Method of producing a printing plate

A method of producing a printing plate is disclosed, which comprises the steps of a) providing, on an aluminium support, a photo-hardenable light-sensitive layer on a 50 .mu.m or less thick film to obtain a light-sensitive plate, the surface on the light-sensitive layer side of said support is electrolytically etched in a nitric acid solution to have an average surface roughness R.sub.a of 0.1 to 0.6 .mu.m; b) imagewise exposing the photo-hardenable photosensitive layer of the light-sensitive plate; c) applying heat or pressure to the exposed light-sensitive plate; d) removing the exposed light-sensitive layer from the light-sensitive plate to leave an unexposed light-sensitive layer on the aluminium support; and e) overall exposing the unexposed light-sensitive layer to harden the same.

FIELD OF THE INVENTION 
The present invention relates to a method for producing a printing plate, 
and more particularly to a method of producing a printing plate in a dry 
process. 
BACKGROUND OF THE INVENTION 
There is a conventionally known method in which a relief image is 
transferred to be formed on a grained support to thereby prepare a 
printing plate. For example, Japanese Patent Publication Open to Public 
Inspection (hereinafter abbreviated to JP O.P.I.) No. 9501/1977 proposes a 
method in which a grained aluminum plate has thereon a light-sensitive 
layer and a cover sheet and, after being imagewise exposed, has the 
unexposed portions of the light-sensitive layer eliminated together with 
the cover sheet therefrom to thereby prepare a negative-type printing 
plate: and JP O.P.I. Nos. 184049/1991 and 172351/1992 propose a method in 
which a grained aluminum plate is laminated with an imagewise exposed 
light-sensitive layer and has the unexposed area alone of the layer 
transferred to thereby prepare a printing plate. 
However, it was difficult to market the above printing plate-making method 
because nothing suitable as the grained support was available at all. The 
conventional mechanical graining emthod, which does not give uniform 
grain, makes it difficult to conduct uniform image transfer, so that the 
method is not suitable for the transfer-type image formation. The 
electrolytic etching method enables uniform graining, but the electrolytic 
etching in a hydrochloric acid bath or sulfuric acid bath forms 
crater-like grain, which prevents a resist material from extending over to 
the deepest part thereof at the time of the image transfer, resulting in a 
partial deterioration of the resist material's adhesion property and 
unsatisfactory printing durability. In a support anodized in the sulfuric 
acid bath, the adhesion of the transferred relief image to the grain was 
not sufficient, and no adequate printing durability was obtained. 
SUMMARY OF TEE INVENTION 
It is an object of the invention to provide a method of producing a 
printing plate which is capable of giving an improved image quality, and 
excellent in the suitability to printing as well as in the printing 
durability. 
It is another object of the invention to provide a method of preparing a 
printing plate which has an improved printing durability and which is 
improved so as to be free of ground staind.

DETAILED DESCRIPTION OF THE INVENTION 
The above objects of the invention are accomplished by the following 
constituents (1) to (9): 
Item 1. A method of producing a printing plate comprising the steps of a) 
providing, on an aluminum support, a photohardenable light-sensitive layer 
on a 50 .mu.m or less thick film to obtain a light-sensitive plate, the 
surface on the light-sensitive layer side of said support is 
electrolytically etched in a nitric acid solution to have an average 
surface roughness Ra of 0.1 to 0.6 .mu.m; b) imagewise exposing the 
photohardenable photosensitive layer of the light-sensitive plate; c) 
applying heat or pressure to the exposed light-sensitive plate; d) 
removing the exposed light-sensitive layer from the light-sensitive plate 
to leave an unexposed light-sensitive layer on the aluminum support; and 
e) overall exposing the unexposed light-sensitive layer to harden the 
same. 
Item 2. The method of producing a printing plate comprising the steps of a) 
imagewise exposing a light-sensitive material comprising a photohardenable 
light-sensitive layer on a 50 .mu.m or less thick film; b) providing, on 
an aluminum support, the exposed light-sensitive material while applying 
heat or pressure, the surface on the light-sensitive layer side of said 
support is electrolytically etched in a nitric acid solution to have an 
average surface roughness Ra of 0.1 to 0.6 .mu.m; c) removing the exposed 
light-sensitive layer from the exposed light-sensitive material to leave 
an unexposed light-sensitive layer on the aluminum support; and d) overall 
exposing the unexposed light-sensitive layer to harden the same. 
Item 3. The method of producing a printing plate comprising the steps of a) 
imagewise exposing a light-sensitive material comprising a 50 .mu.m or 
less thick film and provided thereon, a photohardenable light-sensitive 
layer and a cover sheet in this order: b) removing the cover sheet from 
the exposed light-sensitive material to leave an unexposed light-sensitive 
layer; c) providing, on an aluminum support, the unexposed light-sensitive 
layer while applying heat or pressure, the surface on the light-sensitive 
layer of said support is electrolytically etched in a nitric acid solution 
to have an average surface roughness Ra of 0.1 to 0.6 .mu.m; and d) 
overall exposing the unexposed light-sensitive layer to harden the same. 
Item 4. The method of Item 1, wherein the surface on the light-sensitive 
layer side of said support is mechanically grained, and then 
electrolytically etched in a nitric acid solution to have an average 
surface roughness Ra of 0.1 to 0.6 .mu.m. 
Item 5. The method of Item 2, wherein the surface on the light-sensitive 
layer side of said support is mechanically grained, and then 
electrolytically etched in a nitric acid solution to have an average 
surface roughness Ra of 0.1 to 0.6 .mu.m. 
Item 6. The method of Item 3, wherein the surface on the light-sensitive 
layer side of said support is mechanically grained, and then 
electrolytically etched in a nitric acid solution to have an average 
surface roughness Ra of 0.1 to 0.6 .mu.m. 
Item 7. The method of Item 1, wherein the surface on the light-sensitive 
layer side of said support is electrolytically etched in a nitric acid 
solution to have an average surface roughness Ra of 0.1 to 0.6 .mu.m, and 
then anodized in a phosphoric acid solution to obtain an anodized film 
weight of 5 to 40 mg/dm.sup.2. 
Item 8. The method of Item 2, wherein the surface on the light-sensitive 
layer side of said support is electrolytically etched in a nitric acid 
solution to have an average surface roughness Ra of 0.1 to 0.6 .mu.m, and 
then anodized in a phosphoric acid solution to obtain an anodized film 
weight of 5 to 40 mg/dm.sup.2. 
Item 9. The method of Item 3, wherein the surface on the light-sensitive 
layer side of said support is electrolytically etched in a nitric solution 
to have an average surface roughness Ra of 0.1 to 0.6 .mu.m, and then 
anodized in a phosphoric acid solution to obtain an anodized film weight 
of S to 40 mg/dm.sup.2. 
DETAILED DESCRIPTION OF THE INVENTION 
As the film used in the invention any material may be used as long as it is 
photographically inactive and dimensionally stable, typical examples of 
which include nitrocellulose film, triacetyl cellulose film, 
polyvinylacetal film, polystyrene film, polyethyleneterephthalate film, 
polycarbonate film, and poly-.alpha.-olefin film such as of polyethylene 
and polypropylene, and other resin films. The preferred among them is 
polyester film. A thin metal support or a complex support such as a 
metal-laminated plastic sheet or a metal-laminated paper support may also 
be used. Among these supports, an aluminum plate or an aluminum-laminated 
plastic support is preferred because of its stable dimensional stability 
and light weight. The above support preferably has its surface subjected 
to an appropriate subbing treatment for light-sensitive layer coatability 
or adhesion property improvement. Further, the support may have on the 
obverse or reverse thereof a dye or pigment-containing antihalation layer 
for the antihalation purpose. The surfaces on the light-sensitive resin 
layer-forming side and on the backing side of the support are preferably 
as matted as to have a surface roughness Ra of 1.0 to 3.0 .mu.m. 
