A photopolymerizable composition comprises at least one addition polymerizable compound having at least one ethylenically unsaturated bond and at least one photopolymerization initiator represented by the following general formula (I): ##STR1## wherein R.sub.1 to R.sub.4 independently represent hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, hydroxyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted amino group with the proviso that R.sub.1 to R.sub.4 may form a non-metallic ring together with the carbon atoms bonded thereto; R.sub.5 and R.sub.6 each represents hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a heteroaromatic group, an acyl group, cyano group, an alkoxycarbonyl group, carboxyl group or a substituted alkenyl group with the proviso that R.sub.5 and R.sub.6 may form a non-metallic ring together with the carbon atoms bonded thereto; X represents O, S, NH or a nitrogen atom having a substituent; and G.sub.1 and G.sub.2 each represents hydrogen atom, cyano group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted or unsubstituted acyl group, a substituted or unsubstituted arylcarbonyl group, an alkylthio group, an arylthio group, an alkylsulfonyl group, an arylsulfonyl group or a fluorosulfonyl group with the proviso that G.sub.1 and G.sub.2 cannot simultaneously represent hydrogen atom and that G.sub.1 and G.sub.2 may form a non-metallic ring together with the carbon atoms bonded thereto. This composition provides light-sensitive layer of highly sensitive to light from a variety of light sources.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a photopolymerizable composition and more 
particularly to a photopolymerizable composition comprising an addition 
polymerizable compound having ethylenically unsaturated bonds, a 
photopolymerization initiator and optionally a binder, which is useful as 
a light-sensitive layer of presensitized plate for use in making 
lithographic printing plates, a light-sensitive layer for use in making 
color proofs, a photoresist for use in making print circuit board and the 
like. 
2. Description of the Prior Art 
It has been well known to form duplicates of images according to a 
photographic manner utilizing a light-sensitive composition composed of a 
polymerizable compound having ethylenically unsaturated bonds and a 
photopolymerization initiator, which optionally contains a proper binder 
capable of forming a film and a heat polymerization inhibitor. As 
disclosed in U.S. Pat. Nos. 2,927,022; 2,902,356 and 3,870,524, such kind 
of light-sensitive compositions make it possible to provide desired images 
of hardened light-sensitive composition by forming a proper film 
therefrom, exposing it to light through a negative carrying desired images 
thereon and removing unexposed areas by selectively dissolving them with a 
proper solvent (hereunder referred to as simply development), since the 
light-sensitive composition causes photopolymerization by irradiating it 
with light and thus causes hardening to make the exposed portions 
insoluble in a developer. It is a matter of course that this kind of 
light-sensitive composition is very useful for forming a presensitized 
plate (hereunder referred to as PS plate), a photoresist or the like. 
Moreover, it has been proposed to incorporate, into the foregoing 
light-sensitive composition, a photopolymerization initiator for the 
purpose of improving the light-sensitivity thereof since a sufficient 
light-sensitivity cannot be expected by simply using a polymerizable 
compound having ethylenically unsaturated bonds and there has been used 
such a photopolymerization initiator as benzil, benzoin, benzoin ethyl 
ether, Michler's ketone, anthraquinone, acridine, phenazine, benzophenone 
or 2-ethylanthraquinone. 
However, when such a photopolymerization initiator is used, the resultant 
light-sensitive composition is inferior in sensitivity to hardening and 
thus it takes a long period of time to expose it to light to form images. 
For this reason, the image having a good performance is not reproduced in 
the case of the reproduction of fine images even when there is a slight 
vibration in the operations of imagewise exposure. In this case, it is 
further required to increase the dosage of radiant rays from a light 
source for exposure and, therefore, it must be provided for a means for 
diffusing a great deal of heat generated during the exposure operation. In 
addition, the heat generated exerts a severe influence on the film of the 
light-sensitive composition and thus causes the deformation and the change 
of properties thereof. 
Recently, it has been investigated to improve the light-sensitive 
composition in its sensitivity to ultraviolet light and since UV 
projection techniques have already been put into practical use for 
manufacturing PS plates or the like the corresponding light-sensitive 
materials of high sensitivity is now under development. However, such 
light-sensitive materials are still insufficient in sensitivity. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary purpose of the present invention to provide a 
photopolymerizable composition having a high sensitivity. 
