US3523022A - Photographic element containing a protective matte layer - Google Patents

Description

4, 1970 B. L. J. BYERLY ET AL 3,523,022

PHOTQGRAPHIC ELEMENT CONTAINING A PROTECTIVE MATTE LAYER Filed May 24, 1965 H YDROPH/L /6 LA YER CONTAINING DE SE NS/ 772 E D S/L l/ER HAL/DE O/LVER HAL/DE EMULSION R suPPORr 2 HYDROPH/L/C BACK COAT/N6 FIG.

\ -S/L VER HAL/DE EMULSION SUPPOR 7' HYDROPH/L/C BACK COAT/N6 HYDROPH/L/C LAYER CONTAIN/N6 k DESENS/T/ZED SILVER HAL/DE SILVER HAL/0E EMULS/OA/S CONTAIN/N6 OOLOR FORMERS \APSUPPORT HYDROPH/L/C BACK COAT/N6 BERNARD L. J BYERLEY PETER DAV/S GUY WW STEVENS ATTORNEYS United States Patent US. Cl. 9674 7 Claims ABSTRACT OF THE DISCLOSURE Photographic elements containing a desensitized silver halide matte layer resist deterioration. Silver halide grains which are insensitive to visible radiation and silver halide emulsions containing such grains are useful in a matte layer.

This application relates to photographic elements and more particularly to photographic elements having a protective silver halide emulsion matte coating. It also relates to the preparation of silver halide emulsions of low sensitivity.

It is common to provide photographic silver halide films comprising a support having a silver halide emulsion coated on one side and, on the reverse side, a hydrophilic coating, such as a gelatin coating, to function as an anticurl layer or which may contain an antihalation agent. When such films are stacked or wound on spool, for instance, the silver halide emulsion layer sometimes deteriorates when it comes into contact with the hydrophilic back coating. This deterioration is believed to be due to diffusion of ingredients between the hydrophilic back coating and the emulsion layer. It therefore appears desirable to provide a coating which efiectively prevents this undesired diffusion.

One object of our invention is to provide photographic elements having a support coated with a silver halide emulsion on one side and a hydrophilic back coating on the reverse side, with a layer which inhibits diffusion of ingredients between the emulsion and the hydrophilic back coating when the emulsion and back coating are contacted.

Another object of our invention is to provide photographic elements comprising a support having a hydrophilic coating on one side and, on the opposite side, gelatin silver halide emulsion layers capable of forming colour images overcoated with a protective diffusioninhibiting layer.

A further object of our invention is to provide a method of preparing silver halide emulsions of low sensitivity.

Other objects of our invention will appear herein.

We have found that in photographic elements having a support coated on one side with a light sensitive silver halide emulsion layer, and having a hydrophilic coating on the reverse side, the tendency of substituents to diffuse between the emulsion and the hydrophilic back coatings are in contact with one another may be retarded by providing a protective matte layer, over the emulsion or the hydrophilic back layer, comprising a hydrophilic coating containing coarse grained silver halide which has such low sensitivity to radiation that it is not developed during ordinary exposure and development of the light sensitive silver halide emulsion. The protective coatings of our invention provide good protection against undesired diffusion of substituents between silver halide emulsions and hydrophilic backing layers.

Where we refer in this specification to an emulsion as being insensitive or of a low sensitivity to light, we

mean that the emulsion is in a condition in which it does not show the effects of imagewise exposure in the finally desired image. It will be appreciated that in a negative process, the emulsion must not only be insensitive to light but also unfogged, whereas in a reversal colour process, the emulsion must be fogged completely before imagewise exposure, so that it is not responsive to the imagewise exposure but develops uniformly to silver in the first black-and-white development. The silver is removed in the usual bleach.

In a preferred embodiment of the invention, a photographic element capable of producing colour images comprising a support having coated on one side thereof separate overlying light sensitive silver halide emulsion layers, is overcoated with a hydrophilic layer containining large grained, insensitive silver halide, the other side of the support having a hydrophilic coating. In accordance with this arrangement, diffusion of substituents between the hydrophilic back coating and the sensitive emulsions is effectively inhibited.

In accordance with one embodiment of our invention, we provide a method of precipitating silver halide which features the addition during the precipitation of a bismuth salt to ensure that the silver halide grains precipitated are insensitive.

