US3180734A - Light sensitive photographic color element - Google Patents

Description

April 27, 1965 J. F. WILLEMS ETAL 3,180,734

LIGHT SENSITIVE PHOTOGRAPHIC COLOR ELEMENT Filed Nov. 7. 1960 Wlllllllllll/MIIA Meg/afer n INVENTORS BYM, wei-v ATTORNEYS United States Patent O 3,180,734 LIGHT SENSITIVE PHOTOGRAPHS CGLOR ELEMENT Jozef Frans Willems and Willem Karel Koerber, both of Wilrijk-Antwerp, Belgium, assignors to Gevaert Photo- Producten NN., Mortsel, Belgium, a Belgian company Filed Nov. 7, 1960, Ser. No. 67,483 Claims priority, application Belgium, Nov. 5, 1959, 39,339, Patent 584,331 4 Claims. (Cl. 96--74) This invention relates to a process for improving the color reproduction of a color photographic material.

When preparing photographic color images by color development of exposed silver halide layers, a silver salt image and a color image are formed, the latter being formed by the reaction of the oxidation productsV of the color developing substances such as the usual p-dialkyl phenylene diamines with a color coupler present in said silver halide layer to form a dye.

In the color development of a color photographic material which is composed of different layers, and which comprises three silver halide layers respectively sensitized for the blue, green and red regions of the spectrum, and which also contain a color coupler forming, respectively, a yellow, a magenta and a cyan dye with the oxidation products of the developer, it is oi' paramount irnportance that the oxidation products of the developer, which are formed in a delined layer by the reduction of the exposed silver halide in said layer, couples in situ with the color coupler present therein.

Although in most cases the greater part of the formed oxidation products couples in situ, a rather important part of these products diffuses to an adjacent layer to couple with another color coupler present therein resulting into an undesirable color whereby a bad color reproduction is obtained.

The same phenomenon appears in a photographic material which is suitable for the manufacture of color images wherein for instance three silver halide emulsions in a water-soluble binding agent, one of which is red-sensitized, one green-sensitized and one blue-sensitized, which for instance contain all three a color coupler and which form With the oxidizing products of the developer respectively a cyan-, a magentaand a yellow dyestufi, are dispersed in a solution of a water-insoluble but waterpermeable full-synthetic macromolecular compound whereafter the dispersion thus obtained is applied to a suitable support. The preparation of such photographic material suitablevfor thev preparation of color image is described in the Belgian patent specification 536,673.

A variant of this process consists in preparing a dispersion of silver halide grains in an aqueous solution of a hydrophilic binding agent, to emulsify this dispersion in a solution of -a hydrophobic binding agent in an organic solvent which is not miscible with water, and to emulsify thereafter the emulsion thus obtained in anaqueous solution of a hydrophilic layer-forming binding agent. This method is described in the Belgian patent speciiication 551,312.

Still other -variants are:

A photographic emulsion prepared in a water-insoluble but water-permeable binding agent is dispersed in a water-soluble binding agent, e.g. gelatin or polyvinyl alcohol (US. patent specifications 2,490,749 and 2,548,526).

A dispersion of a modiiied (in situ selectively hardened or insolubilised by cross-linking) originally in watersoluble photographic emulsion (among others gelatin in a water-soluble binding agent) (US. patent specilication 2,698,794). K

A dispersion of a photographic emulsion, prepared in a suitable water-soluble binding agent, in a water-soluble lflgd Patented Apr. 2?, i965 ICC binding agent which is not compatible with the first (eg.

gelatin and polyvinyl alcohol) (British patent specification 800,444).

A dispersion of silver halide gelatin emulsion in cellulose-ether (outer phase) (Belgian patent specifications 520,567 and 542,381).

In the processing of such photographic elements for obtaining color images, it is likewise of great importance that the oxidation products formed by reduction of the exposed silver halide, couple on that area where they are formed and do not dilluse away to an emulsion droplet with other properties to form therein an undesirable color.

