US3887381A - Spectral sensitization of photographic light-sensitive emulsion - Google Patents

Abstract

A method for sensitizing spectrally, a photographic sensitive emulsion, which comprises: A. DISSOLVING A METHINE DYE CONTAINING AT LEAST ONE WATERSOLUBLE GROUP IN AN ORGANIC SOLVENT HAVING A WATER SOLUBILITY OF 10% BY WEIGHT OR LESS AT 35* C, b. dispersing the solution in a member selected from the group consisting of water and a hydrophilic colloid of 2% by weight or less, and C. SUBSEQUENTLY TO THE DISPERSING STEP, ADDING THE DISPERSION TO A LIGHT-SENSITIVE EMULSION.

Description

United States Patent Shiba et a1.

June 3, 1975 SPECTRAL SENSITIZATION OF PHOTOGRAPHIC LIGHT-SENSITIVE r EMULSION Inventors: Keisuke Shiba; Motohiko Tsubota,

both of Minami-Ashigara, Japan Assignee: Fuji Photo Film Co., Ltd., Minami- Ashigara, Japan Filed: Mar. 30, 1973 Appl. No: 346,386

Related US. Application Data [56] References Cited UNITED STATES PATENTS 2,519,001 8/1950 Sprague 96/140 3,469,987 9/1969 Owens et al 96/120 Primary Examiner-J. Travis Brown Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A method for sensitizing spectrally, a photographic sensitive emulsion, which comprises:

a. dissolving a methine dye containing at least one watersoluble group in an organic solvent having a water solubility of 10% by weight or less at 35 C,

b. dispersing the solution in a member selected from the group consisting of water and a hydrophilic colloid of 2% by weight or less, and

c. subsequently to the dispersing step. adding the dispersion to a light-sensitive emulsion.

28 Claims, 13 Drawing Figures PATENTED 3 FIG. I

FIG. 3 100- FIG. 5 100 FIG. 2

0 500 s nm FIG. 4

BY M 2a sf u faK ATTORNEYS PATENTEDJUN 3 ms 3.887 381 SHEET 2 A A d (%1 We} 50 0 v v G I v nm nm nm WAVELENGTH SPECTRAL SENSITIZATION OF PHOTOGRAPHIC LIGHT-SENSITIVE EMULSION CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation Application of our earlier copending Ser. No. lll,5()l filed on Feb. 1, 197 l now abandoned, which claims priority from Jan. 30, 1970, based on Japanese Patent Application No. 823 1/70.

BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to a method of sensitizing spectrally, a photographic light-sensitive emulsion necessary for the production of photographic light-sensitive materials and more particularly, it is concerned with a method of adding a dye to an emulsion.

2. Description of the Prior Art It is well known that the technique of spectral sensitization, whereby the light-sensitive wavelength region of a light-sensitive material is sufficiently extended to the visible region, is important for the production of photographic light-sensitive materials and, in particular, is essential for color photographic light-sensitive materials. In general, the step of spectral sensitization resides in dyeing a light-sensitive element dispersed in a photographic light-sensitive emulsion, such as grained silver halide, zinc oxide, cadmium sulfide, titanium oxide, organic silver complexes or organic high molecular weight photoconductors, by the addition of a suitable sensitizing dye. Many efforts have been made with respect to the spectral sensitization of silver halide emulsions. When a sensitizing dye is added to a silver halide emulsion, the adsorption state on the surface of silver halide microcrystals varies markedly with the conditions of said addition, which have a great influence upon photographic properties, such as fogging action, sensitivity, distribution of spectral sensitivity, desensitizing action, stability of sensitivity, and so on. This is disclosed in C. E. K. Mees, The Theory of the Photographic Process (1954) lld Ed, chapter 12, pages 430-500 (McMillan). The most important condition for providing a stable spectral sensitization while keeping a high sensitivity is in fact that every molecule of a sensitizing dye to be added should adsorb soundly on the adsorption site of light-sensitive silver halide crystal without interaction with a binder and without aggregation or deposition in a binder. It also resides in the fact that a sensitizing dye should adsorb uniformly, neither too much nor too little, on every crystal of lightsensitive silver halide dispersed in a light-sensitive emulsion.

