Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Hoe 81/K 045
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PROCESS FOR THE PRODUCTION OF LITHOG~APHIC PRINTING
F MS USING A LIGHT-SENSITIVE ~IATERIAL BASED ON
DIAZONIUM SALT PO~YCONDENSATION PRODUCTS
This invention relates to a process for the pro~uction of
lithographic printing forms from a light-sensitive reproduction
materLal comprising a negative-working layer containing a diazon-
ium salt polycondensation product, which is applied to a support.
Heretofore, two alternative methods have been proposed
with a view to solving the technical problem of producing heavy-
L O duty, negative-working lithographic printing plates based on
diazonium salt polycondensation products. One of these methods
pertains to an improvement of the properties of the Light-sensltive
diazo compound and the other ls concerned with the discovery of
novel poLymers which may; at times, be formulated to meet
special requirements and function as a supporting framewor3c within
the layer, upon which they impose their physical properties.
While the known light-sensitive diazo compounds as pro-
posed, for example, in German Offenlegungsschriften Nos,
2, 024, 242 and 2, 024, 244 have already attained a high quality
standard, the fine adjustment of the copying layers by means of
the polymers added thereto, is extremely difficult. There is, for
example, a risk that abrasion resistance is insufficient under
exacting working conditlons, for example, when printing on card-
board, or that the image areas become blinded due to a loss of
oleophilic properties, or that scumming occurs as a result of poor
` development, or that the individual constituents of the layer are
incompatible under changing storage conditions.
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Therefore, layers which can be developed with aqueous
solutions and comprise pure diazo polycondensates, particularly
condensates of 4-diazodiphenylamines with Eormaldehyde or of
4-diazodLphenylamine derivatives with other compounds which are
capable of condensation, do not yield very long printing runs.
The same applies, to a higher degree, to corresponding layers
which can be developed with pure water, for example, as
described in German Patent No. 1,160,733, Arhich corresponds to
, .
U. S. Patent No. 3 ,220,832 .
G0rman Offenlegungsschrift No. 1,447,957, which corre-
si~ sponds to British Patent No. 1,110,017, discloses presensitized
~-' lithographic printing plates, the light-sensitive layers oE which
.. ~,
contain condensation products of diphenylamine diazonium salts
~ with formaldehyde in combination with alkali-soluble resins, for
,- example, copolymers of styrene and maleic anhydride. These
:'
~-i layers are also developed with -water, but they yield only limited
~,.,,~
printing runs,
In German Offenlegungsschrift No. 2, 243,2~2, eorrespond-
ing to U. S. Patent No. 3,877,948, lithographic printing plates
.;~ .,
:`;` 20 are described which comprise a water-soluble high-molecular
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, . . .
weight alkylene oxide polymer, a polyearboxylic aeid resin or a
polyearboxylie acid whieh forms an assoeiate with the alkylene
; ~ oxide polymer, and a photosensitizing agent. Styrene-maleic
anhydride copolymers may, among others, also be used as the
j~ ~
polycarboxylic aeid resins in this light-sensitive eomposition. A
development step by washing out the unexposed layer areas is
not performed. Also in this case, the printing run obtainable is
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limited because, naturally, the hydrophilic character of the unex-
posed background areas will gradually disappear, when the print-
ing form is stored in light.
Basically, it is preferable to use the aforementioned poly-
condensation products of diazonium salts and second components
which are capable of condensation therewith, for example, as
described in German Offenlegungsschrift NoO 2, 024, 244, corre-
sponding to U. S. Patent No. 3,867,147, because these products
have a higher sensitivlty to light compared with the condensation
products of diazonium salts with formaldehyde, and they also allow
longer printing runs.
All of the negative-working printing plates based on these
diazonium salt condensation products, which are used today and
are actually efficient, contain polymeric binders of a kind require-
ing a developing treatment with acidic aqueous solutions with the
addition of solvents which are, Ln some cases, volatile and give
off a strong odor. Such printLng plates are, for example, de-
- scribed in German Offenlegungsschrift Mo~ 2 ,139, 774, correspond-
.~ .
~ ing to U. S. Patent No. 4,186,017, They contain polyurethanes
.,
~- ~ 20 as the binders.
