US1961927A - Lithographic process - Google Patents

Description

Patented June 1934 UNITED STATES PATENT OFFICE- vLI'I'HOGRAPHIC PROCESS Donald V. Ger-king, New York, N. Y.

No Drawing. Application November 9, 1 931,

Serial-No. 574,039

3 Claims. (Cl. 95-54) This invention relates to lithography and more be printed is then formed, which negative may particularly to lithographic press plates and the be made on wet plate, dry plate, film, paper or preparation thereof. I other transparent medium, and may consist of Photolithographic printing plates or press all or any part of the image or pattern. It is plates are commonly formed of aluminum or zinc made in a convenient size and placed in a pro- 60 coated on one side with a light-sensitive bijection or enlargement camera. The position chromated albumen. In preparing such a plate of the negative in the camera is reversed and the for printing, this coating is exposed to light reversed image is projected on to the back or through a suitable negative of the image which uncoated side of the transparent press plate, it is desired to print, the light rendering insoluble the light passing through such plate and afthat portion of the coating exposed to it. The fecting the surface of the coating directly adjacoating is'then covered with greasy ink and the cent the celluloid plate. The exposure is made plate washed to remove the unaffected coating in every way similar to ordinary photographic leaving the ink retaining surface corresponding enlargements. The reaction of the silver sento the image to be printed. The plate is then sitized gelatin is very rapid and the ordinary exready for printing and is secured to a suitable posure will usuallyv require a relatively few press for the printing operation in the usual seconds. way. After suitable exposure the plate is developed A serious drawback to this process is the length in a tanning solution to render that part ofthe of time necessary to properly prepare such a coating acted upon by the light, which constiplate, and the resulting .inability to make a plate tutes the image to be printed, insoluble in water, by projecting light through a negative spaced the remaining portions of the coating which have from the plate, as, for example, in making an ennot been affected by light remaining soluble. larged image. Because of the fact that the al- After developing, the plate is dried and the coated I bumen coating reacts so slowlyto the light that surface is covered completely with a thin coating a considerable time is required to obtain the of suitable lithographic ink. It is then washed, necessary exposure, vibration, which is present until that part of the emulsion or coating which in all modern buildings, seriously affects the has remained soluble is dissolved off the plate sharpness of the image in the case of projected surface leaving he ink retaining portions of the 30 light. coating which ccrrespond to the design or image An object'oi' this invention is to provide ato be printed. process of making lithographic printing plates The result is the provision of a celluloid press which will greatly expedite the manufacture or transfer plate which is'clamped in the press thereof, which can be carried out with standard and employed in the printing process in the same 35 apparatus such as is now in use and by relatively way that the aluminum or zinc plates are now unskilled labor. employed. It will be apparent that the present A further object is to provide an improved process is applicable to the manufacture of plates form of photolithographic press plate. from celluloid or equivalent materials such, for

These and other objects which will be apparent example, as cellophane, or the like, and it will 40 to those skilled in this particular art are acbe understood that where I use the term celluloid complished by means of the present invention, I intend to cover such equivalent materials. a preferred and practical mode of which is here- The present process renders possible the manuinaiter described. facture of lithographic printing plates by photo- In carrying out the present invention, a photographic projection from negatives of the same or 45 lithographic plate is formed of Celluloid some different size, while reducing the time of exposure equivalent spa translucent material, to such an extent as to eliminate the vibration a d is grained On One face to provide a Surface factor and to greatly reduce the cost per plate.- capable of retaining a coating of light-sensitive I l im a my invention: material thereon. The grained surface is then 1, The process of forming a photolithographic coated with an emulsion of soft, water-soluble printing plate which comprises providing a ce1- l 05 elatin'w carries a sufilcient amount of silluloid plate coated on one side with a soft waterver to make it properly sensitive to light. The soluble light-sensitive silver gelatin, exposing the celluloid plate is of a size to carry the complete face of said gelatin adjacent the celluloid to light image or design to be printed. projected through a negative and through said 55 A suitable negative of the image or pattern to celluloid plate to form an image-printing surface on said plate in substantially the plane of the celluloid, developing the exposed plate to render the light-afiected image-printing portion insoluble, inking said coating to render the imageprinting portion receptive to ink and repellent to moisture, and washing the plate to remove the soluble portion of the coating therefrom and expose the celluloid to form an ink-repelling moisture-retaining surface, whereby upon drying a lithographic printing surface is formed.

2. A lithographic printing plate formed of celluloid and having a lithographic printing surface on one side, on which a non-image ink-repelling atin surface substantially in the plane of the celluloid surface.

' DONALD V. GERKLNG.