GB2286689A - Photographic colour emulsions with high dye yield couplers - Google Patents

Abstract

A photosensitive colour-forming emulsion layer including a high dye yield coupler so that development of the photographic element can be carried out using a reduced concentration of developing agent. The concentration of the developing agent may be reduced by up to 75%. The coupler preferably has the formula COUP-L-@-PUG wherein COUP is a coupler moiety, L is a leavable linking group and -@-PUG are a releasable dye so that on reaction with oxidised developer two moles of dye are released. The coupler is preferably added to the fast yellow emulsion layer and may be present in reduced amounts.

Description

PHOTOSENSITIVE COLOUR-FORMING EMULSION LAYER INCLUDING A HIGH DYE YIELD COUPLER FIELD OF THE INVENTION The present invention relates to a photosensitive colour-forming emulsion layer including a high dye yield coupler. The invention also embraces a photographic element including one or more colour-forming emulsion layers in accordance with the invention.

BACKGROUND OF THE INVENTION An image-wise exposed photosensitive colour-forming emulsion layer which typically forms part of a photographic element (e.g. photographic film or photographic paper) is developed by treating the element with a developer solution containing a developing agent. At the time of writing, the industry standard developer is C41 which contains 4.52g/l CD4 developing agent; CD4 agent can combine with reduced coupler moieties in the emulsion layer to form a range of dyes which give rise to visible colour. CD4 agent is a phenylene diamine which, on disposal, contributes to the oxygen demand of the resulting effluent.

At the time of writing, there is a general trend within the public at large to prefer products and processes which are perceived to be "environmentally friendly". Accordingly, in the fields of photographic materials and photo-finishing, there is a general desire to reduce the oxygen demand of developer effluent; this can be done by reducing the amount of the developing agent contained in the developer solution. However, it will be appreciated by one skilled in the art that unless additional measures are taken simply reducing the amount of developing agent in the developer solution will result in impaired development of photographic elements processed through the solution.

High dye yield couplers, as a class of materials are well known in the photographic art. US-A-4840884, for example, discloses a range of couplers for use in colour-forming emulsion layers, which couplers include a dye as a photographically useful group ("PUG"); on reaction with two moles of oxidised developer, each coupler gives rise to two moles of dye - one as a result of the combination of the oxidised developer with the coupler, and the other being the photographically useful group. These couplers are therefore sometimes referred to as "one-equivalent" couplers.

SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a photosensitive colour-forming emulsion layer including a high dye yield coupler to permit improved development of a photograpic element comprising said emulsion layer using a reduced concentration of developing agent.

ADVANTAGEOUS EFFECT OF THE INVENTION The present inventor has discovered that, quite apart from the capacity of one-equivalent couplers to generate more dye per mole of oxidised developer as compared with conventional "two-equivalent" couplers, a photosensitive colour-forming emulsion layer, including a high dye yield coupler, on developing with a reduced concentration of developing agent, exhibits a greater speed, contrast and Dmax as compared with an emulsion layer containing conventionally a two-equivalent coupler. For two colour-forming emulsion layers containing equal molar amounts of respectively a two-equivalent coupler on the one hand and a one-equivalent coupler on the other, one would, of course, expect the emulsion containing the one-equivalent coupler, on treatment with an identical concentration of developing agent, to exhibit a greater contrast and Daax.

However, the present inventor has found surprisingly that where two otherwise identical colour-forming emulsion layers containing equal dye-yielding molar amounts of respectively a two-equivalent coupler and a one-equivalent coupler are developed using identical concentrations of developing agent, the emulsion layer containing the high dye yield coupler exhibits an improved film speed and contrast as compared with the emulsion containing the two-equivalent coupler. More surprisingly, the inventor has also discovered that the improved speed, contrast and Dmax associated with the one-equivalent coupler in an equal dye-yielding molar amount as compared with a conventional two-equivalent coupler is more significant when the developing step is carried out using a reduced concentration of developing agent.

DETAILED DESCRIPTION OF THE INVENTION The present invention therefore comprehends the use, in a photosensitive colour-forming emulsion layer, of a high dye yield coupler to permit improved development of a photographic element including said emulsion layer using a reduced concentration of developing agent. Accordingly, the present invention also embraces a photographic element such, for example, as positive or negative, colour-forming or black and white photographic film or paper comprising one or more colour-forming emulsion layers in accordance with the present invention.