Many methods are known for adding sensitizing dyes to light-sensitive emulsions. The most commonly used method consists in dissolving a dye in a water-miscible organic solvent such as acetone, methanol, ethanol, propanol, methyl cellosolve or pyridine and adding the dissolution to an emulsion. Some water may be also added to this organic solvent. See, for instance, French Pat. No. l,508,489. Furthermore, it may be used as an aqueous solution. The method disclosed in Japanese Patent Publication No. 23,389/69 comprises adding a strong acid to a sensitizing dye having an axochrome of an amidinium ion to thus protonize and then adding the dye in the form of an aqueous solution to the emulsion. The method disclosed in Japanese Patent Publication No. 22,948/69 comprises dissolving a substantially water-insoluble sensitizing dye in a volatile organic solvent, adding the solution to a hydrophilic colloid and heating the mixture to remove the solvent, thereby dispersing the dye in the hydrophilic colloid. Many devices for dispersing dyes have been proposed; for example, as disclosed in US. Pat. No. 3,425,835.

However, these methods have many disadvantages. In the method using a water-miscible organic solvent, the organic solvent used tends to lower the surface activity of a coating agent coexistent to conglomerate an aqueous binder of colloidal character and, in the case ofa color photographic light-sensitive material, to briquette a coupler coexistent, so that a high speed coating of, for example, lOO m or more per minute would be very difficult to attain. Furthermore, when added, the organic solvent used is immediately mixed with water and the sensitizing dye adsorbs onto the binder before adsorbing on the silver halide crystal, or it aggregates by itself, so that only a weak spectral sensitization is provided. The method of adding in the form of an aqueous solution has a disadvantage that, in general, the sensitizing dye tends to be decomposed. The method mentioned above with reference to Japanese Patent Publication No. 22,948/69 may somewhat im prove the above-mentioned disadvantages but cannot avoid important disadvantages. A first disadvantage is that, since a substantially water-insoluble sensitizing dye is dissolved in an organic solvent and then dispersed to a hydrophilic colloid, the transferring or adsorbing speed of the dye molecule to the silver halide microcrystal is slower than that of the common method. Therefore, this method cannot be adapted to any high speed continuous process for making lightsensitive materials with advantage. Another disadvantage is that, in the case of applying a sensitizing dye to a color photo-emulsion containing any coupler, it is adsorbed by the coupler micells, coupler dispersing oil drops and surfactant micells around the oil drops. Accordingly, the transferring or adsorption of the sensitiz ing dye to the silver halide microcrystal is so hindered that only a weak spectral sensitization is given. A third disadvantage is a poor influence upon a photographic image obtained. The use of a hydrophilic colloid in the case of dispersion means further addition of the oil and hydrophilic colloid to the emulsion, all of which results in an increase in the thickness, which is a bar to thinning of the emulsion layer. Accordingly, it is preferred to decrease the amount of the hydrophilic colloid used to a large extent or to add immediately the dispersion in water to a light-sensitive emulsion.

SUMMARY OF THE INVENTION It is therefore the principal object of the present invention to provide a method for spectral sensitization whereby the above-mentioned disadvantages encountered when carrying out high-speed coating can be overcome, and the efficiency of the spectral sensitiza tion can be raised with a decrease in fog so as to be adapted to a high-speed continuous process for making a light-sensitive material.

Accordingly, the object of the present invention can be accomplished by employing a sensitizing dye in which at least one water-soluble group, such as carboxyl, sulfo and sulfate groups, is substituted on the dye molecule, and further employing an organic solvent having a water solubility of NW: or less at 35 C. However, a solvent having a preferably high vapor pressure and containing a hydroxyl or keto group is preferred. Such dye (which may be either a sensitizing dye or a socalled desensitizing dye) is dissolved in the abovementioned organic solvent considering its quantity required for complete dissolving, at a temperature of at least 35 C, and then dispersed in water or a hydrophilic colloid, the resulting dispersion being added to a photographic light-sensitive emulsion.

