US3312550A - Processing photographic elements containing developing agent - Google Patents

Description

April 4, 1967 P T W ET AL 3,312,550

PROCESSING PHOTOGRAPHIC ELEMENTS CONTAINING DEVELOPING AGENT Filed Sept. 4, 1962 2 Sheets-Sheet l EXPIOSURE I SILVER HALIDE EMULSION Ea-PYRAZOLIDQNE, ALKALI STAGE I r I I SUPPORT HEAT I3 I --sII.vER IMAGE awm awyi STAGE 2 II Io SILVER I-IALIDE EMULSION WITH EXPOSURE DIAMETER OFAVERAGE GRAIN L5 MICRONS OR Lass l4 3-PYRAZOLIDONE AND ALKALI STAGE I suppom STABLE HIGH COVERINGI POWER 5 SILVER NEGATIVE IMAGE STAGE 2 I6 STABLE LOW COVERING POWER SILVER BACKGQOUND SUPPORT SILVER HALIDE EMULSION WITH DIAMETER OF AVERAGE STAGE 1 GRAIN 0.5 T0 1.5 MICRONS 3- PYRAZOLIDONE ALKALIQAND 1-PHENYL-5-MERcAPToTEmAzcILE SUPPORT I HOT MOIST AIR STABLE LOW covsrama DOWER SILVER BACK GROUND $TAGE 2 STABLE HIGH COVERING woweR SILVER POSITIVE IMAGE SUPPORT PAUL. H- STEWART GEORGE E. FALLESEN JOHN W. REEVES JR.

JNVENTORS BY ATTORNEY & AGENT April 4, 1967 H, STEWART ET AL 3,312,550

PROCESSING PHOTOGRAPHIC ELEMENTS CONTAINING DEVELOPING AGENT Filed Sept. 4, 1962 2 Sheets-Sheet 2 PAUL H. STEWART GEORGE E. FALLESEN JOHN w. QEEVES JR.

INVENTORS BY %7LWMZ 73 CM Q ATTORNEY & AGENT United States Patent 3,312,550 PROCESSING PHOTOGRAPHIC ELEMENTS CON- TAINING DEVELOPING AGENT Paul H. Stewart, George E. Fallesen, and John W. Reeves,

Jr., Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Sept. 4, 1962, Ser. No. 221,031 43 Claims. (Cl. 9663) This invention relates to photographic elements containing silver halide developing agents, methods for processing the same, and more particularly to such photo graphic elements adapted to processing with heat.

This application is a continuation-impart of Stewart, Fallesen and Reeves US. patent application Ser. No. 134,014, filed Aug. 5, 1961, now abandoned, which is a continuation-in-part of Stewart, Fallesen and Reeves U.S. Ser. No. 805,582, filed April 10, 1959, now abandoned.

A common procedure in the protographic art involves exposure of a silver halide emulsion layer to a subject followed by development of the resultant latent image with an alkaline solution of a silver halide developing agent such as hydroquinone to produce a silver image in the regions of the latent image. Fixing and washing steps customarily follow.

It has also been proposed to incorporate the silver halide developing agent into the sensitive element, for example, into the silver halide emulsion layer, in which case development of the exposed emulsion can be initiated mereby by application of an alkaline solution. It is also known that in case both the developing agent and the alkali required to activate the developing agent are present in the sensitive element, development of the emulsion can be initiated by merely applying water.

We have discovered that certain photographic elements comprising a latent image in a silver halide emulsion layer, contiguous silver halide developing agent and alkali, may be processed without use of aqueous or other liquid solutions by merely heating the element preferably in the presence of water vapor.

One object of the invention is to provide the sensitive elements adapted particularly to the dry development process of the invention, that is, development with heat in the absence of a liquid developing solution.

Another object of the invention is to provide the methods and apparatus particularly adapted to use in the dry development of the sensitive photographic elements of the invention.

Another object of the invention is to provide an element which when processed in the single step process of the invention, that is, processing in the absence of liquid processing solutions will produce stable silver images.

Still other objects will become evident from the following specification and claims.

Sensitive elements of our invention include the combination of at least one silver halide emulsion layer, a 3-pyrazolidone silver halide developing agent and an alkaline substance effective to accelerate development of a latent image in the silver halide emulsion in the presence of the developing agent. The element may further include a saccharide, particularly a nonreducing oligosaccharide, such as sucrose or raflin-ose; and preferably, as an auxiliary developing agent, an ascorbic acid or polyhydric phenol silver halide developing agent. Additional ingredients which may be present in the sensitive element are developer preservatives such as sulfite and fog reducers such as benzotriazoles. The mentioned alkaline substance, developing agent and succharide are disposed integral with the sensitive element and contiguous to the silver halide, that is, either directly in the silver halide emulsion or in an effectively adjacent colloid layer or layers. Thus, the primary developing agent, the 3- pyrazolidone compound, may be present in the silver halide emulsion and the auxiliary developing agent, alkali and saccharide in an adjacent colloid layer. Similarly, both developing agent, alkali and saccharide may be present in a layer underlying or overlying the emulsion on a support. Useful combinations of developer ingredients, include a 3-pyrazolidone developing agent as the sole developing agent, in combination with a saccharide; a 3-pyrazolidone in combination with an ascorbic acid and, if desired, a saccharide, and the combination of a 3- pyrazolidone developing agent, a polyhydric phenol developing agent, and if desired, a saccharide.

Included among the preferred sensitive elements of our invention are those which have light-sensitive emulsions with silver halide grains having diameters of 1.5 microns or less. Usually the silver halides in these emulsions are predominantly silver bromide. These emulsions are preferably free of sulfur and gold sensitizers. Such emulsions when coated without the alkali and without the developing agent at approximately 1500 square feet per mole of silver halide, on a paper support and exposed through a step wedge varying in density from 4.0 to 0.03 to a high intensity light source and then processed in a developer of the following composition:

1-phenyl-3-pyrazolidone 5.0 Sodium sulfite 6.0 Sodium metaborate, octahydrate 90.0 Ascorbic acid 27.0 Potassium bromide 2.0 Sodium thiosulfate, pentahydrate 2.0

Water to make 2 liters.

for 16 minutes at 30 C. gives a minimum reflex density less than 0.35 and a maximum density of a least 0.20 greater than the minimum density. In one embodiment, our preferred elements are used to make stable negative reproductions of an original and in another embodiment they are used to make stable positive reproductions of an original by our one step process.

The process of invention embody the steps of recording latent images in the silver halide emulsions in the presence of the developing agents and other ingredients mentioned above, followed by heating the emulsion sutficiently to develop silver images therein. In a representative procedure, a sensitive element of the invention containing a small amount of moisture is exposed to a subject, then subjected to heat by passing over a heated roller at temperatures of the order of 50 to 200 C. and speeds of the order of 10 to 200 feet per minute. As a result, a silver image is formed. In another procedure, an exposed sensitive element containing the mentioned ingredients is passed through a heated chamber so designed that moisture rising from heating of the sensitive element is confined to a relatively small space. In another procedure,

the exposed sensitive elements of the invention are processed by subjecting them to the action of hot air containing moisture in the range from a moderate amount to the amount required to saturate the air. Steam can be used to advantage. Our preferred light-sensitive elements upon exposure to a light image are developed directly to stable silver images simply by treatment in an atmosphere at least saturated with water vapor at a temperature .tiguous layer.

'a silver image in area 13 as shown in stage 2.

a; above 50 C. The silver images obtained by heat development of the other elements of our invention may be stabilized after processing so as to prevent their deterioration during storage.

The 3-pyrazolidone developing agents are essential components of the sensitive elements and are unique in their activity in the dry development process of the invention as compared to other silver halide developing agents. That is, it will be shown in the examples below that when one sensitive element containing both l-phenyl- 3-pyrazolidone and ascorbic acid and a second element containing both monomethyl-p-aminophenol and hydroquinone are exposed and heated under various conditions, only. a faint silver image is obtained in the latter element. On the other hand,.the 3-pyrazolidone-ascorbic acid system of the invention yielded a high density silver image under the same conditions of treatment.

Moreover, it is important that in addition to alkali a substantial amount of the 3-pyrazolidone developing agent be present'in the silver halide emulsion or in a con- For example, an emulsion containing no alkali and no more than about 2 grams of 3-pyrazolidone compound per mole of silver halide, upon exposure and heating yield no visible silver image. When about to 50 grams of 3-pyrazolidone compound per mole of silver halide is present, only a faint visible image is obtained upon heating in the absence of alkali. However, in the presence of strong alkali, about to grams of 3-pyrazolidone per mole of silver halide is sufiicient to produce a high density silver image upon heating the latent image. When an auxiliary developing agent such as ascorbic acid or hydroquinone is present in addition to the .S-pyrazolidone compound and a saccharide, as little as five grams of 3-pyrazolidone developing agent per mole of silver halide is sufficient. Of course, the 3-pyrazolidone-containing emulsions free of alkali may be developed with alkaline solutions, if desired containing additional developing agents as Elon and hydroquinone;

Accompanying drawings show in greatly enlarged crosssectional views, the appearance of a representative sensitive element of the invention at different stages of processing and means for heat processing the element.