In some embodiments, the emulsion layer may comprise an amount of high dye yield coupler in the range 0.05 to 5 g/m2; typically, the emulsion layer may comprise 0.02-2 g/m2 high dye yield coupler. It will be appreciated that the precise laydown of high dye yield coupler used may depend on whether the emulsion layer is a fast, medium or slow colour forming layer.

Said high dye yield coupler may be any high dye yield coupler which is known to a person skilled in the art.

In some embodiments the high dye yield coupler may be a one-equivalent coupler; any of the one-equivalent couplers disclosed in US-A-4840884 which is incorporated herein by reference may be used in an emulsion layer in accordance with the present invention. Typically the high dye yield coupler may be represented by the general structure:

wherein: COUP is a coupler moiety.

L is a cleavable linking group.

PUG is a photographically useful group.

NR is substituted nitrogen atom bonded to PUG that together with NR is a releasable dye.

R may be selected from hydrogen, unsubstituted or substituted alkyl such, for example, as alkyl, containing 1 to 30 carbon atoms, cycloalkyl and ary, e.g. unsubstituted or substituted phenyl.

In one embodiment, said high dye yield coupler may be the coupler which has the formula ("Coupler 1"):

The dye constituting the photographically useful group ("PUG") of the high dye yield coupler may be selected from a yellow forming dye, a magenta forming dye and a cyan forming dye. Alternatively, in some embodiments, the photographically useful group may be a dye selected from a blue forming dye, a green forming dye and a red forming dye.

Other high dye yield couplers which may be used in accordance with the present invention are disclosed in United States Patent No. 4248962 and published European Patent Application No. 0173302 which are incorporated herein by reference.

The photographic element in accordance with the present invention may, in some embodiments, comprise a plurality of colour-forming photosensitive emulsion layers in accordance with the invention. Typically, the photographic element may comprise a fast yellow (blue sensitive) emulsion layer comprising a high dye yield coupler having a yellow forming dye as a photographically useful group.

In a different aspect, the present invention comprises a method of photography which comprises exposing a photographic element to actinic light and thereafter developing the element using a developing agent; characterised in that the element includes a photosensitive colour-forming emulsion layer containing a high dye yield coupler, and the developing step is carried out using a reduced concentration of developing agent.

In some embodiments, the amount of developing agent may be reduced by up to 75% by weight. Typically, the concentration of developing agent may be reduced by up to 50%.

In one embodiment, the concentration of developing agent may be about 2.26g/l; in another embodiment, a concentration of developing agent in the amount 1.13g/l may be used.

Said developing agent may be CD4 agent. Typically, C41 developer solution may be used. It will be understood, however, that other developers/developing agents may be used such, for example, as CD3 agent.

In some embodiments, said element may be treated with said developing agent for 3i minutes.

The photographic elements may be single colour elements or a multicolour element. Multicolour elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum.

Each unit may comprise a single emulsion layer or a plurality of emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, may be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum may be disposed as a single segmented layer.

A typical multicolour photographic element comprises a support bearing a cyan dye image-forming unit comprising a red-sensitive silver halide emulsion layer and a cyan dye-forming coupler; a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer and a magenta dye-forming coupler; and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer and a yellow dye-forming coupler. The element may contain additional layers, such for example as filter layers, interlayers, overcoat layers and subbing layers.

In the following discussion of suitable materials for use in the emulsions and elements of this invention, reference will be made to Research Disclosure, December 1989, Item 308119, published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND, which will be identified hereafter by the term "Research Disclosure". The contents of the Research Disclosure, including the patents and publications referenced therein, are incorporated herein by reference, and the Sections herafter referred to are Sections of the Research Disclosure.

The silver halide emulsions employed in the elements of this invention may be negative-working or positive-working. Suitable emulsions and their preparation as well as methods of chemical and spectral sensitization are described in Sections I through IV. Colour materials and development modifiers are described in Sections V and XXI.

Vehicles are described in Section IX, and various additives such as brighteners, antifoggants, stabilizers, light absorbing and scattering materials, hardeners, coating aids, plasticizers, lubricants and matting agents are described for example, in Sections V, VI, VIII, X, XI, XII, and XV1. Manufacturing methods are described in Sections XIII and XVII, processing methods and agents in Sections XIX and XX, and exposure alternatives in Sections XVIII.

