US2709135A

US2709135A - Process for the direct production of positive photographic images

Info

Publication number: US2709135A
Application number: US217910A
Authority: US
Inventors: Weyde Edith
Original assignee: Agfa AG
Current assignee: Agfa Gevaert NV
Priority date: 1950-03-29
Filing date: 1951-03-28
Publication date: 1955-05-24
Anticipated expiration: 1972-05-24
Also published as: FR1080425A; BE502129A; CH291535A; GB701051A; DE825349C

Description

May 24, 1955 E WEYDE 2 709 13 PROCESS FOR THE DIRECT PRDDUCTION 1 5 CF POSITIVE PHOTOGRAPHIC IMAGES Filed March 28, 1951 coLLo/0 LAYER CONTAINING HYPO 3 ZIIIIIIIIlI/g WATER PERMEABLE PAPER SILVERHALIDE EMULSION, LAYER CUNTAIN/NG PHOTOGRAPH/0 DEVELDPER PAPH? BASE INVENTOR:

EDITl-I WEYDE 43, ATTORNEYS United States Patent Ofiiee 2,709,135 Patented May 24, 1955 PROCESS FOR THE DIRECT PRODUCTION OF POSITIVE PHOTOGRAPHIC LVIAGES Edith Weyde, Leverkusen-Burrig, Germany, assignor to Agfa Aktiengesellschaft fiir Photofabrilration, Leverkusen, Germany, a corporation of Germany Application March 20, 1951, Serial No. 217,910

Claims priority, application Germany March 29, 1950 4 Claims. (Cl. 95-88) This invention relates to a process for the direct production of positive photographic images.

It is an object of the invention to produce direct positive silver images on very thin sheets of a water-permeable material.

Further objects will be apparent from the following description.

In French Patent 879,995 there is described a photographic process for the direct production of positive images according to which a light sensitive silver halide emulsion (negative) layer after being exposed to an object is developed in the presence of a silver halide solvent, said silver halide emulsion layer being in close contact during said developing process with a light nonsensitive reception (positive) layer containing nuclei for development. In this process the exposed part of the silver halide layer is developed to a negative image and part of the unexposed silver halide is dissolved and transferred to the reception layer where it is reduced by the catalytic action of the nuclei for development to a positive silver image. sists in applying said negative layer and said reception layer to separate supports and in pressing together both layers during the developing process, whereafter these are separated from each other. In this process it has proved to be advantageous to incorporate the developing substances in the negative silver halide layer and the substance required for dissolving the non-exposed silver halide, for instance, sodium hyposulphite, in the positive layer. For this purpose, the reception material has to be provided with a coating, for instance, of gelatine or another water-permeable colloid, containing the silver halide solvent and the nuclei for development required for producing the positive image. This process is particularly suited for the production of technical prints, for instance, for the reproduction of drawings, documents etc. If the positive images are produced on transparent reception layers they may be used as intermediate prints for the diazo type process. The reception material used for this process cannot be produced in any desired thickness, since the colloids containing the silver halide solvents can be applied only to relatively thick supports. Therefore, it was not possible up to the present to obtain prints on very thin materials, for instance, on paper customarily used for air-mail.

In accordance with the present invention it has been found that direct positive images are produced on extra ordinarily thin, water-permeable materials, for instance, sheets of regenerated cellulose or sheets of paper weighing about 15-30 grams per square meter, by placing such sheets in the process referred to above between the light sensitive silver halide layer containing a developing substance and a paper or film support of normal thickness coated with a layer containing the silver halide solvents and, if desired, nuclei for development, and after soaking with an alkaline solution, pressing together all three layers, preferable mechanically. The silver halide solvent dissolves in the developing solution, passes through One embodiment of said process conthe very thin intermediate sheet of paper, regenerated cellulose etc. and dissolves at least part of the nonexposed silver halide of the negative layer. Thereupon the dissolved silver salts ditiuse backwards to the thin sheet of paper, regenerated cellulose etc. where the greater part thereof is retained and reduced to form a positive silver image. Even in case the layer with the silver halide solvents contain additional nuclei for development the positive image is produced almost exclusively on the thin, intermediate sheet of paper, regenerated cellulose etc. After separating the three layers after about 1 minute, generally a rather weak positive image is obtained on the thin, intermediate sheet of water-permeable material if the latter does not contain nuclei for development. A perfect image of the object is obtained by using an intermediate sheet containing nuclei for development. Nuclei for development are substances which cause catalytically the reduction of the dissolved silver halide by the developing substances after their diitusion into the reception material. By way of example there may be cited colloidal silver, colloidal silver sulfide, colloidal silver selenide, colloidal silver telluride, colloidal gold. Furthermore, there may be used substances as, for instance, sodium sulfide, from which the nuclei for development are formed during the development.

The nuclei for development or the substances producing them may be incorporated in the intermediate sheet in different manner. The sheets are, for instance, impregnated With solutions containing nuclei for development, such as colloidal silver. They may also be bathed in dilute solutions of silver nitrate as, for instance, in an alcoholic solution containing 0.001% silver nitrate.

Furthermore, it is possible to incorporate these nuclei for development in the thin sheets already during their production. When employing different types of thin paper, it may happen that the positive image produced thereon-also without a previous special treatment for the production of nuclei for development-is very different in strength. Apparently some kinds of paper contain substances (originating from the gluing process which may act as nuclei for development so that the addition of special nuclei for development or substances producing such nuclei for development may be dispensed with.

The process of the present invention may be varied Within wide limits. Thus, it is possible, for instance, to add at least part of the developing substance and/or the silver halide solvent to the developing solution. Furthermore, the thin sheet on which the positive images are to be produced and/ or the silver halide emulsion may contain substances influencing the tone of the image, for instance, mercapto compounds. Such substances are described, for instance, in German Patent 473,000.

