Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS3895951 A
Publication typeGrant
Publication dateJul 22, 1975
Filing dateSep 24, 1973
Priority dateSep 29, 1972
Also published asDE2247893A1
Publication numberUS 3895951 A, US 3895951A, US-A-3895951, US3895951 A, US3895951A
InventorsOhlschlager Hans, Riester Oskar
Original AssigneeAgfa Gevaert Ag
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Silver halide emulsion supersensitized with a merocyanine dye and a tertiary phosphine sulfide
US 3895951 A
Photographic silver halide emulsions are spectrally sensitized with neutral methine dyes (merocyanines, including openchain merocyanines and hemioxonoles) and the sensitization is increased and stabilized by the action of phosphine sulfides of the formula R1 S=P-R2 R3 wherein R1, R2 and R3 are alkyl, cycloalkyl, aralkyl aryl or heterocyclic groups attached to the phosphorus atom either directly or by connecting members as defined hereinafter.
Previous page
Next page
Description  (OCR text may contain errors)

United States Patent [191 Riester et a1.

[ 1 SILVER I-IALIDE EMULSION SUPERSENSITIZED WITH A MEROCYANINE DYE AND A TERTIARY PHOSPHINE SULFIDE [75] Inventors: Oskar Riester, Leverkusen; Hans Ohlschlager, Cologne, both of Germany [73] Assignee: Agfa-Gevaert Aktiengesellschaft,

Leverkusen-Bayerwerk, Germany 221 Filed: Sept. 24, 1973 211 Appl. No.: 400,238

[ July 22, 1975 3.582.340 6/l97l Kuwabara et a1 96/95 Primary Examiner-Won H. Louie. Jr. Alturney, Agent, or FirmConnolly and Hutz [57] ABSTRACT Photographic silver halide emulsions are spectrally sensitized with neutral methine dyes (merocyanines. including openchain merocyanines and hemioxonoles) and the sensitization is increased and stabilized by the action of phosphine sulfides of the formula wherein R R and R are alkyl, cycloalkyl, aralkyl aryl or heterocyclic groups attached to the phosphorus atom either directly or by connecting members as defined hereinafter.

3 Claims, N0 Drawings SILVER HALIDE EMULSION SUPERSENSITIZED WITH A MEROCYANINE DYE AND A TERTIARY PHOSPI-IINE SULFIDE This invention relates to a light-sensitive photo graphic material containing at least one silver halide emulsion layer which is spectrally sensitized with a merocyanine and the sensitivity of which layer can be substantially increased by the addition of phosphine sulfides.

It is known that the sensitizing action which sensitizing dyes exert on photographic silver halide emulsions can be considereably increased by certain additives which need not themselves be sensitizing dyes. This effect is known as supersensitization. The sensitization achieved in this way is, however, in may cases found to be extremely suspectible to the deleterious action of other necessary additives such as wetting agents, emul sifiers, stabilizers, color couplers or other non sensitizing dyes. This susceptibility to the action of other additives is a particularly serious problem in color photographic materials which contain color couplers or dyes which can be bleached, and it results in insufficient sensitization and in considerable loss of sensitivity in storage under extreme conditions such as high temperature and high atmospheric moisture. Another disadvantage of conventional supersensitization is that the sensitivity to light is in many cases increased only under conditions of low exposure, with the result that the gradation curve as a whole is flattened.

It is an object of the invention to achieve a permanent increase in the spectral sensitivity of photographic silver halide emulsions, especially of those which contain color couplers, and, at the same time, to obtain sufficient gradation without any increase in the tendency to fogging even under extreme storage conditions.

lt has now been found that the sensitization of silver halide emulsions which is achieved by means of merocyanines can be considerably increased by the addition of phosphine sulfides. Under phosphine sulfides in the context of this application, there are to be understood generally phosphorus compounds having a sulfur atom double bonded to a phosphorus atom that further carries three radicals other than hydrogen. The sensitization achieved by the combination of merocyanines and phosphine sulfides is found to be stable even in the presence of color couplers and under extreme conditions of storage.