In the. element of FIG. 1 of the drawings, layer 10 represents a support such as paper, synthetic resin or cellulose ester carrying a layer 11 of developer ingredients including a 3-pyrazolidone developing agent and alkali and if desired, other ingredients such as the auxiliary developing agent and a saccharide. Layer 12 is an emulsion layer such as a gelatino-silver halide emulsion layer which may contain any of the mentioned developer ingredients in addition to silver halide. As shown in the drawings, the process of the invention includes the exposure of the sensitive element to a subject to record a latent image in the silver halide in area 13 of layer 12. Thereafter, the element is heated sufliciently to develop In this process, it will be observed that when the sensitive element is heated, a visible silver image is obtained almost instantaneously. This result is facilitated by the use in the emulsion layer of silver halides which have short development induction periods, such as a fine grain silver bromide emulsion. Emulsions having longer induction periods are useful but require longer application of heat to effect their development in the processes of the invention.

In the element of FIG. 2 of the drawings, layer 10 represents a support carrying layer 14 comprising silver halide emulsion (predominantly silver bromide) with grains having an average diameter of 1.5 microns or less, a B-pyrazolidone and an alkali. As shown in the drawings, the process of the invention includes exposure of the sensitive element to a subject to record a latent image in the silver halide in area 15 of layer 14. Thereafter,

the element is treated with air at a temperature above 50 C. and at least 95% saturated with water vapor as shown in stage 2. This process results in the formation of a stable negative, comprising high covering power silver image 15 against a low covering power silver background 16.

In the element of FIG. 3 of the drawings, layer 10 is a support carrying layer 17 comprising silver halide emulsion (predominantly silver bromide) with a diameter of average grain from 0.5 to 1.5 microns, a 3-pyrazolidone, alkali, and l-phenyl-S-mercaptotetrazole. The element is exposed to an image in stage 1 and processed to a stable positive image in stage 2 by treatment with air at a temperature above 50 C. and at least saturated with water vapor. The positive image is formed consisting of stable high covering power silver in area 19 and stable low covering power silver is formed in area 18.

In FIG. 4 is illustrated one means for carrying out the heating step of the invention so as to accelerate development of the exposed photographic element and to prevent undue drying of the sheet during heating. A sensitive element 20 having a structure such as shown in stage 1 of FIG. 1 and having a support 10 of medium thickness such as a paper stock of 16 to 20 lbs. per thousand square feet, is passed around roller 21, thence over the heated roller 23, with the paper support 10 in contact with the roller 23, thence between rollers 24 and 25. The latter roller may be a roller driven at a suitable speed and pressed into contact with sheet 20 in order to draw the sheet off the supply roll, not shown, and advance it around rollers 21, 23 and 24. By arranging the rollers and advancing the paper in a manner such as shown in FIG. 4, it is possible to trap moist, warm air in the space 22 above the sheet which humid atmosphere facilitates development of the paper. A similar effect can be obtained by partially enclosing roller 23 in a manner such that the sheet is heated with its emulsion surface in, contact with warm, moist atmosphere of limited volume. 1 However, it is usually not necessary to apply moisture to the sensitive element during the heating operation and a small amount of moisture such as 510% obtainable by drying and handling the sensitive paper at about 3050% RH, is satisfactory. In a typical installation, roller 23 may be about 4 inches in diameter and heated to a temperature of about 200 C. Since the paper can be advanced at the rate of about 30 feet per minute in this apparatus and still obtain adequate development of the image, the paper does not dry out to any great extent under these conditions. Under other conditions, it may be desirable to supply moisture to the sheet during the heating step in order to obtain reproductions of optimum quality.

The pyrazolidone silver halide developing agents, such as those described below, are useful in our invention. The 3-pyrazolidone compounds having the following genera Formula I are particularly useful in. the sensitive elements a in which the various R groups represent substituents such as hydrogen, alkyl, acyl, heterocyclic or aryl groups, for example, R can be alkyl of from 1 to 12 carbon atoms, benzothiazolyl or an aryl group of the benzene or naphthalene series, substituted or not. R R R and R can be hydrogen atoms or alkyl groups of from 1 to 12 carbon atoms or aryl groups such as phenyl and naphthyl, substituted or not. Typical substituents are lower alkyl groups, including haloalkyl, pyridiniumor picolinium-N- alkyl halide, e.g., pyridinium-N-methy-l chloride, benzyl, phenyl, 4-methylphenyl, 4-methoxyphenyl, carboxylic acid acyl as acetyl, benzoyl, nitrobenzoyl and haloacyl,

.g., chloroacetyl, phenoxy and alkylphenoxy.

The 3-pyrazolidone developing agents of our invention which are used to advantage particularly with gold and sulfur sensitized silver halide emulsions are represented by the following formulas:

II R5 wherein R and R each represent a hydrogen atom or an alkyl group having from about 1 to 12 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, amyl, isoamyl, tertiary amyl, hexyl, etc.; and R represents a hydrogen atom, an alkyl group or a carboxylic acid acyl group such as methyl, ethyl, propyl, isopropyl, butyl, amyl, tertiary amyl, hexyl, chloromethyl, bromomethyl, chloroethyl, chloropropyl, pyridinium- N-methyl chloride, pyridinium-N-ethyl chloride, benzyl, etc.; or an aryl group such as phenyl, 4-methylphenyl, 4-methoxyphenyl, acetyl, dichloroacetyl, propionyl, 4-nitrobenzoyl, aryloxy such as 2,4-di-tert.amylphenoxy, and R and R represent alkyl or aryl groups such as above.

The compounds above which contain the acyl substituents R and R are particularly useful because they are developing agent precursors and are not active developing agents until the acyl group has been split ofi? in the presence of alkali. Accordingly, these acyl derivatives in which active positions of the pyrazolidone nucleus are blocked, are very useful in the emulsions especially in the higher concentrations of the order of 100 to 200 gms. per mole of silver halide. When alkali is also present in the sensitive element it may be desirable to segregate it from the acyl derivative to prevent premature release of the active form of the developing agent. The 4-alkyl and 4,4-dialkyl substituted compounds behave similarly.

The compounds are not to be confused with 5-pyrazolidones such as l-phenyl-S-pyrazolidone.

The following compounds are representative of the 3-pyrazolidone compounds useful for the purposes of our invention.

(1 1-phenyl-3-pyrazolidone (2) 1-p-tolyl-3-pyrazolidone (3) 1-phenyl-4-methyl-3-pyrazolidone (4) 1-phenyl-2-benzoyl-3-pyrazolidone (5) 1-p-chlorophenyl-3-pyrazolidone (6) 1-phenyl-5-phenyl-3-pyrazolidone (7) 1-m-tolyl-3-pyrazolidone (8) l-phenyl-S-methyl-3-pyrazolidone v (23) 1-p-diphenyl-4,4-dimethyl-3-pyrazolidone (38) 2-(pyridinium acetyl)-1-phenyl-3-pyrazolidone chloride (39) 2-(pyridinium acetyl)-4-methyl-l-phenyl-3- pyrazolidone chloride (40) 2-(pyridinium acetyl)-4,4-dimethyl-1-phenyl-3- pyrazolidone chloride (41) 3-acetoxy-1-phenyl-2-pyrazoline in equilibrium with (42) 3-acetoxy-4-methyl-1-phenyl-2-pyrazoline in equilibrium with enol acetate of 4-methyl-1-phenyl-3-pyrazolidone Compounds 1 to 12 can be prepared by the methods described in British Patents 679,677 and 679,678. Compounds 13 to 23 and 26 above are representative of 4,4- dialkyl-B-pyrazolidone compounds useful in this invention and these compounds are described in Allen et al. US. Patent 2,772,282, Nov. 27, 1956.

The w-hydroXyalkylphenyl-3-pyrazolidones in which the alkyl group preferably contains from 1 to 4 carbon atoms, for example, compounds 18 to 24 above, are described in the Allen et al. invention and in the Reynolds and Tinker U.S. Patent 2,743,279, Apr. 24, 1956.

