BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for preparing a presensitized plate for
use in making a lithographic printing plate.
[0002] A presensitized plate for use in making a lithographic printing plate (so-called
PS plate) comprising an aluminum plate and a light-sensitive composition applied onto
the plate in the form of a thin film is prepared by subjecting an aluminum plate to
a surface-roughening treatment, for instance, a mechanical method such as brush graining
or ball graining, an electrochemical method such as electrolytic graining, or a combination
thereof to give a roughened surface; etching the surface with an aqueous solution
of an acid or alkali; anodizing the aluminum plate; optionally hydrophilizing the
plate; and then applying a light-sensitive layer to the surface of the plate. This
PS plate is in general imagewise exposed to light, developed, image-corrected and
gummed up to give a lithographic printing plate which is then fitted to a printing
press to carry out printing operations.
[0003] In the foregoing preparation of the PS plate, the anodization of the aluminum plate
is carried out in such a manner that any current does not pass through the back face
thereof. However, the back face thereof is partially anodized since a part of the
current passes therethrough. Moreover, it is believed that the back face of the aluminum
plate should be anodized to some extent from the viewpoint of facilities for the bath
of the anodization treatment and as a preventive measure against formation of scratch
marks on the surface of the aluminum plate. For this reason, the aluminum plate used
in the PS plate described above has anodized layers on the surface and the back face.
[0004] The anodized layer is not soluble in a developer having a pH of less than 12.5, but
soluble in a strong alkali developer having a pH of not less than 12.5. For this reason,
the greater the quantity of the anodized layer formed on the surface and the back
face of an aluminum plate, the greater the amount of the anodized layer dissolved
in an alkali developer. The dissolved anodized layer is accumulated in the developer
and remains therein in the form of insoluble compounds or sludge. This in turn impairs
the washing ability of an automatic developing machine and results in the deposition
thereof on sensors for detecting, for instance, the activity of the developer through
determination of an electric conductivity to thus interfere with the determination
thereof. When the aluminum plate is treated with an aqueous solution of an alkali-metal
silicate, the higher the molar ratio: SiO
2/M
2O(M represents an alkali-metal), the stronger the foregoing tendency.
[0005] On the other hand, the aluminum plate is dissolved in a developer through the side
on which a light-sensitive layer is applied, but the back face thereof is first dissolved
therein and, therefore, if the time required for the development is short, the back
face is dissolved in a higher ratio.
[0006] Moreover, there has been known a sealing treatment of an anodized layer through treatment
with steam for eliminating the phenomenon of remaining color on the side of the light-sensitive
layer observed after the development thereof as disclosed in Japanese Patent Unexamined
Publication (hereinafter referred to as "J.P. KOKAI") No. Hei 4-176690(=EP-A-0485958).
When the degree of the sealing is too high and the resulting lithographic printing
plate is insufficiently desensitized, for instance, insufficiently gummed up, the
hydrophilicity of non-image areas is impaired and are easily contaminated with printing
inks. Thus, it has been proposed that the steam-treatment should be carried out so
that the degree of sealing ranges from 40 to 95% for the surface and, as disclosed
in EP-A-0485958 not less than 80% for the back face. If the PS plate prepared using
the aluminum plate thus treated is developed with an alkali developer having a pH
of not less than 12.5, the amounts of insoluble compounds or sludge formed in the
developer can be substantially reduced, but if the developing treatment is performed
over a long period of time, insoluble compounds or sludge are accumulated and adhered
to the PS plates during processing.
[0007] On the other hand, the anodized layer is treated with an aqueous solution of an alkali
silicate as disclosed in U.S. Patent No. 3,181,461, the anodized layer is only slightly
dissolved in an alkali developer having a pH of not less than 12.5. However, the adhesion
of the anodized layer of the aluminum plate thus treated to a positive-working light-sensitive
layer subsequently applied thereto is impaired and the printing durability of the
resulting lithographic printing plate is substantially reduced, in particular, when
a plate-cleaner is employed.
[0008] In addition, J.P. KOKAI No. Hei 2-185493 discloses a method for treating an anodized
aluminum plate with an aqueous solution of an alkali metal silicate containing a hydroxide.
[0009] The anodized layer of an aluminum plate thus treated is scarcely dissolved in an
alkaline developer having a pH of 12.5 or higher, but the adhesion of the anodized
layer of the aluminum plate thus treated to a positive-working light-sensitive layer
subsequently applied is likewise impaired and the printing durability of the resulting
lithographic printing plate is substantially reduced, in particular, when a plate-cleaner
is employed.
[0010] EP-A-0089510 discloses a method of preparing an offset PS plate comprising the steps
of treating an anodized aluminum plate with an alkali metal silicate solution having
a pH ranging from 8.0 to 10.5, then washing the aluminum plate with an aqueous solution
of an acid depends on case, and subsequently applying a light-sensitive layer on top
of the aluminum plate.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a method for preparing a PS plate
which permits the suppression of the dissolution of an anodized layer formed on an
aluminum plate in an alkaline developer and in turn the reduction of the amounts of
insoluble compounds or sludge formed in the developer and which can provide a lithographic
printing plate exhibiting good adhesion between the aluminum substrate and a positive-working
light-sensitive layer and satisfactory printing durability.
