US2215128A - Material and process for obtaining metal printing plates with silver halide emulsions - Google Patents

Description

Sept 17, 1940- c. E. MEULENDYKE 2,215,128

MATERIAL AND PROCESS FOR OBTAINING METAL PRINTING'` PLATES WITH SILVER HALIDE EMULSIONS Filed June 7, 1939 U/ze xpos en? am /s/W Wasea/ 1 auf.

Patented Sept. 17, 1940 PATENT OFFICE 2,215,128 MATERIAL AND y PROCESS FR OBTAIN-V ING METAL PRINTING PLATES WITH SILVER HALIDE EMULSIONS Charles Edmund Meulendyke, Rochester, N. Y. Application June 7, 1939, serial No. '277,843

6 Claims.

This invention relates to the preparation of metallic sheets supportingcolloid layers containing a sensitive silver salt and to the subsequent processing of such sheets into relief, planographic and intaglio plates for monochrome and polychrome printing.

Reference is made to the previous state of the art in which an inert metallic layer supported on a metallic base serves to prevent contaminao tion of a silver halide emulsion layer directly ycoated on such inert layer. After processing the emusion layer into a relief such colloid layer serves as a resist for the etching of the metal. There are, however, certain limitati-ons and diffi- 15 culties noted below in connection with this method. Reference is also made to the previous state of the art in which a lacquer or varnish layer is employed in lieu of the inert metallic layer. Such lacquer layer serves to isolate the emulsion layer from the contamination of a zinc r copper base, and to form a lacquer resist for the etching of the metal. The present invention proposes a material whose essentially novel and useful feature is its inclusion of both a metallic and a lacquer interlayer in place of the single metallic or single lacquer layer hitherto employed. Such material constitutes an entity in itself creating new advantages and improve'- ments and functioningy novelly with respect to 30 any previous use of the single layers.

The material consisting of a 'metallic base plated with an inert metallic layer directly supporting a silver halide emulsion has disadvantages in that there is little choice of metal in 35 forming the inert 4metallic interlayer and in that it is difficult to plate a perfect layer of metal non-contaminating to the emulsion layer. In fact, while zinc has been generally recognized as a 'most useful metal base for making line cuts, such an accomplishment asa nickel-plated zinc which will not contaminate a silver halide emulsion coated directly thereon, has not'been proven as practically attainable. Then again it is difficult to process a resist from a silver halide emulsion layer which will vwithstand the etching medium. The use of mineral acids is out. of the question and even a comparatively harmless etching medium suchv as ferric chloride tends todestroy such resist before satisfactory etching 50 depth has been reached. In fact ferrie chloride in high concentration seems to be the only etchant whichcan be usedwith a silver halide `emulsion resist. On the other hand there are certain advantages in the etching of a metal plate con- 55 sisting of a basic metal` sheet plated with a metallic` layer differently composed with respect to such base. An example is a copper sheet electroplated with a nickel layer. Now in the etching of a copper or a zinc plate as ordinarilyv carried out to form a half-tone or line cut, as depth of etching is attained there is also a strong etching action on the sides of the depressions. This requires a skilled etcher who may etch in stages 'or may powder the sides of the depressions in order to form the correct sizes of dots or widths of lines. With suitable choice of electroplated metal and suitable choice of etchant I have found that the etching operation can be made simple, in part -due to the' fact that the metal caps formed after cutting through the metallic interlayer tendtopreserve the sizes of the original half-tone dots while permitting deep etching linto the metal base. This condition can be realized by use of a single etching solution which dissolves the metal of the base somewhat faster than the metal of the interlayer. On the otherl hand, the metal of the interlayer can be purposely undercut and later such undercutting corrected in a second etching solution which dissolves the metalof theinterlayer faster than the base metal. For example, in the etching of nickel-plated copper supporting suitable localresists, and with judicious use of ferric chloride and cupric chloride as etching media as described incopending patent application (U. S. Serial Number 275,514, filed May 24, 1939) the sizes of the dots, the slope of the sides of the dots and depth of etching can be simply controlled without the need of a skilled etcher.

This reference shows how etching control is established b; use of etchants which differentially control the rates of etching of the two metals, and how nickel and copper can be etched at equal rates or either one faster than'the other.l My use of the lacquer layer to form a secondary resist permits use of etchants which would destroy asilver halide emulsion resist. Properly speaking I do not use the metalliclayer as a, metallic resist, but rather as an etching-control layer. It is the varnish layer which functions as the resist. The metallic interlayer etches only where unprotected by such resist. The etching operation can be said to be performedunder the joint selective control of the lacquer resist and the metallic interlayer.

I believe I' amvthe rst to propose a material consisting of a 'basic metallic sheet whose surface is plated with a metallic layer suitably com- -posed to function as an etching-control layer and supporting a lacquer or varnish layer which in turn supports a colloid layer containing a sensitive silver salt. I believe I am the first to proposethe inclusion of nickel-plated copper or nickel-plated zinc in such material. I preferably use a simple form of metallic interlayer although' it can be plated as an alloy or even asv a multiple-plated layer of different metals. I believe I am the rst to propose the processing of such a material into a photomechanical printing plate. It is of course unnecessary that the plated metallic layer shall be truly inert to the silver halide emulsion, although I preferably use a metallic interlayer of such metals as silver,

nickel or chromium which per se are inert to a silver halide emulsion. Such inert metallic layer together with the lacquer layer has the added. advantage of affording a double `protection to the Aemulsion from contamination by the metal base. The metallic layer primarily furnishes etching control and a hard printing surface while the lacquer layer furnishes a hardy resist and an inert layer between the metal and the emulsion.