A feature of this invention lies in the chemical structure of the dye used or its characteristics; that is, positive introduction of a water-soluble group, preferably, to give a neutralor anionic property in aqueous systems. The water-soluble group applicable is a sulfo group, carboxyl group or sulfate group. A phosphate group may also be employed. Introduction of such watersoluble group can promote remarkably the transferring or adsorption of the dye from oil drops for dispersing the dye to silver halide microcrystals, while overcoming the hindering action of the coexistent substances, such as a hydrophilic binder, as much as or more than those methods commonly employed, Furthermore, surprisingly, the solubility into the organic solvent as defined above is markedly raised, in general, by a factor of 2 to 30 times. This means that the quantity of entrainment of the organic solvent or hydrophilic colloid into an emulsion is markedly reduced as compared with the commonly used method.

Another important feature of the invention lies in dispersing the dye with a markedly reduced amount of hydrophilic colloid or dispersing an oil in which the dye is dissolved without the need for a hydrophilic colloid.

IV I

l ca cu coo This method, as compared with the prior art, serves to advantage not only in the thinning of an emulsion layer but also in raising remarkably the efficiency of spectral sensitization and decreasing fog, since there is no aggregation of the dye during dispersing and no interaction with a hydrophilic colloid. In this case, the stability of the oil dispersion in which the dye is dissolved does not matter because the addition to a lightsensitive emulsion is carried out substantially immediately after the dispersion. This is very advantageous for the high-speed production of light-sensitive materials.

DETAILED DESCRIPTION OF THE INVENTION Illustrative of the preferable sensitizing dyes according to the present invention are methine dyes disclosed in US. Pat. Nos. 2,238,231, 2,493,748, 2,519,001, and 2,912,329; British Pat. Nos. 846,298 and 944,301 German Pat. Nos. 1,163,671, 1,177,481, and 1,072,467; Japanese Patent Publications Nos. 23467/65, 14112/65. 2607/68, 27165/67, 27166/67, 27167/67, 2606/68, 4930/68, 13823/68 and 27164/68; and sensitizing dyes obtained by the synthetic methods disclosed in U.S. Pat. Nos. 3,177,210 and 2,537,880; British Pat. No. 840,223; German Pat. Nos. 929,080, 1,072,765, and 1,028,718; and French Pat. No. 1,359,683. These dyes may be used alone or in admixture. The supersensitization including the combined use of dyes mentioned in Japanese Patent Publications Nos. 4932/68, 4933/68, 4936/68 and 22884/68 can with advantage be adapted for use in the present invention,

The methine dyes used in the examples which follow are shown below:

. CH CH COOH 5 C ll Gil S 3 v11, c-cn=cn-K N ia c11 Cli CH OCll CH COOll Br fi s {2 5 Cl N N Cl VIII C-CH=CHCH=C I c1 i n c1 (Cll Cll O) 2 (CH 50 I (LH LH O) (CH SO N&1

Dyes for comparison:

