GB2205966A

GB2205966A - Reductive sensitization of silver halide photographic emulsions

Info

Publication number: GB2205966A
Application number: GB08814328A
Authority: GB
Inventors: Miklos Szucs; Judit Csaplaros; Olga Frigyik; Agota Palotas
Original assignee: FORTE FOTOKEMIAI IPAR
Current assignee: FORTE FOTOKEMIAI IPAR
Priority date: 1987-06-16
Filing date: 1988-06-16
Publication date: 1988-12-21
Anticipated expiration: 2008-06-16
Also published as: GB8814328D0; GB2205966B; JPS6415731A; HU203120B; DE3820592A1; HUT47752A

Description

2 '2 0 5 1: j 6, f 5 REDUCTIVE SENSITIZATION OF SILVER HALIDE PHOTOGRAPHIC

EMULSIONS This invention relates to the reductive sensitization of a silver halide photographic emulsion by the inclusion complexes formed from hydrazine derivatives with substituted cyclodextrins or water-soluble 5 cyclodextrin polymers.

The aim of the chemical sensitization of silver halide crystals is to achieve the ability of a given portion thereof to be developed easier. A method of sensitization is the reduction process wherein sensitive io centres of a small size, consisting of a few hundred silver atoms are formed on the surface of the crystals.

The most frequently used reducing agents are stannous compounds, ascorbic acid, formamidinesulfinic acid or silanes (H. Frieser, E. Klein: Grundlagen der photographischen Prozessen mit Silberhalogeniden; Akademische Verlaggesellschaft, Frankfurt, Vol. II., p. 677, 1966). Aminoboranes (United States patent specification No. 3,761,276) or gaseous hydrogen (United States patent specifications Nos. 3,891,441 and 3,984,249) may also be used.

Although the reductive sensitization with hydrazine is a long-known process (it had been described 11, 1 n United States patent specification No. 2,410,690) it has not been used on an industrial 3cale, probably because it induces a fogging of the emulsion even when used in small amounts (see. e.g.: S. S. Collier 51nternational Congress for Photography, ICPS, Rochester, p. 130, 1978).

Thus, hydrazine and its derivatives (e.g. hydrazine dihydrochloride, phenylhydrazine hydrochloride, 4-methylsulfonamidoethyl-phenylhydrazine and the like) 10are used for fogging in direct;..positive emulsions as described in United States patent specification No.

337613276.

This fogging ability is connected with the relatively strong reducing properties of hydrazine and 15some ot its derivatives. However, tha-eby a possibility is obtained to use these substances, e.g. phenylhydrazine, n apthylhydrazine, hydrazobenzene, aliphatic hydrazine derivatives, carboxyphenylhydrazine, diphenylhydrazine and the like as photographic developers together with the 20appropriate ingredients (T. E. James: The Theory of the Photographic Process, New York, p. 310. 1977).

The aim of the present invention is the reduction sensitization of photographic silver halide emulsions by the use of hydrazine derivatives. The use ot such compounds 25may be interesting because oxidation in the photoemulsion is irreversible. Thus, their effect is similar to the sensitization by gaseous hydrogen which is otherwise favourable but problematic in the realization on an indust- 11 1 1 rial scale.

According to Hungarian patent application No. 2455/84, the inclusion complexes formed from the water-soluble monomers and polymers containing various substituents with labile thiazolidine, oxazolidine, imidazolidine or selenazolidine derivatives containing sulfur, selenium or tellurium atom can be used for the chemical sensitization of silver halides.

The present invention is based on the recog- nition that hydrazine derivatives containing an aromatic or aliphatic cyclic substituent are also capable of forming water-soluble inclusion complexes with cyclodextrin derivatives.

Furthermore, the invention is also based on the recognition that hydrazine derivatives built into an inclusion complex are capable of the reductive sensitization without any considerable increase in the fogging value.