The invention will be further illustrated by the fol lowing example and in the drawing in which a crosssection of the materials described in the example is shown in the order in which they are pressed together during development.

Example A light sensitive material is obtained by coating photographic paper 1 of normal thickness (85 g./m. with a silver-chloride-bromide emulsion layer 2 containing per liter 20 g. of hydroquinone, 20 g. of potassium metabisulfite and 0.05 g. of 1-phenyll-rnercaptotetrazole (coating thickness corresponding to 1-15 g. of silver/ m.**). For the production of the reception layer 4 there is coated an 8% gelatine solution containing 30 g. of NazSzOs per liter, on a paper support 5. As a thin, intermediate layer 3 there is used a weakly sized thin typeas writing paper (Weighing 30 g./m. which is immersed in at 0.01% solution of colloidal silver and dried. After the exposure of the light sensitive layer to an object, the latter as well as the intermediate layer and the reception layer .are drawn through a solution containing per liter of water 100 g. of sodium sulfite and 20 g. of sodium hydroxide. Immediately after leaving the solution or when still in the solution the three materials are pressed together in such a Way that one side of the intermediate layer is in contact with the light sensitive layer and the other side with the reception layer. It is also possible to immerse only one or two of the materials in the developing solution. After about 1 minute the materials are separated from each other. There is obtained a positive image on the thin, intermediate layer.

I claim:

1. A process for the direct production of photographic positive silver images by using a light sensitive silver halide emulsion layer coated on a paper support, a separate nonlight-sensitive water-permeable colloid layer containing a silver halide solvent coated on a support and a separate thin sheet or" a water-permeable material, having a weight of 15-30 grams per square meter which comprises exposing said silver halide layer to an object, developing said exposed silver halide layer by immersing it in an alkaline solution in the presence of a photographic developing substance and bringing one side of the thin sheet of a water-permeable material in close contact with the exposed silver halide layer and the other side with the nonlight-sensitive layer containing a silver halide solvent, so that the exposed part of the emulsion layer is developed to a negative image of the object, whereas part of the non-exposed silver halide layer is dissolved by the silver halide solvent after the latter has difiused from the nonlight-sensitive layer through the thin sheet of water-permeable material to the silver halide layer, and the dissolved silver halide is transferred to the thin sheet of water-permeable material, where it is developed by the developing substance to a positive image of the object, and subsequently separating said light-sensitive layer and said nonlight-sensitive layer from each other.

2. A process according to claim 1, wherein the light sensitive silver halide layer contains a photographic developing substance.

3. A process according to claim 2, wherein the light sensitive silver halide layer contains a mercapto compound.

4. A process according to claim 1, wherein the thin sheet of water-permeable material contains nuclei for development.

References Cited in the file of this patent- UNITED STATES PATENTS 2,500,421 Land Mar. '12, 1950 2,543,181 Land Feb. 27, 1951 2,584,030 Land Jan. 29, 1952 2,635,048 Land Apr. 14, 1953 2,647,056 Land July 28, 1953 OTHER REFERENCES Varden: PSA Journal, vol. 13, September 1947, .pp. 551-554.

Land: The Photographic Journal, vol. 90A, pp. 7-15, January 1950.

Claims

1. A PROCESS FOR THE DIRECT PRODUCTION OF PHOTOGRAPHIC POSITIVE SILVER IMAGE BY USING A LIGHT SENSITIVE SILVER HALIDE EMULSION LAYER COATED ON A PAPER SUPPORT, A SEPARATE NONLIGHT-SENSITIVE WATER-PERMEABLE COLLOID LAYER CONTAINING A SILVER HALIDE SOLVENT COATED ON A SUPPORT AND A SEPARATE THIN SHEET OF A WATER-PERMEABLE MATERIAL HAVING A WEIGHT OF 15-30 GRAMS PER SQUARE METER WHICH COMPRISES EXPOSING SAID SILVER HALIDE LAYER TO AN OBJECT, DEVELOPING SAID EXPOSED SILVER HALIDE LAYER BY IMMERSING IT IN AN ALKALINE SOLUTION IN THE PRESSURE OF A PHOTOGRAPHIC DEVELOPING SUBSTANCE AND BRINGING ONE SIDE OF THE THIN SHEET OF A WATER-PERMEABLE MATERIAL IN CLOSE CONTACT WITH THE EXPOSED SILVER HALIDE LAYER AND THE OTHER SIDE WITH THE NONLIGHT-SENSITIVE LAYER CONTAINING A SILVER HALIDE SOLVENT, SO THAT THE EXPOSED PART OF THE EMULSION LAYER IS DEVELOPED TO A NEGATIVE IMAGE OF THE OBJECT WHEREAS PART OF THE NON-EXPOSED SILVER AFTER THE LATTER DISSOLVED BY THE SILVER HALIDE SOLVENT HALIDE LAYER IS HAS DIFFUSED FROM THE NONLIGHT-SENSITIVE LAYER THROUGH THE THIN SHEET OF WATER-PERMEABLE MATERIAL TO THE SILVER HALIDE LAYER, AND THE DISSOLVED SILVER HALTE IS TRANSFERRED TO THE THIN SHEET OF WATER-PERMEABLE MATERIAL WHERE IT IS DEVELOPED BY THE DEVELOPING SUBSTANCE TO A POSITIVE IMAGE OF THE OBJECT, AND SUBSEQUENTLY SEPARATING SAID LIGHT-SENSITIVE LAYER AND SAID NONLIGHT-SENSITIVE LAYER FROM EACH OTHER.