It is another purpose of the present invention to provide a 
photopolymerizable composition which comprises a photopolymerization 
initiator capable of enhancing the photopolymerization velocity of the 
photopolymerizable composition generally containing a polymerizable 
compound having ethylenically unsaturated bonds. 
The inventors of the present invention have conducted various studies to 
achieve the aforementioned purposes and as a result, have found that 
certain specific photopolymerization initiators allow for the 
polymerizable compound having ethylenically unsaturated bonds to increase 
the photopolymerization velocity thereof and thus have completed the 
present invention. 
Consequently, the present invention relates to a photopolymerizable 
composition which comprises at least one addition polymerizable compound 
having at least one ethylenically unsaturated bond and a 
photopolymerization initiator and the composition is characterized in that 
it comprises, as the photopolymerization initiator, at least one compound 
represented by the following general formula (I): R1 ? 
##STR2## 
wherein R.sub.1 to R.sub.4 each independently represents hydrogen atom, a 
halogen atom, an alkyl group, a substituted alkyl group, an aryl group, a 
substituted aryl group, hydroxyl group, an alkoxy group, a substituted 
alkoxy group, an amino group or a substituted amino group with the proviso 
that R.sub.1 to R.sub.4 may form a ring comprised of non-metallic atoms 
together with the carbon atoms to which they are bonded; R.sub.5 and 
R.sub.6 each independently represents hydrogen atom, an alkyl group, a 
substituted alkyl group, an aryl grouyp, a substituted aryl group, a 
heteroaromatic group, an acyl group, cyano group, an alkoxycarbonyl group, 
carboxyl group or a substituted alkenyl group with the proviso that 
R.sub.5 and R.sub.6 may form a ring composed of non-metallic atoms 
together with the carbon atoms to which they are bonded; X represents 
oxygen atom, sulfur atom, NH or a nitrogen atom having a substituent; 
G.sub.1 and G.sub.2 may or may not be identical and each represents 
hydrogen atom, cyano group, an alkoxycarbonyl group, a substituted 
alkoxycarbonyl group, an aryloxycarbonyl group, a substituted 
aryloxycarbonyl group, an acyl group, a substituted acyl group, an 
arylcarbonyl group, a substituted arylcarbonyl group, an alkylthio group, 
an arylthio group, an alkylsulfonyl group, an arylsulfonyl group or a 
fluorosulfonyl group with the proviso that G.sub.1 and G.sub.2 cannot 
simultaneously represent hydrogen atom and that G.sub.1 and G.sub.2 may 
form a ring of non-metallic atoms together with the carbon atoms to which 
they are bonded.

DETAILED EXPLANATION OF THE INVENTION 
The photopolymerizable composition according to the present invention will 
hereunder be described in more detail. 
The polymerizable compound having ethylenically unsaturated bonds as used 
herein is preferably those having, in the chemical structure thereof, at 
least one ethylenically unsaturated bond at the terminal thereof, which 
are in any chemical form such as monomer, prepolymer, i.e., dimer, trimer 
and an oligomer or a mixture thereof or a copolymer thereof. 
Examples of such monomers and copolymers thereof include such an 
unsaturated carboxylic acid or a salt thereof as acrylic acid, methacrylic 
acid, itaconic acid, crotonic acid, maleic acid and sodium and potassium 
salts of these acids; such an ester as those of unsaturated carboxylic 
acids and aliphatic polyol compounds and such an amide as those of 
unsaturated carboxylic acids and aliphatic polyamine compounds. 
