Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LIGHT-SENSITIVE RECORDING MATERIAL AND PROOESS
FOR THE PRODUCTION OF THE MATERIAL
BACKGROUND OF THE INVENTION
The present invention relates to a negative-
working light-sensitive recording material for use in
the manufacture of planographic printing plates and to
a process for the production of the recording material.
Negative-working, presensitized, planographic
printing plates usually contain polycondensation pro-
ducts of diazonium salts, particularly products which
contain, in addition to diazonium salt units, units of
non-photosensitive compounds which are capable of con-
densation, for example, aromatic amines, phenols, aro-
matic thioethers, aromatic hydrocarbons, heterocyclic
compounds, or organic acid amides. Printing plates of
this kind are described in U.S. Patent No. 3,867,147.
When the light-sensitive layers of these printing
plates substantially comprise only the polycondensation
product, the exposed plates are readily developed with
purely aqueous solutions which appropriately include
wetting agents. These plates are, however, only
suitable for an average range of print runs. To obtain
larger print runs, it is generally necessary to add a
water-insoluble polymeric binder, for example, a poly-
vinyl acetal. The printing plates thus produced,
however, usually require the addition of organic
solvents to the developer to achieve smooth develop-
ment. If purely aqueous developer solutions are used,
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undissolved layer particles remain which contaminate
the developer and which may deposit in the non-image
areas of the plates to be developed therewith.
Binders have therefore been used which
dissolve in aqueous-alkaline solutions. Printing
plates of this type are described in European Published
Patent Applications No. 0,048,876 and No. 0,071,881,
which correspond to U.S. Patent No. 4,387,151 and
Canadian Patent No. 1,172,492, respectively. These
plates are readily developed with purely aqueous devel-
opers, with no undissolved layer particles being
formed, thus resulting in good print runs. The plates,
however, frequently exhibit a retarded ink acceptance
in the printing machine. It is assumed that this is
caused by layer constituents reacting with hydrophylic
desensitizing agents which are applied after develop-
ment in order to protect the plate. Reactions of this
type may occur both in the dark and in the light.
Retarded acceptance of ink may also be caused by
hydrophylization of the layer surface, which is pro-
duced by contact of the layer with alkaline auxiliary
agents normally employed in printing.
Another disadvantage of these printing plates
is that the print run is reduced when alkaline dampen-
ing solutions are used. This is probably due to the
relatively good solubility of the binders in alkali.
Moreover, most of the printing plates devel-
oped with aqueous developers show a smoother gradationthan printing plates developed with organic solvents.
As a result, it is considerably more difficult to
determine the proper development time by means of a
stepwedge, and, in the printing process, a marked
increase of tonal rendering occurs, compared with the
screened original. Up to now, these disadvantages
have, nevertheless, been tolerated in view of the eco-
logical advantages of aqueous development.
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J Z84~3~
It is known from U.S. Patent No. 3,136,637 to
reduce the sensitivity to water and the hydrophilic
character of printing plates based on the diazonium
salt-formaldehyde condensation products in such a way
that a covering coating comprising a water-insoluble
resin can be applied to the light-sensitive layer. In
this case, development must again be carried out with a
developer containing organic solvents.
In German Auslegeschrift No. 15 22 501
(corresponding to British Patent No. 1,192,088), a
similar printing plate is described, in which a water-
insoluble, light-sensitive layer comprising a
1,4-quinone diazide, and optionally a water-insoluble
resin, is applied onto a water-soluble light-sensitive
layer comprising a diazonium salt condensation product.
The applied layer has a relatively low light-
sensitivity, and the print run obtained from the
printing forms so produced is comparatively small.
German Offenlegungsschrift No. 25 23 719
describes a light-sensitive material which comprises a
water-soluble, light-sensitive layer of azides, chal-
cones or diazonium salt condensates and water-soluble
polymers, and an overlying layer of an organic synthe-
tic resin which is permeable to and insoluble in water.
