This invention relates to photographic silver halide materials containing a stabiliser compound and particularly to colour photographic materials.

US Patent 3 591 381 describes the use of 6-chromanols as stabilisers for azo dyes, reducing fade caused by light, moisture and heat. US patent A 155 765 describes O-substituted 6—chromanols used as photographic dye image stabilisers. US patent 3 574 627 describes photographic dye image stabilisers which are A-chromanols having 2,2— entamethylene and 2,2-tetramethylene rings. The present invention employs related compounds, the 5-, 7— and 8—chromanols as stabilisers in photographic materials in which the image dyes, as is well known, are azomethine dyes. It has been found that not all chromanol-coupler combinations have the same properties, for example 6—chromanols have a deleterious effect on image dye stability when used in combination with yellow couplers.

According to the present invention there is provided a colour photographic material comprising a support carrying at least one photographic silver halide emulsion layer having associated therewith a 5-, 7— or 8—chromanol image dye stabiliser.

The preferred chromanols have one of the general formulae:

R^ R ⁵

(1) 5—chromanol

(3) 8—chromanol wherein R is H, alkyl, substituted alkyl

-_- (including arylalkyl, eg benzyl), preferably wherein the alkyl groups have 1—4 carbon g atoms, or -R -COOR,

R is an alkyl, preferably having 1-4 carbon atoms,

2 7 R — R are each, independently, H or an alkyl group, preferably having 1—4 carbon atoms, and

R is an alkylene group, preferably having

3-6 carbon atoms.

In a preferred embodiment, the present photographic materials have incorporated therein a dye— orming colour coupler. Such couplers are well known and are often incorporated in photographic materials as a dispersion in droplets of a coupler solvent.

Examples of chromanol compounds useful in the present invention are listed in the following Table.

The chromanols employed in the present invention may be prepared by reaction of the appropriate dihydric phenol with the appropriate diene, eg 2,5—dimethyl—2,4—hexadiene to form the basic chromanol followed by other reactions, in themselves known, to introduce a further substituents. Such processes are illustrated in Examples below.

The chromanols are used in an amount sufficient to stabilize the photographic image dyes and their precursors e.g. in an amount from 0.2 to 2.0 mole per mole coupler, more preferably at approximately equimolar amounts.

The chromanol may be incorporated in the silver halide emulsion layer or a layer adjacent thereto. It can be incorporated as a separate dispersion, but is preferably incorporated in admixture with the coupler. Both coupler and stabilizer may be dissolved in a conventional coupler ^■* * solvent, such as dibutyl phthalate. As in the production of ordinary coupler dispersions, a volatile and/or water—miscible auxiliary solvent, such as ethyl acetate, may be used to aid the dispersion process and then removed by evaporation or by washing the set

- ^* ~ dispersion. Also, the dispersion process can be assisted by the presence of a surface active compound, as usual in the manufacture of coupler dispersions.

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 1978, Item 17643, published by Industrial Opportunities Ltd., The Old Harbourmaster's, 8 North Street, Emsworth, Hants P010 7DD, U.K., the disclosures of which are incorporated on

- ^■ - herein by reference. This publiciation will be identified hereafter as "Research Disclosure". References giving information on couplers and on methods for their dispersions are given in Sections VII and XIV, respectively, of Research Disclosure.

" The couplers which may employed in the present photographic materials are water—insoluble compounds containing ballast groups, phenolic (including naphtholic) couplers being used for producing cyan dyes, acylacetanilides for yellow dyes 0 and pyrazolones for producing magenta dyes. Patents describing couplers for use in the present invention include the following United States Patents:

5

Cyan dye-forming

3 367 531 3 034 892

2 423 730 3 311 476

2 474 293 3 419 390

2 772 826 3 458 315

2 895 826 3 476 563

Magenta Dye forming

2 343 703 3 062 653

2 369 489 3 127 269

2 600 788 3 311 476 2 908 573 3 419 391

2 933 391 3 518 429

Yellow dye-forming 2 298 443 3 277 155 2 407 210 3 408 194 2 875 057 3 415 652

2 908 573 3 447 928

3 265 506 3 933 501

An account of dye— orming development is given in 'Modern Photographic Processing', Vol. 2, Grant Haist, Wiley, New York, 1978, Chapter 9.

