Red and infrared films containing either 5-thio-1,2,3,4-thiatriazoles and 5-oxy-1,2,3,4-thiatriazoles or 5-substituted-thio-1,2,3,4-thiatriazoles and 5-substituted-oxy-1,2,3,4-thiatriazoles

Abstract: 5-substituted-thio-1,2,3,4-thiatriazoles and 5-substituted-oxy-1,2,3,4-thiatriazoles have been found to be supersensitizers for silver halide photographic emulsions spectrally sensitized to the red and infrared regions of the electromagnetic spectrum.

Description: FIELD OF INVENTION This invention relates to photographic elements, particularly to infrared and red sensitive elements, and more particularly to compounds useful in 1) supersensitizing and 2) improving the keeping properties of the coated infrared and red sensitive materials. BACKGROUND OF THE INVENTION In most uses of silver halide in photographic materials, it is desirable to increase the speed or sensitivity of the emulsion. There are a number of different techniques for increasing the speed of an emulsion which are usually classified as chemical sensitization or spectral sensitization. Chemical sensitization usually involves modification of the silver halide grains to make the most efficient use of the radiation that they absorb. The three general types of chemical sensitization are sulfur sensitization, reduction sensitization, and precious (noble) metal sensitization. These methods of chemical sensitization are well known and firmly established in the art (e.g., James, T. H. and Vanselow, W. "Chemical Sensitization", J. Photo. Sci., 1, 133 (1953), Frieser, H. and Ranz, E., Ber. der Bunsengesellschaft, 68, 389 (1964), and Pouradier, J. "Chemical Sensitization", Photographic Theory: Liege Summer School, A. Hautot, p. 111, Focal Press (London 1963). Spectral sensitization enables grains to benefit from radiation in regions of the electromagnetic spectrum where the silver halide would ordinarily not absorb. Dyes which absorb radiation and can transfer energy to the grains to help in the photoreduction of silver ions to clusters of silver metal are conventionally used to effect spectral sensitization. Another phenomenon associated with the use of spectral sensitizing dyes is known in the art as supersensitization. The addition of other substances, frequently in quantities ranging from less than an equivalent molar rate to a 100 fold molar excess of supersensitizer to dye, can increase the spectrally sensitized speed of the emulsion by more than an order of magnitude. Some supersensitizers are dyes themselves, but many others do not absorb radiation in significant amounts in the visible portion of the electromagnetic spectrum. Therefore, the effect of supersensitizers on spectral sensitization is not clearly dependent on the ability of compounds to absorb radiation in the visible portion of the spectrum. Certain cyanines, merocyanines compounds analogous to cyanines, certain acylmethylene derivatives of heterocyclic bases, and ketone derivatives such as p-dimethylaminobenzalacetone are known supersensitizers. An expanded selection of supersensitizers is therefore desired. Silver halide emulsions can be protected against the production of fog and stabilized against the loss of sensitivity during keeping. Suitable antifoggants and stabilizers which can be used alone or in combination, include triphenylphosphines, amines, arsines, bismuthines, and stibildynes taught in US-A-4,578,347; the thiazolium salts described in Staud, US-A-2,131,038 and Allen, US-A-3,694,716; the azaindenes described in Piper, US-A-2,886,437 and Heimbach, US-A-2,444,605; the mercaptotetrazoles described in Kendall et al., US-A-2,403,977, Kennard et al., US-A-3,266,897 and Luckey et al., US-A-3,397,987; and the oximes described in Carroll et al., GB-A-623,448. With respect to infrared sensitive emulsions, GB-A-2,140,928 describes the use of heterocyclic indolinium dyes to maintain stability. However, it is well known in the prior art that infrared sensitive photographic materials exhibit poor keeping properties (Neblette's Handbook of Photography and Reprography, 7th. Edition, Ed. Sturge, Pub. Van Nostrand). Even with the above mentioned additives, it has not been possible to maintain adequate stability of an infrared sensitive emulsion. As a consequence, many infrared sensitive photographic materials stipulate refrigeration, and put limitations on storage humidity in order to extend the shelf-life as much as possible. Patents and literature related to supersensitization are listed below. US-A-2,875,058 describes the use of triazines such as Leucophor BCF to supersensitize infrared sensitized silver halide emulsions. US-A-4,596,767 describes the use of certain heterocyclic salts to supersensitize infrared sensitized silver halide emulsions. US-A-4,677,053 shows silver halide emulsions spectrally sensitized to the infrared by quinoline dyes which are supersensitized with diazines or