US3887376A - Photographic elements, compositions and processes - Google Patents

Abstract

N-hydroxyurea silver halide developing agents in photographic processing compositions, elements and processes provide desired developing activity. These can be employed in various photographic products including processing compositions, photosensitive compositions, photographic elements and chemical transfer systems. They can be used in combination with other silver halide developing agents and with addenda commonly employed in photographic processing compositions and elements.

Description

Wilson et al.

PHOTOGRAPHIC ELEMENTS, COMPOSITIONS AND PROCESSES Inventors: Burton D. Wilson; Paul E.

Woodgate, both of Rochester; Richard W. Henn, Pittsford, all of NY.

Eastman Kodak Company, Rochester, NY.

Filed: June 13, 1974 Appl. No.: 479,024

Related US. Application Data Assignee:

[ June 3, 1975 2,404,774 7/1946 Dersch 96/66.3 2,477,323 7/1949 Wood 96/66.3

2,819,165 1/1958 Mackey 96/61 3,438,776 4/1969 Yudelson 96/66 R 3,730,727 5/1973 Olivares et al.... 96/95 3,794,488 2/1974 Henn et al. 96/50 R Primary ExaminerMary F. Kelley Attorney, Agent, or FirmR. E. Knapp [5 7] ABSTRACT N-hydroxyurea silver halide developing agents in photographic processing compositions, elements and processes providedesired developing activity. These can be employed in various photographic products including processing compositions, photosensitive compositions, photographic elements and chemical transfer systems. They can be used in combination with other silver halide developing agents and with addenda commonly employed in photographic processing compositions and elements.

4 Claims, No Drawings 1 PHOTOGRAPHIC ELEMENTS, COMPOSITIONS AND PROCESSES This is a divisional of U.S. Pat. application Ser. No. 252,036 of Wilson, Woodgate and Henn, filed May 10, 1972 now abandoned as the updated status of Ser. No. 252,036.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to N-hydroxyurea reducing agents in photographic elements, compositions and processes. In one of its aspects it relates to photographic processing compositions containing these N- hydroxyurea reducing agents. In another aspect it relates to photographic elements containing such reducing agents. In a further aspect it relates to photographic compositions and to processes, such as processing with heat, to develop an image in a photographic element.

2. Description of the State of the Art The use of various nitrogen containing compounds as photographic developing agents and for other purposes in photographic materials is known. For example, hydroxylamines have been used as developing agents as described, for example, in Belgian Pat. No. 558,501 of Gevaert published July 15, 1957; U.S. Pat. No. 3,287,125 of Green et al., issued Nov. 22, 1966 and the like. Certain urea derivatives have also been employed in photographic materials as described in Canadian Pat. No. 456,029 and U.S. Pat. 2,404,774 of Derisch et al., U.S. Pat. No. 2,477,323 of Wood issued July 26, 1949 and U.S. Pat. No. 2,819,165 of Mackey, issued Jan. 7, 1958. Hydroxymethylurea compounds have also been employed in diazo materials as described in U.S. Pat. 3,453,112 of Schaefer, issued July 1, 1969; U.S. Pat. No. 3,316,092 of Klimkowski et al. issued Apr. 25, 1967 and French patent of addition No. 83,978 of Bauchet published Sept. 28, 1964. However, these are not N-hydroxyurea reducing agents of the invention. There has been a continuing need to provide nitrogen containing reducing agents for photosensitive materials which provide reduced staining propensity. While hydroxylamine and various derivatives have been employed for this purpose, they have not always provided sufficient developing activity or stability. This is demonstrated in following comparative Example 9.

There has also been a continuing need to provide combinations of reducing agents which provide reduced processing time and reduced staining propensity. This is especially important in photosensitive materials for processing with heat in which the processing agents remain in the photosensitive material after processing.

Accordingly, it is an object of the invention to provide photographic elements, processing compositions, photosensitive compositions and processes, such as photographic materials for processing with heat, employ certain silver halide developing agents which provide decreased processing time with reduced staining propensity.

SUMMARY OF THE INVENTION According to the invention decreased processing time with reduced staining propensity, without significant loss of desired sensitometric properties, is provided in a photographic element, composition, processing composition and/or process by an N-hydroxyurea silver halide developing agent. Such N-hydroxyurea silver halide developing agents provide especially suitable results when employed in combination with other silver halide developing agents, such as 3-pyrazolidone silver halide developing agents.

