US3658544A

US3658544A - Light-sensitive silver halide color-photographic emulsions

Info

Publication number: US3658544A
Application number: US848069A
Authority: US
Inventors: Masakuni Iwama; Isaburo Inoue; Teruo Hanzawa; Kenro Sakamoto; Takaya Endo
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 1968-08-12
Filing date: 1969-08-06
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25
Also published as: GB1268852A; DE1940719A1

Abstract

A light-sensitive silver halide color-photographic emulsion which contains as protected coupler, a compound of the general formula WHEREIN B is a coupler residue; NR1 are hydrogen atoms, or at most one of nR1 is a C1 to C4aliphatic hydrocarbon radical, attached to the terminal carbon of the alkylene chain and the remaining (n-1)R1 are hydrogen; R2 is a C7 to C18-aliphatic hydrocarbon radical; X is a group capable of bonding the coupler residue with an acylamino group; N IS 2 OR 3; AND Q IS 1 OR 2.

Description

United States Patent Iwama et al.

[ 1 Apr. 25, 1972 LIGHT-SENSITIVE SILVER HALIDE COLOR-PHOTOGRAPHIC EMULSIONS [72] Inventors: Masakuni lwama; lsaburo lnoue; Teruo Hanzawa; Kenro Sakamoto; Takaya Endo, all of Tokyo, Japan [73] Assignce: Konishiroku Photo Industry Co., Ltd., Chuo-ku, Tokyo, Japan l22| Filed: Aug. 6, I969 [2|] Appl. No: 848,069

[30] Foreign Application Priority Data Aug. 12, 1968 Japan ..43/56727 [52] US. Cl ..96/100, 250/65 [5 l] Int. Cl t ..G03c 1/40 [58] Field of Search ..96/l00, 9

[56] References Cited UNITED STATES PATENTS 2,652,329 9/l953 McCrossen et al. ..96/10O Klinger ..96/l00 Misu et al. ..96/l00 Primary Examiner-J. Travis Brown Attorney-Waters, Roditi, Schwartz & Nissen 5 7] ABSTRACT A light-sensitive silver halide color-photographic emulsion which contains as protected coupler, a compound of the general formula LIGHT-SENSITIVE SILVERHALIDECOLOR- PHOTOGRAPHIC EMULSIONS This invention relates to a light-sensitive color photographic emulsion. More particularly, it relates to a light-sensitive silver halide color-photographic emulsion which comprises, as a protected coupler, a new compoundof the general formula B-(Xhq-NHCO-(CFH) P000112 wherein B is a coupler residue; "R are hydrogen atoms, or at most one of the nR, is a C to C aliphatic hydrocarbon radical attached to the terminal carbon atom of the alkylene chain and the remaining '(n-l )R, are hydrogen atoms; R is a C, to C aliphatic hydrocarbon radical, X is a group being capable of bonding the coupler residue with an acylamino group, n is 2 or 3 and q is l or 2.

Various compounds have been proposed as protected couplers heretofore. However, they usually suffer from'individual disadvantages. Few protected coupler compounds are known which can be prepared at an inexpensive cost'and in high purity.

For example, a coupler compound of the formula (I311- Eeln o1--- NllCO(J1I0tC5H is disclosed in US. Pat. No. 2,801,171. Although this compound advantageously has good solubility in high boiling-solvents, it must be prepared from a very expensive starting material and is difficult to purify.

Another coupler of the formula ii I o0 (CHzhiCH;

CONHCHzCHzNHCOCHiCH2N\ is disclosed in Japanese Pat. Publn. No. 2835/1964. It also has good solubility in high boiling solvents. However, it is quite expensive because its oleophilic portion must be prepared through several steps from an expensive starting material.

In view of the above-mentioned disadvantages of the prior art, it is one object of the invention to provide a light-sensitive color-photographic emulsion which contains a coupler compound, with superior photographic characteristics to those of conventionally known coupler compounds. Another object of the invention is to provide a light-sensitive color-photographic emulsion which when coated can form a stable light-sensitive color-photographic film free from crystallization of the coupler contained therein. Still another object of the invention is to provide a new coupler compound which can be obtained at an economical cost and in high purity.