2 r 0 l J 111' I c-ca=c-cu--c I 3 z s z s m" C. ll S 2 f S I IV I c-c:a=c-ca=c I if u l I (1 H C 14 The organic solvent used in this invention must have Specific examples of the organic solvents which can a high dissolving property with respect to the dyes and be employed in the practice of this invention are given a good dispersiveness in the form of fine particles in as follows without limiting the same: water or a hydrophilic colloid. To this goal. the solubil- A. methylphenylcarbinol ity in water at 35 C should be at most 10% and the B. Z-pentanol vapor pressure should be preferably high. This require- C. diisobutylcarbinol ment is satisfied by having a relatively hydrophilic D. mesityl oxide group. such as hydroxyl, ester or keto group, with a hy- E. methyl isobutyl ketone drophobic aromatic or aliphatic radical. The organic F. isopropyl acetate solvents of alcohol ester or ketone type mentioned in G. cellosolve acetate Kirk-Othmer. Encyclopedia of Technology" Vol. l2, Hr 2-phenoxyethanol pages 654-686. in particular, Table 2, (I954 ed., The The dye solution using the organic solvent (as a sollnterscience Encyclopedia Co.) are suitable for use in vent) is then dispersed in water or a hydrophilic colloid the invention. of 2% by weight or less. The dye solution is obtained by heating and stirring, preferably by means of ultrasonic wave. The dispersing is ordinarily carried out in the presence of a surface active agent of the anionic type by mechanical high speed stirring or ultrasonic wave stirring or both. The hydrophilic colloid is gelatin, polyvinylpyrrolidone, its copolymer, cellulose derivative, alginate polymer, polyvinyl alcohol. Preferably, the polymer should contain a sulfo group or carboxyl group. The resulting dye dispersion is added under molten state to a photographic light-sensitive emulsion almost immediately after dispersing.

The light-sensitive emulsion used may be a hydrophilic colloid in which fine crystals of a light-sensitive material such as silver halide, titanium oxide, zinc oxide or cadmium sulfide, is dispersed. Preferably, a gelatino-silver halide such as -silver iodobromide. -silver bromide, -silver chlorobromide, -silver chloride, -silver iodochlorobromide or their mixtures is employed. Chemical aging may with advantage be carried out by any combination of reducing sensitization, sulfur sensitization and noble metal sensitization. In general, it may be applied to any lightsensitive emulsion to which spectral sensitization is required.

To the photographic emulsion spectrally sensitized according to the present invention may be added any additives which are ordinarily used. Illustrative of these are stabilizers, fog inhibitors. chemical sensitizers, hardeners, color formers, coating agents, development precursors, plasticizers and polymers, except for gela tin. A finished emulsion spectrally sensitized according to this invention is coated onto a suitable support, such as cellulose derivative film, polyethylene terephthalate film, baryta paper, paper, resin laminated paper, synthetic paper, glass sheet, plastic film or metallic sheet.

In the method of spectral sensitization according to this invention, the commonly used method or a supersensitization method may jointly be used. The quantity of addition may be an amount such as ordinarily used for a light-sensitive material, and preferably 1 X to l X 10 mol per one mol of the light-sensitive material.

A better understanding of the present invention will be obtained from the following examples, which are merely illustrative and not limitative of the present invention.

EXAMPLE 1 Table l Dye emulsion Amount X Organic Amount No Dye ll) g-mol solvent (ml) l l 500 H 100 2 II 500 H 100 3 III 500 H 100 4 IV 250 H 200 5 V 500 H 100 6 Vl 500 H 50 7 Vll 500 H 100 8 Vlll 500 H 100 Similarly, other dispersions of dyes (emulsion) 9 to 15 were obtained using other organic solvents.

One kg ofa silver iodobromide emulsion prepared in the conventional manner was weighed and made molten at about 40 C. 20 ml to 160 ml of the dye emulsions were added thereto directly after dispersing and held at 35 C while stirring, followed by standing. The silver iodobromide emulsion used was a sulfur-gold sensitized emulsion containing about 0.2 mol of silver per l kg emulsion and having an iodine content of 4.0 mol and an average grain size of about 0.5 micron.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, FIGS. 1, 2, 3, 4, 5, 6, 7 and 8, indicate the results obtained by measuring the percentage spectral absorption (A) of the emulsions after the passage of one minute, 30 minutes and minutes, after adding to the foregoing silver iodobromide emulsion each of the dye emulsions 1-8 corresponding to an amount of dye of 8 X 10 g mol; for example, l04 ml in the case of the dye emulsion l, per one kg of the silver iodobromide emulsion, followed by stirring at 35 C. In the figures, the results after one minute are shown by a dotted curve, the results after 30 minutes are shown by a broken curve, and the results after 75 minutes are shown by a real curve.

