This is a continuation-in-part of U.S. Patent Application Serial No. 531,827 filed June 1, 1990. Field of the Invention

This invention relates to color photographic materials and in particular to such materials which contain acrylate copolymers. Background of the Invention

Color photographic elements contain a silver halide emulsion dispersed in a binder, such as gelatin, and a dye former. A usual dye former is a dye-forming coupler which typically is dispersed in a high boiling organic solvent, know as a coupler solvent. In almost all color photographic elements, silver halide grains have adsorbed thereto a spectral sensitizing dye which renders the grain sensitive to a desired region of the electromagnetic spectrum. Over the years, the association of synthetic polymers with the various layers of color photographic elements has been suggested for a variety of purposes. Commonly such polymers have been suggested as partial or complete replacements for the gelatin binder in which the silver halide grains, are dispersed. In addition, polymers have been suggested as a means for incorporating the dye-forming coupler in the emulsion layer. In this connection, see Chen U.S. Patent 4,214,047, issued July 22, 1980. Also, various polymers and polymer lattices have been suggested to provide other beneficial properties or performance features for photographic materials. An example of the latter iε Lau et al. U.S. Patent 4,914,005 issued April 3, 1990, which describes the use of polymers latexes containing repeating units derived from

ethoxyalkylyacrylates to reduce the loss of cyan image dye in materials processed in bleach solutions containing.ferric ion complexes.

There exists the need for further improvements in the performance of photographic materials, in particular with respect to one or more of the following:

a) reducing the amount of sensitizing dye remaining in the element after processing, hence reducing the amount of stain due to retained sensitizing dye;

b) increasing the bleachability of silver ion; hence reducing the amount of silver retained in the photographic element after processing; and

c) reducing the increase in minimum density upon keeping of the unprocessed photographic material.

Summary of the Invention

We have found that one or more of these improvements can be obtained by incorporating in a spectrally sensitized silver halide color photographic element a copolymer comprising a) repeating units derived from a methoxy— or ethoxy- containing acrylate or acrylamide monomer copolymerized with b) a different methoxy- or ethoxy-containing acrylate monomer represented by the structure:

wherein

Z is the residue of one or more vinyl monomers, G is -0- or -NH-,

R ^*6 is -H or ^■ CH-, no more than one R" ¹ being x is 15 to 90 weight percent, y iε 0 to 90 weight percent, z is 0 to 85 weight percent, and n is 1 to 20, but if y=0, z must be > 10.

Detailed Description of the Invention

In a preferred embodiment of this invention the repeating units represented by Z are derived from one or more acid- or salt- containing vinyl monomers.

In a particularly preferred embodiment of this invention, one of R 3 and R4 i.s methyl and the other is ethyl group.

Examples of monomers useful in preparing polymers of this invention are: methoxyethylacrylate or methacrylate, ethoxyethylacrylate or methacrylate, methoxyethoxyethylacrylate or methacrylate, methoxyethylacrylamide or methacrylamide, ethoxyethylacrylamide or methacrylamide, butyl acrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxyethylmethacrylamide, 2-methyl-2—[(l)-oxo-2-propenyl)amino]-l-propane sulfonic acid, or its alkali metal salt, polyprop leneglycol monomethacrylate, polypropyleneglycol monomethacrylamide. The polypropyleneglycol monomers contain from 1 to 20 glycol units.

The copolymers of this invention are free of repeating units containing dye—forming coupler moieties .

Copolymers containing methoxyethylacrylate, methoxyethylacrylamide or methacrylamide, are especially preferred, especially when the property for which an improvement is sought is ferrous ion stability,

Highly preferred polymers useful in this invention can be represented by the structure:

d above, x is 35 to 85 weight percent, y is 10 to 60 weight percent, z is 3 to 10 weight percent, z is 2 to 5 weight percent, and n iε 1 to 20.

The polymers useful in this invention can be prepared by known polymerization processes, such as emulsion and solution polymerization, using known starting materials. Polymers prepared by emulsion polymerization process can be mixed with gelatin and coated directly. Polymers prepared by solution polymerization can be dispersed in two different ways. The first way is to disperse the polymer in the same way that a ballasted coupler is dispersed, with or without a coupler solvent. The thus formed dispersion is mixed with gelatin and coated. The second way iε to diεperse the polymer directly into water if enough units derived from ionizable monomers are present. The dispersion obtained is then mixed with gelatin and coated. A typical emulsion polymerization procedure iε illustrated in the preparative example, infra.

The polymer preferably iε incorporated in the element in the same layer as the silver halide emulsion. It can be present in an amount that will vary depending upon the particular effect desired.