The thickness of the film needs to be not more than 50 .mu.m, and 
preferably 4 to 20 .mu.m. If the thickness is less than 4 .mu.m, the 
dimensional stability of the support become poor. If the thickness exceeds 
20 .mu.m, the touchableness of the thin sheet with the support lowers to 
make it unable to obtain a good transfer image. 
Compositions to form the photohardenable light-sensitive resin layer used 
in the invention include photohardenable compositions, photo-crosslinkable 
compositions and diazo compounds. The preferably usable among these 
compositions are photopolymerizable compositions and photo-crosslinkable 
compositions. 
Useful photopolymerizable compositions are as follows: As the binder 
component there may be used thermoplastic polymers having an excellent 
compatibility with photopolymerizable components; for example, polyvinyl 
chloride, chlorinated polyolefin, poly(meth)acrylate, epoxy resin, 
polyurethane resin, cellulose derivatives, polyamide resin, 
polyvinylbutyral resin, polyvinylacetal resin, polyvinylpyrrolidone, 
gelatin, diallyl phthalate resin, butadiene-acrylonitrile copolymer, 
polyvinyl acetate, vinyl versatate, and the like. 
As the photopolymerizable component there may be used ethylenically 
unsaturated compounds, typical examples of which includ 2-hydroxyethyl 
(meth)acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, 
1,6-hexanediol di(meth)acrylate, trimethylolpropane triacrylate, 
pentaerythritol triacrylate, dipentaerythritol triacrylate, 
dipentaerythritol hexacrylate, and the like. These ethylenically 
unsaturated compounds may be used alone or in combination of two or more 
kinds thereof. 
The above photopolymerizable component is used preferably in an amount of 
10 to 500 parts by weight, more preferably 30 to 200 parts by weight per 
hundred parts by weight of the binder component. 
Useful materials as the photopolymerization initiator include such carbonyl 
compounds as described in J. Koser, the `Light-Sensitive Systems,` Chapter 
5; organic sulfur compounds, persulfide compounds, peroxidized compounds, 
redoxy compounds, azo and diazo compounds, halogenated compounds, 
photoreductive dyes, and the like. Further, concrete compounds as the 
photopolymerization initiater are exemplified in British Patent No. 
1,459,563. 
Compounds usable as the photosensitizer in the invention include benzoin 
derivatives such as benzoin-methyl ether, benzoin-isopropyl ether and 
.alpha.,.alpha.-dimethoy-.alpha.-phenylacetophenone; benzophenone 
derivatives such as benzophenone, 2,4-dichlorobenzophenone, 
o-benzoyl-methyl-benzoate, 4,4-bis(dimethylamino)benzophenone and 
4,4-bis(diethylamino)benzophenone; thioxanthone derivatives such as 
2-chlorothioxanthone and 2-isopropylthioxanthone; anthraquinone 
derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone; 
acridone derivatives such as N-methylacridone and N-butylacridone; 
.alpha.,.alpha.-diethoxyacetophenone; fluorenone; xanthrone; uranyl 
compounds; and halogenated compounds. 
As the photosensitizer the use of compounds having absorptions in the 
spectral region of visible rays, such as the following pyropyrrole 
compounds, quinacridone compounds, azo compounds and coumarin compounds, 
enables the obtaining of photopolymerizable compositions highly sensitive 
to a low-output visible laser light. 
The above-mentioned sensitizers are preferably pyropyrrole compounds 
represented by the following Formula 1, quinacridone compounds represented 
by the following Formula 2, azo compounds represented by the following 
Formula 3 or 4, and coumarin compounds represented by the following 
Formula 5. 
##STR1## 
wherein A and B each represent an alkyl group, an aralkyl group, a 
cycloalkyl group or a carbocyclic or heterocyclic aromatic grpi; R.sub.1 
and R.sub.2 each represent a hydrogen atom or a substituent not making the 
compound water-soluble; and E represents a sulfur atom or an oxygen atom. 
##STR2## 
wherein R.sub.1 represents an alkyl group; and R.sub.2 represents an alkyl 
group or a perhalogenated alkyl group. 
##STR3## 
In Formulas 3 and 4. R.sub.1 represents an alkyl group; and R.sub.2 and 
R.sub.3 each represent a hydrogen atom, a halogen atom, an alkyl group, an 
alkoxy group, a cyano group, a carboxyl group, a hydroxyl group, an 
acyloxy group, an alkylmercapto group or an alkoxycarbonyl group. 
##STR4## 
wherein R.sub.1, R.sub.2 and R.sub.3 each represent a hydrogen atom, a 
chlorine atom, a lower alkyl group, a lower dialkylamino group, a lower 
dialkenylamino or alicyclic amino group, or a heterocyclic group whose 
total number of carbon atoms and hetero atoms is 5 to 9; and Z is a 
hydrogen atom or a cyano group. 
Further, the incorporation of a cationic dye's borate complex having 
absorptions in a near-infrared spectral region into the 
photopolymerization initiator enables the obtaining of a 
photopolymerizable composition highly sensitive to a near-infrared solid 
laser light, etc. The preferred as the dye's borate anion formed from the 
cationic dye moiety and borate anion are those represented by the 
following Formula 6: 
##STR5## 
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each represent an alkyl 
group such as ethyl or butyl, an aryl group such as phenyl or naphthyl, an 
aralkyl group such as benzyl or phenethyl, an alkenyl group such as vinyl 
or allyl, an alkynyl group such as propynyl, a cycloalkyl group such as 
cyclopentyl or cyclohexyl, or a heterocyclic group such as thienyl or 
pyridyl; these groups each may further have a subsequent. The most 
preferred case is where at least one of the R.sub.1 to R.sub.4 is an aryl 
group and at least another is an alkyl group. 
The aryl group is preferably a phenyl or naphthyl group, which may be 
substituted by an alkyl or alkoxy group. The alkyl group is preferably an 
alkyl group having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, 
butyl, pentyl, hexyl, octyl or decyl. These alkyl groups may be 
substituted by a halogen atom, an alkoxy group, a hydroxyl group, a cyano 
group, a phenyl group, or the like. Examples of the cationic dye moiety 
include cationic ones having absorptions in the near-infrared region, such 
as cyanine, merocyanine, carbocyanine, rhodamine, azomethine, indoaniline, 
azulenium, polymethine, triarylmethine, indoline, thiazine, xanthene, 
acridine and oxazine dyes. 
The preferred as the cationic dye are cyanine dyes, azulenium dyes and 
indoaniline dyes. These dyes are described in, e.g., Shikizai 61(4) pp. 
215-216. Typical examples of such dyes are listed below: 
##STR6## 
With the photopolymerizable composition there may, if necessary, be used in 
combination a sensitization assistant, e.g., an amine compound such as 
Michler's ketone or 4,4'-bisdiethylaminobenzophenone. 
The thickness of the light-sensitive layer, although not restricted, may be 
approximately 0.5 .mu.m. The precise coating weight of the light-sensitive 
layer depends on the colorant (dye or pigment) used, but is preferably 0.5 
to 30 g/m.sup.2. The coating may be carried out by use of a bar coater, 
spin coater or other equivalent coater. 
A useful photo-crosslinkable compound for the photo-crosslinkable 
composition of the invention is a polyester comprised of the dicarboxylic 
acid unit represented by the following Formula 7 and the glycol unit 
represented by the following Formula 9. 