FIG. 9 shows the percentage spectral adsorption (A) obtained by adding ml of a solution of dye III in methanol having a molar concentration of l X 10 per kg of the same emulsion. FIG, 10 shows similarly, the percentage spectral adsorption obtained by the use of dye IV. The features of the spectral sensitization according to the present invention, namely, that the dye is transferred, adsorbed and stabilized on silver halide crystal more rapidly after its addition, will apparently be understood from FIGS. 1-8. Particularly, comparisons with FIG. 3 and FIG. 9, and FIG. 4 and FIG. 10.

EXAMPLE 2 One kg of the same silver iodobromide emulsion as that of Example 1 was weighed, made molten and spectrally sensitized by the use of the dye emulsion 4. The emulsion 15 was emulsified under the same conditions as in the emulsion 4 except that water was used in place of the 2% gelatin. The organic solvent G was used in place of H and was directly added to one kg of the above-mentioned emulsion and spectrally sensitized. Furthermore, the same emulsion was spectrally sensitized by the use of a methanolic solution of the dye IV of 5 X l0 mol. A hardener and coating agent was added to the emulsions, which were coated onto films to obtain film samples spectrally sensitized.

The thus obtained films were cut and subjected to light wedge exposure using a sensitometer of the S-type made by Fuji Photo Film Co, Ltd. A conversion filter of the David-Gibson type was adapted to a light source having a color temperature of 2666 K to give a color temperature of 5400 K and further, a blue filter of No.

K-3l made by Fuji Photo Film Co., Ltd., was used to give a blue light source, while a minus blue light source was obtained using a yellow filter of No. K-l2 made by Fuji Photo Film Co., Ltd. Using these light sources,

With regard to the hydrophilic colloids applicable to the present invention, applicants wish to point out that in addition to those already enumerated in the specification, polyacrylic acid polymers, maleic anhydride light wedge exposures of blue and minus blue were car- P y POIYVlliylbenlenesulfonatei and the like 3T8 i d r, equally applicable. Also, it is to be pointed out that the The exposed films were then developed for It] min terms p y inylpyrr li n and polyvinyl alcohol utes and fixed, and their density was measured by as used in the specification regarding the hydrophilic means of an S-type densitometer to obtain a blue filter Colloids applicable, P P y and P Y- sensitivity (Sh), yellow filter sensitivity (Sy) nd f It) mers of these compounds. As for the molecular weight The results are shown in Table 3, range of these polymers applicable to the present in vention, it may be generally said that they should be g I within the range of from 1 X to 2 X [0 C omposition ol Dmcmpw Um! As for the cellulose derivatives applicable as hydro- M O c) ml philic colloids, there are carboxy methyl cellulose, car Meml 3 g box eth l cellulose, cellul l I Anhydrous sodium sulliti: ltlll g y y 056 a gmdte and pdrnflu) Hydnmmnmm 5 g hydrolyzed cellulose alginate. The molecular weight Borax 2 g range of the cellulose derivatives should preferably be Water to will) ml within 1 X 104m 2 X pH 4 8.70:1)10! so I Regarding the polyvmylpyrrolidone and copolymers Table 3 Addition Method Corresponding Photographic Test Solvent amount X Characteristics No. Dye mol ll] g-mol Sy Sh Fog l 0 100 (M0 2 IV methanol 5 )l 95 (l. l 3

5 X 10 mol 3 it) Hit) 83 0,13 4 tau 7! 013* 5 100 39 0.13 6 IV Emulsion 4 6.7 100 90 (H0 7 1.3 I ll) 75 (m9 8 2,6 140 57 0.10 9 5.2 9| 32 O.l I

It) lV Emulsion is 6.7 105 90 010 ll 1.3 l25 70 0.09

| 2 26 too 009* Same sample as spectrogram of FIG. ll

Same sample as spectrogram of HG. l2 "'Sarne sample as spectrogram of FIG. I]

