Aluminum alloy support for planographic printing plate

Disclosed is an aluminum alloy support for a planographic printing plate, wherein the sodium content of the support is 0.005 to 0.040 weight %.

FIELD OF THE INVENTION 
The invention relates to an aluminum alloy support for a planographic 
printing plate. 
BACKGROUND OF THE INVENTION 
As a support for a planographic printing plate, a plate made of pure 
aluminum or an aluminum alloy has been so far used. As the aluminum alloy 
are used various aluminum alloys containing silicon, copper, manganese, 
magnesium, chromium, zinc, lead, bismuth, nickel, titanium, sodium or 
iron. Generally, an aluminum alloy rolled plate with a thickness of 0.1 to 
0.5 mm according to JIS Standard A1050 or A1100 is used. Such an aluminum 
alloy rolled plate is surface roughened by a mechanical method, an 
electrochemical method, a chemical method or a combination thereof, and 
then anodized to obtain a support for a printing plate. 
The thus obtained aluminum alloy support, which has been surface roughened, 
is required to have a uniformly roughened surface without unevenness, 
defects or streaks in a direction of rolling. The unevenness or defects 
are likely to cause stains on the support surface due to ink acceptance at 
printing. In order to remove such unevenness or defects, there have been 
proposed an aluminum alloy support with a specific content of Fe, Sn, In, 
Ga and Zn, a specific surface roughness and a specific pit size as 
disclosed in JP-A-58-209597, an aluminum alloy support with a specific 
content of Mn and Si as disclosed in JP-A-60-230951, an aluminum alloy 
support with a specific content of Mn and Si subjected to a specific heat 
treatment as disclosed in JP-A-62-80255, an aluminum alloy support with a 
specific content of Mg and Mn, and with a specific crystal particle width 
as disclosed in JP-A-62-86143, an aluminum alloy support with a specific 
content of Si, Fe, Mn and Cu as disclosed in JP-A-1-306288, an aluminum 
alloy support with a specific content of Mg, Si, and Cu as disclosed in 
JP-A-1-61293, and an aluminum alloy support with a specific content of Si, 
Fe, Cu, Ga, Ni, and Ti as disclosed in JP-A-3-177528. However, any 
proposal cannot sufficiently prevent occurrence of stains on the support 
caused due to ink acceptance. 
SUMMARY OF THE INVENTION 
The present invention has been made in order to solve the problems 
described above. An object of the invention is to provide an aluminum 
alloy support for a planographic printing plate, which prevents stains 
occurred on the support due to unevenness or defects (or at non-image 
portions of prints), or minute spots (stop dirtiness) occurred on the 
support (or at non-image portions of prints) at resumption of a print run. 
DETAILED DESCRIPTION OF THE INVENTION 
The above objects of the invention can be attained by the following: 
1. an aluminum alloy support for a planographic printing plate, wherein the 
sodium content of the support is 0.005 to 0.040 weight %, 
2. the aluminum alloy support of item 1 above, wherein the total content of 
sodium and zinc in the support is 0.01 to 0.040 weight %, 
3. a presensitized planographic printing plate comprising a support and 
provided thereon, a light sensitive layer, wherein the support is an 
aluminum alloy support having a sodium content of 0.005 to 0.040 weight %, 
4. the presensitized planographic printing plate of item 3, wherein the 
support is an aluminum alloy support having the total content of sodium 
and zinc of 0.01 to 0.040 weight %, 
5. the presensitized planographic printing plate of item 3, wherein the 
light sensitive layer contains an alkali soluble resin and an 
o-quinonediazide compound, 
6. the presensitized planographic printing plate of item 5, wherein the 
light sensitive layer contains the alkali soluble resin in an amount of 5 
to 90% by weight and the o-quinonediazide compound in an amount of 6 to 
60% by weight, 
7. the presensitized planographic printing plate of item 5, wherein the 
o-quinonediazide compound is an ester compound of o-naphthoquinonediazide 
sulfonic acid and a polycondensate resin of phenols with aldehydes or 
ketones, 
8. the presensitized planographic printing plate of item 5, wherein the dry 
coating amount of the light sensitive layer is 0.2 to 10 g/m.sup.2, 
9. the presensitized planographic printing plate of item 3, wherein the 
support has a thickness of 0.10 to 0.50 mm, or 
10. the presensitized planographic printing plate of item 5, wherein the 
support is subjected to roughening treatment and anodizing treatment. 
