US2431359A - Gravure printing process and device - Google Patents

Description

Nov. 25., 1947.l K. woLFsoN 2,431,359

` GRAVURE PRINTING PROCESSES AND DEVICES original Filed Jan. 21`,y 1941 Upper ema/sion /af/z-Z?` deve/vloed Lower emu/sion layer developed This is The @farm k 9 7 v type section of the composite positive Patented Nov. 25, 1947 UNITED STATES PATENT OFFICE Original application January 21, 1941, Serial No. 375,321, now Patent No. 2,373,732, dated April 17, 1945. Divided and this application January 1l, 1945, Serial No. 572,282

14 Claims.

This invention relates to intaglio printing and more particularly to photographic processes yand devices employed in the manufacture of intaglio printing cylinders and like elements.

This is a division of my United States Letters Patent No. 2,373,732 issued April 1'7, 1945.

Generally, in making intaglio printing surfaces, a photographic positive of the material to be printed is prepared yand light is projected through the positive onto a lighi-I sensitive coating, e. g. carbon tissue, to be transferred onto a metal surface to be later etched for printing. It was early discovered that, Where both picture and type matter are embodied in the material to be printed, diiiiculties in obtaining proper eX- posure of the light sensitive coating are encountered, as employment of suicient light for properly printing both picture and type usually resulted in poor contrast between the background and the finest pictorial tone values, which caused a premature etching of said background in the region of those iinest pictorial tone values.

A proposed solution for the difculty was to prepare a separate positive of the picture matter on yellow tinted lm base, and a separate positive of the type matter on the usual colorless base, combine the two into a single positive and print photographically therefrom as usual. The tinted picture region reduced the exposure of the picture, thereby obtaining balanced exposure of the whole page of material to be printed.

This solution Was satisfactory where the pictures were square, circular, rectangular, elliptical or of any other simple geometrical outline; but was not satisfactory for silhouetted pictures of irregular outline intended to be printed for example against a page as a background.

It was later proposed to produce positives embodying such irregular outline pictures by rst preparing the usual colorless background positive of the whole page and then overlaying the picture with a suitable hand-cut piece of yellow cellophane or the like of proper outline. But this method is time-consuming, inaccurate and costly, and hence not satisfactory.

Another proposed method has been to prepare a positive of the whole page having a yellow tinted back coating, mask out the picture area of that coating with a suitable waterproof lacquer, and then bleach the remainder of the background of the positive. A further variation of this principle was to prepare a colorless positive lm, mask out all except the picture area with Waterproof lacquer, and then dye the picture area yellow. These two methods involved much artistic and 2 careful handwork and consequent, expense and were not reliably accurate, and hence have not been commercially satisfactory.

With the above state of the prior art in mind, it is a major object of the invention to provide a novel speedy, accurate and inexpensive process for simultaneously etching type matter and pictorial matter of any outline on an intaglio `printing surface.

A further object of the invention is to provide a novel speedy and inexpensive process for making a photographic positive suitable for simultaneously accurately photo-etching type matter and pictorial matter of any outline on an intaglio printing surface.

A further object of th-e invention is to provide a novel composite photographic positive having lan actinic ray transmitting background on which is disposed type matter and pictorial matter of any outline, the picture areas being selective to screen actinic light rays to thereby control and provide balanced exposure conditions during photo-etching operations; and novel methods of making the positive. To secur-e this desired screening, the picture areas are preferably. tinted -and/or shaded, as by dyeing, during development.

A further object of the invention is to provide a novel method of making a photographic picture positive for use in photo-etching wherein an actinic ray blocking Ascreen is formed coextensively with the picture area or areas by photochemical operations. Preferably this screen is formed during development on the same or opposite sides of the film base or plate carrying the picture.

