US3253923A - Process for intensifying and fixing print-out images - Google Patents

Description

United States Patent 3,253,923 PROCESS FOR INTENSIFYING AND FIXING PRINT-OUT IMAGES Edward Charles Timothy Samuel Glover and Eric Thomas Smith, Wealdstone, Harrow, England, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Aug. 31, 1962, Ser. No. 220,878 5 Claims. (Cl. 96-60) This invention relates to novel processes and compositions for developing and stabilizing exposed photographic materials, which have been given sufficient exposure to print out a visible silver image. 7

Certain recording papers, when exposed imagewise by a high intensity lamp in an electrical recording machine will provide a visible record as a printed-out silver image without any chemical treatment. This record may only be viewed at low light levels and must be stored in the dark in order to prevent print-out of the background to the point that it masks the image.

It is possible to develop and fix such exposed materlals in the manner conventional for exposed silver halide emulsions but it is found in practice that the development stage must be very carefully con-trolled owing to the ease with which the background silver halide, which has normally received sufi'icient low level illumination to have a developable latent image, can develop and mask the :wanted image.

An exposed silver halide film having a recorded 'printout image can be stabilized by treatment with a complexing agent under conditions that result in very little loss of silver complex from the emulsion and then treated with a developer that intensifies the print-out image by physical development of complexed silver already present around silver nuclei in the print-out image. It is possible under these processing conditions to achieve a high discrimination between the recorded print-out image and its background which may have been exposed enough to produce a latent image. However, this processing system still involves two stages; complexing of the silver halide in a stabilizing bath followed by developmei'it in a suitable developer.

An object of the present invention is to provide a process, and a solution for use in the process, whereby simultaneously a printed-out silver image in an exposed film of silver halide emulsion is intensified and the silver halide is stabilized by washing the film in a single-bath processing solution. According to the present invention, there is provided a monobath processing composition comprising a developing agent in alkaline solution with a concentration of silver halide complexing agent that is sufficiently high with respect to developer concentration to insure that substantially all the silver halide in an exposed emulsion layer treated with the composition is converted into complex form before any substantial visible image can be formed by chemical development of a latent image.

Non-staining developing agents are preferred so that records can be treated and stabilized by the monobath without need for washing afterwards. A preferred combination of non-staining developing agents comprises 1 part by weight of l-phenyl-3-pyrazolidone and 10 parts by weight of ascorbic acid, although it is to be understood that other developing agents may be used in accordance with the present invention.

The term complexing agent includes compounds which form a light-inert silver compound by reaction with undeveloped silver halide and which have little or no Patented May 31, 1966 action on developed silver, such as alkali metal thiocyanates, thiosulphates, and the like. The silver complex solution preferably should be light colored or transparent in order not to interfere with the viewing of the final image. It is more convenient to permit most of the complexed silver halide to remain in the processed emulsion layer rather than to wash away the complex. However, processes in accordance with the present invention do not preclude the possibility of washing away such silver complex after treatment with the monobath.

The silver halide complexing agent must be present in a concentration sufiiciently high with respect to the concentration of silver halide developer to complex silver halide in the latent-image before a visible image can be developed therefrom by chemical development. Thus,

substantial chemical development of the latent image is avoided while the printed-out image is intensified by physical development around the finely divided silver nuclei therein. Silver is reduced around these nuclei from complexed silver halide in solution. To provide short processing times the complexing agent should be as active as possible, so that activity of the developing agents can be correspondingly increased without causing chemical development. Alkali metal thiocyanates are particularly useful silver halide complexing agents for use according to the present invention, as both are very active and are stable in the alkaline solution that is necessary for development. Concentration of the complexing agent should be greater than grams per liter, preferably bet-ween and 250 grams per liter. The following example describes in detail a preferred embodiment of theinvention. A conventional silver halide print out paper, of the type in which about 90% of the silver halide is AgBr, was exposed in a Ha-rtmann and Braune Mercury Vapour Recorder to print out a line image, both with and without postexposure of the paper to ambient illumination. The exposed paper was then immersed in a processing solution,

whose composition is shown below, for 30 seconds at 20 C., then squeegeed and dried. In each case, a stable image was obtained with very low background density.

