US3666460A - Diffusion transfer article and process using humectant in emulsion layer - Google Patents

Abstract

PHOTOGRAPHIC PRODUCTS FOR USE IN DIFFUSION TRANSFER PROCESSES INCLUDING A LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER AND WHEREIN THE EMULSION LAYER FURTHER INCLUDES A PHOTOGRAPHICALLY INNOCUOUS HUMCCTANT IN AN AMOUNT SUFFICIENT TO LOWER MATERIALLY THE PROCESSING TIME FOR FORMING THE TRANSFER IMAGE.

Description

United States Patent Oflice 3,666,460 Patented May 30, 1972 3,666,460 DIFFUSION TRANSFER ARTICLE AND PROCESS USING HUMECTANT IN EMULSION LAYER Leonard C. Farney, Melrose, Mass., assignor to Polaroid Corporation, Cambridge, Mass. No Drawing. Filed Jan. 11, 1966, Ser. No. 526,673 Int. Cl. G03c 5/54 US. Cl. 96-29 14 Claims ABSTRACT OF THE DISCLOSURE Photographic products for use in diffusion transfer proceses including a light-sensitive silver halide emulsion layer and wherein the emulsion layer further includes a photographically innocuous humectant in an amount sufficient to lower materially the processing time for forming the transfer image.

This invention relates to photography and, more particularly, to novel products and processes for preparing visible images by diffusion transfer.

A primary object of this invention is to provide novel photographic emulsions and film units containing the same.

Another object is to provide a novel diffusion transfer process for preparing silver images wherein the processing time and/or the amount of processing composition necessary to provide a silver transfer image of a given desired density is materially lowered.

Still another object is to provide novel photographic products and processes for preparing a transfer image in a layer above the photographic emulsion, which image need not be separated from the emulsion subsequent to processing in order to be viewed.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the fol: lowing detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

It has herefore been known to incorporate plasticizers in photographic emulsion layers to prevent curling and/ or the tendency of the emulsion layer to crack when it is flexed, especially at low humidities.

It has now been found, quite surprisingly, that the presence in the photographic emulsion layer of an effective amount of a photographically innocuous humectant materially lowers the processing time and/or the amount of processing composition necessary to form a silver image by diffusion transfer. This is apparently, at least in part, due to the ability of the humectant to retain water in the emulsion matrix, e.g., in the gelatino matrix of a gelatino silver halide emulsion, which in turn minimizes shrinkage, or stated another way, minimizes the swelling necessary for processing, thus lowering the induction time and/or the time required for the soluble silver complex to transfer to the layer or stratum where the silver transfer image is formed. In addition, under given processing conditions it is possible to obtain a silver transfer image having a desired density with less sliver in the photosensitive emulsion.

As used herein and in the appended claims, the term photographically innocuous humectant denotes a humectant which is not harmful or which does not hinder the photographic process, i.e., does not adversely affect the light-sensitive emulsion or the processing of a developable image produced 'by photoexposure thereof.

As examples of suitable photographically innocuous humectants contemplated by the present invention, mention may be made of water-soluble polyhydroxy com pounds such as a-methyl glucoside, glycerine, etc. The amount of humectant needed will vary according to the structure and character of the film unit and the developing composition employed as Well as the processing conditions. Generally, at least 25% of humectant based upon the weight of gelatin in the emulsion and preferably at least 40% should be employed for optimum results. Particularly good results have been obtained when the percentage of humectant is or more. In any event, the selection of the particular amount of humectant to be employed will be readily apparent to those skilled in the art in view of the present disclosure. Accordingly, as used herein and in the appended claims the term effective amount denotes the amount of humectant necessary to obtain the desired results, e.g., the amount of humectant necessary to obtain the desired lowering of processing time and/or amount of processing composition necessary.

