US2088399A - Photoengraving process - Google Patents

Description

July 27, 1937. J. H. GIBSON 2,088,399

PHOTOENGRAVING PROCES S Filed Sept. 22, 1936 5, :1 l l I 2 g 1 L z 2 WITNESS E5 Jfzrnes H. Gcbson' I ATTORNEYS INVENTO R Patented July 27, 1937 UNITED STATES PATENT OFFICE 2,088,399 PHOTOENGRAVING PROCESS James Henry Gibson, Teaneck, N. J. Application September 22, 1936, Serial No. 101,921 1 Claim. (Cl. 101-4013) The invention, therefore, consists in certain novel steps in the process all of which will be more fully hereinafter described and pointed out in the claims.

In the accompanying drawing Figure. 1 is a fragmentary plan view illustrating one step of my improved process;

Fig. 2 is a similar view illustrating the next step in the process;

Fig. 3 is a view in section on the line 3-3 of Fig.

Fig. 4 is a view in section on the line 4-4 of Fig. 2:

Fig. 5 is a fragmentary view in section on an enlarged scale illustrating the printing plate after it has been developed and etched; and

Fig. 6 is a view similar to Fig. 5 illustrating the plate after it has been subjected to pressure of a mat thereon.

The first step of my improved process is to provide a printing plate of suitable metal coated on both surfaces with a sensitized solution. This plate is indicated by the reference character I convenience of the printing plate will be hereinafter referred to as the top surface and the other surface of the printing plate will be hereinafter referred to as the back surface of the plate.

On both the top and back surfaces of the printassume that the surface of the glass plate 3 containing the half-tone negative 4, is the front surface and the other surface the back surface of the said plate.

This transfer of the image to both surfaces of the printing plate is accomplished as follows:

The sensitized top or printing surface of the printing plate I is located directly against the half-tone negative 4 on the front surface of the glass plate 3, and both plates are aligned at. at

least two edges cause it is by this second exposure of the printing plate through the reversed glass plate of reversed thickness that the half-tone dots in the intermediate tones and shadows are merged into solids which,

inated because of the diflusion of the light rays through excessively thick transparency. This step of the process is illustrated in Figs. 2 and 4 of the drawing and results in transferring the image to the sensitized back surface of the printing plate. We then have a printing plate with the images on both sides thereof in exact register.

The printing plate I is then developed, simultaneously developing the images on both sides of the plate which are, as above stated, in exact register. The printing surface of the metal plate which was subjected to direct contact with the negative, gives a. half-tone screen over the entire image that will be used to print from.

After the plate has been developed the next step is'to etch both sides of the plate by subjecting the same to a bath of-suitable acid as is common in the art. When my improved plate is subjected to this etching process, the result will be to provide on the printing surface of the plate at the high lights of the image a large number of points 6. This is the surface of the plate which has been subjected to direct contact with the negative. The other surface, which is referred to as the back surface of the printing plate, is substantially free from these points. This is due to the fact that in carrying out the step of the process shown in Figs. 2 and 4 of practically when this back surface is etched the result will be that the high light portions of the image on high light dots are virtually elimthe back surface of the plate are cut away or recessed as shown at The plate thus developed and etched is illustrated in Fig. 5 of the drawing.

The printing plate is then subjected to the pressure of a mat thereon, which is a step in the ordinary printing process. When the plate is subjected to this or other pressure these portions of the plate containing the high lights of the image, indicated at 6 on the drawing, are forced downwardly below the surfaces of the dark or shadow portions of the image leaving the plate as indicated in Fig. 6 of the drawing.

Thus when the printing is done the darker areas as well as the lighter areas are accentuated. This gives a very much improved result in the reproduction of images and is an economical process as compared with other processes heretofore known and designed for a like purpose.

I claim:

A photo-engraving process comprising sen- 2,088,899 I I v sitizing both surfaces ot 'a metal printing plate producing a half-tone negative on the obverse side of a transparency of substantial thickness,

contacting one of the surfaces of said sensitized side of said transparency so as to bring said negative into direct contact-- plate with the obverse with said one surface of said plate, exposing the contacted transparency and plate to the action of light, contacting the other side of said sensitized plate with the reverse side of said transparency: again subjecting said plate and transparency to the action of light, the substantial remoteness of the half-tone negative from said second side of the plate causing such difiusion that the screen gradations in the intermediate tones and shadows merge into solids and the high light dots virtually disappear, then developing and etching the plate.

Images