Title:
PHOTOGRAPHIC DIFFUSION TRANSFER ELEMENT
United States Patent 3853557


Abstract:
A photographic silver salt diffusion transfer element of the integral type having the silver precipitation stratum located above a support and below the light-sensitive silver halide emulsion provided on the element is improved by providing a further silver precipitation layer over the light-sensitive emulsion. Elements provided with this stratum over the emulsion layer which are subjected to processing in equipment provided with rollers which contact the element result in elimination of scoring or marking of the element which may interfere with the transport of exposed elements through the processing apparatus.



Inventors:
FASSBENDER H
Application Number:
05/005565
Publication Date:
12/10/1974
Filing Date:
01/26/1970
Assignee:
EASTMAN KODAK CO,US
Primary Class:
Other Classes:
430/229, 430/230, 430/231, 430/232, 430/244, 430/246
International Classes:
G03C8/06; G03C8/28; (IPC1-7): G03C5/54
Field of Search:
96/76,29
View Patent Images:



Foreign References:
GB874046A
Primary Examiner:
Klein, David
Assistant Examiner:
Goodrow, John L.
Attorney, Agent or Firm:
Byers H. E.
Claims:
I claim

1. A light-sensitive photographic element comprising a support, a first silver precipitating agent on the support, a water soluble light-sensitive silver halide emulsion layer provided over said precipitating agent and being capable of being removed from said element by aqueous washing without removing said first precipitating agent, and a temporary, removable second silver precipitating agent which is water premeable and coated over said emulsion layer, said first silver precipitating agent, said silver halide emulsion layer, and said second precipitating agent all being on the same support.

2. A light-sensitive photographic element according to claim 1 wherein said silver halide emulsion layer comprises silver halide dispersed in a binder which comprises an alkali-soluble acid-insoluble carboxylated cellulose derivative.

3. A light-sensitive photographic element according to claim 2 wherein said binder is selected from the group consisting of dibasic acid half-esters of cellulose ethers, and dibasic acid half-esters of cellulose esters.

4. A light-sensitive photographic element according to claim 3 wherein said binder is a member selected from the group consisting of ethyl cellulose phthalate and cellulose acetate phthalate.

5. A light-sensitive photographic element according to claim 1 wherein said second silver precipitating agent is dispersed in a binder selected from the group consisting of gelatin, hydrophilic synthetic resins, cellulose ethers, and alkali-soluble, acid-insoluble carboxylated cellulose derivatives.

6. A light-sensitive photographic element according to claim 5 wherein the binder of said second silver precipitating agent comprises gelatin.

7. A light-sensitive photographic element according to claim 1 wherein each of said first and second silver precipitating agents is in a gelatin binder, the gelatin binder of said second silver precipitating agent having a lower melting point than the gelatin binder of said first silver precipitating agent.

8. A light-sensitive photographic element according to claim 5 wherein said second silver precipitating agent is a member selected from the group consisting of heavy metals, thiourea, mercaptans, stannous halides, heavy metal salts, and fogged silver halide.

9. In a process of producing an image in the silver precipitating layer of a photographically exposed integral silver halide diffusion transfer photographic element comprising a support, a silver precipitating layer, and a photographically exposed silver halide emulsion layer thereover, wherein the element is advanced through photographic development apparatus by work advancing means to provide a photographic image in said silver precipitating layer, the improvement which comprises utilizing an integral silver halide diffusion transfer photographic element according to claim 1 to reduce the accumulation of deposit on said work advancing means.

10. A method of forming a photographic image which comprises developing a latent image in the emulsion layer of an exposed element of claim 1 with an alkaline silver halide developing solution containing a silver halide developing agent and a silver halide solvent for a time sufficient to form a silver image and an imagewise distribution of a soluble silver complex to diffuse imagewise to said silver precipitating agents and the silver of said portion of silver complex to be precipitated by said agents and removing the emulsion layer and said second agent from said first agent.

Description:
The invention relates to a photographic element of the silver salt diffusion type wherein undeveloped silver halide of an exposed silver halide emulsion layer is transferred as a silver complex imagewise by imbibition to a silver precipitating layer to form a positive silver image thereon. More particularly, the invention relates to such a photographic element of the integral type wherein the emulsion layer and silver precipitating layer are provided on a single support, the precipitating layer being provided on the support below the emulsion layer.