The described N-hydroxyurea silver halide developing agents are suitable in photothermographic materials containing a photosensitive component with an oxidation-reduction imageforming combination.

The N-hydroxyurea silver halide developing agents described yield colorless oxidation products which are especially suitable in photosensitive materials which require that the processing agents remain in the photosensitive material after processing. The N-hydroxyurea developing agents provide surprisingly reduced propensity for staining compared to prior art silver halide developing agents such as hydroquinone and paraaminophenol silver halide developing agents which provide undesired oxidation stain. This is demonstrated in following comparative Example 17.

DETAILED DESCRIPTION OF THE INVENTION A variety of N-hydroxyurea reducing agents can be employed according to the invention. One test for suitable N-hydroxyurea reducing agents according to the invention when the reducing agents are to be employed in an aqueous alkaline processing composition is set out in following Example 1. A further test for suitable N-hydroxyurea reducing agents when the reducing agent is to be employed in a photothermographic material is set out in following Example 18.

A useful class of N-hydroxyurea silver halide developing agents according to the invention is represented by the formula:

R1 o R r II 1 N c N I R2 on wherein R, R and R are hydrogen, alkyl, especially alkyl containing 1 to 4 carbon atoms, such as methyl, ethyl, propyl and butyl, or aryl, typically aryl containing 6 to 10 carbon atoms, such -as phenyl, tolyl and xylyl. R R and/or R can contain substituent groups which do not adversely affect developing activity of the described N-hydroxyurea silver halide developing agents. Such substituent groups include, for example, halogen or amino groups. Within the described class of N-hydroxyurea silver halide developing agents especially useful reducing agents are those wherein R is hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms, such as phenyl, tolyl or xylyl; R is hydrogen, alkyl of l to 4 carbon atoms or aryl containing 6 to 10 carbon atoms such as phenyl, tolyl or xylyl; R is hydrogen, alkyl containing 1 to 4 carbon atoms or phenyl, tolyl or xylyl. Examples of suitable N-hydroxyurea silver halide developing agents are compounds wherein R, R and R in the described structure are as follows:

-Continued Compound No.

As can be seen from Examples 2, 3, 4 and 5, above, preferred N-hydroxyurea silver halide developing agents can be represented by the formula methoxyphenyl or p-chlorophenyl.

The described N-hydroxyurea reducing agents can be prepared by procedures known in the art.

The described N-hydroxyurea reducing agents can be employed in a range of physical locations in a photographic system. They can be employed in one or more layers of a photographic element and/or in a processing composition if desired. The optimum location will depend upon the desired image, processing conditions, particular photographic system and the like. For example, the described N-hydroxyurea silver halide developing agents can be employed in a processing composition, such as an aqueous, alkaline developer solution or they can be incorporated into one or more layers of a photographic element, such as a photographic silver halide emulsion layer, a layer between the support and a photographic silver halide emulsion layer, and/or an overcoat layer.

One embodiment of the invention is a photographic processing composition comprising an alkaline devel' oper activator and an N-hydroxyurea silver halide developing agent, as described. This is typically an aqueous alkaline solution.

Various development activators can be employed in the practice of the invention. These include any of those which provide the desired activation of the described developing agents. These include, for instance, alkaline development activators, such as inorganic alkalies including, for example, sodium hydroxide, potassium hydroxide and/or lithium hydroxide, alkali metal carbonates such as sodium carbonate, and potassium carbonate, alkali metal phosphates such as trisodium phosphate, and/or organic alkaline development activators such as quaternary ammonium bases, amines such as amino alkanols and similar alkaline materials and/or alkali releasing materials. The described development activators can be employed in the described processing composition and/or applied to the described photographic element in any suitable manner including, for example, dipping, spraying and/or suitable surface applications such as with rollers or other mechanical means.

The pH of the processing composition should be sufficient to provide desired activation of the described developing agent. A pH of about to about 14 is typically employed.

