Printing plate

A printing plate formed of a substrate and laminated thereon in the following order a primer layer and a photosensitive layer containing a quinonediazide compound and a silicone rubber layer, wherein the primer layer contains 0.1 to 25% by weight of a quinonediazide group. The printing plate of the present invention is excellent in dot reproduction, hardly causes cracking in the photosensitive layer, and has a wide latitutde in production.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a printing plate which enables printing without 
use of dampening water. 
2. Description of the Prior Art 
Heretofore, a number of proposals have been made on printing plates 
comprising a silicone rubber layer as an ink repellent layer and thus 
enabling printing without use of water. For example, U.S. Pat. No. 
4,358,522 discloses a printing plate having a silicone rubber layer 
provided on a photosolubilizable photosensitive layer comprising a 
quinonediazide compound backed with an aluminium plate through a primer 
layer. Further, U.S. Pat. No. 4,342,820 discloses a printing plate having 
a silicone rubber layer provided on a photosensitive layer comprising a 
product of partial esterification of 
1,2-naphthoquinone-2-diazide-5-sulfonyl chloride with a phenolic novolak 
resin crosslinked with a polyfunctional isocyanate compound. In such 
printing plates, it is a common practice to provide a primer layer between 
a substrate and a photosensitive layer for the purpose of preventing 
halation, ensuring the adhesion between the substrate and the 
photosensitive layer, binding the substrate through incorporation of a 
primer layer containing fine particles or the like. 
Although the conventional printing plates having the above-mentioned 
structures are useful, they have the following problems. 
(1) An increase in the thickness of the photosensitive layer leads to a 
poor developability. On the other hand, as the thickness is decreased, the 
light absorbance of the photosensitive layer is decreased, which brings 
about transmission of an exposure light through the photosensitive layer 
and reflection of the transmitted light on the substrate or primer layer 
in the case of longer imagewise exposure time, which brings about halation 
and finally leads to a poor dot reproduction. The addition of a light 
absorber such as an ultraviolet absorber to the primer layer or 
photosensitive layer is considered to be effective to solve this problem. 
However, such an expedient leads to no significant halation preventing 
effect, because it is difficult to match the absorption wavelength of the 
absorber with that of a quinonediazide group contained in the 
photosensitive layer. 
(2) Since known quinonediazide compounds which have been used as the 
photosensitive material have a relatively low molecular weight, pinholes 
and, non-uniform coating, etc. tend to occur in the photosensitive layer 
when a photosensitive layer has a small thickness, which gives an adverse 
effect on the printing. 
(3) The stabilization of the adhesion between the photosensitive layer and 
the silicone rubber layer is of importance in respect of qualities of the 
printing plate such as developability and scratch resistance of printing 
plates. However, since the adhesion between the photosensitive layer and 
the silicone rubber layer tends to be influenced by external conditions, 
qualities of the printing plate also tend to undergo changes. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a printing plate which is 
excellent in dot reproduction as well as in image reproduction. 
Another object of the present invention is to provide a printing plate 
having a photosensitive layer which has a high flexibility and hardly 
causes cracking etc. 
Still another object of the present invention is to provide a printing 
plate having a photosensitive layer which has an improved film-forming 
properties, hardly causes pinholes and is wide in latitude in production. 
In accordance with the present invention, there is provided a printing 
plate comprising a substrate and superimposed on said substrate in the 
following order a primer layer, a photosensitive layer containing a 
quinonediazide compound and a silicone rubber layer, wherein said primer 
layer contains 0.01 to 25% by weight of a quinonediazide group. In a 
preferred embodiment of the present invention, said photosensitive layer 
further contains an organic compound which has a boiling point of 
150.degree. C. or above and at least one bond selected from an ether bond 
and an ester bond in its molecule and a molecular weight of 85 to 1000. 
The term "printing plate" as used in the present invention is intended to 
mean a printing plate before development, i.e. master or unprocessed 
plate, as well as a printing plate after development. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The substrate used in the present invention is not particularly limited and 
may be any one which is used in conventional printing plates. Examples of 
the substrate include plates of metals such as aluminium, iron and zinc, 
films of organic polymers such as polyester, polyamide and polyolefin, and 
composite materials prepared therefrom. 
The quinonediazide group contained in the primer layer used in the present 
invention serves as a light absorber and exhibits a halation preventing 
effect. When the content of the quinonediazide group in the primer layer 
is too low, no satisfactory halation preventing effect can be attained, 
while an excessively high content of the quinonediazide group is 
disadvantageous from the economical point of view. Therefore, the content 
of the quinonediazide group is preferably 0.01 to 25% by weight, more 
preferably 0.05 to 10% by weight, most preferably 0.1 to 5% by weight. 
Examples of the quinonediazide group include substituted or unsubstituted 
1,2-benzoquinonediazide group, 1,2-naphthoquinonediazide group and 
2,1-naphthoquinonediazide group. Among them 1,2- or 
2,1-naphthoquinonediazide group is preferable from the standpoint of 
stability. 
Compounds containing a quinonediazide group include compounds in which 
1,2-benzoquinonediazide group is bonded through a carbon atom in the 
4-position or 5-position and compounds in which 1,2-(or 
2,1-)naphthoquinonediazide group is bonded through a carbon atom in the 
4-position or 5-position. Among them preferred compounds include 
naphthoquinonediazidecarboxylic acid, naphthoquinonediazidesulfonyl halide 
and a product of an esterificaiton of a naphthoquinonediazidesulfonic acid 
with a phenolic hydroxyl group. A more preferred compound includes a 
product of an esterification of 1,2-(or 2,1-)naphthoquinonediazide-4-(or 
5-)sulfonic acid with the following compound having a phenolic hydroxyl 
group. 
Examples of the compound having a phenolic hydroxyl group include 
substituted or unsubstituted phenol, cresol, dihydroxybenzene, pyrogallol, 
naphthol, bisphenol A, dihydroxynaphthalene, hydroxystyrene polymer or 
copolymer, .alpha.-methylhydroxystyrene polymer or copolymer, phenolic 
resin, (e.g., phenol/formaldehyde addition condensate, cresol/formaldehyde 
addition condensate, phenol/acetone addition condensate, cresol/acetone 
addition condensate, pyrogallol/acetone addition condensate or cardanol/ 
formaldehyde addition condensate) and polyhydroxyphenyl. 
