US2801170A

US2801170A - Preparation of color former dispersions

Info

Publication number: US2801170A
Application number: US476539A
Authority: US
Inventors: Paul W Vittum; Donald B Julian
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1954-12-20
Filing date: 1954-12-20
Publication date: 1957-07-30
Anticipated expiration: 1974-07-30
Also published as: US2787544A; GB791353A; BE543744A; FR1151479A; DE963295C; GB798512A

Description

y 3 1957 P. w. VITTUM ET AL I 2,801,170

PREPARATION OF COLOR 'FORMER DISPER IONS Filed Dec. 20, 1954 COUPLER 4- LOW BOILING COUPLER SOLVENT I DISPERSION 0F COUPLER LOW BOILING SOLVENT IN $ELAT|N HIGH BOILING CRYSTALLOIDAL COUPLER SOLVENT ms znszn m DRYING sauna DISPERSION 'OF COUPLER IN GELA'I'IN GELATINO' SILVER HALIOE EM ULSION GELATINO'SILVER mun: EMULSION CONTAINING DISPERSION 0F COUPLER m men BOILING CRYSTALLOIDAL COUPLER SOLVENT.

Paul WViitum Donald B. Julian ENTORS' W 7MZ ATTOR NEYJ United States Patento PREPARATION OF COLOR FORMER DISPERSIONS Paul W. Vittum and Donald B. Julian, Rochester, N. Y., assiguors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application December 20, 1954, Serial No. 476,539

4Claims. (Cl. 96-97) This invention relates to color photography and particularly to a method for incorporating couplers in silver halide emulsion layers.

In preparing dispersions of color-forming compounds in silver halide emulsions it is customary to dissolve the color former or coupler in a suitable'high boiling solvent, disperse this solution in aqueous gelatin and mix the resulting dispersion with the sensitive silver halide emulsion before coating. Ratios of coupler to solvent of about 1 to 2 or 1 to 3 are usually employed (see examples of Jelley and Vittum U. S. Patent 2,322,027), although with some couplers a ratio of 1 to 1 can be used successfully. The true solubility of the couplers in the coupler solvents is, however, considerably lower than is indicated by the above ratios and in many cases does not exceed one part of coupler in ten parts of coupler solvent. The dispersed phase inmost color former dispersions incorporated in emulsion layers is, therefore, usually a highly. supersaturated solution.

Even in the coupler-to-solvent ratios usually employed a large amount of inert solvent is introduced into the emulsion and this is disadvantageous because the inert material has no photographic function and because it tends to decrease the physical hardness of the emulsion layer.

In order. to reduce to a minimum the amount of the inert ingredients in the emulsion layer and to improve the physical hardness of the coatings, it would be desirable to use smaller quantities of coupler solvent than those corresponding to the above ratios. To this end, etforts have been made to prepare coupler dispersions using smaller ratios of coupler solvent, representing, for example, ratios of coupler to solventof 1 to A: or 1 to A. Such low ratio dispersions have been successfully prepared in some cases using auxiliary solvents which are removed during the course of preparing. the dispersion. The same technique has been applied to the preparation of coupler dispersions containing substantially no coupler solvent.

With some couplers, recrystallization occurs with these low ratio dispersions. Crystal-free dispersions containing no coupler solvent can be obtained but these dispersions nearly always yield less dye upon color develop ment, unless the developing solution contains an organic solvent such as benzyl alcohol and hence, have only a limited usefulness where normal color processing is required.

We have now found that it is possible to prepare dispersions of color-forming couplers in gelatin emulsions, the dispersions having a low ratio of coupler to coupler solvent and showing a minimum of coupler crystallization. Our method consists in making two separate dispersions:

- (1) a solvent-free dispersion of the coupler, and (2) a dispersion of the high boiling coupler solvent alone. The two dispersions are then added in proper proportions to a gelatino-silver halide emulsion and mixed prior to coating.

The accompanying drawing is a flow sheet illustrating the stepsin our process.

When proceeding in this way we believe that a rapid interaction occurs between the two dispersions on mixing sothat, in efi'e'cL-the new method provides a means of avoiding the necessity for maintaining the supersaturation of the coupler-coupler solvent system throughout the .process of removing the auxiliary solvent in which the coupler is originally dissolved.

Couplers which may beused according to our inventionare disclosed in Jelley and Vittum U. S. Patent 2,322,027, Loria, Weissberger and Vittum U. S. Patent 2,600,788 and elsewhere.