Examples of esters of an aliphatic polyol compound and an unsaturated 
carboxylic acid include such acrylates as ethylene glycol diacrylate, 
triethylene glycol triacrylate, 1,3-butanediol diacrylate, tetramethylene 
glycol diacrylate, propylene glycol diacrylate, trimethylol propane 
triacrylate, trimethylol propane tri(acryloyl-oxypropyl) ether, 
trimethylol ethane triacrylate, 1,4-cyclohexanediol diacrylate, 
tetraethylene glycol diacrylate, pentaerythritol diacrylate, 
pentaerythritol triacrylate, pentaerythritol tetraacrylate, 
dipentaerythritol diacrylate, dipentaerythritol triacrylate, 
dipentaerythritol tetraacrylate, sorbitol triacrylate, sorbitol 
tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate and polyester 
acrylate oligomers; such methacrylates as tetramethylene glycol 
dimethacrylate, triethylene glycol dimethacrylate, trimethylol propane 
methacrylate, trimethylol ethane trimethacrylate, ethylene glycol 
dimethacrylate, 1,3-butanediol dimethacrylate, pentaerythritol 
dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol 
dimethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, 
bis(p-(3-methacryloxy-2-hydroxypropoxy)phenyl)-dimethylmethane and 
bis(p-(acryloxyethoxy)-phenyl)dimethylmethane; such itaconates as ethylene 
glycol diitaconate, propylene glycol diitaconate, 1,3-butanediol 
diitaconate, 1,4-butanediol diitaconate, tetramethylene glycol 
diitaconate, pentaerythritol diitaconate and sorbitol tetraitaconate; such 
crotonates as ethylene glycol dicrotonate, tetramethylene glycol 
dicrotonate, pentaerythritol dicrotonate and sorbitol tetracrotonate; such 
isocrotonates as ethylene glycol diisocrotonate, pentaerythritol 
diisocrotonate and sorbitol tetraisocrotonate; such maleates as ethylene 
glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate 
and sorbitol tetramaleate; and such other esters as ethylene glycol 
mono(meth)acrylate, propylene glycol mono(meth)acrylate, phenoxyethyl 
(meth)acrylate, ethylene glycol di(meth)acrylate, trimethylol ethane 
triacrylate, neopentyl glycol di(meth)acrylate, pentaerythritol 
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol 
hexa(meth)acrylate, hexanediol di(meth)acrylate, trimethylol propane 
tri(acryloyloxypropyl) ether, tri(acryloyloxyethyl) isocyanurate and 
mixtures thereof. 
Examples of such an amide monomer of an aliphatic polyamine compound and an 
unsaturated carboxylic acid include methylenebis-acrylamide, 
methylenebismethacrylamide, 1,6-hexamethylenebis-acrylamide, 
1,6-hexamethylenebis-methacrylamide, diethylene triamine trisacrylamide, 
xylylenebis-acrylamide and xylylenebismethacrylamide. 
Examples of polymerizable compounds having at least one ethylenically 
unsaturated bond at the terminal include vinylurethane compounds having at 
least two polymerizable vinyl groups in the molecules obtained by adding a 
vinyl monomer having a hydroxyl group and represented by the following 
general formula (II) to a polyisocyanate compound having at least two 
isocyanate groups in the molecule, as those disclosed in Japanese Patent 
Publication for Opposition Purpose (hereinafter referred to as "J. P. 
KOKOKU") No. 48-41708: 
EQU CH.sub.2 .dbd.C(R)COOCH.sub.2 CH(R')OH (II) 
wherein R and R' each represents hydrogen or methyl group. 
In addition to the foregoing compounds, there may be mentioned such 
urethane acrylates as those disclosed in J. P. KOKOKU Nos. 48-41708 and 
50-6034 and Japanese Patent Unexamined Published Application (hereinafter 
referred to as "J. P. KOKAI") No. 51-37193; such polyester acrylates as 
those disclosed in J. P. KOKAI No. 48-64183 and J. P. KOKOKU Nos. 49-43191 
and 52-30490; and such polyfunctional acrylates and methacrylates as epoxy 
acrylates obtained by reacting an epoxy resin and a (meth)acrylic acid. 
Moreover, it is also possible to use compounds listed in Bulletin of Japan 
Adhesives Association (Nippon Setchaku Kyokai Shi), 1984, Vol 20, No. 7, 
pp 300-308, as photohardenable monomers and oligomers. 
These polymerizable compounds having ethylenically unsaturated bonds can be 
used in an amount of 5 to 50% by weight (hereunder simply referred to as 
"%") of the total weight of the composition, and preferably 10 to 40%. 
The photopolymerization initiators, the use of which is the important 
characteristic of the photopolymerizable composition according to the 
present invention will now explained in detail below. 
