Photographic Diffusion Transfer Product And Process

Abstract

A receiving layer for use in the photographic diffusion transfer process comprises finely divided nonsilver noble metal nuclei obtained by reducing a metal salt in the presence of a colloid with a reducing agent having a standard potential more negative than -0.30. The nuclei typically have an average particle size in the range of about 15 A. to about 65 A., at least 80 percent, by number, of the nuclei having a particle size in the range of about 20 A. to about 50 A. The receiving layers can be on a support such as paper or film base.

Description

BACKGROUND OF THE INVENTION

This invention relates to the preparation of nonsilver noble metal nuclei and their use in diffusion transfer products and processes.

Diffusion transfer processes are well known. For example, Rott, U.S. Pat. No. 2,352,014 describes such a process wherein undeveloped silver halide of an exposed photographic emulsion layer is transferred as a silver complex imagewise by imbibition to a silver precipitating or nucleating layer, generally to form a positive image therein. The silver precipitating or nucleating layer generally comprises a binder containing nuclei such as nickel sulfide, colloidal metal or the like. It is known that the particular nuclei play an extremely important role in determining the nature of the silver image which is formed in the receiving layer. For instance, depending upon the particular nuclei employed, the image formed may have inadequate density, may not have a neutral tone, i.e., may have a brownish or yellow color, may lack stability, etc.

Many of the nuclei which have been found suitable from the standpoint of tone and/or density have had to be prepared fresh prior to coating, since they have often had poor stability on standing. For instance, when a dispersion of the nuclei is permitted to stand, the dispersion appears to lose density, probably due to a bleaching effect so that the nuclei are no longer of practical use. In addition, with many nuclei it is difficult to obtain a satisfactory tone even with a conventional toning agent, particularly when gelatin is used in the binder. Moreover, many nuclei do not provide a desirable density in the positive image.

Silver nuclei have long been considered particularly suitable for use in diffusion transfer processes, except for the detrimental yellow color generally associated with their use. Since the image obtained in the receiving sheet is usually composed of silver deposited on a suitable site, it appeared that use of silver nuclei would facilitate the deposition of the silver on these nuclei and result in a particularly good dense image. In addition, evidence points to the importance of the shape and size of the grains which are formed by depositing the silver on the nucleating sites, and it appeared likely that silver nuclei would encourage the formation of desirable grain sizes and grain shapes.

Carey Lea silver, a colloidal silver, can be used as nuclei in diffusion transfer processes. According to the Carey Lea method of preparing colloidal silver, silver nitrate is reduced in a solution of dextrin and sodium hydroxide at a pH of about 13.3. The average particle size is about 150 A. However, the average particle size can be reduced to about 50-70 A. by modifying the Carey Lea process to adjust the pH to a lower level in order to lower the reduction rate after which the reaction is quenched with a strong acid solution. Wiegel, Zeit. Wiss Photo. 24 316ff (1926) describes a modified Carey Lea process. Unfortunately, the yellow color of Carey Lea silver results in a yellow minimum density when it is used as nuclei in a receiving layer. Moreover, colloidal silver has not been found to provide an entirely satisfactory nuclei for many reasons other than the yellow color, such as failure to provide an image which can be suitably toned, an image which does not have satisfactory density and the like. Accordingly, there has been a need for nuclei which are more satisfactory for use in the diffusion transfer process than those that are known in the prior art.

Some of the aforementioned problems have been recognized in the art and various attempts have been made to overcome them, as can be seen by McGuckin, U.S. Pat. No. 3,345,169 which describes the treatment of silver precipitating nuclei such as colloidal silver with a noble metal in the ionic form. This treatment permits toning of the image formed in the diffusion transfer process when Carey Lea silver has been treated using this method.

Noble metal nuclei of metals such as palladium, platinum, gold, etc., are also known in the prior art. Particle sizes of the nuclei often range from at least 300 A. up to 2,500 A., the larger particle sizes requiring a greater concentration per square foot when coated on a receiving support. In many instances, there is a definite lack of uniformity among the particle sizes. Although the average particle size might be 500 A. for instance, there might be many of the very large sizes as well as some very small to result in a particular average size. However, nonsilver noble metal nuclei known in the art generally have not provided the desired improved properties over silver nuclei.

It is recognized that nuclei which would provide improved density of a positive image, which would be easy to tone and which would also behave satisfactorily when used either in a binder containing gelatin or in a polymeric binder would be very useful in diffusion transfer processes. It is also recognized that it would be desirable to obtain nuclei which can be coated at a relatively low concentration on a support and which would provide a surface which is relatively colorless or water white in nonimage areas of a positive. Such desirable results can be achieved by the practice of this invention.

SUMMARY OF THE INVENTION

In accordance with this invention, it has been found that nonsilver noble metal nuclei, as described herein, can be used in diffusion transfer processes to overcome several of the disadvantages described hereinbefore. The nonsilver noble metal nuclei of this invention are characterized by a small and uniform particle size. Their use in diffusion transfer materials and processes gives several advantages, including a significant increase in density and tone of a positive image, in comparison to the use of prior art nuclei which do not exhibit such particle size characteristics.

Non-silver noble metal nuclei having the desired size and distribution can be prepared by reducing a nonsilver noble metal salt, in the presence of a colloid, with a reducing agent having a standard potential more negative than -0.30, e.g., a borohydride or hypophosphite, as described herein. Due to the small size of the nuclei, their particle size and distribution are difficult to measure. However, careful analysis indicates that the nuclei employed in the practice of this invention have an average particle size in the range of about 15 A. to about 65 A., preferably about 30 A. to about 60 A., at least 80 percent, by number, of said particles having an average particle size in the range of about 20 A., to about 50 A., preferably about 25 A. to about 40 A.

Particularly useful nuclei are those of the noble metals, platinum, palladium, gold, mercury, rhodium, ruthenium and osmium. Preferred nuclei are those of palladium and platinum, in that order. These two metals provide the greatest density in the positive image and also have a low background density or minimum density (Dmin). Palladium, in particular, provides a very low minimum density. Gold, on the other hand, does not provide as high a maximum density (Dmax) and provides a relatively high minimum density. Mixtures can be used.