Compound 33 was prepared as follows: 1-phenyl-3- pyrazolidone (16.2 g., 0.1 mole) and acetic anhydride (1S ml.) were heated to reflux and one drop of concentrated sulphuric acid was added. The solution was refluxed for five hours and then evaporated under reduced pressure. The residue was refluxed for one-half hour with water ml.), cooled and neutralized with concentrated ammonium hydroxide. The mixture was extracted with ethyl acetate. The solvent was removed and the residue distilled, B.P. 11931 14.93 g., 70.5% yield, M.P. 72- 4 from ethyl acetate-light petroleum (B.P. ,5565). The infrared spectrum of this material showed two carbonyl absorptions at 5.63 and 5.8 indicating that the material was the N-acetyl derivative.

Compound 34 was prepared as follows: 1-phenyl-3- pyrazolidone (5.0 g., 0.038 mole) was suspended in a solution of benzene (100 ml.) and pyridine (2.5 g., 0.30 mole) and chloroacetyl chloride (3.5 g., 0.031 mole) Was slowly added while stirring. The reaction mixture was then heated to reflux for 2 hours. After cooling, the solution was washed with water and the solvent removed to leave an oil which was recrystallized from ethyl acetate-light petroleum (B.P. 5565), M.P. 9798, 3.5

g., 47.7% yield.

The infrared spectrum of this material showed two carbonyl absorptions at 5.62,u indicating that the material was the N-acyl derivative.

Compound 35 was prepared as follows: 1-phenyl-4- methyl-3-pyrazolidone (17.6 g., 0.1 mole) and acetic anhydride ml.) were heated to reflux and one drop of concentrated sulphuric acid was added. Refluxing was continued for four hours. The excess acetic acid and acetic anhydride were removed under reduced pressure and the residue was refluxed for 30 minutes with 10 ml. water. The solution was cooled and neutralized with ammonium hydroxide and extracted with ether. The ether was removed from the extract and the residue distilled B.P. 112 12.26 g., 56% yield. The infrared spectrum of this material showed two carbonyl absorptions at 5.75,u., 5.85 indicating that the material was the N-acetyl derivative. Compounds 36 and 37 are prepared similarly.

Compound 38 was prepared as follows: 2-chloroacetyl-1-phenyl-3-pyrazolidone (6 g.) prepared as above, was dissolved in absolute ethanol (10 ml.) and ethyl acetate (25, ml.). The resulting solution was heated to reflux and an excess of pyridine added. The crystalline product separated on cooling and was collected and was recrystallized from absolute ethanol-ethyl acetate or ether. This product has a M.P. of 213-14".

Compound 39 was prepared by the same procedure just above but using 2-chloroacetyl-4-methyl-l-phenyl- 3-pyrazolidone. The 2-chloroacetyl-4-methyl-l-phenyl- 3-pyrazolidone was prepared by the procedure used for compound 34 but starting with 4-methyl-1-phenyl-3-pyrazolidone in place of 1 phenyl 3 pyrazolidone. The product compound 39, has a M.P. 22931.

Compound 40 was prepared by the procedure for compound 38 but using 2-chloroacetyl-4,4-dimethyl-1- phenyl-3-pyrazolidone which was prepared from 4,4-dimethyl-1-phenyl-3-pyrazolidone by the same method used for compound 34. Compound 40 had a M.P. 26870.

Compound 41 was prepared as follows: A suspension of 1-phenyl-3-pyr-azolidone (40 g.) in benzene (300 ml.) was heated on a steam cone. Ketene was passed in until all the material had dissolved and then for an additional one-half hour. The solvent was then removed under reduced pressure, to leave an oil which solidified on cooling. The material was recrystallized from benzene-light petroleum (B.P. 65-75) to yield a white crystalline solid M.P. 84-5 29.15 g., 58% yield.

The infrared absorption spectrum of this material showed a single carbonyl absorption at 5.72u, indicating that the material was the O-acetyl derivative.

Compound 42 was prepared as follows: 1-phenyl-4- methyl-3-pyrazolidone (25.0 g., 0.142 mole) was dissolved in refluxing benzene (300 ml.) and ketene (0.11

mole per hour) was passed in for one and one-half hours. The solvent was then removed under reduced pressure to leave an oil which was crystallized from ethyl acetatelight petroleum (B.P. 55-65"), M.P. 62.4", 11.52 g., 37.25% yield.

The infrared spectrum of this material showed a single carbonyl absorption at 5.6a, indicating that the material was the O-acetyl derivative.

Our light-sensitive elements are designed for development with conventional aqueous developer solutions or an alkaline aqueous solution containing no developing agent, which may be applied to the exposed emulsion in a conventional manner.

While the processes of the invention can be carried out with sensitive elements containing a 3-pyrazolidone silver halide developing agent as the sole developing agent, in a preferred embodiment of the invention, a 3-pyrazolidone developing agent is used in combination with ascorbic acid silver halide developing agent, such as dand l-ascorbic acids, d-arabo ascorbic acid, iminogluco-ascorbic acid and other ascorbic acids having the formulas shown in James et al. US. Patent 2,688,549, grant-ed Sept. 7, 1954. Alternately, the 3-pyrazolidone developing agents are employed in combination with a polyhydric phenol silver halide developing agent such as hydroquinone, catechol, 4-phenylcatechol or pyrogallol. As mentioned previously, when a 3-pyrazolidone is used in combination with these auxiliary developing agents, appreciably less of the 3-pyrazolidone compound is required in the sensitive element to maintain high development activity and thus produce the silver images with a minimum of heating of the exposed emulsion layer. An added eflect of 4-phenylcatechol in combination with a 3-pyrazolidone developing agent is that the permanence of the print obtained upon heat development is improved. That is, the residual silver halides show less tendency to print-out upon exposure to light than in the case when the 3-pyrazolidones are used as the developing agent in the sensitive element.

The saccha-rideshave previously been employed in a sensitive element in order to improve the stability of the emulsion upon againg for extended periods of time. However, in the present invention one unexpected effect of the saccharides, especially of the non-reducing oligosaccharides such as sucrose and raffinose, results from their ability to enhance the development activity of the 3-pyrazolidone developing agents, alone or in combination with the auxiliary developing agents. Thus, in the presence of a s-aocharide, much less of the 3-pyrazolidone compound need be used in the sensitive elements to maintain high development activity. Representative saccharides which may be used are: fructose, glucose, inulin, melecitose, pectin, raffinose, starch, sucrose and trehalose. The non-reducing oligosaccharides such as sucrose and raffinose are especially useful.

Non-reducing has a meaning herein usually applied to saecharides and means that the compounds are members of the class of saccharides which do not reduce alkaline solutions of salts of metals such as copper salts,-as present in Fehlings solution, as compared to reducing sugars like fructose.

Latent images in the preferred light-sensitive elements of our invention having emulsions with silver halide grains with diameters of 1.5 microns or less and containing predominantly silver bromide and which have the specific sensitometric characteristics described before :in terms of D and the differences between D, and D are developed directly to stable images by treatment in an atmosphere at least saturated with water vapor at a temperature above 50 C. The silver halide grains in these elements when processed as described are substantially all converted to silver. The image formed is com prised of high covering power silver with a low covering power silver background. These images are stable as formed since there is substantially no residual silver halide. These preferred elements give direct stable negative images. It is believed that the exposed areas are chemically developed to form the black high covering power filamentary silver while the unexposed areas are solution physically developed to form hexagonal crystals of silver, approximately 50 to 200 millimicrons in diameter. Where the hexagonal silver crystals range in size from approximately 80 to 100 millimicrons, the background color appears greenish when viewed by reflected light. Covering power decreases and image tone becomes progressively lighter and browner as silver particles approach a diameter of approximately 150 to 200 millimicrons. We have found that stable direct positive images are produced by relatively coarser grained emulsions, that is when the grain diameter is from 0.5 to 1.5 microns and heterocyclic mercaptan compounds or aromatic mercaptan compounds, such as mercaptotetnazoles, meroaptobenzoxazoles, mercaptobenzothiazoles, toluene thiols, and the like, are added to the silver halide emulsion, and the exposed elements are processed in air saturated with mois ture at 99 C. for one to several minutes. The meroaptotetrazoles, e.g., 1-phenyl-5-mercaptotetrazole are preferred. By adding sodium thiosulfate (usually 50l00 g. per mole of silver halide) in addition to the l-phenyl-S- mercaptotetrazole, a stable positive print is obtained in approximately 30 seconds with some increase in D occurring.

In our preferred elements which are developed directly to stable prints, the rate of print stabilization may be increased in many ways known to increase the rate of solution physical development, e.g., silver halide solvent (such as sodium thiosulfate, etc.), solvent transfer nuclei and development accelerators as coating addenda. Adding solvent transfer-type nuclei, such as yellow colloidal silver, zinc sulfide or reduced silver formed by solution physically developing a portion of the silver halide grains prior to or during coating, increased the print stabilization rate approximately three times. Development accelerators (e.g., u-picolinium-B-phenylethyl bromide or dodecyl pyridinium-p-toluene sulfonate) also increase print stabilization rate by approximately three times.

