Note: Descriptions are shown in the official language in which they were submitted.
85/K 024 ~ ;5~346 TR~NSLATION
Light-sensitive diazonium salt polycondensation product
and light-sensitive recording material prepared therewith
The present invention relates to a light-sensitive diazo-
nium salt polycondensation product which can be used in
the production of pre-sensitized lithographic printing
plates and other light-sensitive materials, for example
photoresists and color proofing films.
U S. Patent No. 4,533,62~ has disclosed diazonium salt
' co-condensation products for use in the production of li-
thographic printing plates. These co-condensates are ob
tained by condensing two different aromatic diazonium
salts and aldehydes or specific condensible aromatic com-
pounds with halogenomethyl, hydroxymethyl, or alkoxyme-
thyl substituents. The condensation products yield prin-
ting plates which have a high photospeed and a good sto-
rage stability. As the diazonium salt anions for a
water-soluble product, HS04-, H2P04-, Cl-, and Br~ are
mentioned. Anions mentioned for condensation products
which are soluble in water and in organic solvents in-
clude methane sulfonate, sulfosalicylate, and p-toluene
sulfonate, whereas condensates which are soluble in orga-
nic solvents are isolated as the mesitylene sulfonates or
other aryl sulfonates, tetrafluoroborates and hexafluoro-
phosphates.
Although some of these products are soluble in pure wa-
ter, it is usually difficult to develop the printing pla-
tes obtained from these products with pure water.
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It is therefore an object of the present invention to
provide a diazonium salt polycondensation product of the
above-indicated generic type, which is comparable with
the prior art products in view of storability and photo-
speed, but which lends itself to the production of prin-
ting plates which can be developed with pure water, wi-
thout leaving any residue.
The invention provides a light-sensitive polycondensation
product compr.ising recurrent units corresponding to for-
_ -- mulae Al and A2
~ (Al) (A2)
which are linked together by methylene groups and in
which
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Rl and R2 stand for al~oxy groups having from 1 to
4 carbon atoms,
~3 is a hy~rogen atom or an alkyl group, and
R4 is a hydrogen atonl or an alkoxy group
having from 1 to 4 carbon atoms,
the total number of units Al and ~2 being, on an average,
from 2 to 160 and the ratio of units Al : A2 ranging from
0.125:1 to 8:1.
The product of the present invention is characterized in
that X is the anion of an acid containing fluorine atoms.
Preferably X i5 the fluoride, tetrafluoroborate, hexa-
fluorophosphate or hexafluorosilicate anion.
The invention further provides a light-sensltive recor-
ding material comprising a support and a light-sensitive
layer which contains, as the light-sensitive substance, a
polycondensation product of the above-indicated
composition.
The supports used comprise materials which are customari-
ly used as supports for printing plates,~especially li-
thographic printing plates. In particular, metals such
as steel, chromium, copper, ~inc, magnesium and prefera-
bly aluminum can be employed.
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In the polycondensation products of the present inven-
tion, the units Al and A2 are not arranged in a specific
sequence.
The total number of units Al and A2 preferably ranges
from 2 to 30 and the ratio of units preferably ranges
from 0.5:1 to 2:1.
The light-sensitive diazonium salt polycondensation pro-
ducts of the invention may be present in admixture with
other constituents, for example, binders, dyes, pigments,
solvents, plasticizers, wetting agents and acid.s, which
are added as required
The compounds of the present invention can generally be
described as the products of a condensation reaction, in
which at least two aromatic diazonium compounds which are
capable of participating in a condensation reaction, are
reacted with formaldehyde.
The reaction media used in the condensation reaction are
strong to moderately strong acids, in particular inorga-
nic acids, the preferred inorganic acids being phosphoric
acid and sulfuric acid.
Examples of suitable monomeric diazonium compounds are
diphenylamine-4-diazonium sulfate, 3-alkoxy-diphenylamine-
4-diazonium sul~ate, 2,5-dialkoxy-diphenylsulfide-4-
diazonium sulfate, particularly 2,5-dialkoxy-4-
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(p-tolylmercapto)-benzenediazonium-tetrachLorozincate,
the alkoxy groups having, in each case, from l to 4, pre-
ferably 1 or 2 carbon atoms. As the partner in the con-
densation reaction, paraformaldehyde or a modification
thereof is preferably used.
If sulfuric acid is employed, the acid concentration is
preferably 96%, lower concentrations being, however, also
possible. The temperatures of the acid may ranye rom
the freezing point of the acid up to room temperature;
preferred temperatures are between about 6 to 15 C. In
a condensation reaction which is carried out in phospho-
ric acid, an acid concentration of 85~ is generally ap-
propriate. In some cases, it is necessary to have an in-
creased activity, in order to obtain the desired result.