It is advantageous that the precipitated silver halide grains be of spherical shape (as herein defined) and this may be achieved either by preparing silver halide emulsions by methods of the type described by R. W. Berriman, I. Phot. Sci., 12, 121-133, 1964, or by employing a 1.5 mole percent iodobromide emulsion which has been prepared by precipitating the silver halide grains in the presence of a thallium salt. Suitably, 0.5 gram of thallous nitrate is present per mole of silver halide produced.

Silver halide precipitated in accordance with the invention constitutes a highly useful matting agent for incorporation in the protective, diffusion-inhibiting overcoatings of the invention.

By spherical as employed in this specification, we mean that the silver halide grains are not plate-like as in the majority of silver halide emulsions employed in photography, but have increased thickness so that they more nearly approach a spherical or cubic shape.

The protective coatings of the invention have a matte surface, and appear to inhibit by limiting the area of contact when an emulsion layer is placed in contact with a hydrophilic coating.

FIG. 1 shows a support having coated on one side a hydrophilic back coating and on the reverse side a light sensitive gelatin silver halide emulsion overcoated with a hydrophilic layer containing insensitive silver halide grains.

FIG. 2 shows a light sensitive silver halide emulsion coated on a support, the reverse side of which carries a hydrophilic back coating overcoated with another hydrophilic layer containing insensitive silver halide FIG. 3 illustrates a colour photographic element comprising a support having a hydrophilic back coating on one side and, on the opposite side, a plurality of layers containing light sensitive silver halide salts and colour formers, and having coated thereover a hydrophilic layer containing insensitive silver halide.

Our invention will be further demonstrated in the following examples. Example 1 shows the preparation of silver halide grains useful in accordance with the invention.

EXAMPLE 1 A neutral silver bromide emulsion was precepitated in the usual manner except that varying quantities of bismuth mtrate were added during the precipitation. It was found that 0.5 gram bismuth nitrate per mole of silver halide greatly reduced light sensitivity; that the additionof 1 gram bismuth nitrate per mole of silver provided a greater reduction of light sensitivity, and that when 2 grams bismuth nitrate per mole of silver were employed, all detectable light sensitivity was suppressed.

Photographic elements containing the protective overcoating of the invention are described in Example 2.

EXAMPLE 2 A colour forming photographic element comprising a support having a hydrophilic antihalation back coating on one side an on the reverse side a plurality of light sensitive layers containing silver halide and substituents capable of forming colour images was provided with a protective coating over the light sensitive layers. The protective coating consisted of gelatin and the spherical, completely insensitive silver bromide grains obtained in Example 1 at a concentration of 0.08 to 1.0 gram silver bromide per square meter. When wound on a spool, it was found that the protective layer in accordance with the invention eifectively prevented diffusion of substituents between the light sensitive layers and the hydrophilic antihalation back coating. However, when a colour element of the same composition, but which did not contain the protective layer in accordance with the invention, was wound on a spool, diffusion of substituents between the light sensitive layers and the hydrophilic antihalation coating occurred, resulting in deterioration of the emulsion.

EXAMPLE 3 Example 2 was repeated using insensitive silver chloride grains instead of insensitive silver bromide grains. Similar results were obtained with the additional advantage that no shadowing of the blue-sensitive layer occurred.

The low sensitive silver halide grains utilized in the invention should have a speed at least times less than the image recording emulsion. Silver halide grains of this type may be provided, for example, by employing emulsions which are not digested, or by oxidizing the emulsion with bromine (see Photographic Sensitivity, Lowe et al., London, 1951, pages 112-125,) or by precipitating silver halidegrains by mixing a soluble silver salt and a soluble halide, in the presence of various desensitizers, in particular a bismuth salt. Bismuth nitrate gives highly useful results; other bismuth salts are operable. The preferred concentration range is above 0.1 and most preferably from 0.5 to 4 grams bismuth salt per mole of silver halide produced. Advantageously, a thallium salt is added to the emulsion during precipitation to obtain substantially spherical instead of the usual tabular grains. Also useful are emulsoins known as Burtons emulsions, described in Walls Photographic Emulsions, 1929, pages 52-53. When a completely fogged insensitive emulsion is required it may be prepared in known manner by digesting a silver halide emulsion with certain sulphur compounds, ammonia and excess silver nitrate, alkaline formaline or thiourea dioxide.