##STR7## 
wherein m represents an integer of 0 or 1, provided when m is 0, 1 and n 
each represent 0 or 1, and at least either one of 1 and n is 1, while when 
m is 1, 1 and n each is 0; and p represents 2 or 3. 
##STR8## 
wherein R represents an alkylene group having 2 to 4 carbon atoms; and r 
is an integer of 2, 3 or 4. 
##STR9## 
wherein R.sup.1 and R.sup.2 each represent a hydrogen atom or an alkyl 
group having 1 to 6 carbon atoms; and R.sup.3 represents a hydrogenated 
benzene ring. 
Examples of the dicarboxylic acid unit represented by Formula 7 include 
those derived from preferably phenylenediacrylic acid, p-carboxy-cinnamic 
acid, bis(p-carboxybenzal)cyclohexanone, 
bis(p-carboxybenzal)cyclopentanone, etc. The most preferred among them is 
a unit derived from phenylenediacrylic acid. 
Examples of the glycol unit represented by Formula 8 include those derived 
from diethylene glycol, triethylene glycol, tetraethylene glycol, 
dipropylene glycol, tripropylene glycol, and the like. 
Examples of the glycol unit represented by Formula 9 include those derived 
from hydrogenated bisphenol F and hydrogenated bisphenol A. The 
hydrogenation degree had better be high; those having Formula 9 wherein 
R.sup.3 is a cyclohexane ring are especially preferred. 
The rate of the glycol unit of Formula 8 accounting for of the whole glycol 
unit is preferably 10 to 90 mol %, more preferably 30 to 70 mol %. If the 
rate exceeds the above range, the composition's resistance to chemicals 
weakens, while if it is smaller than the lower limit of the range, the 
composition's sensitivity falls. 
The average molecular weight of the light-sensitive polyester, although not 
restricted, is preferably 5,000 to 50,000, more preferably 9,000 to 
20,000. The term `average molecular weight` herein means a weight average 
molecular weight. 
The above light-sensitive polyester can be easily prepared according to a 
well-known method, such as the method described in U.S. Pat. No. 
3,622,320. Namely, a dicarboxylic acid ester that forms a dicarboxylic 
acid unit represented by Formula 7 and a glycol mixture that forms the 
glycol units represented by Formulas 8 and 9 are dissolved by heating, and 
titanium and germanium catalysts are added thereto to carry out ester 
exchange, and then the reaction system, under gradually reduced pressure, 
is heated to raise its temperature to have its excessive glycol distilled, 
whereby an objective product can be obtained. The reaction period of time 
is normally about 4 hours, the temperature in the final stage of the 
polymerization is 230.degree. to 240.degree. C., and the reduced pressure 
is approximately 3 mmHg. 
The photo-crosslinkable composition is usually prepared by dissolving the 
foregoing light-sensitive polymer in a solvent. Suitable examples of the 
solvent, although dependent upon the molecular weight and composition of 
the polymer used, include chlorine solvents such as methylene chloride, 
chloroform, trichloroethane, trichloroethylene, chlorobenzene, 
dichlorobenzene, and carbon tetrachloride; alcohol solvents such as 
furfuryl alcohol, tetrahydrofurfuryl alcohol and benzyl alcohol; ether 
solvents such as dioxane and tetrahydrofuran; ethylene glycol-monoalkyl 
ethers and diethylene glycol-monoalkyl ethers such as ethylene 
glycol-monomethyl ether, ethylene glycol-monoethyl ether, ethylene 
glycol-monopropyl ether, ethylene glycol-monobutyl ether, diethylene 
glycol-monomethyl ether, diethylene glycol-monoethyl ether, diethylene 
glycol-monopropyl ether and diethylene glycol-monobutyl ether, ether, 
solvents such as ethylene glycol-ethyl ether acetate, diethylene 
glycol-ethyl ether acetate and ethyl acetate, nitrogen-containing 
compounds such as dimethylformamide, methylpyrrolidone, nitroethane and 
nitrobenzene; ketone solvents such as methyl-ethyl ketone, methyl-isobutyl 
ketone, cyclohexanone, methylcyclohexanone and 
4-methyl-4-methoxy-2-pentanone; and dimethylsulfoxide. The solvent to be 
used in the invention is arbitrarily selected from among these compounds. 
The photo-crosslinkable composition may, if necessary, contain various 
components in addition to the above components. For example, it may 
contain a sensitizer or phthalocyanine, a pigment such as zinc oxide, and 
dyes such as Victoria Pure Blue BOH, ethyl violet, and the like. 
As the sensitizer any compounds applicable to this field may be used which 
include aromatic carbonyl compounds such as benzophenone derivatives, 
benzanthrone derivatives, naphthothiazoline derivatives, quinones, etc.; 
and aromatic nitro compounds. 
The benzophenone derivatives include Michler's ketone, 
diethylaminoethylbenzophenone, etc.; the benzanthrone derivatives include 
benzanthrone, 6,11-dichlorobenzanthrone, 11-chloro-6-hydroxybenzanthrone, 
1-carboethoxy-2-keto-3-methyl-3-aza-1,9-benzanthrone, etc.; the quinones 
include 1,8-dimethoxyanthraquinone, 1,8-dichloroanthraquinone, 
1,2-benzanthraquinone, etc.; the aromatic nitro compounds include mono- 
and polynitro compounds such as 5-nitroacenaphthene, 2-nitrofluorene, 
2,7-dinitrofluorene, 1-nitronaphthalene, 1,5-dinitronaphthalene, etc.; the 
naphthothiazoline derivatives include 
2-dibenzoylmethylene-3-methylnaphthothiazoline, 
2-benzoylmethylene-3-methylnaphthothiazoline, and the like. 
The photo-crosslinkable composition is coated on the thin sheet in the 
usual manner by using a well-known coating method such as a dip coat, 
coating rod, spinner coat or spray coat process, whereby a laminate can be 
prepared. 
The light-sensitive layer of the invention may contain the colorant 
described in JP O.P.I. No. 172351/1992 in addition to the above-mentioned 
materials. 
The thickness of the light-sensitive layer of the invention is 0.1 to 10 
.mu.m, and preferably 0.5 to 5 .mu.m. 
In Items 1 through 9 of the invention, a thermosoftening layer may, if 
necessary, be provided between the thin sheet and the light-sensitive 
resin layer for the purpose of improving the transferability of the relief 
image onto the aluminum support. The thermosoftening layer is comprised of 
a thermoplastic resin, which has the property of being softened by 
heating. As the thermosoftening layer there may be used the 
thermosoftening layer described in JP O.P.I. No. 172351/1992. The 
thermosoftening layer is preferably comprised of a polyolefin compound, 
and more preferably a resin having a softening point of 30.degree. C. to 
150.degree. C. 
The cover sheet according to Items 3, 6 and 9 of the invention, where 
exposure is made from the cover sheet side, needs to have a good 
light-transmittance and a uniform surface. Regarding the light 
transmittance, the cover sheet needs to have a transmittance of not less 
than 50%, preferably not less than 65% in the spectral range of near 
ultraviolet and visible rays (wavelength range of about 290 nm-650 nm). 
Concrete compounds usable as the cover sheet are polyethylene 
terephthalate, polypropylene, polyethylene, cellulose triacetate, 
cellulose diacetate, polyvinyl chloride, polyvinyl alcohol, polycarbonate, 
polystyrene, cellophane, polyvinylidene chloride copolymers, polyamide, 
polyimide, vinyl chloride-vinyl acetate copolymer, 
polytetrafluoroethylene, polytrifluoroethylene, and the like. Any complex 
material composed of two or more kinds of these compounds may also be 
used. 
The cover film may have a thickness of preferably 5 to 100 .mu.m, and more 
preferably 10 to 40 .mu.m. 