Development is carried out with water, the unexposed
areas of the water-soluble, light-sensitive layer being
dissolved in the process. The overlying layer of
synthetic resin must then be removed by rubbing. This
type of development is, to a large extent, dependent on
the skill of the person carrying out processing. There
is always a risk that image areas of the layer will be
torn off or that the covering layer will not be pro-
perly removed in the non-image areas. The material is
unsuitable for automatic development in a processing
line and the developer naturally contains undissolved
particles of the covering layer. In addition, the
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plate described in this publication is not suitable for
the production of large print runs.
It is also known to coat positive-working
light-sensitive materials based on l,2-quinone diazides
with water-insoluble covering layers comprising organic
polymers. According to German Offenlegungsschrift
No. 24 26 159 (corresponding to British Patents
No. 1,478,333 and No. 1,478,334), part of the thickness
of a 1,2-quinone diazide layer is replaced by a water-
insoluble polymer layer, in order to enhance light-
sensitivity. In this case, however, an optimum print
run is not obtained, since adhesion of the covering
layer is too low. According to German Offenlegungs-
schrift No. 24 61 515 (corresponding to British Patent
No. 1,488,350), an adhesion-promoting agent is there-
fore added to the oleophilic covering layer to remedy
this disadvantage. Silane, among others, is used as
the adhesive agent. The developers employed comprise
aqueous solutions containing considerable quantities of
organic solvents. The silane compounds and/or the
reaction products of these compounds, which are washed
off in the development process, produce a more rapid
contamination of the developer.
Moreover, it is known from European Patent
No. 0,008,038 (corresponding to U.S. Patent
No. 4,288,520) to produce light-sensitive layers which
are developable with water, by the application of a
stable aqueous dispersion of a polymer which is insol-
uble in water. The dispersion contains a diazonium
salt polycondensation product dissolved therein. These
materials similarly do not yield optimum print runs,
since the image areas exhibit a certain sensitivity to
water and aqueous solutions.
J 28491~
SUMMARY OF THE INVENTION
It is, therefore, an object of the present
invention to provide a light-sensitive recording
material for use in the manufacture of planographic
printing plates based on diazonium salt polyconden-
sation products which can be developed with purely
aqueous solutions.
Another object of the present invention is to
provide a light-sensitive recording material for use in
the manufacture of planographic printing plates based
on diazonium salt polycondensation products which
yields printing forms of high print run performance.
Yet another object of the present invention
is to provide a light-sensitive recording material for
use in the manufacture of planographic printing plates
based on diazonium salt polycondensation products which
is properly developed without any deposition of par-
ticles in the developer.
Still yet another object of the present
invention is to provide a light-sensitive recording
material for use in the manufacture of planographic
printing plates based on diazonium salt polyconden-
sation products which produces image areas having good
and permanent ink receptivity.
In accomplishing these and other objects of
the present invention, there has been provided in
accordance with one aspect of the present invention, a
light-sensitive recording material comprising a sup-
port, a light-sensitive recording layer which includes
a light-sensitive compound comprising a condensation
product which comprises recurrent units A-N2X and B
which are linked by divalent intermediate members
derived from a carbonyl compound which is capable of
condensation, and a binder, the A-N2X units being
derived from compounds of the general formula
3491~
(Rl-R3-) pR2--N2X
wherein:
X is the anion of the diazonium compound,
p is an integer from about 1 to 3,
Rl is a carbocyclic or heterocyclic aromatic radical
which is capable of condensation in at least one
position,
R2 is an arylene group of the benzene or naphthalene
series,
R3 is a single bond or one selected from the group
consisting of:
-(CH2)~-NR4-,
-O- (CH2 ) r-NR4-,
-S- (CH2) r-NR4-,
-S-CH2Co-NR4-,
-o-R5 -o-,
--O--,
-S-, and -Co-NR4-,
wherein:
q is an integer from about 0 to 5,
r is an integer from about 2 to 5,
R4 is a hydrogen atom, an alkyl group having from
about 1 to 5 carbon atoms, an aralkyl group ha~ing
from about 7 to 12 carbon atoms or an aryl group
having from about 6 to 12 carbon atoms, and
R5 is an arylene group having from about 6 to 12 car-
bon atoms and B denotes the radical of an aromatic
amine, a phenol, a thiophenol, a phenol ether, an
aromatic thioether, an aromatic hydrocarbon, an
aromatic heterocyclic compound or an organic acid
amide, which is free from diazonium groups; the
condensation product comprises from about 0.01 to
50 units B for each unit A-N2X, and the binder
includes a water-insoluble polymer which is soluble
in aqueous-alkaline solutions, and a covering layer
present on the light-sensitive recording layer
which comprises a water-insoluble polymer.