Cyclodextrins (CD-s) are cyclic, non-reducing oligosaccharides built up from ccD-glucopyranose units which are known mainly by their inclusion complex-forming pro-perties (j. szejtli: Cyclodextrins and their Inclusion Complexes; Akac16miai Kiac16, Budapest, 1982). The most widely used compounds are the oh fl- or - p-cyclodextrins consisting of 6, 7 or 8 glucopyranose units, respectively which are prepared by the enzymatic decomposition of starch.

The cc-cyclodextrins contain 18, whereas 2_ and -derivatives contain 21 or 24, respectively free alcoholic hydroxyl groups. The reactivity of these grcups provides the preparation of variously substituted derivatives of the monomer as well as water-soluble and water-insoluble polymers.

The sulfo and carboxyl derivatives obtained by substituting the monomer (e.g. through a reaction with chloroacetic acid or butanesulfone) are remarkable for their good solubility in water.

The water-soluble cyclodextrin polymers with a medium molecular weight can be prepared by several methods. According to one of these methods. cyclodextrin (CD) is first transformed to an unsaturated polymerizable derivative which is then polymerized as such or with a monomer containing no CD [3. Polym. Sci. Letters, 13, p. 357 (1975)1. According to anothermethod, CD molecules are transformed with a bifunctional reagent such as diepoxides or epichlorohydrin to non-crosslinked, water- -soluble polymer derivatives containing straight or branch- ed chains (Hungarian patent specification No. 180,597) or water-soluble polymer products substituted by ionic groups (Hungarian patent specification No. 191,101). To introduce the ionizable functional grcups, reagents are used which are capable of reacting with the alcoholic hydroxyl grouos in the alkaline medium used in the preparation of the polymer. Such reagents are e.g. haloalkylamines or i 0 r haloalkanoic acids for introducing an amino or a carboxylic group, respectively. Such reagents may also be employed which can react with an epoxy group of the coupling agent or with an epoxy group formed at the end 5 of the chain during the preparation of the polymer.

Thus, the Invention relates to a process forthe reductive sensitization of silver halide photographic emulsions by precipitating the silver halide crystals in a protective.colloid solution, growing them to the size required and optionally by removing the ions being present in an excess. which comprises, f.or. reductive. sensitization, introducing into the photographic emulsion and inclusion complex consisting of a cyclodext'rin of the gener'al formula (1), 1 1 is CD- (0.-- R)k (I) wherein CD R is a cyclodextrin molecule, is hydrogen or a R 2 CO 2 H# R 2 so 3 H, R 2 NH V (R' 2) 2 NH group wherein R 2 means a C 1-5 straight or branched chain alkylene group; and k is 1, 2, 3, 4 or 5, or a cyclodextrin polymer of the general formula (II), is CD- (07 (CH 2) wherein 1 OR 2 (CR')t CR2 1 1 1 LH-h< - 0).-CD10- CH2 - CH - R')n - XIC 11 CD means a group derived from the P-Cyclo dextrin molecule by removing a p + s hydroxyl groups; R and R independently from another stand for a -CH 2 -, -CHOH-CH 2-1 -CFL.CHOH-CH 2-1 -CH 2-0 -(CH 2) 2-0-CH 2-CHOH-CH 2- -CH 2-0-CH 2-CHOH -CH 2_ or -CH 2-0-(CH 2) 4-0-CH 2-CHOH-CH 2_ group; X is an -OR 1, -OR 2 or NR 4 R 5 group; R means hydrogen or, when r is different from zero, a group derived by removing a hydroxyl group from a B-cyclodextrin molecule; R 2 stands for hydrogen, -PO(OH) 2 or -SO 3 H$ -RINH-(CH 2) M-CO 2 H# -R 3_(CO 2 H)u$ -R 3_SO 3 H or -R 3_NR 4 R 5 group or a group derived by removing a hydroxyl group from a 2-cyclodext rin molecule; R 2# is the same as defined for R2 above, except the group derived from the cyclodextrin molecule; stands for a Cl_10 group derived from an alkane, the terminal carbon atom of which standing near to the polymer chain may r if 1 R 4 and R 5 m and n r p s and t U with the provisoe; that m, n, r, t and u may be various within a unit; and p + s is equal to or.lower than 18 with an average molecular weight of 2000 to.15000 is containing 30 to 70 % of cyclodextrin, and a hydrazine derivative of the general formula (III), optionally be independently hydrogen or a are integers is an integer is an integer independently from 0 to 7; is an inteaer substituted by an oxo group; from another stand for c 1-4 alkyl group; from 0 to 25; from i to 17; from 1 to 18; from another are integers and from 1 to 5, R 1- NH. NH- R 2 wherein R 1 (III) means a quinolyl, pyridyl or cyclohexyl group or a group ot the general formula (a) to (h); R 4 R R 3 (a) N R 6 ' 1 S R6 (c) (e) H R 6 N 1 67 "li R 1:3L N (9) R 4 (b) N - - R 6,l 'C5 J_ R6 (d) R5 o', - l - IT" N R (f) R 4 (h) R 2 means hydrogen or a phenyl group; R 3 stands for hydrogen, halogen, a C 1-4 alkyl or alkoxy group or sulfonamido group$5 R 4 and R 5 are hydrogen or halogen; and R 6 means C 1-4 alkyl or alkoxy group, in amount of 100 to 500 /umol/mol, preferably 25 to 100 / umol/mol of silver halide as calculated for the reducing agent, the molecular ratio of the CD monomer in the inclusion complex to the sensitizing agent, i.e. (2 = ECD1/ [S] being between 4:1 and 80:1, preferably between 10:1 and 50:1.