The features and advantages of the present invention of same, it is preferred that the polyvinylpyrrolidone will be understood from these results, have a molecular weight range of from I X l0 to l X Although the present invention has been adequately l0. As for the copolymers, polyvinylpyrrolidone may described in the foregoing specification and examples be copolymerized with acrylic amides or vinyl acetate, included therein, it is readily apparent that various 45 the polyvinylpyrrolidone in each being of from O to changes and modifications may be made without deby weight of the acrylic amide. It is also preferred parting from the scope thereof. that the polyvinylpyrrolidone copolymers employed To reiterate. the present invention is directed to a have a molecular weight range of from l X l() to 2 X method for sensitizing spectrally a photograhic sensi- 10 tive emulsion, which comprises dissolving a methine 50 In addition to the water-soluble groups applicable to sensitizing dye containing at least one water-soluble the polymers of the present invention, which have algroup in the organic solvent, having a water solubility ready been enumerated, there are the added groups of of l()% by weight or less at 35 C, dispersing the soluthiosulfonate, thiosulfate, ammonium, amino, cyano, tion in a member selected from the group consisting of hydroxyl, ureido, ethyleneoxide, and the like. These water and a hydrophilic colloid of 2% by weight or less, water-soluble groups are applicable equally as well to and subsequently to the dispersing step, adding the disthe methine sensitizing dye employed herein. persion to a light'sensitive emulsion. What is claimed is:

The term high vapor pressure" as pertaining to the l. A method for sensitizing spectrally, a photographic organic solvent applicable to the present invention is light SeflSillVe Emulsionv mprising l fll' h li disdirected to an organic solvent which is preferably vola- Pfi 1n a hydrophilic Il l mPIl lItg tile at room temperature and more preferably, an orat l ing a ll lne dye C ntaining at least one ganic solvent having a vapor pressure of more than 50 Water-Soluble g p an "g Solvent having 8 mm hg at 20 C so that the solvent can be readily re ater Solubility of 10% by weight or lSS E l 5 moved from the emulsion layer in the course of the dry' p r ing {he SOlUUOTl a member E Clfi fr m ing process after coating the emulsion onto the support.

As to the organic solvents applicable to the present :nvention, other than those already enumerated, refer ence is made to KirkOthmer, Encyclopedia of Technology, Vol. 12. pages 654-686.

the group consisting of water and a hydrophilic col loid of 2% by weight or less, and c. subsequently to the dispersing step, adding the dispersion to the light-sensitive silver halide emulsion. 2. The method of Claim 1, wherein said water-soluble group is a member selected from the group consisting of a carboxyl group, a sulfo group, a sulfate group and a phosphate group.

3. The method of claim 1, wherein said methine dye substituted alkyl group of from 1 to 5 carbon atoms as the N-substitute thereof.

4. The method of claim 1, wherein the methine dye is a member selected from the group consisting of:

O C H comprises a cyanine nucleus having a sulfo-containing CH CH OCH CH COOH Br and 5. The method of claim 1, wherein at least two methine dyes are used in a supersensitizing combination.

6. The method of claim 1, wherein said organic solvent is a material containing a hydrophilic group and a hydrophobic aromatic or aliphatic radical.

7. The method of claim 6, wherein said hydrophilic group is a member selected from the group consisting of a hydroxyl group, an ester group and a keto group.

8. The method of claim 1, wherein the organic solvent is a member selected from the group consisting of methyl-phenylcarbinol, Z-pentanol, diisobutylcarbinol, mesity] oxide, methyl isobutyl ketone. isopropyl acetate, cellosolve acetate and Z-phenoxyethanol.

9. The method of claim 1, wherein said hydrophilic colloid is a member selected from the group consisting of gelatin, polyvinylpyrrolidone polymer, copolymers of polyvinylpyrrolidone, cellulose derivative, alginate polymer, polyvinyl alcohol, polyacrylic acid polymer, maleic anhydride polymer, and polyvinylbenzenesulfonate polymer.