A wide range of concentration of the described developing agent can be employed in a processing composition in the practice of the invention depending upon the desired image, the developing agent employed, processing conditions and the like. A concentration of about 0.5 to about 50 grams, and typically about 2 to about 20 grams of developing agent is suitable per liter of processing composition.

The described silver halide developing agents can be employed in combination with any silver halide developing agent or developing agent precursor which does not adversely affect the developing activity of the N- hydroxyurea compounds. Suitable silver halide developing agents which can be employed include, for example, polyhydroxybenzenes, such as hydroquinone silver halide developing agents, such as hydroquinone, alkylsubstituted hydroquinones, as exemplified by tertiary butyl hydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and 2,6-dimethylhydroquinone; catechols and pyrogallol; chlorosubstituted 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 developing agents such as ascorbic acid, ascorbic acid ketals and ascorbic acid derivatives; hydroxylamine developing agents such as N,N-di(2- ethoxyethyl) 3-pyrazolidone developing agents such as 1-phenyl-3'pyrazolidone and/or 4-methyl-4- hydroxymethyl-l-phenyl-3-pyrazolidone; and the like. Combinations of these developing agents can be employed if desired.

The combination of the described N-hydroxyurea silver halide developing agents with a 3-pyrazolidone developing agent provides surprisingly reduced processing time to provide desired image density without undesired increase in minimum density. Typical 3- pyrazolidone silver halide developing agents which can be employed in this combination are described, for example, in US. Pat. No. 3,453,109 of Lee issued July 1, 1969; US. Pat. No. 3,284,200 of Ficken issued Nov. 8, 1966; U.S. Pat. 3,523,795 of Ohkubo et al issued Aug. 11, 1970; British Pat. No. 1,093,281 issued Nov. 29, 1967 and US. Pat. No. 2,875,048 of Haist and King issued Feb. 24, l959. Typical 3-pyrazolidone silver halide developing agents which can be employed in the described combination include, for example, l-phenyl- 4,4-dihydroxymethyl-3-pyrazolidone; 1-phenyl-4- methyl4-hydroxymethyl3-pyrazolidone; l-phenyl-3- pyrazolidone; 5-phenyl-3-pyrazolidone; 5-methyl-3- pyrazolidone and the like.

A range of concentrations of the described N- hydroxyurea silver halide developing agent can be employed with a range of concentrations of the described 3-pyrazolidone silver halide developing agents. Typically a concentration ratio of 10 parts by weight N- hydroxyurea silver halide developing agent is employed for each part by weight of 3-pyrazolidone silver halide developing agent. A typical concentration range of 3- pyrazolidone silver halide developing agent in a processing composition is about 0.05 grams to about 5 grams of 3-pyrazolidone silver halide developing agent per liter of processing composition.

The described silver halide developing agents can be employed in a range of photographic processing compositions, such as in photographic silver halide developer compositions, hardener compositions, monobaths, and the like.

The photographic processing composition can contain a silver halide solvent if desired. Typical silver halide solvents include, for example, alkali metal or ammonium thiosulfates and thiocyanates, such as sodium thiosulfate, sodium thiocyanate or ammonium thiocyanate and organic silver halide solvents such as thiourea and certain organic amines.

The processing composition as described can be a monobath. Typical components of monobaths are described, for example, in the Monobath Manual by Grant and Haist, published by London Press, 1966.

Another embodiment of the invention is a photosensitive composition comprising a photosensitive component, especially a photosensitive silver salt, and an N- hydroxyurea silver halide developing agent as described. The photosensitive silver salt is typically a photosensitive silver halide.

A range of concentration of the described N- hydroxyurea silver halide developing agent can be employed when the developing agent is a component of a photographic element and/or photosensitive composition such as a photosensitive silver halide emulsion. Typically the concentration of silver halide developing agent is about 0.1 mole to about 50 moles of developing agent per mole of silver present in the photographic element or photosensitive composition, preferably about 05 moles to about 4 moles of silver halide developing agent per mole of silver in the element or composition. This typically corresponds to about to about 500 milligrams of silver halide developing agent per 929 square centimeters of support. When used in photosensitive materials for processing with heat typically a concentration of about 0.1 to about 2 moles of N- hydroxyurea developing agent is employed per mole of silver in the photosensitive material.

