US2827726A

US2827726A - Image-engraving plate and process of producing the same

Info

Publication number: US2827726A
Application number: US203310A
Authority: US
Inventors: George F Stradar
Original assignee: Fairchild Camera and Instrument Corp
Current assignee: Fairchild Semiconductor Corp
Priority date: 1950-12-29
Filing date: 1950-12-29
Publication date: 1958-03-25
Anticipated expiration: 1975-03-25

Description

March 25; 1958 G.1F.STRADAR 2,827,726

IMAGE-ENGRAVING PLATE AND PROCESS OF PRODUCING THE SAME Filed Dec. 29, 1950 FIG.1

- INVENTOR.

GEORGE F. STRADAR ATTORNEY ateint @fiice 2,827,726 Patented Mar. 25, 1958 MAGE-ENGRAVING PLATE AND PRQCESS F PRODUCING THE SAME Application December 29, 1950, Serial No. 293,31-il 15 Claims. (CL 41-21) This invention relates to an engraving plate for reproducing images by printing processes and to a process of producing the same and, while it is of general application, it is particularly suitable for use in the machine for producing screened relief pattern image plates of the type described in the copending application of John A. Boyajean, Jr., Serial No. 40,594, filed July 24, 1948, now Patent No. 2,575,546, and assigned to the same assignee as the present application.

In aforesaid copending application there is described a machine designed and intended to be used in the place of well-known photochemical processes for making plates from photographic prints, negatives, or other images for reproduction by printing or like processes. In general, that machine comprises a pair of synchronously rotatable cylinders for individually supporting a plate and an image sheet and a pair of reciprocable carriages individually including a photoelectric pick-up system and a plate deforming tool for respectively scanning the image sheet cylinder and the plate cylinder. The machine also includes means responsive to the output of the pickup system for actuating the tool, means for reciprocating the carriages synchronously; and an electrical screen generator driven synchronously with the cylinders and connected to modulate the output of the pick-up system.

In the operation of a photoengraving machine such as described in aforesaid 'copending application, it is customary to use an image-reproducing plate comprising a flexible sheet of clear plastic material, such as cellulose nitrate, on which the image is formed as a screened relief pattern by a heated engraving stylus which is actuated by the photoelectric image-scanning device and which thermally decomposes the material of the plate to form the desired relief pattern for image reproduction. in such an operation it is difiicult to determine from an inspection of the engraved plate the quality or character of the image formed thereon. At the same time, it would be highly desirable to be able to tell from a mere inspection both the quality of the reproduced image, such as its detail and depth, and also the general subject of the image, in order to facilitate filing and selection from the files for subsequent use.

It is an object of the present invention, therefore, to provide a new and improved engraving plate for reproducing images by printing processes from which, after engraving,the quality and character of the image formed thereon are readily revealed by a mere inspection.

It is another object of the invention to provide a new and improved engraving plate for reproducing images by printing processes in which the plate has a surface layer treated in such a manner that, after engraving, the quality and character of the image formed thereon are readily revealed by inspection.

it has been found that the foregoing objects can be achieved by treating the surface portion of the engraving plate in such a manner as to impart thereto a pronounced or contrasting'color which, upon engraving, gives a mar ed contrast between the engraved surface and the body of the image plate and provides a clear indication of the quality and nature of the image engraved upon the plate.

In accordance with the invention, an engraving plate for reproducing images by printing processes comprises a finished surface sheet of deformable soluble plastic material only one face thereof having a surface portion treated with a mixture of a dye and a mutual solvent for the plastic material'and the dye, the treated surface material retaining substantially the original character of the finished surface. By the term printing processes, as used herein and in the appended claims, is meant any process by which a plate carrying a screened relief pattern may be utilized to produce multiple reproduced images, of which the most usual example is the conventional printing process. By the term deformable material, as used herein and in the appended claims, is meant a material that may be cut, gouged, decomposed or otherwise deformed to form an image-reproducing plate.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, while its scope Will be pointed out in the appended claims.

Referring now to the drawing, Fig. 1 is a perspective view of an image-engraving plate of the type to which the invention may be applied, while Fig. 2 is an enlarged cross-sectional fragmentary detail view of a portion of the plate of Fig. l to aid in an understanding of the invention.