Particularly useful reducing agents which can be used in preparing nuclei according to this invention include borohydrides, such as alkali (e.g., sodium, potassium, ammonium, etc.) borohydrides which have a standard potential of -1.24 measured at 25.degree. C., and hypophosphites (H.sub.2 PO.sub.2 .sup.-) such as hypophosphorous acid (H.sub.3 PO.sub. 2) which has a standard potential (E.degree.) of -0.50 measured at 25.degree. C. See W. M. Latimer, "The Oxidation States of the Elements and Their Potentials in Aqueous Solution," 2nd Edition, Prentice Hall, Inc., New York, 1952. The E.degree. values are in keeping with the IUPAC convention as to sign. Preferred borohydrides for use in the invention are the alkali metal borohydrides and more particularly sodium or potassium borohydride.

Water-soluble amine-boranes having the following structure are also useful reducing agents:

wherein, within the limitation that the amine-borane is stable in aqueous solution, the groups R.sub.1 and R.sub.2 separately represent hydrogen atoms or alkyl, aryl or aralkyl groups and R.sub.3 represents an alkyl, cycloalkyl, aryl or aralkyl group or R.sub.1 and R.sub.2 constitute with the nitrogen atom a heterocycle and R.sub.3 is then a hydrogen atom.

Referring to the foregoing formula, examples of alkyl groups are methyl, ethyl, propyl and isopropyl, an example of cycloalkyl is cyclohexyl, examples of aryl are phenyl and naphthyl which can be optionally substituted, an example of an aralkyl group is benzyl and examples of nitrogen heterocyclic groups are pyridyl, morpholino and piperazyl. Specific compounds of the class are trimethylamine borane, dimethylamine borane, pyridine borane, cyclohexylamine borane, morpholine borane or piperazine borane. Methods for the production of such boranes are described in articles by Burg et al., J.A.C.S. 59, 1937, 785-787 and Taylor et al., J.A.C.S. 77, 1955, 1506. In general terms, the compounds may be prepared by reacting sodium borohydride, NaBH.sub.4, with a hydrochloride salt of an amine of the formula R.sub.1 R.sub.2 R.sub.3 N.

In a modification of the invention, there may be used, instead of an amine-borane, a precursor for an amine-borane as referred to above. Generally, it is preferred to carry out the reduction reaction using gelatin as the colloid, though other protective colloids, e.g., polyvinyl pyrrolidone, may also be employed.

According to the invention, a receiving layer for use in the diffusion transfer process can comprise the entire reaction product obtained by precipitating finely divided nonsilver noble metal nuclei from a salt of the metal by reducing the metal salt, in the presence of a colloid, to metal nuclei using a reducing agent having a standard potential more negative than -0.30. Particularly useful nuclei are those prepared from noble metal salts such as palladium, platinum, and gold salts, and especially preferred nuclei are those of palladium and platinum. The receiving element is prepared by reducing the metal salt as described above and coating the reaction product on a suitable support. In a particularly advantageous embodiment, the nuclei are coated at about 1 to about 200 .mu.g./ft..sup.2.

The receiving element as described above is used advantageously to provide a photographic print having an image in the receiving layer on a support. The image is obtained by the diffusion transfer process and is formed in the receiving layer which comprises a colloid binder and the nonsilver noble metal nuclei of our invention. Particularly good results are obtained using palladium and platinum nuclei.

DESCRIPTION OF PREFERRED EMBODIMENTS

In one embodiment of this invention, palladium nuclei are prepared by reducing a palladium salt such as ammonium chloropallidate in an aqueous solution containing a colloid, such as gelatin, preferably using a borohydride reducing agent such as potassium borohydride. Advantageously, the reducing agent is used slightly in excess and the reaction mixture heated to about 70.degree. C for about 5 minutes. Additional colloid and other addenda can then be added and the mixture coated on a suitable support such as baryta coated paper. In a particularly useful embodiment, 14 micrograms of palladium nuclei in 80 milligrams of gelatin is coated per square foot of support.

In one example of the utility of this nucleated layer on a support, the nucleated layer having the nonsilver noble metal nuclei thereon, is overcoated with a substantially unhardened silver halide emulsion. Particularly useful emulsions are described in Yackel et al., U.S. Pat. No. 3,020,155. After exposure, the emulsion is developed with a silver halide diffusion transfer type developing solution containing a silver halide developer such as hydroquinone and also containing a silver halide complexing agent such as sodium thiosulfate. The undeveloped silver halide, complexed with the thiosulfate, diffuses to the nucleated underlayer where an image is formed which is positive with respect to the negative image formed in the silver halide emulsion. The unhardened silver halide emulsion is then removed by washing with warm water.

As indicated above, the nuclei of this invention are prepared in a suitable colloid suspension. In a particularly useful embodiment, a hydrophilic colloid is used such as gelatin. However, any suitable colloid or colloids may be used, including both water-soluble polymers and water-insoluble polymers. A latex or hydrosol may advantageously be employed if the polymer is insoluble in the liquid used to carry out the reduction. The amount of colloid can be varied depending upon the particular colloid, reducing agent, ratio of proportions, etc. Typically about 0.5 percent to about 20 percent, by weight, based on the total reaction mixture of colloid is used, preferably from about 1 percent to about 10 percent.

Usually a water-soluble metal salt is used which is dissolved in water which either contains a colloid or to which the colloid is added. The borohydride reducing agent is then added to the solution, usually at a pH of about 6 until the pH reaches about 8.5, typically at temperatures of 0.degree.-95.degree. C., preferably 20.degree.-70.degree. C. The time allowed for the reaction to be completed depends upon the reducing agent, colloid, metal salt used, temperature, etc. Usually from 3 minutes to about 2 hours are sufficient, but greater or less time may be adequate. The reaction mixture can then be coated directly on an appropriate support for use as a receiving sheet in the diffusion transfer process or additional colloid can be added to the reaction mixture before coating.