Silver halide materials which can be employed according to the invention include any photosensitive silver halide, such as silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. The silver halide materials which are suitable are described in the Product Licensing Index, Volume 92, December, 1971, publication 9232, pages 107-110 in paragraphs I, II and III. A photosensitive silver halide can be chemically sensitized as described in paragraph 111 of this Product Licensing Index Publication.

The silver halide photosensitive elements and compositions according to the invention can contain development modifiers, antifoggants, stabilizers, hardeners, plasticizers and lubricants, coating aids, matting agents, brighteners and spectral sensitizing dyes described in the Product Licensing Index, Vol. 92, December, 1971, publication 9232, pages 107-1 10. The silver halide photosensitive compositions according to the invention can be chemically sensitized, washed and/or coated employing the procedures described in this publication.

Another embodiment of the invention accordingly is a photosensitive silver halide emulsion comprising photosensitive silver halide, a binder and an N hydroxyurea silver halide developing agent as described.

A photographic element and/or composition described according to the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Typically hydrophilic materials are employed in those instances where aqueous solutions are to be used in processing. However, in those instances in which the photosensitive material is for processing with heat, a hydrophobic binder can be used. Accordingly, hydrophilic and/or hydrophobic materials can be employed as binders depending on the particular photosensitive material and the intended processing. Suitable hydrophilic materials include naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water soluble polyvinyl compounds like poly(vinylpyrrolidone), acrylic polymers and the like. Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as in latex form and particularly those which increased dimensional stability of photographic materials. Suitable synthetic polymers include those described in the Product Licensing Index, Volume 92, December, 1971, publication 9232, pages 107-110 in paragraph VIII.

The photosensitive materials and other layers of a photographic element according to the invention can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polystyrene film, polyethylene terephthalate, film, polycarbonate film and related films or resinous materials as well as glass, paper, metal and the like. Typically a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/or an alpha olefin polymer particularly a polymer of an alpha olefin containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymers and the like.

Another embodiment of the invention is a photographic element comprising a support having thereon a photosensitive silver salt, typically photosensitive silver halide, an N-hydroxyurea silver halide developing agent, as described, and a binder.

The photosensitive silver halide materials employed according to the invention can be x-ray or other nonspectrally sensitized materials or they can contain spectral sensitizing dyes as described.

The sensitizing dyes and/or other addenda, such as the described silver halide developing agents according to the invention, can be added from water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures known in the photographic art as described in the mentioned Product Licensing Index publication.

The described N-hydroxyurea silver halide developing agents can be employed in combination with a socalled stabilizer precursor. These are typically sulfurcontaining compounds contiguous to photographic silver halide which in the presence of an activator breakdown or cleave to form a compound that combines or complexes with the silver halide in unexposed and undeveloped areas of a photographic element to form a complex or compound which is believed to be a silver mercaptide which is more stable than silver halide to light humidity and ambient conditions. Such compounds are described, for example, in US. Pat. No. 3,301,678 of Humphlett et 211, issued Jan. 31, 1967; Belgian Pat. No. 709,967 and Belgian Pat. 709,900. Examples of suitable silver halide stabilizer precursors include 3-S-isothiuronium propane sulfonate; 2-S- isothiuronium ethane sulfonate and 1,8-(3,6- dioxaoctane)bis (isothiuronium trichloroacetate). A

suitable concentration of stabilizer precursor will vary depending on the particular photographic element, the desired image, processing conditions and the like. Usu' ally a concentration of about 0.25 to about 10 molels of stabilizer precursor per mole of photosensitive silver halide in the element is suitable.

After exposure, the resulting latent image in a photographic element containing the described silver halide developing agent can be developed by contacting the element with an alkaline development activator as described. An especially suitable activator is an alkaline aqueous solution containing an alkali metal hydroxide at a pH of about 10 to about 14.5, especially 12 to 14.5. The described development activators can be applied to the photographic element according to the invention in any suitable manner which provides desired activation including, for example, dipping, spraying, and/or surface application such as with rollers or by surface application processing.

So-called web processing can be employed as described, for example, in US. Pat. No. 3,179,517 ofTregillus et al., issued Apr. 20, 1965 or so-called stabilization processing as described in Russell et al, PSA Journal, Volume 16B, August, 1950.