Referring now more particularly to the drawing, a plate for reproducing images by printing processes as shown in Fig. 1 comprises a sheet 16 of deformable plastic material having preformed reversely bent end flanges 1-1 and 12 to aid in securing the plate to the appropriate supporting carriage of an engraving machine. The plate 14) has a surface portion treated with a mixture of a dye and a mutual solvent for the plastic material and the dye. This treated surface portion is shown more clearly in Fig. 2, which is very much enlarged and in which the thickness of the treated surface portion 16a is exaggerated for the sake of clarity. There are shown on the plate in Fig. 2 a series of deformations or pits ltlb (which are exaggerated in size and spacing for the sake of clarity) such as might be formed by the engraving tool in engraving a single line across the image plate. As explained hereinafter, the treated surface portion 1th: is of a color which contrasts sharply with .the body of the image plate 19, which may be a clear transparent or colorless plastic. The deformations 1% show that the engraving tool, in forming the deformations 1%, has penetrated to a depth extending through the treated surface layer lilo. Therefore, these deformations 10b appear as small colorless dots in the colored surface layer 19a.

The image-engravingplate may be formed of any suitable plastic material such as a thermo-plash'c resin, it only being necessary that it be a material soluble .in a solvent for the coloring dye. By Way of example, the plate 10 may be formed of a sheet of cellulose nitrate with an added plasticizer, for example, approximately 25% by weight of camphor. The plastic sheet may be formed in any conventional manner, for example, as described at pp. 196-197 of Modern Plastics Encyclopedia1948, Plastics Catalogue Corporation, New York. The surface portion 10a is treated with a mixture of a completely vaporizable solvent, for example, a lower aliphatic alcohol such asa methyl, ethyl, propyl, isopropyl or butyl alcohol and a dye soluble therein. One example which has been found eminently satisfactory is a mixture of methyl alcohol and a spirit-soluble aniline dye, such as methyl violet (Color Index No. 680), the latter characterizingthe invention:

being in a concentration of the order of 0.2% and preferably within the range of 0.1% to 0.5% by weight of the solvent.

. Among other materials suitable for forming the imageengraving plate of the invention'are the following:

Sheet l\Iaterial Solvent An estere.. g. amyl, ethyl, or butyl acetate; a ketone-e. g. methyl ethyl ketone;

An alcohol-e. g. isopropyl, methyl or ethyl; a ketonee. g. methyl ethyl ketone; an esteramy1, ethyl, or butyl acetate.

An ester-e. g. amyl, ethyl, or butyl acetate; a ketonee. g. methyl ethyl ketone; an alkylene halide-e. g. ethylene dichloride; an aromatic hydrocarbon-e. g. toluene.

Acetone, benzene, toluene xylene,

ethyl acetate.

Polystyrene or Methyl meth acrylate polymers.

Cellulose acetate, Cellulose acetate butyrate.

Vinyl chloride acetate polymers.

Ethyl cellulose ether Among other spirit-soluble aniline dyes suitable for use with the materials and solvents listed in the preceding table may be mentioned the following, with their respective Color Index numbers: crystal violet (C. I. 681),

' oil crimson (C. I. 258), pheno-safranine (C. I. 840),

' factory results by using a commercial Pottdevin glueing machine with a coating or inking roller dipping in a well of the solvent and dye mixture. If desired, there may be provided an idler roller adjustably spaced with respect to the inking roller in order to control the amount of mixture carried by the latter. to the sheet.

The amount of the mixture applied to thersheet is not critical but is adjusted subjectively by the operator to get a desired degree of color saturation. The amountof mixture should be controlled so that it penetrates the surface of the sheet to a depth substantially less than the maximum deformation of the sheet during the engraving process, for example, to a depth of the order of 0.0001 inch. The exact amount of treating mixture can be best determined by experiment in the light of the foregoing criteria. 7

It has been found that the amount of the treating mixture required to treat a given surface area is affected by variations in atmospheric temperature and humidity. For example, in treating a sheet of cellulose nitrate with a mixture ofmethyl alcohol and aniline dye, it has been plastic sheet is purely a physical one involving no chemical reaction. V

(2) The mixture thoroughly penetrates the surface portion or layer of the engraving plate and is to be contrasted with coatings adhering to the surface thereof which tend tobe abraded'or rubbed-off in handling or by the spacing shoe of the engraving machine.

(3) The engraving surface of the finished plate must be undamaged by any softening or chemical reaction with the treating mixture, in order to prevent abnormal deformation of the surface of the plate by the engraving 1 tool.

found that a quart of the mixture will treat from 20,000

to 200,000 square inches of the sheet material. This;

variation is apparently due to condensation of atmospheric moisture on the sheet and in the container of the coloring mixture due to cooling by the rapid evaporation of the solvent. This condensation increases as the temperature' is lowered and as the humidity rises. Excessive condensation of atmospheric moisture impairs the character of the treated surface portion of the plastic sheet, softening it and rendering it susceptible to removal by the spacing shoe of the engraving machine, which usually contacts the engraving plate in advance of the engraving stylus. The presence of an excessive amount of moisture is manifested by what is termed blushing, which appears to be a whitish precipitate formed by moisture absorbed by the temporarily softened plastic material. When such a phenomenon is observed, the treating mixture should be discarded and a fresh quantity prepared.