10. The method of claim 9, wherein the polymer contains a member selected from the group consisting of a sulfo group, a carboxyl group, a thiosulfonate group, a thiosulfate group, an ammonium group, an amino group, a cyano group, a hydroxyl group, a ureido group, and an ethylene oxide group.

11. The method of claim 9, wherein the cellulose derivative is a member selected from the group consisting of carboxymethyl cellulose, carboxyethyl cellulose, cellulose alginate, and partially hydrolyzed cellulose acetate.

12. The method of claim 9, wherein the polyvinylpyrrolidone copolymer is a copolymer of polyvinylpyrrolidone with a member selected from the group consisting of acrylic amide and vinyl acetate.

13. The method of claim 9, wherein the molecular weight range of the polymers employed ranges from l X 10 to 2 X10 14. The method of claim 9, wherein the molecular weight of the cellulose derivatives employed ranges from 1 X to 2 X 10".

15. The method of claim 9, wherein the molecular weight of the polyvinylpyrrolidone polymer ranges from 1 X l0 to l X 10 16. The method of claim 9, wherein the molecular weight of the polyvinylpyrrolidone copolymer ranges from 1 X l0" to 2 X 10 17. The method of claim 1, wherein the lightsensitive emulsion is a gelatino silver halide emulsion.

18. The method of claim 1, wherein the amount of a dye present is within the range of from 1 X l0 to l X 10' mol of dye per one mol of the light-sensitive material.

19. A photographic light-sensitive silver halide emulsion spectrally sensitized by the method of claim 1.

20. A photographic light-sensitive silver halide element, which comprises a support having thereon at least a layer containing the emulsion of claim 1.

21. The photographic light-sensitive silver halide element of claim 20, wherein said support is selected from the group consisting of polyethylene terephthalate, baryta paper, paper, resin laminated paper, synthetic paper, glass sheet, plastic film, metallic sheet and cellulose derivative film.

22. The method of claim 1, wherein in step b the solution is dispersed in the water.

23. The method of claim 1, wherein in step b the solution is dispersed in the hydrophilic colloid of 2% by weight or less.

24. The method of claim 1, wherein soluble group is a carboxyl group.

25. The method of claim 1, wherein soluble group is a sulfo group.

26. The method of claim 1, wherein soluble group is a sulfate group.

27. The method of claim 1, wherein soluble group is a phosphate group.

28. The method of claim 1, wherein the dispersing of step b occurs in the presence ofa surface active agent.

said watersaid watersaid watersaid water-

Claims (28)

1. A method for sensitizing spectrally, a photographic light sensitive emulsion, comprising silver halide dispersed in a hydrophilic colloid comprising a. dissolving a methine dye containing at least one water-soluble group in an organic solvent having a water solubility of 10% by weight or less at 35*C, b. dispersing the solution in a member selected from the group consisting of water and a hydrophilic colloid of 2% by weight or less, and c. subsequently to the dispersing step, adding the dispersion to the light-sensitive silver halide emulsion.

1. A METHOD FOR SENSITIZING SPECTRALLY, A PHOTOGRAPHIC LIGHT SENSITIVE EMULSION, COMPRISING SILVER HALIDE DISPERSED INA HYDROPHILIC COLLOID COMPRISING A. DISSOLVING A METHINE DYE CONTAINING AT LEAST ONE WATERSOLUBLE GROUP IN AN ORGANIC SOLVENT HAVING A WATER SOLUBILITY OF 10% BY WEIGHT OR LESS AT 35*C, B. DISPERSING THE SOLUTION IN A MEMBER SELECTED FROM THE GROUP CONSISTING OF WATER AND A HYDROPHILIC COLLOID OF 2% BY WEIGHT OR LESS, AND C. SUBSEQUENTLY TO THE DISPERSING STEP, ADDING THE DISPERSION TO THE LIGHT-SENSITIVE SILVER HALIDE EMULSION.

