Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Hoe 77/K 037 (K 2455a)
The present invent1on relates ~o a process for the prepara-
tion of planographlc printing forms wherein an aluminum support
covered by a recording layer comprising diazonium compounds is
imagewise irradiated with a laser beam, whereby oleophilic or in-
soluble image areas are produced in the recording layer.
U. S. Patent NQ. 3,664,737, discloses a printing plate
comprislng a UV-light sensitive lay r, preferably a diazo layer,
on an aluminum support and which is irradlated with a laser
beam .
German Patent No. 2,:~48,325, and German Offenlegungs-
schrift No . 2, 543, 820, disclose processes for the manufacture of
prlnting plates by irradiating non-light-sensitive recording layers
with laser beams, the irradiated areas of the recordlng layer being
made permanently oleophilic or, if an already oleophilic layer is
used, insoluble in a suitable developer liquid. Anodized alumi-
num is mentioned, among others, as a suitable support.
It has been suggested in earlier German Patent Application
No. P 2,725,308, to use laser beams for lmaglng a presensitized
printing plate which comprises a support of optionally anodized
aluminum and a light-sensitive layer containing a negative-
working diazonium compound.
The basic patent relates to a process for the preparation
of planographic printing forms wherein a recording matsrial som-
` prising a support of anodlcally oxldized aluminum and a recording
.. ; :
layer on the oxide layer is imagewise Itradiated with a laser beam,
thus rendering the irradiated portions of the recording layer
H oe 7 7/K 0 3 7 (K 2 4 5 5 a )
oleophl lic and/or insoluble, and the non-irradiated por~lons of the
recording layer are then removed, where necessary, by washing
with a developer l~quid . In the proces s, a support is u sed which
has an oxide layer weighing at least 3 grams per square meter.
It is the ob~ect of the pres~nt inventlon to Improve the
sensitivity towards laser beams of a llght-sensitive recording
material according to the basic patent, and/or increase the length
of the printlng runs of prlnting forms prepared from the recording
material .
In the process according to the present invention, a re-
cording material is llsed which comprises a negative-working,
light-hardenable dlazo cvmpound and an amine resin.
Negative-working, light-hardenable diazo compounds which
may be used in the process of the invention are, above all,
diazonium salt condensation products, also called diazo resins.
Suitable poLycondansation products are obtained by condensation
of aromatic diazonium salts, preferably of possibly substituted
diphenylamine-4-diazonium salts, wlth active carbonyl compounds,
preferably formaldehyde, in a strongly acid medium.
Products of this type are disclosed, for example in German
Patents No. 1, 214, 086 and No . 1,292, 001 . Particularly preferred
are mixed condensation products containing diazonium salt units
and units of non-light-sensitlve second components capable of
condensation, such as aromatic amines, phenols, thiophenols,
phenol ethers, aromatic thioethers, aromatic hydrocarbons, aro-
matic heterocycllc compounds, and organic acid amides.
3~ Hoe 77/K 037 (K 2455a)
Condensation products of this type are disclosed in U. S.
Patents Mos. 3,849,392 and 3,867,147. Negative-working diazo
compounds of the p-benzoquinone dlazide type and p-lmino qui-
none diazides, such as those described, for example, in German
Patent No. 1,104,824, are also suitable.
Among the amine resins, amine-formaldehyde res1ns are
preferred which are obtained by condensation of formaldehyde with
urea, urethanes (carbamide acid esters), anillne, or melamine.
Such condensation products are known and are obtainable in many
modifications as commercial products. Suitable compounds are
described, e.g., in the "Kuns~stoff-Handbuch" tPlastics Manual),
Vol. X, published by Vieweg and Becker, Carl Hauser Verlag~
Munich, 1968.
For the preparation of the laser~sensitlve recording layer,
the amine resin ~ls added to the solution which contains ~he diazo
compound selected and is to be used for coating the anodized
aluminum support. The quantlty of resin added may vary within
wlde llmits. As a rule, it ranges from 0.1 to 10 parts by welght
of resin per part by welght of the diazo compound used. Particu-
larly favorable results are obtainecl with a resin addition in the
range from about 0. 6 to 6 . 0 parts by weight per part by weight of
the diazo compound.