German Auslegeschrift No. 2,019,426, corresponding to
~, British Patent No. 1,352 ,411, discloses a light-sensitL~e compo-
;~ sition and a light-sensitive reproduction material for the prepara-
; tion of etch-resistant layers. The light-sensitive substances used
are diazo polycondensates of 4-diazodiphenylamines and com,~ounds
which are capable of condensatLon therewith. As the polymeric
binder, a mixture of two resins is described; one of these may be
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a styrene-maleic anhydride copolymer. For developing these compositions,
developers which contain larger amounts of organic solvents are exclusively
used~
, .
In Canadian Patent Application Number 386,257, filed September 18,
1981, a light-sensitive composition is described, which comprises the
. indicated diazonium salt polycondensation products and a polymer having
sulfonylurethane side groups, which is soluble in aqueous alkaline
solutions. This composition can be developed with aqueous alkaline solutions
withou~ the addition of organic solvents.
Accordingly, it is the object of this invention to provide a
~ process for the production of lithographic printing forms corresponding
J!~ in quality to the printing plates which can be developed only with the
addition of organic solvents, the process of the invention being however
.~ .
adapted to be performed with purely aqueous-aklaline solutions.
~; The in~ention provicles a process for the production of a
lithographic printing form, in which a light-sensitive reproduction
material comprising a support which has a hydrophilic surface and is suitable
~ for lithographic printing and a negative-working light-sensitive layer
.~: which contains as the light-senstive compound a condensation product with
:
recurrent units A-N2X and B, which are linked by bivalent intermediate
members derived from a carbonyl compound which is capable of condensation,
the units A-N2X being derived from compounds of the general formula
(Rl-R3-) R2_N2x
in which
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X is th0 anion of the diazonium compound
p is an lnteger from 1 to 3,
R is a carbocyclic or heterocycllc aromatic radi-
cal which is capable of condensatLon in at least
one position,
R is an arylene group of the benzene or naphth-
lene series,
R3 is a single bond or one of the groups
~(CH2)q~NR4~ ~
. 10 ~~(C~2)r N~ -,
; -S - (CH2 ) -NR -,
',~., -S-CH2-CO-NR -,
,~ -o R5 o-
~ O
.~ -S-, or
~- -CO -NR
in which
q is a number Lrom 0 to 5,
. ~, .
r is a number from 2 to 5,
R is a hydrogen atom, an alkyl group
having from 1 to S carbon atorns, an
aralkyl ~roup having from 7 to 12
carbon atoms or an aryl group hav-
ing from 6 to 12 carbon atoms, and
R is an arylene group having from 6
to 12 carbon atoms,
and B denotes the radical of an aromatic amine, phenol, thiophenol,
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phenol ether, aromatic thioether, aromatic hydrocarbon, aromatic
heterocyclic compo~md, or organic acid amide, which is free of
diazonium groups, the condensation product containing, on an
averac~e, ~rorn 0.01 to 50 B units for each A-N2X unit, and, as
the binder, a copolymer of styrene and maleic anhydride or a par-
tial ester of maleic acid, is exposed imagewise and the unexposed
layer areas are washed away with a developer. In the process of
~he invention, the developer used is an alkaline solution which
contains water exclusively as the solvent.
. 10 Surprisingly, these copolymers of styrene and maleic anhy-
` dride or the partial esters, normally the half-esters, of maleic
acid obtained by reacting maleic anhydride with alcohols or
: phenols, in admixture with mixed diazo condensates, lead to
; printing plates with excellent properties, particularly if applied to
anodized supports~ The lithographic printing plates can be de-
veloped with aqueous-alkaline surfactant solutions in an environ-
; mentally safe manner and they, nevertheless, exhibit properties
which heretofore have been encountered only in printing plates
hich can be processed only by means of developers containing
organic solvents. These properties include, in particular, very
good resolution, high sensitivity to light, high stability of print-
ing runs, even under severe conditions, excellent differentiation,
and good stability during prolonged storage.
The polymers used are addition polymers of styrene and
maleic anhydride or styrene and half-esters of maleic acid. ~d-
vantageously, the molecular weights of the polymers range between
1,000 and 100,000, preferably between 5,000 and 50,000.
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.: . The acid number which is obtainable in the final product
is determined by the monomer composition. Advantageously, the
.` acid numbers range between 30 and 500, preferably between 60
and 300.
The monomer composition ran~es between 30 and 80 per-
cent by weight, preferably between 40 and 70 percent by weight
of styrene and between 20 and 70 percent by weight, preferably
between 30 and 60 percent by weight of maleic anhydride or the
. partial esters of maleic acid r based upon the total weight of the
polymer.