It will be appreciated that more than one type of colloid can be incorporated in the coating composition. Any suitable colloid may be used. Particularly useful colloids are those which are used for binders in silver halide emulsions. Advantageously, they are coated in a range of about 5-500 mg./ft..sup.2. Included among the suitable colloids are gelatin, preferably coated at a level in the range of about 7-100 mg./ft..sup. 2, polymeric latices such as copoly(2-chloroethyl methacrylate-acrylic acid) preferably coated in the range of 15-350 mg./ft..sup.2 and a polymeric vehicle containing two components (1) polyvinyl alcohol, and (2) interpolymer of n-butyl acrylate, 3-acryloyloxypropane-1sulfonic acid, sodium salt and 2-acetoacetoxyethyl methacrylate, in a preferred range of about 10-300 mg./ft..sup.2.

As pointed out above, various colloids may be used as dispersing agents or as binders for the nuclei of our invention. The use of these various colloid materials results in varying the aspects of the process such as the time of contact between the negative and the receiver sheet, the speed of transfer, the tone and the like. Whereas various latex materials are suitable for use as vehicles for nuclei, it will be appreciated that some latex formulations are also difficult to successfully coat with consistently good results, especially without mottle.

Coating solutions containing polymers are also useful. A particularly useful polymer coating solution which has a viscosity resembling gelatin solutions and can be hardened with an aldehyde comprises polyvinyl quaternary salts containing aldehyde hardenable groups. Also, in addition to various colloids, toners, surfactants, coating aids, developing agents, stripping agents, silver halide solvents etc., may be added to improve the image quality in the receiving sheet.

Due to the unexpectedly high activity of the nuclei of the invention, the concentration on the receiving sheet can be very low, suitable concentrations being about 1 to about 200 .mu.g./ft..sup.2, preferably 6 to 100 .mu.g./ft..sup.2. The size of the particles of the nuclei can be determined using an electron microscope. In a convenient method of preparing the nuclei for examination, discrete nuclei are prepared in a suitable colloid, such as a latex, after which the latex is placed on a suitable support for viewing using an electron microscope. The size of the particles can then be measured from a micrograph of the viewed dispersion.

It will be greatly appreciated from the above, that the coating composition generally contains not only nuclei but also reaction products which are obtained from reducing the metal salt. Accordingly, it is within the scope of the invention to include in the receiving layer, nuclei having the specified size and specified size distribution, plus the reaction byproducts which are obtained during the reducing operation.

The supports which can be used for coating with the receiving layer are any of those which are suitable and include paper, wood, glass, plastics, etc. A particularly useful support is baryta coated paper. However, in a preferred embodiment, a polymeric material which acts as a moisture barrier, such as polyethylene or the like, which is pigmented to provide a white surface is used. Other polymeric materials which may be used as coatings on paper or as self-supported webs include polyesters, polyamides, polycarbonates, polyolefins, cellulose esters, polyacetals and the like.

In order to obtain adhesion or to improve adhesion to a receiving support, treatments of the support, e.g., photographic film base, may be carried out including subbing the support, electron bombardment, treating with peroxide and the like.

In one embodiment, the nuclei can be coated in a polyethylene latex. For instance, polyethylene latex may be used as a dispersing medium when the nuclei are formed or the polyethylene latex may be added to the reaction mixture after the nuclei have been formed in the presence of some other colloid. It will be appreciated that a polyethylene latex may also be used with other nucleating or silver precipitating materials, including metal sulfides and the like.

The nuclei may be formed in situ by coating a layer of non-silver noble metal salt in a colloid on a support and overcoating with a layer of reducing agent. For instance, a coating containing gelatin and gold chloride may be coated on a suitable support over which is then coated a layer containing sodium borohydride. However, improved results are obtained by carrying out the reduction in a reaction vessel and then coating on a suitable support.

As pointed out previously, the receiving sheet may also contain various toning agents or these toning agents may be in the processing solution or even, in some instances, contained in the silver halide emulsion. Toning agents which may be included for improving the image include sulfur compounds such as 2-mercaptothiazoline, 2-amino-5-mercapto-1,3,4-thiadiazole, 2-thionoimidazolidene, 2-mercapto-5-methyloxazoline and 2-thionoimidazolyne. These toners are particularly useful in a range of 0.01 to 3.0 mg./ft..sup.2 either in the receiving layer or coated in a layer on top of the nucleated layer. It will be appreciated that these toners can be used either alone or in conjunction with other toning agents. Other toning agents which may be used include the 5-mercaptotetrazoles of Abbott et al., U.S. Pat. No. 3,295,971 and Weyde, U.S. Pat. No. 2,699,393. Still other toning agents are disclosed in Tregillus et al., U.S. Pat. No. 3,017,270.

It has been found that the use of a 5-mercaptotetrazole such as 1-phenyl-5-mercaptotetrazole as a toning agent in diffusion transfer processes results in a restraining effect, prolonging the transfer time. This can be prevented by the use of an alkali metal iodide such as, for example, potassium iodide, in the processing solution, particularly the activator solution, without loss of the blue-black toning effect obtained by using a 5-mercaptotetrazole.

The nuclei of the invention may also be precipitated in colloidal dispersions which also have therein particles such as silica, bentonite, diatomaceous earth such as Kieselguhr, powdered glass and fuller's earth. In addition, colloids and colloidal particles of metal oxides such as titanium dioxide, colloidal alumina, coarse aluminum oxide, zirconium oxide and the like may be used with the nuclei.

In one method of carrying out the diffusion transfer process, the exposed silver halide emulsion is contacted against a web in which has been imbibed some or all of the processing solutions. The processing solutions and other components of the web and/or the emulsion can be adjusted so that either a useable negative is obtained in the emulsion layer or a useable positive in the web, or both a useable negative and a useable positive.