[0012] The present invention provides a method for preparing a presensitized plate for use
in making a lithographic printing plate comprising the steps of treating an anodized
aluminum plate with an aqueous solution of an alkali metal silicate having a pH ranging
from 10 to 13 as determined at 25 °C, then treating the aluminum plate with an aqueous
solution of an acid having a pH ranging from 1 to 6, then applying a hydrophilic underlying
coating layer onto the aluminum plate thus treated, and then applying a light-sensitive
layer on top of the hydrophilic underlying coating layer.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] The method of the present invention will be explained in more detail below.
Aluminum Plate
[0014] The aluminun plate used in the invention is a plate-like material of, for instance,
pure aluminum or an aluminum alloy which comprises aluminum as a principal component
and small amounts of trace elements.
[0015] Examples of the trace elements are silicon, iron, manganese, copper, magnesium, chromium,
zinc, bismuth, nickel and titanium. Aluminum alloys usable in the invention comprise
these trace elements in an amount of not more than 10% by weight. An aluminum material
suitably used in the invention is pure aluminum, but the production of completely
pure aluminum is difficult from the viewpoint of the aluminum refining technique and
thus it is preferred to use those having contents of trace elements as low as possible.
Aluminum alloys having a content of trace elements on the order of that defined above
can be used in the invention without any trouble. As described above, the aluminum
plate used in the invention is not restricted to those having specific compositions
and any aluminum material known in the art and commonly used may appropriately be
used in the invention. Examples of preferred aluminum materials are JIS A 1050, JIS
A 1100, JIS A 1200, JIS A 3003, JIS A 3103 and JIS A 3005. The thickness of the aluminum
plate used in the invention ranges from 0.1 mm to 0.5 mm.
[0016] The aluminum plate is optionally degreased by treating it with an aqueous solution
of a surfactant or an alkaline agent to remove rolling oils from the surface thereof
and surface-grained prior to anodization.
Surface-Graining Treatment
[0017] Methods for surface-graining an aluminum plate include, for instance, a method for
mechanically surface-roughening an aluminum plate, a method for electrochemically
dissolving the surface of an aluminum plate and a method for selectively and chemically
dissolving the surface of an aluminum plate. The mechanical surface-graining method
usable in the invention may be any known method such as ball graining, brush graining,
blast graining and buff graining methods. In addition, the electrochemical surface-graining
methods include, for instance, those comprising electrolyzing the surface of an aluminum
plate in an electrolyte such as a hydrochloric acid or nitric acid aqueous solution
by passing an altenating or direct current through the aluminum plate. It is also
possible to use a method comprising combination of these two kinds of methods as disclosed
in J.P. KOKAI No. Sho 54-63902.
[0018] The aluminum plate thus surface-roughened is optionally etched with an alkali and
neutralized.
Anodization Treatment
[0019] In the anodization treatment of an aluminum plate, any electrolyte may be used so
far as they permit the formation of a porous oxidized layer on the aluminum plate,
but electrolytes usable in general include aqueous solutions of, for instance, sulfuric
acid, phosphoric acid, oxalic acid, chromic acid and mixture thereof and the concentrations
of these electrolytes may be appropriately determined depending on the kinds of electrolytes.
[0020] Conditions for anodization cannot unconditionally be determined since they vary depending
on each particular electrolyte selected, but the anodization is desirably performed
at an electrolyte concentration ranging from 1 to 80% by weight, an electrolyte temperature
ranging from 5 to 70°C, a current density ranging from 5 to 60 A/dm
2, a voltage of from 1 to 100 V and an electrolyzation time of from 10 seconds to 50
minutes. Among these anodization methods, preferred are the method disclosed in U.K.
Patent No. 1,412,768 in which an aluminum plate is anodized in a sulfuric acid solution
at a high current density and the method disclosed in U.S. Patent No. 4,211,619 which
comprises anodizing an aluminum plate in a sulfuric acid solution having a low concentration.
The most preferred method comprises anodizing an aluminum plate in an electrolyte
which comprises 5 to 20% by weight sulfuric acid and 3 to 15% by weight aluminum ions
and which is maintained at a temperature ranging from 25 to 50 °C, using a direct
current at a current density of 5 to 20 A/dm
2.
[0021] The quantity of the anodized layer to be formed may be in the range of from 0.1 to
10 g/m
2.
Treatment with Alkali Metal Silicate
[0022] The foregoing anodized layer formed on the aluminum plate is treated by immersing
the plate in an aqueous solution comprising 1 to 30% by weight, preferably 2 to 15%
by weight of an alkali metal silicate and having a pH ranging from 10 to 13 as determined
at 25 °C, at a desired temperature and time (for instance, 15 to 80 °C for 0.5 to
120 seconds).
[0023] If the pH of the alkali metal silicate aqueous solution is less than 10, the solution
causes gelation, while if it exceeds 13.0, the oxidized layer is dissolved in the
silicate solution.
[0024] Alkalki metal silicates usable in the invention are, for instance, sodium silicate,
potassium silicate and lithium silicate. Hydroxides used for increasing the pH of
the alkali metal silicate aqueous solution include, for instance, sodium hydroxide,
potassium hydroxide and lithium hydroxide.
[0025] The solutions used for the foregoing treatment may additionally contain alkaline
earth metal salts or salts of Group IVB metals.
[0026] Examples of such alkaline earth metal salts include water-soluble salts, for instance,
nitrates such as calcium nitrate, strontium nitrate, magnesium nitrate and barium
nitrate, sulfates, hydrochlorides, phosphates, acetates, oxalates and borates.