It is already known that some products belonging to the type of the cyclic compounds containing OH groups (US. patent specifications 2,360,290 and 2,401,713) comprising especially the hydroquinone derivatives (Belgian patent specification 447,239, U.S. patent specification 2,336,327, Belgian patent specilication 453,723, U.S. patent Specifications 2,403,721, 2,675,314, 2,701,197, 2,704, f

713, 2,710,801, 2,735,765, 2,728,659, 2,732,300), ascorbic acid derivatives (U.S. patent speciiications 2,336,327 and 2,768,661) and further hydragine compounds (German patent DBP 984,810) are capable of reacting with the oxidation products of the color developer.

These reducing agents possess the property of oxidizing more easily than the color developing substance itself and, moreover, of not coupling with the color couplers on color development. When using these compounds in the color photographic emulsions it is possible to eliminate the general color fog formation which may arise during the color development (c g. by aerial oxidation of the color developer or by oxidation of the color developer by the colloidal silver of the yellow filter layer, if present).

However, when these compounds are present in the emulsion layers they affect the dye formation between the formed oxidation products of the color developer and the color coupler present since a competition arises between the dye formation on the one hand and the reduction of the formed oxidation products on the other hand. Moreover, while the cyclic compounds containing OH groups are quite capable of reducing the diffusing oxidation products of the color developer, they form colored oxidation products whereby the fog of the iinished color images is increased in too high an extent.

By making these compounds fast to dillusion and incorporating them into a thin layer between two differently sensitized silver halide layers or emulsion droplets, it is in principle possible to obtain a better color reproduction since they react with the diffusing oxidizing products to colorless compounds and in this way prevent the formation of an undesirable color in another layer, or another emulsion droplet, as the case may be. Application of this technique, however, has still the disadvantage that the color fog is strongly increased.

Furthermore the reduction power of the ascorbic acid derivatives and of the hydrazine compounds is insufficient so that the color reproduction is not satisfactorily irnproved when such compounds are used. It is also known that ascorbic acid and its derivatives decompose very rapidly and that their practical utility is but very limited.

Another technique for improving the color reproduction of color photographic images has been described in the Belgian patent specification 560,907. According to this patent, compounds are used which are capable of forming colorless coupling products with the oxidation products of the color developer. For this purpose, cornpounds are considered having the structure of the usual ketone-methylene color couplers for yellow and for rnagenta, one hydrogen atom of the active methylene group of which having been replaced by an alkyl-, a cycloalkyl, an arylor an aralkyl group. These compounds form colorless products with the oxidation products of the color developer.

According to said technique color photographic images with an improved color reproduction can be produced. During storage, however, these tinished color images soon discolor which is probably due to the decomposition of the rst formed leuco-derivative in the colored products. This discoloring is particularly well noticeable at increased temperatures such as c g, on high-glossing the tinished images.

Now we have surprisingly found that a considerably improved color reproduction can be obtained without the above-mentioned disadvantages by adding to the layers present between two differently sensitized silver halide layers or to the phase present between the different silver halide emulsion droplets, compounds which correspond to one of the following general formulae R1 represents a member selected from the group consisting of an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an aralkyl group and a substituted aralkyl group;

R2 represents a member selected from the group consisting of a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an aralkyl group and a substituted aralkyl group;

R3 represents a member selected from the group consisting of a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an aralkyl group, a substituted aralkyl group, a hydroxyl group, an alkoxy group, an aryloxy group, an amino group, an alkylamino group, a hydrazino group and a substituted hydrazinno group;

R4 represents a member selected from the group consisting of an oxygen atom and an oxime group;

X represents a member selected from the group consisting of a hydrogen atom and an acyl radical;

at least two of the radicals R1, R2 and R3 containing a group making said compounds fast to diffusion.

Examples of compounds which correspond to the general formulae of this invention are among others: alphahydroxy (or alphaaryloxy)-acyl acetic acid esters II O OH O OCOR and the products which are formed by saponication or both by saponiiication and dicarboxylation, as well as the conversion products of these compounds, with amines, hydrazines, hydrazides and sulphonyl hydrazides.