For calculating the Q va 0.01 X C X m ECD1 = 1135 where 15 C m lue is the amount in grams of the CD derivat.ive in 1 litre of solution; is the CD monomer content in % of the CD derivative; and 1135 is the molecular weight of the CD monomer.

In the process according to the invention, the reductive sensitization may be combined with sensitization by sulfur and gold. In these cases, the inclusion complex containing the reducing agent may be added before, between or after the sulfur and gold compound. Alternatively, the process of the invention may be carried out in such a way that the reductive -10sensitization is combined with sulfur and with an element of group VIII of the periodic table (preferably with Ir, Pt, Pd or Ru) while the inclusion complex may be added before or after introducing the compound containing sulfur 5 and an element of the group VIII or between those.

According to another embodiment of the process ot the invention, the reductive sensitization is employed after growing the silver halide crystals up to a given size, then the crystals are further grown up to a lo defined size whereby a core/shell structure is formed. The sensitization by sulfur and gold is optionally accomplished on the surface ot te shell. According to a further embodi ment of the process of the invention, the inclusion complex containing the reducing agent is introduced to the emulsion after growing the crystals up to a defined size, whereupon the surface of the crystals obtained is recrystallized by adding a halide required for forming a silver salt which is less soluble than the silver halide formed during precipitation. 20 According to the invention, the inclusion complex containing the reducing agent may be introduced to the protective colloid solution before the precipitation of the silver halide crystals whereby the reduction may proceed during the whole period of the formation and growth of the crystals. In the process according to the invention, the emulsion is provided with the usual additives after - 11ending the ripening. Such additives are the colour-sensitizing dyes, stabilizers, wetting and hardening agents and the like.

The colour sensitizing agent may be e.g.

1-ethyl-3--phenyl-2-quino-SI-rhodanine (dyestuff I), 3,3'-diethyll'-phenyl-benzoxazolidine.(ethylidene-21- _thiohydanthoine (dyestuff II), 3,3'-diethyl-6,6'-di- naphthyl-g-phenylthio-carbocyanine (dyestuff III), benzothiazole-phenyl-2thiohydantoine-tetramethynemerocyanine (dyestuff IV) (P. Glafkides: Photographic Chemistry, vol.

