US2201346A - Rotogravure printing process - Google Patents

Description

May 21, 1940. A. w. RABY ET AL ROTOGRAVURE PRINTING PROCESS Filed June 9, 1938 Patented May 21, 1940 UNITED STATES PATENT OFFICE It. Ilarvey, Cooksvil signors to The Canada le, Ontario, Canada, as- Toronto Star, Toronto, Ontario,

Application June a, 1938,8611! No. 212,012

8 Claims.

This invention relates to the process of preparing a printing surface on copper surfaced rolls for the reproduction of photographic sub-'- .iects and the principal objects are to overcome some of the major diiiiculties met with in the preparation of the etched surfaces for intaglio printing, and to produce prints in which the shadow portions will be of uniform tone.

The principal features of the invention consist in the novel steps in the process of'creating an intaglio printing surface in which deep shadows are produced having an intaglio reproduction of a combination of half-tone dots and a fine mesh screen, the intersecting lines of the screen forming a grid surface enclosing a multiplicity of intaglio recesses interspersed between the ordinary half-tone dot recesses.

In the accompanying drawing Figure 1 is an enlarged representation ofaportion of a picture illustrating the arrangement of ordinary halftone dots on a screened negative.

.Figure 2 is a similar illustration of the arrangement of fine intersecting screen lines on a film positive.

Figure 3 is a representation of a contact film positive produced by a combination of the halftone dot-screen negative and the line screen positive which is produced in intaglio on the copper plate by etching.

Figure 4 is an enlargeddetail showing the arrangement of half-tone dots and screen in intaglio.

In carrying this process into effect a continuous tone negative is first produced by photographing the object, This negative is suitably retouched and from this negative is produced a continuous tone positive which in turn is suitably retouched. To this point the process is the same as is practiced in the ordinary gravure process.

A screened half-tone negative is then made from the retouched positive as illustrated in Figure 1 of the drawing.

A very contrasty negative film print is then made from the retouched positive and from this is printed a film positive, with a fine line mesh halftone negative of Figure 1 with the screen shape positive of Figure 2 to produce a final positive representation as illustrated in Figure 3 in which all tones are represented by halftone dots oi' varying sizes except in the deep shadow portions and in such portions there is a combination of half-tone dots and screen.

It will be noted as illustrated in Figure 2 that the screen positive is a fiat or uniform tone and has no influence on the gradation of the image which is carried by the half-tone dots, but the screen being superimposed on the deep shadow surfaces, forms a bearer surface formed of a combination of dot and line screen.

When the final positive, which is represented by Figure 3, is completed it is placed directly over the copper plate or. cylinder which has been previously prepared with a sensitized coating, and it is then "exposed. to light in the usual manner of producing a resist print, after which it is developed and fixed ready for etching.

The etching is' accomplished in a single operation and produces over the ordinary light-tone surfaces an arrangement of intaglio recesses of varying sizes to produce the final printing effect of the shaping and gradation of the image and in those places where the fine line screen is interposed the surface is etched to form a multiplicity of intaglio recesses separated by the fine lines of the screen in the metal between the dot recesses.

It will bereadily understood by those skilled in the art, that where deep shadows occur and particularly where such shadows cover comparatively large areas, the body of ink on such areas will be very effectively retained against being gouged or wiped out, with the result that the ultimate picture produced in the printing will be featured by solid uniform colour tone, which is the principal objective. Further it will be readily appreciated that the various steps in achieving the desired result are of a simple nature ensuring accurate results.

It will also be appreciated that the present process introduces into gravure printing the use of the half-tone screen which, by reason of the outer exposure of paper surface, produces a much more luminous type of print and a better working medium which enables a more faithful reproduction.

What we claim as our invention is:

i. A rotogravure printing process comprising incorporating into aifinal positive film of the image to be reproduced a combination of halftone dots and screen lines by contact exposure thereof through a superimposed half-tone screen I negative and a contrasty continuous tone negative and a transparent line screen so that said positive presents closely spaced screen lines in theshade areas only of the image, exposing a sensitized metal surface through the resultant positive I of the image to be reproduced, developing and finally etching the metal surface.

2. A rotogravure printing process comprising, forming a half-tone negative by exposure through a half-tone screen, forminga screenline positive by exposure of predetermined areas only thereof through a gravure screen, and com bining the half-tone negative image with the screen line positive and reproducing the combined effect thereof on a sensitized metal printing surface by the exposure, developing and etching process.

3. A rotogravure printing process comprising first producing a continuous tone positive and a half-tone screen negative, then from said continuous tone positive producing a contrasty continuous tone negative, then placingsaid continuous tone negative together with a screen having fine and closely spaced transparent intersecting lines over a sensitized film and exposing the latter therethrough to produce a transparent medium having light-obstructing screen lines confined to areas representing the shadow portions of the image, then by the contact and exposure method eifecting the transfer of the halftone screen and line images respectively of said half-tone screen negative and said transparent medium to a transfer medium, and utilizing said transfer medium for the reproduction of the combined half-tone and screen line eifect on a metal printing surface.

4. A rotogravure printing process comprising first producing acontinuous tone negative, then from the negative producing a positive continuous tone image, then from the positive producing a half-tone screen negative, from the continuous tone positive producing by superimposition 'a negative mask having light-penetrable areas corresponding to the dark or shaded areas of said positive, from the mask producing a screen-line positive by exposure of a light-sensitive layer through a fine line screen, combining by superimposition the screen line positive and half-tone screen negative to produce a positive, placing a light sensitive coatingon a metal surface, ex-

posing said coating through the said combined half-tone and line screen positive, and etching the metal surface to produce an intaglio printing plate.

5. A rotogravu're printing process comprising I first producing a half-tone screen negative and a continuous tone positive, then from said continuous tone positive producing a contrasty continuous tone negative, then placing said continuous tone negative together with a screen having fine and closely spaced transparent intersecting lines over a sensitized film and exposing the latter therethrough to produce a transparent medium having light-obstructing screen lines confined to areas representing the shadow' portions of the image, then by the contact and exposure method producing from said half-tone screen negative and said transparent medium a transparent film positive, and then by the contact, exposure and etching method reproducing said positive on a metal printing surface.

6. A rotogravure printing process comprising,

forming a half-tone negative by exposurethrough a half-tone screen, forming a screenline positive by exposure of predetermined areas only thereof through a gravure screen, the gravure screen lines of which are spaced more closely than the rows of half-tone dots, and combining the half-tone negative image with the screen line positive and reproducing the combined effect thereof on a sensitized metal printing surface by the exposure, developing and etching process.

7. A rotogravure printing process comprising, forming a half-tone negative by exposure through a half-tone screen, forming a screenline positive by exposure of predetermined areas only thereof through a gravure screen, and combining the half-tone negative image with the screen line positive with the gravure screen lines acutely intersecting the rows of half-tone dots and reproducing the combined efiect thereof on a sensitized metal printing surface by the exposure, developing and etching process.

8. A rotogravure printing process comprising, forming a half-tone negative by exposure througha half-tone screen, forming a screenline positive by exposure of predetermined areas only thereof through a gravure' screen, the gravure screen lines of which are spaced more closelythan the rows of half-tone dots, and combining the half-tone negative image with the screen line positive with the gravure screen lines acutely intersecting the rows of half-tone dots and reproducing the combined effect thereof on a. sensitized metal printing surface by the exposure, developing and etching process.

AR'I'HUR W. RABY. GEORGE R. HARVEY.

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