This invention thus relates to a light-sensitive photographic material containing at least one silver halide emulsion layer which is spectrally sensitized with a merocyanine. The material is characterised in that the emulsion layer in addition to the merocyanine contains phosphine sulfide of the following formula in which R, and R; which may be the same or different, represent the following groups attached to the phosphorus atom either directly or via a connecting member X,,X as defined hereinafter l. a saturated or unsaturated aliphatic hydrocarbon group. e.g. an alkyl group containing up to car- LII bon atoms, preferably l to 6 carbon atoms, which may be further substituted, e.g. by an amino group, a hydroxyl group, an alkoxy, alkylthio or alkylseleno group a carboxyl group, a carbonamide group, a cyano group, a heterocyclic group such as furane or tetrahydrofurane or a halogen atom such as fluorine or chlorine; or 2. a cycloalkyl group, e.g. cyclohexyl or adamantyl; 3. an aralkyl group, e.g. benzyl or phenylethyl,

an aryl group such as phenyl or naphthyl, including substituted and condensed aryl groups such as tolyl, xylyl, dodecylphenyl, anisyl, chlorophenyl, dialkylaminophenyl, trifluoromethylphenyl, methylthiophenyl, methylene dioxyphenyl, acetylphenyl, carbalkoxyphenyl, methylsulfonylmethyl, sulfonylphenyl, biphenylyl, tetrahydonapththyl, benzylphenyl, benzothiazol-2-ylphenyl, pyrenyl, chrysenyl or phenylthiophenyl, or 5. a heterocyclic group, preferably one comprising a 5-, 6- or 7-membered heterocyclic ring which heterocyclic group may also contain condensed benzene rings and may carry further substituents, e.g. a pyrrolidine, piperidine, morpholine, piperazine, hexamethyleneimine, pyridine, thiazole, selenazole, oxazole, imidazole, indole, dihydroindole, pyrimidine, purine, pyrazole, pyrazolone, quinoline, thiadiazole, oxadiazole, triazole, tetrazole, diazine, thiazine, thiadiazine or l,l-dioxothiolan group; R, and R may further together with the phosphorus atom form a phosphorus-containing heterocyclic ring, for example a phospholine ring X, and X which may be the same or different, repre sent a connecting member that contains hetero atoms, such as for example O, S, Se, NR (R stands for hydrogen or one of the groups defined under R, and R NHN=, N- HNHSO NH-SO --NH-CO, NH-CS, NH-CSNH- or -N- HNl-l-CSNH,

R represents a group as defined under R, and R, that is attached to the phosphorus atom either directly or via a connecting member as defined under X, and X R further may represent a hydroxyl (-OH) or a thiol (SH) group, the latter being presented possibly in anionic form (S), for example as a -SNH., group. R however does not represent a radical bonded to the phosphorus atom via a connecting Oatom, when X, and X, both represent such connecting O- atoms.

Any group represented by R if substituted may carry either directly or via one of the connecting members defined above for X, and X and additional group wherein R, and R, have the same meaning as mentioned above. Any heterocyclic group represented by one of R,, R and R may be bonded to the phosphorus atom or to the connecting member either through one of its hetero atoms or through one of its carbon atoms. If there is no connecting member, then the heterocyclic group is prefereably bonded to the phosphorus atom through one of its hetero atoms (generally a nitrogen atom). For example, a pyrrolidyl group is bonded directly to the phosphorus atom preferably through its nitrogen atom thus constituting a P-N bond. On the other hand if there is any connecting member then the heterocyclic group is bonded to the connecting member preferably through one of its carbon atoms. Such a carbon atom may be part of the heterocyclic ring or of a benzene ring condensed thereto. For example, a benzothiazole group may be bonded to the connecting member through any of its carbon atoms.

The following are examples of compounds which are particularly suitable for intensifying the sensitization effect of silver halide emulsion layers achieved with merocyanines:

I C H,

a: CF

liiN H a o 85 S=P SeCH,

The compounds of the above general formula are, from a formal point of view, not all genuine phosphine sulfides but in some cases derivatives (O-esters, S- esters or amides) of the various sulfur analogues of phosphinic acid, phosphonic acid or phosphoric acid, depending on the number of carbon atoms which are indirectly attached to the central phosphorus atom, i.e. by way of a hetero atom.