Typically, the polymer can be present in an amount of

3 50 to 1000 mg per square meter or about 5 x 10 to 4

5 x 10 mg per weight silver. A preferred amount is between about 150 and 500 mg per square meter or about

._ / 5 x 10 to 5 x 10 mg per weight silver.

The polymers of this invention can be used with any of the silver halide emulsions employed in color photography. The silver halide can be silver bromide, silver bromoiodide, silver chloride, silver chlorobromide, or another silver halide typically used in photography. The silver halide grains can be of varying habit such as cubic, spherical or tabular. Since tabular grains can adsorb greater amounts of sensitizing dye than grains of other habits, the present invention is particularly effective with such grains. The grains can be fine-grain or coarse-grain or of an intermediate size. The emulsions can be monodisperse, polydisperse or a combination of monodisperse emulsions of different sizes. The grains are spectrally sensitized with a cyanine or merocyanine dye. Typical spectral sensitizing dyes are described in Research Disclosure. December 1989, Item No. 308119, Section IV. The present invention is particularly effective with the anionic sensitizing dyes described in the patents and applications referred to in that section.

Most commonly the silver halide emulsion contains a gelatin vehicle, although modified gelatins and other vehicles can be employed as described in Research Disclosure. December 1989, Item No. 308119, Section IX.

The light sensitive layer in which the polymer of the present invention is contained preferably contains a dye—forming coupler compound. Couplers

which form yellow dyes typically are arylacetanilides such as pivalyl acetanilides and benzolylacetanilides . Couplers which form magenta dyes typical are pyrazolones and pyrazoloazoles such a pyrazolotriazoles. Couplers which form cyan dyes typically are phenols and napthols. The present invention is particularly effective with cyan dye forming couplers and is especially preferred with phenolic couplers which contain substituents in the 2- and 5—positions. Suitable couplers of this type are described in U.S. Patents 3,476,563 and 4,004,929.

Photographic elements of the invention can be single color elements or multicolor elements. Multicolor elements contain dye image—forming units sensitive to each of the three primary regions of the visible spectrum. Each unit can be comprised of a βingle emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image- orming units, can 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 can be disposed as a single segmented layer, e.g., as by the use of microvesselε as described in Whitmore U.S. Patent 4,362,806 issued December 7, 1982.

In the following discussion of suitable materials for use in the emulsionε and elements of this invention, reference will be made to Research Disclosure. December 1989, Item 308119, published by Kenneth Mason Publications Ltd., Emsworth, Hampshire P01070Q England. This publication will be identified hereafter by the term "Research Diεcloεure".

These couplers can be incorporated in the elements and emulsions as described in Research Disclosure..Section VII, paragraph C 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 stabilizers (See Research Disclosure Section VII, paragraphs I and J), light absorbing and scattering materials (See Research Disclosure Section VIII), hardeners (see Research Disclosure Section XI), plasticizers and lubricants (See Research Disclosure Section XII), antistatic agentε (εee Reεearch Disclosure Section XIII), matting agents (see Research Disclosure Section XVI), and development modifiers (see Research Disclosure Section XXI).

The photographic elements can be coated on a variety of supports as described in Research Discloεure Section XVII and the references described therein.

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 Discloεure Section XVIII and then proceεεed 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 color developing agent to reduce developable silver halide and oxidize the color developing agent. Oxidized color developing agent in turn reacts with the coupler to yield a dye.

Preferred color developing agents useful in the invention are p-phenylene diamines. Especially preferred .are 4-amino-N,N-diethyl-aniline hydrochloride, 4-amino-3—methyl—N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N- β-(methanesulfonamido)-ethyl ^' aniline sulfate hydrate, 4-amino-3-methyl-N-ethyl-N-β-hydroxyethylani1ine sulfate, 4-amino-3—β—(methanesulfonamido)ethyl— N,N-diethylaniline hydrochloride and 4-amino-N-ethyl-N- (2-methoxyethyl)-m-toluidine di-p-toluenesulfonic acid. With negative working silver halide, the processing step described above gives 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 uniformly fogging 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 steps of bleaching, fixing, or bleach-fixing, as described above, washing and drying.

The polymers employed in this invention can be prepared by procedureε known in the art and illustrated below. Typically this will be a free radical polymerization leading to an aqueous latex polymer.

The resulting polymer typically iε a high polymer having a molecular weight above about 1 x 10 .