The present inventors have made an extensive study on an aluminum alloy 
support for a planographic printing plate. As a result, the present 
inventors have found that the aluminum alloy support having a sodium 
content of 0.005 to 0.040 weight % can prevent occurrence of stains on the 
support and attained the present invention. The present invention further 
provides a surprising effect that minimizes occurrence of stop dirtiness 
after printing is started, stopped to rest or register for a while, and 
then restarted. 
The present invention will be explained below. 
The aluminum alloy support of the invention for a planographic printing 
plate contains sodium in an amount 0.005 to 0.040 weight %. 
The aluminum alloy support of the invention may inevitably contain 
impurities other than sodium. The content of such impurities is, for 
example, the content as shown in JIS Standard A1050 (not more than 0.25 
weight % of Si, not more than 0.40 weight % of Fe, not more than 0.05 
weight % of Cu, not more than 0.05 weight % of Mn, not more than 0.05 
weight % of Mg, not more than 0.05 weight % of Zn, not more than 0.03 
weight % of Ti). Impurities at such contents can still attain the object 
of the invention. 
The reason that the sodium content described above prevents occurrence of 
stains or stop dirtiness on the printing plate support is not apparent, 
but is considered to be as follows: 
Most other metals, which may be contained in the aluminum alloy support in 
minute quantities, are chemically stable compared with aluminum, and 
therefore, the relatively unstable aluminum is likely to be corroded. 
Aluminum is the main element in the aluminum alloy support, and once the 
corrosion continuously proceeds, unevenness or defects on the surface are 
likely to occur. Such defects have a higher pit depth/pit size ratio as 
compared with hemispherical pits obtained by electrolytic roughening of 
the surface, and therefore, easily accept contamination. 
When a metal more chemically unstable than aluminum is hradded, corrosion 
of the metal precedes. When the content of such a metal is reduced to an 
infinitesimal amount, corrosion of the aluminum alloy can be minimized. 
Accordingly, a minute amount of sodium in the aluminum alloy support is 
distributed at a minute quantity in the support, and preceding corrosion 
of the sodium produces only a minimal size of unevenness or defects which 
has no adverse effect on printing properties, for example, the properties 
preventing stain occurrence or stop dirtiness occurrence. In the 
invention, the minute amount of sodium in the aluminum alloy support is 
considered to minimize unevenness or defects on the support surface and 
show the advantageous effects of the invention preventing stain occurrence 
or stop dirtiness occurrence. 
Mechanism of the occurrence of stop dirtiness is not clear, but is 
considered to be as follows: 
When printing is stopped, the planographic printing plate dries since 
dampening water is not supplied thereto. The dried plate, which has a 
support surface with unevenness or defects or a surface with non-uniform 
wettability, results in ink aggregation, and at resumption of a print run, 
brings about occurrence of stop dirtiness. 
In the invention, the sodium content of the aluminum alloy support is 0.005 
to 0.040 weight %, and preferably 0.010 to 0.020 weight %. 
The aluminum alloy support of the invention for a planographic printing 
plate and a manufacturing method of a presensitized planographic printing 
plate employing the support will be explained below. 
Aluminum alloy having a composition as described above is melted and molded 
according to conventional methods. As a molding method, a semi-continuous 
molding method (DC molding method) is generally used, but a thin plate 
continuous molding method (a continuous molding rolling method) may be 
used in view of energy saving or mechanical strength improvement. The 
resulting ingot is uniformized, hot rolled, cold rolled, and optionally 
annealed to obtain a plate having a thickness of preferably 0.10 to 0.50 
mm, and more preferably 0.20 to 0.3 mm. 