Coupler compounds usable 'in thepresent invention have the following advantages:

1. They can be prepared by a simple and economical way starting from a long-chain alcohol easily available in the market,

2. theyhave good solubilities in dibutyl phthalate, tricresyl phosphate or the like high boiling solvents, so that 'a highly concentrated, stable coupler dispersion is obtainable because of the possibility of'reducin'g solvent amounts required for couplers, and

3. they are unlikely to crystallize from the emulsion or coating containing same, because of their low melting point.

These couplers are very useful as protected couplers in the art of color photography and can be synthesized in the following way.

A long-chain alcohol and a dibasic. carboxylic acid anhydride (e.g.,. succinic anhydride or glutaric anhydride) are brought into reaction to form a dibasic carboxylic acid monoalkyl ester, which is then reacted with thionyl chloride. The acid chloride thus obtained is condensed with a coupler component having an amino group thereby obtaining the desired coupler compound. The above process can be represented by the following chemical formulas.

In the-"above formulas, R R,, B, X, n and q have the same meanings as defined above, and p is l or 2.

In the general formula of the coupler compounds of the invention, the coupler residue (B) is a residue ofa phenolic hydroxy-bearing compound (e.g., phenol, naphthol, etc.) or a derivative thereof or of an active methylene-bearing compound (e.g., pyrazolone, indazolone, acylacetanilide, etc.) or a derivative thereof. Further, the group X may be any group capable of bonding the coupler residue with an acylamino group and it includes, for example, an imino group or a residue of an imino-bearing alkylene or arylene derivative.

Typical compounds of the couplers of the present invention are listed below, without limiting the scope of the invention thereto.

-uHco cmco OCH: NHCOCHzCHgCOOCnH-g;

(CHQaC CO CHzCONH- (a NHCOCHzCHgCOOCuHg;

Q-NHCO-iH-GO l OCH; NHCOCHICHZCOOCHHN -NHCO-([}HCO OCOCH; OCH; NHGOCHzCILCOOCnHn 5 c11, -c-NHc0 omcmcoo 0121-1 OHa N NHCOOHzCHgCOOCnHn (BOOK:

NHC ClIzClIrC O O 013" Typical synthetic procedures for these couplers will be mentioned below.

Synthesis Example (1) 105 g. of succinic anhydride is heated on an oil bath. To the resulting melt, 187 g. of n-dodecyl alcohol is added, and the mixture is stirred at l20-125 C.'for 3 hours. After cooling, the solidified mass is recrystallized from hexane. Succinic acid mono-n-dodecyl ester melting at 44.5-45.5 C. is obtained. 143 g. of this ester is mixed with 140 g. of thionyl chloride and the mixture is allowed to stand overnight. The thionyl chloride is removed by distillation under reduced pressure. The remaining mass, succinic acid mono-n-dodecyl ester chloride, is passed to the next acylation.

To the mixture of 500 ml. of glacial acetic acid and 9.0 g. of anhydrous sodium acetate, 28.0 g. of a-(3-aminobenzoyl)-2- methoxy-acetanilide and 40.0 g. of the above-resulted chloride are added. The mixture is heated on a water bath for 2 hours and then poured into water. The precipitate formed is collected by filtration, washed with'water and then dried. The crude product is recrystallized from a mixed solvent of benzene and hexane thereby to obtain the coupler (I indicated before, as a white powder melting at 'l03-l0'4 C.

Yield 40.0 g. (74 percent on theoretical basis). The elementary analysis shows the following.

Calcd.

N 5.0 Found 4.7

By repeating the above procedures in the substantially same manner, the couplers (2), (3) and (4) can be obtained.

aminobenzamido)-5-pyrazolone is suspended in the mixture of 200 ml. of acetonitrile and 40 ml. of pyridine, 42.0.g. of succinic acid mono-n-dodecyl ester chloride is added to the suspension, which is then boiled for 1 hour. Then, this suspension is added with water and the separated oil is extracted with ethyl acetate. The extract is washed with water, dried and then freed from the solvent. The remaining oil is dissolved 'in methyl alcohol and the resulting solution is passed through ion-exchange columns individuallypacked with Amberlite C0 120 and Amberlite CG 400 of Ro'hm & Haas Co.,'U.S.A.-Solvent is removed from the treated solution by distillation and the remaining mass is recr'ystallized from a mixed solvent of benzene andhexane. A pale yellow'powder melting at 77-78 C. is obtained. This is the coupler (6), indicated before, Yield 39 g. (59percent on theoretical basis).