Although the above-mentioned compounds may be used alone as the primer 
layer, it is preferred that the primer layer contain a polymer having a 
crosslinked structure from the standpoint of resistance to a solvent such 
as a developer as well as adhesion to the substrate. Further, it is 
preferred that the content of an acetone-soluble component in the primer 
layer is 20% by weight or less. The term "acetone-soluble component" as 
used herein is intended to mean a component which dissolves in acetone 
when the material constituting the primer layer is stirred in the presence 
of a large excess of acetone at 25.degree. C. for 6 hr. 
It is preferred that the polymer used for the primer layer is selected from 
those which can form a crosslinked structure among addition polymers 
(e.g., polyacrylic ester derivatives, polymethacrylic ester derivatives, 
polystyrene derivatives, polydiene derivatives, polyethylene derivatives, 
polyvinylidene derivatives, polyvinyl alcohol derivatives or their 
copolymes), polycondensates (e.g., polyesters or polyimides), addition 
condensates (such as novolak resin or resol resin), amino resins (such as 
melamine resin or urea resin), polyethers, polythiols, polyurethanes, 
epoxy resins, alkyd resins, etc. It is preferred in this connection that 
the primer layer contain 30% by weight or more of a polymer having a glass 
transition point of 0.degree. C. or below from the standpoint of the 
surface strength of the resulting printing plate. Preferred polymers which 
satisfy the above-mentioned glass transition point requirement include 
polyurethanes, polyesters, polyacrylic ester derivatives, polymethacrylic 
ester derivatives and polyvinyl alcohol derivatives, and they may be used 
alone or in the form of any mixture thereof. The method of crosslinking 
these polymers is not particularly limited and may be those which are 
conventionally employed. Particularly, it is preferred that the polymer is 
crosslinked through at least one compound selected from the group 
consisting of polyepoxy compounds, polyisocyanate compounds and amino 
resins. 
Examples of the polyepoxy compound include polyethylene glycol diglycidyl 
ethers, polypropylene glycol diglycidyl ethers, bisphenol A diglycidyl 
ether and trimethylolpropane diglycidyl ether. Examples of the 
polyisocyanate compound include hexamethylene diisocyanate, isophorone 
diisocyanate, p-phenylene diisocyanate, 2,4-or 2,6-tolylene diisocyanate, 
4,4'-diphenylmethane diisocyanate, polymethylenepolyphenyl isocyanate or 
adducts thereof. Examples of the amino resin include urea resin and 
melamine resin. 
In order to improve the adaptability to visual inspection of the plate, a 
white pigment such as titanium oxide or calcium carbonate or yellow 
pigment may be added to the above-mentioned primer composition. 
Although the thickness of the primer layer is not particularly limited, too 
large a thickness is disadvantageous from the standpoint of coatability as 
well as economy while too small a thickness is also disadvantageous from 
the standpoint of coatability. Therefore, the thickness of the primer 
layer is preferably in the range of 0.5 .mu.m to 100 .mu.m, more 
preferably in the range of 1 .mu.m to 30 .mu.m. A resin layer composed 
mainly of a polymer may also be provided between the specific primer layer 
according to the present invention and the substrate. 
Examples of the method of incorporating a quinonediazide group in a primer 
layer include the following methods: 
(1) A compound having a quinonediazide group is added to a primer layer 
composition, and the composition is then applied on a substrate to form a 
primer layer. 
(2) A rubber component is added to a primer layer composition, and the 
composition is applied on a substrate to form a primer layer. A 
composition comprising a low-molecular compound having a quinonediazide 
group is applied on the primer layer, thereby causing the compound having 
a quinonediazide group to penetrate into the primer layer. Subsequently, a 
photosensitive layer composition is applied thereon to form a 
photosensitive layer. 
(3) A rubber component is added to a primer layer composition, and the 
composition is applied on a substrate to form a primer layer. A 
photosensitive layer composition containing a high molecular compound 
having a quinonediazide group as well as a low-molecular compound having a 
quinonediazide group is then applied on the primer layer, thereby causing 
the low-molecular compound having a quinonediazide group to penetrate and 
migrate into the primer layer. 
(4) A rubber component is added to a primer layer composition, and the 
composition is applied on a substrate to form a primer layer. A 
photosensitive layer composition containing a plurality of quinonediazide 
compounds which are different from each other in percentage esterification 
is then applied on the primer layer, thereby causing the quinonediazide 
compound having a predetermined percentage esterification to penetrate and 
migrate into the primer layer. 
With respect to the above-mentioned methods (2), (3) and (4), the content 
of the rubber component in the primer layer is preferably 30% by weight or 
more, and the materials for the rubber component are preferably those 
having an average glass transition point of 0.degree. C. or below. 
Examples of the rubber component include natural rubber, polybutadiene, 
styrene-butadiene copolymer, nitrile rubber, acrylic rubber, polyurethane, 
polyester elastomer, polyamide elastomer, polyetheresteramide elastomer 
and polyvinyl butyral. 
Examples of the quinonediazide compound contained in the photosensitive 
layer include the above-mentioned compounds contained in the primer layer. 
However, it is preferred from the standpoint of image forming properties 
that 50% by weight or more of the quinonediazide compounds have a 
molecular weight of 500 or more. Preferred compounds having a molecular 
weight of 500 or more include products of esterification of 
1,2-naphtho-quinonediazide-4(or 5)-sulfonic acid with the following 
compounds having a phenolic hydroxyl group, and they may be used alone or 
in the form of any mixture thereof. 
(1) Phenolic resins, e.g., phenol/formaldehyde addition condensate, 
cresol/formaldehyde addition condensate, phenol/acetone addition 
condensate, cresol/acetone addition condensate, pyrogallol/acetone 
addition condensate, cardanol/formaldehyde addition condensate or 
cardanol/acetone addition condensate. 