The stabilizers are useful in any coupler—incorporated silver halide photographic ,. materials, including monochrome materials, false—colour materials and colour transparency, negative and print materials, to stabilize the image dye obtained on development with a solution including a p_-phenylenediamine colour developing agent. Such developing agents are well—known, being described in,for example Photographic Processing Chemistry, L.F.A. Mason, Focal Press, London, 2nd edition (1975) pp 229—235 and Modern Photographic Processing,, Grant

Haist, Wiley, New York (1979), Volume 2 pp 463-8. They may also be used in colour materials not containing couplers but processed in developer solutions containing couplers.

The silver halide emulsion employed in the elements of this invention can be either ⁵ negative—working or positive-working. Suitable emulsions and their preparation are described in Research Disclosure Sections 1 and II and the publications cited therein. Suitable vehicles for the emulsion layers and other layers of elements of this

¹⁰ invention are described in Research Disclosure Section IX and the publications cited therein.

The photographic elements of this invention or individual layers thereof, can contain brighteners (see Research Disclosure Section V), antifoggants and

- ^• stabilizers (see Research Disclosure Section VI), antistain agents and image dye stabilizer (see Research Disclosure Section VII, paragraphs I and J), light absorbing and scattering materials (see Research Disclosure Section VIII), hardeners (see Research f)

Disclosure Section XI), plasticizers and lubricants (see Research Disclosure Section XII), antistatic agents (see Research Disclosure Section XIII), matting agents (see Research Disclosure Section XVI) and development modifiers (see Research Disclosure Section ⁵ XXI).

The photogaphic elements can be coated on a variety of supports as described in Research Disclosure Section XVII and the references described therein. 0 Photographic elements can be exposed to actinic radiation, typically in the visible region of the spectrum, to form a latent image as described in Research Disclosure Section XVIII and then processed

5

to form a visible dye image as described in Research Disclosure Section XIX. Processing to form a visible dye image includes the step of contacting the element with a colour developing agent to reduce developable silver halide and oxidize the colour developing agent. Oxidized colour developing agent in turn reacts with the coupler to yield a dye.

With negative working silver halide emulsions this processing step leads to a negative image. To obtain a positive (or reversal) image, this step can be preceded by development with a non—chromogenic developing agent to develop exposed silver halide, but not form dye, and then uniform fogging of the element to render unexposed silver halide developable. Alternatively, a direct positive emulsion can be employed to obtain a positive image.

Development is followed by the conventional steps of bleaching, fixing, or bleach—fixing, to remove silver and silver ^" halide, washing and drying.

The following Examples are given for a better understanding of the invention. EXAMPLE 1

Preparation of 2,2—dimethyl—4-isopropy1—7—hydroxy— 3,4-dihydro—benzopyran (6).

Resorcinol (11.Og, 0.1m), petroleum ether (b.p. 60-80°) (2ml) and orthophosphoric acid (5mls) were stirred at room temperature. To the stirred mixture 2,5-dimeth l-2,4-hexadiene (11.Og, 0.1m) was added dropwise (1/2 hr) keeping the temperature of the reaction mixture between 30-35°C. After refluxing the reaction for 8 hrs. it was poured into ice/water, extracted with ethyl acetate, dried and evaporated to dryness. The 7-chromoanol (6) was obtained in 89% yield by column chromatograph . EXAMPLE 2 Preparation of 2.2-dimethyl-4-isopropyl-6-t-butyl-7- hydroxy—3.4—dihydrobenzopyran (7).