The present invention is particularly useful in photographic systems such as are described and claimed in the copending application of Edwin H. Land, Ser. No. 519,- 995 filed concurrently as a continuation-in-part of application Ser. No. 368,622 filed May '19, 1964, both of which are now abandoned, and the copending application of Edwin H. Land and Leonard C. Farney, Ser. No. 519,- 884 filed concurrently as a continuation-in-part of application Ser. No. 368,621 filed May 19, 1964, both of which are now abandoned.

As is disclosed in these applications, a photographic film assembly including a layer containing a light opacityproviding material may be exposed to a light source on the same side of the support for the film assembly as the layer of opacity-providing material and then processed to form a negative image and a positive transfer image in a stratum situated above the layer of opacity-providing material. This opacity-providing material is present in an amount sufficient to mask effectively the negative image but not sufficient to preclude photoexposure of the light-sensitive material in the-film assembly, so that there is formed a composite print which contains both a negative and a positive image but which is viewable by reflection as a positive reproduction of the original subject matter. The opacity-providing material, which is preferably white or substantially colorless, further serves to provide the background for the positive image.

In application Ser. No. 519,995 the layer of opacity providing material is situated over a layer containing a light-sensitive silver halide emulsion; while in application Ser. No. 519,884 the opacity-providing material is situated in same layer as the light-sensitive silver halide emulsion and a second or additional layer of opacity-providing material may also be provided over the layer containing the silver halide emulsion.

Any of the aforementioned film asemblies may contain an outer layer comprising a silver receptive Stratum, i.e., a stratum containing at least one silver precipitating agent, or the silver precipitating agent may be present initially in the processing composition. 7

The following examples show by way of illustration and not by way of limitation the use of this invention in photo graphic systems such as described and claimed in the aforementioned two copending patent applications.

EXAMPLE I A first film unit was prepared by coating on a paper base support a light-sensitive silver halide emulsion layer containing 0.071 gm. of silver and 0.61 gm. of gelatin per sq.

ft. of surface area. Over this light-sensitive layer was then applied a layer of opacifying material containing 0.45 gm. of titanium dioxide and 0.045 gm. of gelatin per sq. ft. On top of this was coated a silver receptive stratum containing 0.001 gm. per. sq. ft. of lead sulfide and 0.11 gm. per sq. ft. of gelatin. A second film unit was prepared which was substantially identical to the cfirst film unit except that the light-sensitive layer also contained 0.25 gm. of tit-methyl glucoside per sq. ft. of surface area.

The above film units were exposed and developed in exactly the same manner, namely by exposing each film unit to the same subject matter for one second and then running the thus-exposed film unit through a bath containing the following processing composition:

Water8400.0 cc.

Sodium hydroxide96.0 gm.

Sodium sulfite-255.0 gm.

Potassium thiosulfate-147.0 gm. 4-amino-2,6-dimethylphenol90.0 gm. Phenylmercaptotetrazole-0.09 gm.

The exposed film units were immersed in the bath for about one second followed by an additional twenty seconds dark time. The silver image obtained from the first film unit (the one with no humectant) had a D of 0.40 while the silver image obtained from the second film unit had a D of 1.25, thus demonstrating the materially greater D obtained at short bath times by having a humectant present in the light-sensitive layer.

EXAMPLE II Example I was repeated, except that the exposed film units were immersed in the processing bath approximately three times as long. The first film unit provided an image having a D of 1.40 (in contrast to the 0.40 obtained in Example I) while the second film unit containing the humectant provided a image having a D,,,,,,, of 1.08.

From Example II it will be observed that the film unit with no humectant was immersed in the processing bath approximately three times as long as the film unit with the humectant of Example I in order to obtain a positive image having a comparable D thus demonstrating how the presence of the humectant materially lowers the processing time required to obtain a positive image of a given D This shorter processing time is of particular significance in document duplication systems employing the present invention.

The following additional examples are further illustra tive of the film units contemplated by this invention.