II. Fountain Press, London, 1960, pp. 832-836).

- As stabilizers e.g. 4-hydroxy-6-methyl- 1,3,3a,7-tetraazaindole (TAI), 1-phenyl-5-mercapto-tetra- zole. mercatobenzothiazole, mercaptobenzoxazole and the like may be used (G. P. Duffin: Photographic Emulsion Chemistry, Focal Press, London,-1966, pp. 138-141).

The hardening agents may be e.g. formalin, glutaraldehyde, glyoxal, 2,4-dichloro-6-hydroxy-s-triazine etc. (T. H. James: The Theory of the Photographic Process 20IV. Edition, MacMillan, New York, 1977, p. 82).

The wetting agents may be e.g. alkenylsucci- nic acid polyglycerides, dodecylphenol-polyglycolether, saponine and the like (V. M. Derjagin, S. M. Levi:

Film Coating Theory, Focal Press, London, 1966, p. 162).

The inclusion complex is prepared by dis- sdving the required amount of the reductive sensitizing agent in an aqueous solution of the CD derivative.

-12For the complex formation, a solution of 1 to 10 % of the substituted monomer and a solution of 2 to 20 % of the water-soluble polymer are prepared. The sensitizing agent is dissolved in an amount of 10- 4 to 102 mol/litre in the CD solution.

In the process according to the invention, the compounds shown in Tables 1 to 3 may optionally be used.

Table 1

Compounds derived from the substances of general formula (I) Sign R k M1 -CH 2 COOH 3 M2 -CH 2 COOH 5 M3 -(CH 2) 4 SO 3 H 1 M4.. (CH 2) 3 SO 3 H 3 M5 -N(C 2 H 5) 2 2 1 Average CD Sign rno 1 e cu - lar weight FW 5339 P2 5810 P3 6019 1 Table 2

Compounds derived from the'eubstances of general formula (II) Carb- Nitrosul- R 23 11 gen fur content % - CH2 COOH.

6318 3j37 577 5577 5709 59)6 3910 58p3 - l93 157. 1j47 2)30O70 - 3p19 Note: B = -CH 2-CHOHCH 2-NYI(CH 2) 2-CO 2 H S t - R R 2 R# CH 2 COOH B m n x r p 2 21 CD 1 8 12 CD 1 6 12 CID 1 1 1 CH 2 CH 2 COOH and H 0 0 CH2 CH2 N(C2 5)2 ardH, 0 0 CH 2 (CH 2)4 so 3 H and H 2 0 CH 2 CH 2 N(C 4 H9) 2 Td H 6 18 CD 1 1 1 CH 2 H 180 OH 0 9 1 1 1 PC4 1 -14Table 3

Compounds derived f rom the substances of general formula ( I I I) Sign S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 Sil S12 S13 S14 Formula @_ NH-NH 2 e--NH - NHCH 3 0-NH c 2 H 5-@- NH - NH 2 cl cl NH - NH 3 H 2 NO 2 S'g-NH - NH 2 - NH 2 t,e,nl NH - NH 2 R.' h& NFL NH 2 NH - NH 2 Cl NH - NH 2 NH - NH2 NH - NH 2 NH - NH 2 CH -' CH 2 - CH 2-s, 2 "CH 2 - CH 2 CH - NH - NH 2 The advantages of the process of the invention may be summarized as follows:

1) The hydrazine derivatives according to the invention. except)henylhydrazine are insoluble or very badly soluble in water; their hydrochlorides are moderately water-soluble; a part thereof is soluble in hot Ethanol however, they precipitate from the solution at room temperature.

Conversely the s_ame compounds are well soluble even in a concentration of 10-2 mol/litre in the aqueous solution of CD derivatives whereby a convenient introduction thereof to the photoemisions is made possible.