triazines. Dye precursors and polyethylene oxide are also used with the supersensitizer. US-A-4,030,927 and US-A-4,105,454 describe red and infrared sensitive emulsions which are supersensitized by halogen substituted benzotriazoles and benzotriazole compounds, respectively. US-A-3,592,656 describes the supersensitization of merocyanine dye sensitized silver halide emulsions with heterocyclic compounds selected from pyrazoles, 5-pyrazolones, 3-pyrazolones, 3,5-pyrazolidenediones, triazoles, tetrazoles, xanthines, imidazoles, imidazolidines, and imidiazolinium salts. US-A-3,457,078 describes the use of mercapto substituted oxazine, oxazole, thiazole, thiadiazole, imidazole or tetrazole as supersensitizers in combination with certain cyanine dyes. US-A-3,637,393 describes the use of mercaptotetrazoles in combination with certain hydroquinone compounds to reduce fog and increase speed in photographic emulsions. US-A-4,536,473 describes the use of water soluble bromides for increased speed and improved shelf life of infrared photographic materials. Akhmedzyanov et al., Zhurnel Nauchnio i Prikadnoi Fotografi i Kinematograffi 14 (2), 148-149 (1969) and 12 (6), 462-463 (1967), and Demchuk et al., Zhurnel Prikadnoi Specktrosk., 33 (3), 557 (1980), describe the use of triphenylphosphine as a supersensitizer and stabilizer for infrared sensitive silver halide. US-A-4,603,104 describe additive IR supersensitization by combining arylmercaptotetrazoles, triazine stilbenes and poly(ethylacrylate). US-A-59,932 and US-A-154,293 describe the use of amine thiatriazoles and quaternary ammonium and phosphonium salts respectively for increased speed and improved shelf life of infrared photographic materials. By incorporating thio or oxy thiatriazoles into silver halide emulsions or the protective topcoat, improvements have been obtained in photographic speed and in the keeping properties of the materials. SUMMARY OF THE INVENTION Silver halide emulsions which have been spectrally sensitized to the red or infrared regions of the electromagnetic spectrum show improved sensitivity and aging characteristics with the addition of thio or oxy thiatriazoles. A further extension of the invention is a combination of thio or oxy thiatriazoles or a combination of the thio or oxy thiatriazoles with other supersensitizing classes. DETAILED DESCRIPTION OF THE INVENTION Silver halide crystals have an inherent photosensitivity only in the ultraviolet and blue regions of the electromagnetic spectrum. In order to provide the crystals with sensitivity to other portions of the electromagnetic spectrum, dyes are used. These dyes which extend the range of sensitivity of the silver halide are generally referred to as spectral sensitizing dyes. As noted above, supersensitizers increase the efficiency of these spectral sensitizing dyes. Traditionally, emulsions which have been spectrally sensitized to the red or infrared regions of the spectrum have been sensitized inefficiently. The relative sensitivities of red or infrared sensitized emulsions tend to be lower than the relative sensitivities of emulsions spectrally sensitized to the visible regions of the spectrum. The need for supersensitizers in the red or infrared is therefore considered to be generally very important. The addition to red or infrared sensitized silver halide photographic emulsions of compounds of formula (I) or (II): wherein R¹ may be a cationic element (Na⁺, K⁺, NH₄⁺, etc.) a proton (H), an acyl (acalkyl), alkyl, allyl, aryl, or aralkyl group, or any combination thereof; R² may be an acylene (acylalkylene), allylene, alkylene, arylene or aralkylene group; X may be an oxygen or sulfur, or any combination thereof, will increase sensitivity and/or improve the shelf life of the coated materials. R¹ may also be a 5- or 6-membered heterocylic group having only C, N, S or O ring atoms and R² may be the corresponding 5- or 6-membered heterocyclic divalent linking group having only C, N, S, or O ring atoms. Preferably R¹ is phenyl and R² is phenylene. Examples of compounds include, but are not limited to, the following: Formula (I) T1 5-Thio-1,2,3,4-thiatriazole, sodium salt T2 5-(4-Chlorobenzoylthio)-1,2,3,4-thiatriazole T3 5-(4-Cyanobenzoylthio)-1,2,3,4-thiatriazole T4 5-Phenylacetylthio-1,2,3,4-thiatriazole T5 5-Napthoylthio-1,2,3,4-thiatriazole T6 5-Triphenylmethanethio-1,2,3,4-thiatriazole T7 5-(4-Methylbenzoylthio)-1,2,3,4-thiatriazole T8 5-Ethanoylthio-1,2,3,4-thiatriazole T9 5-Butanoylthio-1,2,3,4-thiatriazole T10 5-Hexanoylthio-1,2,3,4-thiatriazole T11 5-Nonanoylthio-1,2,3,4-thiatriazole T12 5-Steroylthio-1,2,3,4-thiatriazole T13 5-Benzylthio-1,2,3,4-thiatriazole T14 5-Methylthio-1,2,3,4-thiatriazole T15 5-Ethoxy-1,2,3,4-thiatriazole T16 5-Phenoxy-1,2,3,4-thiatriazole Formula (II) T17 5-Glutaroyldi(thio-1,2,3,4-thiatriazole) These types of compounds are added to the optically sensitized emulsions