[0027] Examples of salts of Group IVB metals include titanium tetrachloride, titanium trichloride,
potassium titanium fluoride, potassium titanium oxalate, titanium sulfate, titanium
tetraiodide, zirconium oxide chloride, zirconium dioxide, zirconium oxychloride and
zirconium tetrachloride.
[0028] These alkaline earth metal silicates or salts of Group IVB metals may be used alone
or in combination. The amount of these metal salts to be added in the solution preferably
ranges from 0.01 to 10% by weight and more preferably 0.05 to 5.0% by weight.
Treatment with Acidic Aqueous Solution
[0029] An acidic aqueous solution having a pH ranging from 1 to 6 as determined at 25°C
and used in the treatment performed after the treatment with an alkali metal silicate
is an aqueous solution of an acid such as sulfuric acid, nitric acid, hydrochloric
acid, oxalic acid or phosphoric acid.
[0030] If the pH of the treating solution is less than 1, the anodized layer is dissolved
in the treating solution, while if it exceeds 6, any improvement of the adhesion between
the aluminum plate and a light-sensitive layer subsequently applied cannot be anticipated.
This treatment is suitably performed by immersing the plate in the solution at a temperature
ranging from 10 to 70 °C for 0.5 to 120 seconds, and more preferably at a temperature
ranging from 20 to 70 °C for 5 to 60 seconds.
Hydrophilic Underlying Coating Layer
[0031] Examples of hydrophilic underlying coating layers used in the invention are a hydrophilic
layer comprising a compound having at least one amino group and at least one member
selected from the group consisting of carboxyl group and groups in the form of salts
thereof as well as sulfo group and groups in the form of salts thereof as disclosed
in J.P. KOKAI No. Sho 60-149491; a hydrophilic layer comprising a compound selected
from the group consisting of those having at least one amino group and at least one
hydroxyl group and salts thereof as disclosed in J.P. KOKAI No. Sho 60-232998; a phosphate-containing
hydrophilic layer as disclosed in J.P. KOKAI No. Sho 62-19494; a hydrophilic layer
comprising a polymeric compound having, in the molecule, repeating units derived from
at least one monomer having a sulfo group as disclosed in J.P. KOKAI No. Sho 59-101651;
and an organic layer comprising at least one compound selected from the group consisting
of substituted or unsubstituted aliphatic or aromatic compounds represented by the
general formula: R
1(PO(OH)
2)
n or R
1(PO(OH)(R
2))
n wherein n is 1 or 2; if n is 1, R
1 and R
2 each represents a substituted or unsubstituted alkyl, alkoxy, aryloxy, aryl, acyl
or acyloxy group; and if n is 2, R
1 represents a substituted or unsubstituted alkylene or arylene group and R
2 is the same as that defined above as disclosed in EP-A-0503602.
Light-Sensitive Layer
[0032] A composition for the light-sensitive layer used in the invention may be any light-sensitive
composition so far as it causes change in its solubility or swelling characteristics
through exposure to light. Typical examples thereof will hereinafter be explained.
(A) Light-Sensitive Layer Comprising o-Quinonediazide Compound
[0033] Light-sensitive compounds for positive-working light-sensitive compositions are,
for instance, o-quinonediazide compounds and typical examples thereof include o-naphthoquinonediazide
compounds.
[0034] Preferred examples of o-naphthoquinonediazide compounds include esters of 1,2-diazonaphthoquinonesulfonic
acid chloride with pyrogallol-acetone resins as disclosed in Japanese Patent Publication
for Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") No. Sho 43-28403.
Preferred examples of o-quinonediazide compounds include an ester of 1,2-diazonaphthoquinonesulfonic
acid chloride with phenolformaldehyde resin as disclosed in U.S. Patent Nos. 3,046,120
and 3,188,210. Other useful o-naphthoquinonediazide compounds are known and disclosed
in a variety of patents such as J.P. KOKAI Nos. Sho 47-5303, Sho 48-63802, Sho 48-63803,
Sho 48-96575, Sho 49-38701 and Sho 48-13354; J.P. KOKOKU Nos. Sho 37-18015, Sho 41-11222,
Sho 45-9610 and Sho 49-17481; U.S. Patent Nos. 2,797,213, 3,454,400, 3,544,323, 3,573,917,
3,674,495 and 3,785,825; U.K. Patent Nos. 1,227,602, 1,251,345, 1,267,005, 1,329,888
and 1,330,932; and German Patent No. 854,890.
[0035] It is also possible to use o-naphthoquinonediazide compounds prepared through the
reactions of polyhydroxyl compounds having molecular weights of not more than 1,000
with 1,2-diazonaphthoquinonesulfonic acid chloride. Specific examples of these compounds
are those disclosed in, for instance, J.P. KOKAI Nos. Sho 51-139402, Sho 58-150948,
Sho 58-203434, Sho 59-165053, Sho 60-121445, Sho 60-134235, Sho 60-163043, Sho 61-118744,
Sho 62-10645, Sho 62-10646, Sho 62-153950, Sho 62-178562 and Sho 64-76047; U.S. Patent
Nos. 3,102,809, 3,126,281, 3,130,047, 3,148,983, 3,184,310, 3,188,210 and 4,639,406.
[0036] These o-naphthoquinonediazide compounds are synthesized by reacting polyhydroxyl
compounds with 1,2-diazonaphthoquinonesulfonic acid chloride in an amount of preferably
0.2 to 1.2 eq. and more preferably 0.3 to 1.0 eq. per one hydroxyl group of the polyhydroxyl
compound. Preferred 1,2-diazonaphthoquinonesulfonic acid chloride is 1,2-diazonaphthoquinone-5-sulfonic
acid chloride, but 1,2-diazonaphthoquinone-4-sulfonic acid chloride may also be used.
