FR2460210A2 - Offset printing plate with intermediate non-hydrophilic layer - between metal surface and printing layer - Google Patents

Abstract

A monometal offset printing plate has an intermediate 0.005-0.5 mu thick layer of a non-hydrophilic material (I) between the printing layer and the hydrophilic surface of the plate. (I) is pref. a metal or a metal alloy having affinity for ink or treated to have such affinity. Improved bonding is achieved between the printing layer and the metal and the hydrophilic zones i.e. the non printing zones are clean i.e. they are ink-repellent.

Description

 The present application relates to an improved process for preparing offset plates and the. Qbtenues plates.

 Dan. Patent application no. 78 (34 955 of December 12, 1978, new offset plates have been described using plates having an aquaphile monometallic surface in which, between the aquaphile monometallic surface and the printing layer, a veil of a metal is inserted. of an encrophilic alloy or which may become so. This encrophilic metal or alloy must have the following two properties: on the one hand, it can be fixed firmly on the aquaphile monometallic surface and on the other hand it can be easily removed after development of the printing layer. .

It has been indicated that the thickness of this veil of metal or of encrophilic alloy is between 0.1 and 0.5 microns.

However, it has been observed that it is possible, within the framework of this invention, to use sails of significantly smaller thicknesses and that excellent results could be obtained by using sails of thickness between 0.005 and 0.5 microns.

Such a result is moreover actually obtained if the invention is implemented as described in patent application No. 78/34 955; in fact if example 1 of said application is used, the thickness of the zinc veil, deposited by displacement, is not 0.2 micron as indicated in said example but 0.02 micron
The present application therefore relates to the use between the aquaphile surface and the printing layer of a veil of a metal or alloy which is encrophilic or which may become so with a thickness of between 0.005 and 0.1 micron
It has also been confirmed - on the one hand that the aquaphile surfaces which can be coated
of a veil are very diverse; we can especially use as
aquaphile surface of anodized aluminum, - on the other hand than the metals and alloys mentioned in the application
No. 78/34 955, which can be used to form the sails with an encrophilic surface, are not thus limiting, for example, as
you might expect, you can use iron, antimony,
cadmium, manganese and encrophilic chromium or various alloys
containing said metals; these metals and alloys can be deposited
on the hydrophilic surface by the "displacement" technique
chemical ", and it is sometimes desirable to carry out a
good adhesion between the hydrophilic surface and the layer of
metal of intermediate layer according to the technique
known.

- finally that the metal or encrophilic alloy veil used
according to the invention of application no. 78/34 955 and according to the present
demand, greatly improving the bonding of the layer
printer, made significant progress in
certain printing techniques in particular in the technique
"wipe-on"; the use of a veil of metal or alloy encro
phile on an aquaphile metal surface allows in particular, in
the framework of the "wipe-on" technique the use of solutions
fluids containing not only diazo - as known
but also resins - also known - which make
the layer obtained more solid and allow to increase the
number of prints achievable.

 The nonlimiting examples below illustrate the invention.

EXAMPLE 1
After degreasing and pickling an aluminum plate (offset quality) from the St. CGEDUR, we brush its surface with water and fine sand and then rinse. The plate is then first treated in a bath based on phosphoric acid so as to anodically oxidize its surface. After rinsing the plate is immersed in a pyrophosphate copper-plating bath having the following composition
Cu2P207 71 g / l
K4P207 302 g / l
K N03 11.5 g / l
NH40H 5 ml / l
The pH of the bath being 7, the current density of A / dm2 and the temperature of 550C. The plate is removed from the bath when a 0.08 micron layer of copper has settled.

After rinsing and drying, the copper surface is covered with a photosensitive printer layer known to those skilled in the art.

EXAMPLE 2
After having degreased and pickled an aluminum plate 25/100 thick from St. CEGEDUR (offset quality), a solution formed by lOOOcc of isopropyl alcohol (99%) is spread over the completely dry surface of the plate. per 31 grams of Cu2C12 (copper chloride) and 32 cc of Hcl (37. 38.5).

 The aluminum turns red indicating the formation of a layer of copper. When the color is uniform, remove the excess solution with a squeegee, then pour in isopropyl alcohol which is quickly removed with cellulose wadding to dry the surface. Then it is coated with a photosensitive layer as indicated above.

After exposure, the uncured parts are removed with a developing solution and then with a special bite solution to destroy the copper on aluminum (Polychrome bi-metal bite) copper can be removed in less than 30 "in the developed areas. After rinsing and scrub the plate is ready to go in machine
EXAMPLE 3
A steel plate is used as support covered on one of its faces with a layer of 1.5 micron thick of tin-nickel alloy, this layer being coated with a layer of 0.01 micron of copper according to the present invention.

The surface obtained is brushed with a wire brush.

The printer deposits a photosensitive printer layer on the thus prepared plate using a fluid solution containing 10% by weight of KODAK PE425 resin for 90% by weight of trichlorethylene. It forms a thin photo-sensitive layer allowing direct, after exposure and development a print to
The printer, as a man skilled in the art knows how to do when he wants to lacquer an offset plate, deposits on the plate thus DréDarée a photosensitive printer layer using a fluid solution containing 10% by weight of KODAK PE425 resin for 90 % in Trichlorethylene weight. A thin, photosensitive layer is formed which allows, directly after sunshine and development, a titration of 65,000 copies; obviously it is possible according to known techniques to strengthen the Darties printers of said layer if one wants to increase the print runs

Claims (4)

 REVENDICATI, ONS l, Improved process for. offset plate preparataown for use of monometallic plate in. which between the aquaphile monometallic surface of the plate and the printing layer-a thin veil of an encrophilic metal or alloy has been inserted, characterized in that said thin veil has a thickness of between 0.005 and 0.1 microns. 2. Improved process for the preparation of an offset plate using a monometallic plate in which, between the aquaphile monometallic surface of the plate and the printing layer, a thin veil of thickness between 0.005 and 0.5 micron has been inserted. metal or ink-absorbing alloy, characterized in that the aquaphile monometallic surface is anodized aluminum. 3. Improved process for the preparation of an offset plate using a monometallic plate in which a thin veil of thickness between 0.005 and 0.5 micron of a metal has been inserted between the aquaphile monometallic surface of the plate and the printing layer or encrophilic alloy characterized in that said veil is made of iron, antimony, cadmium, manganese, encrophilic chromium or an alloy containing said metals. 4. Use of an improved process for preparing an offset plate using a monometallic plate in which, between the aquaphile monometallic surface of the plate and the printing layer, a thin veil of thickness between 0.005 and 0.5 microns has been inserted. of an ink-absorbing metal or alloy characterized in that a fluid solution containing at least one diazo and at least one resin is applied to said veil and according to the so-called "wipe-on" technique.