Uniformizing carried out after molding is necessary to decrease the size of 
minute recrystallization particles produced during annealing, and in 
uniformizing, the molded ingot is suitably maintained at 450 to 
610.degree. C. for 1 to 48 hours. Heat for uniformizing and heat for hot 
rolling need not be applied separately, but heat for uniformizing and for 
hot rolling may be applied at the same temperature, immediately followed 
by hot rolling. In either case, the temperature of heat application for 
hot rolling is 400 to 550.degree. C. at the initial stage. 
After hot rolling, the ingot is cold rolled to obtain a plate with a 
predetermined thickness, but the ingot is ordinarily annealed once or 
twice immediately after hot rolling or during cold rolling. The annealing 
temperature is suitably 300 to 600.degree. C. When the annealing 
temperature is less than 300.degree. C., the ingot is not completely 
recrystallized, and when the annealing temperature exceeds 600.degree. C., 
the surface oxidation is serious, resulting in a disadvantageous increased 
size of the recrystallization particles. 
The thus obtained aluminum alloy plate is preferably subjected to 
degreasing treatment for removing rolling oil on the surface, prior to 
roughening. The degreasing treatment to be used includes one employing a 
solvent such as trichlene or thinner, and emulsion degreasing treatment 
employing an emulsion such as kerosene and triethanol. It is also possible 
to use an aqueous solution containing alkali such as caustic soda for the 
degreasing treatment. When alkali aqueous solution such as caustic soda is 
used for the degreasing treatment, it is possible to remove even a stain 
and oxide film which can not be removed by aforesaid degreasing treatment 
alone. When an aqueous solution containing alkali such as caustic soda is 
used for the degreasing treatment, smut is caused on the surface of a 
support. In this case, it is preferable to perform desmutting treatment by 
dipping in an acid such as phosphoric acid, nitric acid, sulfuric acid and 
chromic acid, or in mixed acid thereof. 
The aluminum alloy plate is followed by roughening treatment to give a 
uniformly roughened surface. The roughening method includes a mechanically 
roughening method such as a wire graining or brush graining method 
employing a rotating metal wire in a roll form or a rotating nylon brush, 
or a blast graining method jetting an abrasive onto the plate surface, an 
electrolytic roughening method, so-called electrolytic graining, a 
combination thereof, or a roughening method interposing therebetween a 
relatively strong chemical roughening. 
In the invention, electrolytic roughening is preferable. For example, 
electrolytic roughening is carried out in a 1 to 10 weight % hydrochloric 
acid solution at 5 to 50.degree. C., at 20 to 100 A/dm.sup.2 of current 
density and a quantity of electricity of 100 to 800 C/dm.sup.2. The 
electrolytic roughening plate is chemically treated with an acid or alkali 
to remove smut produced during electrolytic roughening. The acid includes 
sulfuric acid, persulfuric acid, fluoric acid, phosphoric acid, nitric 
acid and hydrochloric acid, and the alkali includes sodium hydroxide and 
potassium hydroxide. When the above roughening is carried out employing an 
aqueous alkali solution, smut is caused on the surface of the support. In 
this case, it is preferable to perform desmutting treatment by dipping in 
an acid such as phosphoric acid, nitric acid, sulfuric acid and chromic 
acid, or in mixed acid thereof. 
After the roughening treatment, a conventional anodizing treatment is 
carried out. Direct current is supplied to the resulting aluminum plate in 
an aqueous solution containing sulfuric acid, phosphoric acid, chromic 
acid, oxalic acid, sulfamic acid or a combination thereof to form an 
anodized oxide film on the surface of the plate. The anodizing conditions 
vary depending on the electrolytic solution used, but the plate is 
generally anodized in an 1-50 weight % electrolyte solution at 5 to 
50.degree. C. for 1 to 100 seconds, at a current density of 2 to 10 
A/m.sup.2 and a voltage of 5 to 50 V to give an oxide film of 0.5 to 5 
g/m.sup.2. In the anodizing treatment, an electrolyte solution containing 
sulfuric acid or phosphoric acid is generally used. 