EXAMPLE HI On a paper base support was coated a light-sensitive emulsion layer containing per sq. ft. of surface area 0.0059 gm. of silver, 0.22 gm. of gelatin, 1.72 gm. of titanium dioxide, 0.24 gm. of Cab-O-lSil (trademark of Godfrey L. Cabot, Inc. for a fire-dry 99% pure fumed silica with a particle size of 0.015 micron, surface area of 200 mP/gm. bulk density of 2.3 lb./cu. ft.) and 0.053 gm. tit-methyl glucoside. On top of this was coated a silver-receptive stratum containing 0.001 gm. per sq. ft. of lead sulfide and 0.22 gm. per sq. ft. of gelatin. The exposure and development in the manner described in Example I provided a positive silver reproduction of excellent density and contrast.

EXAMPLE IV Example III was repeated, substituting for the lightsensitive emulsion layer, a layer containing per sq. ft. of surface area 0.0065 gm. of silver, 0.25 gm. of gelatin, 1.44 gm. of titanium dioxide, 0.20 gm. of Cab-06H and 0.l2 gm. of tx-mfifl'lyl glucoside. A comparable positive silver reproduction was obtained.

4 EXAMPLE v On a paper base support was coated a light-sensitive silver halide emulsion layer containing per sq. ft. of surface area 0.05 gm. of silver, 0.39 gm. of gelatin, 2.00 gm. of titanium dioxide and 0.34 gm. of a-methyl glucoside. Over this light-sensitive layer was then applied a layer of opacifying material containing per sq. ft. of surface area 1.01 gm. of titanium dioxide and 0.055 gm. of gelatin. On top of this was coated a silver-receptive stratum similar to that described in Example 1. Exposure and development in the manner described in Example I provided an excellent positive silver reproduction.

EXAMPLE VI On a paper base support was coated a light-sensitive silver halide emulsion layer containing per sq. ft. of surface area 0.050 gm. of silver, 2.00 gm. of titanium dioxide, 0.213 gm. of gelatin and 0.34 gm. of tl-mfithyl glucoside. Over this light-sensitive layer was then applied a layer of opacifying material containing per sq. ft. of surface area 0.86 gm. of titanium dioxide and 0.043 gm. of gelatin. On top of this was coated a silver-receptive stratum as in Example V. Exposure and development in the foregoing manner provided a positive silver reproduction comparable to that obtained in Example V.

While the present invention may be employed in diffusion transfer processes for preparing silver images generally, from the foregoing illustrative examples it will be appreciated that the present invention is particularly useful in photographic products and processes for preparing composite prints viewable by reflected light as a positive reproduction, such as are described and claimed in the aforementioned copending applications, Ser. No. 519,995 and Ser. No. 519,884 filed concurrently. In this respect, the present invention may be employed in the preparation of composite prints in conjunction with the electrolytic development techniques described and claimed in the copending application of Edwin H. Land, Ser. No. 519,885 now US. Pat. No. 3,362,823 and Ronald F. Cieciuch, Ser. No. 519,886 and now US. Pat. No. 3,549,363, both filed currently.

Since certain changes may be made in the aboce process and product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic product for forming a composite pr nt which a positive image is formed over a negative image, said composite print being viewable as a positive reflection print without separation of said two images, said product comprising a support substantially opaque to visible light and having thereon a first layer containing a light-sensitive silver halide emulsion and a second layer situated above said first layer and containing a light opacity-providing material in an amount sufficient for masking elfectively a negative image formed by exposing said photographic product and deyeloping said exposed product to form said negative image in said first layer and a positive image in a stratum on said second layer, the amount of said material being insufficient to preclude photo-exposure of said silver halide from a light source on the same side of said support as said two layers, said material further providing a background for viewing said composite print by refiected light as a positive image; the improvement which comprises including in said first layer a photographically innocuous humectant in an amount sufiicient to lower materially the processing time for forming said transfer image.

2. A photographic product as defined in claim 1 wherein said humectant comprises a-methyl-glucoside.

3. A photographic product as defined in claim 1 whercin said emulsion comprises a gelatino silver halide emulsion and at least 25% of humectant based upon the weight of gelatin in said emulsion is present in said layer.