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In a preferred embodiment, the covering layer
further co~prises a diazonium salt condensation product
as defined above. Additionally, it is preferable if
the covering layer has a layer weight from about 0.2 to
1 g/m2, and further comprises a surface-active agent
and a protective colloid. Advantageously, the water-
insoluble polymer of the covering layer comprises a
homopolymer or copolymer of an alkyl acrylate or an
alkyl methacrylate having from about 1 to 12 carbon
atoms in the alkyl group,ofavinyl ester of a carboxylic
acid having from about 2 to 12 carbon atoms,ofa vinyl
alkyl ether having from about 2 to 8 carbon atoms in
the alkyl group, oro~a vinyl-aromatic compound having
from about 8 to 12 carbon atoms.
In accordance with another aspect of the pre-
sent invention, there has been provided a process for
the productionof a light-sensitive recording material,
which comprises the steps of coating a support with a
light-sensitive recording layer which includes a light-
sensitive compound comprising a condensation product
which comprises recurrent units A-N2X and B, which are
linked by divalent intermediate members derived from a
carbonyl compound which is capable of condensation, and
a binder, the units A-N2X being derived from compounds
of the general formula
(Rl--R3 - ) pR2--N 2X
wherein:
X is the anion of the diazonium compound,
p is an integer from about 1 to 3,
0 Rl is a carbocyclic or heterocyclic aromatic radical
which is capable of condensation in at least one
position,
R2 is an arylene group of the benzene or naphthalene
series,
R3 is a single bond or one selected from the group
--7--
~ 2~4~
consisting of:
~(CH2)q~NR4~~
~o-(CH2)r-NR4
-S- (CH2 ) r-NR4-,
-S-CH2Co-NR4-,
-o-R5-O-,
--O--,
-S-, and -Co-NR4-,
wherein:
q is an integer from about 0 to 5,
r is an integer from about 2 to 5,
R4 is a hydrogen atom, an alkyl group having from
about 1 to 5 carbon atoms, an aralkyl group having
from about 7 to 12 carbon atoms or an aryl group
having from about 6 to 12 carbon atoms, and
R5 is an arylene group having from about 6 to 12 car-
bon atoms and B denotes the radical of an aromatic
amine, a phenol, a thiophenol, a phenol ether, an
aromatic thioether, an aromatic hydrocarbon, an
aromatic heterocyclic compound or an organic acid
amide, which is free from diazonium groups; the
condensation product comprises from about 0.01 to
50 units B for each unit A-N2X, and the binder
includes a water-insoluble polymer which is soluble
in aqueous-alkaline solutions, coating the
recording layer with a stable aqueous dispeesion of
a water-insoluble polymer, and drying the aqueous
dispersion to produce a covering layer on the
recording layer.
Other objects, features and advantages of the pre-
sent invention will become apparent from the detailed
description of preferred embodiments which follows.