The anodized aluminum alloy support may be further provided with a 
hydrophilic property. A hydrophilic property providing method includes a 
method of employing an alkali metal silicate (for example, an aqueous 
sodium silicate solution) disclosed in U.S. Pat. Nos. 2,714,066, 
3,181,461, 3,280,734 and 3,902,734, a method of employing potassium 
zirconium fluoride disclosed in JP-B-36-22063, a method of employing 
polyvinyl sulfonic acid disclosed in U.S. Pat. Nos. 3,276,868, 4,153,416 
and 4,689,272, a method of providing a subbing layer comprised of a 
hydrophilic resin and a water soluble salt on the support as disclosed in 
JP-A-56-21126, a method of providing a subbing layer comprised of a 
hydrophilic resin and an carboxylic acid salt on the support as disclosed 
in JP-A-64-14090, a method of providing, on the support, a hydrophilic 
layer containing at least one selected from compounds having an amino 
group and one of a carboxylic acid group and a sulfonic acid group, and 
salts thereof as disclosed in JP-A-63-130391, and a method of providing, 
on the support, a hydrophilic layer containing at least one selected from 
compounds having an amino group and a phosphone group, and salts thereof 
as disclosed in JP-A-63-165183. 
On the aluminum alloy support of the invention for a planographic printing 
plate, a conventional light sensitive composition is provided to form a 
light sensitive layer. Thus, a presensitized planographic printing plate 
is obtained. The planographic printing plate obtained from this 
presensitized planographic printing plate has superior properties. 
The light sensitive composition for the light sensitive layer is, for 
example, as follows: 
(o-Quinonediazide Compound) 
The o-quinonediazide compound includes an ester compound of 
o-naphthoquinonediazide sulfonic acid and a polycondensate resin of 
phenols with aldehydes or ketones. 
Examples of the phenols include a monohydric phenol such as phenol, 
o-cresol, m-cresol, p-cresol, 3,5-xylenol, carvacrol and thymol, a 
dihydric phenol such as catechol, resorcin or hydroquinone, and a 
trihydric phenol such as pyrogallol or phloroglucin. Examples of the 
aldehydes include formaldehyde, benzaldehyde, acetaldehyde, crotonaldehyde 
and furfural. Preferred are formaldehyde and benzaldehyde. Examples of the 
ketones include acetone, and methyl ethyl ketone. 
The polycondensate resin includes a phenol-formaldehyde resin, a 
m-cresol-formaldehyde resin, a mixed m- and p-cresol-formaldehyde resin, a 
resorcin-benzaldehyde resin, and a pyrogallol-acetone resin. 
In the o-naphthoquinonediazide compound, the condensation ratio of the 
o-naphthoquinonediazide sulfonic acid to the hydroxyl group of the phenol 
component is 15 to 80 mol %, and preferably 20 to 45 mol %. 
The o-quinonediazide compound used in the invention include those disclosed 
in Japanese Patent O.P.I. Publication No. 58-43451. The examples thereof 
include conventional 1,2-quinonediazide compounds such as 
1,2-benzoquinonediazide-sulfonate, 1,2-benzoquinonediazidesulfonamide, 
1,2-naphthoquinonediazide-sulfonate and 
1,2-naphthoquinonediazide-sulfonamide and, further, include 
1,2-quinonediazide compounds such as 1,2-benzoquinonediazide-4-sulfonic 
acid phenyl ester, 1,2,1',2'-di- 
(benzoquinonediazide-4-sulfonyl)dihydroxybiphenyl, 
1,2-benzoquinonediazide-4-(N-ethyl-N-.beta.-naphthyl)sulfonamide, 
1,2-naphthoquinonediazide-5-sulfonic acid cyclohexyl ester, 
1-(1,2-naphthoquinonediazide-5-sulfonyl)-3,5-dimethylpyrazole, 
1,2-naphthoquinonediazide-5-sulfonic 