Latent images in the other light-sensitive elements of our invention give photographic reproductions (as a direct result of heating of the alkaline emulsions containing a 3-pyrazolidone developing agent) comprising silver images and residual unreduced silver halide which is capable of being subsequently exposed and developed by heat in the same manner. That is, after forming one image in the emulsion layer by means of the exposure and heat development steps, the residual emulsion may be re-exposed and redeveloped with heat any number of times until the unexposed and undeveloped emulsion has been exhausted. Accordingly, the sensitive elements can be used for posting items at various times and heat developing emulsion at a convenient time after the entry has been made. Since the prints obtained in the process will usually contain some residual silver halide and developing agent, they should not be subjected to light and moisture for any prolonged period of time, otherwise appreciable density will appear in the background regions. If it is desired to prevent formation of this background density, this may be accomplished by treating the prints with a desensitizing agent, an antifoggant, acid or other compound inhibiting development of the silver halide. For example, this may be accomplished by dusting the compound onto the surface of the print and steaming the print to cause the compound to penetrate the emulsion. The following compounds are represenative of those suitable for this purpose: 6-chloro-4-nitrobenzotriazole, 5-chlorobenzotriazole, B-methylbenzothiazolium methylsulfate, a mixture of 6-chloro-4-nitrobenzotriazole and sulfamic acid. It has also been found that mercaptans (e.g., thiosalicylic a'cid, 1-phenyl-5-mercaptotetrazole) present either in the emulsion layer, or contiguous to the emulsion layer, can serve as post-exposure stabilizers. Such compounds do not materially improve the stability of the unexposed product,

10 however, they do serve as post-exposure stabilizers since after exposure and heat processing of the sensitive elements under the conditions described, the mercaptans appear to react with the residual silver halide to form a much less light-sensitive silver salt than the original silver halide.

Useful amounts of the various ingredients in the sensitive elements can be ascertained from the following examples although optimum quantities should be ascertained under the particular conditions in use. However, 3- pyrazolidone compound such as l-phenyl-3-pyrazolidone may be used in amounts in excess of about 20 grams per mole of silver halide and when in combination with an auxiliary developing agent such as ascorbic acid or hydroquinone, an amount in excess of about 5 grams per mole of silver halide should be used. Quantities of the 3-pyrazolidones in excess of about 50 grams per mole of silver halide may be difficult to disperse in many silver halide emulsions. However, somewhat larger amounts of from about 50-to 200 grams per mole of silver halide can be used. The saccharides may be used in combination with the pyrazolidones in amounts ranging from about 30 to 1000 grams per mole of silver halide. If too large a quantity is used, crystallization occurs or the emulsion tends to be tacky, depending upon the particular saccharide used. The auxiliary developing agents such as the ascorbic acids may be used in combination with the 3-pyrazolidones in amounts of the order of about 30100 grams per mole of silver halide and the polyhydric phenol developers such as hydroquinone in the range .of about 15 to 75 grams per mole of silver halide. However, at the higher levels of concentration, the latter developing agent tends to produce more background stain in the prints than desired.

The following examples will serve to illustrate .our invention.

Example 1 Sample 1.-48 grams of a 20% gelatin solution were added to 500 cc. of the following solution.

Water to make 1.0 liter.

The mixture was then coated upon a baryta-coated photographic paper base at a coverage of about 8 grams of solution per square foot. The alkaline layer was then overcoated with a gelatino-silver bromoiodide emulsion (94.5 mole percent silver bromide, 5.5 mole percent of silver iodide) containing 50 grams of I-phenyl-B-pyrazolidone and 320 grams .of sucrose per mole of silver at a coverage of approximately 475 square feet per mole of silver.

Sample 2.A coating similar to that of Sample 1 was prepared except omitting the sucrose from the emulsion. Samples 1 and 2 were processed fresh by exposure under a step tablet and passing the samples over a metal surface heated at 200 C. at a rate of 20 feet per minute in an apparatus similar to that described on page 39, line 13. Sample 1 had an image having a maximum density of 1.65 and Sample 2, a maximum density of 1.60. When Samples 1 and 2 were incubated eight days at F., and 35% relative humidity, the maximum density obtainable in Sample 1 was 1.60 and in Sample 2, only 0.76. When Sample 1 was aged six months and Sample 2 for three months, at 75 F. and 50% relative humidity, the respective maximum densities obtained were 1.54 (Sample 1) 0.52 (Sample 2).

The effect of sucrose in stabilizing the developing agent in the coated element is thus apparent from these data.

It is interesting to note that the sensitive elements of the invention containing silver halide in combination with a 3-pyrazolidone developing agent and alkali are developable with heat under a wide range of conditions, i.e., as mentioned above, when the emulsions are conditioned at 35% relative humidity, the emulsions develop readily upon heating. Even when the sensitive elements are conditioned at 17% or lower relative humidity, the emulsions develop readily upon heating regardless of the fact that a comparatively small amount of moisture is present.

Processors similar to that described on page 39, line 13, were also used in the following Examples 2, 3, 4, 5, 6, 8, 9 and 11.

Example 2 A coating was made on a paper support in the manner of Example 1, except that 48 grams of 20% gelatin solution were added to 500 cc. of the following composition:

Grams l-phenyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45.0 Hydroquinone 12.0 Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0 S-methyl-benzotriazole .02

Water to make 1 liter.

This was coated on .a paper support at 8 grams of solution per square foot followed by the bromoiodide emulsion free of developing agent coated at 475 square feet per mole of silver. Upon exposing the coating and heat developing at 200 C. a maximum density of 1.60 was obtained in the fully exposed areas.

Example 3 A gelatino bromoiodide emulsion (94.5% silver bromide, 5.5% silver iodide) was coated on a paper base at 475 square feet per mole of silver. This emulsion layer was then overcoated with a composition consisting of 48 'grams of 20% gelatin solution added to 500 cc. of the following developer solution:

Grams l-phenyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45 .0 Ascorbic acid 13.5 Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0 S-methylbenzotriazole 0.2

Water to make 1 liter.

An exposed sample of the coating when developed as described at 200 C. gave a maximum density of 1.40.

Example 4 The inability of the 3-pyrazolidone developing agents to develop a useful image in silver halide in the absence of alkali even when the developing agent is present in high concentrations is illustrated by this example.

Three gelatin solutions each containing 1-phenyl-3-pyrazolidone were coated on a paper base and each coating then overcoated with a bromoiodide emulsion at 475 square feet per mole of silver, so as to obtain coverages of 2, 10 and 50 grams of 1-phenyl-3-pyrazolidone per mole of silver. When these coatings were exposed and heat developed at 200 C. only the coating containing 50 grams of l-phenyl-3-pyrazolidone per mole of silver showed any image at all and this was extremely faint. At the 2 and 10 gram levels no image was visible.

Similar coatings prepared by adding 2, 10 and 50 grams of 1-phenyl-3-pyrazolidone per mole of silver to the bromoiodide emulsion yielded images of very low density and then even only at the highest concentration (50 grams of pyrazolidone per mole of silver).

1 2 Example 5 48 grams of 20% gelatin solution were added to 500 cc. of the following composition:

Grams 1-phenyl-4,4-dimethyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45.0 Ascorbic acid 13.5 Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0 S-methylbenzotriazole .02

Water to make 1 liter.

The solution was coated on a paper base and the resulting coating then overcoated with a bromoiodide emulsion at 475 square feet per mole of silver. Upon heat development at 200 C. of the exposed emulsion, a maximum density of 1.4 was obtained.

Example 6 A dispersion was prepared of a mixture of 46 grams of 4-phenyl-catechol, 69 grams of di-n-butylphthalate, 460 grams of 10% gelatin solution and 23 cc. of 15% saponin solution. This was added to an unhardened gelatin silver bromoiodide emulsion containing one mole of silver halide and the emulsion coated on a paper support which had previously been coated with a gelatin layer containing sodium carbonate. Upon heat development of the coating by passing through a chamber heated at 200 C. and at a rate of 10 feet per minute for about one second imagewise tanning development occurred and washing in water removed unexposed areas. A maximum density of 1.4 was obtained in the fully exposed regions and 0.06 in the unexposed regions.

Example 7 A silver bromoiodide emulsion was prepared containing a mixture of monomethyl-p-aminophenol sulfate and hydroquinone developing agents by diluting 48 grams of a 20% gelatin solution with 208 cc. of water and adding to 300 cc. of the following developer composition:

Water cc 500 Monomethyl-p-aminophenol sulfate "grams" 4.5 Sodium sulfite, anhydrous do 45.0 Hydroquinone do 12.0 Sodium carbonate monohydrate do 80.0 Potassium bromide do 2.0

Water to make 1 liter.