The time for processing a photographic element containing a developing agent according to the invention, that is developing a desired latent image, can vary over a wide range, typically between about 1 second to several minutes depending on the desired image, processing conditions, particular developing agent and the like.

Processing conditions can also vary. When the described developing agent is in a processing solution and/or in a photographic element, processing is usually carried out under ambient pressures and temperatures of about 20C. to about 30C. If desired, higher temper atures can be used.

The described N-hydroxyurea silver halide developing agents can be employed in a diffusion transfer photographic system, especially a photographic silver salt diffusion transfer system. The described developing agents can be employed in one or more layers of a photographic element and/or in a processing composition in such a system if desired. Suitable diffusion transfer systems, processes, processing compositions and elements therefore are described, for example, in U.S. Pat. No. 2,452,181 of Land issued Feb. 27, 1951; and US. Pat. 3,337,342 of Green issued Aug. 27, 1967. Accordingly, another embodiment of the invention is: in a photographic product comprising in combination (a) a photographic element comprising photographic silver halide, (b) a processing composition containing a silver halide solvent, and (c) an image-receiving layer an N- hydroxyurea silver halide developing agent as described. The N-hydroxyurea silver halide developing agent is typically present in the processing composition. The product is typically employed for developing an image by exposing the photographic silver halide element to form a latent image therein; developing the latent image with a processing composition, such as at a pH of about 12 to about 14, containing the described N-hydroxyurea silver halide developing agent with a silver halide solvent; contacting undeveloped silver halide in the photographic silver halide layer with the silver halide solvent to form an imagewise distribution of a silver complex in the unexposed areas of the photo graphic silver halide layer; transferring at least part of the silver complex to an image receiver layer contiguous to the photographic silver halide layer; reducing the silver complex in the presence of development nuclei to form a visible image in the receiver layer; and lowering the pH of the processing composition to below about 8 to form a stable developed image.

The developing agents according to the invention can be present in one or more layers of elements designed for color photography, for example, elements containing color-forming couplers, or elements to be developed in solutions containing color-forming couplers; or in so-called false-sensitized color materials such as those described in US. Pat. No. 2,763,549 of Hanson issued Sept. 18, 1956.

If desired, the developing agents can be employed in so-called hardening developers such as described in US. Pat. No. 3,232,761 of Allen and Burness, issued Feb. 1, 1966; or in roller transport processors which is described in US. Pat. No. 3,025,779 of Russell et al, issued March 20, 1962.

The described developing agents can also be employed in photosensitive materials designed for pro cessing with heat. Photosensitive materials for processing with heat in which the described N-hydroxyurea silver halide developing agents are especially suitable are described, for example, in US. Pat. No. 3,457,075 of Morgan et al, issued July 22, 1969; US. Pat. No. 3,152,904 of Sorenson et al., issued Oct. 13, 1964; US. Pat. No. 3,392,020 of Yutzy et al., issued July 9, 1968; and Belgian Pat. No. 705,872. In photosensitive elements for processing with heat typically a support is provided having thereon an oxidationreduction image forming combination comprising an oxidizing agent, typically a heavy metal salt oxidizing agent, such as a silver salt of a fatty acid. with an N-hydroxyurea reducing agent and a catalyst for the image-forming combination, such as photosensitive silver halide. A visible image is produced after exposure of the photosensitive element Within a short time, such as about 1 to about 60 seconds, after exposure by heating the element to moderately elevated temperatures, such as about C. to about C.

Accordingly, another embodiment of the invention in a photothermographic element comprising a support having thereon a photosensitive component, such as a photosensitive silver salt, an oxidation-reduction image-forming combination comprising (a) an oxidizing agent, typically a heavy metal salt oxidizing agent, such as silver behenate, with (b) an N-hydroxyurea reducing agent as described.

The described photosensitive component in this photothermographic material is believed to function as a catalyst for the image-forming combination. A typical concentration range of photosensitive component, especially photosensitive silver halide, in the described photothermographic element is from about 0.005 to about 0.50 moles of photosensitive silver salt per mole of oxidizing agent.