acid-4'-hydroxydiphenyl-4'-azo-.beta.-naphthol ester, 
N,N-di-(1,2-naphthoquinonediazide-5-sulfonyl)-aniline, 
2'-(1,2-naphthoquinonediazide-5-sulfonyloxy)-1-hydroxy-anthraquinone, 
1,2-naphthoquinonediazide-5-sulfonic acid-2,4-dibydroxybenzophenone ester, 
1,2-naphthoquinonediazide-5-sulfonic acid-2,3,4-trihydroxybenzophenone 
ester, a condensation product of 2 moles of 
1,2-naphthoquinonediazide-5-sulfonic acid chloride with 1 mole of 
4,4'-diaminobenzophenone, a condensation product of 2 moles of 
1,2-naphthoquinonediazide-5-sulfonic acid chloride with 1 mole of 
4,4'-dihydroxy-1,1'-diphenylsulfone, a condensation product between 1 mole 
of 1,2-naphthoquinonediazide-5-sulfonic acid chloride and 1 mole of 
purpurogallin, and 
1,2-naphthoquinonediazide-5-(N-dihydroxyabiethyl)-sulfonamide described in 
J. Kosar, Light-Sensitive Systems, John Wily & Sons, New York, pp. 339-352 
(1965) and W S. De Forest, Photoresist, Vol. 50, McGraw-Hill, New York 
(1975). Other examples are 1,2-naphthoquinonediazide compounds described 
in Japanese Pat. Exam. Pub. Nos. 37-1953, 37-3627, 37/13109, 40/26126, 
40/3801, 45/5604, 45/27345 and 51/13013, and Japanese Pat. O.P.I. Pub. 
Nos. 48/96575, 48/63802 and 48/63803. 
Among the above described o-quinonediazide compounds is especially 
preferable an o-quinonediazide ester compound obtained by reacting 
1,2-benzoquinonediazide sulfonylchloride or 1,2-naphthoquinonediazide 
sulfonylchloride with a pyrogallol-acetone resin or 
2,3,4-trihydroxybenzophenone. 
In the invention, the o-quinonediazide compound may be used singly or in 
combination. 
The light sensitive layer containing an o-quinonediazide compound 
preferably contains an alkali soluble resin. The alkali soluble resin 
includes a novolak resin, a vinyl polymer having a phenolic hydroxy group, 
and a polycondensate of polyhydric phenol with aldehyde or ketone 
disclosed in Japanese Patent O.P.I. Publication No. 55-57841. The alkali 
soluble resin is contained in the light sensitive layer in an amount of 
preferably 5 to 90% by weight. 
The above novolak resin includes a phenol-formaldehyde resin, a 
cresol-formaldehyde resin, a phenol-cresol-formaldehyde resin disclosed in 
Japanese Patent O.P.I. Publication No. 55-57841, and a copolycondensate of 
a p-substituted phenol, and phenol or cresol with formaldehyde disclosed 
in Japanese Patent O.P.I. Publication No. 55-127553. 
The novolak resin has a number average molecular weight (Mn) of preferably 
3.00.times.10.sup.2 to 7.50.times.10.sup.3, more preferably 
5.00.times.10.sup.2 to 4.00.times.10.sup.3, and a weight average molecular 
weight (Mw) of preferably 1.00.times.10.sup.3 to 3.00.times.10.sup.4, more 
preferably 3.00.times.10.sup.3 to 2.00.times.10.sup.4, in terms of 
polystyrene standard. The above novolak resin may be used singly or in 
combination. The novolak resin content of the light sensitive layer is 
preferably 5 to 85% by weight. 
The o-quinonediazide compound content of the light sensitive layer is 
preferably 6 to 60% by weight, and more preferably 10 to 50% by weight. 
The light sensitive layer containing o-quinonediazide compounds optionally 
contains a plasticizer, a surfactant, an organic acid or an acid 
anhydride. The light sensitive layer can further contain a lipophilic 
agent such as a p-tert-butylphenol formaldehyde resin, a p-n-octylphenol 
formaldehyde resin or an ester resin thereof partially esterified with an 
o-quinonediazide compound in order to increase the lipophilicity of the 
light sensitive layer. 