In any event, the web is nucleated with silver precipitating nuclei. I have found that the nuclei of the invention are especially suitable for use in the web processing system. In a particularly useful embodiment, the web comprises a support carrying a layer of gelatin which contains nuclei such as those described in this application. The web is soaked with a desired processing solution prior to use and then placed in close contact with an exposed negative for a time which depends upon the particular components used. The two films are then separated, revealing a positive image in the web material. If desired, a cover sheet may be applied over the negative or processing web after they have been separated for ease of handling or to improve stability of the images therein. Typical processing webs and processes of using processing webs are disclosed in U.S. Pat. No. 3,179,517 issued Apr. 20, 1965 to Tregillus et al.

In carrying out the diffusion transfer process, conventionally the silver halide emulsion is exposed to a light image after which it is contacted with a silver halide developing agent containing a silver halide complexing agent. The exposed emulsion is developed in the light areas and the unexposed silver halide is complexed with the silver halide complexing agent after which the emulsion is contacted against the receiving sheet and the complex silver halide diffuses imagewise to the receiving sheet containing nuclei.

In some instances it may be desirable to treat the receiving sheet in order to improve the stability of the sheet, particularly with regard to the silver image thereon. A simple stabilizing method merely involves washing the print in order to remove any processing chemicals which may remain thereon. However, the washing step does not protect the print from subsequent chemical reactions with oxygen, hydrogen sulfide, etc., in the atmosphere, which have an adverse effect on the stability of the silver image.

For these reasons, it has been proposed to coat the print with a coating composition such as that disclosed in U.S. Pat. No. 2,979,477 comprising a mixture of vinylpyridine polymer and a hydantoin-formaldehyde condensation polymer.

Suitable print coating compositions may also employ a polymeric material such as methylmethacrylate-methacrylic acid copolymer or the combination of an acid group or sulfate group containing polymer such as copoly(methylmethacrylate-methacrylic acid) and a hydantoin-formaldehyde condensation polymer, such as that disclosed in French Pat. No. 1,493,188. A heavy metal salt such as zinc acetate may also advantageously be incorporated in the print coating composition. Further improvement is obtained by incorporating in the coating composition an acid such as acetic acid, propionic acid or the like.

In some instances, it can be helpful to apply a solution, e.g., an aqueous solution of a strong reducing agent, such as sodium borohydride, to the surface of a print made employing a diffusion transfer process, such as described in U.S. Pat. No. 2,698,237 of Land issued Dec. 28, 1954. Application of this solution can return the developed image to a neutral black tone should undesired loss of black tone or loss of image resulting from affects of hydrogen sulfide in the atmosphere, highly humid keeping conditions or the like have occurred. It is desirable to apply the solution without any protective overcoat having been applied to the print. A 10 percent, by weight, aqueous solution of sodium borohydride is especially suitable, but other reducing agents are effective, e.g., stannous chloride, hydrazine and ascorbic acid.

It can be also useful in some instances after formation of a developed image in an image receiver by a diffusion transfer process, such as described in U.S. Pat. No. 2,698,237 of Land issued Dec. 28, 1954, to stabilize the image by treatment with various stabilizing agents. This can include, for instance, treatment of a print prepared by the described process, such as by swabbing, with a stabilizer solution, e.g., an aqueous solution containing equal parts, by weight, water and methanol, or a solution of a cationic stabilizer such as a phosphonium or quaternary ammonium stabilizer, such as poly 1,2-dimethyl-5-vinyl pyridinium methyl sulfate, 2-methyl-3-ethyl benzothiazolium para toluene sulfonate, tetrabutyl phosphonium chloride, or triphenyl benzyl phosphonium chloride. A concentration of the described stabilizer of about 0.5 to about 3 milligrams per milliliter of solution is usually sufficient. This stabilization can provide desired cold tone and maintain desired speed.

The silver halide emulsions employed in this invention can contain incorporated addenda, including chemical sensitizing and spectral sensitizing agents, coating agents, antifoggants and the like. They can also contain processing agents such as silver halide developing agents and/or developing agent precursors. Of course, the processing agents can be incorporated in a layer adjacent to the silver halide emulsion if desired.

The developing agents and/or developing agent precursors can be employed in a viscous processing composition containing a thickener such as carboxymethyl cellulose or hydroxyethyl cellulose. A typical developer composition is disclosed in U.S. Pat. No. 3,120,795 of Land et al. issued Feb. 11, 1964.

The silver halide developing agents used for initiating development of the exposed sensitive element can be the conventional types used for developing films or papers with the exception that a silver halide solvent such as sodium thiosulfate, sodium thiocyanate, ammonia or the like, is present in the quantity required to form a soluble silver complex which diffuses imagewise to the receiving support. Usually, the concentration of developing agent and/or developing agent precursor employed is about 3 to about 320 mg./ft..sup.2 of support.

The developing agents and/or developing agent precursor can be employed alone or in combination with each other, as well as with auxiliary developing agents. Suitable silver halide developing agents and developing agent precursors which can be employed include, for example, polyhydroxybenzenes, such as hydroquinone developing agents, e.g., hydroquinone, alkyl substituted hydroquinones, as exemplified by t-butyl hydroquinone, methyl hydroquinone and 2,5-dimethylhydroquinone, catechol and pyrogallol; chloro substituted hydroquinones such as chlorohydroquinone or dichlorohydroquinone; alkoxy substituted hydroquinones such as methoxy hydroquinone or ethoxy hydroquinone; aminophenol developing agents such as 2,4-diaminophenols and methylaminophenols; ascorbic acid, ascorbic acid ketals, such as those described in U.S. Pat. No. 3,337,342 of Green issued Aug. 22, 1967; hydroxylamines such as N,N-di(2-ethoxyethyl) hydroxylamine; 3-pyrazolidone developing agents such as 1-phenyl-3-pyrazolidone, including those described in Kodak British Pat. No. 930,572 published July 3, 1963; and acyl derivatives of p-amino-phenol such as described in Kodak British Pat. No. 1,045,303 published Oct. 12, 1966.