or to the topcoat in any of the conventional methods by which supersensitizers or other adjuvants are added to photographic emulsions. Typically the supersensitizing compounds are added to the emulsion mixture just prior to coating, mixed well, then coated onto the photographic substrate. There is accordingly provided in another embodiment of the invention a photosensitive element comprising a substrate having adhered to at least one surface thereof a layer comprising the supersensitized photographic emulsion of the present invention. In the photosensitive element either said supersensitizing 5-thio-or oxy-1,2,3,4-thiatriazole or said supersensitizing 5-substituted thio- or oxy-1,2,3,4-thiatriazole is preferably present in a protective layer adjacent to the emulsion layer and further from the substrate than the emulsion layer. The supersensitising compounds are added as aqueous solutions, aqueous dispersions, or organic solvent solutions (e.g. methanol) alone, or with other desirable adjuvants. The compounds may be added in any effective supersensitizing amount to the photographic emulsion or topcoat. The concentration of ingredients and materials can vary significantly in photographic emulsions such as from 0.5 to 10 g/m² for silver. The supersensitizers may also vary significantly in concentration. A generally useful range would be from 0.0001 to 2.0 percent by dry weight of the supersensitizer to the total silver halide emulsion layer. This would generally comprise 0.001 to 20% by weight of the silver halide in the photographic emulsion layer. A more preferred range would be from 0.01 to 10% for the total supersensitizer combination by weight of the silver halide or 0.001 to 1.0% total dry weight of the coated emulsion layer. An extension of the present invention is a combination of the thio or oxy thiatriazoles with an additional compound as described below: (1) two or more thio or oxy thiatriazoles, (2) a thio or oxy thiatriazole and an amino thiatriazole, (3) thio or oxy thiatriazole and an arylmercaptotetrazole, and (4) a thio or oxy thiatriazole with other supersensitizers. The arylmercaptotetrazoles useful in the practice of the present invention are defined by the formula in which Ar is an aryl group, preferably a phenyl group. The aryl or phenyl group may or may not be substituted as with alkyl, alkoxy, phenyl, fused benzyl (to form naphthyl groups), halogen (e.g., chloro-, bromo-, fluoro-, and iodo-), amino, sulfonic acid, and carboxyl groups as described in U.S. Patent No. 3,457,078. The amino thiatriazoles useful in the practice of the present invention are defined by the formula wherein R is selected from the group consisting of alkyl (preferably of 1 to 12 carbon atoms, more preferably of 1 to 4 carbon atoms), aryl (preferably phenyl and substituted phenyl, more preferably p-substituted phenyl, with examples of preferred substituents being selected from the class consisting of halogen (e.g. Br and Cl), hydroxyl, alkyl (e.g. of 1 to 12 carbon atoms, preferably 1 to 4 carbon atoms), alkoxy (e.g. of 1 to 12 carbon atoms, preferably of 1 to 4 carbon atoms), fused aromatic rings (to form naphthyl groups or substituted naphthyl groups with substituents preferred similar to those used with R equals substituted aryl)), allyl, and 5- or 6-membered heterocyclic rings composed of C, S, N, and O atoms, with at least one carbon atom. Any red or infrared spectral sensitizing dye may be used in the practice of the present invention with the supersensitizing compounds of the present invention. Useful dyes for this purpose tend to be merocyanines, cyanines, dicarbocyanine and especially tricarbocyanines. Such dye sensitizers for the infrared are described for example in U.S. Patent Nos. 3,457,078, 3,619,154, 3,682,630, 3,690,891, 3,695,888, 4,030,932 and 4,367,800. The preferred classes of compounds are the tricarbocyanines such as the 3,3'-dialkylthiatricarbocyanines, thiatricarbocyanines (especially with rigidized chains), selenotricarbocyanines, and enamine tricarbocyanines. Useful red sensitizing dyes include 4-quinoline, carbocyanine, dicarbocyanine and merocyanine dyes. Preferred classes of dyes according to the present invention are represented by the following general formula (Ia), (IIa), or (IIIa): wherein: R⁰ and R¹ can be a substituted alkyl group or a nonsubstituted alkyl having from 1 to 8 carbon atoms such as, for example, methyl, ethyl, propyl, butyl, amyl, benzyl, octyl, carboxymethyl, carboxyethyl, sulfopropyl, carboxypropyl, carboxybutyl, sulfoethyl, sulfoisopropyl and sulfobutyl groups; X⁻ is any acid anion such as, for example, chloride, bromide, iodide, perchlorate, sulfamate, thiocyanate, p-toluenesulfonate and benzenesulfonate; Z⁰ and Z¹ are independently the non-metallic atoms necessary to complete an aromatic heterocyclic nucleus chosen within those of the thiazole series, benzothiazole