The light sensitive layer can further contain various additives other than 
those described above, for example, alkylethers (such as ethylcellulose or 
methylcellulose), a fluorine-containing surfactant, a nonioic surfactant 
(such as Pluronic L-64 produced by Asahidenka Co., Ltd.), a plasticizer 
for giving flexibility or antiabrasion to the coated layer (such as 
butylphthalate, polyethylene glycol, tributylcitrate, diethylphthalate, 
dibutylphthalate, dihexylphthalate, dioctylphthalate, tricresyl phosphate, 
tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryloleate, an 
oligomer or polymer of acrylic acid or methacrylic acid), an lipophilic 
agent for improving a lipophilicity of image portions (such as an alcohol 
half ester of styrene-maleic anhydride copolymer disclosed in Japanese 
Patent O.P.I. Publication No. 55-527/1980), a stabilizing agent (such as 
phosphoric acid, phosphorous acid, an organic acid, for example, citric 
acid, oxalic acid, benzenesulfonic acid, naphthalene sulfonic acid, 
4-methoxy-2-hydroxybenzophenone-5-sulfonic acid, glutaric acid), a 
development accelerator (such as higher alcohols or acid anhydrides). The 
content of these additives is generally 0.01 to 30 weight % based on the 
total solid component weight of the light sensitive layer, although it 
varies depending on the objects of the usage. 
The presensitized lithographic printing plate in the invention is prepared 
by dissolving the components described above in a solvent to obtain a 
coating solution, coating the solution on the aluminum alloy support of 
the invention and then drying the coated to form a light sensitive layer 
on the support. 
The solvent includes methylcellosolve, methylcellosolve acetate, 
ethylcellosolve, ethylcellosolve acetate, diethylene glycol 
monomethylether, diethylene glycol monoethylether, diethylene glycol 
dimethylether, diethylene glycol methylethylether, diethylene glycol 
diethylether, diethylene glycol monoisopropylether, propylene glycol, 
propylene glycol monoethylether acetate, propylene glycol monobutylether, 
dipropylene glycol monomethylether, dipropylene glycol dimethylether, 
dipropylene glycol methylethylether, ethyl formate, propyl formate, butyl 
formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, 
butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl 
butyrate, dimethylformamide, dimethylsulfoxide, dioxane, acetone, 
methylethylketone, cyclohexanone, methylcyclohexanone, discetonealcohol, 
acetylacetone, .gamma.-butyrolactone. These solvents can be used singly or 
in combination. 
The coating method for coating the light sensitive layer on a support 
includes a conventional coating method such as whirl coating, wire bar 
coating, dip coating, air-knife coating, roll coating, blade coating or 
curtain coating. The solid component concentration of the light sensitive 
layer coating solution is preferably 1 to 50 weight %. The coating amount 
of the light sensitive layer is preferably 0.2 to 10.0 g/m.sup.2, and more 
preferably 1.0 to 3.0 g/m.sup.2, as a solid. 
A backing layer (also called a back coat layer) containing metal oxides 
obtained by hydrolyzing or polycondensating organic or inorganic metal 
compounds is preferably provided on the surface of the aluminum alloy 
support of the invention opposite the light sensitive layer whereby an 
anodized aluminum oxide dissolution in developer is minimized. 
The coating amount of the backing layer may be any, as long as it prevents 
from dissolving the aluminum in the developer. The coating amount of the 
backing layer is preferably 0.001 to 10 g m.sup.2, more preferably 0.01 to 
1 g/m.sup.2, and still more preferably 0.02 to 0.1 g/m.sup.2. 
The backing layer can be coated on the surface of the support opposite the 
light sensitive layer according to various coating methods. In order to 
obtain the above described coating amount, the most preferable coating 
method is a method including preparing a backing layer coating solution, 
coating the solution on a support and drying. 
The presensitized planographic printing plate is imagewise exposed to light 
through a transparent original having a line image or a dot image. The 
light source for exposure includes a carbon arc lamp, a mercury lamp, a 
xenon lamp, a metal halide lamp and strobe. 