In the photopolymerization initiators which are represented by the 
following general formula (I) and are employed in the photopolymerizable 
composition of the present invention: 
##STR3## 
the alkyl groups included in the definition of R.sub.1 to R.sub.6 may be 
those having 1 to 20 carbon atoms such as methyl, ethyl and tert-butyl 
groups. The aryl group may be those having 6 to 10 carbon atoms such as 
phenyl group. The alkoxy groups included in the definition of R.sub.1 to 
R.sub.4 may be those having 1 to 6 carbon atoms such as methoxy, ethoxy 
and butoxy groups. The substituted amino groups in the definition of 
R.sub.1 to R.sub.4 may be alkylamino group, in which the alkyl moiety has 
1 to 20 carbon atoms, such as methylamino, dimethylamino and diethylamino 
groups; and arylamino groups having 6 to 10 carbon atoms such as 
diphenylamino, piperidino and morpholino groups. 
These alkyl, aryl, alkoxy, alkylamino and arylamino groups may have 
substituents. Examples of such substituents include halogen atoms such as 
fluorine, chlorine and bromine atoms; alkoxycarbonyl groups such as 
ethoxycarbonyl group; alkoxy groups such as methoxy and ethoxy groups; 
aryl groups such as phenyl group; and cyano group. 
As already explained, R.sub.1 to R.sub.4 may form a ring comprised of 
non-metallic atoms together with the carbon atoms to which they are 
bonded. Examples of the compounds including such rings are those 
represented by the following general formulas (A) to (C): 
##STR4## 
Moreover, when R.sub.5 and R.sub.6 represent acyl groups, the acyl group 
may be acetyl and those having an alkyl group having 1 to 10 carbon atoms 
and an aryl group; the alkoxycarbonyl groups in R.sub.5 and R.sub.6 may be 
those having an alkyl group having 1 to 6 carbon atoms such as 
ethoxycarbonyl group. The substituted alkenyl groups therein may be those 
having 2 to 10 carbon atoms such as styryl group and the heteroaromatic 
groups therein may be those represented by the following general formulas 
(D) to (F): 
##STR5## 
In addition, R.sub.5 and R.sub.6 may form a non-metallic ring together with 
the carbon atoms to which they are bonded as explained above. Examples of 
the compounds including such rings are those represented by the following 
genral formula (G): 
##STR6## 
When X is a nitrogen atom having a substituent, examples of such 
substituents include the same alkyl groups and aryl groups as those listed 
above in connection with R.sub.1 to R.sub.6. G.sub.1 and G.sub.2 may be 
identical or different and each represents hydrogen atom, cyano group, an 
alkoxycarbonyl group having an alkyl group of 1 to 10 carbon atoms such as 
ethoxycarbonyl group, an aryloxycarbonyl group having an aryl group of 6 
to 10 carbon atoms such as phenoxycarbonyl group, an acyl group having 1 
to 6 carbon atoms such as acetyl or propionyl group, an arylcarbonyl group 
having 7 to 11 carbon atoms such as benzoyl group, an alkylthio group 
having 1 to 6 carbon atoms such as methylthio or ethylthio group, an 
arylthio group having 6 to 10 carbon atoms such as phenylthio group, an 
arylsulfonyl group having 6 to 10 carbon atoms such as phenylsulfonyl 
group, an alkylsulfonyl group having 1 to 6 carbon atoms such as 
methylsulfonyl or ethylsulfonyl group, or a fluorosulfonyl group. 
These alkoxycarbonyl, aryloxycarbonyl, acyl, arylcarbonyl, alkylthio, 
arylthio, arylsulfonyl and alkysulfonyl groups may have substituents. 
Examples of such substituents include halogen atoms such as chlorine; 
alkoxycarbonyl groups having an alkyl group of 1 to 6 carbon atoms; 
carboxyl group; aryl groups having 6 to 10 carbon atoms; alkoxy groups 
having 1 to 6 carbon atoms; and cyano group. Moreover, aryloxycarbonyl, 
arylcarbonyl, arylthio and arylsulfonyl groups may further have an alkyl 
group having 1 to 6 carbon atoms such as methyl group as the substituent 
in addition to the foregoing groups. 
As explained above, G.sub.1 and G.sub.2 may form a ring of nonmetallic 
atoms together with the carbon atoms to which they are bonded. Such a ring 
is usually used as an acidic nucleus of merocyanine dyes and examples 
thereof include as follows: 
(a) 1,3-dicarbonyl nucleus, for instance, 1,3-indanedione, 
1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione and 
1,3-dioxane-4,6-dione. 
(b) pyrazolinone nucleus, for instance, 
3-methyl-1-phenyl-2-pyrazolin-5-one, 1-phenyl-2-pyrazolin-5-one and 
1-(2-benzothiazoyl)-3-methyl-2-pyrazolin-5-one. 