Hereinafter follow some examples of preparation.

PREPARATION 1 CxsHsi-C O-CH-C O 03H5 O C O C H3 37.5 g. of palmitoyl acetic acid ethyl ester are dissolved in 100 cm.3 of acetic acid distilled over potassium permanganate. Whilst thoroughly stirring, 74 g. of lead tetracetate are slowly added. Thereafter the temperature is increased to 80 C. and stirring is continued for another 1 hour until the reaction mixture has cornpletely discolored. The whole is poured out into 250 cm.3 of water, the precipitate formed is filtered of and washed with water. The precipitate is dissolved in ether and the insoluble residue is ltered off. The ether is distilled oit and the residue obtained is recrystallized from methanol. Melting point: at about 24 C.

PREPARATION 2 C15H31--CO--CH2--OH PREPARATION 3 8 g. of the product obtained according to Preparation 1, and 2.55 g. of mono-ethanolamine are heatedfor 6 h. in a flask, cooled ott and recrystallizedfrom methanol. Melting point: 50 C.

This product can be prepared according to the description given in J. Chem. Soc. 1942, page 205.

This compound can be prepared by treating 2 mol of caprylic acid ester with a sodium dispersion according to I. Am. Chem. Soc., 57 (1935), page 2302.

The compounds according to the general Formulae I and IL dissolved in a suitable solvent are mixed with a solution of gelatin or of another binding agent Wherefrom the intermediate layers mentioned hereinbefore are prepared. In case these compounds are used in a material which is composed of dispersed differently sensitized emulsion droplets such as for instance described in and known from the Belgian patent specifications 536,673 and 551,312, these compounds can be added to the intermediate discontinuous phases as well as to the outer continuous phases. In case the inner discontinuous phase consists of two color sensitive emulsions and the hydrophilic outer continuous phase contains the non-sensitized emulsion and a color coupler for yellow, it is necessary to add these compounds to the hydrophobic intermediate discontinuous phase.

The amount is chosen lin such a way that the content of active compound lays between about 0.025 g. and 2 g. per sq m. of intermediate layer which corresponds with a concentration of 0.100 g. to 20 g. per litre of :intermediate layer solution. This concentration is not critical and can if necessary be shifted up to higher limits.

In case the compounds are poorly miscible with the aqueous colloid layers with which. they are mixed before casting, the compounds can be dispersed therein by means of a suitable emulsifying agent. Very suitable emulsifying agents are among other sodium salts of alkyl benzene sulphonic acids having surface-active properties.

It is of common practice to apply in the color threelayer material, a yellow filter layer between the bluesensitive layer and the green-sensitive layer in order to eliminate the sensitivity to blue of the emulsion layers sensitive respectively to green and to red.. Such a yellow iilter layer is usually composed of colloidal silver. In this case the compounds according to the present invention can advantageously be used in the yellow lter layer since the colloidal silver exercises an oxidizing effect on the usual color developers whereby these oxidation products can diffuse to an adjacent emulsion layer to produce an undesirable color. If the compounds according to the present invention are used, these oxidation products are immediately reduced again whereby their noxious f action is excluded.

It is also possible to incorporate these compounds into the silver halide layers themselves containing the color couplers. In that case, however, the concentration of these compounds must be such that no excessive competition arises between the dyestui formation of oxidized developers with the color coupler on the one hand and the reduction of the oxidation products on the other hand.

FIG. 1 is a diagrammatic illustration of an otherwise conventional three-layer color material in which one of the novel reducing agents of this invention is incorporated in the yellow filter layer separating the blue-sensitive and green-sensitive layers and in an interlayer separating the green-sensitive and red-sensitive layers. FIG. 2 is a similar illustration of an alternative embodiment in which the several emulsions are dispersed in a common colloid layer which contains the reducing agent of the invention.

In emulsions which on account of determined causes show an excessive gradation, these compounds can simultaneously be used for regulating this gradation.

The following examples illustrate the invention without limiting, however, the scope thereof.