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~ 28491~
DETAILED DESCRIPTION OF THE ~REFERRED EMBODIMENTS
The present invention is based on a light-
sensitive recording material comprising a support and a
light-sensitive recording layer which comprises, as the
light-sensitive compound, a condensation product
comprising recurrent units A-N2X and B which are linked
by divalent intermediate members derived from a car-
bonyl compound which is capable of condensation. The
units A-N2X are derived from compounds of the general
formula
(Rl-R3-) pR2-N2X,
wherein:
X is the anion of the diazonium compound,
p is an integer from about 1 to 3,
Rl is a carbocyclic or heterocyclic aromatic radical
which is capable of condensation in at least one
position,
R2 is an arylene group of the benzene or naphthalene
series,
R3 is a single bond or one selected from the group
consisting of:
~(CH2)q~NR4~~
-o-(CH2)r-NR4-,
-S- (CH2) r-NR4-,
-S-CH2Co-NR4-,
-O-R5-o-,
--O--,
-S-, and -Co-NR4-,
whereir:
q is an integer from about 0 to 5,
r is an integer from about 2 to 5,
R4 is a hydrogen atom, an alkyl group having from
about 1 to 5 carbon atoms or an aralkyl group
having from about 7 to 12 carbon atoms or an aryl
_g _
~ ~491X
group having from about 6 to 12 carbon atoms, and
R5 is an arylene group having from about 6 to 12 car-
bon atoms, and
B denotes the radical of an aromatic amine, a phenol,
a thiophenoi, a phenol ether, an aromatic
thioether, an aromatic hydrocarbon, an aromatic
heterocyclic compound or an organic acid amide,
which is free from diazonium groups.
The condensation product contains, on an
average, from about 0.01 to 50 units B for each unit
A-~2X. The binder includes a water-insoluble polymer
which is soluble in aqueous-alkaline solutions. The
recording material also includes a covering layer which
comprises a water-insoluble polymer. The covering
layer is present on top of the light-sensitive
recording layer.
The present invention also provides a process
for the production of a light-sensitive recording
material, in which a light-sensitive recording layer
of the above-indicated composition and a covering
layer are applied to a support. The process of the
invention is characterized in that the covering layer
is produced by coating the recording layer with a
stable a~ueous dispersion of a water-insoluble polymer
which is then dried. The covering layer preferably
has a layer weight in the range from about 0.2 to 1
g/m2. According to a preferred embodiment, the
covering layer comprises, in addition to the water-
insoluble polymer, a diazonium salt polycondensation
product which is preferably water-soluble.
Homopolymers or copolymers of alkyl acrylates
or alkyl methacrylates having from about 1 to 12 carbon
atoms in the alkyl group,of vinyl esters of carboxylic
acids having from about 2 to 12 carbon atoms,ofvinyl
alkyl ethers having from about 2 to 8 carbon atoms in
the alkyl groupor of vinylaromatic compounds having from
--10--
~ ~84~1~
about 8 to 12 ca bon atoms are preferably used as the
water-insoluble polymers contained in the covering
layer. These polymers are preferably insoluble in
aqueous alkali.
Examples of suitable polymers include polyvi-
nyl acetate, polyvinyl propionate, polyvinyl versatate,
polyvinyl nonanate, polystyrene, poly-4-methyl-styrene,
poly-~ -chloro-styrene, polyisopropyl-styrene, poly-
methyl methacrylate, polybutylacrylate, poly-2-ethyl-
hexylmethacrylate, polyvinyl isobutylether and the
copolymers and terpolymers of these monomers, for
example, a terpolymer comprising vinyl chloride, ethy-
lene and vinyl acetate.
In a covering layer comprising a diazonium salt
condensation product, the latter basically can have the
same structure as described above for the components of
the light-sensitive layer. The anion of the salt is
preferably of such a nature that the salt is water
soluble. Suitable anions include, for example, sul-
fates, chlorides, phospha~es and aliphatic sulfonates.
The diazonium salt condensation product, if present, is
preferably included in the covering layer in a quan-
titative proportion from about 10 to 50 percent by
weight, relative to the non-volatile constituents of
the layer.