This composition was then coated upon a photographic paper base at a coverage of 8 grams of solution per square foot. .The layer was then overcoated with a gelatino-siler bromoiodide emulsion (94.5% silver bromoiodide, 5.5 mole percent silver iodide) at a coverage of 475 square feet per mole of silver. A comparable emulsion was prepared by the following procedure: 96 grams of 20% gelatin solution were added to one liter of a 1- phenyl-3-pyrazolidone-ascorbic acid developer solution, given in Example 3 above, and the mixture coated on a baryta-coated paper base at a coverage of about 9 grams per square foot. This layer was then overcoated with the above emulsion at 475 square feet per mole of silver halide. When the papers were exposed and heat processed by passing them over a surface heated at 200 C., at speed of 10 and 12 feet per minute, the highest maximum density obtainable in the first paper was 0.30 whereas the 1-phenyl-3-pyrazolidone-ascorbic acid paper of the invention yielded densities as high as 1.20 under the same conditions of treatment.

Example 8 Coatings were prepared as described in Example 2 except that the hydroquinone in the developer composition was replaced by 13.5 grams per liter of d-araboascorbic acid or 15.5 grams per liter of iminoglucoascorbic acid. When the samples were heat processed at 200 C. passing 13 over the heated surface at 20 feet per minute, they yielded maximum densities of 1.65 and 1.66 respectively.

Example 9 50 grams of sucrose in 48 grams of 20% gelatin solution were added to 500 cc. of the following developer composition and coated on a photographic paper base at 9.0 grams of solution per square foot:

Grams 1-phenyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45.0 Sodium ascorbate 15.0 Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0 S-methylbenzotriazole 0.02

Water to make 1.0 liter.

The developer layer was then overcoated with a gelatinosilver bromoiodide emulsion containing approximately 94.5 mole percent AgBr and 5.5 mole percent AgI at a coverage of approximately one mole of silver per 475 square feet. A similar coating containing no sucrose was prepared as a control. Additional coatings were prepared in the same manner except replacing the sucrose by the following:

Grams Fructose 25 Raflinose 50 Inulin 25 Melezitose 25 Trehalose 50 The coatings were exposed and heat developed at 200 C. with the results shown in the following table:

max. Sample Fresh 8 days 1 16 days 1 3 mo.

Control.. 1. 60 0.3 Sucrose 1. 62 1. 60 Fructos 1.60 1. 08 Raffinose- 1. 60 1. 62 InulirL 1. 60 1. 58 Melezitose. 1. 70 l. 56 Trehalose 1. 60 1.68

Example 10 In a less preferred process a direct positive photographic paper comprising a fogged silver chloride emulsion was immersed briefly in a solution of 100 cc. water, 100 cc. methanol, 2 g. l-phenyl-3-pyrazolidone and 10% triethanolamine followed by drying. An exposed silver halide emulsion layer was placed in contact with the paper containing the alkaline developer composition and heated between metal surfaces at 180 F. for about one second, resulting in the development of a silver image in the exposed emulsion layer.

Example 11 A fine grain gelatin-o silver bromoiodide emulsion (94.5 mole percent AgBr and 5.5 mole percent AgI) containing 320 g. sucrose, 162 g. ascorbic acid, 90 g. l-phenyl- 3-pyrazolidone, 36 g. Na SO 540 g. sodium metaborate, octahydrate, 12 g. KBr, 178 g. lphenyl mercaptotetrazole and 40 g. NaOH per mole silver halide was coated on single weight paper at a coverage of approximately 1300 sq. ft./ mole silver handle. A strip of the coating exposed and processed by passing over a heated surface as described in Example 1 at 150 C. at a paper speed of about 7 ft. per minute gave a stable print having a D of 0.96 and 0.03 density in the unexposed areas. Similar coatings in which the l-phenyl- S-mercaptotetraz-ole was replaced with either mercaptobenzoxazole, or p-toluene t'niol also produce stable prints.

When the developer is added directly to the silver halide emulsion layer, it is sometimes advantageous to add the developer solution to the emulsion just prior to coating. This can be done by using a procedure similar to that described in Collins et al. U.S. Patent 2,912,343.

Example 12 A negative speed sulfur and gold salt sensitized bromoiodide emulsion preparation was divided into aliquot portions and solutions of the following developing agents added just before coating. Each of the preparations was coated on a light-weight paper in an amount equivalent to 200 mg. Ag per ft. and dried. After sensitometric exposure, the papers were developed 25 seconds at 32 C. in a developer having the following composition:

Grams p-Methylaminophenol sulfate 2.2 Hydroquinone 8.8 Sodium sulfite, anhydrous 72.0 Sodium carbonate, anhydrous 48.0 Potassium bromide 4.0

Water to 1 liter.

then fixed, washed, and dried. Relative speeds were measured at reflection densities of 0.1 above fog.

The following Table I lists the relative speeds, fogs, and reflection D values for the control emulsion and each of the emulsions containing 3-pyrazolid0ne developing agents.

TABLE I Developing Agent Incorporated Into Rela- Reflec- Emulsion 20 g./mole silver tive Fog tion Speed Dim;

Control 0. 02 1.16 l-phenyl-3-py1azolidone 200 0. 06 1. 21 l-phenyl-Z-chloroaeetyl-3-pyrazolidone 152 0. 03 1. 18 1-phenyl-2-ch1oroacetyl-4-methyl-3-pyrazolidone 0. 03 1. 20 1-phenyl2-acetyl-3-pyraz0lidone 100 O. 04 1. 20 1-phenyl-2-acetyl-4-methyl-3-pyrazolidone.. 100 0. 02 1.18 Enol acetate of l-phenyl-3-pyrazolidone. 166 0. 02 1. 20 Enol acetate of 1-phenyl-4-methyl-3-pyrazolidone 159 0. 02 1. 2O 4-methyl-l-phenyl-3-pyrazolidone 0. 03 1; 20

Another identical set of coatings containing the 3-pyrazolidones of Table I were incubated 8 days at 120 F.

and 35% RH. with the result that the coatings containing the 3-pyrazolidone derivatives substituted by acyl and acetoxy radicals in the 2- and 3-positions and alkyl in the 4-position of the nucleus were found to be most stable.

This example illustrated the development properties of the 2- and 3-acyl and 4-alkyl substituted 3-pyrazolidones, which as mentioned are eflicacious for use in emulsions, particularly those sulfur and gold sensitized, since the acyl derivatives do not become effective as developing agents until the acyl radical is split off in the presence of alkali. The 4-alkyl derivatives behave similarly. Alkali can be added to these sensitive elements preferably in a layer effectively separate from the acyl derivative, and the elements subjected to heat development by the method described in Example 1.

Example I 3 A high speed sulfur and gold salt sensitized silver I bromoiodide emulsion was prepared and coated in the normal fashion. Portions of this emulsion, containing to modulate the infrared exposure.

1. 5 the 3-pyrazolidones listed in the Table II were coated on a paper support. Samples of each coating were exposed on an intensity scale sensitometer, processed for 25 seconds in the developer used. in Example 12 at 32 C., fixed,

16 Example 14 A gelatino silver bromoiodide emulsion consisting of silver halide grains having a diameter of approximately washed and dried with the following results. 5 50 millimicrons containing 320 g. of sucrose was coated TABLE 11 Amount of De- Developing Agent Incorporated veloping Relative Fog Din.

Into Emulsion Agent, Speed gJmole silver Control 100 0. 02 1.13 l-phenyl-3-pyrazolidone 20 166 0. 02 1. 19 4-methyl-l-phenyl-3-pyrazolidone 13. 3 138 0. 02 l. 18 20. 166 0. 02 1. 17 H1 26. 7 121 O. 4 irnethyl-lhenyl-3- azolidone 13.3 1 8 0.

p pyr 20.0 152 0. 04 1.18 1- -(2-hydroxyethylphenyDl-3- pyrazolidoue 13. 3 132 0- 04 l- 5 20. 0 132 0.05 1. 18 26. 7 152 0.06 1. 18

When samples of these emulsions were incubated for 8 days at 120 F. and 35% R.H., it was noted that the emulsions containing the 4-methyl and 4,4-dimethyl substituted compounds were substantially more stable. Additional 3-pyrazolidone derivatives have general Formulas II and 111 above, and particularly compounds 32 to 41, may be used in the emulsions sensitized with sulfur compounds and the gold salts such as mentioned below, to obtain improved stability arising out of this particular emulsion sensitizing in combination with the 3-pyraz-olidones unsubstituted in the 5 -position but substituted in the 2-, 3- and 4-positions of the pyrazolidone nucleus.