Example 1 A photographic color material which is composed of respectively a suitable support, a red-sensitized silver halide layer containing a colorcoupler for cyan, an intermediate layer consisting of Compound according to Prep. 1 2 g.

dissolved in 40 cm.3 of Dodecylbenzene sulfonic acid 0.5 g. ethanol.

Gelatin 24 g. Water l l.

Grams p-Diethylamino-aniline sulfate 3 Sodium sulte (anhydrous) 2 Sodium carbonate (anhydrous) 60 Potassium bromide 1.5

Water to 1000 cm.

The further finishing process is executed in the commonly known baths. in this -way a color image is obtained showing a much better color reproduction than the color reproduction of a .color photographic material, simillarly composed and finished but comprising intenlayers which were coatedfrom a pure gelatin solution. This improved color reproduction can e.g. be measured in the following way: a green selection of the three-layer material to be tested is made. Next, the H and D-curve of this green-selection is measured behind greenand rediilter in the Ansco-densitometer, and that step of the curves is selected the density of which behind the red filter is nearest to 0.50; the density x behind green filter is measured on the same step. Then is calculated which percentlage of the unknown density Arepresents the density of 0.50; the lower this percentage the better the color reproduction. Thus, a side-absorption of 37% is noted for color material composed according to the foregoing example and wherein the interlayers are cast only from a pure gelatin-solution whereas an improved side-absorption of 27% is noted for a material provided with interlayers whereto the compound 1 has been added.

Example 2 The same photographic color material and processing as in Example l, but instead of 2 g. of the compound according to Preparation 1, 1.5 g. of the compound according to Preparation 2 are added to the gelatin intermediate layers. The improved color reproduction obtained is expressed by a considerably improved measured side-absorption of 23.7% as against 37% of a same material without this compound in the intermediate layers.

Example 5' The same photographic color material and processing as in Example 1, but instead of 2 g. of the co-mpound according to Preparation l, 2 g. of the compound according to Preparation 3 are added to the gelatin intermediate layers and to the yellow filter layer. The improved color reproduction obtained is expressed by a considerably improved measuredside-absorption of 26% as against 37% of a same material without this compound in the intermediate layers.

Example 4 A same photographic color material and processing as in Example l, 'but instead of 2 g. of the compound according to Preparation 1, 1 g. of the compound according to Preparation 4 is added to the gelatin intermediate layer and to the yelow filter layer. The improved color reproduction obtained is expressed by a considerably improved measured side-absorrption of 25% as against 37% of a same material without this compound in the intermediate layers.

Example 5 50 cm.3 of a red-sensitized silver chloride emulsion with normal gradation, containing a color coupler for cyan, are mixed with 0.6 cm.3 of 10% aqueous solution of a polystyrene maleic anhydride composed of equimolecular amounts of both monomers. 5 g. of the butyraldehyde polyvinyl acetal known as Pioloform DS (registered trademark) .are dissolved in 25 cm.3 of chloroform, 25 cm.3 of amyl alcohol and 45 cm.3 of carbon tetrachloride. The photographic emulsion is emulsitied in the polyvinyl acetal solution with a colloid mill or a homogenizer. In the same way, a green-sensitized silver chloride emulsion containing a color coupler for magenta is prepared and a blue-sensitive photographic emulsion containing a color coupler for yellow are prepared. Next, each of the emulsions thus obtained is again separately emulsiiied in 150 cm.3 of a 6% aqueous gelatin solution containing l g. of the compound according to Preparation 1 dissolved in 20 em of ethanol. Then these three complex emulsions are mixed and coated onto a paper support. After exposure, color development as in Example l and lrther finishing, the three different colors are formed in the three different inner phases. The color reproduction and the color separation are much better than in a material which is composed in quite the same way but wherein no compound was added to the gelatin phase.

Example 6 The same emulsion preparation and the same finishing as in Example 5 but 2 g. of the compound according to Preparation l are added per each 100 cm.3 of solvent to the hydrophobic phases consisting of butyraldehyde polyvinyl acetal. The outer gelatin phase consists of pure gelatin. The color reproduction and the color separation are much better than when these compounds are not added.