(2) Substituted or unsubstituted hydroxystyrene polymers or copolymers and 
substituted or unsubstituted .alpha.-methylhydroxystyrene polymers or 
copolymers. 
(3) Crosslinked products as disclosed in U.S. Pat. No. 4,342,820, e.g., 
those obtained by crosslinking the compounds as mentioned in the above 
items (1) and (2) with a polyisocyanate compound, a polyepoxy compound or 
the like. 
The photosensitive layer may also contain other polymers and plasticizers 
for the purpose of improving film-forming properties and adhesion. 
Although the content of the quinonediazide group in the photosensitive 
layer is not particularly limited, it is preferably more than 5% by 
weight, more preferably more than 10% by weight. Further, the content of 
an acetonesoluble component in the photosensitive layer is preferably 20% 
by weight or more from the standpoint of developability. 
The composition for forming the above-mentioned photosensitive layer can be 
prepared by dissolving the components in a suitable organic solvent, e.g., 
dioxane, tetrahydrofuran, cellosolve, cellosolve acetate or 
dimethylformamide. 
Although the thickness of the photosensitive layer is not particularly 
limited, too large a thickness brings about lowering in developability 
while too small a thickness often brings about pinholes. Therefore, the 
thickness of the photosensitive layer is preferably 0.3 to 10 g/m.sup.2, 
more preferably 0.5 to 5 g/m.sup.2. 
The organic compounds having at least one bond selected from an ether bond 
and an ester bond in its molecule which may be used in the present 
invention are those having a high compatibility with the quinonediazide 
compound and capable of plasticizing the photosensitive layer. 
Preferred examples of such organic compounds are represented by the 
following general formulae (I) and (ii): 
##STR1## 
EQU R.sub.1 O--(CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --O).sub.n R.sub.2 
(II) 
wherein R.sub.1 and R.sub.2 each independently stand for a hydrogen atom, 
an alkyl group having 1 to 10 carbon atoms or an acyl group having 2 to 5 
carbon atoms; R.sub.3 a hydrogen atom or a methyl group; and n an integer 
of 2 to 15, and they include diethylene glycol, triethylene glycol, 
polyethylene glycol, dipropylene glycol, tripropylene glycol, 
polypropylene glycol, diethylene glycol monomethyl ether, diethylene 
glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene 
glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene 
glycol monoethyl ether, triethylene glycol monobutyl ether, diethylene 
glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol 
dibutyl ether, triethylene glycol dimethyl ether, tetraethylene glycol 
dimethyl ether, polyethylene glycol dimethyl ether, diethylene glycol 
monomethyl ether acetate, diethylene glycol monoethyl ether acetate, 
diethylene glycol monobutyl ether acetate, 1,4-butanediol monohexyl ether 
and 1,4-butanediol dibutyl ether. 
Examples of other organic compounds having an ether bond include ethylene 
glycol monohexyl ether and ethylene glycol dibutyl ether. 
Examples of other organic compounds having an ester bond include ethylene 
glycol diacetate, dimethyl oxalate, diethyl oxalate, dimethyl malonate, 
diethyl malonate, dimethyl succinate, dimethyl adipate, diethyl adipate, 
dimethyl maleate, diethyl maleate, dimethyl fumarate, diethyl fumarate and 
propylene carbonate. 
More preferred organic compounds include polyethylene glycol, polypropylene 
glycol, diethyl glycol dimethyl ether, diethylene glycol diethyl ether, 
triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 
diethylene glycol monoethyl ether acetate, dimethyl succinate, dimethyl 
adipate and propylene carbonate. 
The molecular weight of the organic compound having at least one bond 
selected from an ether bond and an ester bond in its molecule is 
preferably 85 to 1000, more preferably 90 to 800, and the boiling point 
thereof is preferably 150.degree. C. or above. A molecular weight of less 
than 90 and a boiling point of lower than 150.degree. C. are unfavorable 
because the effect attained by its addition is small. On the other hand, a 
molecular weight exceeding 1000 is also unfavorable because the 
compatibility with the quinonediazide compound is lowered. 
The content of the organic compound having at least one bond selected from 
an ether bond and an ester bond is 0.5 to 300 parts by weight, preferably 
0.5 to 150 parts by weight per 100 parts by weight on a dry basis of the 
photosensitive layer. When the content is too low, the effect attained by 
its addition is small, while when it is too large the photosensitive 
characteristics of the resulting printing plate is poor. Therefore, it is 
preferred that the content of the organic compound be in the 
above-mentioned range. 
In producing a printing plate, the above-mentioned organic compound is 
added in an amount of 1 to 2,000 parts by weight based on 100 parts by 
weight of the quinonediazide compound. It is noted in this connection that 
the whole amount of the organic compound which has been added is not 
necessarily required to be left in the photosensitive layer, and 
satisfactory effect can be attained when the above-mentioned amount of the 
organic compound is left in the photosensitive layer. 
Excess amounts of the organic compound can be readily removed by 
evapolation. Usually they can be evapolated by heating. 
The silicone rubber layer according to the present invention is composed 
mainly of a silicone rubber obtained by crosslinking a linear 
organopolysiloxane having the following repeating unit: 
##STR2## 
wherein n stands for an integer of 2 or more and R.sup.1 and R.sup.2 each 
independently stand for a hydrogen atom, an unsubstituted or substituted 
(with, e.g., a halogen atom or a cyano or amino group) hydrocarbon group 
having 1 to 10 carbon atoms. A preferred hydrocarbon group is an alkyl, 
alkenyl or phenyl group, and 60% or more of the total of R.sup.1 and 
R.sup.2 are preferably methyl groups from the standpoint of easiness of 
production. In the present invention, the crosslinking of the 
organosiloxane to a silicone rubber can be attained by the condensation 
reaction of an organosiloxane having 1.2 or more silanol groups on the 
average per molecule with a crosslinking agent comprising a silane or 
siloxane in which two or more, preferably three or more hydrolyzable 
groups, e.g., acyloxy, alkoxy, ketoximate, amino or aminoxy group, halogen 
atom or alkenyloxy group, are bonded to the silicon atom. 