PROCESSING SOLUTION Potassium thiocyanate Water to make 1 liter. v

Samples of exposed recording paper which have been processed in the above solution at different times between 30 seconds and 1 hour show very little variation in quality. Provided the recording paper has not had suflicient extraneous exposure to print out the background and completely mask the recorded image, it can be satisfactorily processed by the above processing solution.

The temperature at which paper may be processed in the above solution is not critical and prints have been processed satisfactorily at 30 C.

Other organic silver halide developers can be substituted for 1-phenyl-3-pyrazolidone and ascorbic acid developer which was preferred in the example for its non-staining quality. Examples are: Hydroquinone, metol-hydroquinone, other 3-pyrazolidones such as those listed in US. Patent No. 2,685,516, August 3, 1954, and the like. Other complexing agents may be used instead of an alkali metal thiocyanate, which was preferred in the example for its stability in alkaline solution. Examples are: sodium thiosulfate and the like.

The invention has been described with reference to certain preferred embodiments and it will be understood that modifications and variations may be made within the scope of the invention as described above and as defined in the following claims.

We claim:

1. A method for intensifying and fixing a printed-out silver image in an imagewise exposed film of silver halide print-out emulsion, comprising the step of:

washing the exposed film in an alkaline processing solution containing a silver halide developer and an alkali metal thiocyanate silver halide complexing agent for time sufi'lcient to intensify the print-out image by physical development, the concentration of saidcomplexing agent in the solution being s'ufiiciently high with respect to concentration of developer to stabilize substantially all exposed and unexposed silver halide in the film before occurrence of substantial chemical development.

2. The method of claim 1 wherein said silver halide developer consists of phenidone and ascorbic acid.

3. The process of claim 1 wherein said developer consists of 1 part by weight of phenidone and 10 parts by weight of ascorbic acid, and said complexing agent consists of at least 70 parts by weight of alkali metal thiocyanate.

4. The process of claim 1 wherein said processing solution consists of Potassium thiocyanate 150 Water to make 1 liter.

5. The process of claim 1 wherein the concentration of said complexing agent is in the range from 100 to 250 grams per liter.

References Cited by the Examiner UNITED STATES PATENTS 2,751,300 6/1956 James et a1. 2,782,120 2/ 1957 Goldhamrner. 2,875,048 2/1959 Ha-ist et al.

OTHER REFERENCES Photographic Science and Engineering, vol. 5, Number 4, July-August 1961-, pp. 198-203.

J. TRAVIS BROWN, Acting Primary Examiner.

' NORMAN G. TORCHIN, Examiner.

' A. D. RIC CI, C; E. DAVIS, Assistant Examiners.

Claims (1)

1. A METHOD FOR INTENSIFYING AND FIXING A PRINTED-OUT SILVER IMAGE IN AN IMAGEWISE EXPOSED FILM OF SILVER HALIDE PRINT-OUT EMULSION, COMPRISING THE STEP OF: WASHING THE EXPOSED FILM IN AN ALKALINE PROCESSING SOLUTION CONTAINING A SILVER HALIDE DEVELOPER AND AN ALKALI METAL THIOCYANATE SILVER HALIDE COMPLEXING AGENT FOR TIME SUFFICIENT TO INTENSIFY THE PRINT-OUT IMAGE BY PHYSICAL DEVELOPMENT, THE CONCENTRATION OF SAID COMPLEXING AGENT IN THE SOLUTION BEING SUFFICIENTLY HIGH WITH RESPECT TO CONCENTRATION OF DEVELOPER TO STABILIZE SUBSTANTIALLY ALL EXPOSED AND UNEXPOSED SILVER HALIDE IN THE FILM BEFORE OCCURRENCE OF SUBSTANTIAL CHEMICAL DEVELOPMENT.