As the alcohol componen ts contained in the unlts of the
maleic acid half-esters, aliphatic or aromatic, preferably lower
aliphatic, alcohols may be used, which have the followLng
molecular formulae:
Cn~l2n+1H with n = 1 to 30, preferably 1 to
; ~: 10, branched or linear,
Ar(CH2)mOH m = O to 4; and Ar = aromatic radical
- which optionally may have additional
substituents,
. 20 R-O-(CEI2-CH2O)lH
1 = 1 to 10, preferably 1 to 4, and
. R = aromatic or aliphatic radical,
. . Suitable polycondensation products of diazonium salts are
. mixed condensation products of condensable aromatic diazonium
-~. salts, for example, of diphenylamine-4-diazonium salts contain-
ing, in addition to the diazonium salt units, other units which
,',
are not sensitive to light and are derived from compounds which
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are capable of condensation, particularly from aromatic amines,
pilenols, thiophenols, phenol ethers, aromatic thioethers, aromatic
hydrocarbons, aromatic heterocycles and organic acid amides.
These condensation produc-ts are described in German Offenlegungs-
schrift No. 2, 024, 244 .
The diazonium salt units are preferably derived from com-
pounds which have the formula (Rl-R3-)pR -N2X, in which
X is the anion of the diazonium compound,
p is an integer from 1 to 3,
R is an aromatic radical which is capable of
condensation with an active carbonyl com-
; pound, in at least one position
R is a phenylene ~roup, and
R is a single bond or one of the groups
" ~(cH2)q-NR ~,
2 r
S (CH2)r NR
. -S-CH2Co-NR4-,
-o-R5-o-
: 20 -O-,
-S-, or
.: -Co -NR4 -,
wherein q is a number from 0 to 5,
r is a number from 2 to 5,
i R is a hydrogen atom, an alkyl group
having from 1 to 5 carbon atoms, an
aralkyl group having from 7 to 12
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. carbon atoms or an aryl group having
from 6 to 12 carbon atoms, and
- R is an arylene group having from 6 to
12 carbon atoms,
The compositions used in the process according to the
present inventlon generally contain the following amounts of dia-
zonium salt polycondensation product and polymeric binder:
5 to 90, preferably 10 to 70, percent by weight
- of diazonium compound, and
9S to 10, preferably 90 to 30, percent by weight
of polymeric binder.
As the polymerlc binders, the above-described copolymers
. .
of styrene and maleic anhydride or of styrene and partial or half-
esters of maleic acid are used. These are preferably the only
~,;; polymeric binders contained in the layerO
:
To stabilize the light-sensitive composition, it is advan-
tageous to add a compound having an acid character. Compounds
~' which may be used include mineral acids and strong organlc acids,
~; with phosphoric acid , sulfuric acid , perchloric acid , boric acid
' 20 or p-toluene sulfonic acid being preferred. Phosphoric acid is a
, particularly suitable acid,
:~,
Plasticizers, adhesion promoters, dyes, pigments and color
,
precursors also may be added to the compositions.
The types and quantities of such additions depend upon
the field of application for which the respective light-sensltive
composition is intended. In principle, care must be taken that
the hd~ed substances do not absorb an excessive portion of the
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actinic light whieh is required for cross-linking, because this
would result in a reduction of the practical sensitivity to light.
The light-sensitive compositions additionally may contain
dyes and/or pigments -which may serve to enhance the contrast
upon exposure and also to harden the la~er.
Suitable dyes are, for example, specified in U. S, Patents
Nos. 3,218,167 and 3~884~693O Particularly suitable are, ior
example, Vietoria~Pure Blue FGA or Rhodamine 6 GDN (C . I .
: .~
45,160~. To enhanee the image eontrast after exposure, MetaniL
Yellow (C.I. 13,065), Mathyl Orange (C.I. 13,025) or phenylaæo-
diphenylamine may be used.
Within the seope of the present invention, the followiny
weight proportions of the most important components of the light-
sensitive eomposition are preferred, which are, in each case,
based upon the content of non-volatile eonstituents, i . e ., the
constituents of the solid light-sensitive layer obtained after
evaporation of the solvent:
Copolymer of styrene and maleic acid 30 to 90%
derivative:
diazonium salt polycondensation 10 to 70%
product:
aeid: 0 to 10%
dye or pigment: 0 to 12%
dye which changes its color upon 0 to 5%.
exposure:
The support material is coated from appropriate organic
; solvents or solvent mixtures, by flow~coating, spraying or dipping.