A single element paper readily developable with heat may be prepared by coating a silver halide emulsion on a suitable paper support and then overcoating the silver halide emulsion layer with a solution of 400 ml. methanol, 40 g. of Aerosol OT (dioctyl ester of sulfosccinic acid), and 10 g. of 1 phenyl-3-pyrazolidone followed by drying. This paper, after exposure, is readily developable by applying to it a uniformly heated surface (250-3 00 F.) for several seconds. A further paper readily developable with heat may be made by impregnating an emulsion with a solution of 12.5 g. l-phenyl-3-pyrazolidone, 1.0 g. thiosalicylic acid, 12.5 cc. phenylhydrazine and 1000 cc. methyl alcohol.

The processes of the invention are further applicable to use with sensitive elements comprising .a support such as paper, upon the support a gelatin layer of alkaline developer ingredients such as used in Example 1, Sample 1, and over that alkaline layer the gelatino-silver halide-3- pyrazolidone-sucrose layer to which has been added a quantity of wax such as paraffin and a dye suitable for carrying out the therm-ographic exposure step described below. The sensitive element is exposed to a subject then subjected to heat under conditions such as described in Example 1 in order to develop a silver image in the exposed areas. Thereafter the element is placed with the emulsion side in contact with a thin sheet of absorbent paper and exposed to infrared radiations, with the result that the wax in the region of the silver image melts and transfers with the dye to the absorbent sheet yielding a dye image of the subject thereon. In this process the amount of silver halide in the emulsion layer may be extremely small since only a faint silver image is needed Thus the mentioned emulsion of Example 1 coated over the alkaline layer can contain as little as 1 mole of silver halide per 5000 or more square feet of coating surface.

The following examples will serve to illusrate the preferred elements of our invention and their processing with heated air at least 95% saturated with water vapor to produce stable prints.

on single weight paper stock at a coverage of approximately 1600 ft. /mole of silver as silver halide. The emulsion layer was then overcoated with a solution consisting of 48 g. of a 20% gelatin solution and 500 ml. of a 1-phenyl-3-pyrazolidone, ascorbic acid developer having the composition:

1-phenyl-3-pyrazolidone 2.5 Sodium sulfite 45.0 Ascorbic acid 13.5 Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0 Water to make 1 liter.

at a coverage of approximately 9.0 g. per ft. A strip of the coating, when imagewise exposed and subjected to air saturated with moisture at 95 C. for 15 seconds, gave a legible print having a dense black image on a brown background of relatively low density. The print was dry to the touch. Exposing to 50 ft.-c. illumination for one hour under high relative humidity conditions (90 percent R.H. at F.) did not alter the appearance of the print. A strip of the coating was exposed by means of an intensity scale sensitometer, processed as described in this example, and the resulting image density measured with a reflection densitometer. The log exposure at a density of 0.8 was 2.50, Dmax, 1.33 and D 0.60.

Example 15 A gelatino silver bIOtl'IlOlOdldC emulsion consisting of silver halide grains having a diameter of approximately 50 millimicrons containing the following materials per Sodium metaborate, octahydrate 540.0 Potassium bromide 12.0

Was coated on a single weight paper at a coverage of approximately 1500 ftF/m'ole of silver halide. A strip of the coating when imagewise exposed and processed as described in Example 14 gave a legible print having a black image on a light brown background. The log exposure at a density of 0.8 was 2.52, D 1.48 and D like 0.40. Another element like this was made but with a faster gelatino silver bromoidide emulsion containing silver halide grains with diameters of approximately 250 millimicrons. This was exposed, processed and its image densities measured as described. The log exposure at a den y f 0.8 was 0.39, D,,,,,, 1.30 and D,,,,,, 0.38.

A gelatino silver bromoiodide emulsion consisting of silver halide grains having a diameter of approximately 1.5 microns containing the following materials per mole of silver halide:

Sucrose 640.0 Ascorbic acid 162.0 1-pheny1-3-pyrazolidone 30.0 Sodium sulfite 36.0

Sodium metaborate, octahydrate 540.0 Potassium bromide 12.0 1-phenyl-5-mercaptotetrazole 10.0

was coated on single-weight paper stock at a coverage of approximately 1600 ft. per mole of silver halide and then air dried. A similar coating was made in which the l-phenyl-S-mercaptotetrazole was omitted. An imagewise exposed strip of the coating containing the l-phenyl- S-mercaptotetrazole, when subjected to air saturated with moisture at 99 C. for 2 minutes, gave a legible direct positive print with a D of 0.71 and D of 1.21. The coating which contained no 1 phenyl 5 mercaptotetrazole when exposed and processed in a similar manner for 15 seconds gave a legibile negative print with a D of 0.52 and a D of 1.06. Exposing both prints to 30 ft.-c. illumination for one hour under high relative humidity conditions (90% R.H., 75 F.) did not alter the appearance of the print.

Another element like this was made but in which 100 g. of sodium thiosulfate per mole of silver halide was also included along with the 1-phenyl-5-mercaptotetrazole. An irnagewise exposed strip of this element when subjected to air saturated with moisture at 99 C. for 30 seconds gave a legible stable positive print with a D of 1.64 and D of 0.76. Exposure of the print to actinic light under elevated temperature and humidity as described above did not alter the prints appearance.

The elements of Examples 14, 15 and 16 have been processed to stabilized prints by treatment with air saturated with water vapor at temperatures as low as 50 C. The following table lists the temperatures and processing times used to advantage.

TABLE III Approximate processing time, minutes Water vapor saturated air temperature, C.:

The type elements illustrated by Examples 14, 15 and 16 are processed to advantage by passing the light exposed element through hot moist air which is at least about 95% saturated with water vapor for the required time. The water vapor may be supplied in any convenient way, for example as steam, or water vapor fi'om the element itself if contained in a heated enclosed processor of the type described by Stewart et al. in Photographic Science and Engineering, vol. 5, No. 2, Part 1 of 2 parts, March-April 1961, page 113. We have found that such a processor operating with a paper travel speed of approximately 15 feet per minute will process our preferred elements to advantage.

Our stable prints can be copied with the immediate elements or with office copy materials that are used conventionally.

The alkaline materials present in the sensitive elements together with the developing agents include inorganic alkalies such as sodium metaborate, octahydrate, sodium hydroxide and sodium carbonate. Organic alkaline materials such as quaternary ammonium bases and salts can be used although the inorganic alkalies which do not yield volatile bases upon heating, are preferred.

The elements and processes of the invention have been described with respect to ordinary developing emulsions. If desired, sensitive elements containing direct reversal emulsions and the 3-pyrazolidone compounds may be used in a similar manner.

The photographic emulsions used in practicing our invention are of the developing-out type.

The emulsions can be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard U.S. Patent 1,574,944, Sheppard and Punnett U.S. Patent 1,623,499, and Sheppard and Brigham U.S. Patent 2,410,689.

The emulsions can also. be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium, and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller, Collins and Dodd U.S. Patent 2,399,083 or stabilized with gold salts as described in Damschroder U.S. Patent 2,597,856 and Yutzy and Leermakers U.S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850), polyamines, such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925), or bis(fi-aminoethyl)sulfide and its Water-soluble salts (Lowe and Jones U.S. Patent 2,251,926).

The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker U.S. Patent 1,846,301, 1,846,302, and 1,942,854; White U.S. Patent 1,990,507; Brooker and White U.S. Patents 2,112,140, 2,165,338, 2,493,747, and 2,739,964; Brooker and Keyes U.S. Patent 2,493,748; Sprague U.S. Patents 2,503,776 and 2,519,001; Heseltine and Brooker U.S. Patent 2,666,761; Heseltine U.S. Patent 2,734,900; Van Lare U.S. Patent 2,739,149; and Kodak Limited British Patent 450,958. 1

The emulsions can also be stabilized with the mercury compounds of Allen, Byers, and Murray U.S. Patent 2,728,663; Carroll and Murray U.S. Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665; the triazoles of Heimbach and Kelly U.S. Patent 2,444,608; the azaindenes of Heimbach and Kelly U.S. Patents 2,444,605 and 2,444,606; Heimbach U.S. Patents 2,444,607 and 2,450,397; Heimbach and Clark U.S. Patent 2,444,609; Allen and Reynolds U.S. Patents 2,713,541 and 2,743,181; Carroll and Beach U.S. Patent 2,716,062; Allen and Beilfuss U.S. Patent 2,735,769; Reynolds and Sagal U.S. Patent 2,756,147; Allen and Sagura U.S. Patent 2,772,164, and those disclosed by Birr in the Z. wiss. Phot. 47, 2 (1952); the quaternary benzothiazolium compounds of Brooker and Stand U.S. Patent 2,131,038; and the zinc and cadmium salts of Jones U.S. Patent 2,839,405 and the'isothiourea derivatives of the Herz and Kalenda U.S. applicaber 15, 1960, of Milton and Murray; an ester of an ethylene bis-glycolic acid such as ethylene bis(methyl glycolate) (as described in U.S. Patent 2,904,434 of Milton); bis- (ethoxy diethylene glycol) succinate as described in U.S. Patent 2,940,854 of Gray or a polymeric hydrosol as results from the emulsion polymerization of a mixture of an amide of an acid of the acrylic acid series, and acrylic acid ester and a styrene-type compound as described in U.S.