2. The method of claim 1, wherein said water-soluble group is a member selected from the group consisting of a carboxyl group, a sulfo group, a sulfate group and a phosphate group.

3. The method of claim 1, wherein said methine dye comprises a cyanine nucleus having a sulfo-containing substituted alkyl group of from 1 to 5 carbon atoms as the N-substitute thereof.

4. The method of claim 1, wherein the methine dye is a member selected from the group consisting of:

5. The method of claim 1, wherein at least two methine dyes are used in a supersensitizing combination.

6. The method of claim 1, wherein said organic solvent is a material containing a hydrophilic group and a hydrophobic aromatic or aliphatic radical.

7. The method of claim 6, wherein said hydrophilic group is a member selected from the group consisting of a hydroxyl group, an ester group and a keto group.

8. The method of claim 1, wherein the organic solvent is a member selected from the group consisting of methyl-phenylcarbinol, 2-pentanol, diisobutylcarbinol, mesityl oxide, methyl isobutyl ketone, isopropyl acetate, cellosolve acetate and 2-phenoxyethanol.

9. The method of claim 1, wherein said hydrophilic colloid is a member selected from the group consisting of gelatin, polyvinylpyrrolidone polymer, copolymers of polyvinylpyrrolidone, cellulose derivative, alginate polymer, polyvinyl alcohol, polyacrylic acid polymer, maleic anhydride polymer, and polyvinylbenzenesulfonate polymer.

10. The method of claim 9, wherein the polymer contains a member selected from the group consisting of a sulfo group, a carboxyl group, a thiosulfonate group, a thiosulfate group, an ammonium group, an amino group, a cyano group, a hydroxyl group, a ureido group, and an ethylene oxide group.

11. The method of claim 9, wherein the cellulose derivative is a member selected from the group consisting of carboxymethyl cellulose, carboxyethyl cellulose, cellulose alginate, and partially hydrolyzed cellulose acetate.

12. The method of claim 9, wherein the polyVinylpyrrolidone copolymer is a copolymer of polyvinylpyrrolidone with a member selected from the group consisting of acrylic amide and vinyl acetate.

13. The method of claim 9, wherein the molecular weight range of the polymers employed ranges from 1 X 104 to 2 X 105.

14. The method of claim 9, wherein the molecular weight of the cellulose derivatives employed ranges from 1 X 104 to 2 X 105.

15. The method of claim 9, wherein the molecular weight of the polyvinylpyrrolidone polymer ranges from 1 X 104 to 1 X 106.

16. The method of claim 9, wherein the molecular weight of the polyvinylpyrrolidone copolymer ranges from 1 X 104 to 2 X 105.

17. The method of claim 1, wherein the light-sensitive emulsion is a gelatino silver halide emulsion.

18. The method of claim 1, wherein the amount of a dye present is within the range of from 1 X 10 7 to 1 X 10 3 mol of dye per one mol of the light-sensitive material.

19. A photographic light-sensitive silver halide emulsion spectrally sensitized by the method of claim 1.

20. A photographic light-sensitive silver halide element, which comprises a support having thereon at least a layer containing the emulsion of claim 1.

21. The photographic light-sensitive silver halide element of claim 20, wherein said support is selected from the group consisting of polyethylene terephthalate, baryta paper, paper, resin laminated paper, synthetic paper, glass sheet, plastic film, metallic sheet and cellulose derivative film.

22. The method of claim 1, wherein in step b the solution is dispersed in the water.

23. The method of claim 1, wherein in step b the solution is dispersed in the hydrophilic colloid of 2% by weight or less.

24. The method of claim 1, wherein said water-soluble group is a carboxyl group.

25. The method of claim 1, wherein said water-soluble group is a sulfo group.

26. The method of claim 1, wherein said water-soluble group is a sulfate group.

27. The method of claim 1, wherein said water-soluble group is a phosphate group.

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