series, [1,2-d]-naphthothiazole series, [2,1-d]-naphthothiazole series, oxazole series, benzoxazole series, selenazole series, benzoselenazole series, [1,2-d]-naphthoselenazole series, [2,1-d]-naphthoselenazole series, thiazoline series, 4-quinoline series, 2-pyridine series, 4-pyridine series, 3,3-dialkyl-indolenine series (wherein alkyl has a meaning known to those skilled in the art including alkyl groups having 1 to 12 carbon atoms), imidazole series and benzimidazole series. More particularly and preferably, the present invention refers to dyes of the type (Ia) and (IIa) above indicated in which both heterocyclic nuclei are of the benzothiazole series. The preferred dyes of the type (IIIa) above in the present invention would be where both heterocyclic nuclei are of the benzoxazole series. R² and R³ each represent a hydrogen atom, or an alkyl group having 1 to 5 carbon atoms such as a methyl group or an ethyl group; R⁴ represents a hydrogen atom, a halogen atom, a hydroxy group, a carboxy group, an alkyl group having 1 to 5 carbon atoms, an unsubstituted or substituted aryl group, or an acyloxy group shown by wherein R⁵ represents an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a substituted phenyl group. k, l, m, and n are 0 to 1. Q represents chloride or bromide. p is 0, 1, 2, or 3. Any of the various types of photographic silver halide emulsions may be used in the practice of the present invention. Silver chloride, silver bromide, silver iodobromide, silver chlorobromide, silver chlorobromoiodide and mixtures thereof may be used for example. Any configuration of grains, cubic orthorhombic, hexagonal, epitaxial, lamellar, tabular or mixtures thereof may be used. These emulsions are prepared by any of the well-known procedures, e.g., single or double jet emulsions as described by Nietz et al., US-A-2,222,264, Illingsworth, US-A-3,320,069, McBride, US-A-3,271,157 and US-A-4,425,425 and US-A-4,425,426. The silver halide emulsions of this invention can be unwashed or washed to remove soluble salts. In the latter case the soluble salts can be removed by chill-setting and leaching or the emulsion can be coagulation washed e.g., by the procedures described in Hewitson et al., US-A-2,618,556; Yutzy et al., US-A-2,614,928; Yackel, US-A-2,565,418; Hart et al., US-A-3,241,969; and Waller et al., US-A-2,489,341. Photographic emulsions in accordance with this invention can be sensitized with chemical sensitizers, such as with reducing agents; sulfur, selenium or tellurium compounds; gold, platinum or palladium compounds; or combinations of these. Suitable chemical sensitization procedures are described in Shepard, US-A-1,623,499; Waller, US-A-2,399,083; McVeigh, US-A-3,297,447; and Dunn, US-A-3,297,446. The silver halide emulsions of this invention can contain speed increasing compounds such as polyalkylene glycols, cationic surface active agents and thioethers or combinations of these as described in Piper, US-A-2,886,437; Chechak, US-A-3,046,134; Carroll et al., US-A-2,944,900; and Goffe, US-A-3,294,540. Silver halide emulsions of this invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers which can be used alone or in combination, include the thiazolium salts described in Staud, US-A-2,131,038 and Allen US-A-2,694,716; the azaindenes described in Piper, US-A-2,886,437 and Heimbach, US-A-2,444,605; the mercury salts described in Allen, US-A-2,728,663; the urazoles described in Anderson, US-A-3,287,135; the sulfocatechols described in Kennard, US-A-3,235,652; the oximes described in Carrol et al., GB-A-623,448; nitron; nitroindazoles; the polyvalent metal salts described in Jones, US-A-2,839,405; the thiuronium salts described in Herz, US-A-3,220,839; and the palladium, platinum and gold salts described in Trivelli, US-A-2,566,263 and Damschroder, US-A-2,597,915. Silver halide grains in accordance with the invention can be dispersed in colloids that can be hardened by various organic or inorganic hardeners, alone or in combination, such as the aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfones, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed function hardeners and polymeric hardeners such as oxidized polysaccharides, e.g., dialdehyde starch, oxyguargum, etc. Photographic emulsions according to the present invention can contain various colloids alone or in combination as vehicles or binding agents. Suitable hydrophilic materials include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives (e.g., phthalated gelatin), cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water soluble polyvinyl compounds, e.g., poly(vinylpyrrolidone) acrylamide polymers or other synthetic polymeric compounds such as dispersed vinyl compounds in latex form, and particularly those which increase the dimensional stability of the photographic materials. Suitable synthetic polymers include those described, for