In the exampleε which follow, polymerε which illuεtrate the invention are aε identified in Table 1, part A, which followε and compariεon polymers are identified in Table 1, part B. In these tables the following abbreviation are uεed for the monomers employed:

BA = Butyl acrylate AA = Acrylic acid MAA = methacrylic acid

NaAMP = 2—methyl-2—[(l)-oxo-2-propenyl)amino]- l-propane sulfonic acid sodium salt

M-l is CH 2,.=

The following examples further illustrate this invention:

Preparation of polymer 1-3 Co-poly(methoxyethylacrylate) (ethoxyethylacrylate) (acrylic acid) (2-methyl-2—[(1—oxyl, 2-propenyl) amino] l-propane

ms)

Persulfate(5T_) 8.45

-14-

° The polymer waε prepared aε followε:

1) Group A was added to a 1 liter 4-neck, round-bottom flask equipped with a nitrogen inlet, thermometer, condensor, and a mechanical stirrer. The system was evacuated using an aspirator and filled with 5 nitrogen. Evacuation and filling with nitrogen was repeated three times. The flask was heated to 80°C in a water bath and a nitrogen purge waε maintained during the course of the reaction.

2) The ingredients of Group B were added to 0 the flask and stirred for several minutes. Group C was then added to initiate nucleation. After waiting about 10 minutes until the exothermic reaction had stopped, Groups D and E were added simultaneously to the flask over a period of 4 hours. 5 After all the monomers have been added,

Group F was added and the temperature was raised to 85°C and maintained there for 1 hour until all of the comonomers had reacted. The mixture waε cooled to room temperature, and filtered. The latex polymer was 0 purified by a DC—2 diafiltration unit to remove surfactants and electrolytes .

5

Example 1 Reduction of Sensitizing Dye Stain

Photographic elements were prepared having the following schematic structure:

Overcoat layer: Gelatin-5.4 g/m Bisvmylsulfonylmethylether hardener—95 mg/m 2 i

Light-sensitive layer: gelatin-0.2 g/m

0.9μ silver bromoiodide (3 weight % I, 0.9μ equivalent circular diameter, 7.5:1 aspect ratio)-1.6 g/m ²

The silver bromoiodide grains are spectrally sensitized with 300 mg per weight silver of dye A (see below) and 515 mg per weight silver of dye B (see below).

2 Cyan dye-forming coupler C (see below) 0.89 g/m and

2 Cyan dye forming coupler D (see below) 74 mg/m

Polymer 1-3, see Table II below for amounts

Support - Cellulose acetate

Dye A

Dye B

Coupler D

The photographic elements were exposed through a neutral density step wedge and then processed using the C-41 process as described in the British Journal of Photography. 1982 Annual, pages 209-211. The amount of residual sensitizing dye A and B waε determined by high pressure liquid chromotography.

TABLE II Amount of Polymer 1-3 Sensitizing Sensitizing (mg/m ² ) Dye A Retained Dye B Retained

0 74.4 95.8

80 69.6 75.0

160 63.6 52.3

320 55.0 24.9

It is obεerved from thiε data that the preεence of Polymer 1-3 significantly reduces the amount of sensitizing dye remaining in the photographic element upon procesεing.

Example 2 Reduction of Sens itizing Dye Stain

Photographic elements were prepared having the following schematic structure :

Overcoat layer:

Gelatin-5.4 g/m ²

2 Bisvinylsulfonylmethylether hardener-95 mg/m

Light—senεitive layer:

2 gelatin-0.2 g/m

0.9μ silver bromoiodide (3 weight '/. I, 0.9μ equivalent circular diameter, 7.5:1 aεpect ratio)-1.6 g/m ²

The silver bromoiodide grains are εpectrally εensitized with 300 mg per weight silver of dye A and 515 mg per weight silver of dye B.

2 Cyan dye-forming coupler C 0.89 g/m and

2 Polymer 320 mg/m . See Table I above and Table III below for polymer identification.

Support — Cellulose acetate

From the above, it will be seen that polymers of this invention greatly reduce the sensitizing dye stain.

Example 3 Reduction of Sensitizing Dye Stain

A series of photographic elements were prepared having the following structure:

Overcoat: Gelatin-1.1 g/m ²

2 Hardener-19 mg/m

Light Senεitive Layer

2 Gelatin-1.5 g/m Silver Halide-εee below

Coupler—εee below

Polymer I-3-(see Table IV below for amounts)

Support:

Polyethylene coated paper with a gelatin overcoat

Element A contained a silver chlorobromide emulsion in

2 an amount of 0.33 g/m silver, spectrally sensitized with 122 mg per weight silver of spectral sensitizing

2 dye E. This element also contains 0.62 g/m of coupler F.

Element B contained a silver chlorobromide emulsion in

2 an amount of .32 g/m silver spectrally sensitized with 240 mg per weight silver of sensitizing dye G.

This element contained coupler H.