OH OH

(6) (7)

To a stirred mixture of the 7—chromanol (6)

(4.38g, 0.2m) and t-butanol (10ml), sulphuric acid

(5ml) was added dropwise keeping the temperature of the reaction mixture between 25-30°C. The reaction mixture was stirred at room temperature for 3 hrs, then poured onto ice/water. The solid was filtered and crystallised from aqueous ethanol to afford the butylated chromanol (7) (4.4g, 85%). EXAMPLE 3

Preparation of 2,2—dimethyl—4-isopropyl—6—t—butyl— 7-benzyloχy-3.4-dihydrobenzopyran (8).

0H OCH ₂ Ph

( 7 ) (8 )

To a stirred mixture of 7—chromanol (7), (5.5g, 0.2m) and potassium carbonate (5gms) in acetone (30ml), benzylbromide (3.42g, 0.2m) was added. The reaction mixture was refluxed with stirring for 18 hrs. The reaction mixture was poured onto ice/water, extracted with ethyl acetate, dried and evaporated to afford a lemon—yellow solid. Crystallisation from aqueous ethanol gave the required product (6.6g, 90%). EXAMPLE 4 Yellow dye light stability improvement

Single layer film strips were prepared by coating a gel-subbed polyethylene-terephthalate support with a photosensitive layer containing a

2 silver bromoiodide emulsion at 0.398 Ag/m , gelatin

2 at 1.36g/m and dispersion of coupler (9) in coupler solvent (10) (1.5 moles/mole of coupler). The coupler

2 coverage was 0.83 millimoles/m . The photographic layer was overcoated with a layer containing gelatin

2 at 3.0g/m and bis—vinylsulphonylmethylether hardener at 1.5 weight percent based on total gelatin. Similar coatings were prepared using coupler dispersions which also contained one of the stabilisers (I) and (V) at 0.5 mole per mole coupler.

Samples were exposed through a graduated density test object and developed with 4—amino-3- methyl-N-ethyl—N-β-(methanesulphonamido)ethyl-aniline in an EP-2 process.

I so '2.

Coupler ( 9 )

OCH ₂ Ph

Coupler Solvent (10)

Patches from each coating having a density at or above 1.0 were faded for 6 weeks using a 5.4 klux xenon source, the UV component of which was removed by a coating of Tinuvin 328 (Trade Mark of Ciba-Geigy) in

2 a gelatin dispersion at a coverage of 750 mg/m on a transparent support. The loss in transmission optical density at the wavelngth of maximum absorption was measured. The data is presented below in Table 2.

TABLE 2

The presence of Stabiliser compounds (I) and (V) greatly improved the fade performance in all cases. EXAMPLE 5 (Comparative)

In a comparative experiment, coatings were prepared as described in Example 4, except that the test materials included in the coupler dispersion were the 6-chromanols (la) and (lb). The results of the fade experiments showed that these 6-chromanols greatly reduced the stability of the yellow image dye as shown in Table 3 below. Compounds la and lb were as follows: OH

( la)

TABLE 3

Coating Initial Final Density Density Density Loss

Coupler (9) 1.05 0.97 -0.08 (7.6%)

Coupler (9) + Compound la 1.09 0.52 -0.57 (52%)

Coupler (9) + Compound lb 1.16 0.85 -0.31 (27%)

EXAMPLE 6

Magenta dye light stability improvement

Typical single layer film strips were prepared by coating, as in Example 4, a gel—subbed polyethylene- terephthalate support with a photosensitive layer containing a silver bromoiodide emulsion at 0.538 Ag/m 2, gelatin at 3.23g/m2 and dispersion of coupler (11) in coupler solvent (10)

(2.8 moles/mole of coupler) and the test material (1.0 mole/mole of coupler). The photographic layer was overcoated with a layer containing gelatin at

2 1.08g/m and bis-vinylsulphonylmethylether hardener at 1.0 weight percent based on total gelatin. In this case the test materials used were stabilisers (II) and

(VII), and a reference coating containing no stabiliser was also prepared.

Samples were exposed and tested as in Example

4 but using a Wratten (Trade Mark) 2B filter instead of the Tinuvin coating.

The results are tabulated below.

Coupler (11) had the formula:

Coupler (11)

TABLE 4

The presence of Stabiliser compounds (II) and (VII) greatly improved the fade performance in all cases.