Further objects of the invention will presently appear as the description thereof proceeds in connection with the appended claims and the annexed drawings in which:

Figure l is an enlarged section illustrating the structure of a photo-sensitive element of a preferred embodiment of the invention;

Figure 2 illustrates the element of Figure l after exposure and development of the special thin emulsion layer;

Figure 3 illustrates the element of Figure 1 after further development to nal form;

Figure 4 is a diagrammatic view illustrating how the picture positive of Figure 3 is combined with a, positive containing associated type matter for simultaneous optical printing during photoetching of the intaglio printing surface;

Figure 5 i-s a section along line 5-5 of Figure 4; and

. blue sensitive.

Figure 6 is a section illustrating a photo-sensitive element wherein the emulsion layers are on opposite sides of the base.

Brieiiy my invention contemplates improving and speeding up present processes for simultaneously photo-etching picture and type matter on intaglio printing surfaces by producing, photographically and photo-chemically and without hand Worx, photographic positives wherein the picture areas are correctly tinted or shaded, and u using such positives in optical printing operations involved in the photo-etching processes.

To this end, I first make a special photo-serieley partly in the thin emulsion layer and in a suitable developing bath, or wholly in the developing bath as desired. Preferred specific methods of preparing such picture positives are herein later` described. e' Y Preferably the picture area screen or screens are so. tinted as to reduce the amount of actinic lightl which can pass therethrough to the normally blue or actinic light sensitive material commonly employed as the photo-sensitive coating on the surface to be etched, and are therefore tinted yellow or otherwise arranged to reduce actinic light.

After being prepared as above, the tinted picture positive is combined with a photographic positive of the type matter with which it forms a complete page assembly to be printed, and both picture and type matter are optically printed onto the surface to be etched in the usual manner.

As the preferred specific embodiment of my invention, I prepare the picture and type sections of my new composite picture positive separately and independently.

For preparing the picture section of the composite positive, I preferably employ the special sensitive iilm illustrated in Figure 1V. This film comprises a colorless transparent base II which may be of glass, cellulose ester or any suitable substance.

Base Il has on its upper surface a thin layer I2 of a hydrophilic colloid, such as gelatin or polyvinyl alcohol. Layer I2 has high affinity for water and serves to closely bind base I I to an overlying layer of silver halide emulsion I3.

Emulsion layer I3 is of the same thickness, sensitivity and other characteristics as the emulsion layer usually employed on films employed in photogravure photo-etching operations. Emulsion layer I3 is therefore of comparatively slow speed and, like the usual photographic emulsion employed in photogravure work, predominantly Emulsion layer I3 of course contains no coloring material and is adapted to produce upon exposure andy development a Conventional black and white picture positive as in the usual photogravure process.

In'practice, I have found it very satisfactory and inexpensive to simply employ an ordinary commercially available sensitive iilm of the type commonly employed in photogravure work as that part of the sensitive element designated by numerals II, I2 and I3 in'Figures 1 and 5.

Completely and directly overlying emulsion layer I 3 is a second thinner silver halide emulsion layer I4 of special characteristics. Layer I4 is only about one-third as thick as layer I3, being of the same order of thickness asa single color sensitive emulsion layer of ordinary Kodachrome film.

' Layer I4 has extremely high sensitivity and speed, and has a high concentration of very ne silver halide grains. I have found it very satisfactory to employ an emulsion having a speed of about 50 Weston and a suicient concentration of fine silver halide grains'to produce a maximum density of .15 to .2O in the positive.

" Layerll is Vessentially of such diiferent exposure characteristics from layer I3 that, when the latteris properly exposed under the usual exposure light conditions encountered in making photographie positives for use in intaglio printing and subsequently developed, screen area I4' of uniform and high transmission is produced in layer qyerlyirig'the entire picture areain layer I'.l Screen" area IQ'is a uniform light transmis-I sion filter containirigno image details within its outline. W n

Laye? f4 iS 3:15p Plefeablypredommntly Sen.' sitive to the yellow and orange regions` of the visibe spectrum, so that it requires less exposure to light from an'ordinary incandescent electric lamp than the blue sensitive emulsion layer.