Integral photographic elements including a precipitating layer located below a light-sensitive silver halide emulsion are well known. For example, it is known to provide a multi-layer element such as one carrying on a support two gelatin layers of different solubility, the layer next to the support containing a silver precipitating agent and being harder than the outer gelatin layer which is a gelatin emulsion layer containing silver halide. After exposure of the element, development is carried out with the silver halide solvent-containing developer to obtain a silver positive in the hardened gelatin silver precipitating layer, after which the emulsion layer containing the negative silver image is washed off, leaving the positive silver image on the support. Similar elements are known where the gelatin binder of the emulsion layer is replaced in whole or in part by organic colloid vehicles having a decidedly different solubility than the organic colloid vehicle present in the silver precipitating layer. One of the most satisfactory classes of organic colloids found to be useful in this respect comprise the alkali-soluble, acid-insoluble carboxylated cellulose derivatives disclosed in U.S. Pat. No. 3,020,155, the disclosure of which is herein incorporated by reference. However, irrespective of which type of integral silver halide diffusion transfer element is used, it has been found that in processing such elements in conventional processing equipment which includes rollers for advancing and processing the photographic elements, there is an objectionable deposit built up on the rollers with the passage of time.

It is an object of the present invention to provide a diffusion transfer photographic element of the integral type which can be processed in processing equipment which includes rollers and which substantially reduces the amount of objectionable deposit built up on the rollers. It is a further object of the invention to provide a process for developing photographic images in said elements in equipment which includes work-advancing rollers wherein build-up of deposits on the rollers is minimized to permit operation of the process over longer periods of time. Further objects of the invention will be apparent from the following detailed disclosure.

The silver halide diffusion transfer element to which the invention relates are of the integral type including a support, a silver precipitating layer, and a light-sensitive silver halide layer thereover. These elements are known per se as illustrated by the disclosure of U.S. Pat. No. 3,020,155, mentioned above.

The support may comprise any photographic support such as paper, cellulose ester, synthetic resin, glass, etc., and may be provided with one or more auxiliary layers such as subbing layers. When it is desired to produce a positive (relative to the original subject) image in the silver precipitating layer, the support is preferably opaque and white either by virtue of the support material itself, e.g., paper, or by providing an opaque, white auxiliary layer on a support, such as a transparent synthetic resin film. A transparent support is preferred where the image produced in the silver precipitating layer is a negative with respect to the original subject.

The silver precipitating layer, hereinafter referred to as the "first" silver precipitating layer, provided beneath the light-sensitive silver halide layer, is a water-permeable organic colloid layer containing a silver precipitating agent, that is, an agent capable of yielding with silver ion a dark-colored argental or silver-containing substance, when dissolved silver salts from the emulsion layer come into contact with it. The silver precipitating agent may comprise either physical development nuclei or a chemical precipitant for silver ions.

Suitable silver precipitating agents for use in the silver precipitating layer for forming the argental image include metal sulfides, metal selenides, metal polysulfides, metal polyselenides, thiourea, mercaptans, stannous halides, heavy metals, and heavy metal salts, and fogged silver halide. Heavy metal sulfides such as lead, silver, zinc, antimony, cadmium and bismuth sulfides are useful, particularly the sulfides of lead and zinc alone or in admixture, or complex salts of these with thioacetamide, dithio-oxamide, or dithio-biuret. The heavy metals include silver, gold, platinum, palladium and mercury preferably in the colloidal form. The noble metals are particularly efficacious.

The silver precipitating layer may be applied directly to a support such as paper, or to suitably subbed cellulose derivative supports and synthetic polymer supports from solutions or dispersions of the silver precipitating agents in a colloid vehicle such as gelatin. The colloid vehicle of the silver precipitating layer is insoluble in the solution used for removing the emulsion layer from the element in processing. If gelatin is used, it should be hardened. Hydrophilic cellulose esters and synthetic polymers are useful as a vehicle in the silver precipitating layer insofar as they meet the requirement of having a solubility appreciably different from that of the colloid vehicle of the emulsion layer.