The aluminum support used in Items 1 to 3 of the invention is explained. As 
the substrate of the aluminum support there may be used a pure aluminum 
plate, an aluminum alloy plate, or other metal plate with its surface 
covered with aluminum or aluminum alloy. Film or paper may also be used. 
The surface of the aluminum support is grained by electrolytic etching, 
which is carried out by use of an electrolytic bath filled with nitric 
acid or a nitric acid-containing acid mixture. Prior to the electrolytic 
etching, the aluminum support may be subjected to a mechanical graining 
treatment such as ball graining, brush graining, liquid honing or buff 
graining. The aluminum support is surface-grained so as to have a surface 
roughness Ra of 0.1 to 0.6 .mu.m. 
For the electrolytic etching, the aluminum support is immersed in a bath 
containing nitric acid in an amount of preferably 0.1 to 0.5 mol/liter, 
more preferably 0.2 to 0.4 mol/liter to be subjected to electrolytic 
etching for 10 seconds to 3 minutes at a temperature of preferably 
20.degree. to 50.degree. C., more preferably 25.degree. to 45.degree. C. 
under the condition of a current density of 20 to 200 A/dm.sup.2. 
The aluminum support that has been subjected to electrolytic etching is 
preferably chemically cleand because it is necessary to remove the 
residual, so called `smut`, from its surface. The above treatments include 
the alkali etching method described in Japanese Patent Examined 
Publication (hereinafter abbreviated to JP E.P.) No. 28123/1973 and the 
sulfuric acid desmut method described in JP O.P.I. No. 12739/1978. 
After the electrolytic etching treatment, the aluminum support is 
preferably subjected to anodizing treatment to form an anodized coat 
thereon. 
The anodizing treatment can be carried out by electrolyzing the aluminum 
support with itself used as an anode for 10 seconds to 2 minutes under the 
condition of a current density of 1 to 10 A/dm.sup.2 in an electrolytic 
bath filled with an eletrolyte, i.e., an aqueous solution of one or two or 
more of sulfuric acid, chromic acid, oxalic acid, phosphoric acid, malonic 
acid, etc., in a total concentration of 10 to 50%. There is another 
anodizing method as described in U.S. Pat. No. 1,412,768, in which the 
electrolysis is made in sulfuric acid at a high current density. The 
anodized coat amount is preferably 1 to 50 mg/dm.sup.2, and more 
preferably 5 to 30 mg/dm.sup.2. 
In the electrolytic bath, the use of phosphoric acid is preferred because 
it improves the aluminum support's adhesion to the transferred image. 
The anodized aluminum support may be further subjected to a treatment of 
immersing it in an aqueous solution of an alkali metal silicate such as 
sodium silicate as described in U.S. Pat. Nos. 2,714,066 and 3,181,461; 
may have thereon a subbing layer comprising a hydrophilic cellulose (such 
as carboxymethyl cellulose) containing a water-soluble metal salt (such as 
zinc acetate) as described in U.S. Pat. No. 3,860,426; and may be 
subjected to polyvinylsulfonic acid treatment as described in U.S. Pat. 
No. 4,153,461. 
The aluminum support according to Items 4 to 6 of the invention is 
explained. As the substrate of the aluminum support there may be used a 
pure aluminum plate, an alluminum alloy plate, or other metal plate with 
its surface covered with aluminum or aluminum alloy. Film or paper may 
also be used. The surface of the aluminum support is subjected to 
mechanical graining, which is following by electrolytic etching treatment. 
The above mechanical graining method includes a sand blast method, a ball 
graining method, a wire graining method, a brush graining method that uses 
a nylon brush and abrasive/water slurry, and a honing method that makes a 
high-pressure blow of abrasive/water slurry against the surface. 
The electrolytic etching is conducted in an electrolytic bath containing 
hydrochloric acid, sulfuric acid, nitric acid or a mixture of these acids. 
It is preferable to subject the aluminum support to electrolytic etching 
by immersing it in an aqueous solution of an acid in a concentration of 
preferably 0.1 to 0.5 mol/liter, more preferably 0.2 to 0.4 mol/liter for 
10 secpmds to 3 minutes at a temperature of preferably 20.degree. to 
50.degree. C., more preferably 25.degree. to 45.degree. C. under the 
condition of a current density of 20 to 200 A/dm.sup.2. 
Regarding the surface roughness of the obtained aluminum support, its 
maximum value Rmax is not more than 5 .mu.m, and the peak count of the 
surface roughness is preferably substantially zero from the image 
reproduction point of view. 
The aluminum support that has been subjected to electrolytic etching is 
preferably chemically cleaned because it is necessary to remove the 
residual, so-called `smut,` from its surface. The above treatments include 
the alkali etching method described in JP E.P. No. 2813/1973 and the 
sulfuric acid desmut method described in JP O.P.I. No. 12739/1987. 
After the electrolytic etching treatment, the aluminum support is 
preferably subjected to anodizing treatment to thereby form an anodized 
coat thereon. The anodizing treatment can be carried out by electrolyzing 
the aluminum support with itself used as an anode for 10 seconds to 2 
minutes under the condition of a current density of 1 to 10 A/dm.sup.2 in 
an electrolytic bath filled with an electrolyte, i.e., an aqueous solution 
of one or two or more of sulfuric acid, chromic acid, oxalic acid, 
phosphoric acid, malonic acid, etc., in a total concentration of 10 to 
50%. There is another anodizing method as described in U.S. Pat. No. 
1,412,768, in which the electrolysis is made in sulfuric acid at a high 
current density. The anodized coat amount is preferably 1 to 50 
mg/dm.sup.2, and more preferably 5 to 30 mg/dm.sup.2. In the electrolytic 
bath, the use of phosphoric acid is preferred because it improves the 
aluminum support's adhesion to the transferred image. 
The anodized aluminum support may be further subjected to a treatment of 
immersing it in an aqueous solution of an alkali metal silicate such as 
sodium silicate as described in U.S. Pat. Nos. 2,714,066 and 3,181,461; 
may have thereon a subbing layer comprising a hydrophilic cellulose (such 
as carboxymethyl cellulose) containing a water-soluble metal salt (such as 
zinc acetate) as described in U.S. Pat. No. 3,860,426; and may be 
subjected to polyvinylsulfuric acid treatment as described in U.S. Pat. 
No. 4,153,461. 
The aluminum support according to Items 7 to 9 of the invention is 
explained. As the substrate of the aluminum support there may be used a 
pure aluminum plate, an aluminum alloy plate, or other metal plate with 
its surface covered with aluminum or aluminum alloy. Film or paper may 
also be used. The surface of the aluminum support is grained by a 
mechanical graining method such as a brush graining or ball graining 
method or an electromechanical method such as an electrolytic etching 
method or a combination of both methods. 
The electrolytic etching is conducted in an electrolytic bath containing 
nitric acid, hydrochloric acid, sulfuric acid, or a mixture of these 
acids. It is preferable to subject the aluminum support to electrolytic 
etching by immersing it in an electrolytic bath containing an aqueous 
solution of nitric acid in a concentration of preferably 0.1 to 0.5 
mol/liter, more preferably 0.2 to 0.4 mol/liter for 10 seconds to 3 
minutes at a temperature of preferably 20.degree. to 50.degree. C., more 
preferably 25 to 45.degree. C. under the condition of a current density of 
20 to 200 A/dm.sup.2. 
Prior to the electrolytic etching, it is preferable to subject the aluminum 
support to mechanical graining treatment such as ball graining, brush 
graining, liquid honing or buff graining treatment. 