We claim:

1. A photographic color lm comprising a plurality of silver halide emulsions, each of said emulsions being sensitive to a different portion of the spectrum and containing a color coupler capable of coupling with the oxidation product of an aromatic amino color developing agent, and a separate colloid phase containing a reducing agent selected from the group consisting of a compound of the formula BiC-(IJH-Rz its enolic tautomer, and mixtures thereof, wherein an alkyl radical, a carboxy alkylene radical, a lower alkoxy carbonyl radical, and a lower hydroxy alkyl amino carbonyl radical, and

X is selected from the group consisting of hydrogen and a lower aliphatic carboxylic acyl radical.

2. A multilayer photographic color iilrn comprising a plurality of superposed silver halide emulsion layers, each of said emulsions being sensitive to a different portion of the spectrum and containing a color coupler capable of coupling with the oxidation product of an aromatic amino color developing agent, and an intermediate colloid layer containing a reducing agent selected from the group consisting of a compound of the formula rality of aqueous colloid silver halide emulsions, each ofl said emulsions being sensitive to a dilerent portion of the spectrum and containing a color coupler capable of coupling with the oxidation product of an aromatic amino color developing agent, as the phase surrounding the discontinuous inner phase a hydrophobic colloid and as the continuous outer phase a gelatin layer containing a reducing agent selected from the group consisting of a cornpound of the formula Rx-CH-Rz o X its enolic tautomer, and mixtures thereof, wherein R1 is a long chain alkyl radical,

R2 is selectedfrom the group consisting of hydrogen, an alkyl radical, a carboxy alkylene radical, a lower alkoxy carbonyl radical, and a lower hydroxy alkyl amino carbonyl radical, and

X is selected from the group consisting of hydrogen and a lower aliphatic carboxylic acyl radical.

4. A photographic color iilm comprising a colloid layer which contains as the discontinuous inner phase a plurality of aqueous colloid silver halide emulsions, each of said emulsions being sensitive to a dilierent portion of the spectrum and containing a color coupler capable of coupling with the oxidation product of an aromatic amino color developing agent, as the phase surrounding the discontinuous inner phase a hydrophobic colloid containing a reducing agent selected from the group consisting of a compound of the formula Rio-'on-Rz o 0X its enolic tautomer, and mixtures thereof, wherein R1 is a long chain alkyl radical,

R2 is selected from the group consisting of hydrogen, an alkyl radical, a carboxy alkylene radical, a lower alkoxy carbonyl radical, andra lower hydroxy alkyl amino carbonyl radical, and

X is selectedfrom the group` consisting of hydrogen and a lower aliphatic carboxylic acyl radical.

References Cited by the Examiner UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner. HAROLD N. BURSTETN, Examiner.

Claims (1)

1. A PHOTOGRAPHIC COLOR FILM COMPRISING A PLURALTIY OF SILVER HALIDE EMULSIONS, EACH OF SAID EMULSIONS BEING SENSITIVE TO A DIFFERENT PORTION OF THE SPECTRUM AND CONTAINING A COLOR COUPLER CAPABLE OF COUPLING WITH THE OXIDATION PRODUCT OF AN AROMATIC AMINO COLOR DEVELOPING AGENT, AND A SEPARATE COLLOID PHASE CONTAINING A REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF A COMPOUND OF THE FORMULA R1-CO-CH(-O-X)-R2 ITS ENOLIC TAUTOMER, AND MIXTURES THEREOF, WHEREIN R1 IS A LONG CHAIN ALKYL RADICAL, R2 IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, AN ALKYL RADICAL, A CARBOXY ALKYLENE RADICAL, A LOWER ALKOXY CARBONYL RADICAL, AND A LOWER HYDROXY ALKYL AMINO CARBONYL RADICAL, AND X IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND A LOWER ALIPHATIC CARBOXYLIC ACYL RADICAL.

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