In photothermographic materials the described N- hydroxyurea reducing agents can be employed in combination with other described reducing agents, typically a substituted phenol and/or naphthol. For example, the N-hydroxyurea reducing agents can be employed in combination with bis-beta-naphthol reducing agents, such as 2,2-dihydroxy-l,l'-binaphthol, 6,6'-dibromo- 2,2'-dihydroxy-l,1-binaphthol, 6,6-dinitro-2,2-dihydroxy-1,1 -binaphthol, or naphthol)methane.

The oxidizing agent in the described oxidationreduction image-forming combination is typically a heavy metal salt oxidizing agent such as a silver salt oxidizing agent. The heavy metal salts of an organic acid are especially suitable, such as water insoluble silver salts of long-chain fatty acids which are substantially stable to light. Compounds which are silver salts of long-chain fatty acids include, for example, silver behenate, silver stearate, silver oleate, silver laurate, silver hydroxystearate, silver caprate, silver myristate and silver palmitate. Oxidizing agents which are not silver salts of carboxylic acids can be employed if desired such as silver phthalazinone, silver benzotirazole and- /or silver saccharin. Oxidizing agents which are not silver salts can be employed if desired such as gold stearate, mercuric behenate, auric behenate and the like, but silver salts are preferred.

It is often desirable to employ a so-called activator toning agent in the photothermographic elements and compositions according to the invention in order to obtain improved tone and desired image density. The described activator toning agent is suitable in a range of concentration; however, it is especially suitable in a concentration of about 0.10 moles to about 1.1 moles of activator toning agent per mole of oxidizing agent employed such as per mole of silver behenate. A typical activator toning agent which is suitable is a cyclic imide such as phthalimide, N-hydroxyphthalimide, N- potassium phthalimide, N-silver phthalimide, N- mercury phthalimide, succinimide and/or N-hydroxy succinimide. Other suitable activator toning agents include, for example, phthalazinone, 2-acetyl phthalazinone and 2-phthalylphthalazinone.

Binders can be employed in the described photothermographic materials as described. Preferred binders are hgih molecular weight materials and resins including polyvinyl butyral, cellulose acetate butyrate, polymethylmethacrylate, poly(vinyl pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and polyvinyl alcohol.

If desired, the described photosensitive silver halide in the photothermographic material according to the invention can be prepared in situ. A method of preparing photosensitive silver halide in situ in a photothermographic material is described, for example, in U.S. Pat. No. 3,457,075 of Morgan et a1. issued July 22, 1969.

Stability to print out from light exposure is increased in the described photothermographic materials typically by employing highly purified materials; for example, freedom from halides and sulfides increases stability to light exposure. The use of highly purified silver behenate can, for example, reduce propensity to print out in background areas of a photothermographic element according to the invention.

In a developing image in a photothermographic material according to the invention a range of processing temperatures is suitable. The processing temperature range is typically about 80C. to about 250C. such as for about 1 to about 60 seconds. By increasing or debis-( Z-hydroxyl creasing the length of time of heating, a higher or lower temperature within the described range can be employed.

Any suitable means can be useful providing the desired processing temperature range. The heating means can be a simple hot plate, roller or the like.

In some cases, if desired, a photothermographic element can be prepared wherein one or more components such as the described photosensitive silver halide can be in one layer and other components in other layers. For example, an element according to the invention can comprise a support, a layer containing photographic silver halide and a layer comprising the socalled oxidation-reduction image-forming combination comprising a heavy metal salt oxidizing agent as described such as silver behenate with an N-hydroxyurea reducing agent as described.

A typical so-called oxidation-reduction imageforming combination according to the invention comprises silver behenate with the described N- hydroxyurea reducing agent and an activator toning agent which is typically phthalimide or phthalazinone.

Other addenda known to be useful in photosensitive and thermosensitive elements as described in British Pat. No. 1,161,777 published Aug. 20, 1969; U.S. Pat. No. 3,152,904 of Sorenson et a1, issued Oct. 13, 1964 and U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22, 1969 can be employed in photo-thermographic materials according to the invention.

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

EXAMPLES 1-8 An N-hydroxyurea silver halide developing agent is mixed in an aqueous solution containing a 0.02 molar concentration of the N-hydroxyurea silver halide developing agent, a 0.2 molar concentration of sodium sulfite and either a 0.2 molar concentration of sodium phosphate with the pH adjusted to l 1.5 or a 0.5 molar concentration of sodium hydroxide with the pH of the solution adjusted to approximately 13.5. This provides a photosnsitive silver halide developer solution.