Examples of the crosslinking agent having an acyloxy group include 
vinyltriacetoxysilane, methyltriacetoxysilane, ethyltriacetoxysilane and 
tetraacetoxysilane. 
Examples of the crosslinking agent having an alkoxy group include 
tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, 
methyltriethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane. 
Examples of the crosslinking agent having a ketoximate group include 
methyltris(dimethylketoxime)silane, vinyltris(dimethylketoxime)silane, 
methyltris(methylethylketoxime)silane, 
vinyltris(methylethylketoxime)silane, tetrakis(dimethylketoxime)silane and 
tetrakis(methylethylketoxime)silane. 
Examples of the crosslinking agent having an alkenyloxy group include 
methyltriisopropenoxysilane and vinyltriisopropenoxysilane. 
Examples of the crosslinking agent having an amino group include 
methyltris(N,N-dimethylamino)silane, methyltris(N,N-diethylamino)silane, 
vinyltris(N,N-dimethylamino)silane, vinyltris(N,N-diethylamino)silane, 
1,3,5-tris(N,N-diethylamino)-1,3,5,7,7-pentamethyltetracyclosiloxane, 
dimethylbis(N-methylacetamide)silane, dimethylbis(N-ethylacetamide)silane, 
methyltris(N-methylacetamide)silane, methyltris(N-ethylacetamide)silane, 
vinyltris(N-methylacetamide)silane, vinyltris (N-ethylacetamide)silane, 
1,3-bis(N-methylacetamide)-1,1,3,3-tetramethyldisiloxane, 
1,1,3,3-tetrakis(N-methylacetamide)-1,3-dimethyldisiloxane, a copolymer of 
methyl(N-methylacetamide)siloxane with dimethylsiloxane and a copolymer of 
methyl(N-ethylacetamide)siloxane with dimethylsiloxane. 
Examples of the crosslinking agent having an aminoxy group include 
1,5-bis(N,N-dimethylaminoxy)- 1,3,3,5,7,7-hexamethyltetracyclosiloxane, 
1,5-bis(N,N-diethylaminoxy)-1,3,3,5,7,7-hexamethyltetracyclosiloxane, 
1,3,5-tris(N,N-dimethylaminoxy)-1,3,5,7,7-pentamethyltetracyclosiloxane, 
1,3,5-tris(N,N-diethylaminoxy)-1,3,5,7,7-pentamethyltetracyclosiloxane, a 
copolymer of methyl(N,N-dimethylaminoxy)siloxane with dimethylsiloxane and 
a copolymer of methyl(N,N-diethylaminoxy)siloxane with dimethylsiloxane. 
Examples of the crosslinking agent having a halogen atom include 
tetrachlorosilane, methyltrichlorosilane, dimethyldichlorosilane and 
vinyltrichlorosilane. 
The condensates of hydrolyzates of the above-mentioned compounds may also 
used as the crosslinking agent. 
The crosslinking may be conducted under such a condition that the number of 
the silanol groups of the organopolysiloxane is substantially the same as 
that of the hydrolyzable groups. Alternatively, the crosslinking may be 
conducted by hydrolysis followed by condensation under such a condition 
that the number of the hydrolyzable groups is larger than that of the 
silanol groups. It is preferred that the silicone rubber has the following 
composition before curing: 
(a) an organopolysiloxane having 1.2 or more silanol groups on the average 
per molecule . . . 100 parts by weight, and 
(b) a crosslinking agent having a hydrolyzable group . . . 0.5 to 20 parts 
by weight. 
Additives such as a solvent for coating, a reinforcing filler, a catalyst 
for curing and a known tackifier may also be added to the composition. 
Although the thickness of the silicone rubber layer is not particularly 
limited, too large a thickness tends to bring about lowering in 
developability while too small a thickness brings about lowering in 
strength of the plate surface. Therefore, the thickness of the silicone 
rubber layer is preferably 0.25 to 50 .mu.m, more preferably 0.5 to 10 
.mu.m. An adhesive layer may be provided between the silicone rubber layer 
and the photosensitive layer with, e.g., a silane coupling agent or a 
titanium coupling agent for the purpose of ensuring adhesion. 
The printing plate according to the present invention can be prepared by 
e.g., the following method. First, a primer layer forming composition is 
applied on a substrate with an ordinary coater such as a reverse roll 
coater, an air-knife coater or a Mayer bar coater, or a rotary applicator 
such as a whirler, followed by drying and, if required, heat curing, 
thereby forming a primer layer. If necessary, a composition for causing 
the migration of a quinonediazide group into the primer layer is applied 
and then dried. Subsequently, a photosensitive layer forming composition 
is applied thereon and dried and, if required, heat cured, thereby forming 
a photosensitive layer. If necessary, an adhesive layer is provided on the 
photosensitive layer, and an uncured composition of a silicone rubber is 
applied thereon and heat-treated for several minutes to form a silicone 
rubber layer. If necessary, the silicone rubber layer thus formed may be 
covered with a protective film comprising a polymer such as polyester or 
polyolefin with a laminator or the like. 
The printing plate of the present invention thus prepared is exposed to an 
actinic light, e.g., through a negative film which has been closely 
contacted to the plate in vacuo. The light source used in this exposure 
step is one capable of generating a sufficient amount of ultraviolet rays, 
and examples of such a light source include a mercury lamp, a carbon arc 
lamp, a xenone lamp, a metal halide lamp, a tungsten lamp and a 
fluorescent lamp. 
Thereafter, the exposed plate surface is rubbed with a developing pad 
containing a developer to remove at least the silicone rubber layer of the 
exposed portion, thereby obtaining a printing plate in which the surface 
of the photosensitive layer or the primer layer serves as an ink 
receivable image area. 
Suitable developers which may be used in the production of the printing 
plate of the present invention are those as disclosed in U.S. Pat. No. 