(c) isoxazolinone nucleus, for instance, 3-phenyl-2-isoxazolin-5-one and 
3-methyl-2-isoxazolin-5-one. 
(d) oxyindole nucleus, for instance, 1-alkyl-2,3-dihydro-2-oxyindole. 
(e) 2,4,6-triketohexahydropyrimidine nucleus, for instance, barbituric 
acid, 2-thiobarbituric acid and derivatives thereof. Examples of such 
derivatives include 1-alkyl derivatives such as 1-methyl and 1-ethyl 
derivatives; 1,3-dialkyl derivatives such as 1,3-diethyl and 1,3-dibutyl 
derivatives; 1,3-diaryl derivatives such as 1,3-diphenyl, 
1,3-di(p-chlorophenl) and 1,3-di(p-ethoxycarbonylphenyl) derivatives; and 
1-alkyl-3-aryl derivatives such as 1-ethyl-3-phenyl derivative. 
(f) 2-thio-2,4-thiazolidinedion nucleus, for instance, rhodanine and 
derivatives thereof. Examples of such derivatives include 3-alkylrhodanine 
such as 3-ethylrhodanine and 3-allylrhodanine; and 3-arylrhodanine such as 
3-phenylrhodanine. 
(g) 2-thio-2,4-oxazolidinedion(2-thio-2,4-(3H,5H)-oxazoledion nucleus, for 
instance, 2-ethyl-2-thio-2,4-oxazolidinedion. 
(h) thianaphthenone nucleus, for instance, 3-(2H)-thianaphthenone and 
3-(2H)-thianaphthenon-1,1-dioxide. 
(i) 2-thio-2,5-thiazolidinedion nucleus, for instance, 
3-ethyl-2-thio-2,5-thiazolidinedione. 
(j) 2,4-thiazolidinedione nucleus, for instance, 2,4-thiazolidinedione, 
3-ethyl-2,4-thiazolidinedione and 3-phenyl-2,4-thiazolidinedione. 
(k) thiazolidinone nucleus, for instance, 4-thiazolidinone and 
3-ethyl-4-thiazolidinone. 
(l) 4-thiazolinone nucleus, for instance, 2-ethylmercapto-5-thiazolin-4-one 
and 2-alkylphenylamino-5-thiazolin-4-one. 
(m) 2-imino-2-oxozolin-4-one nucleus (sub-hydantoin nucleus). 
(n) 2,4-imidazolidinedione (hydantoin) nucleus, for instance, 
2,4-imidazolidinedione and 3-ethyl-2,4-imidazolidinedione. 
(o) 2-thio-2,4-imidazolidinedione-(2-thiohydantoin) nucleus, for instance, 
2-thio-2,4-imidazolidinedione and 3-ethyl-2-thio-2,4-imidazolidinedione. 
(p) 2-imidazolin-5-one nucleus, for instance, 
2-n-propylmercapto-2-imidazolin-5-one. 
(q) furan-5-one nucleus. 
The photopolymerization initiators represented by the general formula (I) 
which can be used in the composition of the present invention may be 
prepared from a compound represented by the general formula (II) or (III) 
and a compound represented by the general formula (IV). 
##STR7## 
wherein L.sub.1 and L.sub.2 represent alkyl groups and Z.sup.- represents 
an anion. 
Specific examples of the photopolymerization initiators represented by the 
general formula (I) are as follows: 
##STR8## 
A binder may be incorporated into the photopolymerizable composition of the 
present invention according to need. With regard to such a binder, it 
should have a good compatibility with the polymerizable compound having 
ethylenically unsaturated bonds and the photopolymerization initiator so 
as not to cause separation during the whole manufacturing processes for 
the light-sensitive material, i.e., the preparation of the coating 
liquids, coating process and drying process, it should not exert adverse 
influence on the development, irrespective of it being dissolution 
development or swelling development, when the composition containing such 
a binder is formed into a light-sensitive layer or a photoresist layer and 
it should have properties required to form a tough film serving as a 
light-sensitive layer or a photoresist layer. 
