US2325519A - Method of producing printing forms from colloids - Google Patents

Description

Patented July 27, 1943 METHOD or reonpcmc rmn'rnvc Forms FROM coLLoms a Josef Kc h,

Siegburg, Germany; vested inthe Alien Property Custodian t No Drawing. Application August z 2, 1939, Serial No. 291,379. In Germany'August 24, 1938 Q 2 Claims. (ores- 5.4)

The present invention relates to a method of producing printing from diapositives and letterpress to be printed a screened copy in known manner is first prepared on a colloid film, which is then transferred to aprinting form carrier, and is developed and dried after rier.

According to the invention the colloid film is applied to a smooth film carrier and copied through to the positions on the screen and in white as far as the base. The film carrier has to be separated from the colloid film by means of a liquid, which dissolves the film carrier without any part of the colloid film being also dissolved. In this way a printing form is obtained whose screen cross-lines lie in one plane with the white and are of a uniform height so that the doctor blade can wipe off the ink uniformly. The gelatine film may merely show in the screen naps themselves, differences in high lights and low lights and the gelatine film then forms a relief corresponding to the matter to be printed.

The possibility of carrying out the method according to the invention is thus restricted to the possibility of copying-through as far as the film carrier the screen cross-lines uniformly in black and in white, so that after removing the film carrier by means of a liquid that does not attack the colloid film the screen cross-lines all lie in one plane. Celluloid foil, or foil of similar material, is suitable as film carrier of this kind. The actual film carrier may be applied subsequently upon a layer of paper. The dissolving of the film carrier from the colloid film may be effected by means of an etheric liquid as for example ethyl ether or acetone, or like liquids, which have a good capacity for dissolving the film carrier without on the other hand parts of the colloid film being also dissolved.

It has already been proposed to make use of intaglio printing forms of gelatine or asphalt without however the particular working conditions which form the condition for the realization of this proposal being mentioned and recognized. When ordinary carbon paper is used, it is certainly not possible to obtain printing surfaces of colloid films with uniformly high screen cross-lines, since when copying-through, the illuminated parts of the gelatine adhere so that the separation of the paper without damage to the colloid film is quite impossible. It has furthermore been proposed to apply to the surface of the roller for photo-chemical etching,

the removal of the film caritself the upper edges of forms from colloids in which,

an uncopied film that is light-sensitive or that is to be made light-sensitive later (the film be ing applied to a base film for the purpose of obtaining a smooth surface) in such manner that the base film then forms an outer protectlve film which is to be dissolved by a solvent and which does notattack the colloid film itself. Apart from the fact that this method is described only in conjunction with photo-chemical etching, itwould prove to be entirely unsuitable for producing an intaglio printing form from the colloid film since, when the film is being copied after it has been applied to the surface of the roller, development is no longer pos- 'sible because when copying from the surface the insoluble relief is at the top while the unilluminated parts and therefore the soluble parts a lie On the surface of the roller, so that when hot water is applied, dissolving of the base film from the roller would be unavoidable. A sharp relief in the screen naps with uniformly high screen cross-lines cannot therefore be secured in accordance with the matterto be printed.

The invention is hereinafter more fully described by reference to an example:

For intaglio printing the printing form is produced in the following manner: As in the case of copper intaglio printing, a diapositive is prepared from the original to be printed, the diapositive being copied upon alight sensitive colloid film. For copying purposes a film is used mm; thick, the film being applied to a smooth film carrier-in the present case to Celluloid foil. The copying period must be so determined that copying-through is effected in the white and on the screen cross-lines as far as the film carrier. After being damped the copy is applied with its film side on the printing form carrier, in the present case upon a printing roller. The film carrier now covering the colloid film is dissolved by treatment with an acetone solution and thereby removed. All the colloid film left on the roller is thn treated with hot water of a temperature between and 60 0., whereby the unilluminated parts of the colloid film. are washed away, the copied matter and the screen cross-lines remaining in relief. After being dried the form is ready for printing. For special cases the colloid film may be subjected to subsequent dressing for exthe printing form consisting of the colloid film has been removed by simple washing.

In the same way are produced the printing forms for printing in relief, except that no screen naps are formed but more or less large raised and dried, the printing form in relief is ready for printing.

The method that process of the invention is employed, whole working stages, such as etching, grinding of the copper, and the application of The elimination of the case I ings are commonly produced. complete elimination of the etching, 7 dependent upon correct observation and underinvention is, unlike the known method,- com the production of new copper layers,"

the printing form is made possible without previous knowledge. the

means the difficulties are avoided which are involved in three-colour printing.

I claim:

1. The process of producing a printing form comprising preparing a screened layer of photosensitive co-lloid which on exposure to light becomes water insoluble upon a sheet of soluble material, printing on the uncovered side and fixing to and printed, applying the free that only, and washing unexposed portions of said colloid from said carrier.

2..The process of producing an intaglio printing form comprising forming a laminated sheet of Celluloid coated with a screened light sensitivecolloid, fixing an image of the matter to be