A photographic element containing a fine-grain silver bromoidide gelatino emulsion on a film support is sensitometrically exposed through a step wedge to tungsten light. The photographic element contains about 0.35 grams of silver per square foot of support. The resulting latent image is developed-by immersing the film in the silver halide developer solution containing the N-hydroxyurea silver halide developing agent for a seris of times at 20C. Image densities of the resulting developed image are observed. Image densities, time and fog density for each N-hydroxyurea silver halide developing agent are listed in following Table 1. Good image discrimination is obtained in each instance. The compound number in Table I and in the following examples corresponds to the compound number of the N-hydroxyurea developing agent described.

Aqueous Development -Continued Aqueous Development pH pH 1 1.5 13.5

Mini- Mini- Com- Image mum Image mum Ex. pound Time Den- Den- Time Den- Den- No. No. (min) sity sity (min) sity sity EXAMPLE 9 This is a comparative example.

The procedure set out in Example 1 is repeated with the exception that hydroxylamine sulfate is employed in place of the described N-hydroxyurea silver halide developing agent. The resulting image has a density of 1.45 in 32 minutes at a pH of 11.5.

EXAMPLES 10-16 The procedure set out in Examples 1-5, 7 and 8 are repeated with the exception that 0.002 molar concentration of 1-phenyl-3-pyraz0lidone is added to the described developer solutions. Upon processing the results observed are set out in following Table II.

The combination of silver halide developing agents provide a developed image in surprisingly reduced time and provide especially low minimum density compared to the results of Examples 18.

This example demonstrates reduced staining propensity of the N-hydroxyurea silver halide developing agents of the invention. 1-11 An alkaline solution of each of the N-hydroxyurea silver halide developing agents designated as compounds 1-1 1 are permitted to evaporate to dryness in the presence of air. The residue in each instance is almost colorless.

The procedure is repeated with the exception that hydroquinone is employed in place of the N- hydroxyurea silver halide developing agent. The residue resulting upon evaporation is intensely colored.

This procedure is also repeated employing paraaminophenol in place of the described N-hydroxyurea silver halide developing agent. Upon evaporation the resulting residue is intensely colored. This demonstrates that the N-hydroxyurea silver halide developing agents of the invention provide surprisingly reduced staining propensity compared to silver halide developing agents employed herefore.

EXAMPLES 18-25 This illustrates the use of N-hydroxyurea silver halide developing agents according to the invention in photosensitive materials for processing with heat.

A dispersion is prepared by mixing the following components:

Silveer behenate 23.3 g Behenic acid 26.0 g Polyvinyl butyral 1.25 g Sodium bromide 1.31 g Acetone-toluene (1:1 parts by 500 ml volume) This mixture is ball-milled for 18 hours and the resulting dispersion is coated on a resin coated paper support at a wet thickness of 0.004 inches. The resulting coating is permitted to dry under atmospheric conditions. Various N-hydroxyurea reducing agents as indicated in following Table III are each dissolved in a mixture of alcohol and acetone and coated on separate pieces of the resulting photosensitive element. The N- hydroxyurea silver halide developing agent is present at a concentration of 0.02 molar.

After the N-hydroxyurea reducing agent is introduced, the resulting photothermographic element is dried and exposed sensitometrically to light. The resulting image is developed by overall heating the photothermographic element on a heated metal plate at C. Images of moderate to high density are produced within about 1 to 3 seconds as indicated in following Table lll. Good density corresponds to 0.8 max, Dense corresponds to 1.0 max., Fair corresponds to 0.5 "max.

This is a comparative example.

The procedure set out in Example 18 is repeated with the exception that hydroxylamine sulfate is employed in place of the described N-hydroxyurea silver halide developing agent.

Upon exposure and overall heating, an image having almost no density is produced. The image density is very poor compared to the image density produced in each instance in Examples 18-25.

EXAMPLES 27-34 The procedure set out in Examples 18-25 are repeated with the exception that phthalazinone in a concentration of 0.7 g/g Ag. is employed in the photothermographic elements described. In each instance upon exposure and overall heating an image is developed within about 2 to 4 seconds at a processing temperature of about 140C.