The supports of the recording materials used for the pres-
ent process are prepared in known manner. Prior to anodic oxi-
; dation, the aluminum preferably is roughened by rnechanical,
chemical or electrochemical rneans. A combination of an electro-
Iytic roughening with an anodic oxidation has been iound to be
Hoe 77~K 037 (K 2455a)
particularly advantageous for a continuous process. Roughening
is performed in a bath containing a dilute aqueous mineral acid,
e . g . hydrochloric acid or nitric acid, with the simultaneous
applicatlon of direct or alternatir,g current,
Anodization also takes place in an aqueous acld bath, for
axample in a suliuric acid or phosphoric acld bath, preferably
with s1multaneous application of dlrect current. Current densities
and anodizing times are so adjusted that oxide layers of a thick-
ness in the above stated range are obtained . The thicknes s of
the layer should correspond to at least 2 grams per square me$er,
The upper l1mit for the layer thickness is not critical, but nor-
mally no further improvem~nts are obtained w1th layers welghing
more than 12 grams per square meter. If the layers are substan-
tiallythicker, i.e. above about 3û grams per square meter, there
is the additional risk that cracks will form in the oxide layer
when it is bent, Normally oxide layers welghing between about
3 and 10 grams per square meter are preferred.
After irradiation -with laser beams, the UV light-sensitive
diazo layers according to the invention are developed with aque-
ous alkaline or acid solutions, or even with water. Lacquer
emulsions or lacquer~ of the type used for~ planographic printing
plates also may be used. These lacquer amulsions and lacquers
may be applied, in one operation, for development and lacquerlng,
- or after development w1th aqueous solutions.
:~'
~3S~6 Hoe 77/K 037 (K 2455a~
Appropriately powered relatively short-wave lasers, for
example argon lasers and krypton lasers may be used for the
purposes of the present invention, and they may have radiation
outputs from about 0.5 to about 2.5 watts in the UV range, or of
about 1 to 25 watts in the visible range, dependlrlg on the type
of mirror used . Dyestuffs, e . g . rhodamines, triphenyl methane
dyest such as crystal violet, astrazon orange, eosin, or methyl-
ene blue, which strongly absorb wlthin ~he emitted ranges and
have a sensltizing effect, may be added to the layer according
to the lnvention .
The laser beam may be controlled by means of a given,
programmed line and screen movement~ Processes and devices
for controlling laser beams by means of computers and bundling,
modulation, or deflec~ion of laser beams are no part of the pres-
ent invention; they are described in various publications, for
example German Offenlegungsschriften Nos. 2,318,133 (pages 3
et seq.), 2,344,233 ~pages 8 et seq.), and in U. S. Patents
Nos. 3,751,587, 3,745,586, 3,~47,117, 3,475,760,
3,506,779, and 3,664,737.
Preferably, the layers are imagewlse irradiated wlth an
argon laser of between 1 and 10 watts . Speeds of up to and
even exceeding 110 m per second can be achieved, depending
upon the sensitlvity and absorption capacity of the layer used.
By focussing the laser beam with a lens, hardened spots of
less than 50y,m diameter are produced on the layer.
By the process according to the inventlon, a very durable
oleophilizatlon of the surface ls achLe~ed, so that long runs can
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5~, Hoe 77/K 037 (K 2455a)
be printed. Further~ the recording rnaterials used are distinguish-
ed in that their sensitivity ts)wards laser beams is especially
high .
The following examples lllustrate preferred embodiments of
the lnvention. Unless otherwise stated, all percentages are by
weight. 1 part by weight is 1 gram, if 1 mllliliter is one part
by volume.
~2~
A roll of bright rolled aluminum is electrolytically rough-
ened in a continuous process, and is then anodically oxidized
for 75 seconds, at 40C with a 9A/dm direct current in an aque-
ous bath containing 150 grams of sulfuric acid per liter. An
anodic oxide layer weighlng 5 grams per square meter is thus
produced. The layer is then treated for 30 seconds, at 70 C,
wlth a 0 . 25 per cent aqueous solution of polyvinyl phosphonlc
acld and dried. The plate is then sensltized wlth a solul:lon con-
taining 0 . 4 per cent of a diaxo polycondensate (obtained by con-
densing 1 mole of 3-methoxy-diphenylamine-4-diazonium sulfate
with 1 mole of 4 ,4'-bis methoxymethyl-diphenyl ether in 85 per
cent phosphorlc acld at 40 C and separating the reaction product
in the form of the methane sulfonate), 0. 72 per cent of a highly
reactive, unplasticized urea resin with a dynamic viscosity ln a
60 per cent solution in isobutanol of about 2500 mPas (cP) at 20
C and an acld number below 2 (resin I), and 0.4% of Rhodamine
6 GDN (Color Index No. 45,16û~ dis~olved in ethylene glycol
monoethyl ether.
.