Lactone derivative silver halide developing agents which have the property of forming a lactone silver halide developing agent precursor under neutral and acid conditions are particularly useful. Typical lactone derivatives are described in copending U.S. application Ser. No. 764,348 filed Oct. 1, 1968 entitled "Photographic Compositions and Processes" in the name of Oftedahl. The particularly suitable lactone derivatives provide desired developing activity and reduction of stain without adversely affecting desired maximum density, minimum density, photographic speed and other desired sensitometric properties. Suitable lactone derivative developing agents include those which under neutral, slightly alkaline or acid conditions, i.e., when the pH is lowered to a level of about 9 or lower, i.e., about 2 to about 9, do not have significant developing activity, if any, due to formation of a developing agent precursor.

A wide variety of hydroxy cinnamic acid and/or amino cinnamic acid developing agents can be employed. Suitable hydroxy cinnamic acid or amino cinnamic acid developing agents include any such compounds which cause reduction of a photographic silver salt in exposed areas of a layer containing such photographic silver salt without adversely affecting the unexposed areas of the photosensitive silver salt. Especially suitable developing agents are derivatives of 6-hydroxy coumarins, 6-amino coumarins, mixtures thereof and their salts, e.g., water-soluble salts.

As pointed out above, combinations of developing agents can be used in the diffusion transfer process. Particularly useful developers include combinations of the following:

1-phenyl-3-pyrazolidone

hydroquinone

methyl hydroquinone

2,5-dimethyl hydroquinone

2,6-dimethyl hydroquinone

tertiary butyl hydroquinone

3,6-dihydroxy benzonorbornane

2,4-diamino-6-methyl phenol dihydrochloride

4-phenyl catechol

tertiary butyl pyrocatechol

2,4-diaminophenol dihydrochloride

ascorbic acid

N-methyl-p-aminophenol sulfate

N,N'-ethylene di(oxymethyl)pyridinium perchlorate

2-(3-sulfopropyl)-2-thiopseudo urea

7,14-diazo-6,15-dioxoeicosane-1,21-bis(pyridinium perchlorate)

The receiving layers and receiving elements of this invention can be employed with a wide range of photographic emulsions. The photographic emulsions employed can be X-ray or other nonspectrally sensitized emulsions or they can contain spectral sensitizing dyes such as described in U.S. Pat. Nos. 2,526,632 of Brooker et al. issued Oct. 24, 1950 and 2,503,776 of Sprague issued Apr. 11, 1950. Spectral sensitizers which can be used include cyanines, merocyanines, styryls and hemicyanines.

The photographic emulsions can contain various photographic addenda, particularly those known to be beneficial in photographic compositions. The various addenda and concentrations to be employed can be determined by those skilled in the art. Suitable photographic addenda include hardeners, e.g., those set forth in British Pat. No. 974,317; buffers which maintain the desired developing activity and/or pH level; coating aids; plasticizers, speed increasing addenda, such as amines, quaternary ammonium salts, sulfonium salts and alkylene oxide polymers; and various stabilizing agents, such as sodium sulfite. The photographic silver salt emulsions of the invention can be chemically sensitized with compounds of the sulfur group such as sulfur, selenium and tellurium sensitizers, noble metal salts such as gold, or reduction sensitized with reducing agents or combinations of such materials.

Various photographic silver salts can be used in the practice of the invention. These include photographic silver halides such as silver iodide, silver bromide, silver chloride, as well as mixed halides such as silver bromoiodide, silver chloroiodide, silver chlorobromide and silver bromochloroiodide. Photographic silver salts which are not silver halides can also be employed such as silver salts of certain organic acids such as silver behenate, silver-dye salts or complexes, etc.

The photographic silver salts are typically contained in an emulsion layer comprising any of the known binding materials suitable for photographic purposes. These include natural and synthetic binding materials generally employed for this purpose, for example, gelatin, colloidal albumin, water-soluble vinyl polymers, such as mono and polysaccarides, cellulose derivatives, proteins, water-soluble polyacrylamides, polyvinyl pyrrolidone and the like, as well as mixtures of such binding agents. The elements can also contain stripping layers and/or antistatic layers (i.e., conducting layers).

Stripping agents can be used either on the surface of the silver halide emulsion layer, on the receiving layer containing the nuclei, or can be contained in the developing or processing solutions. When added to the processing solution in concentrations of about 3 percent to about 10 percent, by weight, the stripping agents prevent the processing solution from sticking to the receiver. Suitable stripping agents normally are used which have a composition different from the binder used in the silver halide emulsion. Typical stripping agents include alkali permeable polysaccharides such as, for example, carboxymethyl cellulose or hydroxyethyl cellulose, 4,4'-dihydroxybiphenol, glucose, sucrose, sorbitol (hexahydric alcohol C.sub.6 H.sub.8 (OH).sub.6), inositol (hexahydroxy-cyclohexane C.sub.6 H.sub.6 (OH).sub.6.sup. . 2H.sub.2 O), resorcinol, phytic acid sodium salt, thixcin (a castor bean product), zinc oxide, and finely divided polyethylene. These coatings are relatively thin having a preferred coverage of about 6.0 mg./ft..sup.2. However, a useful range may be from 1.0 mg. to 1.0 g./ft..sup.2. It will also be understood that a stripping agent or release agent can be incorporated in the receiving layer along with the nuclei and/or binder used as a carrier for the nuclei.

In some adaptations, the nuclei can be carried in the developing or processing solution to form the receiving layer. The use of nuclei in the processing solution permits use of receiving surfaces which have not been specifically prepared as receiving layers. If desired, developing or processing solutions containing nuclei can be used with receiver sheets having thereon a coating containing the nuclei of this invention.

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

EXAMPLE 1

Palladium Nuclei

Solution A Water 657 ml. 20% Latex-copoly(2-chloroethyl 35 ml. methacrylate-acrylic acid) 96% 2-chloroethyl methacrylate- 4% acrylic acid 20% Latex--copoly(butyl acrylate 3.55 ml. acrylic acid) 90% butyl acrylate- 10% acrylic acid 15% Saponin solution 5.0 ml.

To 100 ml. portions of Solution A are added (1) 2.50 ml. of palladium chloride solution at 1.25 mg./ml. of solution; (2) 5.0 ml. of reducing agent solution and (3) distilled water to bring the total volume of each solution to 118 ml.