These compounds are well known. For methods of their preparation, reference may be had, for example, to the following literature:

a. Houben-Weyl, Methoden der Organischen Chemie VoLXll/l Fourth Edition, 1963) pages 168 174, pages 278-287 pages 564-598; and Vol. XII/2, Fourth Edition, (1964) pages 623 795;

b. G. M. Kosolapoff, Organophosphorus Compounds, New York, John Wiley and Sons, Inc., 1950, page 98;

e. Z. Chem. 12, 137-138(1972).

d. Article of Chr. Fest and K. J. Schmidt in Chemie der Pflanzenschutzund Schadlingsbekampfungsmittel", Springer Verlag 1970, Vol. I, pages 248 253.

Merocyanines in the context of this application are understood to be neutral cyanine dyes in general as opposed to cationic or anionic cyanine dyes. Merocyanines in this application therefore include not only the merocyanines proper, in which a basic and an acid heterocyclic group are linked together, optionally through an even number of methine groups, but also those merocyanines in which the acid hcterocyclic group (cyclic ketomethylene compound) has been replaced by an open chain ketomethylene compound such as malodinitrile, sulfonylacetonitrile or a-cyanoacetic acid (the so-called open neutrocyanines) as well as those which contain a simple amino group instead of made to Houben-Weyl, Methoden der Organischen Chemie", Georg Thieme Verlag Stuttgart, Vol VII d, 1972. pages 284-295 and to Hamer. Cyanine Dyes and Related Compounds", lnterscience Publishers 1964, pages 485 488 and 511- 61 l.

The following are given as examples of merocyanines dyes whose sensitizing effect on silver halide emulsion layers can be enhanced by phosphine sulfides in accordance with the invention:


l a 's a": C H


Continued dyestuff VIII XII





I can The combinations according to the invention of merocyanines and phosphine sulfides may be used in any silver halide emulsions. Suitable silver halides for the emulsions are silver chloride, silver bromide or mixtures thereof, which may have a small silver iodide content of up to mols percent.

The silver halides may be dispersed in the usual hydrophilic binders, for example in carboxymethyl' cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts, esters or amides or, preferably, in geiatine. The silver halide emulsions may be the usual negative emulsions or such emulsions useful for forming positive images, for example such emulsions that form latent images predominantly inside the silver halide grains.

The phosphine sulfides used according to this invention may be added to the silver halide emulsion at any stage during preparation of the emulsion, for example at the silver halide precipitation stage or latter, e.g. before, during or after chemical ripening. They may be added together with the merocyanines or at an earlier or later stage. The method by which they are added is generally not critical and depends on the solubility properties of the phosphine sulfide used. The usual solvents may also be used for the addition of sensitizing dyes, for example alcohols such as methanol or ethanol, acetone, dimethylformamide, pyrrolidone hydroxypropionitrile, pyridine or phenols, for example cresol, but the compounds may also be added to the emulsion in the form of aqueous dispersions, e.g. dispersions in a dilute gelatine solution. They may also be applied to the emulsion by bathing or immersion or from an adjacent layer. The solvents must, of course, be compatible with gelatine and must not have any deleterious effect on the photographic properties of the emulsion. The quantity of phosphine sulfide added depends on the merocyanine used and on the intensity of the effect desired. Quantities of between 1.5 and 50 X 10 mol per mol of silver halide are generally suitable, the quantities preferably used being 5 to X 10"" mol per mol of silver halide. The quantity of phosphine sulfide used is of much the same order of magnitude as that of the merocyanine, being preferably 1 to times the molar quantity of merocyanine used. The most suitable concentration of phosphine sulfide and merocyanine for any given emulsion can easily be determined by conventional tests employed in the photographic art.

Since the sensitization obtained with the combination according to the invention is substantially unaffected by the presence of color couplers, it is particularly ad vantageous to use such a combination in color photographic materials which contain color couplers. This applies to all classes of color couplers, e.g. cyan couplers based on phenol or naphthol, magenta couplers based on pyrazolone or indazolone and yellow couplers based on open chain ketomethylene compounds. It is immaterial whether the couplers are hydrophobic couplers that preferably are incorporated in the binder from an organic water immiscible solvent or whether they contaian one or mor watersolubilizing groups, and accordingly may be brought in from aqueous solution. The combination of merocyanines and phosphine sulfides may advantageously also be used in color photographic materials that contain dye-giving compounds for imagewise producing diffusing dyes which can be transferred by diffusion into image receiving layers.