example, in US-A-3,142,568 of Nottorf; US-A-3,193,386 of White; US-A-3,062,674 of Houck, Smith and Yudelson; US-A-3,220,844 of Houck, Smith and Yudelson; Ream and Fowler, US-A-3,287,289; and Dykstra, US-A-3,411,911; particularly effective are those water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, those which have cross linking sites which facilitate hardening or curing and those having recurring sulfobetaine units as described in CA-A-774,054. Emulsions in accordance with this invention can be used in photographic elements which contain antistatic or conducting layers, such as layers that comprise soluble salts, e.g., chlorides, nitrates, etc., evaporated metal layers, ionic polymers such as those described in Minsk, US-A-2,861,056 and US-A-3,206,312 or insoluble inorganic salts such as those described in Trevoy, US-A-3,428,451. Photographic emulsions of the invention can be coated on a wide variety of supports. Typical supports include polyester film, subbed polyester film, poly(ethylene terephthalate) film, cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polycarbonate film and related 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, ethylenebutene copolymers and the like. Emulsions of the invention can contain plasticizers and lubricants such as polyalcohols, e.g., glycerin and diols of the type described in Milton, US-A-2,960,404; fatty acids or esters such as those described in Robijns, US-A-2,588,765 and Duane, US-A-3,121,060; and silicone resins such as those described in DuPont GB-A-955,061. The photographic emulsions as described herein can contain surfactants such as saponin, anionic compounds such as the alkylarylsulfonates described in Baldsiefen, US-A-2,600,831 fluorinated surfactants, and amphoteric compounds such as those described in Ben-Ezra, US-A-3,133,816. Photographic elements containing emulsion layers as described herein can contain matting agents such as starch, titanium dioxide, zinc oxide, silica, polymeric beads including beads of the type described in Jelley et al., US-A-2,992,101 and Lynn, US-A-2,701,245. Emulsions of the invention can be utilized in photographic elements which contain brightening agents including stilbene, triazine, oxazole and coumarin brightening agents. Water soluble brightening agents can be used such as those described in Albers et al., DE-A-972,067 and McFall et al., US-A-2,933,390 or dispersions of brighteners can be used such as those described in Jansen, DE-A-1,150,274 and Oetiker et al., US-A-3,406,070. Photographic elements containing emulsion layers according to the present invention can be used in photographic elements which contain light absorbing materials and filter dyes such as those described in Sawdey, US-A-3,253,921; Gaspar, US-A-2,274,782; Carroll et al., US-A-2,527,583 and Van Campen, US-A-2,956,879. If desired, the dyes can be mordanted, for example, as described in Milton and Jones, US-A-3,282,699. Contrast enhancing additives such as hydrazines, rhodium, iridium and combinations thereof are also useful. Photographic emulsions of this invention can be coated by various coating procedures including dip coating, air knife coating, curtain coating, or extrusion coating using hoppers of the type described in Beguin, US-A-2,681,294. If desired, two or more layers may be coated simultaneously by the procedures described in Russell, US-A-2,761,791 and Wynn, GB-A-837,095. The silver halide photographic elements can be used to form dye images therein through the selective formation of dyes. The photographic elements described above for forming silver images can be used to form dye images by employing developers containing dye image formers, such as color couplers, as illustrated by GB-A-478,984; Yager et al., US-A-3,113,864; Vittum et al., US-A-3,002,836, US-A-2,271,238 and US-A-2,362,598. Schwan et al. US-A-2,950,970; Carroll et al., US-A-2,592,243; Porter et al., US-A-2,343,703, US-A-2,376,380 and US-A-2,369,489; Spath GB-A-886,723 and US-A-2,899,306; Tuite US-A-3,152,896 and Mannes et al., US-A-2,115,394, US-A-2,252,718 and US-A-2,108,602, and Pilato US-A-3,547,650. In this form the developer contains a color-developing agent (e.g., a primary aromatic amine which in its oxidized form is capable of reacting with the coupler (coupling) to form the image dye. Also, instant self-developing diffusion transfer film can be used as well as photothermographic color film or paper using silver halide in catalytic proximity to reducable silver sources and leuco dyes. The couplers may be present either directly bound by a hydrophilic colloid or carried in a high temperature boiling organic solvent which is then dispersed within a hydrophilic colloid. The colloid may be partially hardened or fully hardened by any of the variously known photographic hardeners. Such hardeners are free aldehydes (US-A-3,232,764), aldehyde releasing compounds (US-A-2,870,013 