The samples are held for 30 minutes at 70.degree. C. All of the solutions are then coated at 0.002 inch on a polyethylene coated paper support to give a nuclei coverage of about 75 .mu.g./ft..sup.2 and about 80 mg./ft..sup.2 of latex (solids). All of the coatings are made at 100.degree. F. and cured at 205.degree. F. for 1 minute. The receiving sheet is used in a photographic silver salt diffusion transfer process with an exposed silver chlorobromide emulsion and a developer having the following composition:

Component g./l. __________________________________________________________________________ 2,4-diamino-6-methylphenol sulfate 5-10 Tertiary butyl hydroquinone 25 Na.sub.2 S.sub.2 O.sub.3.sup. . 5H.sub.2 O 60 NaOH 20 KOH 20 KI 0.6-1.6 Hydroxyethyl cellulose 3-4.5% K.sub.2 SO.sub.3 25-50 Water to make 1 liter __________________________________________________________________________

The following results are obtained:

Sensitometry __________________________________________________________________________ Soln. Average nuclei Reducing Conc. particle size Agent mg./ml. Dmax E.degree.,25.degree. C. in melt __________________________________________________________________________ NaBH.sub.4 10 1.64 - 1.24 about 30 A. H.sub.3 PO.sub.2 100 1.52 - 0.50 about 60 A. SnCl.sub.2 100 1.34 + 0.15 about 135 A. HCHO 100 1.14 + 0.056 about 110 A. __________________________________________________________________________

the above data indicate that the nuclei obtained by reducing a palladium salt with a reducing agent having a standard potential more negative than -0.30 result in particularly good transfer densities. This example also shows that a lower density is obtained with nuclei having a large average particle size.

EXAMPLE 2

Palladium nuclei prepared according to this invention are contrasted with other palladium nuclei and with silver nuclei prepared using borohydride and hypophosphite reducing agents. Sensitometric data is determined in this example, using the procedure of Example 1.

a. Palladium Nuclei

Strong reducing agents (e.g., borohydride and hypophosphite) used to form nuclei by the method of Example 1 yield well defined fine particle size nuclei which result in high image density after transfer.

Reducing Agent Dmax __________________________________________________________________________ borohydride 1.30 hypophosphite 1.32 stannous chloride 0.84 formaldehyde 0.99 hydrazine 0.80 __________________________________________________________________________

b. Silver Nuclei

Strong reducing agents (e.g., borohydride) produced nuclei by the method of Example 1 which result in much lower transfer density.

Reducing Agent Dmax __________________________________________________________________________ borohydride 0.98 hypophosphite 0.28 __________________________________________________________________________

EXAMPLE 3

Platinum Nuclei

Strong reducing agents (e.g., borohydride) produce nuclei by the method of Example 1 which result in high transfer density and fine particle size.

Reducing Agent Dmax Average particle size of nuclei __________________________________________________________________________ borohydride 1.22 32 A. __________________________________________________________________________

EXAMPLE 4

Palladium Nuclei vs. Cadmium Sulfide Nuclei

A coating solution containing colloidal palladium nuclei is prepared by adding Solution A to Solution B with vigorous stirring at 25.degree. C.

solution A PdCl.sub.2 0.01 g. 10 N HCl 0.01 ml. Distilled Water 0.8 ml. Solution B Latex containing 7.6% polymeric 54 ml. material prepared from acrylonitrile, vinylidene chloride, acrylic acid and gelatin in a ratio of 15:77:08:25 Distilled water 202 ml. Isopropanol 45 ml. H.sub.3 PO.sub.2 0.5 ml. Polyoxyethylene ether alcohol nonionic 0.6 ml. wetting agent

After heating the above mixture at 70.degree. C. for one hour, the resulting solution is coated on a polyethylene-coated paper support. Reducing agents other than hypophosphorous acid can be used, such as its sodium salt or the like. Other water-soluble salts of palladium, such as palladium nitrate or ammonium chloropallidate can be used.

Cadmium sulfide is prepared in a latex having the same composition in a manner similar to the above procedure, but without heating. A coating solution containing colloidal CdS nuclei is prepared by adding Solution C to Solution D.

solution C 0.02 M Cd(C.sub.2 H.sub.3 O.sub.2).sub.2 4 ml. Solution D Latex 60 ml. Distilled water 210 ml. Isopropanol 50 ml. Na.sub.2 S.sup.. 9H.sub.2 O 3 ml. Polyoxyethylene ether alcohol 0.4 ml. nonionic wetting agent

A silver bromoiodide gelatin emulsion coated on a support is exposed and the above receiving sheets tested with it and a developer having the following composition:

Water 1,860 g. Sodium carboxymethyl cellulose 117 g. Sodium sulfite 73 g. Sodium hydroxide 74.6 g. Sodium thiosulfate 14.5 g. Citric acid 38.5 g. Hydroquinone 52 g.

The following results are obtained, showing that palladium nuclei even at a lower coverage than CdS nuclei produce a good image:

Average Particle Polymer Nuclei size mg./ft..sup.2 .mu.g./ft..sup.2 Nuclei Dmax Dmin __________________________________________________________________________ 30 A. 7.6 11 Pd.degree. 1.58 0.00 35 A. 10.0 30 CdS no image formed __________________________________________________________________________

EXAMPLE 5

Cellophane, 1.6 mils in thickness, is nucleated by the following treatment to form a processing web: A sample is first bathed for 3 minutes in a 0.1 percent gold chloride solution and then bathed for 3 minutes in an alkaline 0.2 percent solution of potassium borohydride. This treatment forms metallic gold nuclei on the cellophane sheet. After washing for 3 minutes, the nucleated sheet is contacted for 30 seconds with a developer having the composition listed below, rolled in contact with a suitably exposed negative, after which the two are separated. A fully developed negative image forms on the exposed film.

Tertiary butyl hydroquinone 25 g. Na.sub.2 S.sub.2 O.sub.3.sup. . 5H.sub.2 O 60 g. NaOH 20 g. KOH 20 g. KI 0.6-1.6 g. Hydroxyethyl cellulose 3-4.5 % K.sub.2 SO.sub.3 25-50 g. 2,4-diamino-6-methylphenol 5-10 g. sulfate Water to make 1 liter

The cellophane sheet shows bronzing and a high minimum density. The minimum density is 0.5 compared to a maximum density of 1.3, or a density difference of 0.8. This is a poor density difference and is not an acceptable image.

