DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS Any of the supports conventionally used in lithography are suitable for the present invention.
Metal supports and particularly steel, aluminum, brass, stainless steel and the like, in the form of foils are particularly suitable for the lithographic plates of the present invention.
Furthermore, these supports may be treated mechanically, i.
e.
with abrasives, or chemically, i.
e.
by electrochemical deposit, to promote the adherence of the anchoring layer.
For example, an electrochemical deposit of chromium having a thickness of at least 0.
1 microns, preferably greater than 0.
5 microns, can be used.
Other suitable treatments for modifying this support to increase the adhesion between the support and the anchoring layer are described, for example, in the Lewis, et al patent, U.
S.
Pat.
No.
3,820,993, the disclosure of which is incorporated herein by reference.
The anchoring layer is formed from a hydrophobic colloid ester and has pronounced oleophilic properties and is further characterized by being capable of being converted to a hydrophilic colloid by treatment with solutions of alkali substances.
Examples of suitable colloid esters which can be used as the anchoring layer in the present invention, include, for example, cellulose esters of organic acids such as, cellulose acetate, cellulose propionate, cellulose butyrate, etc.
; acetopropionates, acetobutyrates, as well as mixtures of these colloid esters.
The hydrophobic colloid ester is applied to the support, after suitable degreasing and any other pre-treatment, as a solution in a solvent of the methylglycol type, (ethyleneglycol monomethyl ether) methylglycol acetate, etc.
, methylethylketone, methylenechloride and the like.
The hydrophobic colloid ester is present in the solution in an amount sufficient to provide a dry layer having a thickness greater than about 200 A, preferably greater than about 500 A and most preferably from about 0.
1 to about 4 microns.
In place of the above mentioned hydrophobic (oleophilic) colloid esters, it is also possible to use cellulose nitrate with a sufficiently strong ester hydrolysis solution
|
Metal Working 