[0037] The o-naphthoquinonediazide compound thus prepared comprises a mixture of those which
differ, from one another, in positions of 1,2-diazonaphthoquinonesulfonic acid ester
groups and the number of the ester groups introduced therein, but preferred are those
having a rate of the compound whose hydroxyl groups are completely substituted with
1,2-diazonaphthoquinonesulfonic acid ester groups based on the mixture (the content
of the compound completely esterified) of not less than 5 mole%, more preferably 20
to 99 mole%.
[0038] Positive-working light-sensitive compounds other than o-naphthoquinonediazide compounds
include, for instance, o-nitrocarbinol ester group-containing polymeric compounds
as disclosed in J.P. KOKOKU No. Sho 56-2696 which may likewise be used in the invention.
[0039] Also usable in the invention include, for instance, systems comprising combinations
of photolytically acid-generating compounds with compounds having groups capable of
causing dissociation by the action of acids such as -C-O-C- and -C-O-Si groups.
[0040] Examples of such systems include combinations of photolytically acid-generating compounds
with acetal or O,N-acetal compounds as disclosed in J.P. KOKAI No. Sho 48-89003, with
orthoester or amidoacetal compounds as disclosed in J.P. KOKAI No. Sho 51-120714,
with polymers having acetal or ketal groups in the main chains as disclosed in J.P.
KOKAI No. Sho 53-133429, with enol ether compounds as disclosed in J.P. KOKAI No.
Sho 55-12995, with N-acyliminocarbon compounds as disclosed in J.P. KOKAI No. Sho
55-126236, with polymers having orthoester groups in the main chains as disclosed
in J.P. KOKAI No. Sho 56-17345, silyl ester compounds as disclosed in J.P. KOKAI No.
Sho 60-10247 and with silyl ether compounds as disclosed in J.P. KOKAI Nos. Sho 60-37549
and Sho 60-121446.
[0041] The amount of these positive-working light-sensitive compounds (inclusive of the
foregoing combinations) in the light-sensitive composition used in the invention suitably
ranges from 10 to 50% by weight and more preferably 15 to 40% by weight on the basis
of the total weight of the composition.
[0042] The o-quinonediazide compound by itself may form a light-sensitive layer, but the
compound is preferably used in combination with an alkaline water-soluble resin as
a binder. The light-sensitive composition may comprise a variety of alkaline water-soluble
polymeric compounds. Such alkaline water-soluble resins are, for instance, novolak
resins having the properties specified above and examples thereof include phenol-formaldehyde
resins, cresol-formaldehyde resins such as m-cresol-formaldehyde resins, p-cresol-formaldehyde
resins, m-/p-mixed cresol-formaldehyde resins and phenol-mixed cresol (m-, p- or m-/p-mixed
cresol)-formaldehyde resins, phenol-modified xylene resins, polyhydroxystyrene, poly(halogenated
hydroxystyrene), phenolic hydroxyl group-containing acrylic resins as disclosed in
J.P. KOKAI No. Sho 51-34711, sulfonamido group-containing acrylic resins as disclosed
in J.P. KOKAI No. Hei 2-866, and urethane resins. Among these alkali-soluble polymeric
compounds, preferred are those having weight-average molecular weights ranging from
500 to 200,000 and number-average molecular weights ranging from 200 to 60,000.
[0043] The amount of these alkali-soluble polymeric compounds to be added to the composition
is not more than 70% by weight on the basis of the total weight of the composition.
[0044] It is also preferred, for improving the ink-receptivity of images, to simultaneously
use a condensate of a phenol carrying an alkyl group having 3 to 8 carbon atoms as
a substituent with formaldehyde such as t-butylphenol-formaldehyde resin or octylphenol-formaldehyde
resin or an o-naphthoquinone-diazidosulfonic acid ester of the condensate (such as
those disclosed in J.P. KOKAI No. Sho 61-243446) as disclosed in U.S. Patent No. 4,123,279.
[0045] The light-sensitive composition used in the invention may further comprise cyclic
acid anhydrides for improving the sensitivity of the composition, agents or compositions
for obtaining visible images immediately after exposure to light, dyes for coloring
images and/or other fillers. Examples of such cyclic acid anhydrides- include, as
disclosed in U.S. Patent No. 4,115,128, phthalic anhydride, tetrahydrophthalic anhydride,
hexahydrophthalic anhydride, 3,6-endoxy-Δ
4-tetrahydrophthalic anhydride, tetrachlorophthalic anhydride, maleic anhydride, chloromaleic
anhydride, α-phenylmaleic anhydride, succinic anhydride and pyromellitic anhydride.
The sensitivity of the composition can be increased by a factor of at most about 3
if these cyclic acid anhydrides are incorporated into the composition in an amount
ranging from 1 to 15% by weight on the basis of the total weight of the composition.