The aluminum support that has been subjected to electrolytic etching is 
preferably chemically cleand because it is necessary to remove the 
residual, so-called `smut,` from its surface. The above treatments include 
the alkali etching method described in JP E.P. No. 28123/1973 and the 
sulfuric acid desmut method described in JP O.P.I. No. 12799/1978. 
After the electrolytic etching treatment, the aluminum support is 
preferably subjected to anodizing treatment to thereby form an anodized 
coat thereon. The anodizing treatment can be carried out by electrolyzing 
the aluminum support with itself used as an anode for 10 seconds to 2 
minutes under the condition of a current density of 1 to 10 A/dm.sup.2 in 
an electrolytic bath containing phosphoric acid in a concentration of 10 
to 50% as an electrolyte. The formed anodized coat amount is preferably 5 
to 40 mg/dm.sup.2, and more preferably 10 to 30 mg/dm.sup.2. 
The anodized aluminum support may be further subjected to a treatment of 
immersing it in an aqueous solution of an alkali metal silicate such as 
sodium silicate as described in U.S. Pat. Nos. 2,714,066 and 3,181,461; 
may have thereon a subbing layer comprising a hydrophilic cellulose (such 
as carboxymethyl cellulose) containing a water-soluble metal salt (such as 
zinc acetate) as described in U.S. Pat. No. 3,860,426; and may be 
subjected to polyvinylsulfonic acid treatment as described in U.S. Pat. 
No. 4,153,461. 
According to the preferred embodiment of Items 7 to 9 of the invention, the 
aluminum support has a surface roughness Rmax of 1 to 5 .mu.m and Ra of 
0.1 to 0.6 .mu.m, in which the peak count value that exceeds a limit which 
is provided 2 .mu.m above the center line and is in parallel with the 
center line is substantially zero, wherein the surface maximum roughness 
Rmax and the average surface roughness Ra are values obtained by measuring 
with a probe-type surface roughness tester and determined in accordance 
with German Standard DIN3768, and the peak count, stipulated by the same 
German Standard, is, in the surface roughness profile R, the number of 
peaks that exceed a line provided above and in parallel with the center 
line. 
In the invention, that the above `peak count is substantially zero` implies 
that the average value of the peak count numbers measured according to the 
aforementioned measuring method at 10 or more pints selected at random on 
the surface of the support is not more than 0.49/nm. 
The above surface graining of the aluminum support results in the 
improvement of the image resolution as well as of the image 
transferrability. 
Next, the method of producing the printing plate of the invention is 
explained. In the invention, `to laminate` means `to place one layer upon 
another to bring them into close contact with each other.` 
The invention of Item 1 is of a printing plate producing method which is 
such that a photohardenable light-sensitive resin layer-having thin sheet 
with its light-sensitive layer side laminated to an aluminum support is 
imagewise exposed; both the thin sheet and the exposed portion of the 
light-sensitive resin layer are removed from the aluminum support after 
completion of or simultaneously with heating and/or pressing the laminated 
unit; and the unexposed portion of the light-sensitive resin layer 
remaining on the support is subjected to after-exposure treatment to thus 
harden the same to thereby prepare a printing plate. Regarding the 
imagewise exposure, the light source used for this purpose is not 
particularly restricted as long as it can cause the light-sensitive 
composition to effect hardening reaction. Contact printing exposure may be 
made through a light-permeable original image. Alternatively, a modulable 
light source like a laser light may be used to make line-to-line or 
point-to-point sequential scanning exposure. 
After the imagewise exposure, the laminated unit is subjected to heating 
and/or pressure treatment in order to have the unexposed portion of the 
light-sensitive resin layer transferred onto the aluminum support, but the 
heating is preferably made at a temperature of not lower than 80.degree. 
C. under pressure of not less than 1 kg/m.sup.2. Peeling the thin sheet 
apart from the support is performed simultaneously with or after the 
heating and/or pressure treatment. More preferably the peeling is carried 
out in parallel with the heating/pressure treatment. To be concrete, while 
letting the laminated unit pass between the juxtaposed heated rollers 
having pressure, the thin sheet and the support are peeled apart on the 
outlet side of the rollers. At this moment, the exposed portion of the 
light-sensitive resin layer is removed together with the thin sheet from 
the support, while the unexposed of the same light-sensitive layer is 
transferred onto the aluminum support. The unhardened light-sensitive 
resin transferred onto the support is then again exposed to an active 
light to be hardened, whereby a printing plate is obtained. 
The invention of Item 2 is of a printing plate producing method which is 
such that prior to laminating the aluminum support with the 
light-sensitive resin layer of the thin sheet, an imagewie exposure is 
given to the thin sheet unit from the thin sheet side or from the cover 
sheet side thereof, and thereafter the unexposed portion of the 
light-sensitive resin layer is transferred onto the aluminum support. The 
conditions of the imagewise exposure, transfer and after-exposure may be 
the same as in claim 1. 
The invention of Item 3 is of a printing plate producing method which is 
such that prior to laminating the aluminum support with the 
light-sensitive resin layer, an imagewise exposure is given to the thin 
sheet unit composed of a thin sheet, a photohardenable light-sensitive 
resin layer and a cover sheet from the thin sheet side or cover sheet side 
thereof, the cover sheet is removed to make a peel development to thereby 
form a relief image on the thin sheet, and the relief image is transferred 
onto the aluminum support. The conditions of the imagewise exposure, 
transfer and after-exposure may be the same as in claim 1. 
The invention of Item 4 is of a method in which a printing plate is 
produced in the same manner as in Item 1 except that the aluminum 
support's graining method is different from that of Item 1. Item 5 is of a 
method in which a printing plate is produced in the same manner as in Item 
4 except that the imagewise exposure is conducted prior to laminating the 
aluminum support with the light-sensitive resin layer. Item 6 is of a 
method in which a printing plate is prepared in the same manner as in Item 
3 except that the aluminum support's graining method is different from 
that of Item 3. Item 7 is of a method in which a printing plate is 
prepared in the same manner as in Item 1 except that the aluminum 
support's graining method is different from that of Item 1. Item 8 is of a 
method in which a printing plate is produced in the same manner as in Item 
2 except that the aluminum support's graining method is different from 
that of Item 2. And Item 9 is of a method in which a printing plate is 
produced in the same manner as in Item 3 except that the aluminum 
support's graining method is different from that of Item 3. 
EXAMPLES 
The invention is illustrated in detail by the following examples. The term 
`part` used in the following examples means part(s) by weight. 
Example 1 (Item 1) 
On a subbed polyethylene terephthalate film of 10 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylthioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
An aluminum support with its surface subjected to nitric acid/electrolytic 
etching treatment was laminated with the above composition under pressure 
of 1 kg/cm.sup.2. Subsequently, a transparent positive original image was 
brought into close contact with the polyethylene terephthalate film side 
of the aluminum support, and it was exposed through the original to a 
ultraviolet light. The aluminum plate was let pass between juxtaposed 
pressure rollers heated to 80.degree. C. and having a pressure of 3 
kg/cm.sup.2. The ethylene terephthalate film was peeled off together with 
the exposed portion from the aluminum plate, and the unexposed portion 
remained on the aluminum plate. The aluminum plate was overall exposed to 
an ultraviolet light to harden the remaining unexposed portion. The 
obtained printing plate was set to a Heidelberg GTO printing machine to 
make a run of printing, whereby more than 100,000 good print copies were 
obtained. 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the etched 
surface roughness was measured, the aluminum plate had a surface roughness 
Ra of 0.3 .mu.m. Next, the aluminum plate was immersed for 2 minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for smut treatment, 
and then anodized in an aqueous 20% sulfuric acid solution at a current 
density of 2.5A/dm.sup.2 so as to have an anodized coat weight of 30 
mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.001% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
Example 2 (Item 2) 
On a subbed polyethylene terephthalate film of 25 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylthioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
Further, on the above composition was laminated polypropylene film of 6 
.mu.m in thickness as a cover sheet. 