Then P2Os is advantageously added to raise the concentra-
tion of the phosphoric acid. Temperatures may range bet-
ween 20 and 50 ~C, in particular between 35 and 45 C, if
phosphoric acid is used.
One of the monomeric diazonium compounds used to prepare
the condensation products of the present invention is a
diarylsulide diazonium compound which preferably has two
alkoxy substituents attached to the ring carrying the
diazonium group.
The monomeric diazonium compounds are usually added one
after another, within a period from 30 to 240 minutes, to
the acid used or the condensation raction and thereafter
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paraformaldehyde is slowly added, such that temperature
variations are obviated. The reaction time generally
ranges from 15 to 300 minutes, preerably from 30 to 240
minutes. A post-reaction period under isothermal condi-
tions is advisable to ensure the complete reaction of the
reactants. Post-reaction may be carried out for a period
between ~ and 48 hours, preferably for 10 to 30 hours
and, in particular, for 12 to 20 hours.
The condensation mixture obtained is poured slowly and
with stirring into 5 to 10 times the quantity of water.
To this solution, the e~uivalent quantity of a fluorine-
containing acid or a solution of its salt is slowly added
dropwise, as a result of which the reaction product is
deposited in the form of a yellow, solid product which can
be isolated. Aqueous solutions of NaF, HBF4, NaBF4,
H2SiF6 or HPF6 are preferably used.
Light-sensitive mixtures which are used in the production
of light-sensitive materials, such as lithographic prin-
ting plates, photoresists or color proofing films, nor-
mally comprise mixtures of aromatic diazonium salts, bin-
ders, dyes or pigments, indicators and stabilizers, which
are coated onto suitable supports, usually aluminum
supports.
The diazonium compound of the present invention can be
processed in organic solvents, similarly to the diazonium
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compounds known in the art. The quantity of the diazoni-
um compound ranges between 15 and :L00% by weight, prefe-
rably between 20 and 80~ by weight, based on solids.
To increase the print run, binders may be added to the
diazonium compound. Suitable binders include, for exam-
ple, polyvinyl acetate/maleate copolymers, polyvinyl
alkyl ethers, polyurethanes, polyvinyl acetals, polyols,
polyacrylates, polyvinyl acetates, and phenol formalde-
hyde resins. The binders are usually added in quantities
between 5 and 75% by weight, preferably between 15 and
60~ by weight, based on the solids content of the coating
mixture.
Pigments or dyes are usually employed as colorants. Sui-
table dyes include triarylmethane and xanthene dyes. The
amount of colorant ranges between 1 and 10% by weight,
preferably between 2 and 7% by weight.
Below the invention i5 explained in detail by means of
examples. Percentages and quantitative proportions rela-
te to weight.
Example of Preparation 1 (Comparison)
8.8 g of diphenylamine-4-diazonium sulfate and 59 g of
2,5~dimethoxy-4-p-tolylmercapto-benzenediazonium
tetrachlorozincate are added to 223 g of sulfuric acid
(96% strength). As soon a~ these additions have been
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completely dissolved by steadily stirring at 10 ~C, 4.5 g
of paraformaldehyde are slowly added within a period of 3
hours. During this period, care must be taken to main-
tain a constant temperature. Stir:ring is continued for
10 hours at 10 C. The reaction mixture is then dissol-
ved in 2 1 of deionized water and precipitated as the
p-toluenesulfonate.
Example of Preparation 2
The condensation is carried out as described in Example
1. Instead of precipitating as the p-toluenesulfonate,
54 g of tetrafluoroboric acid (32% strength) are slowly
added dropwise to the reaction solution diluted with wa-
ter. The reaction product is precipitated and is then
isolated.
Example of Application 1
The two reaction products obtained in Example of Prepara-
tion 1 (Comparison) and Example of Preparation 2
(according to the invention) are used to prepare light-
sensitive coating solutions of the following composition:
1.50 % of diazonium salt polycondensate,
0.15 % of Basonyl Red 540 dye,
0.40 % o H3PO4 (85% strength), and
97.97 % of 2-methoxy-ethanol.
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For comparison, the two solutions are, in each case, spin-
coated upon an aluminum plate which has been electro-
chemically roughened, anodically oxidized and rendered
hydrophilic by methods known in the art. After drying,
the two plates are exposed side by side under a metal
halide lamp.
Onehalf of each plate is used to test the complete deve-
lopment by means of pure water, and the other half is
used to test the storage stability in the unexposed
state.
To test the developability with pure water, without manu-
ally wiping over or rubbing with a sponge, cotton pad or
the like, the two plate halves according to Examples of
Preparation 1 and 2 are arranged side by side, briefly
rinsed with a water spray and dried. The plates develo-
ped in this manner are again exposed side by side without
using an original, for three tlmes the period required
for image exposure and are then moistened and inked with
a greasy printing ink, either by hand or in an offset
printing machine. It is seen that the layer according to
Example of Preparation 1 clearly picks up ink even in the
non-image areas, i. e. it cannot be completely developed
with a water spray. As against this, the layer according
to Example of Preparation 2 does not show any scumming
after treatment with greasy ink, i. e. it can be ccmpletely
developed merely by rinsing with a water spray.