The emulsions may also be chemically sensitized, e.g.

by adding other sulfur compounds such as allylisothiocyanate, allylthiourea or sodium thiosulfate at the chemical ripening state. Certain reducing agents may also be used as chemical sensitizers, e.g. the tin compounds described in Belgian Patent Specifications No. 493,464 and 568,687, polyamines such as diethylene triamine or aminomethylsulfinic acid derivatives, e.g. according to British Patent Specification No. 789,823.

Noble metals such as gold, platinum, palladium, iridium, ruthenium and their compounds are also suitable chemical sensitizers. This method of chemical sensitization has been described in the article by R. Koslowsky, Z. Wiss. Phot. 46, 65 72 (1951).

The emulsions may also be sensitized with polyalkylene oxide derivatives, e.g. polyethylene oxide with a molecular weight of between 1000 and 20,000, or with condensation products of alkylene oxides and aliphatic alcohols, glycols, cyclic dehydration products and hexitols, alkyl substituted phenols, aliphatic carboxylic acids, aliphatic amines, aliphatic diamines and amides. The condensation products should have a molecular weight of at least 700 and preferably more than 1000. Combinations of these sensitizers may of course also be used in order to achieve special effects, as described in Belgian Patent Specification No. 537,278 and in British Patent Specification No. 727,982.

The emulsions may also in addition contain other spectral sensitizers, e.g. the usual monomethine or polymethine dyes such as bacic or acid cyanines, hemicyanines, streptocyanines, oxonoles, styryl dyes, and other that also may have three or more heterocyclic nuclei, such as rhodacyanines and neocyanines. Sensitizers of this type have been described in the work by F. M. Hamer The Cyanine Dyes and Related Compounds" lnterscience Publishers, I964.

The emulsions according to the invention may contain the usual stabilizers, e.g. homopolar or ionized compounds of mercury which contain aromatic or herocyclic rings, such as mercurymercaptotriazoles, simple mercury salts and sulphonium mercury double salts. Azaindenes are also suitable stabilizers, especially tetra-or penta-azaindenes and particularly those which are substituted with hydroxyl or amino groups. Such compounds have been described in the article by Birr, Z. Wiss. Phot. 47, 2 58 (1952). Quaternary benzothiazole derivatives, benzotriazole and the like are also suitable stabilizers, among others. Certain heterocyclic mercapto compounds containing substituents which confer a negative charge have been disclosed in German Auslegeschrift No. 1,447,577. These act both as stabilizers and as supersensitizing additives and produce particularly advantageous results when used with the combination according to the invention.

The emulsions may also contain white toners such as the known diaminostilbene derivatives as well as socalled masking or sharpening dyes from the series of anthraquinone, triphenylmethane or azo dyes. The emulsions may be hardened in the usual manner, for example with formaldehyde or halogenated aldehydes which contain a carboxyl group, such as mucobromic acid, diketones, methane sulphonic acid esters, dialdehydes, dimethylolurea, and dimethylolbenzimidazolone.

The invention will now be explained with the aid of the following Examples.

EXAMPLE 1 A silver halide emulsion which contains per kg l9 g 17 18 of silver, of which 35 mols percent are silver bromide EXAMPLE 2 and 65 mols percent silver chloride, is used. 3 mg of a 10 g of the sodium salt of l hydmxy 4 sulfo merocyamne of the followmg formula dissolved in ace- N octadecy| 2 naphthamide are added in the form of (1 99 added to l kg of emulslon as a 5% aqueous solution to asilver halide emulsion which spectra] sensmzer' 5 has been prepared as described in Example I and sensi- CH3 3 tized with mg of Dye l. The results shown in the followi g Table are obtained after exposure behind a u \f 2 step wedge and the aforesaid L 622 Red filter: CH

| 10 Table 2 CH,

5 Tropical Compound 2 mg c H a 2 s 30 27 2s 4 60 27 3O 25 9O 28 3i 2'! Preparation of this dye is carried out by a method anal- (1:500 in 120 28 31 28 ogous to that used for preparation of the corresponding acetone) s 1 Fresh Heat conditions c =cu c=cu cu= 5 without additive 23 24 23 l c H dye which is unsubstituted in the methine chain, described in Houben-Weyl, Methoden der organischen Chemie", Volume V/ld, page 290.

A sensitization maximum in deep red at 702 nm is obtained with this dye.