By repeating the above procedures in substantially the same manner, the couplers (5) to (11) and (15) to (16), indicated before. are obtained.

Nitrogen analysis hydrochloride is mixed with 550 ml. of acetone and 25.0 g. of diethyl aniline. The resulting mixture is added with 40.0 g. of succinic acid mono-n-dodecyl ester chloride and then stirred for 1 hour, followed by boiling for l hour. The reaction mixture is filtered, and the filtrate is concentrated and then the remaining oil is added to a mixture of conc. HCl and water. The solidified oily mass is collected by filtration, washed with water, dried and then recrystallized from acetonitrile thereby obtaining 30.0 g. (yield 65 percent) of a white powder melting at 72-74 C. The product is the coupler (14). The nitrogen analysis shows the following.

N Calcd. 3.04% Found 3.19%

Synthesis Example (4) 3.6 g. of p-anisidine, 40.0 ml. of water, 100 ml. of concentrated hydrochloric acid and 2.4 g. of sodium nitrite are brought into reaction, followed by addition of ml. of ethyl alcohol.

The diazotized solution thusprepared is added at 5-l0 C. to a solution of 12.8 g. of the coupler (8) in 128 ml. of pyridine. The resulting mixture is stirred for 3 hours and then diluted with 300 ml. of water; 128 ml. of concentrated hydrochloric acid is addeclv thereto, and the separated precipitate is collected by filtration, washed with water, dried and then recrystallized from ligroin thereby to obtain 1 1.6 g.

(yield, percent) of orange powder melting at l06-l07 C.

Nitrogen analysis 1%) Coupler mp. (C.) Calcd. Found No. (13) 106-107 10.42 10.26 No. l2) 85-87 10.88 10.70 No. 17) 126-127 9.68

In order to prepare a light-sensitive color-photographic emulsion of theinvention, any one of the couplers prepared as above is dissolved in a high boiling solvent (b.p. C. .or higher) such asxtricresyl'phosphate, dibutylphthalate, etc. or a low boiling solvent such as butyl acetate, butyl propionate, etc. or a mixture of both. The thus prepared solution may be mixed with an aqueous gelatinous solution containing a surface active agent.

Then,the coupler dispersion thus obtained is emulsified by means of a high speed rotary mixer or colloid mill and'then added directly to a light-sensitive silver halide photographic emulsion, which is coated on a suitable support (e.g., film base, baryta paper, etc.), followed by drying to remove the majority of the low boiling solvent. Alternatively, the emulsified coupler dispersion is set and extruded to noodle form, followed by water-washing or the like procedure to remove e.g., cyanine dyes, merocyanine dyes, etc., also may be contained therein.

A light-sensitive silver halide color-photographic material obtained from the above-mentioned light-sensitive silver hathe low boiling solvent. Then it is added to a light-sensitive 5 lide color-photographic emulsion can be subjected to exposilver halide photographic emulsion, which in turn is coated sure by actinic irradiation (oz-ray, B-ray, X-ray, visible ray, inon a support and dried to obtain a light-sensitive silver halide frared ray, etc.) and then treated with a liquid developer conphotographic material. It should be understood that the taining a p-phenylene diamine type compound. The resulting manner of incorporation of the couplers into a light-sensitive developed image is bleached and fixed, thereby giving a highly photographic emulsion as mentioned above is merely illustra- 10 transparent color image having good spectral absorption tive and does not limit the scope of the invention in any way. characteristics.