Typical examples of agents or compositions for obtaining visible images immediately
after exposure to light are combinations of light-sensitive compounds capable of releasing
acids through exposure to light with salt-forming organic dyes. Specific examples
thereof are combinations of o-naphthoquinonediazido-4-sulfonic acid halides with salt-forming
organic dyes as disclosed in J.P. KOKAI No. Sho 50-36209; and combinations of trihalomethyl
compounds with salt-forming organic dyes as disclosed in J.P. KOKAI Nos. Sho 53-36223,
Sho 54-74728, Sho 60-3626, Sho 61-143748, Sho 61-151644 and Sho 63-58440. Agents for
coloring images may be the foregoing salt-forming organic dyes and other dyes. Preferred
dyes (inclusive of the salt-forming organic dyes) may be oil-soluble dyes and basic
dyes. Specific examples thereof are Oil Yellow #101, Oil Yellow #130, Oil Pink #312,
Oil Green BG, Oil Blue BOS, Oil Blue #603, Oil Black BY, Oil Black BS, Oil Black T-505
(all of these are available from Orient Chemical Industries, Ltd.), Victoria Pure
Blue, Crystal Violet (CI 42555), Ethyl Violet (CI 42600), Methyl Violet (CI 42535),
Rhodamine B (CI 45170B), Malachite Green (CI 42000) and Methylene Blue (CI 52015).
In addition, the dyes disclosed in J.P. KOKAI No. Sho 62-293247 are particularly preferred.
[0046] In the present invention, the light-sensitive composition is dissolved in a solvent
capable of dissolving the foregoing every components and then applied to the surface
of a substrate. Solvents usable herein include, for instance, ethylene dichloride,
cyclohexanone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol
monoethyl ether, 2-methoxyethyl acetate, 1-methoxy-2-propanol, 1-methoxy-2-propyl
acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate, dimethylsulfoxide,
dimethylacetamide, dimethylformamide, water, N-methylpyrrolidone, tetrahydrofurfuryl
alcohol, acetone, diacetone alcohol, methanol, ethanol, isopropanol, diethylene glycol
and dimethyl ether, which may be used alone or in combination. The concentration of
the foregoing components (solid content) in the solution ranges from 2 to 50% by weight.
The amount of the composition to be applied varies depending on the applications of
the composition, but in general it preferably ranges from 0.5 to 3.0 g/m
2 (as expressed in terms of solid content) for PS plates. The smaller the amount of
the composition coated, the higher the sensitivity of the resulting light-sensitive
film, but the lower the physical properties of the film.
[0047] The light-sensitive composition used in the invention may comprise surfactants for
improving the coating properties thereof such as fluorine atom-containing surfactants
as disclosed in J.P. KOKAI No. Sho 62-170950. The amount of the surfactant preferably
ranges from 0.01 to 1% by weight and more preferably 0.05 to 0.5% by weight on the
basis of the total weight of the light-sensitive composition.
(B) Light-Sensitive Layers Comprising Diazo Resins and Binders
[0048] Negative-working light-sensitive diazo compounds preferably used are condensed products
(so-called light-sensitive diazo resins) of diphenylamine-p-diazonium salts, which
are reaction products of diazonium salts with reactive carbonyl salt-containing organic
condensation agents such as aldol or acetal, with formaldehyde as disclosed in U.S.
Patent Nos. 2,063,631 and 2,667,415. Examples of other useful condensed diazo resins
are disclosed in, for instance, J.P. KOKOKU Nos. Sho 49-48001, Sho 49-45322 and Sho
49-45323. These light-sensitive diazo resins are in general used in the form of water-soluble
inorganic salts and, therefore, they can be applied in the form of aqueous solutions.
Alternatively, these water-soluble diazo compounds can be reacted with aromatic or
aliphatic compounds having at least one phenolic hydroxyl group or sulfonate residue
or both of these groups according to the method disclosed in J.P. KOKOKU No. Sho 47-1167
to give substantially water-insoluble light-sensitive diazo resins as reaction products.
The products can likewise be used in the invention.
[0049] It is also possible to use the foregoing diazo compounds in the form of reaction
products with hexafluorophosphates or tetrafluoroborates as disclosed in J.P. KOKAI
No. Sho 56-121031.
[0050] Examples of reactants having phenolic hydroxyl groups are hydroxybenzophenone, 4,4-bis(4'-hydroxyphenyl)pentanoic
acid, resorcinol or diphenolic acids such as diresorcinol, which may have substituents.
Specific examples of hydroxybenzophenones include 2,4-dihydroxybenzophenone, 2-hydroxy-4-m
ethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 2,2',4,4'-tetrahydroxybenzophenone.
Examples of preferred sulfonic acids include aromatic sulfonic acids such as sulfonic
acids of benzene, toluene, xylene, naphthalene, phenol, naphthol and benzophenone
or soluble salts thereof such as ammonium and alkali metal salts. These sulfonic acid
residue-containing compounds may in general be substituted with lower alkyl groups,
nitro group and/or an additional sulfonic acid group. Preferred examples thereof are
benzenesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid, 2,5-dimethylbenzenesulfonic
acid, sodium benzenesulfonate, naphthalene-2-sulfonic acid, 1-naphthol-2 (or 4)-sulfonic
acid, 2,4-dinitro-1-naphthol-7-sulfonic acid, 2-hydroxy-4-methoxybenzophenone-5-sulfonic
acid, sodium m-(p'-anilinophenylazo)benzenesulfonate, alizarinsulfonic acid, o-toluidine-m-sulfonic
acid and ethanesulfonic acid. Sulfonic acids of alcohols and salts thereof are also
useful in the invention. Generally, such compounds can easily be available as anionic
surfactants and specific examples thereof include ammonium salts or alkali metal salts
of, for instance, lauryl sulfate, alkylaryl sulfate, p-nonylphenyl sulfate, 2-phenylethyl
sulfate and isooctylphenoxydiethoxyethyl sulfate.