I have found the ellulosic lacquersdo not adhere strongly to metal, while gum lacquers tend to adhere very strongly. I have further found that gum lacquerstend to be attacked by the Solutions used to process thecolloid relief from the silver halide emulsion la'yer, while cellulosic lacquers are markedly resistant in this respect. For these reasons I suggest a mixed lacquer containing cellulosic and gum ingredients. Preferably I coat a gum lacquer such as shellac directly upon the metallic layer and then a cellulosic lacquer over this gum lacquer. However; I do not restrict myself in the choice of a lacquer or varnish and within the meaning of this invention I intend to include any suitable form such as cellulose nitrate, cellulose acetate, natural gums such as shellac, dammar anddragons blood, as well as synthetic resins, all of which can be Adissolved in appropriate organic solvents for application to the metallic surfaces. Also a suitable dye may be added to the lacquer layer to render it more visible or to prevent halation from the metallic surface. After formation of the emulsion relief the bared lacquer surfaces can be cut through to form bared metallic surfaces by brushing with a suitable organic solvent.

It will thus be seen that I have described materialsand processes with all necessary details embodying the principles and attaining the objects and advantages of the invention. Since many manners of treatment, manipulation, selection and proportion of ingredients, succession of steps and other details may be variously modied without departing from the principles involved, I do not intend any limitation to such details excepting so far as set forth in the appended claims.

For the purpose of illustrating Athe several steps which can be followed in carrying out one form of the methods herein described and at the same time disclosing the material in one of its several forms, attention is called to the accompanying drawing in which:

Figure l shows a greatly'enlarged section of a metallic base sheet I, plated with a metallic layer 2 supporting a lacquer or varnish layer 3 which in turn supports a silver halide emulsion layer 4.

Figure 2 shows the emulsion layer -as exposed under a half-tone screen and developed, exposed areas 5 being subsequently hardened. y

Figure 6 shows the completed plate with the emulsion and varnish layers removed.

What is claimed is: 1. A material for use in the art of photome- Achanical printing including al basic metallic sheet Whose surface isplated with a nickel layer suitable for effecting etching control substantially as herein described, such layer supporting a lacquer or varnish layer which in turn supports a colloid layer containing a sensitive silver salt.

2. A material for use in the art of photomechanical printing including a basic copper sheet whose surface is plated with a nickel layer suitable for effecting etching control substantially as herein described, 'such layer supporting a lacquer or varnish layer which in turn supports a colloid layer containing a sensitive silver salt.

3. In the art of photomechanical printing, the method of producing a printing plate including the steps of exposing a basic metallic sheet whose surface is plated With ametallic layer suitably composed to effect etching control substantially as herein described, such metallic layer supporting a lacquer or varnish layer which in turn supports a colloid layer containing a Sensitive silver salt, developing the silver image, rendering a colloid relief under the selective control of the silver image with formation of bared lacquer or varnish surfaces, rendering a lacquer or varnish relief under the selective control of the colloid relief with formation of bared metallic surfaces, and etching into the metallic base by a suitable agency under the joint selective control of the lacquer or varnish relief and the metallic interlayer.

4. In the art of photomechanical printing', the method of producing a printing plate including the steps of exposing a basic metallic sheet whose surface is plated with a nickel layer suitable for effecting etching control substantially as herein described, such layer supporting a lacquer or varnish layer. which in turn supports a colloid layer containing a sensitive silver salt,

developing the silver image, rendering a colloid` 'relief under the selective control of the silver image with formation of bared lacquer or varnish surfaces, rendering a' lacquer or varnish relief under the selective control of the colloid relief with formation of bared. metallic surfaces, and etching into the` metallic base by a suitable agency under the joint selective control of the lacquer or varnishrelief and the metallic interlayer.

method of producing a printing plate including the steps of exposing a basic copper sheet Whose surface is plated with a nickel layer sitable for effecting etching control substantially as herein described, .such layer supporting a lacquer or varnish layer which in turn supports a colloid layer containing a sensitive silver salt, developing thesilver' image, rendering a colloid relief 5. In the art of photomechanical printing, the

under the selective control of the'silver image with formation of bared lacquer or varnish surfaces,'rendering a lacquer or varnish relief under the selective control of the colloid relief with formation of bared metallic surfaces, and etching into the metallic base by a suitable agency under the joint selective control of the lacquer or varnish relief and the metallic interlayer.

6. A material for use in the art of photomechanical printing including a basic metallic sheet whose surface is plated with a metallic layer selected from the group consisting of silver, nickel and chromium," and suitable for effecting etching control. substantially as herein described, such.

layer supporting a. lacquer or varnish layer which in turn supports a colloid layer containing a sensitive silver salt.

CHARLES EDMUND MEULENDYKE.

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