US 2855297 A
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Description (OCR text may contain errors)
Oct. 7, 1958 P. G. SAUNDERS 2, 5,
ELECTROPHOTOGRAPHIC METHOD OF APPLYING ART WORK TO RUBBER FOR ENGRAVING Filed, May 16, 1955 INVENTOR 27/14 6. flan/042s BY M ATTORN United States Patent ELECTROPHOTOGRAPHIC METHOD OF APPLY- ING ART WORK TO RUBBER FOR ENGRAVING Philip G. Saunders, Toledo, Ohio, assignor to Owens- Illinois Glass Company, a corporation of Ohio Application May 16, 1955, Serial No. 508,751
1 Claim. (Cl. 96-1) cast upon the plate during exposure. After exposure an electroscopi-c or developer powder is applied to the plate to form a powder image which is temporarily attached to the charged plate. The powder image is electrostatically transferred to a piece of sheet material such as paper to form the unfixed duplicated copy. The powder image loosely attached to the sheet material normally undergoes a fixing step wherein the powder is fused by means of heat, solvent or the like to the sheet material to form the permanent duplicated copy.
The principal object of the present invention is to provide a simple and inexpensive method of placing art work designs on rubber for engraving the rubber by rubbing a temporary copy of the art work produced by the modified xerographic process onto a sheet of rubber of the required resiliency for forming a printing plate.
a temporary transfer copy of the art work rather than I a permanent copy.
Printing plates employed in printing advertising matter on cardboard or corrugated cartons are usually composed of relatively soft rubber made by either hand engraving the rubber plate itself or hand engraving hard rubber from which a mold is formed. The shaped mold is then used to mold one or more soft rubber printing plates similar to those which are individually hand engraved.
However, before either the hard or soft rubber can be hand engraved, an outline of the desired art work and/ or written material must be placed on the rubber to serve as a pattern for the engraver. Applying art work to rubber in preparation for the engraving is usually accomplished by tracing on paper the desired patter-n of existing art work and transferring the tracing from the paper to the rubber by firmly pressing one against the other. The tracing is generally drawn by an artist, requiring both time and skill to achieve the desired result. In printing with several colors, separate plates must be prepared for each color to be printed by having the tracing drawn with the various colors and impressed onto a rubber sheet as many times as colors employed. The design of each color is then separately engraved to obtain an individual plate for subsequently printing that particular color.
a The preparation of art work designs on rubber'hasfalso been accomplished by sensitizing the rubber and photographing directly to it. The rubber surface is then developed somewhat as a photographic print to disclose the art work design. At present this method has not been widely adopted because it is expensive and requires handling the rubber as a light sensitive film.
The present invention involves the application of the existing process of xerography to obtain a temporary copy of the art work. The xerographic process is not carried through to completion but modified to the extent that the temporary powder image on sheet material which is created by this process is employed to form an image of the art work on rubber. The fixation of the image to the sheet material as normally done in the standard procedure is eliminated.
The xerographic process is used commercially in plants and offices to facilitate the production of copies by electrophotographic means. In the process a sensitive plate consisting of a conductive backing coated with a photoconductive insulating material is charged electrostatically after being thoroughly cleaned. The sensitized plate is then exposed under light to form an electrostatic image of the subject on the plate. A shadow of the subject or an image of the subject created by an optical system is Another object of this invention is to provide a method of producing permanent outlines of desired size of selected art work designs on rubber or other surfaces by utilization of the modified xerographic process.
The specific nature of this invention as well as other objects and advantages thereof will become apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheet of drawing on which is illustrated one embodiment of this invention. s
Referring to the accompanying drawing the figure is a perspective view illustrating the transfer of the art work which is shown in broken lines.
The following procedure is disclosed as the improved method of applying art work to rubber for the purpose of engraving the rubber. The art work to beprinted on cartons, boxes or other articles is selected from large or small patterns, photographs, sketches or cut-outs. Individual or composite layouts of any of these are placed on a suitable backing and arranged in desired form.
The design comprising the subject art work is then electrophotographed by the 'xerographic process onto a sensitized plate having a photoconductive surface electrostatically charged. By the use of a suitable optical system in conjunction with the xerographic equipment, the subject art may be photographed onto a standard xerographic 'plate either full size or enlarged or reduced in size to the exact dimensions required for the printing plate. Qn exposure an electrostatic image is formed on the plate which is converted into a visible powder image when: it is developed. The development is made by cas- 'cading an electroscopic developer powder'over the electrostatic latent image. The powder which generally consists of a pigmented thermoplastic resin is transferred electrostatically in another operation from the plate to a piece of paper in the same powder image.