4,496,647 and include a developer containing a basic substance such as an 
amine and a developer comprising an aliphatic hydrocarbon, an aromatic 
hydrocarbon, water or a halogenated hydrocarbon and the following polar 
solvent added thereto: 
(i) alcohols, e.g., methanol and ethanol, 
(ii) ethers, e.g., dioxane, 
(iii) cellosolve, e.g., ethyl cellosolve, methyl cellosolve and butyl 
cellosolve, 
(iv) carbitol, e.g., methyl carbitol, ethyl carbitol and butyl carbitol, or 
(v) esters, e.g., ethyl acetate, ethyl cellosolve acetate, methyl 
cellosolve acetate and carbitol acetate. 
A printed matter having an excellent image reproduction can be obtained by 
mounting the printing plate thus obtained on an offset printing machine 
and conducting printing without use of damping water. 
EXAMPLES 
The present invention will now be described in more detail with reference 
to the following examples. In the examples, the contents in terms of % by 
weight of a quinonediazide group in the primer layer and the 
photosensitive layer of an unprocessed plate were calculated from an 
absorbance at a light wave length of 400 nm which were determined by 
reflection ultraviolet spectrometry (using a Hitachi 323 
spectrophotometer). In this connection, the effective detection range of 
the quinonediazide group was 0.01% by weight or more.

EXAMPLE 1 
The following primer composition was applied on an aluminium plate and 
heated at 120.degree. C. for 4 min to form a primer layer (thickness: 1 
.mu.m): 
__________________________________________________________________________ 
(1) 
a phenolic novolak resin having a number-average 
degree of polymerization of 5.1 
90 parts by weight 
(2) 
a product of an esterification of the resin as 
mentioned in the above item (1) with 1,2-naphtho- 
quinonediazide-5-sulfonyl chloride (percentage 
esterification: 25%) 
10 parts by weight 
(3) 
dibutyltin diacetate 0.5 
part by weight 
(4) 
4,4'-diphenylmethane diisocyanate 
20 parts by weight 
(5) 
tetrahydrofuran 990 
parts by weight 
__________________________________________________________________________ 
Thereafter, the following photosensitive layer composition was applied on 
the primer layer, heated at 120.degree. C. for 1 min and dried to form a 
photosensitive layer (thickness: 1.5 g/m.sup.2) 
__________________________________________________________________________ 
(1) 
a product of an esterification of a phenolic 
novolak resin having a number-average degree of 
polymerization of 4.6 with 1,2-naphthoquinonediazide- 
5-sulfonylchloride (percentage esterification: 40%) 
20 parts by weight 
(2) 
tetrahydrofuran 80 parts by weight 
__________________________________________________________________________ 
The following adhesive layer composition was then applied on the 
photosensitive layer, heated at 100.degree. C. for 1 min and dried to form 
an adhesive layer (thickness: 0.5 .mu.m): 
______________________________________ 
(1) .gamma.-aminopropyltrimethoxysilane 
1 part by weight 
(2) n-heptane 990 parts by weight 
______________________________________ 
Subsequently, the following silicone rubber composition was applied on the 
adhesive layer and heated at 120.degree. C. to dry and cure the resulting 
coating, thereby forming a silicone rubber layer (thickness: 2.mu.m): 
__________________________________________________________________________ 
(1) 
.alpha.,.omega.-dihydroxypolydimethylsiloxane (number-average 
molecular weight: 20,000) 
100 
parts by weight 
(2) 
vinyltris(methylethylketoxime)silane 
8 parts by weight 
(3) 
dibutyltin diacetate 0.2 
parts by weight 
(4) 
n-heptane 800 
parts by weight 
__________________________________________________________________________ 
Thereafter, a 10 .mu.m-thick polypropylene film ("Torayfan," a product of 
Toray Industries, Inc.) was laminated as a cover film on the silicone 
rubber layer. Thus, there was obtained a unprocessed printing plate. 
The cover film of the unprocessed printing plate thus obtained was peeled 
off. The silicone rubber layer, the adhesive layer and the photosensitive 
layer were then removed using a nonwoven fabric ("Haize Gauge," a product 
of Asahi Chemical Industry Ltd.) with the plate immersed in methyl ethyl 
ketone at 25.degree. C., and the content of the quinonediazide group in 
the primer layer was determined and found to be 2.1 % by weight. 
The unprocessed printing plate obtained above was exposed to an actinic 
light ray by means of a metal halide lamp ("Eyedolphin 2000," a product of 
Iwasaki Electric Co., Ltd.) for 60 sec at a distance of 1 m through a 
negative film having a dot image of 150 lines/in. which had been closely 
contacted to the plate in vacuo. The plate surface after exposure was 
immersed in a treating solution [ethanol/aliphatic hydrocarbon solvent 
("Isopar E," a product of Exxon Corp.); 50/50 in weight ratio]. By softly 
rubbing the surface of the plate with a developing pad, the exposed areas 
were removed together with the photosensitive layer, thereby causing the 
primer layer to be exposed. On the other hand, the silicon rubber layer in 
the unexposed areas remained unremoved in a firmly bonded state, thereby 
exactly reproducing the image borne on the negative film. 
The printing plate thus obtained was attached to an offset printing machine 
("Komori Sprint 2 Color"), and printing was conducted with an ink 
("Aqualess PLT Blue," a product of Toyo Ink Mfg. Co., Ltd.) without use of 
dampening water to obtain a printed matter having an extremely excellent 
image which reproduced 3% to 95% of dots of 150 lines/in. 
COMATIVE EXAMPLE 1 
An unprocessed printing plate was prepared in substantially the same manner 
as in EXAMPLE 1, except that the following primer composition was used 
instead of that used in EXAMPLE 1. 
__________________________________________________________________________ 
(1) 
a phenolic novolak resin having a number-average 
degree of polymerization of 5.1 
100 
parts by weight 
(2) 
dibutyltin diacetate 0.5 
part by weight 
(3) 
4,4'-diphenylmethane diisocyanate 
20 parts by weight 
(4) 
tetrahydrofuran 900 
parts by weight 
__________________________________________________________________________ 
The content of the quinonediazide group in the primer layer of the 
resulting unprocessed printing plate was determined in the same manner as 
in EXAMPLE 1 and found to be below the effective detection range, i.e., no 
quinonediazide group was detected in the determination. 