The preferred amount of the coupler in photographic emul- Typical p-phenylene diamine type compounds which are sion usually is 10-100 g. per mole of silver halide. However, contained as the main active ingredient in the liquid developer this is not critical and can be varied depending on the purpose are the sulfates, sulfites and hydrochlorides of N,N-diethyl-pof the final use. The light-sensitive silver halide emulsion may 15 phenylene diamine, N-ethyl-N-B-methane-sulfonamidoethylcontain any type of silver salts including silver chloride, silver 3-methyl-4-aminoaniline, N-ethyl-N-hydroxyethyl-p-pheniodide or silver chloroiodide. Further, said emulsion may conylene diamine, N-ethyl-N-hydroxyethyl-Z-methyl-p-phenylene tain any sensitizer, for example, sulfur sensitizer, polyalkylene diamine, N,N-diethyl-Z-methyI-p-phenylene diamine and the oxide sensitizer, noble metal sensitizer, etc. Other photolike. graphic additives may exist in the photographic emulsion, 20 The melting points of the couplers of the present invention which are antifoggants, stabilizers, anti-stain agents, anti-irare compared with those of known couplers having a similar radiation agents, coating aids, etc. Known optical sensitizers, structure in Table 1.

TABLE 1 Coupler Structure M.p. C.)

Coupler (1) 103-10 CrzHnCOOCHzCHzCONH- OCH;

l C O CHzC O NH- Coupler of U.S.P. 2,875,057 126-127 liCsHn- OCH2CONH (|)CH2 l l tCsHti coomcomr Coupler (6) 77-78 CH2(|3NH C 0 0:0 N

N NHCOCHzCHzCOOCrzHzs Coupler of U.S.P. 2,6l8,641 138-139 (|JHzfi-NHCO 0=o N l Nnooonlo I.C5H|1 I tCsH Cl- Cl Coupler (14) OH 72-74 Cl- NHCOGHnCHaCOOCnHzs Coupler 0lU.S.P.2,801,171 123-124 The above data clearly indicate that the couplers of the EXAMPLEl present invention have remarkably lower melting points than the conventionally known couplers. g. of the coupler 1), indicated before, is dissolved at Further, some test results demonstrating the high solubility C. in th mixtur f 20 ml- Of dibutyl phthalate and 60 ml. of of the couplers of the present invention in high boiling 501- 5 butyl acetate. The resulting clear solution is mixed with 10 ml.

vents are shown in Table 2. Degree of solubility is expressed in of an aqueous solution of 10 percent Alkanol B (alkyl terms of the dibutyl phthalate amount (ml.) required for disnaphthalene sulfonate, manufactured and sold by Du Pont, solution of 1.0 g. of the particular coupler at 60C. U.S.A.) and 200 ml. of an aqueous solution of 5 percent TABLE 2 Dlbutyl phthalate Coupler Structure amount (ml.)

Coupler (1) 5.0

C 2H25COOCHzCH2CONH- OCH; COCHzCONH- Coupler 0i U.S.P. 2,875,051.... 7. 5

tCaHn- --OCH2CONH- OCH! tCsHn ooomcoun Coupler (6) 1. 5

(IJH2('TNH c o O=C N \N/ NHCOCIIzCHzCOOCuHzr (ll-@Cl l 01 Coupler of U.S.P. 2,618,641.. 2.0

(|3H2CNHCO- O=C N N/ NI{COOH2O-'- tCsI-Iu tCsHn Cl Cl Coupler (14) 0H i 2.0

01- NHCOCHrCHzCOOCnIIzs Coupler of U.S.P. 2,801,171 0H 3.0

01- NHC O(|JHO tGsHu C2H5 HaC t DH" The above data clearly indicated that the couplers of the gelatine. The mixture is treated by means of a colloid mill. present invention are superior in solubility in high boiling sol- The thus prepared coupler dispersion is added to 1 kg. of a vents to the conventionally known couplers, and this affirms high speed gelatino silver iodobromide emulsion, which in the usefulness of our couplers as protected couplers in colorturn is coated on a film base and dried. A light-sensitive photophotography. graphic film having a stable light-sensitive layer is obtained.

Accordingly, it can be understood that a light-sensitive This photographic film is exposed to light in the usual silver halide color-photographic emulsion of the invention manner and then treated at 20 CIfor l 0 minutes with a liquid which comprises a coupler of the above-defined general forde eloper of the following formulation:

mula is quite free from crystallization of the coupler, with the result that said emulsion can give an excellent color image havinggood spectral absorption characteristics and good N,N-diethyl-p-phenylene diamine transparency, due to nonexistence of irregular spectral abhydrochloflde g sor ion Anhydrous sodium sulfite 2.0 g p Sodium carbonate monohydrate 82.0 g Now the following examples will serve to show the invention potassium bromide 20 g in detail, without limiting the scope of the invention thereto. Water to make up 1,000 ml.

