Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Th~s invention relates to lithographic printing plates.
More particularly it relates to an improved support ~or use in
the preparat.ion of such plates, radiation-sensitive elements pre-
pared -~rom such supports and lithographic printing plates pre-
pared from said elements.
Radiation sensitive elements, which may be converted -to
lithographic printing plates, comprise a radiation-se~sitive
~eproduction layer, in which the printing image is photomechan-
ically produced, and a support which, from the produc-tion of the '
material until its processing into a printing plate, carries the
reproduction layer and is stored therewith until the material i5
used. AEter the production of the printing image, the support
carries the printing image and simultaneously forms the image
background in the image-free areas. It is a requirement of a
support sui.table for the production oE a printing plate ~hat the
printing image areas developed from the reproduction layer o-f the
material adhere thereto very Eirmly. Further, it must have a.
hydrophilic surEace and the repelling eEEect thereoE with
respect to oleophilic printing inks must not be reduced in
efEiciency under the multiple requirements o:E the printing pro-
cedure. The support must have a surace structure which is
porous so that the surEace can retain su:Eficient water to have
arl adequat~ repelling ef:Eect with respect to the printing i.nks
used Eox printing
~ luminu~ oxide layers prepare~d by anOdic~xidation O:e
aluminum sheets or :Eoils are extraordinarily abrasion-resistant
and such anodized shee-ts have been Eound very use:Eul in the
production o~ long running printing p:lates. However, such plates
su:EEer Erom disadvantages caused by too great a penetration of
the radiation-sensiti.ve composition into the pores of the supportl.
In the past such disadvanta~es have been obviated by, for
example, treating the anodized support with a.n a~ueous solution
of sodium silicate, ammonium or alkali bichromate! iron ammonium !
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oxalate or a dyestu~f which can react chemi^all, with the Al
oxide surfaces, prior to coating with the radiation-sensitive
composition.
However, these processes also suffer from disadvantages.
Il Thus, treatment with alkali silicate entails the requirement of -
,, thorough rinsing with water when the support obtained is to be
I provided with a storable light-sensitive layer adapted to be
stored in the thus sensitized sta~e over a long period without
deterioration. But even after thorough rinsing with water,or
even neutralization with dilute acids, the silicate layer, or
perhaps alkali residue remaining from the silicate solution,
effect a certain deterioration. When the mentioned aqueous
chromate solutions are used a barely hydrophilic intermediate
layer is obtained, the chromate content of which, presumably
because o~ its oxidizing e~fect, often adversely affects the
light-sensitive layer to be applied in that the layer is dis-
colored, which impairs the light-permeability thereof so that
I the light-sensitivity of the layer is reduced.
Furthermore, the use of chromium containing compositions is
now considered environmentally undesireable. Similar consider-
ations, except for the environmental, apply to treatment with
an iron ammonium oxalate solution, the iron content of which may
cause a dark discoloration. ~Vhen using aqueous solutions of
dyestuf-fs which chemically react with the aluminum oxide surf~ce
the hydrophilic properties of the aluminum layer are reducea
partiallv with the result that a printing plate material produced
with a support pretreated in this manner tends to scum during
printin~ more than a printing plate whose surface has not
been so pretreated. Furthermore, the aluminum oxide surfaces
I chemically altered by means of dyestuffs cannot be easily
corrected.
The improved support according to the present invention has
been found to overcome the above disadvantages.
In accordance with the instant invention there is
provided a method for preparinq a lithoqraphic printing plate
comprisinq the steps of
I. exposin~ a radiation-sensitive element comprising
an anodized support material having coated thereuPon a
radiation-sensitive composition to radiation through a
mask; and
II. developing the exposed element to remove the areas
of qreater solubility to produce the desired plate,
wherein the improvement comprises treatinq said
anodized support, either during or after anodization,
with an aqueous solution of an alkali metal salt of a
condensed arylsulfonic acid having an acid pH prior to
coatinq with said composition, said arylsulfonic acid
having two or more arylsul~onic acid~ nuclei joined by
alkylene groups.
It is therefore an ohject of an instant invèntion to
provide an improved support material for use in the preparation
of radiation-sensitive elements which prevents deleterious
penetration of the radiation-sensitive composition into the
support material without reducinq the hydrophilicity thereof.
This and other ohjects of the present invention will be
in part discussed and in part apparent upon a consideration of
the detailed description of the preferred embodiment.
As indicated above the present invention provides an
improved support material, for use in the radiation-sensi~ive
elements which are useful in the preparation o~ long running
lithographic printing plates, which are free of background
contamination said improved support material comprisin~ any~ f
the known anodized support materials which has been treated with
an aquelous bath comprising an alkali metal salt of a condensed
aryl sufonic acid having an acidic pH durin~ or subsequent to
the anodization step.
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The arylsulfonic acid salts useful according to the
instant invention include the naphthalene sulfonates in which
two or more naphthalene nuclei are joined by alkylene groups.
The prototype of this class is dinaphthylmethane-disulfonic
acid, the disulfonic acid having a formula as follows:
- 4a -
r
3 ,~11 ~ ~1 c~
~ ~ ~ ~ ~.L
~a~2~
¦ Products of this class are of indefinite composition.