In general, the binder may properly be selected from linear organic 
polymers. Specific examples thereof include chlorinated polyethylene; 
chlorinated polypropylene; polyalkyl acrylates (examples of such alkyl 
groups include methyl, ethyl, n-propyl, iso-butyl, n-hexyl and 
2-ethylhexyl); copolymers of an alkyl acrylate (examples of the alkyl 
groups are the same as those listed above) and at least one monomer, for 
instance, selected from the group consisting of acrylonitrile, vinyl 
chloride, vinylidene chloride, styrene and butadiene; polyvinyl chloride; 
copolymer of vinyl chloride and acrylonitrile; polyvinylidene chloride; 
copolymer of vinylidene chloride and acrylonitrile; polyvinyl acetate; 
polyvinyl alcohol; polyacrylonitrile; copolymer of acrylonitrile and 
styrene; copolymer of acrylonitrile, butadiene and styrene; polyalkyl 
methacrylates (examples of the alkyl groups include methyl, ethyl, 
n-propyl, n-butyl, iso-butyl, n-hexyl, cyclohexyl and 2-ethylhexyl); 
copolymers of an alkyl methacrylate and at least one monomer selected from 
the group consisting of, for instasnce, acrylonitrile, vinyl chloride, 
vinylidene chloride, styrene and butadiene; polystyrene; 
poly-alphamethylstyrene; polyamides (6-nylon, 6,6-nylon and the like); 
methyl cellulose; ethyl cellulose; acetyl cellulose; polyvinyl formal and 
polyvinyl butyral. 
In addition, if an organic polymer soluble in water or an alkaline aqueous 
solution is used, it becomes possible to develop the resultant composition 
with water or an alkaline aqueous solution. As such polymers, there may be 
mentioned such addition polymers having carboxyl groups at their side 
chains as methacrylic copolymers (e.g., copolymer of methyl methacrylate 
and methacrylic acid, copolymer of ethyl methacrylate and methacrylic 
acid, copolymer of butyl methacrylate and methacrylic acid, copolymer of 
benzyl methacrylate and methacrylic acid, copolymer of allyl methacrylate 
and methacrylic acid, copolymer of ethyl acrylate and methacrylic acid, 
and copolymer of methacrylic acid, styrene and ethyl methacrylate); 
acrylic copolymers (e.g., copolymer of ethyl acrylate and acrylic acid and 
copolymer of ethyl acrylate, styrene and acrylic acid); itaconic 
copolymers, crotonic copolymers and partially esterified maleic 
copolymers. In addition to these examples, other polymers such as acidic 
cellulose derivatives having carboxyl groups at their side chains may also 
be used in the invention. 
These polymers may be used alone as the binder for the composition of the 
present invention. Moreover, these polymers may be used, as the binder, in 
combination in a proper ratio so far as each component of the mixture has 
a good compatibility with other components of the composition so as not to 
cause separation throughout the whole manufacturing processes, ie., from 
the preparation of coating liquid to the coating and drying processes. 
The molecular weight of these polymers used as the binder may widely vary 
depending on the kind thereof. It is preferably in the range of from about 
5,000 to about 2,000,000 and more preferably from 10,000 to 1,000,000. 
It is desirable to add a heat polymerization inhibitor to the 
light-sensitive composition of the present invention for the purpose of 
preventing the polymerizable compound having ethylenically unsaturated 
bonds from causing undesirable heat polymerization during the preparation 
and the storage of the light-sensitive composition of the invention. 
Examples of suitable heat polymerization inhibitors include hydroquinone, 
p-methoxyphenol, di-tert-butyl-p-cresol, pyrogallol, tert-butylcatechol, 
benzoquinone, copper(I) chloride, phenothiazine, chloranil, naphthylamine, 
beta-naphthol, nitrobenzene and dinitrobenzene. 
In addition, a dye or a pigment may optionally be incorporated into the 
composition of the invention for the purpose of coloration of the 
composition. Examples thereof include Methylene Blue, Crystal Violet, 
Rhodamine B, Fuchsine, Auramine, azo dyes, anthraquinone dyes, titanium 
oxide, carbon black, iron oxide, phthalocyanine pigments and azo pigments. 
For the purpose of improving the adhesion of the composition to an aluminum 
substrate which is anodized (sulfuric acid or phosphoric acid) and then 
silicate treated, it is also possible to add a negative working diazo 
resin such as PF.sub.6 salt of the condensate of p-diazodiphenylamine and 
formaldehyde. 
