Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a new
offset plate~ for use as a monometallic plate~ and
comprising a printing layerO
In offset printing, plates are often u~ed
which are known to be used as monometallic plates, i.
e. plate~ in which a monometallic surface, the term
monometallic being used here to cover simultaneously
the use of metals or alloys, plays the part of surface
accepting water~ Such a surface may be for example
in stainless steel, chromium, tin, nickel-tin,
aluminium, aluminium alloy or hydrophilous ~inc. Such
surface is the surface of a support which is made of
the same metal or alloy or of a different metal;
plates are known to have, for example, a coppered
steel support and a chromium surface.
A positive or negative photosensitive
printing layer is deposited on the said monometallic
surface.
The development, after insolating, consists
in removing the soluble parts of the printing layer and
in exposing the subjacent water accepting mono-
metallic surface.
It has been found, and this is precisely
the object of the present invention, that in offset
plates used as plates having monometallic water-
accepting surfaces, such as those described herein-
above, it is advantageous to insert between the
water-acceptinS surface and the printing surface a
film of between 0.005 and 0.5 ~ thickness of a
3 water-refusing derivative.
Such water-refusing derivative can be a
metal, a metal alloy, a varnish, a resin or a combina-
tion of these products~
Said derivative will need to be strongly
fixed by known means, to the water-accepting surface
used, and also to be easily removable, after the
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printing layer is developed~ by means of an etching
solution which will remove the totality of the
derivative without noticeably attacking either
the remaining parts of the printing layer or the
water-accepting monometallic surface on which the
derivative has been deposited.
According to the invention, it i9 possible
and even preferred to use a metal or metal alloy
accepting ink or made to accept ink after an
appropriate treatment. Amongst metals and metal
alloys suitable to be very thinly applied over a
monometallic water-accepting surface can be cited:
- copper, bronze, lead, ink-accepting zinc, zinc-
nickel, tin, iron~antimony, cadmium, manganese, ink-
accepting chromium, or various alloys of these metals,the said metals or metal alloy~ accepting ink nat-
urally or being made to accept ink.
It may often be advantageous to arrange,
within the scope of the invention, for the film
of water-refusing derivative deposited between the
water-accepting surface and the printing layer,
to be colored and to have a special structure. ~or
example, when the said film is constituted by a
deposit of copper, tin or zinc, etc... it is
advantageous, before depositing the printing layer,
to attack the metallic film with commercially known
substances in order to produce porous surfaces which
may be blackened or colored as required~
The way to produce the film should be
3 selected as a function, fir~t of the metal or alloy
to be deposited, and second, of the water-accepting
monometallic surface to be covered; amongst the
known methods of depositing such a film, the main
ones are: chemical displacement of a metal contained
in a bath, or electrolysi~. When the said film is to
be made of a material such as varnish or a resin,
,:
~:13Z840
known techniques will then be used.
The non-restrictive examples given herein-
after illustrate the invention.
EXA~IPLE 1
S An aluminium plate of 25/100 thickness is
used, whose face has been scoured and scrubbed but
not anodized. On the surface of the said plate is
deposited a film of zinc of 0002 p thickness using
the "zincate process" which consists in dipping the
aluminium plate for about 30 seconds in a bath
especially containing zinc salts~ Such a process
is for example described in the CANNING HANDBOOK
ON ELECTROPLATING (22nd Edition) Canning Lt. Page
350.
On the zinc film produced this way, is
deposited a photosensitive layer of about 1 to 2 ~,
such as for example a negative photosensitive layer.
After insolation, the said photosensitive
layer is treated with a developing solution which
dissolves the non-hardened parts of the layer; then
the whole lot is treated with a nitric acid solution
at 15% which removes the zinc film in those places
where the zinc surface is no longer covered with
a printing layer. After washing, a plate is obtained
which can be used right away and in which the aluminium
surface plays the part of water-accepting surface.
EXAMPLE 2
A scrubbed stainless steel plate is used.