The unprocessed printing plate was subjected to exposure and development in 
the same manner as in EXAMPLE 1, thereby obtaining a printing plate in 
which the primer layer is exposed in the light exposed areas. Using the 
printing plate thus obtained, printing was conducted in the same manner as 
in EXAMPLE 1. The resulting printed matter had an image which reproduced 
only 3% to 90% of dots of 150 lines/in. and was poor in the reproduction 
of shadow portions. 
EXAMPLE 2 
The following primer composition was applied on an aluminium plate and 
heated at 210.degree. C. for 2 min to form a primer layer (thickness: 3 
.mu.m): 
__________________________________________________________________________ 
(1) 
a polyurethane resin ("Sanprene LQ-T1331," a product 
of Sanyo Chemical Industry Ltd.) 
50 parts by weight 
(2) 
a blocked isocyanate ("Takenate B830," a product 
of Takeda Chemical Industries, Ltd.) 
20 parts by weight 
(3) 
an epoxy/phenol/urea resin ("SJ9372," a product of 
Kansai Paint Co., Ltd.) 8 parts by weight 
(4) 
N,N--dimethylformamide 725 
parts by weight 
__________________________________________________________________________ 
Thereafter, the following composition was applied on the primer layer so as 
to form a coating having a thickness of 10 .mu.m in a wet state and heated 
at 100.degree. C. for 30 sec, thereby causing the migration of the 
quinoediazide compound into the primer layer: 
__________________________________________________________________________ 
(1) 
a product of an esterification of a bisphenol with 
1,2-naphthoquinonediazide-5-sulfonylchloride 
(percentage esterification: 50%) 
1 parts by weight 
(2) 
tetrahydrofuran 99 parts by weight 
__________________________________________________________________________ 
The following photosensitive layer composition was then applied thereon, 
heated at 120.degree. C. for 1 min and dried to form a photosensitive 
layer (thickness: 1.5 g/m.sup.2): 
__________________________________________________________________________ 
(1) 
a product of an esterification of poly(p-hydroxy- 
styrene) having a number-average molecular weight 
of 11,000 with 1,2-naphthoquinonediazide-5- 
sulfonylchloride (percentage esterification: 40%) 
10 parts by weight 
(2) 
ethyl cellosolve 90 parts by weight 
__________________________________________________________________________ 
Thereafter, an adhesive layer, a silicone rubber layes and a cover film 
were provided on the photosensitive layer in the same manner as in EXAMPLE 
1, there by obtaining an unprocessed printing plate. 
The content of the quinonediazide group in the primer layer of the 
resulting unprocessed printing plate was determined in the same manner as 
in EXAMPLE 1 and found to be 1.2% by weight. 
The unprocessed printing plate thus obtained was subjected to exposure and 
development in the same manner as in EXAMPLE 1, thereby obtaining a 
printing plate in which the primer layer was exposed in the light exposed 
areas. Using the printing plate thus obtained, printing was conducted in 
the same manner as in EXAMPLE 1. The resulting printed matter had an 
extremely excellent image which reproduced 3% to 95% of dots of 150 
lines/in. 
COMATIVE EXAMPLE 2 
The same primer layer as that formed in COMATIVE EXAMPLE 1 was provided 
on an aluminium plate. A photosensitive layer, an adhesive layer and a 
silicone rubber layer were successively laminated on the primer layer in 
the same manner as in EXAMPLE 2, thereby obtaining an unprocessed printing 
plate. 
The content of the quinonediazide group in the primer layer of the 
unprocessed printing plate thus obtained was determined in the same manner 
as in EXAMPLE 1 and found to be below the effective detection range, i.e., 
no quinonediazide group was detected in the determination. 
The unprocessed printing plate was subjected to exposure and development in 
the same manner as in EXAMPLE 1, thereby obtaining a printing plate of 
which the primer layer was exposed. Using the printing plate thus 
obtained, printing was conducted in the same manner as in EXAMPLE 1. The 
printed matter thus obtained had an image which reproduced only 3% to 90% 
of dots of 150 lines/in. and was poor in the reproduction of shadow 
portions. 
EXAMPLE 3 
The following primer composition was applied on an aluminium plate and 
heated at 210.degree. C. for 2 min to form a primer layer (thickness: 7 
.mu.m): 
__________________________________________________________________________ 
(1) 
a linear polyester ("Vylon 300," a product of 
Toyobo Co., Ltd.) 85 parts by weight 
(2) 
a blocked diisocyanate ("Takenate B830," a product 
of Takeda Chemical Industries, Ltd.) 
15 parts by weight 
(3) 
N,N--dimethylformamide 800 
parts by weight 
__________________________________________________________________________ 
Thereafter, the following photosensitive layer composition was applied on 
the primer layer, heated at 120.degree. C. for 1 min and dried to form a 
photosensitive layer (thickness: 2 g/m.sup.2): 
__________________________________________________________________________ 
(1) 
a product of an esterification of poly(p-hydro- 
xystyrene) having a number-average molecular 
weight of 11,000 with 1,2-naphthoquinonediazide-5- 
sulfonylchloride (percentage esterification: 25%) 
80 parts by weight 
(2) 
a product of an esterification of a phenolic 
novolak resin having a number-average degree of 
polymerization of 5.1 with 1,2-naphthoquinonediazide- 
5-sulfonyl chloride (percentage esterification: 25%) 
20 parts by weight 
(3) 
4,4'-diphenylmethane diisocyanate 
30 parts by weight 
(4) 
dibutyltin diacetate 0.2 
part by weight 
(5) 
tetrahydrofuran 500 
parts by weight 
__________________________________________________________________________ 
The following silicone rubber composition was applied on the photosensitive 
layer and heated at 120.degree. C. for 3.5 min to dry and cure the 
resulting coating, thereby forming a silicone rubber layer (thicknes: 2 
.mu.m): 
__________________________________________________________________________ 
(1) 
.alpha.,.omega.-dihydroxypolydimethylsiloxane (number-average 
molecular weight: 20,000) 
100 
parts by weight 
(2) 
vinyltris(methylethylketoxime)silane 
8 parts by weight 
(3) 
dibutyltin diacetate 0.2 
part by weight 
(4) 
.gamma.-aminopropyltrimethoxysilane 
0.5 
part by weight 
(5) 
n-heptane 800 
parts by weight 
__________________________________________________________________________ 
A cover film was laminated on the silicone rubber layer in the same manner 
as in EXAMPLE 1, thereby obtaining an unprocessed printing plate. 