The light-sensitive composition according to the present invention may 
further include a plasticizer according to need. Examples of such 
plasticizers include such phthalates as dimethyl phthalate, diethyl 
phthalate, dibutyl phthalate, dihexyl phthalate, dicyclohexyl phthalate 
and ditridecyl phthalate; such glycolates as dimethyl glycol phthalate, 
ethyl phthalylethyl glycolate and butyl phthalylbutyl glycolate; such 
phosphates as tricresyl phosphate and triphenyl phosphate; and such 
aliphatic dibasic acid esters as diisobutyl adipate, dioctyl adipate, 
dibutyl sebacate and dibutyl maleate. 
The light-sensitive layer or the photoresist layer may be prepared by first 
dissolving the aforementioned various components of the light-sensitive 
composition of the present invention and then coating the resultant 
solution on a proper substrate according in a conventional manner. In this 
connection, the preferred ratio between the components of the composition 
is as follows the amount of each component being expressed as parts by 
weight on the basis of 100 parts by weight of the polymerizable compound 
having ethylenically unsaturated bonds: 
______________________________________ 
Particularly 
Component Preferred Range 
Preferred Range 
______________________________________ 
Photopolymerization 
0.01 to 50 0.1 to 20 
Initiator 
Binder 0 to 1,000 0 to 500 
Heat Polymerization 
0 to 10 0 to 5 
Inhibitor 
Dye or Pigment 
0 to 50 0 to 20 
Plasticizer 0 to 200 0 to 50 
______________________________________ 
Examples of solvents which may be used to dissolve the light-sensitive 
composition of the present invention and to apply the composition onto the 
surface of the proper substrate include ethylene dichloride, 
cyclohexanone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, 
methyl acetate cellosolve, propylene glycol monomethyl ether, propylene 
glycol monomethyl ether acetate, monochlorobenzene, toluene, xylene, ethyl 
acetate and butyl acetate. These solvents may be used alone or in 
combination. 
When a PS plate is prepared from the composition of the invention, the 
amount of the composition to be coated on the surface of the substrate 
preferably ranges from 0.1 to 10.0 g/m.sup.2 generally expressed as solid 
content and particularly preferred amount thereof ranges from 0.5 to 5.0 
g/m.sup.2. 
The light-sensitive composition according to the present invention is quite 
adapted for the preparation of the light-sensitive layers of PS plates. 
Examples of the substrates suitable for the preparation of PS plates 
include hydrophilized aluminum plates such as silicate treated aluminum 
plates, anodized aluminum plates and silicate-electrodeposited aluminum 
plates; zinc plates; stainless steel plates; chromate treated copper 
plates; and hydrophilized plastic films or paper. 
As already mentioned above, the light-sensitive composition according to 
the present invention may also be used to form the light-sensitive layers 
of photoresists. In such case, there may be employed a variety of 
substrates such as copper plates or copper-plated plates, stainless steel 
plates and glass plates. Moreover, a protective layer may be formed on the 
light-sensitive layer coated on the substrate in order to eliminate the 
plymerization inhibitory effect of oxygen in air. Such protective layers 
may be obtained from a polymer excellent in oxygen shielding effect, such 
as polyvinyl alcohol and cellulose acetates. As to the method for applying 
such a protective layer, reference is made to, for instance, U.S. Pat. No. 
3,458,311 and J. P. KOKOKU No. 55-49729. 
In addition to the foregoing application, the photopolymerizable 
composition of the present invention may be used in various field and 
applications, for instance, in the conventional photopolymerization 
reactions and as a photoresist for use in making print circuit boards. 
From the foregoing detailed descriptions, it is clear that the 
photopolymerizable composition of the invention has a high sensitivity to 
actinic light. Therefore, the composition of the invention may be highly 
sensitive to light from a variety of light sources such as superhigh 
pressure, high pressure, medium pressure or low pressure mercury lamps, 
chemical lamp, carbon arc lamp, xenon lamp and metal halide lamps. 
The photopolymerizable composition of the present invention will hereunder 
be explained in more detail with reference to the following preparation 
examples and non-limitative working examples and the effects actually 
attained according to the composition of the invention will also be 
discussed in detail. 
Preparation Example: Preparation of Compound (13) 
There were mixed 6.5 g of 
2-methoxy-2-ethoxy-4-methyl-7-diethylamino-2H-benzopyran and 4 g of ethyl 
cyanoacetate and the mixture was heated at 150.degree. C. for 30 minutes. 