2) The hydrazine derivatives are decomposed in aqueous solutions; however, their stability is enhanced in the form of inclusion complexes. The reduction poten tial of e.g. an aqueous solution of 10-3 mol/litre of phenylhydrazine is decreased by 30% during a storage at 6 0 C for 8 days; however. it remains unchanged in a P1 solution of 10% under the same conditions.

3) The reducing agent added in the form of an inclusion complex exerts a substantially higher sensitiz ing effect and nevertheless induces less fogging than the same introduced as an aqueous or alcoholic solution to the emulsion.

The process according to the invention is illustrated in detail by the following non-limiting t,-- Examples.

Example 1 g of inert gelatine are swollen and dissolved in 100 mi of water. then 0. 035 mol of potassium bromide, 0.01 mol of cadmium chloride and 0.06 / umol of rhodium complex are added. The silver halide is precipitated by adding 60 mI of an 1,.4 molar silver nitrate solution at 60 OC. After a heat-treatment for 20 minutes, 40 9 of inert gelatine are added and the heat-treatment is continued for additional 80 minutes. After cooling the emulsion obtained to 40 OC, the pouring additives (50 ml of an O.OTIO dyestuff II solution, 80 ml of 50 % glycerol solution, 40 ml or 4 % saponin solution, 20 ml of 5 % formol, and 35 ml of 1 % 1-phenyl-5-mercapto- tetrazole solution as calculated for 1 mol or silver halide) are added. Threafter, the emulsion is applied onto a paper carrier by using a silver content of 2 1.05+0.05 9/M. The photographic characteristics of the thus obtained control-material are determined according to the standard recommendation No. ISO 6846/1984. The development is carried out at 18 OC for 2 minutes in a solution containing 1 9 of N-methyl-p-aminophenol sulfate, 20 9 of anhydrous sodium sulfite, 4 g of hydr.oquinone,.10 9 of anhydrous sodium carbonate and lg of potassium bromide in 1 litre of water.

The solution or the inclusion complexes is introduced as a thin stream into the emulsion by 15 minutes after adding the second portion of gelatine.

W At the same time, the aqueous or alcoholic solution of the hydrazine derivative or optionally, the chemical sensitizing agents are added in the defined order.

The substances investigated are the s inclusion complexes of the CD monomers which are both here and hereinafter marked (signed)'by the signs of the components (ingredients). The results obtained are illustrated in Table 4.

Table 4

Sign of _[CD1 Portioning Photographical characteristics the com- LS1 of the re- Average Relative gogging 0 plex ducing gradient sensitivi- 18 c 30 c agent ty 2 min 10 min / umol/mol Control - 1.58 100 0.02 0.12 S1 (aqueous) - 48 1.13 108 0.05 01.15 MI/S1 40 48 1.51 158 0.02 0.10 M2/SI 40 48 1.43 145 0.02 0.10 M3/S1 40 48 1.61 175 0.03 0.09 M4/SI 40 48 1.39 140 0.02 0.08 M5/S1 40 48 1.62 185 0.03 0.10 1 1 1 CO 1 1 1, It is obvious from the results that an increase by 48 to 85 % in the sensitivity was obtained without any increase in the fogging by using phenylhydrazine built into inclusion complexes formed with CD monomers. A lower gradation and sensitivity as well as a higher fogging were induced by a sensitizing agent without complex formation.

Example 2

The process desc-ribed in Example 1 is followed, except that the inclusion complexes formed from the P1 polymer with various hydrazine derivatives are portion- - wise added into the emulsions in various amounts and molar ratios. The results are summarized in Table 5.

It is shown by the results that in each case, a higher sensitivity was obtained by using the hydrazine derivatives as inclusion complexes than by using their aqueous or alcoholic solutions.