and US-A-3,819,608), s-triazines and diazines (US-A-3,325,287 and US-A-3,992,366), aziridines (US-A-3,271,175), vinylsulfones (US-A-3,490,911), carbodiimides, and the like may be used. The dye-forming couplers can be incorporated in the photographic elements, as illustrated by Schneider et al. Die Chemie , Vol. 57, 1944, p. 113, Mannes et al. US-A-2,304,940, Martinez US-A-2,269,158, Jelley et al. US-A-2,322,027, Frolich et al. US-A-2,376,679, Fierke et al. US-A-2,801,171, Smith US-A-3,748,141, Tong US-A-2,772,163, Thirtle et al. US-A-2,835,579, Sawdey et al. US-A-2,533,514, Peterson US-A-2,353,754, Seidel US-A-3,409,435 and Chen Research Disclosure, Vol. 159, July 1977, Item 15930. The dye-forming couplers can be incorporated in different amounts to achieve differing photographic effects. For example, GB-A-923,045 and Kumai et al. US-A-3,843,369 teach limiting the concentration of coupler in relation to the silver coverage to less than normally employed amounts in faster and intermediate speed emulsion layers. The dye-forming couplers are commonly chosen to form subtractive primary (i.e., yellow, magenta and cyan) image dyes and are non-diffusible, colorless couplers, such as two and four equivalent couplers of the open chain ketomethylene, pyrazolone, pyrazolotriazole, pyrazolobenzimidazole, phenol and naphthol type hydrophobically ballasted for incorporation in high-boiling organic (coupler) solvents. Other conventional photographic addenda such as coating aids, antistatic agents, acutance dyes, antihalation dyes and layers, antifoggants, latent image stabilizers, antikinking agents, and the like may also be present. Although not essential in the practice of the present invention, one particularly important class of additives which finds particular advantage in the practice of the present invention is high intensity reciprocity failure (HIRF) reducers. Amongst the many types of stabilizers for this purpose are chloropalladites and chloroplatinates (US-A-2,566,263), iridium and/or rhodium salts (US-A-2,566,263; US-A-3,901,713), cyanorhodates (Beck et al., J. Signalaufzeichnungsmaterialen, 1976, 4 , 131), and cyanoiridates. These and other aspects of the invention will be shown by the examples. Synthetic Methods The thio and oxy thiatriazoles were prepared by the synthetic routes outlined in methods A to E. Method A Preparation of 5-thio-1,2,3,4-thiatriazole, sodium salt. Into a 250 ml Erlenmeyer flask containing 75 ml of deionized water was added 20 grams (0.31 mole) of sodium azide and 25 grams (0.33 mole, slight excess) of carbon disulfide. The flask was stoppered and stirred overnight at room temperature. The yellow solution was filtered and then transferred to a crystallization dish for drying. The resultant solid was dissolved in acetone and filtered. Evaporation of the acetone yielded a yellow-white solid which was characterized by FT-IR and X-ray crystallography. Method B Preparation of 5 substituted thio-1,2,3,4-thiatriazole. Into a small flask or large test tube was weighed 2.97 grams (0.021 mole) of the sodium salt of 5-thio-1,2,3,4-thiatriazole (see Method A) and 30 ml of acetone to dissolve the solid. Hexanoyl chloride, 2.85 grams (0.021 mole) was added dropwise with vigorous agitation. A yellow-white solid precipitate formed almost immediately and was filtered. The solid was rinsed with several small portions of cold water and acetone, then allowed to air dry. Method C Preparation of 5-methylthio-1,2,3,4-thiatriazole. Potassium hydroxide (33 grams, 0.55 mole) was dissolved in 200 ml of ethanol and slowly added to 85% hydrazine monohydrate (0.55 mole) while stirring in an ice bath. To this solution was added 24 grams (0.52 mole) of carbon disulfide dropwise keeping the temperature between 5 and 10°C. The separation of potassium dithiocarbazinate from the aqueous solution was accomplished by extraction with 2 portions of diethyl ether. Evaporation of the ether gave a clear heavy yellow oil. One half was dissolved in 150 ml of water. After cooling in an ice bath, methyl iodide (39 grams, 0.27 mole) was slowly added in small portions. Agitation continued until the methyl iodide was consumed. The methyl dithiocarbazinate precipitated during this step and was collected and recrystallized from ethanol; m.p. 81-82°C. The methyl dithiocarbazinate underwent diazotization by sodium nitrite using methods known and published in the literature to yield 5-methylthio-1,2,3,4-thiatriazole; m.p. 34-35°C. Method D Preparation of 5-phenoxy-1,2,3,4-thiatriazole. Phenyl chlorothionoformate (3.44 grams, 0.02 mole) was dissolved in 5 ml of dry acetone. Sodium azide (1.4 grams, 0.22 mole) was dissolved in 12 ml of deionized water with 8 ml of acetone and slowly added to the phenyl chlorothionoformate solution over a 5 minute period. The reaction was kept at 5°C in an ice bath and stirred an additional 45 minutes before