The emulsion is divided into two parts, each of which The samples were developed for 5 minutes at 20C in a developer of the following composition to produce a blue dye image:

is cast on a baryta paper substrate. 60 mg of triphenyl- Hydmxyhm-me Sulfate 3 g phosphine sulfide (Compound 1) dissolved in acetone N- kllllyl-lN- as ulfobulyl-pe (1:500) are added to one of these parts. g g fi f 'gfig 87 g The material is exposed behind a step wedge (w 2) Potassium bromide 1 g and an Agfa-Gevaert L 622 red filter (permeable to 2:22 hos hate is light above 622 nm) and developed for 2 minutes at made up with s; mpmoo m1 s 20C in a developer of the following composition:

The samples were then washed for 2% minutes and fixed in a short stop fixing bath for 5 minutes. They -Meth [amino henol l Elydroqiiinone p 3 g were then bleach fixed for 5 minutes and finally washed Anhydrous sodium for 0 minutes sulphide [3 g Anhydrous sodium carbonate 26 g EXAMPLE 3 Potassium bromide l g t Made up with ware, m 1000 The sensitivity values obtained when other phosphine sulfides are added to the emulsion described in Exam- The material is then fixed and washed in the usual Ple mg of Dye 1; m of the aforesaid cyan manner. The sensitivities obtained are shown in the folforming coupler) are Show" m Table lowing Table, expressed as number of visible steps T bl 3 {[7 Table 1 Tropical Fresh Heat conditions Without additive 23 23 23 Tropical w 60 mg of Compound I 27 29 25 Without additive I9 20 22 60 mg of Compound 3 26 28 25 60 mg of Compound 4 26 28 25 60 m of triphenyl- 60 mg of Compound 5 26 27 27 phosphine sul- 150 mg of Compound 6 28 30 27 fide 45 mg of Compound 7 26 27 27 (Compound 1) 24 27 25 45 mg of Compound 8 27 27 27 500 di l d 30 mg of Compound 9 26 28 22 in acetone) in the above Table, fresh means that the material EXAMPLE 4 is proceksfed a few 32 it has been cast heat. When the following color couplers (in each case 10 means t at exposure an evelopment are carried o ut g) are added to 0 mg of Dye I and 30 mg of triphenyL after the samples have been stored for 3 days at C phosphine sulphide (Compound 1) per kg of the Silver and 40% relative humidity and tropical condition? halide emulsion described in Example 1, the sensitivity means that sampl'jis'are Stored for 3 days at 30 C values shown in Table 4 below are obtained after color and relative humidity before exposure and develdevelopment carried out as described in Example opment. A, l-(4'-phenoxy-3-sulfophenyl)-3-heptadecyl- All the samples are practically free from fogging. 1 -5 as a 2.5% solution;

B. 3,5-dicarboxy-a-(4'- stearoylaminobenzoyl)acetanilide as a 3.3% solution;

C. l 3 '-Carboxyphenyl)-3-( p-stearylaminophenyl pyrazolone-S as a 2.5% solution;

D. l-hydroxy-[2'-(N-methyl-N-octadecylamino)-5'- sulfo1-2-naphthanilide as a 6% solution;

The sensitivities to red obtained with increasing quantities of triphenylphosphine sulfide (Compound I added to a silver chlorobromide emulsion described in Example I which contains mg of Dye ill and 10g of the cyan-forming coupler mentioned in Example 2 per kg of emulsion are shown in the Table below. Sensitization maxima are observed at 615 and 663 nm.

in the sensitizing dye mentioned in Example 2 is replaced by 10 mg of the other sensitizing dyes, the values shown in Table 6 are obtained.