Ij They may be manufactured by heating naphthalene, formaldehyde,
I and sulfuric acid together, or by treating naphthalene sulfonic
! acids with formaldehyde. Thus three or more naphthalene nuclei
may be joined toge-ther by alkylene groups to yield a condensation
I polymer. Lower alkylated naphthalenes may also be used in the
reaction. An example is monoisopropylnaphthalene. In place of
naphthalene, other aromatic hydrocarbons may be employed such
as benzene, diphenyl, anthracene, phenanthrene, fluorene, etc.,
or homologues or derivatives thereof. The salts of the foregoing'
acids, such as the sodium salts possess similar properties. The
production of dispersing agents of this type is described in
detail in the literature and in prior art patents including U.S.
1, Patent No. 2,802,845 and representative compounds are available
¦ in the trade under the trademarks Tamol, Leukanol and Daxad.
¦ Particularly useful for the instant invention are the sodium
salts of condensed naphthalene sulfonic acids known as Tamol SN
! and Tamol N Micro which are available commercially from ~hm and
IIaas.
The support material may be any o~ those known in the art,
including aluminum and its alloys. A preferred support material
is selected from aluminum and its lithographically suitable
alloys
I If desired, the support material may be subjected to one or
more treatments prior to, or a~ter, said salt treatment, selected
¦ from the group comprising graining e.g., chemical, mechanical,
~' or electrochemical, degreasing, desmutting, and the like.
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The anodization may be e~ected in any manner known in the ¦
art including immersion oL the substra-te in an aqueous bath com-
prising H2S0~, ~13PO~and the like,and mixtures thereof and
subjectin~ it to a current density in an AC or DC field.
According to one em~odiment of the invention an anodiæed
support material is prepared by subjecting a metal sheet or web
which may have been pretreated as indicated above, to a current
density of about l to about 4 A/dm2 at about lO -to about 40 volts
D~, in an aqueous acid bath o-F about 15 to about 30% wt. concen-
tration for about 0.5 to about 5 minutes. The thus anodized
support is then treated wi-th an aqeuous solution of the alkali
salt of the condensed aryl sulfonic acid whose conce~tration is
abou-t 5 to about lOh wt. The pH of the sul~onic acid bat~ is
adjusted to abou-t l.5 by addi-tion of H2S0~.
Preferably the anodization is effected in a bath of about
20% wt. aqueous H2S04 at about 2.6 A/dm and about 20 volts DC
for about l minute while the sulfonic acid comprises about 7.5%
wt. aqueous solution. The salt solution may be applied to the
I anodized support material by any means inclucling dipping,
sponging and squeegeeing.
In an alternative modi~ication of the instant invention, the
anodization and sealing processes are e~`fected approximately
simultaneously by inclusion of the arylsul-fonic acid salt in the
anodization bath. According to this modification the bath
comprises ~rom about lS to about 30% wt. H2S0~ and about 0.5
to about lO70 wt. of the sulfonic acid salt. Preferably the bath
'~ comprises about 2070 wt. }I2S04 and about 1% wt. sulfonic acid
salt.
According to the instant invention there is also provided
an improved radiation-sensitive element which comprises any o~ ¦
the improved supports upon which has been coated any radiation- I
sensitive composition as known in the art, e.g., pos:itive-acting ¦
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compositions, such as are described, e.g., in U.S. Patents
4,189,320 (issued February 19, 1930) and 3,785,825 (issued
January 1~, 1974) and negative--acting compositions, such as are
described, e.g., in U.S. Pa-tent 3,382,069 (issued May 7, 1~68).
Said coatings are applied to the support material by any method
known to the art including which coating, meniscus coating and
the li~e.
The instant invention also provides a method for the
preparation of improved lithographic printing plates which com-
prises -the steps of imagewise exposing any o~ the above elements,
in accordance with the invention, to radia-tion through a mask,
development of said imagewise exposed element to remove the
less soluble areas o-f the coating and, iE desired, post-treating
the developed element to produce a desirable lithographic print-
ing plate.
The methods -Eor exposure, development and post-treatment oE
the elements may be any of those known in the art including,
e.g., the post-curing procedure described in U.S. Patent No.
4,233,390 issued November 11, 1980.
The Eollowing examples illustr~v.te and are not meant to
limit the invention as claimed.
le 1
A sheet ~25 cm x 25 cm) of Al alloy AA 1050 was
~rained USillg a wet slurry o:E pumice and then anodized in an
aqueous bath comprising 20~o wt. ~I2S0~ at 3.3 A/d~2 Eor a period
o~ 1 minute.
The thus anodiæed sheet was then dipped, at room temperature,
into a bath comprlsing 50 to 100 g/l of TAMOI,T~I SN, which was
ad;)usted to a p~I oE 1.5 with TI2S0~, Eor 30 seconds.
After the above treatment the sheet was rinsed and dried ancl
coated with a radiation-sensitive composition comprising a 1 to 1
mixture of a cresol -Eormaldehyde resin wi.th the condensation
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product of naphthoquinone-1,2-(diazide 2)-5 sulfonyl chloride
with a pyrogallol acetone resin, to yield a radiation-sensitive
element which after image wise exposure, development and post-
treatment by means well known in -the art yielded a lithographic
printing plate, having a clean non-image area, which produced
65,000 acceptable impressions. -~
Example 2
The method of Example 1 vas repeated e~cept that the
anodizing bath comprised 20% wt. H2SO4 and 1% wt. TAMOL SN, and
the dipping step was deleted. Similar results were obtained.
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