adding 12 ml of water. The solution was filtered to collect the product; m.p. 35-36°C. Method E Preparation of 5-benzylthio-1,2,3,4-thiatriazole. Preparation of the benzyl dithiocarbazinate followed the same procedure as in method C except that benzyl chloride was substituted for methyl iodide. Diazotization to make the target molecule was accomplished by using sodium nitrite by methods reported in the literature. The preparation of 5-methylthio-1,2,3,4-thiatriazole and 5-benzylthio-1,2,3,4-thiatriazole followed standard synthetic procedures reported in the literature for the preparation of thiatriazoles from dithiocarbazinates. These procedures were outlined in methods C and E respectively. We have found that the addition of methyl iodide or benzyl chloride to the sodium salt of 5-thio-1,2,3,4-thiatriazole yielded two compounds whose infrared spectra (FT-IR) correspond exactly with the FT-IR spectra of the two compounds as prepared in the preceding paragraph by diazotization. Also, their individual melting points were the same and mixed melting points showed no depression. Therefore, the compounds made by different routes were identical. An x-ray crystal structure was obtained on 5-benzoylthio-1,2,3,4-thiatriazole prepared by method B. This showed the substituted thio form as opposed to the thione (C=S) structure of the molecule. The preparation methods and melting points are compiled in the table below. Thiatriazole Synthetic Method m.p. (°C) T2 B 96 T3 B 94-96 T4 B 74-76 T5 B 84-86 T7 B 91-92 T9 B dec T11 B dec T12 B 51-54 T13 E&B 68-69 T14 C&B 33-35 T15 C 40-41 T16 D 35-36 T17 B dec EXAMPLES A silver halide emulsion was prepared by a double jet precipitation to provide a grain composed of 64% chloride and 36% bromide with an average size of 0.24 micrometers. The emulsion was digested with p-toluenesulfinic acid, sodium thiosulfate and sodium gold tetrachloride (NaAuCl₄). Final preparation of the emulsion comprised the addition of water and gelatin to the level of 5.0% gelatin and 2500 g of emulsion per mole of silver. The pH was adjusted to 7.0, and the pAg was adjusted to 7.2. Sensitizing dyes (D1-D6), phenyl-5-mercaptotetrazole (hereinafter PMT), p-chloroanilinothiatriazole (hereinafter ClATT) and the thio and oxy thiatriazoles were added as methanol solutions except T1 which was added as an aqueous solution. A 20 gram quantity of poly(ethylacrylate) (hereinafter PEA) was added as a 20% aqueous dispersion to all of the coated films. All additives listed in the tables are given in quantities per mole of silver. The coatings were run at 2.4 g Ag/m² on 7 mil (0.178 cm) clear polyester base. The coated and dried films were aged one day before exposing with a flash sensitometer for 10⁻³ seconds through either a 660 or 820 nm narrow band filter. The exposed films were developed in a 90 second X-ray procesor. Sensitometric results include Dmin, speed (SPD: at O.D = 1.0), average contrast (CONT) and the change in log E speed from emulsion without additives (dSPD). Sensitometric evaluation was also run on samples incubated under the extreme conditions of 7 days at 50°C and 60% R.H., and the speed loss in log E due to incubation (-dSPD) was calculated. Example 1-51 The effects of thio- and oxy-thiatriazoles were evaluated by adding them to the fine grain chlorobromide emulsion sensitized to the near infrared with 30 mg of heptamethine dye, D1. The results are reported in Table 1 for aromatic thio thiatriazoles (T2-T7) and in Table 2 for alkyl thio thiatriazoles (T8-T14) and oxy thiatriazoles (T15 and T16). The dimeric thio thiatriazole, T17, also was included in Table 2 whereas the water soluble sodium salt of thio-thiatriazole (T1) was placed in Table 1. All the sensitometry in Table 1 and 2 was performed with an 820 nm narrow band filter. The thio thiatriazoles of Table 1 show relatively little supersensitization but do show significant benefits when combined with PMT. In all cases, the incubated Dmin is greatly improved by combining any of T1-T7 with PMT. Improvements in incubated speed stability versus the control (Example B) were obtained by adding T1 (Example 4) or T7 (Example 28) to PMT. In these coatings, the fresh speed is lowered but a more stable system results with only a 0.06 log E speed reduction on incubation versus a greater incubated speed loss for the control (example B). Table 2 shows that the alkyl (T8-T14), dimeric thio thiatriazole (T17) and oxy thiatriazoles (T15 and T16) act as strong supersensitizers with reductions in incubated speed loss at levels exceeding the maximum for fresh speed. Example 52-57 The additive effects of thio thiatriazoles were tested both with an additional thio thiatriazole and with another strong supersensitizer, p-chloroanilino-1,2,3,4-thiatriazole (ClATT). The chemicals were added to the fine grain chlorobromide emulsion sensitized to the near infrared with 30 mg of