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3~ H oe 7 7/K 03 7 (K 2 4 5 5 a )
The plate is irradlated with an argon laser which emlts in
the W range, malnly at wave lengths 363 and 351 nm, the radia-
tion output belng 0 . 8 watt and the recording speed being 100 m/
sec. The areas of the layer not struck by the laser beam are de- :~
cc-ated with an aqueous solu~ion containing 0 . 65 per cent of sod-
ium metasilicate 9 H2O and 3 . a per cent of benzyl alcohol .
The irradiated, hardened areas are oleophlllc and accept greasy
lnk . More than 85, 000 copies of good quality can be prlnted in
an offset printing machine.
Simllar results are obtained if the above-mentioned urea ~ .
resin is replaced by the same quantity of one of the following
unplastici~ed urea resins: ~ .
-
Resin II: acid number below 3; dynamic viscosity in a
65 per cent solution In butanol/xylene, at
~ 2ûC, of approximately 6,000 mPas (cP).
: ~ Resin III: acid number below 3; dynamic viscosity in a
60 per cent solutlon in isobutanol, at 2 0 C, r
of approxlmately 650 mPas ~cP~.
Example 2
An aluminum plate with an anodic oxide layer welghing 2
grams per square meter, which has been pretreated with poly-
vinyl phosphonlc acid, ls coated with a solution containlng 1 . 0
per cent of the dlazo polycondensate used in Example 1, but
;~; lsolated in the form of the mesltylene sulfonate, 1. 8 per cent
. ~ of Resin II, and 0.4 per cent of crystal violet d1ssolved in
ethylene glycol monomethyl ether.
,~
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3~i~6 Hoe 77/K 037 (K 2455a)
The plate is irradiated with an argon laser emittlng ln the
vlsible range, mainly at wave lengths of 488 and 514 nm, and
having a radlation output of 5 watts and a recording speed of 50
m per second. The areas of the layer not struclc by the laser
beam are decoated with an aqueous solution containing 6 per cent
of magnesium sulfate 7 H2O, 20 per cent of n-propanol, and 0 . 7
per cent of a non-ionogenic wettlng agent (alkylphenol-polyglycol
ether). The irradiated areas accept greasy ink in an offset print-
ing machine and allow long printing runs.
Example 3
An aluminum plate having an anodic oxide layer wei~hing
10 grams per square meter is coated with a solution of the fol-
lowing composition:
2 p.b.w. of 1-(4'~methyl benzene-sulfonyl-imino)-
2-(2 ", 5 "-dimethyl~phenylamino-sulfonyl3-benzo-
quinone-(1, 4) diazide-(4) and
i~ 0.7 p.b.w. of an unplasticized, highly reactive
melamine resin with a dynamic viscosity in a
50% solution in ethanol at 20 C of about 450
2Q mPas (cP) and an acid numher below 1 Iresln
IV) in
80 p.b.w. of ethyleneglycol monomethyl ether, and
~` 2û p.b.w. of butyl acetate.
The material ls irradlated with a krypton-ion laser emitting
in the UV range, mainly at wave lengths of 406 and 423 nm,
which has a radlation output of 0.9 watt and a recording speed
of 80 m per second. Then the plate is decoated with a solution
3~ , Hoe 77/K 037 (K 2455a)
of 1 . 3 per cent of anhydrous sodium sllicate and 1 . 2 per cent of
anhydrous trlsodium phosphate in water. Long prlntlng runs can
be obtained.
Example 4
An aluminum plate wlth an anodlc oxide layer weighing S
grams per square meter is coated with a solution of 0.4 part by
weight of a crude condensation product of paraformaldehyde and
diphenylamine-4-diazonium chloride (prepared ln 85% phosphoric
acid), 1 part by weight of a liquid urethane resin obtained from
butylurethane and formaldehyde and having a density of 1.1 at
20 C ancl a dynamic viscosity~ at 20 C of from 6 to 20 mPas
tcP), and 0.2 gram of Astrazon Orange ~C.I. 48,040) dissolved
1n a mixture of 50 parts ~y weight of tetrahydrofuran, 40 parts ~ ;~
by weight of ethyleneglycol monomethyl ether, and 10 parts by
weight of butyl acetate.
The plate is irradiated with an argon laser emitting in the
visible range,~ which has a radiation output of 5 watts and a re-
~; cording speed of 60 m per second, and ls then decoated wlth
water .
~.
It will be obvious to those skilled in the art that many
modifications may be made within the scope of the present lnven-
tion without departing from the spirlt thereof, and the inventlon
- includes all such modiflcations.
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