I.layerY I4 Ypreferably hasimbedded therein dyestui and color developing agents which produce a dyed picture section'at layer I4( upon exposure and development. I'preferably employ such materials as will'dye the picture section'yellovv so as to lpreiiorninantly reduceactinic light Briefly, layer I4 contains imbedded d yestuifffin-A termediatesr which arey of high molecular wei ht as to be fast .to diffusion, i. e. they do not wanderfrom Ythe emulsion and are not removed byv mechanical eperationssuchas washing during developing. An example cfa suitable 'dyestuff material foiled' Veri S'eiofeoio'ry ,forrollroooos of the invention fororodooing o yellow Siro is pofnnolooozoyl-2-o1ilofooootooiiido- 1o oorboxylo acid which ooobo olkrloiod inthe NH2 group. by along chain'carbon radical such'as `palinity'l, or moleculesof can be coupled by reaction Wiihrho. gene to lolot'oio molooo'lo' .of Suooioni heaviness.``

Layei" 'It @1.501 12T-@kif my @maints Salts 0f 00u' pling developers, Vor color. `'develeping agents, which are temporarily inactive, i. e. inactiveuntil the lm is beingde'veloped afterfexposure. These salts rfi/,ay be almost any[neutral` salts, but prefervably'v comprise neutral'double salts of'rmetals such as Zinc'orcadumpuin."

AS o saiisiooto'ry oorololoiee agent ,It have found it .Soiiofooiory' -to use IJ-ominooliothyl.- aniline combined with tartaric or. vglycolic acid, boric acid Vand Vzinc chloride.' "This mixture provides a temporarily inactive double salt of gincyin the emulsion. V7

asiditiori'to the ,above almost any Suitable y combination of dyestui and color developing aeoois oomrooolyomployoo in .Color photoei-oomV may be incorporated io emulsion loyer Il It 1S constant and prevent such changes in pH as would alter the sensitivity of the emulsions. In practising the invention, I have found a mixture of citric acid and sodium diphosphate to comprise a satisfactory buffer, and I place the mixture in layer I4. The acids in the color developing agents must be considered in providing a buffer since these acids have some buffer function in the system.

I have also found that most satisfactory results are obtained by employing a common antifogging agent, such as nitrobenzimidazole, preferably in emulsion layer I4.

As a protection for emulsion layer I4, I provide an antistatic, antifriction overlayer I5 of gelatin, polyvinyl alcohol or like hydrophilic colloid material which prevents scratches and other physical injuries to the thin emulsion layer.

The above described photo-sensitive element, as shown in Figure 1, is ready for use in the photo-etching process and is exposed through emulsion layer I4, i. e. the light strikes layer I4 first, usually by optical printing from a photographic negative of the picture to be printed. After sufficient exposure to properly expose the less sensitive emulsion layer I3, the element is placed in a weak alkaline bath for a short period, preferably for about one or two minutes. This bath may comprise weak solutions of potassium or sodium hydroxide, organic bases, or ammonia, but preferably comprises a weak solution of borax. This bath sets free and activates the color developing agents in overexposed emulsion layer I4, and development of that layer proceeds.

This developing operation is accompanied by concomitant chemical formation of a yellow dye, and the developed overexposed layer I4 emerges from the developing bath as a thin gray-toned fog layer overlying the lower emulsion layer and having a yellow dye in situ. Layer I4 is sufficiently overexposed to include substantially no details of the picture except outline.

If no dye were present, the picture area would be covered by the thin gray silver fog layer only. For some purposes, such a fog is sufficiently dense and color selective to reduce transmission of actinic light sufficiently for purposes of the invention as will appear, but for more purposes it is desirable to produce a yellow tinted fog layer such as shown at I4 in Figure 2.

In any event the fog layer, with or without the dye, provides a light reducing filter or screen permanently and precisely coextensive with the picture area.

The chemical reactions involved in the abovedescribed color development are the same as in the usual color photography processes involving color developing agents and need not be described in detail for an understanding of the invention.

The partially developed element is then placed in a developing bath of the type usually employed for ordinary photogravure process film, thereby developing lower layer I3 and completing development of the element to the condition shown in Figure 3. A suitable fixing operation completes production of the picture positive P.

Picture positive section P comprises a transparent base II carrying a developed picture portion I3 overlaid by a dyed actinic light reducing filter layer or screen I4' of uniform and high transmission throughout its area, and is ready for use in the optical printing phase of the photo-etching process. Screen I4 is permanently and precisely coextensive with picture area I3.

I preferably assemble picture positive section P with a photographic positive section T, containing the associated type matter to be printed on the same page with the picture, on a layout comprising a colorless mirror glass plate I1 on which the composite page is held by means of a suitable adhesive. Type section T contains the type matter on a colorless film or pellicle and is made in a conventional manner.

Picture section P and type section T are of regular outline and can be easily fitted together in desired page assembly on the layout.

The composite positive on the layout reveals a colorless transparent background for the page to be printed, with the type matter standing out clear and sharp and with the picture precisely covered with a screening layer of thin gray fog having a yellow tint.

The composite positive is placed in the usual optical printing apparatus whereby the picture and type matter for a page are simultaneously projected on the carbon tissue or other sensitized coating of the surface to be etched. The nonactinic layer I4 blocks out a suitable amount of the actinic light in the printing light, and the arrangement therefore provides more exposure for the background than the picture during such optical printing. After development and etching, the intaglio printing surface so produced is of such quality that in the printed page the page background stands out as in relief against the lightest tones of the picture.

My above described process is speedy, and the results are accurate and permanent. The picture area is completely uniformly and precisely screened in the positive, and its outlines are therefore printed sharp and distinct.

Further embodiments and variations While, as above set forth, I prefer to make the picture and type positive sections on separate plates or lms and then combine them in interfitting relation on a suitable layout, I have also found it satisfactory to produce both positive sections on the same transparent film or plate. To accomplish this I mask out a selected portion of the film or plate according to Figure 1, so that the remainder of the plate is suitably reserved for the production of a type matter positive by double exposure or an equivalent operation.

It is immaterial in this embodiment of the invention that the type section of the film or plate has formed thereover the same screening fog layer as the picture section, because this factor can easily be compensated for by shortening exposure of the type'section to allow for the additional density of the type matter section produced by the screening layer.

The term composite positive employed in the claims includes assembly of physically separate i type and picture positive sections, as on the layout above described, as well as the permanent location of both sections on the same film or plate base.

In producing the picture positive, a variation in the above described process consists in providing the color developing agents in the developing solution instead of in the thin emulsion layer I4. Under such circumstances, I employ va regular color developer solution of the type commonly used in color photography to obtain the tinted layer at I4.

It is further within the scope of the invention to omit both the dyestuff intermediates and the color developing agents from emulsion layer I4.

ter on an intaglio printing surface, a transparent support providing a background having a, picture area and an associated type area arranged in correct printing relation, and an overexposed and developed high speed emulsion layer constituting a photochemically produced actinic light reducing screen permanently and precisely coextensive with said picture area to control the transmitted printing light during photo-etching operations.

8. In a photographic positive for use in simultaneously etching pictorial and type matter on an intaglio printing surface, a transparent support having a picture area, and a photochemically produced actinic light reducing screen comprising an overexposed and developed high speed emulsion layer permanently and precisely coextensive with said picture area to control the transmitted printing light during photo-etching operations.

9. In the photographic positive defined in claim 8, said screen being tinted a non-actinic color.

10. In the photographic positive dened in claim 8, said screen comprising a thin fog layer of concentrated suspended ne silver grains.

11. In the photographic positive defined in claim 8, said screen comprising a thin fog layer of 10 concentrated suspended ne silver grains combined With an insoluble yellow dyestuff or an equivalent non-actinic color agent.

12. In the photographic positive dened in claim 8, said screen directly overlying said picture area.

13. In the photographic positive dened in claim 8, said screen being disposed on the opposite side of the support from said picture area.

14. In the photographic positive deiined in claim 8, said screen comprising a concentration of iine silver grains and having a maximum density of about 0.20.

KURT WOLFSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,250,421 Blecher Dec. 18, 1917 1,581,012 Philippe et al Apr. 13, 1926 1,742,658 n Loening Jan. 7, 1930

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