The components of the covering layer are
applied to the light-sensitive layer in the form of a
stable aqueous dispersion. The dispersion comprises
surface-active dispersing agents and/or protective
colloids, as is typical. Production and application of
the coating dispersion are known per se and are, for
example, effected in the same way as described in U.S.
Patent No. 4,288,520.
The light-sensitive layer - or optionally the
lower light-sensitive layer - comprises diazonium salt
polycondensation products which are normally water-
~ Z849~2
insoluble, as is known in the art. As already mentioned
above, these condensation products are described in
U.S. Patent No. 3,867,147. The layer additionally
includes an àlkali-soluble polymer as a binder.
Suitable polymers are described in European Published
Patent Applications No. 0,071,881 and No. 0,048,876
(corresponding to U.S. Patent No. 4,387,151 and
Canadian Patent No. 1,172,492, respectively). Pre-
ferred polymers include copolymers comprising carboxyl
groups and polymers having sulfonyl urethane groups.
The layers generally comprise from about 5 to 90% by
weight, preferably from about 10 to 70% by weight, of
diazonium compound and from about 95 to 10% by weight,
preferably from about 90 to 30% by weight, of poly-
meric binder. The layers may additionally includeacids, for example, phosphoric acid, plasticizers,
adhesion promoters, dyes, pigments, color precursors
and other polymers.
The preferred support comprises aluminum which
may be roughened by mechanical, chemical and/or elec-
trochemical processes and which is optionally anodic-
ally oxidized. Other suitable materials include, for
example, steel, chromium, and other support materials
which are used in the practice of planographic
printing.
Processing of the present recording material
is carried out in the known manner by image-wise
exposing and washing off the unexposed layer areas
with an aqueous-alkaline developer which usually has a
pH in the range from about 8 to 14, preferably from
about 10 to 13. In addition to alkali and buffer
salts, the developer may include wetting agents and
other customary additives. Preferably, no organic
solvents are added.
In the development process, the unexposed por-
tions of the light-sensitive layer and the
-12-
~ 2#4~9~X
corresponding areas of the covering layer are dissolved
and/or dispersed in the developer. In these areas, the
components of the covering layer are readily dispersed
in the developer, while at least the major part thereof
remains on the light-sensitive layer in the exposed
areas. This differentiation is enhanced by adding
diazonium salt condensation products to the covering
layer. The water-insoluble components of the covering
layer are rapidly distributed in the developer to form
a stable dispersion, i.e., there are no macroscopically
visible clods or particles formed and deposited, which
is obviously due to the dispersing agents distributed
in the covering layer.
The covering layer remains on top of the
light-hardened areas of the light-sensitive layer and
is firmly attached to the underlying layer. In these
areas, the layer exhibits an excellent oleophilic
character, i.e., the image areas of the printing form
accept printing ink immediately upon the passage of the
first printed sheets. The print run is also increased
by the covering layer. The printing forms have a
clearly steeper gradation than corresponding printing
forms which are not provided with a covering layer of
the type described herein.
In the following examples, preferred embodi-
ments of the invention are described. Unless otherwise
indicated, percentages and quantitative proportions
relate to units by weight. Parts by weight (p.b.w.)
and parts by volume (p.b.v.) are related as g to cm3.