This example shows that a reduction using borohydride in the absence of colloid results in nuclei which are unsatisfactory for use in the diffusion transfer system.

EXAMPLE 6

In situ Preparation

Part A

Potassium choraurate is dispersed in a physical mixture of 9 parts latex containing polymeric material prepared from a mixture consisting of 2-chloroethyl methacrylate and acrylic acid in a ratio of 98:2 and one part of a polymeric latex consisting of N-butyl acrylate and acrylic acid in a ratio of 9:1 and coated on a polyethylene-coated paper support at 0.144 mg./ft..sup.2.

Part B

Prepared like Part A except that palladium chloride is used instead of potassium chloraurate and coated at 0.125 mg./ft..sup.2.

These coatings are overcoated with an ethanolic solution of NaBH.sub.4 at 4 mg. NaBH.sub.4 /ft..sup.2, allowed to dry at 100.degree. F. and stand overnight, then cured 2 minutes at 100.degree.-110.degree. C. before being processed. A high-speed silver bromoiodide gelatin emulsion coated on a paper support is exposed and the above receivers tested with it and a developer at 20.degree. C. as described in Example 1 to yield the following results:

Receiver Dmax Dmin Tone __________________________________________________________________________ A 1.33 0.14 cold B 1.53 0.11 fairly cold __________________________________________________________________________

A and B are overcoated with solutions of hypophosphorous acid and processed as above with similar results.

EXAMPLE 7

Palladium Nuclei vs. Cadmium Sulfide, CLS and Silver Sulfide Nuclei in Latex

A coating solution containing colloidal palladium nuclei is prepared by adding Solution A to Solution B with vigorous stirring at 25.degree. C. The mixture is heated to 70.degree. C. for one hour, then cooled.

Solution A PdCl.sub.2 0.00312 g. 10 N HCl 0.003 ml. Distilled water 0.25 ml. Solution B Latex containing 20% polymeric 10 ml. material consisting of 2-chloro ethyl methacrylate & acrylic acid in a ratio 98:2 Distilled water 180 ml. H.sub.3 PO.sub.2 0.1 ml. Anionic wetting agent 1 ml.

A yellow colloidal dispersion of CdS in latex is prepared: 5 g. of the latex used above in Solution B is dispersed in 35 ml. distilled water; to this is added 30 ml. of a 20 percent cadmium acetate (.sup.. 2 H.sub.2 O) solution and then 30 ml. of 1 percent sodium sulfide (.sup.. 9 H.sub.2 O), dropwise with good stirring at 72.degree. F.

Carey Lea silver (CLS) is prepared in a latex having the above composition by mixing 10 ml. of a colloidal Carey Lea silver dispersion with 40 ml. of a 1 percent latex solution.

Silver sulfide nuclei coated in a latex are prepared as above for the CdS using a silver sulfide dispersion.

The above nuclei are coated on polyethylene-coated paper and tested as in Example 1, with the following results showing that palladium produces an image of higher quality.

Polymer Nuclei mg./ft..sup.2 mg./ft..sup.2 Nuclei Dmax Dmin Tone __________________________________________________________________________ 39 0.035 Pd.degree. 1.34 0.07 Cold 37 65.0 CdS 0.76 0.30 Cold 30 0.03 CLS no ima ge formed 30 0.06 Ag.sub.2 S0.76 0.04 Cold __________________________________________________________________________

EXAMPLE 8

Palladium Metal Nuclei in a Colloidal Silica Vehicle

A coating solution containing colloidal palladium nuclei is prepared by adding Solution A to Solution B with vigorous stirring at 25.degree. C.

solution A PdCl.sub.2 0.0156 g. 10 N HCl 0.0156 ml. Distilled water 1.25 ml. Solution B Colloidal dispersion of SiO.sub.2 80 ml. in water Distilled water 120 ml. Hypophosphorous acid 0.1 ml. Anionic wetting agent 1 ml.

The above nuclei are coated on polyethylene-coated paper at 160 mg./ft..sup.2 silica and 0.15 mg./ft..sup.2 palladium metal and tested as in Example 1 to give a silver image of very good quality.

EXAMPLE 9

Noble Metals in Latex

Solution A Water 657 ml. Latex containing 20% polymeric 35 ml. material prepared from a mixture consisting of methyl acrylate, 2- chloroethyl acrylate, vinyldene chloride and itaconic acid in a ratio of 25:39:34:02 Latex (19.73% solids) (90% butyl 3.55 ml. acrylate-10% acrylic acid polymer) 15% Saponin solution 5.0 ml.

To 100 ml. portions of Solution A are added: (1) metal salt solutions at 2.0 mg. metal salt/ml. solution (except PdCl.sub.2 solution which is at 1.25 mg./ml. solution) in the amounts listed in Table I below; (2) 5.0 ml. of NaBH.sub.4 solution except for coatings A and B in which 0.05 ml. of commercial H.sub.3 PO.sub.2 is used as the reducing agent, and (3) distilled water to bring the total volume of each solution to 118 ml.