Potassium ferricyanide Potassium bromide Water to make up 1,000 ml.

The film is washed with water for minutes and then treated for 5 minutes with a fixing solution of 250 g. of sodium thiosulfate in 1,000 ml. of water. Washing with water for 20-25 minutes is made, followed by drying. A brilliant yellow color image having absorption maximum at 440 my. is obtained.

Substantially the same procedures as above are repeated but using the coupler (6) or coupler instead of the coupler 1 A clear magenta or cyan color image having an absorption maximum at 540 m or 670 mu, respectively, can be obtained.

EXAMPLE 2 10 g. of the coupler (2), indicated before, is dissolved at 50 C. in 10 ml. of tricresyl phosphate and 30 ml. of butyl acetate. The resulting clear solution is mixed with 5 ml. of an aqueous solution of 10 percent Alkanol B and 800 ml. of an aqueous solution of 5 percent gelatine. The resulting mixture is treated in a colloid mill.

The coupler dispersion thus obtained is added to 500 g. of a light-sensitive gelatino silver iodobromide emulsion, which in turn is coated on a film base and dried.

The light-sensitive silver halide photographic film thus obtained is exposed to light and then treated at C. for 10 minutes with a liquid developer of the following formulation:

Methol 3.0 g. Anhydrous sodium sulfite 60.0 g. Hydroquinone 6.0 g. Anhydrous sodium carbonate 50.0 g. Potassium bromide 1.0 g.

Water to make up 1,000 ml.

After stopping, film hardening and water-washing in the usual manner, the film is further subjected to secondary exposure to light and then treated at 20 C. for 10 minutes with a liquid developer of the following formulation:

N,N-diethyl-p-phenylene diamine hydrochloride Anhydrous sodium sulfite Sodium carbonate (monohydrate) 8 Potassium bromide Water to make up 1,000 ml.

The film is then treated by stopping, fixing, water-washing and bleaching in the usual manner and then washed with running water for 20 minutes and dried. A yellow color positive image having good transparency and having an absorption maximum at 445 mu is obtained.

Substantially the same procedures as above are repeated but using the coupler (8) or 16) instead of the coupler (2). A clear magenta or cyan color image having an absorption maximum at 535 mp. or 680 mu, respectively, can be obtained.

EXAMPLE 3 The light-sensitive silver halide photographic film thus prepared, after light exposure, is treated at 20 C. for 10 minutes in a developing bath of the following formulation:

N-ethyl-N-hydroxyethyl-p-phenylenediamine hydrochloride 2.5 g Anhydrous sodium sulfite 2.0 g Hydroxylamine hydrochloride 1.0 g Sodium carbonate (monohydrate) 82.0 g Potassium bromide 2.0 g

Water to make up 1,000 ml.

The film is then immersed in a stopping bath consisting of 10 ml. of glacial acetic acid, 3.0 g. ofsodium hydroxide and 1,000 ml. of water, and immediately thereafter, immersed in a film hardener-containing fixing bath for 4 minutes. After waterwashing for 10 minutes, the film is treated at 20 C. for 8 minutes in a bleaching bath of the following formulation:

Ethylenediamine tetraacetic acid disodium salt 40 g. Ferric chloride 30 g. Sodium carbonate (monohydrate) 20 g. Potassium bromide 30 g. Sodium thiosulfate 200 g.

Water to make up 1,000 ml.

After washing with water for 20 minutes, the film is immersed in a stabilizing bath for 2 minutes and then dried. A cyan color image having good light fastness and humidity resistance and having an absorption maximum at 680 mp, is obtained.

EXAMPLE 4 2.0 g. of the coupler (13), indicated before, is dissolved at 60 C. in 2 ml. of dibutyl phthalate and 6 ml. of butyl acetate. The resulting clear solution is mixed with 1 ml. of an aqueous 10 percent Alkanol B solution and 20 m1. of an aqueous 5 percent gelatine solution.

The coupler dispersion thus prepared is added to g. of a high speed light-sensitive gelatino silver iodobromide photographic emulsion, which in turn is coated on a film base and dried.