heptamethine dye, D1. The sensitometric evaluation was performed with an 820 nm narrow band filter. The results are shown in Table 3. The initial speed was reduced by adding T1 to the two supersensitizers but improvements were found in the incubated data both in terms of lower Dmin and a lower speed drop (-dSPD). Example 58-66 Additional infrared dyes were examined to determine the breadth of the invention. The infrared dyes were added at their optimum level which was 20 mg for D2, 45 mg for D3 and 15 mg/mole Ag for D4. The IR dyes were added to the fine grain chlorobromide emulsion with different levels of 5-nonanoylthio 1,2,3,4-thiatriazole (T11). Sensitometric evaluation was performed with an 820 nm narrow band filter, and the results are listed in Table 4. All three infrared dyes show strong supersensitization in the presence of T11. Therefore, the thiatriazoles are not limited as supersensitizers to a specific class of IR dyes, but instead have broad utility as infrared supersensitizers. Example 67-69 The thiatriazole, T1, was examined in the protective topcoat layer coated over the emulsion layer. The silver halide emulsion layer was composed of the fine grain chlorobromide emulsion sensitized to the near infrared with 30 mg of heptamethine dye, D1, and supersensitized with 150 mg of ClATT. The emulsion was coated at 2.4 g Ag/m². The thiatriazole, T1, was incorporated into the topcoat layer which was composed of 5% gelatin and coated at 21.5 ml/m². The quantity of T1 is given in Table 5 both in mg of T1 per square meter and in mg of T1 per mole of silver. The sensitometric data in Table 5 was obtained with an 820 nm narrow band filter. The addition of T1 to the adjacent, topcoat layer does drop the fresh speed slightly but improves the fresh and incubated Dmin and reduces the loss of speed on incubation (-dSPD). Example 70-76 The thiatriazoles were examined further in other areas of the electromagnetic spectrum besides the infrared. The red sensitizing dyes, D5 and D6, were both added at 100 mg/mole Ag to the chlorobromide emulsion. The supersensitization effects of the dimeric thiatriazole, T17, were evaluated with a 660 nm narrow band filter and reported in Table 6. The thiatriazole, T17, does improve the speed of red sensitive films and also improved the Dmin on incubation. Therefore, the benefits of the thiatriazoles are not limited to the infrared.

Claims: A silver halide photographic emulsion in a hydrophilic colloidal binder, said emulsion being spectrally sensitized to the red or infrared portion of the electromagnetic spectrum and having a supersensitizing amount of either a 5-thio- or oxy-1,2,3,4,thiatriazole or a 5-substituted-thio- or oxy-1,2,3,4-thiatriazole wherein the optional 5-substituent of said 5-substituted-thio- or oxy-1,2,3,4-thiatriazole is bonded to said thiatriazole through a sulfur or oxygen atom. The emulsion of claim 1 wherein said 5-substituted-1,2,3,4-thiatriazole is represented by any one of the following general formulae wherein R¹ is selected from alkyl groups, aralkyl groups, aryl groups, allyl, and 5- or 6-membered heterocyclic groups having only C, N, S, or O ring atoms and wherein R² is selected from alkylene groups, aralkylene groups, arylene groups, allylene groups and 5- or 6-membered heterocyclic divalent linking groups having only C, N, S, or O ring atoms, and X is oxygen or sulfur. The emulsion of claim 1 wherein said 5-thio-or oxy-1,2,3,4-thiatriazole is represented by the general formula wherein R¹ is selected from a proton, and a cationic element and X is oxygen or sulfur. The emulsion of claim 2 wherein R¹ is a phenyl group, and wherein R² is a phenylene group. The emulsion of claim 2 wherein R¹ is an alkyl group, and wherein R² is an alkylene group. The emulsion of any preceding claim wherein poly(ethylacrylate) is also present in a supersensitizing amount. The emulsion of any claim 1 to 5 wherein two or more thio or oxy thiatriazoles are present. The emulsion of any claim 1 to 5 wherein an amino-thiatriazole is also present. The emulsion of any claim 1 to 5 wherein an arylmercaptotetrazole is also present. A photosensitive element comprising a substrate having adhered to at least one surface thereof a layer comprising the photographic emulsion of any preceding claim. The element of claim 10 wherein either said 5-thio- or oxy-1,2,3,4-thiatriazole or said 5-substituted thio-or oxy-1,2,3,4-thiatriazole is present in a protective layer adjacent to said emulsion layer and further from said substrate than said emulsion layer.

Inventors: PERMAN CRAIG A C O MINNESOTA M, PHILIP JAMES B JR C O MINNESOT, SILLS PETER D C O MINNESOTA MI, PERMAN, CRAIG A. C/O MINNESOTA MINING AND, PHILIP, JAMES B., JR. C/O MINNESOTA MINING AND, SILLS, PETER D. C/O MINNESOTA MINING AND
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1989
Main classification: G03C1
IPC codes: C07D285, G03C1