The solution for A and B is held for 30-45 minutes at 70.degree. C.; the remaining solutions are held 1-2 hours at 50.degree. C.; all are then coated at 0.002 inches on a polyethylene-coated paper support to give a nuclei coverage of 75 .mu.g./ft..sup.2 and aged approximately 5 minutes at 100-110.degree. C. These receiving sheets are tested as in Example 1 except that the following processing composition is used to process B, D, F, H, K and M.

sodium sulfite 21.85 g./l. Sodium thiosulfate.sup.. 5 H.sub.2 O83.87 g./l. Potassium bromide 31.33 g./l. Potassium iodide 0.08 g./l. Sodium hydroxide 71.39 g./l. Methylhydroquinone 5.5 g./l. Diaminophenol hydrochloride 31.5 g./l. Hydroxyethyl cellulose 30 g./l. Water to make 1 liter

Results are listed in Table I. --------------------------------------------------------------------------- TABLE I

Results __________________________________________________________________________ Metal ml. metal Coating Salt salt soln. Tone Dmax Dmin __________________________________________________________________________ A PdCl.sub.2 2.50 Black Very good fair B PdCl.sub.2 2.50 Black Very good fair C PdCl.sub.2 2.50 Brown Very good fair D PdCl.sub.2 2.50 Brown Very good fair E Na.sub.2 PtCl.sub.6.sup.. 6H.sub.2 O 2.70 Brown good good F Na.sub.2 PtCl.sub.6.sup. . 6H.sub.2 O 2.70 Brown good good G RuCl.sub.3 1.92 Black fair good H RuCl.sub.3 1.92 Black fair good J RhCl.sub.3.sup. . 4H.sub.2 O 2.56 Black .times..times..times.Dmax fair fair Brown Dmin K RhCl.sub.3.sup. . 4H.sub.2 O 2.56 Brown Dmin fair good L KAuCl.sub.4 1.80 Brown excellent good M KAuCl.sub.4 1.80 Brown excellent good __________________________________________________________________________

EXAMPLE 10

A nuclei processing web dispersion is prepared containing the following components:

Nuclei Dispersion A. 20%, by weight, gelatin in water 90 g. Water 1,680 cc. Sodium hypophosphite anhydrous 2.16 g. Sulfuric Acid, 2 N 60 cc. B. Ammonium chloropallidate, 1.665 g./l. 90 cc. Water 510 cc. C. 20%, by weight, gelatin in water 2,160 g.

B is poured into A and maintained 5 minutes at 70.degree. C. and C is added. Water is added to bring the solution to 4,500 cc.

A coating composition having the following components is prepared:

Nuclei dispersion 600 g. Gelatin 453 g. Water 4,680 g. Mucochloric acid 250 cc. 15%, by weight, Saponin in water 30 cc.

This composition is coated on cellulose acetate film support to form a nucleated web and dried. The nucleated web is then immersed for 3 minutes in a processing solution having the following composition:

4,4-dimethyl-1-phenyl-3-pyrazolidone 1.0 g. Hydroquinone 10.0 g. 2,2'-iminodiethanol-SO.sub.2 addition product 190.0 g. (20 mole percent SO.sub.2) 2,2'-iminodiethanol 50.0 g. Sodium thiosulfate, pentahydrate 8.0 g. Water to make 1 liter

The sheet is then squeegeed to removed excess solution and rolled in contact with an exposed silver chlorobromide photographic emulsion. After ten minutes, the two are separated. A developed negative is obtained in the emulsion layer, as well as a positive in the processing web.

EXAMPLE 11

A processing web is prepared as in Example 10 except that the following coating composition is applied to the film support:

Nuclei dispersion 500 g. Gelatin 453 g. Water 4,680 g. 15%, by weight, Saponin in water 30 cc. Formalin (40%, by weight, formaldehyde 40 cc. in water)

After imbibing with the processing solution of Example 10, the web is rolled in contact with an exposed silver positive and negative images.

EXAMPLE 12

Size Frequency Study

Pictures are obtained as in Example 1 using platinum nuclei formed by means of borohydride reduction. A size frequency count involving 86 nuclei particles show that about 85 percent of the particles are less than 40 A. in diameter with the following distribution: ---------------------------------------------------------------------------

about 20 A. 13 particles about 25 29 about 35 28 about 45 7 about 50 6 about 62.5 2 about 75 1 __________________________________________________________________________ 86 __________________________________________________________________________

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

Claims

We claim:

1. A receiving layer for use in a diffusion transfer transfer process comprising a colloid binder and nonsilver noble metal nuclei having an average particle size in the range of about 15 A. to about 65 A., at least about 80 percent, by number, of said nuclei having a particle size in the range of about 20 A. to about 50 A.

2. A receiving element comprising a support having thereon said receiving layer of claim 1.

3. A receiving element according to claim 2 in which said support is paper.

4. A receiving element according to claim 2 in which said nuclei are coated on said support in an amount of about 1 to about 200 .mu.g./ft..sup.2.

5. A receiving element according to claim 2 in which said colloid is gelatin.

6. A photographic element comprising a support having thereon said receiving layer of claim 1 and having over said layer an overcoat of a photographic silver halide emulsion.

7. A receiving element of claim 2 in which said metal nuclei are palladium

8. A receiving element according to claim 2 in which said support is photographic film base.

9. A photographic element comprising a image in a receiving layer on a support, said silver image obtained by a silver ion diffusion transfer process, said receiving layer comprising a colloid binder and nonsilver noble metal nuclei, substantially all nuclei in said layer having a particle size in the range of about 15 A. to about 65 A. and about 80 percent of the total number of said nuclei having a particle size in the range of about 20 A. to about 50 A.

10. A receiving layer for use in the diffusion transfer process comprising a reaction product obtained by forming finely divided nonsilver noble metal nuclei from a salt of said metal by reducing said metal salt, in the presence of a colloid, with a reducing agent having a standard potential more negative than -0.30.

11. A receiving layer of claim 10 in which said reducing agent is a hypophosphite or a borohydride.

12. A receiving layer of claim 10 in which said metal salt is palladium chloride.

13. A receiving layer of claim 10 in which said metal salt is palladium nitrate.

14. A receiving layer of claim 10 in which said metal salt is ammonium chloroplatinate.

15. A receiving layer of claim 10 which comprises a gelatin polymeric latex vehicle for said nuclei.

16. A receiving layer of claim 15 in which said vehicle is prepared from a monomeric mixture containing acrylonitrile, vinylidene chloride, acrylic acid with gelatin.

17. A receiving layer of claim 10 in which said metal salt is sodium chloropallidate.

18. A receiving layer of claim 10 in which said nuclei are coated in an amount in the range of about 1 to about 200 .mu.g./ft..sup.2.

19. A receiving layer of claim 10 which comprises a gelatin vehicle for said nuclei.