After lightexposure in the usual manner, the light-sensitive photographic film is treated with a color developer as used in Example 1. A yellow color positive image having an absorption maximum at 440 my. and a magenta color image having an absorption maximum at 540 mp. are obtained.

Substantially the same procedures as above are repeated but using the coupler 17) instead of the coupler 13). A red color positive image having an absorption maximum at 520 mp. and a cyan color image having an absorption maximum at 670 mp. are obtained.

EXAMPLE 5 5.0 g. of the coupler 15), indicated before, is dissolved at 60 C. in 5.0 ml. of dibutyl phthalate and 15 ml. of butyl acetate. The resulting clear solution is mixed with 2.5 ml. of an aqueous 10 percent Alkanol B solution and 50 ml. of an aqueous 5 percent gelatine solution. The mixture is treated by means ofa colloid mill.

The coupler dispersion thus prepared is added to 500 g. of a light-sensitive silver chloride photographic emulsion sensitized at the wavelength region of red light. This emulsion in turn is coated on a film base and dried.

The light-sensitive photographic film thus prepared is exposed to X-ray irradiation in the usual manner and then treated at 20 C. for 10 minutes with a developer as used in Example 1. After stopping, film-hardening and water-washing in the usual manner, the treated film is subjected to secondary exposure to yellow light (exposure time 30 seconds, Agfareprocolor separation filter used) and then treated at 20 C. for 10 minutes with the same developer as above. Stopping, fixing, bleaching, water-washing and drying are carried out in the usual manner. A clear yellow color image on a blue background is obtained.

13 I EXAMPLE 6 5.0 g. of the coupler (6) is dissolved at 60 C. in the mixture of .0 ml. of dibutyl phthalate and ml. of butyl acetate. The resulting clear solution is mixed with 2.5 ml. of an aqueous 10 percent Alkanol B solution and 50 ml. of an aqueous 5 percent gelatine solution. The resulting mixture is treated in a colloid mill.

The thus obtained coupler dispersion is added to 500 g. of a high speed light-sensitive silver iodobromide photographic emulsion, which in turn is coated on a film base and dried to obtain a light-sensitive silver halide photographic film.

Separately, a gelatine layer having a dry thickness of about 5 p. is prepared on a cellulose triacetate film. On that layer, a tritium-labelled thymidine solution is spotted at the ratio of 10 ,u.c. (micro-count) per square centimeters. Then, spotting is repeated by using double dilution of the said solution. By repeating this method, a standard tritium radiation source having a stepwedge of radioactivity in geometric progression with an equal ratio of 2 is prepared.

The gelatine layer of this radiation source is brought into contact with the light-sensitive layer of the light-sensitive photographic film and the resultant composite is allowed to stand for IS hours in a dark room. At the end of that time, the gelatine layer is removed and the photographic film is treated by the developing procedures mentioned in Example 1. A magenta color image which indicates the existence of the radioactive substance is formed at the position which corresponds to the radioactive source of the gelatine layer.

What we claim is:

l. A light-sensitive silver halide color-photographic emulsion which contains, as protected coupler, a compound of the general formula wherein B is a coupler residue;

nR are hydrogen atoms, or at most one of nR, is a C to C,-

aliphatic hydrocarbon radical, attached to the terminal OClIg NHCOCHrCHzCOOCuHza 3. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula NBC 0 CHzCHzC O 0 0121125 4. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula 5. A light'sensitive silver halide color-photographic emulsion as claimed in 'claim 1, wherein said protected coupler is a compound of the structural formula NH-NHC 0 omomo o 0 CrrHzs 6. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula NIICO CHzCHzCO O C 11 7. A light-sensitive silver halide colorphotographic emulsion as claimed in'claim 1, wherein said protected coupler is a compound of the structural formula CONIICHZCIDNHCO (CHz)3-CO O CHgCH-(LHD 8. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula CONHCHzCHzNHCO (CH2)a-CO O CHzCH-C4H0

Claims

2. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula
3. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula
4. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula
5. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula
6. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula
7. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula
8. A light-sensitive silver halide color-photographic emulsion as claimed in claim 1, wherein said protected coupler is a compound of the structural formula