US2145036A - Process of preparing printing plates - Google Patents

Description

Patented Jan. 24,; 1939 UNITED STATES PATENT OFFlCE No Drawing.

Application September 27, 1937, Serial No. 165,891

2 Claims. (oi. 95-54;)

This invention relates to printing processes, particularly to the. preparation of intaglio plates, such as are used in photogravure and rotog'ravure printing.* The primary object of the present invention is to provide means whereby an intaglio printing plate, suitable for use in gravure printing, may be prepared much more simply and quickly than is now possible, without the use of carbon tissue, and with the complete elimination of all of the steps involved in its preparation and application, as well as those relating to the etching of the plate and the formation of the resist. I

A further object is the provision of improved means whereby such a, printing plate may .be given the desired printing characteristics by exposure thereof in a camera in the manner of an ordinary photographic plate, and. by a quick and simple finishing process thereafter which gives the plate such characteristics that it'may be used directly in a press for printing.

This case is a continuation in part of my previously filed copending application Serial No. 128,708, filed March 3, 1937.

In carrying out my improved process, I first form upon the surface of a translucent plate a plurality of fine pockets, which may be of the arrangement and order of magnitude of some 150 to the inch, or about the proportions of screens of the sort now employed in connection with gravure printing. The edges of the walls between such pockets define the surface of the finished plate, and during printing are pressed against the surface ofthe paper, the pockets serving to hold the ink. The plate may be formed of Celluloid, glass, a synthetic resin or other suitable translucent material.

The plate is preferably of a size to fit in a camera, which is used for taking the picture which is to form the desired illustration. The pocketed surface of the plate is then covered and the pockets are filled with a sensitized gelatin or emulsion of the order of sensitivity of the emulsion employed upon ordinary camera film.. The plate is placed in the camera with its smooth side toward .the lens, so that upon-ex posure the light enters the pockets from the bottom. The amount of light reaching the gelatin in the various pockets varies in accordance with the difierent amounts of light projected thereon by the lens, corresponding to the scene "taken" by the camera. It will be apparent that V such variations fix thegelatln in the pockets to varying depths.

The emulsion and the exposure are so related that in those areas intended to print darkly, theimpingement of very little light prevents the fixing of the gelatin to any appreciable extent, while the areas to print clear white are distinguished by the fixing of the gelatin in the pockets to their full depth, all shades in between b'e- 6 ing distinguished by proportionately varying v depth of fixation of the gelatin. The gelatin so fixed becomes insoluble in water so that after removal of the exposed plate from the camera, it is only necessary to wash away the unfixed 10 gelatin, to leave pockets which are able to hold more, less or no ink in accordance with the extent to which they are filled with fixed gelatin.

Thus over the entire plate the depth to which the gelatin is fixed in the minutepockets conforms 15 proportionately to the picture taken by the camera. I 7

It will be appreciated that after washing the plate to remove the unfixed gelatin, the plate is ready to be put upon the press and may be 20 used in the conventional or any desired Way, and it will also be'understood that the plate may either be used fiat or shaped to fit the cylinder of a rotogravure press.

Needless to say, the ink used must not affect the gelatin. After completion of the printing job for which the plate was prepared, the fixed gelatin may be dissolved from the pockets by a suitable solvent, leaving the plate in its initial condition and ready for sensitizing and similar re-use.

The emulsion used with my improved process may be extremely'rapid, and of suchcharacter that snapshots may be takenin the usual way by the photographer, and the exposed plate quickly prepared for printing in the manner described.

What I claim is: k 1. The method of preparing an lntaglio printing plate which comprises providing a translu- 40 cent plate with a minutely pocketed surface.- substantially filling the pockets of such surface with a material adapted to be rapidly fixed therein and rendered insoluble to a selected solvent by exposure tolight, placing the plate so 5 removing the unfixed from said pockmin-combination with the method set forth in claim 1, the further-steps of applying inkto the pocketed surface of said plate after treatmentinthe-mannerdescribedandusingthesame for Printing. G AD.