[0051] These substantially water-insoluble light-sensitive diazo resins each is isolated
by admixing an aqueous solution of a water-soluble diazo resin with an aqueous solution
of the foregoing aromatic or aliphatic compound preferably in amounts approximately
identical to one another in the form of precipitates.
[0052] In addition, diazo resins as disclosed in U.K. Patent No. 1,312,925 are likewise
preferably used in the invention.
[0053] It is also preferred to use diazo resins having phosphorus atom-containing oxyacid
groups as disclosed in J.P. KOKAI No. Hei 3-253857, diazo resins condensed with carboxyl
group-containing aldehyde or acetal compounds thereof as disclosed in J.P. KOKAI No.
Hei 4-18559, diazo resins co-condensed with carboxyl, group-containing aromatic compounds
such as phenoxyacetic acid as disclosed in J.P.KOKAI. No. Hei 4-211253.
[0054] Most preferred diazo resins are, for instance, 2-methoxy-4-hydroxy-5-benzoylbenzenesulfonate
of condensates of p-diazodiphenylamine with formaldehyde.
[0055] The content of these diazo resins in the light-sensitive layer suitably ranges from
5 to 50% by weight. The smaller the content of the diazo resin, the higher the light-sensitivity
of the resulting light-sensitive layer, but the lower the stability thereof with time.
The amount of the diazo resin most preferably ranges from 8 to 20% by weight.
[0056] On the other hand, binders may be various kinds of polymeric compounds, but preferably
used in the present invention include those comprising groups selected from hydroxyl,
amino, carboxyl, amido, sulfonamido, active methylene, thioalcohol and/or epoxy groups.
Examples of preferred binders include shellac as disclosed in U.K. Patent No. 1,350,521;
polymers comprising, as main repeating units, those derived from hydroxyethyl acrylate
or hydroxyethyl methacrylate as disclosed in U.K. Patent No. 1,460,973 and U.S. Patent
No. 4,123,276; polyamide resins as disclosed in U.S. Patent No. 3,751,257; phenol
resins and polyvinyl acetal resins such as polyvinl formal resins and polyvinyl butyral
resins as disclosed in U.K. Patent No. 1,074,392; linear polyurethane resins as disclosed
in U.S. Patent No. 3,660,097; phthalate-modified polyvinyl alcohol resins; epoxy resins
obtained through condensation of bisphenol A and epichlorohydrin; amino group-containing
polymers such as polyaminosulfone and polyalkylamino(meth)acrylate; and cellulose
derivatives such as cellulose acetate, cellulose alkyl ether and cellulose acetate
phthalate.
[0057] The composition comprising a diazo resin and a binder may further comprise other
additives such as pH indicators as disclosed in U.K. Patent No. 1,041,463 and phosphoric
acid and dyes as disclosed in U.S. Patent No. 3,236,646.
(C) Light-Sensitive Layer Comprising Aside Compound and Binder (Polymeric Compound)
[0058] Examples of light-sensitive compositions of this kind include those comprising aside
compounds and water-soluble or alkali-soluble polymeric compounds as disclosed in
U.K. Patent Nos. 1,235,281 and 1,495,861 and J.P. KOKAI Nos. Sho 51-32331 and Sho
51-36128; and those comprising azido group-containing polymers and polymeric compounds
as binders as disclosed in J.P. KOKAI Nos. Sho 50-5102, Sho 50-84302, Sho 50-84303
and Sho 53-12984.
(D) Other Light-Sensitive Resin Layer
[0059] Examples of other light-sensitive resins are polyester compounds as disclosed in
J.P. KOKAI No. Sho 52-96696; polyvinyl cinnamate resins as disclosed in U.K. Patent
Nos. 1,112,277, 1,313,390, 1,341,004 and 1,377,747; photo-polymerizable photopolymer
compositions as disclosed in U.S. Patent Nos. 4,072,528 and 4,072,527.
(E) Electrophotographic Light-Sensitive Layer
[0060] The electrophotographic light-sensitive layer mainly comprises a photoconductive
compound and a binder, but may optionally comprise known dyes, pigments, chemical
sensitizers and other additives for the improvement of the sensitivity and for imparting,
to the layer, sensitivity to a desired wavelength range. The light-sensitive layer
may comprise a single layer or a plurality of layers comprising those having a charge-generating
function and those having a charge-transfer function. A lithographic printing plate
can be obtained by forming a toner image on the light-sensitive layer according to
the known electrophotographic process and then decoding the non-image areas while
using the toner image as a resist layer. These light-sensitive layers are disclosed
in various publications such as J.P. KOKOKU Nos. Sho 37-17162, Sho 38-6961, Sho 59-36259
and Sho 59-25217 and J.P. KOKAI Nos. Sho 56-107246, Sho 60-254142, Sho 56-146145,
Sho 62-194257, Sho 57-147656, Sho 58-100862 and Sho 57-161863, all of which may be
suitably used in the invention.
[0061] The thickness of the light-sensitive layer preferably ranges from 0.1 to 30 µm and
more preferably 0.5 to 10 µm. The amount (solid content) of the light-sensitive layer
to be applied to a substrate ranges from 0.1 to 7 g/m
2 and preferably 0.5 to 4 g/m
2. The surface of the light-sensitive layer thus applied is preferably matted in order
to shorten the evacuation time required for the close contact exposure in a vacuum
printing frame and prevent an image from becoming indistinct. More specifically, such
a mat layer can be formed by a method as disclosed in J.P. KOKAI No. Sho 50-12580
and J.P. KOKOKU Nos. Sho 57-6582 and Sho 61-28986 or a method as disclosed in J.P.