4. In a photographic product for forming a composite print in which a positive image is formed in a stratum over a negative image, said composite print being viewable without separation of said two images as a positive reflection print, said product comprising a support having thereon a layer containing a light-sensitive silver halide emulsion, said layer further including a light opacityproviding material in an amount sufficient for masking effectively a silver image formed in said layer by exposing said photographic product and developing said exposed product to form said negative image in said layer and a positive transfer image in a stratum above said layer containing said negative image, the amount of said material being insufficient to preclude photoexposure of said silver halide from a visible light source on the same side of said support as said layer, said material further providing a background for viewing said composite print by refiected light as a positive image; the improvement which comprises including in said layer a photographically innocuous humectant in an amount sufficient to lower materially the processing time for forming said transfer image.

5. A photographic product as defined in claim 4 wherein said humectant comprises a-methyl-glucoside.

6. A photographic product as defined in claim 4 wherein said emulsion comprises a gelatino silver halide emulsion and at least 25% of humectant based upon the weight of gelatin in said emulsion is present in said layer.

7. In a photographic product for forming a composite print in a stratum over a negative image, said composite print being viewable as a positive reflection print without separation of said two images, said product comprising a support having thereon a first layer containing a lightsensitive silver halide emulsion and a light opacity-providing material, and a second layer situated above said first layer and containing a light opacity-providing material, said material in said two layers being present in an amount sufiicient for masking efiectively a silver image formed in said first layer by exposing said photographic product and developing said exposed product to form said negative image in said first iayer and a positive transfer image in a stratum above said second layer, the amount of said material being insufficient to preclude photoexposure of said silver halide from a visible light source on the same side of said support as said two layers, said material further providing a background for viewing said composite print by reflected light as a positive image; the improvement which comprises including in said first layer a photographically innocuous humectant in an amount suflicient to lower materially the processing time for forming said transfer image.

8. A photographic product as defined in claim 7 wherein said humectant comprises u-methyl-glucoside.

9. A photographic product as defined in claim 7 wherein said emulsion comprises a gelatino silver halide emulsion and at least 25 of humectant based upon the weight of gelatin in said emulsion is present in said layer.

10. A photographic process wherein a layer containing a light-sensitive silver halide emulsion is exposed through a layer of light opacity-providing material positioned thereover to form a developable image and said exposed emulsion layer is contacted with an aquous alkaline developing composition to form a negative image in said light-sensitive layer and an imagewise distribution of soluble silver complex in terms of unexposed areas of said emulsion is transferred to a stratum above said layer of said material wherein it is reduced to image silver to form a positive transfer image, said layer of said material being present in an amount sufiicient for masking effectively said negative image while at the same time providing a background for said positive image thereover, thereby providing a composite print viewable by reflected light as apositive image; the step which comprises incorporating a photographically innocuous humectant in said layer in an amount sufiicient to lower the processing time for forming said transfer image.

11. A process as defined in claim 10 wherein said emulsion comprises a gelatino silver halide emulsion and the amount of said humectant incorporated in said emulsion layer is at least 25% by weight of the gelatin in said layer.

12. A process as defined in claim 10 wherein said humectant comprises a-methyl-glucoside.

13. In a photographic process wherein a layer containing a light-sensitive silver halide emulsion and a light opacity-providing material is exposed to form a develop able image and said exposed layer is contacted with an aqueous alkaline developing composition to form a negative image in said layer and an imagewise distribution of soluble silver complex in terms of unexposed areas of said emulsion which is transferred to a stratum above said layer where it is reduced to image silver to form a positive transfer image, said material being present in an amount sufficient for masking effectively said negative image while at the same time providing a background for said positive image thereover, thereby providing a composite print viewable by reflected light as a positive image; the step which comprises incorporating a photo graphically innocuous humectant in said layer in an amount sufficient to lower the processing time for forming said transfer image.

14. A process as defined in claim 13 wherein said emulsion comprises a gelatino silver halide emulsion and the amount of said humectant incorporated in said emulsion layer is at least 25% by weight of the gelatin in said layer.

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