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- As the solvents, alcohols, ketones, esters, ethers, and
the like may be used. The partial ethers of glycols or of keto-
alcohols have proved to be favorable solvents, for example,
ethylene glycol monomethyl ether.
Suitable layer supports are, for example, magnesium,
zinc, copper, mechanically, chemically or electrochemically
roughened aluminum, anodized aluminum, steel, and also poly-
ester film or cellulose acetate film, Perlon (~) gauze etc., the
;- surface of which, optionally, may have been suhjected to a pre-
1 Q treatment . The support material may function as the flnal layer
support or as a temporary support from which the light^~sensitive
` layer is transferred by lamination to the workpiece to be
proce s sed .
The reproduction materials prepared by means of the light-
- ,`` sensitive compositions of the invention serve, on the one hand,
to produce images on suitable supports or receptor sheets and,
' ~ on the other hand, to produce reliefs which are used as printing
forms, screens, resists, and the like.
In addition, it is also possible to use the light-sensitive
compositions for the formulation of UV-hardenable printing inks or
for the preparation of lacquers which are hardenable by ultraviolet
radiation and may be used for the protection of surfaces.
Primarily, the compositions are used for the production of
lithographic printing forms, in which aluminum is the preferred
support material.
It is particularly preferred to pretreat the aluminum used
for this purpose in the usual manner, for example, by a
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mechanical, chemical or electrochemical roughenlng process which
is, optionally, followed by an anodic oxidation. A further treat-
ment of thLs support material, for example, with polyvinyl phos-
phonic acid, alkali metal silicate, phosphate, hexa Eluorozirconate,
chromate, borate, polyacrylamide and cellulose derivatives is
advantageou s .
The reproduction materials obtained from the compositions
are processed in the conventional manner, by exposing imagewise
and washing-out the unexposed layer areas with a sultable
developer.
The reproduction material is exposed under an orlginal,
as is known in the art, using light sources which emit light with
.
the highest possible spectral fraction in the near ultraviolet re-
gion. The material also may be exposed by laser irradiation.
Suitable lasers for irradiation are shorter- wave lasers, for exam-
ple, Ar lasers, krypton ion lasers, helium/cadmium lasers,
emitting in the region between about 300 and 600 nm and, fo~
some layers, even C02 lasers, which emit at about 10.6~4m, or
YAG lasers emitting at about 1. 06 ~m.
As the developing solutions, aqueous-alkaline solutions
are used, which have a pH value in the range from 8 to 14,
preferably from 10 to 13, and which contain buffer sal ts, for
example, water-soluble alkali metal phosphates, silicates, borates,
carbonates, acetates or benzoates. Additional constituents used
are wetting agents, preferably anionic wetting agents and,
optionally, water-soluble polymers; volatile organic constituents
/
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are not employed.
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Development may be performed in the conventional manner
by dipping, spraying, brushing or wiping-over with a pad,
Surprisingly, the long-known copolymers of styrene and
maleic anhydride or half-esters of maleic acid, used in the print-
ing plates produced according to this invention, render an easy
development possible by means of aq-leous-alkaline solutions
which are free of organic solvents, yieldLng, at the same time,
a good sensitivity to light and long printing runs. As opposed to
printing plates comprising binders which contain other carboxyl
groups, the characteristics of the printing plates produced accord-
ing to the present invention correspond to those of prior art plates
which could be developed only with developers contalnin~ organic
. ., ~
~`,: solventsO
, .
-~ The printing plates produced according to the invention
:. ~ exhibit, in particular, high practical sensitivity to light, high
::
resolution, easy and scum-free developability, good stability in
: storage, sharp differentiation between image and non-image areas,
Iong printing runs, and a good compatibility of the layer con-
stituents in the solvents which are suitable for coating,
The examples which follow further illustrate the invention,
Parts by weight and parts by volume have the same relationship
as the g to the ml . Percentage s and weight ratios refer to
welght units, unless otherwise specified,
Example 1
A coating solution was prepared from the following compo-
nents:
20,0 parts by weight of a styrene-maleic acid ester copolymer,
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softenlng range from 160 to 175 C,
acid number 145-160,
10 . 0 parts by weight of a mixed diazo condensate, prepared
by condensing 1 mole of 3-methoxy-
diphenylamine-4-diazonium sulfate with
1 mole of 4,4'-bis-methoxy-methyl-diphenyl
ether in 85 percent concentration phos-
phoric acid and isolating as the mesitylene
` sulfonate and
~~ 10 0.8 part by weight of Victoria Pure Blue FGA (C.I, E~asic
Blue 81),
0 . 5 part by weight of phenylazodiphenylam;ne,
1, 2 parts by weight of phosphoric acid (85%) In
900 . 0 parts by weight of ethylene glycol monomethyl ether.