High boiling coupler solvents which are used according to our invention to form the second dispersion mentioned above are organic crystalloidal materials which are substantially water-insoluble, have low molecular weight, have a boiling point'above about C. and have a high solvent action for the color-forming compound and for the dyesv formed from it and are permeable to photographic developer oxidation products in the layer in whichthey are incorporated. Such materials include di-n-butylphthalate and other compounds disclosed on pages 2 and 3 of Ielley and Vittum U. S. Patent 2,322,027.

Low boiling organic solvents in which the color-forming compound is first dissolved and which is removed to form the substantially dry or solvent-free dispersion of coupler'in gelatin prior to mixing the dispersion of coupler with the dispersion of high boiling coupler solvent, include nitromethane, nitroethane, methyl, ethyl, propyl and butyl acetates .and ethyl and butyl formate.

Our process is further illustrated by the flow sheet diagram in the accompanying drawing. As shown therein,.to'a solution of coupler in low-boiling organic coupler solvent there is added a gelatin solution and a dispersion of the coupler and low-boiling solvent formed in the gelatin. This. dispersion is dried to remove the lowboiling solvent, leaving a dispersion of the coupler in gelatin.

A separate dispersion of high-boiling crystalloidalcoupler solvent is made in gelatin and this dispersion and the dried dispersion of the coupler in gelatin are added to a gelatino-silver halide emulsion. Mixing these together results in a gelatino silver halide emulsion containing a dispersion of coupler in high-boiling crystalloidal coupler solvent.

Our invention will now be illustrated by the following examples:

EXAMPLE I A. Preparation of solvent-free coupler dispersion V T-wograms of the coupler 1-(2,4,6'-trichlorophenyl)- 3 [3" -'(2",4" di tent.amylphenoxyacetamido)- benzamido] .-5-pyrazolone and 8 cc. of ethyl acetate were heated until the coupler was completely dissolved. To the coupler solution there was added with stirring a mixture of 70.8 cc. of 10% gelatin solution and 8 cc. of a 5% solution of Alkanol B. The mixture was passed through a colloid mill 4 times and then chilled to 40 F. to gel. The gel dispersion was then shredded, spread out on a stainless steel screen and dried at 72 F. and 50% relative humidity.

B. Preparation of high boiling coupler solvent dispersion 'I hree cc. of di-n-butylphthalate were added with stirring to a warm mixture of 35.5 cc. of 10% gelatin solution and 4 cc. of a 5% oslution of Alkanol B. The mixture was passed through a colloid mill 4 times and filtered through a. silk screen to remove air bubbles.

C. Preparation of coating mixture 1.9 grams of the dried coupler dispersion A was added to a mixture of 25.2 cc. of water and 1.2 cc. of saponin solution. The mixture was allowed to soak for about 20 minutes and then the mixture was heated in a water bath at 40 C. 2.8 cc. of the coupler solvent dispersion B were then added and the mixture of the two dispersions was finally added to cc. of a gelatino-silver halide'emulsion.

The final emulsion was coated and dried in the usual way and upon exposure and development in the following solution was found to produce a satisfactory magenta dye density. t

I Grams p-Aminodiethylphenylenediaminesulfate 2 Sodium sulfite, anhydrous 5 Sodium carbonate, anhydrous Potassium bromide 2 Water to 1 liter.

Other primary aromatic amino developing agents may, of course, be used. EXAMPLE II A. Preparation of a solvent-free coupler dispersion Two grams of the coupler 2-[u-diamylphenoxybutyrylamino]-4,6-dichloro-5-methylphenol was dissolved in 8.0 ml. of ethyl acetate. To this solution were added 8.0 cc. of Alkanol B (5%) and 70.8 cc. of 10% gelatin solution. A dispersion was then made by passing this mixture through a colloid mill 4 times. After the dispersion had gelled, it was shredded and washed in water (40 F.) for 24 hours to remove the ethyl acetate. It was dried by spreading the shredded material on stainless steel screens.

B. Preparation of coupler solvent dispersion Three cc. of tri-o-cresyl phosphate and 6.0 cc. of ethyl acetate were warmed and added to a solution of 35.4 cc. of 10% gelatin solution and 4.0 cc. of Alkanol B (5%). This mixture was passed through a colloid mill 4 times. The ethyl acetate was removed by shredding the dispersion and washing in water at 40 F. for 24 hours. The dispersion was then dried on stainless steel screens at room temperature. 3.27 grams of this dispersion was added to 19.2 cc. of water and 2.0 cc. of Alkanol B (5%). This mixture was allowed to stand 20 minutes, at which tim it was warmed to 40 C. i

C. Preparation of the coating mixture EXAMPLE III A. Preparation of a solvent-free coupler dispersion Two grams of N(4-benzoylacetaminobenzenesulfonyl)- N-(' -phenylpropyl)-p-toluidine was dissolved in 8.000. of methylisobutylcarbinol. 8.0 cc. of Alkanol B (5%) 4 and 70.8 cc. of 10% gelatin solution were added to this solution. This mixture was then passed through a colloid mill four times. The resulting dispersion was chilled, shredded and washed with water to remove the coupler solvent.