There are a number of'characteristics and criteria (1) The action of the solvent and dye mixture on the surface. I

(4) The treating mixture preferably should leave no unabsorbed residue on the surface of the plate which will adhere to the engraved plate after engraving or fill in the engraved deformations. To this end, the dye should a be completely soluble and the solvent. should be completely vaporizable. 7

While there have been described what are at present considered to be the preferred embodiments of themvention, it will be'obvious to those skilled in'the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall Within the true spirit and scope of the invention.

What is claimed is: Y I

1. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of deformable soluble plastic material, only one face thereof having a surface portion treated with a mixture of a dye and a mutual solvent for the plastic material and the dye, said treated surface material retaining substantially the original character of the-finished surface.

- 2. An engraving plate for reproducing images by printing processes comprising: 'a finished surface sheet of deformable soluble thermoplastic resin, only one face thereof having a surface portion treated with a mixture'of a dye and a mutual solvent for the thermoplastic resin and the dye, said treated surface material retaining substantially the original character of the finished surface.

3. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of cellulose nitrate, only one face thereof having a surface portion treated with a mixture of a dye and a mutual solvent for cellulose nitrate and the dye, said treated surface material retaining substantially the original character of the finished surface. a p

4. An engraving platefor reproducing images by printing processes comprising: a finished-surface sheet of cellulose nitrate, only one face thereof having a' surface.

portion treated with a mixture of an alcohol and an alcohol-soluble dye, said treated surface material retaining substantially theoriginalcharacter of the finished 5. An engraving plate 7 ing processes comprising: a finished-surface sheet of cellulose nitrate, only one face thereofhaving a surface portion treated with a mixture of approximately methyl alcohol and an aniline dye, said treated surface cellulose nitrate, only one face thereof having a surface portion treated with a mixture of approximately 95% methyl alcohol and an aniline dye in a concentration in for reproducing images by printthe range of 0.1% to 0.5%, said treated surface material retaining substantially the original character of the finished surface.

8. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of polystyrene, only one face thereof having a surface portion treated with a mixture of an acetate and an acetatesoluble dye, said treated surface material retaining substantially the original character of the finished surface.

9. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of methyl methacrylate polymer, only one face thereof having a surface portion treated with a mixture of an acetate and an acetate-soluble dye, said treated surface material retaining substantially the original character of the finished surface.

10. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of deformable soluble plastic material, only one face thereof having a surface portion treated to a depth less than the maximum deformation by engraving with a mixture of a dye and a mutual solvent for the plastic material and the dye, said treated surface material retaining substantially the original character of the finished surface.

11. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of deforrnable soluble plastic material, only one face thereof having a surface portion treated to a depth of the order of 0.0001 inch with a mixture of a dye and a mutual solvent for the plastic material and the dye, said treated surface material retaining substantially the original character of the finished surface.

12. An engraving plate for reproducing images by printing processes comprising: a finished surface sheet of deformable soluble plastic material, only one face thereof having a surface portion treated with a mixture of a dye and a completely vaporizable mutual solvent for the plastic material and the dye, said treated surface material retaining substantially the original character of the finished surface.

13. An engraving plate for reproducing images by printing processes comprising: a finished-surface sheet of deformable soluble plastic material, only one face thereof having a surface portion treated with a mixture of a dye and a mutual solvent for the plastic material and the dye, said solvent being chemically inert with respect to said plastic material and said dye, said treated surface material retaining substantially the original character of the finished surface.

14. The process of producing a finished-surface engraving plate for reproducing images by printing processes which comprises treating a surface portion of only one face of a deformable plastic material with a solution of a dye in a mutual solvent for the dye and the plastic material so as to impregnate the material with the dye to a depth less than the maximum deformation encountered in engraving while retaining substantially the original character of the finished surface.

15. The process of producing an engraved plate for reproducing images by printing processes which comprises applying a heated engraving stylus, in a predetermined pattern, to a finished-surface sheet of deformable thermoplastic material, only the engraving side thereof having a surface portion treated to a depth less than the maximum deformation encountered in engraving with a mixture of a dye and a co-solvent for the thermoplastic material and the dye, said treated surface material retaining substantially the original character of the finished surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,900,877 Hickman Mar. 7, 1933 1,957,888 Hickman May 8, 1934 2,314,975 Ford Mar. 30, 1943