Example 1
A coating solution comprising:
97.0 p.b.w. of the product obtained by reacting a
polyvinyl butyral (molecular weight from
70,000 to 80,000; 71% by weight of vinyl
butyral units, 2% by weight of vinyl
~ 2~491~
acetate units and 27% by weight of vinyl
alcohol units) with propenyl sulfonyl
isocyanate (softening point approxi-
mately 161C, acid number 18.0),
48.3 p.b.w . of a diazonium salt polycondensation
product obtained from 1 mole of
3-methoxydiphenylamine-4-diazonium
sulfate and 1 mole of 4,4'-bis-methoxy-
methyl-diphenylether in an 85% strength
phosphoric acid and isolated as the
mesitylene sulfonate,
4.8 p.b.w. of phosphoric acid (85% strength),
3.5 p.b.w. of Victoria Pure Blue FGA (C.I. Basic
Blue 81) and
1.6 p.b.w. of phenylazodiphenylamine in
3500 p.b.w. of 2-methoxy ethanol and
1036 p.b.w. of tetrahydrofuran
was applied to an electrochemically roughened and anod-
ically oxidized aluminum foil which had been post-
treated with polyvinyl phosphonic acid. After drying,
the layer weight was 0.8 g/m2. The dry layer was
coated with an aqueous emulsion based on polystyrene
(Styrofan 2D ~ , manufacturer BASF; anionic emulsifier
system, particle size 0.5 /um, tear strength of the
film 100 kg/cm2). The dry layer had a weight of 0.5
g/m2. The presensitized printing plate was placed
under a negative original and exposed for 35 seconds to
the light of a 5 kW metal halide lamp.
The exposed layer was treated with a developer
solution of the following composition:
5 p.b.w. of sodium lauryl sulfate
1.5 p.b.w. of sodium metasilicate x 5 H2O,
1 p.b.w. of trisodium phosphate x 12 H2O,
92.5 p.b.w. of water
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~ X~49~2
using a plush pad, the unexposed layer areas being
removed in the process which was followed by rinsing
with water and drying.
In an offset printing machine, two plates,
i.e., the plate prepared as described above and a
corresponding plate without a covering layer, were
clamped side by side to a cylinder. One half of each
plate was treated with a strongly alkaline roller
washing fluid (Feuchtofix ~ , while the other half was
left untreated. The four areas of the plate cylinder
accepted ink at different rates. The following table
indicates, in each case, the number of printed sheets
produced until ink was completely accepted.
Plate With Plate Without _
Coverina Layer Coverinq Layer
._ _ _ _
alkaline-treated 30 100
untreated 15 20
The table shows that the plate produced
according to the present invention was by far less sen-
sitive to alkali than a corresponding plate without a
covering layer.
Gradation in the inked state, i.e., the number
of intermediate steps which were not completely
blackened, was 2 in the plate of the invention and 4 in
the comparative plate (KALLE stepwedge BK 01). The
print run increased by 20%, in comparison with the
uncovered comparative plate.
Example 2
Example 1 was repeated with the following
differences:
a) the binder of the organic coating solution
was replaced by the same quantity of a copolymer
comprising styrene and maleic anhydride (1:1);
4~
b) the solution used for the development
included
5 p.b.w. of the triethanol ammonium salt of lauryl
sulfate,
1 p.b.w. of sodium metasilicate x 5 H2O and
1.5 p.b.w. of trisodium phosphate x 12 H2O in
92.5 p.b.w. of water;
c) the covering layer was produced by coating
with a solution of
3 p.b.w. of an aqueous emulsion of polyvinyl isobutyl-
ether (particle size 0.5 to 3 /um),
1 p.b.w. of a diazonium salt polycondensation product
prepared from 1 mole of 3-methoxydiphenyl-
amine-4-diazonium sulfate and 1 mole of
4,4'-bis-methoxymethyl-diphenylether in an
85% strength phosphoric acid and isolated as
the methane sulfonate, and
l.p.b.w. of a non-ionic wetting agent based on an
ethoxylated alkyl phenol (Triton x 100 ~ .
The weight of the dry covering layer was 0.65
g/m2. Processing was carried out in a manner analogous
to Example 1. The sensitivity to alkali was even lower
than in the case of using a covering layer without
diazo compound. Particularly noticeable was a facili-
tated determination of exposure time (hard gradation)
and an improved visual contrast upon exposure.
Example 3
Example 1 was repeated, except that an
emulsion of a terpolymer comprising vinyl chloride,
ethylene and vinyl acetate was used as the polymeric
binder of the covering layer. The results were similar
to those of Examples 1 and 2.
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