EXAMPLES 3541 Table IV Ex- Comample poun Temp Time Image Minimum Image No. No. "C (sec) Density Density Tone 35 2 15 1 High High 1 15 36 3 l 15 3 High Low Neutral 37 4 1 l5 1 High Low Neutral 38 5 90 9 Good Low Neutral 39 6 l 15 High Low Neutral 40 8 l 15 2 Good Low Neutral 41 9 1 l5 7 Fair Low Neutral EXAMPLES 42-47 A photosensitive silver chloride gelatino emulsion is prepared containing 2.6 kilograms of gelatin and 2 moles of silver chloride. The silver chloride gelatino emulsion is mixed with 600 grams of gelatin, a wetting agent and one of the N-hydroxyurea silver halide developing agents as set out in following Table V. A concentration of 3.0 moles of N-hydroxyurea silver halide developing agent per mole of silver in the silver chloride gelatino emulsion is used.

The resulting silver chloride emulsion containing the N-hydroxyurea silver halide developing agent is coated on a paper support at a concentration of 0.04 grams of silver per square foot of support. After drying, the photographic element is sensitometrically exposed to tungsten light. The resulting image is developed by immersing the photographic element in an aqueous sodium hydroxide solution containing 2.0 percent by weight sodium hydroxide for 5 seconds. An image is developed in each instance as set out in following Table V. In each instance very good image discrimination is produced.

Table V Incorporation in Silver Halide Photosensitive Emulsion The procedure set out in Example 42 is repeated with the exeption that after sensitometric exposure the photographic element is heated for 10 seconds at 200C. A developed image is produced having moderate image density.

EXAMPLE 49 graphic element is heated for 10 seconds at 200C. An

image is developed having moderate density.

EXAMPLE 50 The procedure set out in Example 47 is repeated with the exception that after imagewise exposure the photographic element is heated for 10 seconds at 200C. A developed image results having moderate image density.

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.

What is claimed is:

l. A photographic processing composition comprising an alkaline development activator and an N- hydroxyurea silver halide developing agent, said N- hydroxyurea silver halide developing agent being represented by the formula:

wherein R is hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms; R is hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms; R is hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms.

2. The photographic processing composition of claim 1 wherein said N-hydroxyurea silver halide developing agent is represented by the formula:

0 R NH ii NH on wherein R is phenyl, p-methylphenyl, p-

methoxyphenyl or p-chlorophenyl.

3. The photographic processing composition of claim 1 also comprising a 3-pyrazolidone silver halide developing agent.

4. A photographic silver halide developer solution comprising an alkaline development activator, a l-phenyl-3-pyrazolidone silver halide developing agent and an N-hydroxyurea silver halide developing agent represented by the formula:

wherein R is phenyl, p-methylphenyl, methoxyphenyl or p-chlorophenyl. 4:

Claims (4)

1. A photographic processing composition comprising an alkaline development activator and an N-hydroxyurea silver halide developing agent, said N-hydroxyurea silver halide developing agent being represented by the formula:

1. A PHOTOGRAPHIC PROCESSING COMPOSITION COMPRISING AN ALKALINE DEVELOPMENT ACTIVATOR AND AN N-HYDROXYUREA SILVER HALIDE DEVELOPING AGENT, SAID N-HYDROXYUREA SILVER HALIDE DEVELOPING AGENT BEING REPRESENTED BY THE FORMULA: R1-N(-R2)-CO-N(-R3)-OH WHEREIN R1 IS HYDROGEN, ALKYL CONTAINING 1 TO 4 CARBON ATOMS OR ARYL CONTAINING 6 TO 10 CARBON ATOMS; R2 IS HYDROGEN, ALKYL CONTAINING 1 TO 4 CARBON ATOMS OR ARYL CONTAINING 6 TO 10 CARBON ATOMS; R3 IS HYDROGEN, ALKYL CONTAINING 1 TO 4 CARBON ATOMS OR ARYL CONTAINING 6 TO 10 CARBON ATOMS.

2. The photographic processing composition of claim 1 wherein said

3. The photographic processing composition of claim 1 also comprising a 3-pyrazolidone silver halide developing agent.