KOKOKU No. Sho 62-62337 which comprises heat-fusing solid powder on the light-sensitive
layer.
[0062] The PS plate used in the present invention is imagewise exposed to light and then
treated by the usual manner including development to give a lithographic printing
plate.
[0063] For instance, a positive-working PS plate having a light-sensitive layer (A) is imagewise
exposed to light and then developed with an alkaline aqueous solution such as those
disclosed in U.S. Patent No. 4,259,434 and J.P. KOKAI No. Hei 3-90388 to remove the
light-sensitive layer on the exposed area and to thus give a lithographic printing
plate.
[0064] Alternatively, a negative-working PS plate having a light-sensitive layer (B) which
comprises a diazo resin and a binder is imagewise exposed to light and then developed
with a developer such as those disclosed in, for instance, U.S. Patent No. 4,186,006
to remove the light-sensitive layer on the unexposed area and to thus give a lithographic
printing plate.
[0065] The PS plate used in the invention can of course be subjected to the plate-making
methods as disclosed in J.P. KOKAI Nos. Sho 54-8002, Sho 55-115045 and Sho 59-58431.
More specifically, after developing the imagewise exposed PS plate, it is washed with
water and then desensitized; or directly desensitized without water-washing; or treated
with an aqueous solution containing an acid; or desensitized after treating with an
aqueous solution containing an acid. Moreover, in the development processing of the
PS plate of this kind, the processing ability of an alkaline developer because the
alkali concentration is reduced due to consumption thereof in proportion to the quantity
of the PS plate processed or through absorption of air when an automatic developing
machine is operated over a long time, but the processing ability of the alkaline developer
can be recovered by the addition of a fresh developer (replenisher) or a replenisher
having a high alkaline concentration as disclosed in J.P. KOKAI No. Sho 54-62004.
In this case, the supplementation of the replenisher is preferably carried out by
a method in which the replenisher is added in an amount proportional to the length
of one side of the PS plate to be processed or the method disclosed in U.S. Patent
No. 4,882,246.
[0066] Moreover, the foregoing plate-making process is preferably performed in an automatic
developing machine as disclosed in J.P. KOKAI Nos. Hei 2-7054 and Hei 2-32357.
[0067] Furthermore, when erasing unnecessary portions of images after imagewise exposure,
development, water-washing or rinsing the PS plate used in the present invention,
it is preferred to use an erasing solution as disclosed in J.P. KOKOKU No. Hei 2-13293.
Desensitizing gums optionally applied to the resulting lithographic printing plate
at the final step of the plate-making process are preferably those disclosed in J.P.
KOKOKU Nos. Sho 62-16834, Sho 62-25118 and Sho 63-52600 and J.P. KOKAI Nos. Sho 62-7595,
Sho 62-11693 and Sho 62-83194.
[0068] In addition, when the PS plate used in the present invention is subjected to burning-in
treatment after imagewise exposure, development, water-washing or rinsing, optional
erasing and water-washing, it is preferred to treat the plate with a surface-conditioning
solution as disclosed in J.P. KOKOKU Nos. Sho 61-2518 and Sho 55-28062 and J.P. KOKAI
Nos. Sho 62-31859 and Sho 61-159655, prior to the burning-in treatment.
[0069] The aluminum substrate of the PS plate used in the present invention is only slightly
dissolved in an alkaline developer and this accordingly prevents the formation of
insoluble compounds or sludge effectively, during development.
[0070] The present invention will hereinafter be explained in more detail with reference
to the following Examples. In addition, the effects practically achieved by the invention
will also be discussed in detail while comparing with Comparative Examples. In the
following Examples, the term "%" means "% by weight" unless otherwise specified.
Reference Example 1
[0071] A JIS 1050 aluminum sheet was surface-grained with an aqueous suspension of pumice
stone as an abrasive and a rotary nylon brush. At this stage, the surface roughness
of the aluminum sheet was determined and found to be 0.5 µm (expressed in terms of
central line-average surface roughness). After water-washing, the aluminum sheet was
etched by immersing it in a 10% aqueous caustic soda solution heated up to 70°C to
such an extent that the amount of dissolved aluminum was reached 6 g/m
2. After water-washing, the sheet was neutralized by immersing in a 30% nitric acid
aqueous solution for one minute and then sufficiently washed with water. Thereafter,
the sheet was electrolytically surface-roughened for 20 seconds in a 0.7% nitric acid
aqueous solution using a rectangular alternating waved voltage having an anodic voltage
of 13 V and a cathodic voltage of 6 V, then immersed in a 20% sulfuric acid solution
maintained at 50°C to wash the surface thereof and washed with water.
[0072] Further a porous anodized layer was formed on the sheet in a 20% aqueous sulfuric
acid solution using a direct current.
[0073] The aluminum sheet was electrolyzed at a current density of 5 A/dm
2 while adjusting the electrolyzation time such that the weight of the anodized layer
formed on the surface of the aluminum sheet was 2.5 g/m
2 and the weight of the anodized layer formed on the back face thereof was 0.5 g/m
2, to thus give a substrate (I).
[0074] The substrate (I) was treated with a 10% aqueous sodium silicate solution (pH 11.2)
at 70 °C for 12 seconds, washed with water and then treated with an aqueous sulfuric
acid solution having a pH of 2 at 30 °C for 15 seconds.