;Patent 2,852,386 of Tong. The plasticizer may be added to the emulsion before or after the addition of a sensitizing dye, if used.

The emulsion may be hardened with any suitable hardener for gelatin such as formaldehyde; a halogen-substituted aliphatic acid such as mucobromic acid as described in U.S. Patent 2,080,019 of White; a compound having a plurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,2) 7 octene 2,3,5,6-tetracarboxylic dianhydride, or a dicarboxylic or a disulfonic acid chloride such as terephthaloyl chloride or naphthalene-1,5-disulfonyl chloride as described in U.S. Patents 2,725,294 and 2,725,- 295 of Allen and Carroll; a cyclic 1,2-diketone such as cycl-opentane-1,2-dione as described in U.S. Patent 2,725,- 305 of Allen and Byers; a bisester of methanesulfonic acid such. as 1,2-di-(methanesulfonoxy)ethane as described in U.S. Patent 2,726,162 of Allen and Laakso; -1,3-dihydroxyrnethylbenzimidazole-2-one as described in U.S. Patent 2,732,316 of July, Knott and Pollak; a dialde- Jeffrey's et al. U.S. Ser. Nos. 822,444, 822,445, and 822,-

446, all filed June 24, 1959.

The emulsions may have been supplied with a coating aid such as saponin; a lauryl or oleyl monoether of polyethylene glycol as described in U.S. Patent 2,831,766 of Knox and Davis; a salt of a sulfated and alkylated polyethylene glycol ether as described in U.S. Patent 2,719,087 "of Knox and Davis; an acylated alkyl taurine such as the sodium salt of N-oleoyl-N-methyl taurine as described in U.S. Patent 2,739,891 of Knox, Twardokus, and-Davis; the reaction product of a dianhydrideof tetracarboxybutane with an alcohol or an aliphatic amine con- .taining from 8 to 18 carbon atoms which is treated with a base, for example, the sodium salt of the monoester of tetracarboxybutane as described in U.S. Patent 2,843,487 of Knox, Stenberg and Wilson; a water-soluble maleopimarate or a mixture of a water-soluble maleopimarate and a substituted glutamate salt as described in U.S. Patent 2,823,123 of Knox and Fowler; an alkali 'metal salt of a substituted amino acid such as disodium N-(carbo-p-tert. octylphenoxypentaethoxy)glutamate as described in U.S. application Serial No. 600,679 of Knox and Wilson; or a sulfo-succinamate such as tetrasodium 'N-(1,2-dicarboxyethyl)-N-octadecyl sulfosuccinamate or N-laury1 disodium sulfosuccinamate as described in U.S.

Patent 2,992,108 of Knox and Stenberg.

In the preparation of the silver halide dispersions employed for preparing silver halide emulsions there may be employed as the dispersing agent for the silver halide in its preparation, gelatin or some other colloidal material such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound. Some colloids which may be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in U.S. Patent 2,286,215 of Lowe; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 1926% as described in U.S. Patent 2,327,808 of Lowe and Clark, a water-soluble ethanolamine cellulose acetate as described in US. Patent 2,322,085 of Yutzy; a polyacrylamide having a combined acrylamide content of 30-60% 'and a specific viscosity of 0.251.5 or an imidized polyacrylamide of like acrylamide content and viscosity as described in U.S. Patent 2,541,474 of Lowe, .Minsk and Kenyon; zein as described in U.S. Patent 2,563,791 of Lowe; a vinyl alcohol polymer containing urethane carboxylic acid groups'of the type described in U.S. Patent 2,768,154 of Unruh and Smith, or containing cyano-acetyl groups such as the vinyl alcoholvinyl cyanoacetate copolymer as described in U.S. Patent 2,808,331 of Unruh, Smith and Priest; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in U.S. Patent 2,852,382 of I11- ingsworth, Dann and Gates.

If desired, compatible mixture of two or more of these colloids may be employed for dispersing the silver halide in its preparation. Combinations of these antifoggants, sensitizers, hardeners, etc., may be used.

It may be advantageous, in some instances, to use as the photographic emulsion support a paper base having a thin metal foil, e.g. aluminum, laminated to it. The foil appears to cut down loss of heat and moisture from the region of development.

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 eifected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A light-sensitive, unexposed photographic element comprising a support having thereon a silver halide emulsion layer and contiguous to the said silver halide, an alkaline material and at least about 5 g./mole of silver halide of a 3-pyrazolidone selected from those having the formulas:

.wherein R represents a member selected from the class consisting of hydrogen, and anacyl' group; R1 represents a substituent selected from the class consisting of an alkyl group having from 1 to 12'carbon atoms, a benzothiazolyl group and an aryl group; and R R R and R each represent a substituent selected from the class consisting of hydrogen, an alkyl group havingfrom 1 to 12 carbon atoms and an aryl group; R represents a group selected from the class consisting of an alkyl group having from 1 to 12 carbon atoms, and an aryl group; and R represents a group selected from the class consisting of an alkyl group having from 1 to 12 carbon atoms and an aryl group; and an auxiliary developing agent selected from the class consisting of a polyhydric phenol and an ascorbic acid developing agent and when none of said auxiliary developing agent is present, at least about 15 g./mole of silver halide of said 3-pyrazolidone' silver halide developing agent, said element containing a small amount of moisture that is suflic'ient to develop a latent image in said silver halide to a silver image upon heat ing to a temperature above about 50 C,

21 2. A photographic element of claim 1 containing contiguous to the silver halide a saccharide.

3. A photographic element of claim 1 containing contiguous to the silver halide a non-reducing oligossaccharide.

4. A photographic element of claim 1 in which the 3- pyrazolidone is l-phenyl-3-pyrazolidone.

5. A photographic element of claim 1 containing at least about 15 g./mole of silver halide of an auxiliary developing agent.

6. A photographic element of claim 1 containing contiguous to the silver halide a saccharide and at least about 30 g./mole of silver halide of ascorbic acid.

7. A photographic element of claim 1 containing contiguous to the silver halide a non-reducing oligosaccharide and at least about 30 g./mole of silver halide of ascorbic acid.

8. A photographic element of claim '1 containing contiguous to the said silver halide sucrose and at least 30 gm/mole of silver halide of ascorbic acid.

9. A photographic element of claim 1 containing contiguous to the silver halide a saccharide and at least about 15 g./mole of silver halide of a polyhydric phenol.

10. A photographic element of claim 1 containing contiguous to the silver halide a non-reducing oligosaccharide and at least about 15 g./mole of silver halide of hydroquinone.

11. A photographic element of claim 1 containing contiguous to the silver halide, sucrose and at least 15 g./ mole of silver halide of hydroquinone,

12. A photographic element of claim 1 wherein the alkaline material and developing agent are present in a layer between the emulsion layer and the support.

13. A photographic element of claim 1 wherein the alkaline material and developing agent are present in a layer overlying the emulsion layer.

14. A photographic element of claim 1 wherein the alkaline material is present in a layer between the emulsion layer and support, and the developing agent is present in the emulsion layer.

15. A photographic element of claim 1 wherein the alkaline material and developing agent are present in the emulsion layer.

16. A photographic element of claim 1 containing contiguous to the silver halide at least about 30 g./mole of silver halide of a non-reducing oligosaccharide.

17. A photographic element of claim 1 containing a mercaptan.

18. A photographic element of claim 1 in which the silver halide emulsion is a sulfur and gold sensitized silver halide emulsion.

19. A photographic element of claim 1 in which the silver halide emulsion is a sulfur and gold sensitized silver halide emulsion and the 3-pyrazolidone developing agent is selected from the class consisting of 1-phenyl-4- methyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazoli- ,done, 1 phenyl 2 acetyl 3 pyrazolidone, 3-acetoxyl-phenyl-Z-pyrazoline, the enol acetate of 1-phenyl-3- pyrazolidone, 3-acetoxy-4-methyl-1-phenyl-2-pyrazoline and the enol acetate of 4-methyl-1-phenyl-3-pyrazolidone.

20. A photographic element of claim 1 wherein the alkali is sodium metaborate, octahydrate.

21. A photographic element of claim 1 having contiguous to the silver halide a non-reducing oligosaccharide and in which the alkali is sodium metaborate octahydrate.

22. A photographic element of, claim 1 containing a mercaptotetrazole and in which the silver halide emulsion has silver halide grains having an average diameter in the range from approximately 0.5 to 1.5 microns and the silver halide is predominately silver bromide.