The silver halide emulsion can be applied directly over the silver precipitating layer, but preferably a thin layer comprising the binder of the light-sensitive emulsion layer is first applied followed by the emulsion layer. This thin layer is not absolutely essential; however, it has been found to facilitate the clean removal of the emulsion from the silver precipitating layer.

The silver halide component of the emulsion is not especially critical and can include various silver halides and mixtures of silver halides such as silver bromoiodide, silver chloride or silver bromide optically sensitized in the usual manner. The emulsion may be a developing-out emulsion designed for development to negative images in which case the image obtained in the silver precipitating layer is a positive with respect to the original subject. If desired, the emulsion can be of the direct positive type with the result that the silver image developed in the emulsion is a positive and the image in the silver precipitating layer a negative in respect to the original subject. The procedures of Leermakers, U.S. Pat. No. 2,184,013 and Kendall et al., U.S. Pat. No. 2,541,472 are useful in conferring the direct positive characteristics to the emulsions.

The water-permeable colloid binder of the emulsion layer is one which is appreciably more soluble in water or alkaline solution than the colloid binder of the first silver precipitating layer. Several suitable binders are known such as gelatin either unhardened or substantially less hardened than the gelatin which may be used for the silver precipitating stratum in which case the melting point of the emulsion binder is substantially lower than that of the precipitating layer. Other known binders include hydrophilic, somewhat water soluble synthetic resins such as partially hydrolyzed polyvinyl esters, polyvinyl acetals, polyamides, polyvinyl alcohol, polyvinyl pyrrolidone, non-carboxylated cellulose derivatives such as methyl cellulose, and acid-insoluble alkali-soluble carboxylated cellulose derivatives. The last class of materials, more fully described in U.S. Pat. No. 3,020,155, is the preferred binder by virtue of its ease of removal from the photographic element. The preferred binder for the emulsion layer thus comprises at least a major portion of the cellulose binders disclosed in U.S. Pat. No. 3,020,155. These binders are dibasic half esters of cellulose ethers or cellulose esters. The cellulose ethers and esters are preferably the alkyl ethers and esters and more preferably lower alkyl of one to four carbon atoms. The dibasic acids include aromatic acids, e.g., phthalic, and aliphatic acids either saturated, e.g., succinic, or unsaturated, e.g., maleic.

Representative carboxylated cellulose derivatives are the alkali-soluble acid-insoluble dibasic acid half esters of the cellulose ethyl ethers including the phthalic, succinic, and maleic acid half esters of ethyl celluloses and their ammonium, alkali metal and amine salts, the half esters being made from cellulose ethyl ethers having an alkoxy content of at least 42 percent and the half esters having a dicarboxylic acid radical content of at least 5 percent and preferably at least 20 percent.

The ethyl cellulose phthalates made from cellulose ethyl ethers having at least 42 percent ethoxyl and containing at least 5 and preferably about 20 percent phthalyl are particularly efficacious for use in the emulsion layer. Thus a satisfactory cellulose ether phthalate can be made by the esterification of a cellulose ethyl ether containing 42 percent ethoxy until about 5 to 10 percent phthalation has taken place. A preferred cellulose ether phthalate is thus made from a cellulose ethyl ether containing 45 percent ethoxyl, the final ester containing about 24 percent phthalyl. The ethyl cellulose phthalates employed may vary as to viscosity. In the case of low viscosity esters, such as those whose salts have a viscosity of less than 10 cps. in 4 percent solution in water, it may be desirable to incorporate some plasticizer, such as triacetin or polyethyleneglycol in the ethyl cellulose phthalate cmposition. composition.

The preparation and properties of these ether phthalates and methods for preparing emulsions containing them, suitable for application over the silver precipitating layer of the sensitive elements, is described more fully in the Talbot and mcCleary U.S. Pat. No. 2,725,293, granted Nov. 29, 1955. In addition to the peptizing agents disclosed in the last-mentioned invention for preparing the cellulose ether phthalate emulsions, gelatin is equally useful. Malm et al., U.S. Pat. No. 2,718,667 and Hiatt et al., U.S. Pat. application Ser. No. 272,697, filed Feb. 20, 1952, now U.S. Pat. No. 2,759,925, may also be referred to for a description and synthesis of useful cellulose ether phthalates.