A light-permeable positive image original as brought into contact with the 
support side of the light-sensitive material, and the light-sensitive 
material was exposed through the original to a ultraviolet light. Next, 
the cover sheet was peeled off, and the rest was laminated at 100.degree. 
C. under a pressure of 1 kg/cm.sup.2 upon an aluminum plate that was 
subjected to nitric acid/electrolytic etching treatment under the 
following conditions. The exposed poriton was peeled off together with the 
film, and the unexposed portion was transferred onto the aluminum plate. 
The aluminum plate was overall exposed to a ultraviolet light to harden 
the remaining unexposed portion. The thus obtained printing plate was set 
to a Heidelberg GTO printing machine to make a run of printing, whereby 
more than 100,000 good print copies were obtained. 
Electrolytic etching conditions 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the etched 
surface roughness was measured, the aluminum plade had a surface roughness 
Ra of 0.3 .mu.m. Next, the aluminum plate was immersed for 2 minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for desmut treatment, 
and then anodized in an aqueous 20% sulfuric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 30 
mg/dm.sup.2. The obtained aluminum plate was immersed for 10 seconds in an 
aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., washed, 
and then dried. 
Example 3 (Item 3) 
On a subbed polyethylene terephthalate film of 25 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thicknee of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, Produced by Sanyo Kokuksaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylthioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
Further, on the above composition was laminated polypropylene film of 6 
.mu.m in thickness as a cover sheet. 
A light permeable positive original image was brought into contact with the 
support side of the above light-sensitive material, and the 
light-sensitive material was exposed through the original to a ultraviolet 
light, and then the cover sheet was removed, whereby the exposed portion 
of the light-sensitive layer remained on the support side, and a relief 
image was formed. 
Subsequently, an aluminum plate that was subjected to nitric 
acid/electrolytic etching treatment under the following conditions was 
laminated with the above light-sensitive layer at 100.degree. C. under a 
pressure of 1 kg/cm.sup.2. The exposed portion was peeled off together 
with the film, and the remaining unexposed portion was transferred onto 
the aluminum plate. The aluminum plate was overall exposed to a 
ultraviolet light to harden the remaining unexposed portion. The thus 
obtained printing plate was set to a Heidelberg GTO printing machine to 
make a run of printing, whereby more than 100,000 good print copies were 
obtained. 
Electrolytic etching conditions 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the etch surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. The aluminum plate was then immersed for two minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for smut treatment, 
and then anodized in an aqueous 20% sulfuric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 30 
mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C. washed, 
and then dried. 
Example 4 (Item 4) 
On a subbed polyethylene terephthalate film of 25 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylenethioxanthon, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
The above composition was laminated upon an aluminum plate that was 
subjected to nitric acid/electrolytic etching treatment under the 
following conditions. A light-permeable positive original was brought into 
close contact with the polyethylene terephthalate film side of the 
aluminum plate, and the aluminum plate was exposed through the original to 
a ultraviolet light. The aluminum plate was then let pass between a pair 
of juxtaposed rollers heated to 80.degree. C. and having a pressure of 3 
kg/cm.sup.2, and the polyethylene terephthalate film was peeled off 
together with the exposed portion from the aluminum plate, and the exposed 
portion remained on the aluminum plate. The aluminum plate was overall 
exposed to a ultraviolet light to harden the remaining unexposed portion. 
The thus obtained printing plate was set to a Heidelberg GTO printing 
machine to make a run of printing, whereby more than 100,000 good print 
copies were obtained. 
Electrolytic etching conditions 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush. The grained aluminum plate, after being washed, was immersed 
for 10 seconds in an aqueous 10% sodium hydroxide solution at 30.degree. 
C. for surface etching. 
The aluminum plate was then subjected to electrolytic etching treatment in 
an aqueous 1% nitric acid solution bath with a quantity of anode 
electricity of 80 coulomb/dm.sup. 2 per hour. When the surface roughness 
was measured, the aluminum plate had a surface roughness Ra of 0.3 .mu.m. 
Next, the aluminum plate was immersed for 2 minutes in an aqueous 30% 
sulfuric acid solution at 55.degree. C. for desmut treatment, and then 
anodized in an aqueous 20% sulfuric acid solution at a current density of 
2.5 A/dm.sup.2 so as to have an anodized coat weight of 30 mg/dm.sup.2. 
The obtained aluminum support was immersed for 10 seconds in an aqueous 
0.01% carboxymethyl cellulose solution at 90.degree. C., washed, and then 
dried. 
Example 5 (Item 5) 
On a subbed polyethylene terephthalate film of 25 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylthioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba was 33 parts 
Methylethyl ketone 1000 parts 
Further, on the above composition was laminated polypropylene film of 6 
.mu.m in thickness as a cover sheet. 
A transparent positive image original was brought into close contact with 
the support side of the light-sensitive material, and the light-sensitive 
material was exposed through the original to a ultraviolet light. Then the 
cover sheet was removed, and the rest was laminated at a temperature of 
100.degree. C. under pressure of 1 l kg/cm.sup.2 upon an aluminum plate 
that was subjected to nitric acid/electrolytic etching treatment under the 
following conditions. The exposed portion was peeled off together with the 
film, while the unexposed portion was transferred onto the aluminum plate. 
The aluminum plate was overall exposed to a ultraviolet light to thereby 
harden the remaining unexposed portion. The thus obtained printing plate 
was set to a Heidelberg GTO printing machine to make a run of printing, 
whereby more than 100,000 good print copies were obtained. 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush, washed, and then immersed for 10 seconds in an aqueous 10% 
sodium hydroxide solution at for surface watching. 
Next, the grained aluminum plate was subjected to electrolytic etching 
treatment in an aqueous 1% nitric acid solution with a quantity of anode 
electricity of 80 coulomb/dm.sup. 2 per hour. When the etched surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. 
The aluminum plate was then immersed in an aqueous sulfuric acid solution 
for 2 minute-desmut treatment at 55.degree. C., and subjected to anodizing 
treatment in an aqueous 20% sulfuric acid solution at a current density of 
2.5 A/dm.sup.2 so as to have an anodized coat weight of 30 mg/dm.sup.2. 
The obtained aluminum support was immersed for 10 seconds in an aqueous 
0.01% carboxymethyl cellulose solution at 90.degree. C., washed, and then 
dried. 
Example 6 (Item 6) 
On a subbed polyethylene terephthalate film of 25 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylenethioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
Further, on the above composition was laminated polypropylene film of 6 
.mu.m in thickness as a cover sheet. 
A light-permeable original image was brought into contact with the support 
side of the light-sensitive material, and the light-sensitive material was 
exposed through the original to a ultraviolet light. After that, the cover 
sheet was removed, and the rest of the light-sensitive material was 
laminated under pressure of 1 kg/cm.sup.2 upon an aluminum plate that was 
subjected to nitric acid/electrolytic etching treatment under the 
following conditions. The aluminum plate was overall exposed to a 
ultraviolet light to harden the remaining unexposed portion. The printing 
plate thus obtained was set to a Heidelberg GTO printing machine to make a 
run of printing, whereby more than 100,000 good print copies were 
obtained. 
Electrolytic etching conditions 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush. The grained aluminum plate, after being washed, was immersed 
for 10 seconds in an aqueous 10% sodium hydroxide solution at 
30.degree.0C. for surface etching. 