23. A photographic element of claim 1 containing a mercaptotetrazole and an alkali metal thiosulfate and in which the silver halide grains have an average diameter in the range from approximately 0.5 to 1.5 microns and the silver halide is predominately silver bromide.

24. A photographic element of claim 1 that contains ascorbic acid and in which the silver halide emulsion has silver halide grains having an average diameter of less than approximately 1.5 microns and the silver halide is predominately silver bromide.

25. A photographic element of claim 1 that contains ascorbic acid and sodium thiosulfate and in which the silver halide emulsion has silver halide grains having an average diameter of less than approximately 1.5 microns and the silver halide is predominately silver bromide.

26. A photographic element of claim 1 that contains an organic cyclic mercaptan compound and in which the silver halide emulsion has silver halide grains having an average diameter in the range from approximately 0.5 to 1.5 microns and in which the silver halide is predominately silver bromide.

27. A photographic element of claim 1 in which the silver halide emulsion has silver halide grains having an average diameter of less than approximately 1.5 microns and the silver halide is predominately silver bromide.

28. A light-sensitive, unexposed photographic element comprising a support having thereon a silver halide emulsion layer and contiguous to the said silver halide, an alkaline material and at least about 5 g./mole of silver halide of a 3-pyrazolidone selected from those having the formulas:

ing from 1 to 12 carbon atoms, and an aryl group; and

R represents a group selected from the class consisting of an alkyl group having from 1 to 12 carbon atoms and an aryl group; and an auxiliary developing agent selected from the class consisting of a polyhydric phenol and an ascorbic acid developing agent and when none of said auxiliary developing agent is present, at least about 15 g./mole of silver halide of said 3-pyrazolid0ne silver halide developing agent, said element containing a small amount of moisture that is suflicient to develop a latent image in said silver halide to a stable silver image upon heating to a temperature above about 50 C., the silver halide in said emulsion layer having grains with an average diameter of less than approximately 1.5 microns, the silver halide being predominately silver bro- -mide, and the said silver halide emulsion being such that when coated without the alkali and without the developing agent at approximately 1500 square feet per mole of silver halide on a paper support and exposed through a step wedge varying in density from 4.0 to 0.3 to a high intensity light source and then processed in a developer of the following composition:

, Grams 1-phenyl-3 -pyrazolidone 5.0 Sodium sulfite 6 0 Sodium metaborate :0

Ascorbic acid 27.0 Potassium bromide 2.0 Sodium thiosulfate, pentahydrate 2.0

Water to make 2.0 liters.

for 16 minutes at 20 C. gives a minimum reflex density less than 0.35 and a maximum density of at least 0.20 greater than the minimum density.

29. A light-sensitive, unexposed photographic element of claim 28 in which the support is paper.

30. A photographic process which comprises applying a sufiicient amount of heat to a photographic element containing a small amount of moisture including a silver halide emulsion layer containing a latent image, integral and contiguous thereto an alkaline material and at least about g. per mole of silver halide of a 3-pyrozolidone silver halide developing agent, to develop a silver image in the emulsion layer the said small amount of moisture being sufiicient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

31.- A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, a saccharide, and at least about 5 g. per mole of silver halide of a 3-pyrazolidone silver halide developing agent, and applying a sufficient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being suflicient to develop a latent image in said silverhalide to a silver image upon heating toa temperature above about 50 C.

32. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, nonreducing oligosaccharide, and at least about 5 g. per mole of silver halide of a 3-pyrazolidone silver halide developing agent, and applying a sufiicient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being suflicient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

33. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, nonreducing oligosaccharide, and at least about 5 g. per mole of silver halide of 1-phenyl-3-pyrazolidone, and applying a suflicient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being suificient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

34. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, at least about 15 g. per mole of silver halide of a silver halide developing agent of the class consisting of polyhydric phenol and ascorbic acid developing agents, and at least about 5 g. per mole of silver halide of a 3-py-razolidone silver halide developing agent, and applying a sufiicient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being suflicient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C. 35. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, a saccharide, at least about 30 g. per mole of silver halide of an ascorbic acid, and at least about 5 g. per mole of silver halide of a 3-pyrazolidone silver halide developing agent, and applying a sufiicient amount of heat to said exposed element containing a small amount or moisture to develop a silver image in-the emulsion layer the said small amount of moisture being sufiicient to develop a latentimage in said silver halide to a silver image upon heating to a temperature above about 50 C.

36. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, a nonreducing oligosaccharide, at least about 30 g. per mole of silver halide of an ascorbic acid, and at least about 5 g. per mole of silver halide of a 3-pyrazolidone silver halide developing agent, and applying a sufiicient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being sufficient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

37. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, sucrose, at least about 30 g. per mole of silver halide of an ascorbic acid, and at least about 5 g. per mole of silver halide of 1-phenyl-3-pyrazolidone, and applying a sufiicient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being sufficient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

38. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, a

saccharide, at least about 15 g. per mole of silver halide of a polyhydric phenol silver halide developing agent, and at least about 5 g. per mole of silver halide of a 3- pyrazo-lidone silver halide developing agent, and applying a sufi'lcient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being sufficient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 5 0 C.

39. A photographic process which comprising exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, a non-reducing oligosaccharide, at least about 15 g. per mole of silver halide of a polyhydric phenol silver halide developing agent, and at least about 5 g. per mole of silver halide of a 3-pyrazoliclone silver halide developing agent, and applying a suflicient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being sufiicient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

40. A photographic process which comprises exposing to a subject a photographic element including a silver halide emulsion layer, contiguous alkaline material, sucrose, at least about 15 g. per mole of silver halide of hydroquinone, and at least about 5 g. per mole of silver halide of 1-phenyl-3-pyrazolidone, and applying a sufficient amount of heat to said exposed element containing a small amount of moisture to develop a silver image in the emulsion layer the said small amount of moisture being sufiicient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C.

41. The process of claim 30 wherein the application of heat is effected by passing the element over a heated roller.

42. A photographic process which comprises exposing a light-sensitive photographic element containing a small amount of moisture, said element comprising a support having thereon a sulfur and gold sensitized silver halide emulsion and integral and contiguous to the silver halide at least about 5 g. per mole of silver halide of a 3-pyrazolidone silver halide developing agent, and an alkaline compound, said small amount of moisture being sufficient to develop a latent image in said silver halide to a silver image upon heating to a temperature above about 50 C., and heat developing the exposed emulsion.

43. The process of claim 42 wherein the developing agent is a member of the class consisting of l-phenyl-4- 25 methyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 1 phenyl 2 acetyl 3 -pyrazo1id0ne, 3 acetoxy 1 phenyl 2 pyrazoline, the enOl acetate of lphenyl 3 pyrazo-lidone, 3 acetoXy 4 methyl 1- phenyl-2-pyrazoline and the enol acetate of 4-methy1-1- pheny1-3-pyraz0lidone.

References Cited by the Examiner UNITED STATES PATENTS 2,592,368 4/1952 Yackel 96-95 2,624,674 1/ 1953 Tarkington et a1 96-108 2,751,300 6/1956 James et al. 96-66 2,855,299 10/1958 Rogers 9629 3,022,168 2/1962 Stjarnkvist 96-66 26 3,062,648 11/1962 Crawford 9676 3,088,824 5/1963 Jacobs 96-63 3,248,219 4/1966 Jacobs 96--66 OTHER REFERENCES Weyde, E. abstract of Belgian Patent No. 586,348 (1- 1959). Published in Ansco Abstract 1444 Ha.

Gareis, et al., abstract of Belgian Patent No. 599,383 (1-1960). Published in Ansco Abstract 1412.1Ib. 10 Inagaki, K., abstract of Japanese Patent No. 176,111.

Published in Chem. Abstr. 45, 4590 (6-1951).

NORMAN G. TORCHIN, Primary Examiner.

A. D. RICCI, C. E. DAVIS, Assistant Examiners.

@2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 31 2,550 Dated Paul H. Stewart, George E. Fallesin Inventm-(s) and John W. Reeves, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 22, lines 2? through 33, in the righthand structural formula, that portion reading SEALED DEZ2 1969 Amt:

Eanrdunetchml WILLIAM E. SGHUYLER, JR.

Attesting Officer Oomissioner of Patents L J

Claims (1)

1. A LIGHT-SENSITIVE, UNEXPOSED PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT HAVING THEREON A SILVER HALIDE EMULSION LAYER AND CONTAGIOUS TO THE SAID SILVER HALIDE, AN ALKALINE MATERIAL AND AT LEAST ABOUT 5 G./MOLE OF SILVER HALIDE OF A 3-PYRAZOLIDONE SELECTED FROM THOSE HAVING THE FORMULAS:

Images