The alkali-soluble acid-insoluble dibasic acid half esters of cellulose esters such as various cellulose acetate phthalates are likewise useful as the emulsion vehicle. A typical cellulose acetate phthalate contains 34 percent phthalyl and 19 percent acetyl. These esters can be made by methods known in the art or as shown in the above Hiatt et al., invention. Similarly, cellulose phthalate containing about 50 percent phthalyl can be used as the major part of the emulsion vehicle.

According to the invention, the build up of objectionable deposits on rollers in equipment used to process the known integral elements described above is substantially reduced by providing a second silver precipitating layer on the element over the silver halide emulsion layer. The second silver precipitating layer comprises a silver precipitating agent of the known type mentioned above dispersed in a water-permeable colloid binder which may be any of the conventional binders mentioned above for use in either the first precipitating layer or in the emulsion layer. It is not required that the binder is water soluble as in the case of the emulsion layer since the presence of a water-permeable layer over the emulsion layer has been found not to substantially interfere with the removal of the emulsion layer by conventional means. The binder thus conveniently and preferably comprises gelatin.

A typical photographic element according to the invention is shown in the drawing which is a greatly enlarged cross-sectional diagrammatic view of a photographic element according to the invention. As shown therein, a representative sensitive element includes: a support 10 such as paper, cellulose ester or synthetic resin, if desired carrying a subbing layer not shown on the support; a silver precipitating layer 11, for example, a gelatin layer containing a colloidal heavy metal or heavy metal sulfide; the emulsion layer 12 containing silver halide grains dispersed in the alkali-soluble acid-insoluble cellulose derivative; and over the emulsion layer a second silver precipitating layer 13 which may be the same as the first layer both in composition and weight.

An element according to the present invention is processed in the usual manner by development with a silver halide developing solution containing a silver halide solvent such as sodium thiosulfate with the result that a silver image is developed in the emulsion layer and shortly thereafter the residual undeveloped silver halide is transformed to a soluble silver complex, a portion of which diffuses imagewise to the first silver precipitating layer where an argental image is formed by reaction of the silver complex with the silver precipitating agent of the silver precipitating layer. The emulsion layer containing the negative silver image is then merely washed from the support with an excess of water to obtain the reproduction wherein the argental positive image is present in the first silver precipitating layer. The second silver precipitating layer is removed with the emulsion layer. In conventional processing equipment, the exposed element is usually transported through a series of processing chambers or sections by work advancing means, such as rollers, which contact the element. In the first chamber or section the exposed element is contacted with a developer solution whereby the desired image is produced in the first precipitating layer. In a subsequent stage or stages the element is washed to remove the overlying emulsion layer and the second precipitating layer, and the element is usually given a final rinse to remove residual chemicals. A typical process involves four stages: development, aqueous spray wash, aqueous soak wash, and final water rinse. In either or both of the washing stages, the element is contacted with water which may be slightly alkaline. The process may also employ a stop bath stage.

The second precipitating layer can be applied directly over the emulsion layer or a thin subbing layer comprising any of the water-permeable colloids mentioned herein may be employed between it and the underlying emulsion layer. The second precipitating layer can be coated by apparatus and with techniques used conventionally to provide silver precipitating layers. The layers may contain generally the same amount of precipitating agent used in the first precipitating layer although the amount can vary widely, provided the layer is not rendered opaque. In general, the amount of precipitating agent will be from 0.8 × 10-6 to 2.0 × 10-6 moles of precipitating agent per square foot. The thickness of the second layer may vary widely and will generally be that which is sufficient to provide a transparent layer having an effective amount of precipitating agent. In general, the layer will have a thickness of from 0.0005 to 0.002 millimeters.

The following examples are included for a further understanding of the invention.