B. Preparation of the coupler solvent dispersion A solution of 35.4 cc. of 10% gelatin solution and 4.0 cc. of Alkanol B (5%) was added with stirring to 3.0 cc. of ethyl sebacate. A dispersion was then made by passing this mixture through a colloid mill four times.

C. Preparation of the coating mixture 1.9 grams of the dried coupler dispersion A was soaked in a solution of 23.0 cc. of Water, 2.0 cc. of Alkanol B (5% and 1.2 cc. of saponin (5%) for about 20 minutes. This mixture was then warmed to 40 C. at which time 2.8 cc. of the coupler solvent dispersion B and 10.0 cc. of a silver halide emulsion were added.

The final emulsion was coated, dried, exposed and developed as in Example I and was found to produce a satisfactory yellow dye density.

It will be understood that our invention is to be taken as limited only by the scope of the appended claims.

We claim:

1. The method of incorporating a color former in a gelatino-silver halide emulsion which comprises mixing a color-forming compound capable of reacting with a primary aromatic amino developing agent on photographic development, with a low boiling water-insoluble organic solvent for the color-forming compound said low-boiling solvent having a boiling point below C., dispersing the solution of color-forming compound and low boiling organic solvent in gelatin, drying said dispersion to remove substantially all organic solvent, separately dispersing in gelatin a substantially water-insoluble, 'low molecular weight, organic crystalloidal-material having a boiling point above about C., said organic crystalloidal material having a high solvent action for the color-forming compound and for dyes formed therefrom, and being permeable to photographic developer oxidation products, and then mixing said dispersion of color-forming compound and said dispersion of organic crystalloidal material, with a gelatino-silver halide emulsion to form a dispersion in the emulsion of liquid particles of'the colorforming compound and the organic crystalloidal material.

2. The method of claim.1 in which the low boiling organic solvent is ethyl acetate.

3. The method of claim 1 in which the organic crystalloidal material is di-n-butylphthalate.

4. The method of claim l in which the low boiling organic solvent is ethyl acetate and the organic crystalloidal material is di-n-butylphthalate.

References Cited in the file of this patent UNITED STATES PATENTS Jelley et a1. June 15, 1943 Jelley etal Aug. 9, 1949

Claims

1. THE METHOD OF INCORPORATING A COLOR FORMER IN A GELATINO-SILVER HALIDE EMULSION WHICH COMPRISES MIXING A COLOR-FORMING COMPOUND CAPABLE OF REACTING WITH A PRIMARY AROMATIC AMINO DEVELOPING AGENT ON PHOTOGRAPHIC DEVELOPMENT, WITH A LOW BOILING WATER-INSOLUBLE ORGANIC SOLVENT FOR THE COLOR-FORMING COMPOUND SAID LOW-BOILING SOLVENT HAVING A BOILING POINT BELOW 125* C., DISPERSING THE SOLUTION OF COLOR-FORMING COMPOUND AND LOW BOILING ORGANIC SOLVENT IN GELATIN, DRYING SAID DISPERSION TO REMOVE SUBSTANTIALLY ALL ORGANIC SOLVENT, SEPARATELY DISPERSING IN GELATIN A SUBSTANTIALLY WATER-INSOLUBLE, LOW MOLECULAR WEIGHT, ORGANIC CRYSTALLOIDAL MATERIAL HAVING A BOILING POINT ABOVE 175* C., SAID ORGANIC CRYSTALLOIDAL MATERIAL HAVING A HIGH SOLVENT ACTION FOR THE COLOR-FORMING COMPOUND AND FOR DYES FORMED THEREFROM, AND BEING PERMEABLE TO PHOTOGRAPHIC DEVELOPER OXIDATION PRODUCTS, AND THEN MIXING SAID DISPERSION OF COLOR-FORMING COMPOUND AND SAID DISPERSION OF ORGANIC CRYSTALLOIDAL MATERAIL, WITH A GELATINO-SILVER HALIDE EMULSION TO FORM A DISPERSION IN THE EMULSION OF LIQUID PARTICLES OF THE COLORFORMING COMPOUND AND THE ORGANIC CRYSTALLOIDAL MATERIAL.