Patent GB-1028814-A (GB)
Title: Process of sensitizing photographic silver halide emulsions, the emulsions so sensitized and photographic elements including them
IPC: G03C1/09
Filed: 1962-11-05
Abstract: 1,028,814. Photographic silver halide emulsions. EASTMAN KODAK CO. Nov. 5, 1962 [Nov. 6, 1961], No. 41723/62. Heading G2C. A photographic silver halide emulsion is sensitized by incorporating therein elemental sulphur or a precursor thereof (i.e. a compound having a -S-S- bond and which gives rise to elemental sulphur in an aqueous medium) and an organic thiol or a precursor thereof (i.e. a compound which gives rise to a thiol in an aqueous medium). The sulphur precursor may be dithiodimorpholine. The organic thiol precursor may be one of the following: - (i) A compound of the formula R-CH(X)-NHR or R-CH(x)-H 2 COR when R is aryl or substituted aryl and X is a thio-ether radical, (see Specification 1, 010, 563). R may be phenyl which may be substituted with a nitro, alkoxy, acyl or amino group and X may be phenylthio or phenylalkylthio wherein the phenyl group may be substituted with a carboxy, amino or alkyl group or it may be -S-R<SP>4</SP>)-M where R<SP>4</SP> is alkylene of 1 to 20 carbon atoms and M is amino, amido, sulphonyl, hydroxyl, alkoxy, carboxylic acid or ester or a heterocyclic radical such as morpholinyl or a phenyltetrazine radical. (ii). Compounds of the formula VIII or IX wherein R<SP>12</SP>-R<SP>18</SP> are hydrogens or hydrocarbon radicals or R<SP>12</SP> and R<SP>13</SP> are acyl radicals or together form an alkylene radical which with the nitrogen atoms forms a heterocyclic nucleus, n is 1 to 10 and E is amino, carboxyl, sulphonyl or hydroxyl, or salts of such compounds (see Specification 1, 019, 222). Examples are given of the use of carboxymethyl isothiourea, #-aminoethyl isothiourea and y-sulphopropyl isothiourea. (iii) Thiazoles and thiazolines and their quaternary salts, particularly those having a 2-amino or 2- hydrocarbon substituent (see Specification 1, 019, 223). Examples are given of the use of N- methylbenzthiazolium methosulphate and 2, 3- dimethyl-thiazolium perchlorate. (iv) Compounds of the formula B-S-A-S-B where A is alkylene and B is ureido or a N-containing heterocyclic group, and their salts (see Specification 616, 822), such as 1, 2-ethane bis(isothiouronium bromide). (v) Thiouronium compounds of the formula wherein R<SP>5</SP> is alkyl or substituted alkyl and z is halogen (see Specification 613, 400). (vi) Formamidinothiomethyl compounds of the formula R<SP>6</SP>-N=C(R<SP>7</SP>)-S-CH 2 -R<SP>8</SP> where R<SP>6</SP> is hydrogen, alkyl or aryl, R<SP>7</SP> is amino or substituted amino (including 2-thiazylamino and 1, 2, 4-triazylamino) and R<SP>8</SP> is alkyl, carbalkoxy, heterocyclyl (tetrazaindenyl or pyridyl) or amido (see Specification 886, 722). (vii) Organic disulphides such as 5- thioctic acid, di-o -formylethylamino-diphenyl-disulphide, bis(o-carboxyphenyl) disulphide, bis(o- N-methyl carbonamido-phenyl) disulphide,γ,γ<SP>1-</SP> dithio-dibutyric acid, (HO-CH 2 CH 2 -S-) 2 , (HO . CO-(CH 2 ) 3 -S-) 2 , and (NAO 3 S-(CH 2 ) 3 -S-) 2 . Reference also is made to S-p-tolyl-isothiourea. The organic thiol compound may be an alkylthiol in which the alkyl group may be substituted by a sulpho, carboxyl, hydroxyl, phenyl or amino group, or an arylthiol in which the aryl group is substituted by an alkyl or carboxyl group. Thiol compounds specified are, thiosalicylic acid, N -methyl -thiosalicylamide, sodium thioglycollate, p-tolyl-thiol, benzylmercaptan, HS-CH 2 CH 2 NH 2  . HCl, HSCH 2 CH 2 OH, HS-(CH 2 ) 3.  COOH and HS-(CH 2 ) 3 -S0 3 H guanidine salt.