Portioning Table 5 Photographical chara=riiing Sign of [CD] of the reAverage Relative 9 0 the com- -FST ducing agent gradient sensitivity is c 30 c Plex / UM01/M01 2 min 10 min Control - 158 100 0.02 0.12 S1 X 48 117 145 0.05 0.18 S1 3R X 46 l13 95 0.05 0---16 S2 xXX - 48 1926 100 0.05 0.10 S3 X - 480 1330 106 0.06 0.18 S4 - 460 1)10 95 0.04 0.09 S5 - 480 1226 115 0.04 0.10 S6 - 48 1,11 91 0.03 0.09 S7 - 48 l26 i30 0.06 0.16 S9 - 48 1919 i40 0.04 0.15 Sil - 48 1j29 125 0.04 0.14 P1/S1 50 48 133 219 0.05 0.14 PI/S2 50 48 120 105 0.05 0.12 P1/S3 50 480 16l 165 0.04 0.10 P1/S4 50 480 l.,56 110. 0.03 0.110 P1/S5 50 480 1275 152 0.03 0.12 P1/S6 50 24 l.,28 200 0.06 0.22 P1/S7 50 72 130 190 0.06 0.15 P1/S9 50 48 140 180 0.03 0i12 P1/S11 50 48 1343 140 0.03 0.10 1 1 Sign of the com plex ICD] Portioning TS7 of the reducing agent / UM01/M01 Table 5. (cont.) Photographical characteristics Averag Relative Fogging gradient sensitivity 18 oC 30 2 min 10 0 c min pl/S1 5 48 1.40 200 0.05 0.09 96 1.39 185 0.05 0.10 144 1.36 167 0.06 0.12 192 1-,28 150 0.06 0.14 P1/S1 75 48 1.25 140 0.04 0.10 48 1,33 219 0.05 0.14 48 142 202 004 0.12 48 l35 198 0.04 0.12 48 1.26 -196 0.04 0.081 48 1.40 200 0.05 0.09 Note: X ethanolic solution XX aqueous solution XXX aqueous solution of S4S11 Example 3

The process described in Example 1 is followed, except that various inclusion complexes of phenylhydrazine or 2-quinolylhydrazine, respectively are added to the emulsion. The results are summarized in Table 6.

1 Table 6

Sign of [CD] Portioning Photographical characteristics tsxcom- ---MSof the re- Average Relative Fogging p ducing agent gradient sensitivity 18 0 c 30 0 c /UM01/M01 2 min 10 min P1/S7 50 48 1.22 176 0.04 0.14 P2/S7 so 48 1 "3 2 121 0.06 0.14 P3/S7 50 48 1.31 102 0.05 0.15 P4/S7 50 48 1.06 95 0.05 0.14 P5/S7 50 48 1.02 86 0.05 0.14 S7 (aqueous) - 49 1.26 130 0.06 0.16 PI/S1 50 46 1.33 '219 0.05 0.14 P2/S1 50 48 1.35 115' 0.05 0.12 P3/S1 50 48 126 126 005 012 P4/S1 50 48 122 110 0.06 0 -16 PS/S1 50 48 1.05.175 0.05 0.20 S1 ( aqueous) - 48 1.16 104 0.05 0 1.6 Control - 1.158 100 0.02 0.12 It is obvious from the above results that the inclusion complexes exert an effect of various extent on the sensitivity: this depends upon the structure of the CD polymer and the hydrazine derivative. In the optimum composition of the complex, both reducing agents are more effective than their solutions prepared only with water.

Example 4

The process described in Example 1 is followed, except that 0.01 mol of cadmium chloride is only added to the inert gelatine solution and the silver halide is precipitated by using 60 mlof a 1.4 molar silver nitrate solution and 60 ml of a 1.4 molar potassium bromide solution; the complexes of the P4 polymer formed with various hydrazine derivatives are used as sensitizing agents and the colour-sensitization is achieved by adding dyestuff IV. The results are summarized in Table 1 Table 7