Sensitization Tropical maximum (nm) Fresh Heat conditions He IV 692 Without additive 23 24 24 45 mg of Compound 1 26 27 25 Eye V 712 without additive 26 25 25 60 mg of Compound 1 29 29 28 Efi. Without additive 24 25 24 45 mg of Compound l 27 28 27 Eye VI! 655 Without additive l8 l8 14 45 mg of Compound 1 24 25 17 Dye Vll 740 Without additive 22 24 21 45 mg of Compound l 26 25 26 e IX 690 Without additive 25 24 23 60 mg of Compound 1 28 28 27 Eye X 672 Without additive 24 26 27 60 mg of Compound I 28 30 29 Dye Xl 700 Without additive 23 24 24 60 mg of Compound l 27 28 25 EXAMPLE 7 10 mg of the following neutrocyanines dissolved in acetone to a dilution of 1 2000 are added to 1 kg of a silver chloride emulsion prepared according to T. TH. Baker, Photographic Emulsion Technique (American Photographic Publishing Co. Boston/Mass), I948, page 217. Table 7 below shows the sensitivity values obtained with and without the addition of mg of triphenylphosphine sulfide (Compound l after exposure behind a step wedge n) and a pale yellow filter which absorbs below 435 nm (GG 435" of Agfa- Gevaert AG) and therefore excludes the intrinsic sensitivity of the emulsion.

Table 7 Without Sensitiza- Dye phosphine With comtion maximum sulfide pound 1 (nm) XIV 4 17 465 XV 22 26 575 XVI 21 24 570 XVll 5 13 498 EXAMPLE 8 -naphthamide.

To 1 kg of a silver chlorobromide emulsion as described in Example 1 are added l0 mg of Dye l and 10 of the sodium salt of l-hydroxy-4-sulfo-N-octadecyl-2- naphthamide. To different sample of this emulsion are further added a phosphine sulfide as indicated in the following table 8 in an amount of 60 mg per kg of emulsion. The samples are then cast on a photographic paper base. The dried layer is then exposed to light behind a red filter that is transparent above 622 nm and a a 2 step wedge, and is subsequently color developed. bleach fixed and rinsed. Table 8 shows the sensitivity of the different materials indicated by number of visible steps.

Table 8 visible steps V 2 after exposure behind red filter no additional compound What is claimed is:

1 A light sensitive photographic material comprising at least one silver halide emulsion layer containing a merocyanine spectral sensitizing agent and a sensitizing and stabilizing tertiary phosphine sulfide having the general formula:

2 1 wherein R and R may be the same or different and represent a saturated aliphatic hydrocarbon group; a cycloalkyl group; an aralkyl group an aryl group; a heterocyclic group comprising a 6- or 7-membered heterocyclic ring;

and R, and R together with the phosphorus atom may form a phospholine ring;

R represents a saturated or unsaturated aliphatic hydrocarbon group; a cycloalkyl group; an aralkyl group; an aryl group; a heterocyclic group comprising a 5-, 6- or 7-membered heterocyclic ring; a hydroxyl group or a thiol group;

X and X, and X represent a chemical bond or linking member containing hetero-atoms and being selected from the group consisting of -O, S, Se, -NR (wherein R stands for hydrogen,

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2271622 *Feb 29, 1940Feb 3, 1942Eastman Kodak CoPhotographic emulsion
US3582340 *Jul 2, 1968Jun 1, 1971Konishiroku Photo IndProcess for the antistatic treatment of light-sensitive silver halide photographic materials with phosphine oxide
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4003746 *Jul 1, 1975Jan 18, 1977E. I. Du Pont De Nemours And CompanyOrganic heterocyclic and thioaryl phosphines in silver halide emulsions and developers therefor
US4115129 *Oct 28, 1977Sep 19, 1978E. I. Du Pont De Nemours And CompanyOrganophosphine sulfides as photographic sensitizers
US5378595 *Mar 1, 1994Jan 3, 1995Fuji Photo Film Co., Ltd.Silver halide photo-sensitive material
US5601970 *Jan 3, 1995Feb 11, 1997Eastman Kodak CompanyContaining thiophosphate ester
US7026105 *Dec 9, 2003Apr 11, 2006Eastman Kodak CompanyPhotothermographic materials containing silver halide sensitized with combination of compounds
US7063941 *Dec 9, 2003Jun 20, 2006Eastman Kodak CompanyMethod for chemical sensitization of silver halide for photothermographic use
US7087366 *Dec 9, 2003Aug 8, 2006Eastman Kodak CompanyMethod for chemical sensitization of silver halide for photothermographic use
US7157219Sep 30, 2005Jan 2, 2007Eastman Kodak CompanyPhotothermographic materials containing silver halide sensitized with combination of compounds
U.S. Classification430/550, 430/551, 430/572, 430/610
International ClassificationG03C1/08, G03C1/28
Cooperative ClassificationG03C1/28
European ClassificationG03C1/28