Next, the aluminum plate was subjected to electrolytic etching treatment in 
an aqueous 1% nitric acid solution with a quantity of anode electricity of 
80 coulomb/dm.sup.2 per hour. When the surface roughness was measured, the 
aluminum plate had a surface roughness Ra of 0.3 .mu.m. 
Subsequently, the aluminum plate was immersed for two minutes in an aqueous 
30% sulfuric acid solution at 55.degree. C. for desmut treatment, and then 
anodized in an aqueous 20% sulfuric acid solution at a current density of 
2.5 A/dm.sup.2 so as to have an anodized coat weight of 30 mg/dm.sup.2. 
The obtained aluminum support was immersed for 10 seconds in an aqueous 
0.01% carboxymethyl cellulose solution at 90.degree. C., washed, and then 
dried. 
Example 7 (Item 7) 
On a subbed polyethylene terephthalate film of 10 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylthioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
An aluminum plate that was grained/etched under the following conditions 
was laminated with the above composition under a pressure of 1 kg/m.sup.2. 
A light-permeable original image was brought into contact with the 
polyethylene terephthalate film side of the aluminum plate, and the 
aluminum plate was exposed through the original image to a ultraviolet 
light. The aluminum plate was then let pass between a pair of juxtaposed 
rollers heated to 80.degree. C. and having a pressure of 3 kg/cm.sup.2. 
When the polyethylene terephthalate film was peeled from the aluminum 
plate, the unexposed portion remained on the aluminum plate. The aluminum 
plate was overall exposed to a ultraviolet light to harden the remaining 
unexposed portion. The obtained printing plate was set to a Heidelberg GTO 
printing machine to make a run of printing, whereby more than 100,000 good 
print copies were obtained. 
Graining/etching conditions 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush, washed, and then immersed for seconds in an aqueous 10% sodium 
hydroxide solution at 30.degree. C. for surface etching. 
The above aluminum plate was then subjected to electrolytic etching 
treatment in an aqueous 1% nitric acid solution with a quantity of anode 
electricity of 80 coulomb/dm.sup.2 per hour. When the surface roughness 
was measured, the aluminum plate had a surface roughness Ra of 0.3 .mu.m. 
Subsequently, the aluminum plate was immersed for two minutes in an aqueous 
30% sulfuric acid solution at 55.degree. C. for desmut treatment, and 
thereafter anodized in an aqueous 20% phosphoric acid solution at a 
current density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 
20 mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds 
in an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
Example 8 (Item 8) 
On a subbed polyethylene terephthalate film of 10 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 100 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobanzoate 3 parts 
DETX (diethylenethioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
Further, on the above composition was laminated polypropylene film of 6 
.mu.m in thickness as a cover sheet. 
A transparent original positive image was brought into contact with the 
support side of the light-sensitive material, and the light-sensitive 
material was exposed through the original to a ultraviolet light. After 
that, the cover sheet was peeled off, and the rest was laminated under a 
pressure of 1 kg/cm.sup.2 at 100.degree. C. upon an aluminum plate that 
was subjected to nitric acid/electrolytic etching treatment under the 
following conditions. The exposed portion was peeled off together with the 
film, while the unexposed portion was transferred onto the aluminum plate. 
The aluminum plate was overall exposed to a ultraviolet light to harden 
the remaining unexposed portion. The thus obtained printing plate was set 
to a Heidelberg GTO printing machine to make a run of printing, whereby 
more than 100,000 good print copies were obtained. 
Etching conditions 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. Further, the aluminum plate was immersed for 2 minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for desmut treatment, 
and then anodized in an aqueous 20% phosphoric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 20 
mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
Example 9 (Item 9) 
On a subbed polyethylene terephthalate film of 10 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
Ethyl-p-aminobenzoate 3 parts 
DETX (diethylthioxanthone, produced by Ciba Geigy) 3 parts 
Carnauba wax 33 parts 
Methylethyl ketone 1000 parts 
Further, on the above composition was laminated polypropylene film of 6 
.mu.m in thickness as a cover sheet. 
A light-permeable positive image original was brought into contact with the 
support side of the light-sensitive material, and the light-sensitive 
material was exposed through the original to a ultraviolet light. Then, 
the cover sheet was removed, and the rest was laminated under a pressure 
of 1 kg/cm.sup.2 at 100.degree. C. upon an aluminum plate that was 
subjected to nitric acid/electrolytic etching treatment under the 
following conditions. The exposed portion was peeled off together with the 
film, while the unexposed portion was transferred onto the aluminum plate. 
The aluminum plate was overall exposed to a ultraviolet light to harden 
the remaining unexposed portion. The thus obtained printing plate was set 
to a Heidelberg GTO printing machine to make a run of printing, whereby 
more than 100,000 good print copies were obtained. 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. Further, the aluminum plate was immersed for two minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for desmut treatment, 
and then anodized in an aqueous 20% phosphoric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 20 
mmg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
Example 10 
On a subbed polyethylene terephthalate film of 10 .mu.m in thickness was 
coated the following light-sensitive composition so as to have a dry 
thickness of 2 .mu.m. 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 50 parts 
TMPTA (trimethylolpropane triacrylate, produced by Shin-Nakamura Kagaku 
K.K.) 100 parts 
3-(2'-Benzimidazoyl)-7-dimethylaminocoumarin 5 parts 
3,3',4,4'-Tetra(t-butylperoxycarbonyl)benzophenone 5 parts 
Methyl cellosolve 1000 parts 
An aluminum plate that was subjected to electrolytic etching treatment in a 
nitric acid solution under the following conditions was laminated with the 
above composition under a pressure of 3 kg/m.sup.2. The aluminum plate was 
then exposed to an argon laser light of 488 nm located on the polyethylene 
terephthalate film side. The exposed aluminum plated was let pass between 
a pair of juxtaposed rollers having a pressure of 3 kg/m.sup.2. The 
polyethylene terephthalate film was removed together with the exposed 
portion from the aluminum plate, and the unexposed portion remained on the 
aluminum plate. The aluminum plate was overall exposed to a ultraviolet 
light to harden the remaining unexposed portion. The thus obtained 
printing plate was set to a Heidelberg GTO printing machine to make a run 
of printing, whereby more than 100,000 print copies were obtained. 
Electrolytic etching conditions 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. Next, the aluminum plate was immersed for two minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for desmut treatment, 
and then anodized in an aqueous 20% phosphoric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 20 
mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.01% polyvinylsulfonic acid solution at 90.degree. C., washed, 
and then dried. 
Example 11 
Butyl acrylate-ethyl acrylate-maleic anhydride copolymer 80 parts 
Superclon CPE907LTA (chlorinated polyolefin, produced by Sanyo Kokusaku 
Pulp) 20 parts 
Dipentaerythritol hexaacrylate 60 parts 
Pentaerythritol/terephthalic acid/acrylate (2:1:7) 60 parts 
Cationic dye-borate complex (Compound IR-1) 1 part 
Tetrabutylammoniumbutyltriphenyl borate 3 parts 
Methyl cellosolve 1000 parts 
The above composition was laminated under a pressure of 3 kg/m.sup.2 upon 
an aluminum plate that was subjected to nitric acid/electrolytic etching 
treatment under the following conditions. Next, the laminated aluminum 
plate was exposed to a 830 nm semiconductor laser light that was located 
on the polyethylene terephthalate film side. The exposed aluminum plate 
was let pass between a pair of juxtaposed pressure rollers heated to 
80.degree. C. and having a pressure of 3 kg/m.sup.2. The polyethylene 
terephthalate film was peeled off together with the exposed portion, and 
the unexposed portion remained on the aluminum plate. The aluminum plate 
was overall exposed to a ultraviolet light to harden the remaining 
unexposed portion. The thus obtained printing plate was set to a 
Heidelberg GTO printing machine to make a run of printing, whereby more 
than 100,000 good print copies were obtained. 