Element C contained a silver chlorobromide emulsion in

2 an amount of .42 g/m spectrally sensitized with 349 mg per weight silver of sensitizing dye I. This

2 element contained 1.13 g/m of yellow dye-form g coupler J.

Sens. Dye E

Sens. Dye G

Sen . Dye I

Coupler

C ₅ H _u -t

Coupler H

Coupler I

Theεe three elementε were exposed to a neutral density step wedge and then procesεed in the EP-2 process described in The British Journal of Photography, supra.

The amount of residual sensitizing dye in each of the elements was determined as i-n Example 1.

TABLE IV

Amount of Polymer 1-3 Retained Sensitizing (mg/m ² ) Dye mg/m ² -)

Element Element Element A B C

0

80

325

It iε obεerved that preεence of the polymer reduces the amount of sensitizing dye retained.

Example 4 Reduction in Keeping the Fog

A photographic element was prepared like element C described above in Example 3, except that the emulsion

2 was a silver chloride emulsion containing .28 g/m silver. The element was held at 49°C and 50 relative humidity for 2 weeks. The element was then exposed and processed in the EP2 procesε deεcribed in

The British Journal of Photography, εupra. The density

(Dmi•n) in backg°round areas, which receive no exposure, was measured. The resultε are εhown in Table V below.

The above data indicates that polymers of the present invention effect a substantial reduction in fog attributable to keeping.

Example 5 Silver Retention:

The presence of methoxyethylacrylate in the polymer has been shown in published European Patent Application 0 294 104, published December 7, 1988 to be beneficial for minimizing problems associated with leuco cyan dye formation. We have found that the presence of this monomer can aggravate retention of silver in the element by interfering with the bleaching procesε. The preεence of ethoxyethylacrylate in the polymer has less of an impact on retention of silver in the element. Th s, copolymers containing both methoxyethylacrylate and ethoxyethylacrylate minimize problems asεociated with leuco cyan dye and minimize silver dye retention.

An element was prepared having the structure and components shown in Example 2 except that the overcoat

2 contained .2.15 g/m of gelatin, the light-sensitive

2 layer contained 2.2 g/m of gelatin, the silver halide

2 emulsion was present in an amount of 1.6 g silver/m , the couplers employed were couplers C and D, and the polymer employed was from Table 1, as identified below in

Table VI.

The elements were exposed and processed as in Example 1 above. The amount of silver retained was determined from the infra red density of the processed element.

The resultε are εhown in Table VI.

Table VI

Polymer No. Laydown Ag Retention

(mg/m ² ) by IR

1-3

1-1

1-2 1-7

Thiε data shows that polymers containing ethoxyethylacrylate have less of an impact on silver retention than do polymers containing methoxyethylacrylate.

Exa ple 6 Ferrous Ion Stability

Photographic elements were prepared having the following schematic structure:

Overcoat layer:

2 gelatin-5.4 g/m

2 Bisvinylsulfonylmethylether hardener-95 mg/m

Light—sensitive layer: gelatin-0.2 g/m ²

0.9μ silver bromoiodide (3 weight % I, 0.9μ equivalent circular diameter, 7.5:1 aspect ratio)—1.6 g/m 2

The silver bromoiodide grains are spectrally senεitized with 300 mg per weight silver of sensitizing dye A and 515 mg per weight silver of sensitizing dye B.

2 Cyan dye-forming coupler K (see below) 0.74 g/m

2

Polymer 320 mg/m (See Table I above and Table VII below for identification)

Support - cellulose acetate

Coupler K

Ferrous ion stability iε determined as follows

10

Coatings are exposed and processed as described in Example 1. Densitometry of proceεsed stripε iε recorded.

Proceεsed strips are immersed in Solution X

._ (below) under a nitrogen atmosphere for 5 min. , washed lb with water for 5 min., and the densitometry re-read.

The % density loεs from D= .O is shown in Table VII.

20 Solution X: 256.8 g EDTA

220 ml cone NH^OH

229.4 g FeS0 ₄ made up to 8000 ml with water pH 5.0. 5

0

5

Table VII. Fe(II) Stability of Cyan Dye Forming Coupler

Polymer No, % Loss I-l 6.7

1-12 8.2

1-44 9.0

1-2 9.8

1-31 10.4

1-43 11.5

1-45 12.6 1-42 13.5

1-20 15.1

1-46 15.8

1-3 16.7

1-17 20.7

1-37 23.3

1-32 30.2

Comparison Polymers

N-l 90.2

N-2 93

N-4 92.6

N-3 91.5 no polymer 92.5

This data shows that polymers of this invention greatly improve the Fe(II) stability of cyan dye.

This invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.