The contents of the quinonediazide group in the photosensitive layer and 
the primer layer of the unprocessed printing plate thus obtained were 18% 
by weight and 0.5% by weight, respectively, and the contents of the 
acetone-soluble component in the photosensitive layer and the primer layer 
were 28% by weight and 16% by weight, respectively. 
The whole surface of the unprocessed printing plate obtained above was 
exposed to an actinic light having an intensisity of 11 mW/cm.sup.2 with 
an UV meter (light measure type; "UV-402A," manufactured by Ohku 
Seisakusho) by means of a metal halide lamp ("Eyedolphin 2000," a product 
of Iwasaki Electric Co., Ltd.) for 6 sec. 
Then, the unprocessed printing plate was exposed to an actinic light using 
the above-mentioned metal halide lamp for 60 sec at a distance of 1 m 
through a negative film having a dot image of 150 lines/in. which had been 
closely contact to the plate in vacuo. Thereafter, the cover film was 
peeled off and the plate after exposure was immersed in a pre-treating 
solution ["Isopar H" (aliphatic hydrocarbon solvent manufactured by Exxon 
Corp.)/butyl carbitol/ethyl cellosolve/monoethanolamine; 90/10/5/0.6 in 
weight ratio], and the plate surface after exposure was sufficiently 
wetted with the pre-treating solution for 1 min. Subsequently, the 
pre-treating solution on the plate surface was removed with a rubber 
sponge. A developer (butyl carbitol/water/2ethylbutyric acid/Crystal 
Violet; 20/80/2/0.2) was poured onto both the plate surface and a 
developing pad. By softly rubbing the surface of the plate with a 
developing pad, the silicone rubber layer in the imagewise exposed areas 
was removed, causing the surface of the photosensitive layer to be 
exposed. On the other hand, the silicon rubber layer in the unexposed 
areas remained unremoved in a firmly bonded state, thereby exactly 
reproducing the image borne on the negative film. 
Using the printing plate thus obtained, printing was conducted in the same 
manner as in EXAMPLE 1. The resulting printed matter has an extremely 
excellent image which reproduced 3% to 98% of dots of 150 lines/in. 
COMATIVE EXAMPLE 3 
A primer layer was provided on an aluminium plate in the same manner as in 
Comparative EXAMPLE 1. A photosensitive layer, a silicone rubber layer and 
a cover film were successively laminated on the primer layer in the same 
manner as in EXAMPLE 3, thereby obtaining an unprocessed printing plate. 
The content of the quinonediazide group in the primer layer of the 
unprocessed printing plate thus obtained was determined in the same manner 
as in EXAMPLE 1 and found to be below the effective detection range. 
The unprocessed printing plate was subjected to exposure and development in 
the same manner as in EXAMPLE 3, thereby obtaining a printing plate in 
which the photosensitive layer was exposed in the light exposed areas. 
Using the printing plate thus obtained, printing was conducted in the same 
manner as in Example 1. The printed matter thus obtained had an image 
which reproduced 3 % to 95 % of dots of 150 lines/in. and was poorer in 
the reproduction of shadow portions than that of EXAMPLE 3. 
EXAMPLE 4 
The following primer composition was applied on a 0.3 mm-thick aluminium 
plate (manufactured by Sumitomo Metal Industries, Ltd.) and heated at 
200.degree. C. for 2 min to form a 5 .mu.m-thick primer layer: 
__________________________________________________________________________ 
(1) 
a polyurethane resin ("Sanprene LQ-T1331," a 
product of Sanyo Chemical Industry Ltd.) 
100 
parts by weight 
(2) 
a blocked isocyanate ("Takenate B830,": a product 
of Takeda Chemical Industries, Ltd.) 
20 parts by weight 
(3) 
an epoxy/phenol/urea resin ("SJ9372," a product 
of Kansai Paint Co., Ltd.) 
8 parts by weight 
(4) 
dimethylformamide 725 
parts by weight 
__________________________________________________________________________ 
Thereafter, the following photosensitive layer composition was applied on 
the primer layer with a bar coater and dried in a hot air at 110.degree. 
C. for 1 min to form a photosensitive layer having a thickness of 2 
g/m.sup.2 : 
__________________________________________________________________________ 
(1) 
a product of an esterification of a phenolic 
novolak resin having a number-average degree of 
polymerization of 5.1 with 1,2-naphthoquinonediazide-5- 
sulfonyl chloride (percentage esterification: 25%) 
100 
parts by weight 
(2) 
diethylene glycol monoethyl ether acetate (having a 
molecular weight of 176 and a boiling point of 
217.degree. C.) 
40 parts by weight 
(3) 
4,4' diphenylmethane diisocyanate 
35 parts by weight 
(4) 
dibutyltin diacetate 0.2 
part by weight 
(5) 
dioxane 800 
parts by weight 
__________________________________________________________________________ 
Subsequently, the same silicone rubber composition as the one used in 
EXAMPLE 3 was applied on the photosensitive layer and cured under heating 
and humid conditions at a temperature as indicated in Table 1 and thereby 
forming a 2.3 .mu.m-thick silicone rubber layer. 
A cover film was laminated on the silicone rubber layer in the same manner 
as in EXAMPLE 1 to form an unprocessed printing plate. 
The content of the quinonediazide group in the primer layer of the 
unprocessed printing plate thus obtained was 0.7% by weight. 