Preferably, the insensitive silver halide grains are dispersed in gelatin although other hydrophilic colloid binders, such as polyvinyl alcohol, hydrolyzed polyvinyl acetate and all the colloid binders referred to in US. Pat. 3,039,873, col. 13, lines 40-67, may be employed if desired. Similarly, the hydrophilic back coatings of the invention may be composed of any of those colloids.

Advantageously, when protective layers are provided for colour materials employing blue sensitive layers responding to wavelengths between about 4,000 and 4,800 A., the silver halide grains employed are silver chloride. It has been found that silver bromide and silver bromoiodide grains are relatively opaque to radiation between 4,000 and 4,800 A., whereas silver chloride grains transmit such radiation. The use of silver chloride in the overcoatings thus avoids shadowing which occurs in the blue sensitive layer when silverbromide or silver bromoiodide is employed in the protective layer.

In order to obtain effective results, the silver halide grains incorporated in the protective layers of the in vention must be substantially spherical and have a particle size of at least 0.5 micron, a particle size from 0.5 to about 5l0 microns being particularly suitable. Grain sizes smaller than 0.5 micron are less effective in preventing dilfusion. The concentration of silver halide grains in the protective layer may be about 0.02 to 4.0 grams per square meter, and preferably is about 0.08 to 1.0 gram per square meter.

The unfogged relatively insensitive silver halide emulsions employed in the invention are removable in the fixing baths employed in processing exposed silver halide materials, so that these emulsions do not contribute to the graininess of the images produced in the sensitive emulsion layer, or to any light-scattering effect on subsequent viewing.

This invention is particularly applicable to motionpicture film. When the invention is practiced with colour reversal film, the emulsion is completely fogged before irnagewise exposure to ensure complete development of the insensitive silver halide layer in the first (black and white) development. This can be ensured by excess sulphur digestion, digestion with ammonia and excess silver nitrate, or with alkaline formaline or thiourea dioxide.

The 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 as described hereinabove and as defined in the appended claims.

We claim:

1. A photographic element comprising a support having coated on one side a hydrophilic layer and on the opposite side a gelatin light-sensitive silver halide emulsion layer, and a protective matte layer over one of said layers comprising a hydrophilic colloid containing silver halide grains substantially insensitive to light during normal exposure and development of the light-sensitive silver halide emulsion, said silver halide grains comprising a desensitizer and being substantially spherical in shape and having a mean diameter of at least 0.5 micron.

2. A photographic element according to claim 1, wherein the protective coating is applied over the silver halide emulsion.

3. A photographic element comprising a support having a hydrophilic back coating and on the reverse side a plurality of light-sensitive silver halide containing layers having incorporated therein substances capable of forming color images, and a protective matte coating over said light-sensitive layers comprising a hydrophilic colloid binder dispersed therein substantially light-in-' sensitive silver halide grains, said silver halide grains comprising a desensitizer and being substantially spherical in shape and having a mean diameter of at least 0.5 micron.

4. A photographic element according to claim 3, wherein the silver halide grains are silver chloride.

5. In a photographic element having a support coated with a light-sensitive silver halide emulsion and, on the opposite side, a hydrophilic layer, the improvement which comprises a protective matte coating, over said light-sensitive silver halide emulsion, comprising a hydrophilic colloid having dispersed therein substantially light-sensitive silver halide grains, said silver halide grains comprising a desensitizer and being substantially spherical in shape and having a mean diameter of at least 0.5 micron.

6. A photographic element as in claim 1 wherein said grains is a bismuth salt.

7. A photographic element as in claim 1 wherein said desensitizer for said substantially insensitive silver halide grains is bismuth nitrate.

References Cited 6 OTHER REFERENCES Chem. Abstracts, vol. 59, 1963 (Izu. Inst. Fizikokhim, Bulgar. Akad. Nauk 2, pp. 219-28 (1962)), 4716d.

Chem. Abstracts, vol. 59, 1963 (Sci. Phot. Proc. Intern. 5 Coloq. Liege 1959, pp. 144-51 (pub. 1962)), 3464c.

UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner

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