After allowing the reaction product to cool, it was passed through a 
column packed with silica gel utilizing 1:1 mixture (volume ratio) of 
hexane and ethyl acetate as the eluent to remove black colored impurities 
and then the product was recrystallized from 50 ml of ethanol. The 
crystals were filtered off and dried to recover 1.2 g of brown colored 
crystals having melting point of 146.degree. to 148.degree. C. 
Electron Spectrum (in tetrahydrofuran): .lambda.max=473 nm. 
.epsilon.=3.25.times.10.sup.4. 
IR Spectrum (KBr disk) cm.sup.-1 : 2200, 1683, 1583, 1512, 1420, 1350, 
1140. 
EXAMPLES 1 TO 5 
The surface of an aluminum plate of 0.03 mm thick was grained with a nylon 
brush and an aqueous solution of pumice stone having a particle size of 
400 mesh and then washed with water sufficiently. The aluminum plate was 
further etched by immersing it into 10% aqueous solution of sodium 
hydroxide at 60.degree. C. for 60 seconds, followed by water washing with 
running water, neutralizing and washing with 20% nitric acid and then 
washing with water. The aluminum plate was subjected to an electrolytic 
surface roughening treatment, in 1% aqueous solution of nitric acid, at 
the anode time electricity of 160 coulomb/dm.sup.2 using an alternating 
waved current of sign wave under V.sub.A =12.7 V. The surface roughness 
thereof was determined to be 0.6 microns (expressed as Ra). Subsequently, 
the plate was desmutted by immersing it into 30% aqueous solution of 
sulfuric acid at 55.degree. C. for 2 minutes and thereafter the aluminum 
plate was anodized in 20% aqueous solution of sulfuric acid at a current 
density of 2 A/dm.sup.2 so as to reduce the thickness thereof to 2.7 
g/m.sup.2. 
A light-sensitive layer was formed by applying, onto the aluminum plate 
thus treated, the light-sensitive liquid of the following composition so 
that the coated amount thereof was equal to 1.5 g/m.sup.2 (dry weight) and 
drying. 
______________________________________ 
Allyl Methacrylate/Methacrylic Acid 
3.2 g 
Copolymer (molar ratio = 80/20) 
Pentaerythritol Tetraacrylate 
1.7 g 
Photopolymerization Initiator 
5 mole % 
with re- 
spect to 
the 
monomer 
Methyl Ethyl Ketone 20 g 
Propylene Glycol Monomethyl- 
20 g 
ether Acetate 
Fluorine Nonionic Surfactant (manufacured 
0.03 g 
and sold by 3M Corporation under the trade 
name of FLUORAD FC-430) 
______________________________________ 
On the light-sensitive layer, an aqueous solution of 3% by weight of 
polyvinyl alcohol (dgree of saponification=86.5 to 89 mole %; degree of 
polymerization=1,000) was applied so that the dry weight thereof was 2 
g/m.sup.2 and then was dried at 100.degree. C. for 2 minutes. 
Using a vacuum printing frame equipment, the light-sensitive layer was 
exposed to light from a light source of PS LIGHT S type manufactured and 
sold by Fuji Photo Film Co., Ltd. (metal halide lamp; 2 KW) from a 
distance of 1 m for 1 minute. The metal halide lamp has a bright line 
spectrum between 300 to 450 nm. The sensitivity was determined by using a 
continuous step wedges having an LTF density difference of 0.15. In 
addition, the development of the exposed light-sensitive layer was 
effected by immersing it into the following developer at 25.degree. C. for 
1 minute. 
______________________________________ 
Benzyl Alcohol 10 g 
Monoethanolamine 1 g 
Triethanolamine 10 g 
Sodium Isopropylnaphthalene 
2 g 
Sulfonate 
Pure Water 1000 ml 
______________________________________ 
The results of the sensitivity measurement observed on the 
photopolymerizable compositions, each of which contained a different 
photopolymerization initiator, are summarized in Table I below. 
TABLE I 
______________________________________ 
Number of 
clear steps of 
Ex. gray scale 
No. Photopolymerization 
step wedge 
______________________________________ 
1 Compound No. 12 
5.0 
2 Compound No. 13 
3.0 
3 Compound No. 14 
2.5 
4 Compound No. 15 
3.0 
5 Compound No. 16 
5.0 
______________________________________