Said colour developing agent may be selected from p-phenylenediamines; typically the agent may be selected from:4-amino N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N- (B- (methanesulfonamido) ethyl)aniline sesquisulfate hydrate, 4-amino-3-methyl-N-ethyl-N- (B-hydroxyethyl) aniline sulfate, 4-amino-3-B- (methanesulfonamido) ethyl-N,N- diethylaniline hydrochloride and 4-amino-N-ethyl-N- ( 2-methoxyethyl ) -m-toluidine di-ptoluene sulfonic acid.

With negative working silver halide a negative image may be formed. Optionally a positive (or reversal) image may be formed.

The high dye yield coupler described herein may be used in combination with other Classes of image couplers such as 3-acylamino- and 3-anilino5-pyrazolones and heterocyclic couplers (e.g.

pyrazoloazoles) such for example as those described in EP 285, 274, U.S. Patent 4,540,654 and EP 119,860; and other 5-pyrazolone couplers containing different ballasts or coupling-off groups such for example as those described in U.S. Patent 4,301,235, U.S. Patent 4,853,319 and U.S. Patent 4,351,897. Yellow or cyan coloured couplers (e.g. to adjust levels of interlayer correction) and/or masking couplers such for example as those described in EP 213.490, Japanese Published Application 58-172,647, U.S. Patent 2,983,608, German Application DE 2,706,117C, U.K. Patent 1,530,272, Japanese Application A-113935, U.S. Patent 4,070,191 and German Application DE 2,643,965 may also be used.

Said masking couplers may be shifted or blocked.

Photographically useful coupling-off groups are well-known in the art. Such groups can determine the equivalency of the coupler, i.e., whether it is a 2-equivalent or a 4- equivalent coupler, or modify the reactivity of the coupler. Such groups can advantageously affect the layer in which the coupler is coated, or other layers in the photographic recording material, by performing, after release from the coupler, functions such as dye formation, development acceleration or inhibition, bleach acceleration or inhibition, electron transfer facilitation and color correction.

Representative classes of coupling-off groups include chloro, alkoxy, aryloxy, heteroyloxy, sulfonyloxy, acyloxy, acyl, heterocyclyl, sulonamido, mercaptotetrazole, mercaptopropionic acid, phosphonyloxy anylthio, and arylazo. These coupling-off groups are described in the art, for example, in U.S. Pat. Nos. 2,455,169, 3,227,551, 3,432,521, 3,476,563, 3,617,291, 3,880,661, 4,052,212 and 4,134,766; and in U.K. Patents and published application Nos. 1,466,728, 1,531,927, 1,533,039, 2,006,755A and 2,017,704A, the disclosure of which are incorporated herein by reference.

Thus, the high dye yield couplers may be used in association with materials that accelerate or otherwise modify the processing steps e.g. of bleaching or fixing to improve the quality of the image. Bleach accelerators described in EP 193,389; EO 301,477; U.S. 4,163,669; U.S. 4,865,956; and U.S.

4,923,784 are particularly useful. Also contemplated is use of the coupler in association with nucleating agents, development accelerators or their precursors (UK Patent 2,097,140; U.K. Patent 2,131,188; electron transfer agents (U.S. 4,859,578; U.S. 4,912,025); anti fogging and anti colour-mixing agents such as derivatives of hydroquinones, aminophenols, amines, gallic acid; catechol; ascorbic acid; hydrazides; sulfonamidophenols; and non colour-forming couplers.

Thus the high dye yield couplers may be used in combination with filter dye layers comprising colloidal silver sol or yellow and/or magenta filter dyes, either as oil-in-water dispersions, latex, dispersions or as solid particle dispersions.

Additionally, they may be used with "smearing" couplers (e.g. as described in U.S. 4,366,237; EP 96,570; U.S. 4,420,556; and U.S. 4,543,323). Also, the couplers may in some embodiments be blocked or coated in protected form as described, for example, in Japanese Application 61/258,249 or U.S. 5,019,492.

The high hye yield couplers may further be used in combination with image-modifying compounds such as "Developer- Inhibitor-Releasing" compounds (DIR's); DIR's useful in conjunction with said couplers are known in the art and examples are described in U.S.