The exposed plate is developed with developer, washed with water or a 
rising solution, optionally gummed with a gumming solution, and dried to 
obtain a planographic printing plate for printing. The planographic 
printing plate is mounted on a printing machine and printing is carried 
out. 
The developer used in the invention is preferably an aqueous alkaline 
solution. The alkali of the developer includes an alkali metal silicate 
such as potassium silicate, sodium silicate, sodium metasilicate, 
potassium metasilicate, or ammonium silicate, an inorganic alkali such as 
potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium tertiary 
phosphate, sodium secondary phosphate, potassium tertiary phosphate, 
potassium secondary phosphate, ammonium tertiary phosphate, ammonium 
secondary phosphate, sodium bicarbonate, sodium carbonate, potassium 
carbonate, or ammonium carbonate, and an organic alkali such as 
monoethanol amine, diethanol amine, triethanol amine, or a tetraalkyl 
ammonium hydroxide. Preferred among these alkalis is the alkali metal 
silicate. The developer contains the alkali in an amount of preferably 0.3 
to 10 weight %, and water in an amount of preferably not less than 50 
weight %. The developer is especially preferably an aqueous solution 
having an alkali silicate content of 0.3 to 10 weight % in which the 
silicon dioxide (SiO.sub.2) content of the silicate is 0.1 to 7.0 weight 
%. 
The developer in the invention optionally contains other additives such as 
an organic acid, an anionic, nonionic or cationic surfactant, an organic 
solvent and a reducing agent.

The invention will be detailed in the following examples, but is not 
limited thereto. 
EXAMPLE 1 
(Preparation of Presensitized Planographic Printing Plate 1) 
The aluminum alloy having the composition as shown in Table 1 was melted 
and molded according to a semi-continuous molding method to produce ingot 
having a size of 400 mm.times.1000 mm.times.3000 mm. Ten mm were removed 
from each surface of the ingot. The resulting ingot was uniformized at 
550.degree. C. for 6 hours, hot rolled to obtain a 5 mm thick plate, and 
cold rolled to obtain a 1.5 mm thick plate. The resulting plate was batch 
annealed at 400.degree. C. for 2 hours, and finally cold rolled to obtain 
an aluminum alloy plate support having a thickness of 0.3 mm. 
The resulting support was dipped for 30 seconds in a 10% sodium hydroxide 
aqueous solution kept at 85.degree. C. to degrease, and then washed with 
water. The resulting aluminum plate was dipped for 1 minute in a 10% 
sulfuric acid aqueous solution kept at 25.degree. C. to desmut, and then 
washed with water. The resulting aluminum plate was electrolytically 
etched in 1.5% nitric acid aqueous solution for 30 seconds at 30.degree. 
C. at a current density of 60 A/dm.sup.2, employing a 50 Hz sine wave 
alternate current. The etched plate was dipped for 10 seconds in a 10% 
sodium hydroxide aqueous solution at 60.degree. C., then dipped for 20 
seconds in a 10% sulfuric acid aqueous solution kept at 25.degree. C. to 
desmut, and then washed with water. The resulting plate was anodized for 
60 seconds in a 20% sulfuric acid aqueous solution at 35.degree. C. at a 
current density of 3 A/dm.sup.2, and then washed with water. Thus, support 
1 was obtained. 
The following light sensitive composition coating solution was coated on 
the surface of the support 1 by a wire bar, and then dried for 2 minutes 
at 80.degree. C. to give a light sensitive layer having a dry thickness of 
2.0 g/m.sup.2. Thus, a presensitized planographic printing plate 1 was 
obtained. presensitized planographic printing plate 2 to 4 were prepared 
in the same manner as in presensitized planographic printing plate 1, 
except that aluminum alloy supports 2 to 4 as shown in Table 1 were used. 
______________________________________ 
Novolak resin (phenol/m-cresol/p-cresol, 10/54/36, mol ratio), 
6.70 g 
Mw: 4,000) 
Condensation product (esterification rate: 30%) of a pyro- 
1.50 g 
gallol-acetone resin (Mw: 3,000) with o-naphthoquinone 
diazide-5-sulfonylchloride 
Polyethylene glycol #2,000 0.20 g 
Victoria Pure Blue BOH (made by Hodogaya Kagaku Co., 
0.08 g 
Ltd.) 