[0075] The following light-sensitive composition was applied onto the substrate thus prepared
so that the coated amount thereof was 2.5 g/m
2 (weighed after drying) and then dried to form a light-sensitive layer.
Light-Sensitive Composition
[0076]
Component |
Amount (g) |
ester compound of naphthoquinone-1,2-diazido-5-sulfonyl chloride and pyrogallol-acetone
resin (the compound disclosed in Example 1 of U.S. Patent No. 3,635,709) |
0.75 |
cresol-novolak resin |
2.00 |
Oil Blue #603 (available from Orient Chemical Industries, Ltd.) |
0.04 |
ethylene dichloride |
16 |
2-methoxyethyl acetate |
12 |
[0077] The PS plate thus prepared was exposed to light from a 3 KW metal halide lamp for
50 seconds at a distance of 1 m through a transparent positive film in a vacuum printing
frame and then developed with a 3.5% aqueous solution of sodium silicate (pH 12.9)
having a molar ratio, SiO
2/Na
2O, of 0.83.
[0078] After the development, the plate was sufficiently washed with water, followed by
a gumming up treatment and printing operation in the usual manner. In this respect,
after processing 10 m
2 of the PS plate per one liter of the developer, the degree of dissolution of the
anodized layer in the developer was evaluated on the basis of the condition of the
insoluble compounds remaining in the developer. The results thus obtained and the
printing durability are summarized in the following Table 1.
Example 1
[0079] The substrate (I) was treated with a 10% by weight aqueous solution of sodium silicate
(pH 11.2) at 70°C for 12 seconds, then washed with water and treated with an aqueous
sulfuric acid solution having a pH of 2 at 30 °C for 15 seconds.
[0080] Thereafter, the same procedures used in Reference Example 1 were repeated except
that a solution comprising 1 g of phenylsulfonic acid, 39 g of water and 60 g of methanol
was applied onto the substrate thus treated in an amount of 20 mg/m
2 (weighed after drying) and then dried at 80 °C for 30 seconds.
[0081] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Reference Example 2
[0082] The same procedures used in Reference Example 1 were repeated except that the substrate
(I) was treated with a 10% by weight aqueous solution of sodium silicate (pH 13.0),
to which sodium hydroxide was added, at 70°C for 12 seconds, then washed with water
and treated with an aqueous sulfuric acid solution having a pH of 2 at 30 °C for 15
seconds.
[0083] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Example 2
[0084] The substrate (I) was treated with a 10% by weight aqueous solution of sodium silicate
(pH 13.0), to which sodium hydroxide was added, at 70°C for 12 seconds, then washed
with water and treated with an aqueous sulfuric acid solution having a pH of 2 at
30 °C for 15 seconds. Thereafter, the same procedures used in Reference Example 1
were repeated except that a solution comprising 1 g of phenylphosphonic acid, 39 g
of water and 60 g of methanol was applied onto the substrate thus treated in an amount
of 20 [mg/m
2] (weighed after drying) and then dried at 80°C for 30 seconds.
[0085] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Comparative Example 1
[0086] The same procedures used in Reference Example 1 were repeated using the substrate
(I) except that the treatments with an alkali metal silicate aqueous solution and
with an aqueous sulfuric acid solution were omitted.
[0087] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Comparative Example 2
[0088] The same procedures used in Reference Example 1 were repeated using the substrate
(I) except that the treatment with an aqueous sulfuric acid solution were omitted.
[0089] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Comparative Example 3
[0090] The same procedures used in Example 1 were repeated using the substrate (I) except
that the treatment with an aqueous sulfuric acid solution were omitted.
[0091] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Comparative Example 4
[0092] The same procedures used in Reference Example 2 were repeated using the substrate
(I) except that the treatment with an aqueous sulfuric acid solution were omitted.
[0093] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
Comparative Example 5
[0094] The same procedures used in Example 2 were repeated using the substrate (I) except
that the treatment with an aqueous sulfuric acid solution were omitted.
[0095] After processing 10 m
2 of the resulting PS plate per one liter of the developer, the developer was examined
on whether insoluble compounds remained therein or not. The results thus obtained
and the printing durability are summarized in the following Table 1.
[0096] In the following Table 1, the printing durability data are expressed in values relative
to that observed in Comparative Example 1 which is assumed to be 100.
Table 1
Insoluble Compounds Remaining in Developer and Printing Durability |
Ex. No. |
Treatment A1) |
Treatment B 2) |
Underlying Coating |
Insoluble Compounds Remaining in Developer3) |
Printing Durability (%) |
1** |
Yes |
Yes |
No |
A |
95 |
1 |
Yes |
Yes |
Yes |
A |
120 |
2** |
Yes |
Yes |
No |
A |
100 |
2 |
Yes |
Yes |
Yes |
A |
120 |
1 * |
No |
No |
No |
B |
100 |
2 * |
Yes |
No |
No |
A |
40 |
3 * |
Yes |
No |
Yes |
A |
60 |
4 * |
Yes |
No |
No |
A |
40 |
5 * |
Yes |
No |
Yes |
A |
60 |
*: Comparative Example |
**: Reference Example |
1) Treament with an alkali metal silicate. |
2) Treatment with an aqueous sulfuric acid solution. |
3) This is evaluated according to the following two stage evaluation criteria.
A: Any insoluble compounds was not formed.
B: A large amount of insoluble compounds was formed. |