Patent Nos. 3,137,578; 3,148,022; 3,148,062; 3,227,554; 3,384,657; 3,379,529; 3,615,506; 3,617,291; 3,620,746; 3,733,201; 4,049,455; 4,049,455; 4,095,984; 4,126,459; 4,149,886; 4,150,228, 4,211,562; 4,248,962; 4,259,437; 4,362,878; 4,409,323; 4,477,563; 4,782,012; 4,962,018; 4,500,634; 4,579,634; 4,579,816; 4,607,004; 4,618,571; 4,678,739; 4,746,600; 4,746,601; 4,791,049; 4,857,447; 4,865,959; 4,880,342; 4,886,736; 4,937,179; 4,946,767; 4,948,716; 4,952,485; 4,956,269; 4,959,299; 4,966,835; 4,985,336 as well as in patent publications GB 1,560,240; GB 2,007,662; GB 2,032,914; GB 2,099,167; DE 2,842,063, DE 2,937,127; DE 3,636,824; DE 3,644,416 as well as the following European Patent Publications: 272,573; 335,319; 336,411; 346,899; 362,870; 365,252; 365,346; 373,382; 376,212; 377,463; 378,236; 384,670; 396,486; 401,612; 401,613.

Such compounds are also disclosed in "Developer Inhibitor-Releasing (DIR) Couplers for Colour Photography," C.R. Barr. J.R. Thirtle and P.W. Vittum in Photographic Science and Engineering, Vol. 13, p.174 (1969), incorporated herein by reference.

Generally, the developer inhibitor-releasing (DIR) couplers may include a coupler moiety and an inhibitor coupling-off moiety (IN). The inhibitor-releasing couplers may be of the time-delayed type (DIAR couplers) which also include a timing moiety or chemical switch which produces a delayed release of inhibitor. Examples of typical inhibitor moieties are: oxazoles, thiazoles, diazoles, triazoles, oxadiazoles, thiadiazoles, oxathiazoles, thiatriazoles, benzotriazoles, tetrazoles, benzimidazoles, indazoles, isoindazoles, mercaptotetrazoles, selenotetrazoles, mercaptobenzothiazoles, selenobenzotiazoles, mercaptobenzoxazoles, selenobenzoxazoles, mercaptobenzimidazoles, selenobenzimidazoles, benzodiazoles, mercaptooxazoles, mercaptothiadiazoles, mercapothiazoles, mercaptotriazoles, mercaptothiazoles, mercaptotriazoles, mercaptooxadiazoles, mercaptodiazoles, mercaptooxathiazoles, telleurotetrazoles or benzisodiazoles.

Following is a description by way of example only and with reference to the accompanying drawings of methods of carrying the present invention in to effect.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings Figure 1 is a graph showing the sensitometric curves constituting the blue records for an emulsion layer containing a high dye yield coupler and an emulsion layer containing a conventional two-equivalent coupler as a comparison.

DETAILED DESCRIPTION OF THE DRAWINGS Example 1 A typical colour negative film was prepared having a fast yellow layer containing a standard two-equivalent yellow image coupler having the formula ("Coupler 2"):

A second colour negative film was prepared in accordance with the invention wherein the fast yellow layer comprised the high dye yield image Coupler 1 in an amount 57% molar with respect to the amount of Coupler 2 in the fast yellow layer of the first mentioned film. Each of the films was given a white light exposure for 1/100 second.

One sample of each film was processed under standard conditions for 3k minutes using a C41 developer solution containing 4.52g/1 CD4 developing agent (standard concentration); one sample of each film was processed identically save that the developer contained 2.26g/1 CD4 (reduced concentration). The sensitometric curves for the samples are shown in Figure 1 of the drawings. The curves for the the film samples processed using 4.52g/1 CD agent are indicated at (1), the curves for the samples processed using 2.26g/1 CD4 are shown at (2); the curves for the samples incorporating high dye yield Coupler 1 are shown in "dashed" lines, the curves for the samples incorporating standard Coupler 2 are shown in "dotted" lines. In Figure 1 the values of Dmin for the curves have been equalised.

Table 1 below shows the speed and contrast for each of the films using the different concentrations of CD4 developing agent.