Sign of [CD], Portioning the com plex is] of the re ducing agent / umol/mol Photographical characteristics Average Relative Fogging gradient sensitivity 18 0 c 30 oc 2 min 10 min Control - - 1.35 100 0.08 0.18 P4/S 1 25 49 1.40 215 0.07 0.15 P4/S 2 25 48 1.20 122 0.05 0 15 P4/S8 25 48 1 26 280 Q.09.0 25 P4/S 10 25 48.1.29 160 0.10 0.19 P4/S 12 25 48 1.36 127 0.05 0.13 P4/S 13 25 48 1.26 148 0.04 0.12 P4/S.14 25 48 1.42 196 0.05 0 1.8 Ln 1 It can be stated on the basis of the above data that each of the inclusion complexes shows a sig nificant sensitizing effect.

Exam21e 5 The process described in Example 1 is followed, except that the P1/S1 inclusion complex is combined with sensitization by sulfur and gold or sulfur and palladium, respectively by using the following ratios:

P1/S1 = 48 / umol/mol (R); Na2S2 0 3 = 48 / UM01/M01 (S); NH 4 Ac (SCN) 2 = 55 / UM01/M01 (AU); K 2 PdCl 6 = 60 / UM01/M01 (PS). The molar ratio in the inclusion complex, i.e.

[WI/ [S] = 50. The results are summarized in Table 8.

Table 8

No. order of Average Relative 0 Fogging 0 adding the gradient sensiti- is c 30 c Note sensitizing vity 2 min 10 min agents 1 Control 1.58 100 0.06 0.12 No sensitizer 2 R 1.33 219 0.05 0.14 3 S+AU 1.86 377 0.08 0.18 4 R+S+AU 2.05 720 0.08 0.36 R+S+AU solution 1.76 550 052 S1 in aqueous 6 S+R+AU 1.66 940 0.09 0.44 1.53 690 0.11 0.46 7 S+AU+R 1.29 53 0.09 0.40 S1 added befor R+S+AU precipitation 9 R+S+M 1.92 686 0.06 0.32 The above results indicate that the inclusion complex of the reductive sensitizing agent can well be combined with other sensitizing substances whereby a higher gradation and sensitivity as well as a lowerfogging value are achieved in comparison to the reducing agent used in an aqueous solution. It can also be seen that phenylhydrazine introduced as an inclusion complex shows a synergism with sulfur and gold sensitizers, however such effect is not induced by the reducing agent used as a jo solution prepared with only water(see the sensitivity data of lines 4 and 5 of Table 8 in comparison to the sum of the sensitivities obtained in Examples2 and 3).