Said plate i~ soaked in an acid copper plating bath
by electrolysis, and the said electrolysis is conducted
until a copper deposit of about 0.2 ~ is obtained.
On the said copper surface is deposited a negative
photosensitive layer of about 1.5 ~ thickness.
After insolation, the photosensitive layer
is treated with a developins solution and then those
il3~8~0
parts of -the copper film, which have been exposed
with a nitric acid solution (copper etching) so as
to expose the corresponding subjacent parts of
stainless steel, are removed.
EXAMPLE 3
After scouring down an aluminium plate
- (offset quality) produced by the company CEGEDUR,
its surface is scrubbed with water and a fine
pumice, and then rinsed. The plate is thereafter
treated first in a bath containing phosphoric acid
so as to oxide its surface anodically~ After rinsing,
the plate is immersed in a copper plating bath
containing pyrophosphate and composed as follows:
Cu2P207 71 g/l
K4P207 302 g/l
K N03 11O5g/1
NH40H 5 ml/l
the pH of the bath being 8.5, the voltage density
lA/dm2 and the temperature 55C. The plate is
removed from the bath when a layer of o.8 ~ of copper
has deposited.
After rinsing and drying, the surface
of the copper is coated with a printing photosensitive
layer known of every one skilled in the art.
EXAMPLE 4
After scouring and scrubbing an aluminium
plate of 25/100 thickness produced by the company
CEGEDUR (offset quality), a solution containing 1000
cc of isopropyl alcohol (99%), 31 g of Cu2C12
(copper chloride) and 32 cc of llcl (37. 3805), is
spread over the completely dry surface of the plate.
The aluminium reddens thereb~ indicating the
formation of a copper layer. When the coloring is
uniform, the excess solution is removed with a
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seraper, and the isopropyl alcohol is poured on
and quiekly removed with eellulose wool for drying
the surfaee. Said surface is then eoated with a
photosensitive layer as indieated hereinabove.
After insolation, the non-hardened portions are
removed with a developed solution and then with a
special etehing solution to destroy the copper on
aluminium (Polyehrome bi-metal etehing) the copper
may be removed in less than 30 seconds in the
developed areasO After rinsing and gumming the plate
is ready to be used in a machineO
EXAMPLE 5
A stainless steel plate is used which is
covered, as in example 2, with copper, the thickness
f the copper deposit being 0 7~u
After rinsing, the said plate is soaked
in a bath of a product sold by the Company IMASA,
under the name Ebonol C~ for blackening copper
~ surfaces.
The copper becomes black, dull and porous
and its thickness is brought back to about Ool ~o
The plate is then coated with a positive
and photosensitive printing layer~ of 1. 8 ~ thiclmess
after insolation and developingO
The black copper is destroyed with an
etching solution as in Example 2.
The printing parts are very dark and
contrast strongly with the water-accepting surface,
this facilitating greatly the control.
EXAMPLE 6
... ...
A USINOR steel plate is used and coated
with a 3 ~ layer of tin nickel (65-35), then with
a oOo8 ~ layer of co~er or tin and with a o.o8 p
~ nl~c m~k)
layer of an ALVONOL~resin (formophenolic resin
commercialized by the company l10ECHST).
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Aft~r drying, the coated plate i~ baked at
220 for a ~ew second~ to harden the ~aid resin.
After which the plate surface is coated witll a 1,8
photosensitive printinS layer.
After insolation and developing, the plate
is attacked with a solution known and used in off~et
techniques for etching copper or tin; the ~aid
qolution is sufficient to remove first the thin layer
of ALVONOL resin, and second~ the film of copper or
tin. The water-accepting surface i~ thus exposed~
The pIates according to the invention have
very interesting qualities which are linked to the
two following phenomena:
- on the one hand, the printing layer shows very good
adherence to the surface of the film of ink-
accepting metal alloy or resin produced this way,
- and on the other hand, the water-accepting layer
exposed at the end of the process i~ always
found to be clean, iOeO not accepting ink~