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To test the unexposed plate material for storage stabili-
ty, a quick test involviny storing of the material at
100 C is appropriately carried out:. For this purpose,
several plates according to Examples of Preparation 1 and
2 are stored side by side in a drylng oven heated at
9S C to 110 ~C. Every 10 minutes one plate each is re-
moved, cooled, exposed under a test film original in the
usual manner, briefly developed by means of a water spray
without manually wiping over and then treated with a gre-
asy printing ink. The extension of the photographic step
wedge which has also been recorded on the plate in ~he
test exposure, the occurrence of staining and the picking
up of ink in the non-image areas with increasing storage
period are the criteria which serve to judge the storage
stability of the materials. In the present comparison,
the plates according to Example of Preparation 1 are sto-
rable for only 60 to 80 minutes at 100 C, whereas the
plates according to the present invention are storable
for 160 to 200 minutes. This corresponds to a difference
in storage stability of several months for storage at
room temperature.
It is a particular advantage of the layer according to
the present invention that, irrespective of its conside- -
rably better storage stability, it is just as light-
sensitive as the layer of the comparison test. This
signifies that, in this case, photospeed and storage sta-
bility are not reciprocal, as is otherwise generally as- -
sumed and has been described many times in the literatu-
re.
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Example of ~eplication 2
A light-sensitive coating solution is prepared, which has
the following composition:
1.50 % of the diazonium saLt polycondensate ac-
cording to Example of Preparation 2,
0.15 ~ of crystal violet,
0.60 % of H3PO4 (85% strength),
0.50 % of a vinyl acetate/maleate copolymer,
- ''97.25 % of 2-methoxy-ethanol.
Coating, exposure and development are carried out as in-
dicated in Example of Application 1. Storage stability at
100 C is from 160 to 180 minutes. When the plate so pre-
pared is used for printing on a commercial offset prin-
ting machine, 130,000 good prints are obtained.
Instead of the indicated copolymer, a polyvinyl ethyl
ether or a copolymer of ethyl acrylate, methyl methacry-
late, acrylic acid and methacrylic acid can equally suc-
cessfully be used as a binder.
Example of Preparation 3
6 g of diphenylamine-4-diazonium sulfate and 41.8 g of
2,5-diethoxy-4-p-tolylmercapto-benzenediazonium tetra-
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chlorozincate are added to 150 g of sulfuric acid (96% strength)
and after completely dissolving with stirring at +10 C,
3.0 g of trioxane are slowlv added to the mixture within
2 hours. Stirring is continued for 17 hours at +10 C. The
crude product is then poured into 1.3 1 of wa-ter and 200 g o~
H2SiF6 (34% strength) are added dropwise with stirring. The
reaction product is deposited as a yellow solid substance
which is removed by filtration and dried.
Example of Application 3
The following components are used to prepare a light-
sensitive coating solution:
1.50 % of the diazonium salt polycondensate ac-
cording to ~xample of Preparation 3,
0.15 % of Astrazone red-violet 3RN,
0.40 % of H3PO4 (85% streng-th),
87.95 ~ of 2-methoxy-ethanol,
lO.00 ~ of butyrolactone.
The solution so prepared is used for coating an aluminum
plate which has been roughened by brushing with an
aqueous abrasive suspension. The coated plate is exposed
under a photographic negative and developed with pure wa-
ter. Upon inking with a greasy printing ink, a perfect
printing iorm is obtained,
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Example of Preparation 4
The condensation is carried out as described in Example
of Preparation 3. Instead of H2SiF6, 50 g of sodium
fluoride are slowly added with stirring to the reaction
solution diluted with water. Aftersaturating with common
salt, the condensation product is deposited as a yellow
solid substance which can readily be isolated.
Example of Preparation 5
The condensation is carried out as described in Example
of Preparation 1, however, 50 g of NaBF4 are used to pre-
cipitate the condensation product in an aqueous solution,
as a greenish solid substance.
Examples of Ap~ication 4 and 5
An aluminum plate which has been roughened by brushing
with an aqueous abrasive dispersion and then anodically
oxidized is coated with the coating solution of Example
of Application 3, but which contains the condensation
product of Example of Preparation 4 as the light-
sensitive compound. After exposure under an original,
the plate is developed with water and can then be proper-
ly inked for printing
Another aluminum plate is coated as in Example of Appli-
cation 2, but using the condensation product of Example
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5, and is exposed under an original. The plate is clam-
ped onto a printing machine in subdued light. After
starting the machine, the plate is developed immediately
and accepts ink in the image areas. About 50,000 prints
can thus be produced.
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