 phenanthrenequinone 20.8 
24 acridine 17.9 
25 phenazine 18.0 
26 anthracene 17.8 
27 3,3'-carbobis(7-diethylaminocoumarin) 
46.0 
28 2-methyl-3-benzenesulfonyloxy-4(3H)- 
quinazolinone 40.4 
29 Michler's ketone 26.8 
30 none -- 
______________________________________ 
The photosensitive lithographic plate thus prepared was subjected to an 
image-forming exposure through a step wedge with PS Light (a product of 
Fuji Photo Film Co., Ltd.) at a distance of 1 m for 5 minutes. The plate 
was immersed in a developer having the following composition at room 
temperature for 1 minute and the surface thereof was lightly scrubbed with 
an absorbent wadding to remove an unexposed region and to obtain 
lithographic plates (21) to (30) (Examples 21 to 30), each having a light 
blue image. 
______________________________________ 
Composition of the developer 
Amount 
______________________________________ 
sodium sulfite 5 g 
tetrahydrofuran 30 g 
sodium carbonate 5 g 
sodium isopropylnaphthalenesulfonate 
12 g 
water 1000 g 
______________________________________ 
The results were shown in the following Table 6. 
TABLE 6 
______________________________________ 
Example Clear step number 
______________________________________ 
21 9 
22 5 
23 9 
24 11 
25 4 
26 4 
27 3 
28 5 
29 9 
30 5 
______________________________________ 
Comparative Examples 31 to 40 
The surface of an aluminum plate having a thickness of 0.24 mm was grained 
with a nylon brush and an aqueous suspension of 400 mesh pumice powder and 
then thoroughly washed with water. It was immersed in a 10% aqueous sodium 
hydroxide solution at 70.degree. C. for 60 seconds to conduct etching. It 
was washed with running water and then with 20% nitric acid solution to 
neutralize it. The plate surface was electrolytically roughened by an 
electrochemical surface-roughening method described in J.P. KOKAI No. 
53-67507, wherein the plate was grained in 1% aqueous sulfuric acid 
solution using alternating sinusoidal current under conditions of V.sub.A 
=12.7 V and V.sub.c 9.1 V so that the quantity of electricity was 160 
C/dm.sup.3. The product was then immersed in 30% aqueous sulfuric acid 
solution to remove smuts at 55.degree. C. for 2 minutes and then subjected 
to the anodic oxidation in a 7% aqueous sulfuric acid solution in order to 
have a thickness of 2.0 g/m.sup.2. The plate was immersed in a 3% aqueous 
sodium silicate solution at 70.degree. C. for 1 minute, washed with water 
and dried. A sensitizing solution having the following composition was 
applied to the thus obtained aluminum plate by means of a whirler and 
dried at 80.degree. C. for 2 minutes. The dry weight was 2.0 g/m.sup.2. 
______________________________________ 
Composition of the sensitizing solution 
Amount 
______________________________________ 
25% solution of Polymer (H) 
2 g 
in methyl cellosolve 
sensitizer (Table 7) Table 7 
Oil Blue 0.018 g 
2-methoxyethanol 8.5 g 
Polymer (H): 
##STR9## 
(weight average molecular weight: 55,000) 
______________________________________ 
TABLE 7 
______________________________________ 
Amount 
Example 
Sensitizer (mg) 
______________________________________ 
31 1-nitronaphthalene 17.3 
32 2,4-diethylthioxanthone 26.8 
33 phenanthrenequinone 20.8 
34 acridine 17.9 
35 phenazine 18.0 
36 anthracene 17.8 
37 3,3'-carbonylbis(7-diethylaminocoumarin) 
46.0 
38 2-methyl-3-benzenesulfonyloxy-4(3H)- 
quinazolinone 40.4 
39 Michler's ketone 26.8 
40 none -- 
______________________________________ 
The photosensitive lithographic plate thus prepared was subjected to an 
image-forming exposure through Fuji PS Step Guide (a product of Fuji Photo 
Film Co., Ltd.) at a distance of 1 m with PS Light (a product of Fuji 
Photo Film Co., Ltd.) for 10 minutes. The plate was immersed in a 
developer having the following composition at room temperature for 1 
minute. No image could be formed. 
______________________________________ 
Composition of the developer 
Amount 
______________________________________ 
sodium sulfite 5 g 
benzyl alcohol 30 g 
sodium carbonate 5 g 
sodium isopropylnaphthalenesulfonate 
12 g 
water 1000 g 
______________________________________