Electrolytic etching conditions 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution with a quantity of 
anode electricity of 100 coulomb/dm.sup.2 per hour. When the surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. Next, the aluminum plate was immersed for two minutes in an 
aqueous sulfuric acid solution at 55.degree. C. for desmut treatment, and 
then anodized in an aqueous 20% phosphoric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 20 
mg/dm.sup.2. The obtained aluminum supprot was immersed for 10 seconds in 
an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
Example 12 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution. When the surface 
roughness was measured, the aluminum plate had a surface roughness Ra of 
0.3 .mu.m. Next, the aluminum plate was immersed for two minutes in an 
aqueous 30% sulfuric acid solution at 55.degree. C. for desmut treatment, 
and then anodized in an aqueous 20% sulfuric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 25 
mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
Example 13 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush, and then immersed for 10 seconds in an aqueous 10% sodium 
hydroxide solution for surface etching treatment. Subsequently, the 
aluminum plate was subjected to electrolytic etching treatment in an 
aqueous 1% nitric acid solution with a quantity of anode electricity of 80 
coulomb/dm.sup.2 per hour. When the treated surface roughness was 
measured, the aluminum plate had a surface roughness Ra of 0.4 .mu.m. 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution. When the treated 
surface roughness was measured, the aluminum plate had a surface roughness 
Ra of 0.3 .mu.m. Next, the aluminum plate was immersed for two minutes in 
an aqueous 30% sulfuric acid solution at 55.degree. C. for desmut 
treatment, and then anodized in an aqueous 20% phosphoric acid solution at 
a current density of 2.5 A/dm.sup.2 so as to have an anodized coat weight 
of 25 mg/dm.sup.2. The obtained aluminum support was immersed for 10 
seconds in an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. 
C., washed, and then dried. 
Example 15 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush, and then immersed for 10 seconds in an aqueous 10% sodium 
hydroxide solution at 30.degree. C. for surface etchin treatment. Next, 
the aluminum plate was subjected to electrolytic etching treatment in an 
aqueous 1% nitric acid solution with a quantity of anode electricity of 80 
coulomb/dm.sup.2 per hour. When the etched surface roughness was measured, 
the aluminum plate had a surface roughness Ra of 0.4 .mu.m. 
Comparative Example 1 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminu plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution. When the etched 
surface roughness was measured, the aluminum plate had a surface roughness 
Ra of 0.4 .mu.m. After that, the aluminum plate was immersed for two 
minutes in an aqueous 30% sulfuric acid solution at 55.degree. C. for 
desmut treatment, and then anodized in an aqueous 20% sulfuric acid 
solution at a current density of 2.5 A/dm.sup.2 so as to have an anodized 
coat weight of 25 mg/dm.sup.2. The obtained aluminum support was immersed 
for 10 seconds in an aqueous 0.01% polyvinylsulfonic acid solution at 
90.degree. C., washed, and then dried. 
Comparative Example 2 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was grained by using a stainless 
wire brush, and then immersed for 10 seconds in an aqueous 10% sodium 
hydroxide solution at 30.degree. C. for surface etching treatment. When 
the treated surface roughness was measured, the aluminum plate had a 
surface roughness Ra of 0.4 .mu.m. 
Comparative Example 3 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution. When the etched 
surface roughness was measured, the aluminum plate had a surface roughness 
Ra of 0.8 .mu.m. After that, the aluminum plate was immersed for two 
minutes in an aqueous 30% sulfuric acid solution at 55.degree. C. for 
desmut treatment, and then anodized in an aqueous 20% phosphoric acid 
solution at a current density of 2.5 A/dm.sup.2 so as to have an anodized 
coat weight of 25 mg/dm.sup.2. The obtained aluminum support was immersed 
for 10 seconds in an aqueous 0.01% carboxymethyl cellulose solution at 
90.degree. C., washed, and then dried. 
Comparative Example 4 
The light-sensitive layer of Example 1 was used to form an image in the 
same manner as in Example 1 on an aluminum support that was prepared under 
the following conditions. 
An aluminum plate of 0.3 mm in thickness was subjected to electrolytic 
etching treatment in an aqueous 1% nitric acid solution. When the etched 
surface roughness was measured, the aluminum plate had a surface roughness 
Ra of 0.4 .mu.m. Next, the aluminum plate was immersed for two minutes in 
an aqueous sulfuric acid solution at 55.degree. C. for desmut treatment, 
and then anodized in an aqueous 20% phosphoric acid solution at a current 
density of 2.5 A/dm.sup.2 so as to have an anodized coat weight of 3 
mg/dm.sup.2. The obtained aluminum support was immersed for 10 seconds in 
an aqueous 0.01% carboxymethyl cellulose solution at 90.degree. C., 
washed, and then dried. 
The test results of the aluminum supports obtained in the above Examples 12 
to 15 and Comparative Examples 1 to 4 are shown below, wherein data of 
their physical properties are shown in Table 1, and their image formation 
evaluation results in Table 2. 
TABLE 1 
______________________________________ 
Surface 
roughness Anodizing 
(.mu.m) Peak AD weight 
(Ra) (Rmax) count Bath condition 
(mg/dm.sup.2) 
______________________________________ 
Example 12 
0.3 3.2 0.1 Sulfuric acid 
25 
Example 13 
0.4 3.8 0.4 Phosphoric acid 
20 
Example 14 
0.4 4.2 0.3 Phosphoric acid 
20 
Example 15 
0.4 3.8 0.4 Phosphoric acid 
20 
Comp. 0.4 4.5 0.3 Sulfuric acid 
25 
ex. 1 
Comp. 0.4 4.8 150 Sulfuric acid 
25 
ex. 2 
Comp. 0.8 6.5 450 Sulfuric acid 
25 
ex. 3 
Comp. 0.4 4.2 0.1 Phosphoric acid 
3 
ex. 4 
______________________________________ 
TABLE 2 
______________________________________ 
Halftone Number 
Printing 
reproduc- Transfer of 
durability 
ibility uniformity 
pinholes 
______________________________________ 
Example 12 
150,000 2-98% .+-.2% 5 or less 
Example 13 
300,000 2-98% .+-.2% 5 or less 
Example 14 
200,000 2-98% .+-.2% 5 or less 
Example 15 
200,000 2-98% .+-.2% 5 or less 
Comp. ex. 1 
70,000 2-98% .+-.2% 5 or less 
Comp. ex. 2 
150,000 5-95% .+-.5% 30 
Comp. ex. 3 
150,000 5-95% .+-.5% 100 
Comp. ex. 4 
50,000 2-98% .+-.2% 5 or less 
______________________________________ 
The evaluation criteria in Table 2 are as follows: 
Printing durability: In printing on sheets of fine paper by using a 
Heidelberg printing machine, the number of print copies until when the 
density drop begins to appear in the solid density area. 
Halftone reproducibility: The reproducibility of an image that was formed 
on the aluminum plate after exposing the aluminum plate through a 175 
lines/inch haltone dot original image. 
Transfer uniformity: Difference between the mininum density and the maximum 
density of an image that was formed on the aluminum plate by exposing the 
aluminum plate through an A2-size 150 lines/inch 50% screen tint film. 
Pinholes: The number of pinholes found in 1 mm.sup.2 visual field by using 
a 25-power magnifying glass. 
As has been mentioned, it is understood that the printing plate obtained 
according to the method of the invention has a high resolution, is 
excellent in the printing durability as well as in the image uniformity, 
and has few pinholes.