2,4-Bis(trichloromethyl)-6-(p-methoxystyryl)-s- 
0.15 g 
triazine 
FC-430 (made by Sumitomo 3M Co., Ltd.) 
0.03 g 
Cis-1,2-Cyclohexanedicarboxylic acid 
0.02 g 
Methyl cellosolve 100 ml 
______________________________________ 
TABLE 1 
__________________________________________________________________________ 
Presensi- 
tized Alumi- 
plano- 
num 
graphic 
alloy 
printing 
support 
Composition (weight %) of the support 
Re- 
plate No. 
No. Na Fe Cu Mn Mg Zn Ti Ga marks 
__________________________________________________________________________ 
1 1 0.013 
0.233 
0.021 
0.004 
0.004 
0.005 
0.028 
0.009 
Inv. 
2 2 0.026 
0.304 
0.008 
0.011 
0.010 
0.007 
0.009 
0.011 
Inv. 
3 3 0.052 
0.314 
0.015 
0.007 
0.005 
0.003 
0.007 
0.011 
Comp. 
4 4 0.000 
0.692 
0.303 
0.003 
0.005 
0.011 
0.009 
0.030 
Comp. 
__________________________________________________________________________ 
Inv.: Invention 
Comp.: Comparative 
Each of the presensitized planographic printing plates obtained above was 
cut to 80.times.60 cm, and exposed at 8 mw/cm.sup.2 for 60 seconds 
employing a 4 kw metal halide lamp. The exposed plate was then developed 
at 30.degree. C. for 40 seconds employing a developer obtained by diluting 
a commercially available developer SDR-1 (made by Konica Corporation) with 
water at a factor of 6 to obtain a positive-working printing plate for a 
print run. The resulting printing plate was evaluated according to the 
following evaluation method. 
(Evaluation) 
(Stains) 
The positive-working printing plate was further heated at 250.degree. C. 
for 60 seconds for burning treatment, cooled to room temperature, washed 
with water, and then gummed. Employing the printing plate obtained above, 
printing was carried out on a printing machine (DAIYA1F-1 produced by 
Mitsubishi Jukogyo Co., Ltd.), wherein a coated paper, dampening water 
(Etch Solution SG-51 (concentration 1.5%) produced by Tokyo Ink Co., Ltd.) 
and printing ink (Hyplus M magenta produced by Toyo Ink Manufacturing Co., 
Ltd.) were used. Thus, one hundred prints were obtained, and the non-image 
portions of the one hundredth print were evaluated according to the 
following criteria: 
A: No stains occurred at non-image portions. 
B: Several stains occurred at non-image portions. 
C: Stains occurred at a part of non-image portions or at the entire 
non-image portions. 
(Stop dirtiness occurred on the support after printing was started, stopped 
during a predetermined interval, and then resumed) 
Printing was carried out in the same manner as above, except that the 
positive-working printing plate was not subjected to burning treatment and 
gumming, and pure water was used as dampening water. After five thousand 
sheets of coated paper were printed, printing was stopped for 1 hour, and 
then printing was resumed to obtain one hundred prints. The number of stop 
dirtiness occurred on 100 cm.sup.2 non-image portions of the one hundredth 
print at resumption of a print run was counted for evaluation. 
The results are shown in Table 2. 
TABLE 2 
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Presensitized 
Aluminum Number per 
planographic 
alloy 100 cm.sup.2 of 
printing plate No. 
support No. 
Stains stop dirtiness 
Remarks 
______________________________________ 
1 1 A 2 Invention 
2 2 A 5 Invention 
3 3 C 86 Comparative 
4 4 B 43 Comparative 
______________________________________ 
As is apparent from Table 2, the planographic printing plates 1 and 2 
employing the aluminum alloy support of the invention produced no stain, 
and provided surprisingly reduced stop dirtiness as compared with the 
comparative samples. The aluminum alloy support of the invention provides 
extremely superior printing properties.