In order to make this powder image permanent, the usual process contemplates a fixing step wherein the powder is fused to the paper. Normally, it is essential in the fixing or fusing step that the powder image be made permanent on the sheet with no distortion of its shape or position so that the permanent image Will be an exact and lasting reproduction of the powder image. The powder image which consists of pigmented resin particles is usually fused by heat from external heating elements at a temperature only slightly less than the charring point of the paper to avoid discoloration thereof.
In my method the fusible powder image is not permanently fused to the paper but the fixing step of the normal xerog-raphic process is eliminated and the unfused powder image on paper is taken for transfer to a sheet of rubber. The unfused powder image on paper thus comprises a temporary transfer copy for conveying the duplicate image to another surface. An individual transfer copy and printing plate is prepared for each color design to be printed.
As shown on the drawing the sheet of paper which is taken from the modified xerographic process bears the temporary unfixed image 11. The image 11 is formed of fusible or thermoadhesive electroscopic material such as pigmented resin which is an extremely fine powder having substantially spherical particles. The fine particles are smoothly and uniformly distributed over the surface of the image in its development and transferred in the same pattern onto the paper. The image 11 on the paper 10 has fine grain size of uniform density and is slightly tacky in consistency. The image 11 is generally black in color when the most common, black-colored developer powder is used in the Xerographic process. The image 11 may be varied in color by using other dyed developer materials which ,are available for use with xerographic equipment.
The temporary pattern of the art work image 11 which is shown in the form of the letter X is sufliciently adherent to the paper 10 to withstand normal handling of the paper without distortion or destruction of the image. The paper 10 may be inverted or shaken without removing the image 11 but care must be exercised to avoid accidental contact of the image with other materials or surfaces as it may be easily smudged.
A light colored rubber sheet 12 is provided of the proper composition and resiliency to form the printing plate. The sheet 12 is composed of soft rubber which is compounded with a light colored ingredient or painted a light color on its upper surface to provide greater contrast with the image 11. The image 11 may "be placed on the surface of other materials as desired.
The image 11 is placed face down in contact with the rubber sheet 12 without shifting or sliding the contacting faces of the rubber and paper to avoid distorting the outline of the image. With the paper 10 held firmly in position on the rubber sheet 12 the reverse side of the paper 10 is forcefully and uniformly rubbed by hand with a piece of smooth bone, ivory or plastic 13 to transfer the image 11 onto the contacted surface of the rubber sheet 12. In similarly transferring the art work from paper tracings to rubber this operation is commonly referred to as burnishing. After uniformly rubbing the reverse side of the paper 10 above the art work image 11 the paper is smoothly separated from the rubber sheet 12 leaving a clear pattern of the art work of uniform density and definition for engraving.
The powder image 11 is made permanent on the rubber sheet 12 by dusting the transferred image with a fine light colored powder such as talc and rubbing it into the rubber surface. The fine loose particles comprising the powder image 11 are either forced into the porous rubber surface or removed therefrom by the dusting powder. Both the excessive image and dusting powders are removed by wiping the surface of the rubber sheet 12 with a clean cloth leaving a clear imprint of the art work.
By this method outlines of art patterns to be engraved can be quickly prepared eliminating the laborious tracing of artists. The method is cleaner than using a paper tracing and provides good quality outlines to hand engrave. The time involved to prepare the rubber surface for engraving is only a small fraction of that required to prepare the hand tracing on paper.
Various modifications of the method may be resorted to within the spirit and scope of the appended claim.
The method of manufacturing rubber printing dies in the form of artwork designs which method comprises the steps of producing an electrostatically charged pattern of an art work design on the surface of photoconductive insulating material by exposing an electrically charged plate to light passing through a photographic optical system to create a latent image on said plate, depositing electroscopic' developer powder on said pattern to produce a visible corresponding powder image, transferring said powder image to paper, retransferring said powder image to rubber sheet capable of forming a resilient printing die by contacting the image-bearing surface of said paper and said rubber sheet in surface-to-surface relationship, impressing said powder image onto said rubber sheet by the application of pressure to the reverse side of said paper, removing said paper from contact with said rubber sheet, rubbing a fine light-colored dusting powder over the impressed surface of said rubber sheet, removing any excess image powder and dusting powder, and engraving the face layer of said rubber sheet in the outline of said powder image.
References Cited in the file of this patent UNITED STATES PATENTS 1,496,753 Burkley June 3, 1924 1,597,602 Klein Aug. 24, 1926 1,784,912 Scott Dec. 16, 1930 1,784,913 Scott Dec. 16, 1930 2,297,691 Carlson Oct. 6, 1942 2,551,582 Carlson May 8, 1951 2,627,486 Smith Feb. 3, 1953 2,637,651 Copley May 5, 1953 2,653,871 Marsh Sept. 29, 1953