The solution was applied to an electrochemically roughened
and anodized alumlnum foil which had been after-treated with
polyvinyl phosphonic acid.
The copying layer was exposed for 20 seconds, using, as
the negative original, a silver film continuous-tone stepwedge
having a density range from 0. 05 to 3 . 05, with density increments
of 0.15 and, as the light source, a 5 kW metal halide lamp.
The exposed layer was treated with a developing solution
having the following composition:
5 . 0 parts by weight oi sodium lauryl sulfate,
1.5 parts by waight of sodium metasilicate,
1. 5 parts by weight of trisodium phosphate, and
92. 0 parts by weight of demineralized water,
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which was applied with a plush pad, whereby the non-image
areas were removed. The plate was then rinsed with water and
squeegeed .
In the copy obtained, step 5 of the stepwedge was still
fully blackened, The printing plate thus produced yielded 70, 000
printed sheets when used c~n a sheet-fed offset machine.
Examples 2 to 5: Similar results were obtained when the
.
~ folLowing styrene-maleic acid derivative polymers were used
. ~,
( instead of the binder specified In Example 1.
'; 10 Example 2
,. .
A styrene-malelc acid ester copolymer, havlng a softenlng
range from 140 - 160 C and an acid number of 145 - 160.
~ . .
Example 3
A styrene-maleic anhydride copolymer, the anhydride groups
of which were reacted with a low ~ molecular weight alcohol;
softening range from 217 - 225 C, acid number 200 - 220, mean
molecular weight about 20, OûO .
Example 4
^ A styrene-maleic anhydride copolymer having a softening
range Erom 205 - 220 C, an acid number of about 300, and a
mean molecular welght of about 5 0, 000 .
Example 5
A styrene-maleic anhydride copolymer, the anhydride groups
of which were reacted with a low - molecular weight alcohol;
softening range from 190 - 205 C, acid number about 200, mean
molecular weight about 10, 000,
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Example 6
The followLng components were used for the preparation of
a coating solution:
15 . O parts by weight of the binder used in Example 5,
15.0 parts by weight oE the diaæo polycondensate used in
Exa mple 1,
0 . 8 part by weight of Victoria Pure Blue FGA,
O. 5 part by weight of phenylazodiphenylamine,
2. 0 parts by weight of phosphoric acid (85%) in
950. û parts by weight of ethylene glycol monomethyl ether.
The solution was applied to an electrochemicalLy roughened
and anodized aluminum foil, which had been after-treated with
polyvinyl phosphonic acid, in a layer thickness of about 1. 0
g/m
The copying layer obtaLned was exposed for 22 seconds
under a negative original.
After developing with the developer used in Example 1,
, the plate was clamped into a small offset printing machine and
yielded more than 100, 000 printed sheets .
; 20 Example 7
Similar results were obtained when the binder specified in
Example 6 was replaced by the binder of Example 3.
; j Example 8
A coating solution was prepared from the following compo-
nents:
"~IJ 15 . O parts by weight of the polymer of Example 3,
..,
15 . O parts by weight of a mixed diazo condensate, prepared
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by condensing 1 mole of 3-methoxy-
diphenylamine-4-diazonium sulfate with
1 mole of 4,4'-bls-methoxy-methyl-
diphenyl ether in 8 5% concentration
phosphoric acid and isolating as the
methane sulfonate,
1. 6 parts by weight of Rhodamine 6 GDN (C. I. 45 ,160),
2. 0 parts by weight of phosphoric acid ~85%) in
~; 966 . 4 parts by wei~ht of ethylene glycoL monomethyl ether.
The sotution was applied to an electrochemically roughen-
ed and anodized aluminum foil which had been after-treated with
polyvinyl phosphonic acid.
The resulting copying layer was exposed for 35 seconds
under a negative original, using a 5 kW rnetal halide lamp.
The exposed layer was treated with the developer solution
of Example 1 in the customary manner. A perfect printing plate
was obtained, which yielded a long printin~ run on a sheet-fed
offset machine.
It will be obvious to those skilled in the art that many
modificatlons may be made within the scope of the present inven-
tion without departing from the spirit thereof, and the invention
includes alt such modifications.
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