The unprocessed printing plate was subjected to whole surface exposure and 
image exposure in the same manner as in EXAMPLE 3 and subjected to 
developing treatment in the same manner as in EXAMPLE 3 to obtain a 
printing plate. 
The printing plate thus obtained was attached to an offset printing machine 
("Komori Sprint 2 Color"), and printing was conducted with an ink 
("Aqualess PLT Blue," a product of Toyo Ink Mfg. Co., Ltd.) for the 
purpose of evaluating the dot reproduction. The results are shown in Table 
1. 
As can be seen from Table 1, the obtained printing plate exhibits an 
excellent dot reproduction in the range of a curing temperature from 
90.degree. C. to 115.degree. C. 
Thus, the printing plate has a wide range of silicone rubber layer curing 
temperatures at which it exhibits an excellent dot reproduction. 
With respect to the unprocessed printing plates as prepared above, the 
number of the pinholes present in the photosensitive layer was counted, 
and the diameter thereof was determined with a magnifying glass 
(magnification: .times.100). The results are shown in Table 2. As can be 
seen from Table 2, the number of pinholes in the printing plate in an 
unprocessed form is few and the printing plate had excellent film forming 
properties of the photosensitive layer over. 
The amount of diethylene glycol monoethyl ether acetate remaining in the 
photosensitive layer after the production of the unprocessed printing 
plate was determined by gas chromatography. The results are shown in Table 
1. 
TABLE 1 
______________________________________ 
Content of diethylene 
glycol monoethyl ether 
acetate after production 
Curing temp. 
of unprocessed printing 
Dot 
of silicone plate (based on the 
reproduction 
rubber photosensitive layer on 
(150 lines/in.) 
(.degree.C.) 
a solid basis) 1% to 99% 
______________________________________ 
90 7.7 wt % 2 to 97 
100 6.6 wt % 2 to 98 
105 6.1 wt % 2 to 98 
110 5.2 wt % 2 to 98 
115 4.1 wt % 3 to 98 
120 3.2 wt % 10 to 98 
______________________________________ 
TABLE 2 
______________________________________ 
Diameter 
pinhole of 
photosensitive 
Number of pinholes 
layer (per m.sup.2) 
______________________________________ 
10 to 50 .mu.m 
3 
50 to 200 .mu.m 
0 
200 .mu.m or more 
0 
______________________________________ 
Using the printing plate which was treated by temperature of 110.degree. 
C., 2,000 copies were printed under the following forced conditions to 
examine the resulting printed matter and the plate surface. 
Printing conditions: a modified model Hamada 
Star - 700 direct printing machine 
Printing pressure: underlay 500 .mu.m 
Ink: "Aqualess PLT Blue", a product of Toyo Ink Mfg. Co., Ltd. 
With respect to the printing plate, there was observed no damage to the 
printing area as well as the non-printing area, and satisfactory printed 
matter was obtained. 
EXAMPLES 5 and 6 
An unprocessed printing plate was prepared in substantially the same manner 
as in EXAMPLE 4, except that only diethylene glycol monoethyl acetate was 
omitted from the printing plate of EXAMPLE 4 and that an organic compound 
having at least one bond selected from an ether bond and an ester bond in 
its molecule was added in an amount as indicated in Table 3 to form a 
photosensitive layer having a thickness of 2.0 g/m.sup.2. 
The unprocessed printing plate thus obtained was exposed and developed in 
the same manner as in EXAMPLE 4 to obtain a printing plate similar to 
that prepared in EXAMPLE 4. The printing plate was subjected to a printing 
evaluation test in the same manner as in EXAMPLE 4 to examine the range of 
silicone rubber layer curing temperatures at which the printing plate 
exhibits a dot reproduction of 3 to 95% (150 lines/in.). The results are 
shown in Table 3. 
The number of the pinholes of the photosensitive layer was counted. The 
results are shown in Table 3. 
As can be seen from Table 3, the printing plates of EXAMPLES 5 and 6 
falling within the scope of the present invention have a wide range of 
silicone rubber layer curing temperatures at which the printing plate 
exhibits a dot reproduction of 3 to 95% (150 lines/in.) and a small number 
of the pinholes of the photosensitive layer. 
TABLE 3 
______________________________________ 
Range of silicone 
rubber layer curing 
temps. at which 
Number of 
Organic compound 
printing plate 
pinholes 
having at least 
exhibits a dot 
of photo- 
one selected from 
reproduction of 3 
sensitive 
Example 
an ether bond and 
to 95% layer 
No. an ester bond (150 lines/in.) 
(per m.sup.2) 
______________________________________ 
diethylene glycol 
Example 
dimethyl ether 
5 (MW: 134) 95 to 115.degree. C. 
5 
(b.p.: 160.degree. C.) 
(30 pts. wt.) 
propylene carbonate 
Example 
(MW: 102) 
6 (b.p.: 242.degree. C.) 
100 to 115.degree. C. 
3 
(30 pts. wt.) 
______________________________________ 
Among the printing plates listed in Table 3, those having a silicone rubber 
layer curing temperature of 115.degree. C. were selected, and 2,000 copies 
were printed under the same forced conditions as those of EXAMPLE 4. With 
respect to the printing plate obtained in EXAMPLES 5 and 6, there was 
observed no damage to the printing area as well as non-printing area, and 
satisfactory printed matter was obtained. 
The following effects can be attained by the printing plate of the present 
invention. 
(1) The addition of a quinonediazide group to the primer layer leads to 
prevention of halation due to active light rays passing through the 
photosensitive layer at the time of imagewise exposure, which improves the 
dot reproduction. 
(2) The addition of an organic compound which has a high compatibility with 
a quinonediazide compound, a boiling point of 150.degree. C. or above, at 
least one bond selected from an ether bond and an ester bond in its 
molecule and a molecular weight of 85 to 1,000 contributes to improve in 
the film forming properties of the photosensitive layer, which in turn 
widens the latitude of production. 
(3) Since the photosensitive layer is flexible, cracking hardly occurs. 
As is apparent from the foregoing description, a printing plate useful as a 
dry planographic printing plate can be provided by the present invention.