1 29 ON 53-026

Claims

CLAIMS: 1. A process for the reductive sensitization of silver halide photographic emulsions by precipitating silver halide crystals in a protective colloid solution, growing them to the size required and optionally removing the ions which are present in excess, said reductive sensitization comprising introducing into the photographic emulsion an inclusion complex comprising (a) a cyclodextrin of general formula (I), CD - (0 - R) L. (I) (wherein CD is a cyclodextrin molecule, R is 2 hydrogen or an R 2 CO 2H, R 2 so 3H, R 2 NH 2 or (R)2 NH group wherein is a C 1-5 straight or branched chain alkylene group; and is 1, 2, 3, 4 or 5), a cyclodextrin polymer of general formula k 20 or (b) (11) 1 (OR 2')S OR 2 (OR 21) t OR 2 Dy- t( 0-(CH2) CH-R-0)m-CD'-PO-CH 2-CH-R')n-X3r3 p (II) (wherein CD 1 is a group derived from the $-cyclodextrin molecule by removing (p + s) hydroxyl groups; R and R' independently of one another each stand for a CH 2 -CHOH-CH 2-, -CH 2 CHOH-CH 2-1 -CH 2-0-(CH 2)2-O-CH2-CHOH-CH2-1 -CH2-0-CH2CHOH-CH 2- or -CH 2-0-(CH 2)4 - 0-CH 2 -CHOH-CH 2group; X R 1 R 2 R21 R 3 is R 4 and R 5 r p s and t is an -OR 1, -OR 2 or -NR 4 R 5 group; is hydrogen or, when r is other than zero, a group derived by removing a hydroxyl group from a p- cyclodextrin molecule; is hydrogen, -PO(OH) 2 or -SO H, -R I-NH(CH 2) m - CO 2 H, -R 3_ (CO 2 H) U, -R -SO 3 H or -R 3 -NR 4 R 5 group or a group derived by removing a hydroxyl group from a p-cyclodextrin molecule; is hydrogen, -PO(OH) 2 or -S03 H, -R -NH(CH2)m -CO 2 H-, -R 3_ (CO H), -R 3_ SO H or -R 3 -NR 4 R 5 group; is a C 1-10 group derived from an alkane, the terminal carbon atom of which standing near to the polymer chain may optionally be substituted by an oxo group; independently from one another each stand for hydrogen or a C 1-4 alkyl group; m and n are each an integer from 0 to 25; is an integer from 0 to 17; is an integer from 1 to 18; independently from one another are each an integer from 0 to 7; and U is an integer from 1 to 5) with the provisos that (i) m, n, r, t and u may be various within a unit; and (ii) (p + s) is equal to or lower than 18, with an average molecular weight of 2000 to 15000 containing 30 to 70% of cyclodextrin, and a hydrazine derivative of genral formula (III), Z U R 1-NH-NH-R 2 (111) (wherein 35 R 1 is a quinolyl, pyridyl or cyclohexyl group or a group of any one of general formulae (a) to (h):

1 - 31 R 3 (a) N R5,,i S _ 'S (c) R 6 1 S ' ll' R 6 N (e) H R 6 N 6, 1 1 ' "--ir R (g) 01 R4 (b) R 4 N -- J_ R 6 1,0 RS (d) R5 0 6 1 1 y, R N (f) C5' 1 'I 1- 41 R 4 (h) (wherein R 2 R3 is hydrogen or a phenyl group; is hydrogen, halogen, a C 1-4 alkyl or alkoxy group or sulfonamido group; R 4 and R5 are each hydrogen or halogen; and R 6 is Cl-4 alkyl or an alkoxy group, in an amount of 100 to 500 Pmol/mol, preferably to 100 Pmol/mol of silver halide as calculated for the reducing agent, the molecular ratio of the cyclodextrin monomer in the inclusion complex to the sensitizing agent being between 4:1 and 80:1.

2. A process as claimed in claim 1 wherein the molecular ratio of the cyclodextrin monomer in the inclusion complex to the sensitizing agent is betwen 10:1 and 50:1.

3. A process as claimed in either of claims 1 and 2, which comprises combining the reductive sensitization with sensitization using sulfur and gold, the inclusion complex being added before or after the introduction of the sulfur and gold compound or therebetween.

4. A process as claimed in either of claims 1 and 2, which comprises combining the reductive sensitization with sensitization using sulfur and an element of group VIII of the periodic table, the inclusion complex being added before or after the introduction of the compounds containing sulfur and the element of group VIII, respectively or therebetween.

5. A process as claimed in claim 4 wherein the reductive sensitization is combined with sensitization using sulfur and Ir, Pt, Pd or Ru.

1 1 1 - -33 -

6. A process as claimed in any of the preceding claims which comprises adding the inclusion complex of the reductive sensitizing agent before precipitating the silver halide crystals or during the period of 5 the crystal growth or thereafter.

7. A process as claimed in claim 1 substantially as herein disclosed.

8. A silver halide photographic emulsion when reductively sensitized using a process as claimed in any one of claims 1 to-7.

Published 1988 at The Paten', Offlee. S-.ate House 66 -1 High Volborn. Lord,= MICIF. 41P Furtb er e-jies rnay be obtaired from The Paxent M& "TRn prin- e- bl;, lijtil,'lex teebmcl.cs ltd St Mary Cray. Kent. Con. 1,87.