Table 1: Effects of Coupler 1 on the blue sensitometry of a colour negative film processed in reduced CD4 developer.

Coupler 2 Coupler 1 in FY Process (Comparison - (dashed lines) dotted lines) ER FY ER FY ER FY ER FY Speed Contrast Speed Contrast 4.52gel 366 1.76 371 1.78 CD4 (1) 2.26g/1 336 0.86 346 1.43 CD4 (2) It will be noted from Table 1 and Figure 1 that the film in accordance with the present invention including Coupler 1 in the fast yellow layer exhibits a greater film speed and contrast as compared with ths typical colour negative film at the standard and reduced concentrations of CD4 developing agent, even though the fast yellow layer of the film in accordance with the invention only contains approximately half the laydown density of coupler as compared with the typical film so as to provide a substantially equal dye-yielding molar density of coupler in each film.

Furthermore, at the reduced concentration of CD4 agent, the improved performance of the film in accordance with the invention containing Coupler 1 as compared with the typical colour negative film containing Coupler 2 is significantly better than at the standard level of developing agent. Thus, while both films exhibit an impaired contrast and film speec at the reduced concentration of developing agent, the degree of impairment of the film containing Coupler 1 high dye yield coupler is significantly less than that of the typical film containing Coupler 1.

Claims (19)

1. A photosensitive colour-forming emulsion layer including a high dye yield coupler to permit improved development of a photographic element comprising said emulsion layer using a reduced concentration or developing agent.

2. A photosensitive colour-forming emulsion layer as claimed in claim 1 comprising an amount of high dye yield coupler in the range 0.05-59/m2

3. A photosensitive colour-forming emulsion layer as claimed in claim 1 or claim 2 comprising 0.02-2g/m2 high dye yield coupler.

4. A colour-forming emulsion layer as claimed in claim 1, claim 2 or claim 3 wherein said high dye yield coupler is a one equivalent coupler.

5. A photosensitive colour-forming emulsion layer as claimed in any preceeding claim wherein said high dye yield coupler is a one-equivalent coupler as disclosed in US-A-4840884.

6. A photosensitive colour-forming emulsion layer as claimed in any preceeding claim wherein said high dye yield coupler is represented by the general structure.

wherein: COUP is a coupler moiety.

L is a cleavable linking group.

PUG is a photographically useful group NR is a substituted nitrogen atom bonded to PUG that together with NR is a releasable dye.

7. A photosensitive colour-forming emulsion layer as claimed in any preceeding claim wherein said high dye yield coupler has the formula:

8. A photosensitive colour-forming emulsion layer as claimed in any preceeding claim wherein the dye constituting the photographically useful group ("PUG") of the high dye yield coupler is selected from a yellow forming dye, a magenta forming dye and a cyan forming dye.

9. A photosensitive colour-forming emulsion layer as claimed in any preceeding claim wherein the high dye yield coupler is a high dye yield coupler disclosed in US Patent No. 4248962 or European Patent Application No. 0173302.

10. A photographic element comprising one or more colour-forming emulsion layers as claimed in any preceeding claim.

11. Any photographic element as claimed in claim 10 comprising a fast yellow (blue sensitive) emulsion layer comprising a high dye yield coupler having a yellow forming dye as a photographically useful group.

12. A method of photography which comprises exposing a photographic element to actinic light and thereafter developing the element using a developing agent; charaterised in that the element includes a photosensitive colour-forming emulsion layer as claimed in any of claims 1-9, and the developing step is carried out using a reduced concentration of developing agent as compared with standard concentration for the agent.

13. A method as claimed in claim 12 wherein the amount of developing agent is reduced by up to 75% by weight.

14. A method as claimed in claim 12 or claim 13 wherein the concentration of developing agent is reduced by about 50%.

15. A method as claimed in any of claims 12 to 14 wherein the concentration of developing agent used is about 2.26g/1.

16. A method as claimed in any of claims 12 to 15 wherein the developing agent is CD4 agent.

17. A method as claimed in any of 12 to 15 wherein C41 developer solution is used.

18. A method as claimed in any of claims 12 to 16 wherein the element is treated with said developing agent for 3k minutes.

19. The use, in a photosensitive colour-forming emulsion layer, of a high dye yield coupler to permit improved development of a photographic element including said emulsion layer using a reduced concentration of developing agent.