EXAMPLE 1

An integral silver halide diffusion transfer element, containing the following layers in order over a photographic polyethylene-coated paper support: (1) a silver precipitating layer, (2) an organic water-permeable colloid layer, and (3) a silver halide emulsion layer, is prepared as follows: a 10 percent gelatin solution (250 cc) is diluted with 750 cc water. 2.5 cc of 1 N Na2 S are then added to the solution. 250 cc of water containing 2.6 cc of 1 N zinc nitrate are added slowly to the sulfide solution through a jet, resulting in the formation of a colloidal dispersion of zinc sulfide. To this dispersion are added 10 liters of a 3 percent gelatin solution, 300 cc of a 7.6 percent saponin solution and 134 cc of a 10% formaldehyde solution. The mixture is dispersed at 40°C and then coated on a photographic paper support at a coverage of 2 lb. of solution per 100 sq. ft. of coated surface and dried, forming the silver precipitating layer.

Over the silver precipitating layer is coated a 1 percent aqueous solution of the sodium salt (or other alkali metal salt) of cellulose ether phthalate (an ethyl cellulose containing 45.8 percent ethoxyl phthalated to 22.7 percent phthalyl) at a coverage of 0.15 lb. per sq. ft.

To 1 liter of a positive speed, sulfur sensitized high contrast chlorobromide emulsion containing approximately 30 g of gelatin and one mole of silver halide per liter, are added the following ingredients:

30 cc of a 50 percent aqueous solution of glycerine

20 cc of a solution containing 34 gm of salicylaldehyde oxime per liter of MeOH

30 cc of a 7.6 percent saponin solution

12.5 cc of a solution containing 0.2 gm of 1-carboxymethyl-5-[(3-ethyl-2(3)-benzoxazolylidene)ethylidene]-3-phenyl-2- thiohydantoin in 30 cc of MeOH + 1 drop of triethylamine

To the above mixture are added 4 liters of a 4 percent solution of the ammonium salt of the cellulose ether phthalate just mentioned and 2 gm of 3-methylbenzothiazoline-2-thione dissolved in methyl alcohol. The mass is stirred at 30°C, thoroughly dispersed and then coated over the sodium salt of cellulose ether phthalate interlayer at a coverage of 600 sq. ft. per mole of silver halide and dried in the conventional manner. After exposure, several elements are processed in Itek Positive Process equipment which includes several work-advancing rollers to transport the print through developing, spray wash, soak wash and final rinse sections of the apparatus. The developer employed is the following:

ethylene diamine tetraacetic acid, 1.0 gm/l tetra sodium salt hydroquinone 10.0 gm/l 1-phenyl-3-pyrazolidone 0.8 gm/l sodium sulfite 50.0 gm/l sodium thiosulfate 5H2 O 20.0 gm/l trisodium phosphate 12H2 O 100.0 gm/l potassium bromide 0.5 gm/l potassium chloride 16.0 gm/l boric anhydride 0.4 gm/l (packaging ingredient) 2-β-phenethyl isoquinolinium bromide 0.25 gm/l pH 11.2

Other suitable developers are described in Bloom and Pomeroy U.S. Pat. No. 3,062,643. After 500 prints are processed in this manner, a noticeable deposit is built up on the rollers in the device and it is necessary to shut down the process in order to replace the rollers. It is quite difficult and time consuming to remove the deposit from the dirty rollers, an overnight soaking being ordinarily required. The following example illustrates that the deposit is substantially reduced by the present invention.

Example 2

A plurality of integral photographic diffusion transfer element are made as in Example 1 except that a second silver precipitating layer is coated over the silver halide emulsion layer. The second precipitating layer is provided from a coating solution which is the same as that used to coat the first layer, and coated at equal weight. The elements are then exposed and processed as in Example 1. After 1,600 prints are processed in the device, the process is interrupted and the rollers inspected. A small deposit is observed on the rollers which deposit amounts to substantially less than that of Example 1.

Examples 3 and 4

Elements similar to that of Example 2 are prepared except that the coating weight of the second layer is 75 percent of the first precipitating layer in Example 3 and 137 1/2 percent in Example 4. Results are similar to that of Example 2.

While the present invention results in a substantially reduced deposit during processing, the processing is otherwise not adversely affected. That is, the element can be exposed and processed in the usual manner in conventional apparatus such as the Itek equipment mentioned.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention.