US2596754A

US2596754A - Photomechanical copy method

Info

Publication number: US2596754A
Application number: US783913A
Authority: US
Inventors: Edward C Yackel
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1947-11-04
Filing date: 1947-11-04
Publication date: 1952-05-13
Anticipated expiration: 1969-05-13

Description

May 13, 1952 UNHA RDE NE D EMULSION LA YER F/XED AND WAS/IEO PHOTOGRAPH/C ELEMENT RECE/ V/NG JUPPOR T TRAMSFfRR/NG A STRATUM 0F EMULSION w TRANSFER/WED EMULSION 577M TUM EDWARD C YA CKEL INVENTOR m2 BY ATTORNEYS Patented May 13, 1952 UNITED STATES g'rsnr orrics PHOTOMECHANICAL COPY METHOD Application November 4, 1947, Serial No. 783,913

Claims.

This: invention relates to photography and more particularly toa photomechanical copy method for use-in the reproduction of printed matter.

There are a number of well-known photographic'methods'of reproducing designs such as printed matter on paper or other supports. For instance, by the so-called reflex copy method an emulsio'n'layer is exposed'through its support and the printed matter is-reproduced asa negative. Or one may print a negative and a positive therefrom by conventional methods. In the photomechanical art a common practice is to expose a suitable photographic element such as a tissue and to transfer the exposed element to a metal plate after which the unexposed emulsion is washed off the plate or the washing off may occur before transfer of the resist to the plate. However, none of these processes possesses the feature of transferring a thin stratum of a photographic image to a support or a method of making a multi plicity of prints by transferring a plurality of strata from a photographic emulsion layer. I have succeeded-in perfecting a method of doing this which, in general, consists of preparing a photographic image in a substantially unhardene'd layer of colloid vehicle and transferring acontinuousstra-tum of the entire layer to a support;

One object of my invention is to provide a simple" photographic process of reproducing a subject such as printed matter in the manner above-mentioned. Another object is to provide tliem'a'teri'als and photographicand mechanical processes and variations of the same, to which my invention issusceptible; Other objects will become'apparent from the following description of my invention.

According to the broader aspects of my invention a substantially unhardened light-sensitive photographic emulsion layer, such as a g'elatino-silver halide emulsion layer, is exposed toa subject and subsequently at some stage in the processing cyclea thin continuous stratum of the entire layer is transferred to a support.

My'inventi'on will be'better understood by refer'ence to the accompanying drawings wherein Fig. 1 shows in enlarged cross-sectional View the appearance of' a processed photographic element carrying an unhardened emulsion layer containing a silver image.

Fig. 2 shows in enlarged cross-sectional view the method of transferring a stratum of the processed emulsion layerto a receiving support.

Fig. 3 shows in enlarged cross-sectional view 2 the appearance of the transferred emulsio stratum on the receiving .support. I

My invention will now be described in greater detail with reference to the accompanying drawings.

According to the preferred embodimentofmy invention, I take a substantially unhardened light-sensitive silver. salt emulsion layer, such as a gelatino-silver halide emulsion layer; containing little or no hardening agent coated on a suitable support as paper, filin, or other material, and expose by projection or' contact printingto a negative so as to obtain a reverse position,- after which the exposed photographic element is developed in an ordinary black-and- White developer, fixed in a non-hardening fixing bath, and then Washed. After washing, when the emulsion layer is still moist, I rolldown a suitable receiving support, such aspaper, cloth, wood, or similarabsorptive'material, onto the emulsion layer, and, after stripping the receiving support-from the emulsion layer, a thin stratum of emulsion is found transferred to the receiving support; The appearance of the fixed-and-washed photographic element is shown in enlarged cross-sectional view in Fig. 1 wherein layer In is the emulsion support of a proper base carrying the unhardened emulsion layer ll containing the silver image I2. The method of transferring a stratum of the emulsion layer of Fig. 1 to a receiving support is shown in enlarged cross-sectional view in Fig; 2 wherein layer l'fl-is the emulsion support carrying the residual unhardened emulsion layer [3' andresidual'silver image Mwhich are left on support l0 after stripping off the stratum of emulsion l5 containing the stratum of image H on the receiving support IS. The appearance of the transferred emulsion stratum on the receiving support is shown in enlarged cross-sectional view in Fig. 3 wherein layer I6 is the receiving support carrying the emulsion stratum I5 containing the image stratum H.

The above-described process is similar to that disclosed and claimed in the Yutzy and Yackel, UL S. patent application Serial No. 783,914 filed concurrently herewith. However, the present process differs in the respect that in my process a continuous stratum of the entire emulsion layer is transferred to a receiving support whereas in the co-pending process a stratum of only the unhardened image area ofa differentially tanned emulsion layer is transferred to a support.

The following examples are illustrative of my invention but are to be considered as in no way limiting the scope of my invention.

Example 1 An emulsion suitable for use in my process can be made by preparing solutions of (A) 25 grams of gelatin in 1 liter of water at 40 C., (B) 100 grams silver nitrate in 500 cc. water at 20 C. and (C) 35 grams of sodium chloride in 500 cc. of water. Solutions B and C are simultaneously run into solution A at a uniform rate while stirring the latter, over a period of about ten minutes; solution B preferably not being allowed to run in faster than C. Thereafter 400 grams of gelatin in 4 liters of water at 40 C. are added. Preparatory to coating an emulsion layer, 2 cc. of 10 per cent formaldehyde solution may be added to the emulsion providing that a gelatin of poor physical properties has been used, and this composition is then coated on a support such as paper containing no agent tending to further harden the emulsion. After drying, the product is ready for use. The amount of hardening agent added to the emulsion layer depends somewhat upon the characteristics of the particular type of gelatin in use and in general it is unnecessary to use a hardening agent. When a hardener is used, ordinarily it is not necessary to use more of a hardening agent such as formaldehyde than the amount specified. If another hardening agent such as chromium salts or alum is used, due regard is given to differences in hardening activity. The emulsion layer is then exposed to a suitable negative as stated above using suitable light intensity and time of exposure. Following exposure the element is developed in an ordinary black-and-white developer such as one having the following composition:

Water (50 C.) cc 500 p-Methylamino-phenol sulfate gms 3.1 Sodium sulfite (dry) gms 45.0 Hydroquinone gms 12.0 Sodium carbonate (dry) gms 67.5 Potassium bromide gms 1.9 Water to liter 1.0

For use the above formula may be diluted 1 to 4 times, depending on the results desired.

After developing the emulsion layer it is then fixed-out in a fixing bath of the following composition:

Water, about 125 F cc 500.0 Sodium thiosulfate gms 240.0 Sodium sulfite (dry) gms 10.0 Sodium bisulfite gms 25.0 Cold water to liter 1.0

After washing the fixed photographic emulsion well, I may treat the product with a 5-20 per cent solution of urea or one of the gelatin softening solutions shown in the following table:

Percent Formamide 2-20 Ethylene chlorohydrin 5-20 Sodium nitrate 5-20 Glycerol -20 the image on the receiving support. In order to make succeeding prints the emulsion layer residing on the original support is merely moistened again with the solution, for example, of urea or one of the materials above mentioned. Following this the transfer is made to an absorbing support as before.

Example 2 In a manner similar to that of Example 1, the transfer may be made from the washed emulsion layer by placing the emulsion layer in contact with a receiving support having its temperature raised high enough to cause the surface of the emulsion layer to melt and effect transfer of a melted stratum to the heated receiving support. The temperature'selected, of course, is dependent upon the hardness of the emulsion layer, and in certain cases it may be desirable to use a treatment with one of the gelatin-softening solutions above, as well as raising the temperature at which the transfer is made. Successive transfer prints are made by a similar treatment which softens a stratum of the emulsion layer to the desired extent. Naturally, the depth to which the emulsion layer is softened determines the thickness of the transferred stratum.

A number of variations may be made in my process, as will be apparent from consideration of the data in the following table.

processing.

Process No. 5 (Example 1) is the preferred embodiment of my invention principally because of the fewer number of steps required to obtain an optimum number of finished prints. It is apparent that the purpose of my process is to make multiple prints. Ten or 12 prints may be obtained. I may make a number of prints in the manner described, for example, in process No. 5 above, and after the desired number of prints, as 3 to 5, have been made, I may dry the residual emulsion layer on its support and store it away for future use. At a later date I may then resoften the material using water or a solution of one of the softening agents above mentioned, and after this make more prints in like manner. In the processes Nos. 1-5, when I apply a solution for softening a stratum of emulsion layer, this solution is applied previous to making the transfer.

A number of advantages of my process over prior art processes for the multiple reproduction of images are now apparent. My process possesses all of the well-known advantages of silver salt emulsion layers over prior art sensitive materials, such as glue-bichromate layers. Also, my process provides a quick and cheap reproduction method of particular use in the photomechanical art. Furthermore, my process is capable of a wide range of variation both in method of operation and the materials used.

My invention is subject to a number of variations. The vehicle in which the light-sensitive silver salt such as silver halide is dispersed, may be composed of any of a number of substances such as gelatin, polyvinyl alcohol, partially hydrolyzedcellulose esters, partially hydrolyzed polyvinyl esters, and other resins such as polyacrylamide. In-fact, it is only necessary to select an emulsion vehicle which can be swollen by the processing solutions to the extent that the vehicle will adhere to or be absorbed by the receiving support. The silver salt dispersed in the emulsion vehicle is not critical since it may be any of the well-known types such as silver bromide, silver chloride, or silver iodide, or mixtures thereof.

Without departing from the spirit of my invention, an image may be formed in unhardened colloid vehicle by means other than by exposure of a silver salt and subsequent processing thereof. For example, I may form a colored image in the layer as by imbibition and make successive transfers of continuous strata of this layer to receiving support. Similarly, the image in the layer may be formed by means of the well-known toning methods. The principal feature of my process lies in the ability to transfer an image from a soft emulsion layer, no matter what method was used for forming it therein, in the form of a continuous thin stratum, to a receiving support.

Process No. 3 shown in the above table represents a process almost as valuable as the preferred process No. 5. According to this process I can put the agent used for softening the emulsion vehicle into the developer solution and make useful transfers without further treatment. These transfers will have fairly good stability, however, not of archive quality, because the silver halide will print out and some subsequent development will occur tending to darken the highlights and lower the contrast of the image.

It is necessary for the successful operation of the invention that the emulsion layer not be harder than would be the case with gelatin containing 0.25 ounce of formaldehyde (40 per cent diluted 1:3 with water) or 0.7 gm. dry formaldehyde per pound, when freshly coated, or 0.1 ounce of the solution per pound for a sample aged three to six months. By substantially unhardened as used herein, and in the appended claims, it is to be understood that this means a hardness for the emulsion layer of the order obtained with gelatin treated with formaldehyde under the conditions above. Strata of emulsion layers appreciably harder will not transfer satisfactorily.

The expression transferring a continuous stratum of the entire emulsion layer, as used here and in the appended claims, is defined as the means in my process whereby a thin layer of the total surface of the photographic element is carried off onto a receiving support. It does not contemplate transferring just a portion of the surface as in the above-mentioned invention of which I am joint-inventor.

The invention having been described, I would have it understood that the disclosure herein is by Way of example, and included in the invention are all modifications and equivalents falling within the scope of the appended claims.

What I claim is:

1. A method of photographic reproduction which comprises exposing a substantially unhardened light-sensitive gelatino-silver halide emulsion layer to a subject, said layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing in said emulsion layer in substantially unhardened gelatin vehicle an image corresponding to said subject, pressing an ab- .6 scrbent support against said" layer while said layer is moist to cause said layer to adhere to the support and without drying separating said support and layer to transfer a continuous stratum of'the entire layer to saidsupport.

2. A method of photographic reproduction which comprises exposing a light-sensitive substantially unhardened gelatino silver halide photographic emulsion-layer to a subject, said layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing in said emulsion layer in substantially unhardened gelatin, an image corresponding to said subject, pressing an absorbent support against said layer while said layer is moist and free of greasy material to cause said layer to adhere to the support, without drying separating said support and layer to transfer a continuous stratum of the entire layer to said support, rewetting said emulsion layerand transferring another stratum of the entire emulsion layer to an absorbent support.

3. A method of photographic reproduction which comprises exposing a light-sensitive photographic gelatino-silver halide emulsion layer to a subject, said layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing in said emulsion layer in substantially unhardened gelatin an image corresponding to said subject, fixing and washing the developed emulsion layer without hardening it, pressing an absorbent support against said layer while said layer is moist and free of greasy material to cause said layer to adhere to the support and without drying separating said support and layer to transfer a continuous stratum of the entire layer to said support.

4. A method of photographic reproduction which comprises exposing a light-sensitive photographic gelatino-silver halide emulsion layer to a subject, developing in said emulsion layer in substantially unhardened gelatin an image corresponding to said subject, said layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, fixing and washing the developed emulsion layer without hardening it, pressing an absorbent support against said layer while said layer is moist and free of greasy material to cause said layer to adhere to the support and without drying separating said support and layer to transfer a continuous stratum of the entire layer to said support, moistening the remaining emulsion layer and transferring another continuous stratum of said emulsion layer to an absorbent support.

5. A method of photographic reproduction which comprises exposing a light-sensitive substantially unhardened gelatino-silver halide emulsion layer to a subject, said layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing in said emulsion layer in substantially unhardened gelatin an image corresponding to said subject, treating said emulsion layer with a gelatin softening agent, pressing an absorbent support against said layer while said layer is moist to cause said layer to adhere to the support and without drying separating said support and layer to transfer a continuous stratum of the entire layer to said support.

EDWARD C. YACKEL.

(References on following page) REFERENCES CITED Number The following references are of record in the 1944'123 file of this patent: 2,367,939

UNITED STATES PATENTS Number Name Date Re. 20,694 Miller Apr. 12, 1938 Number 116,720 Loemmel July 4, 1371 168,578 663,539 Giesecke Dec. 11, 1900 226,598 1,567,333 scharschawsky Dec.29,1925 10 231,413 1,793,070 Eldridge Feb. 17, 1931 324,330

Name Date Fleishmann et a1. J an. 16, 1934 Gregory Jan. 23, 1945 FOREIGN PATENTS Country Date Great Britian June 1, 1922 Great Britain Dec. 22, 1924 Great Britain Apr. 30, 1926 Great Britain J an. 13, 1930

Claims

1. A METHOD OF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES EXPOSING A SUBSTANTIALLY UNHARDENED LIGHT-SENSITIVE GELATINO-SILVER HALIDE EMULSION LAYER TO A SUBJECT, SAID LAYER BEING NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED, DEVELOPING IN SAID EMULSION LAYER IN SUBSTANTIALLY UNHARDENED GELATIN VEHICLE AN IMAGE CORRESPONDING TO SAID SUBJECT PRESSING AN ABSORBENT SUPPORT AGAINST SAID LAYER WHILE SAID LAYER IS MOIST TO CAUSE SAID LAYER TO ADHERE TO THE SUPPORT AND WITHOUT DRYING SEPARATING SAID SUPPORT AND LAYER TO TRANSFER A CONTINUOUS STRATUM OF THE ENTIRE LAYER TO SAID SUPPORT.