Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-09-13
2001-12-11
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S574000, C430S576000, C430S577000, C430S578000, C430S579000, C430S580000, C430S581000, C430S582000, C430S583000, C430S584000, C430S585000, C430S586000, C430S587000, C430S588000, C430S590000, C430S591000, C430S592000, C430S593000, C430S594000, C430S595000
Reexamination Certificate
active
06329133
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a silver halide color photographic material containing at least one silver halide emulsion having enhanced light absorption.
BACKGROUND OF THE INVENTION
J-aggregating cyanine dyes are used in many photographic systems. It is believed that these dyes adsorb to a silver halide emulsion and pack together on their “edge” which allows the maximum number of dye molecules to be placed on the surface. However, a monolayer of dye, even one with as high an extinction coefficient as a J-aggregated cyanine dye, absorbs only a small fraction of the light impinging on it per unit area. The advent of tabular emulsions allowed more dye to be put on the grains due to increased surface area. However, in most photographic systems, it is still the case that not all the available light is being collected.
Increasing the absorption cross-section of the emulsion grains should lead to an increased photographic sensitivity. The need is especially great in the blue sensitization of the yellow layer of color negative photographic elements. This is because not all incident blue light is absorbed by the typical blue-sensitive emulsions in practical multilayer films. Higher speed in this layer can be used to obtain improved color and image quality characteristics.
One way to achieve greater light absorption is to increase the amount of spectral sensitizing dye associated with the individual grains beyond monolayer coverage of dye (some proposed approaches are described in the literature, G. R. Bird,
Photogr. Sci. Eng.,
18, 562 (1974)). One method is to synthesize molecules in which two dye chromophores are covalently connected by a linking group (see U.S. Pat. Nos. 2,518,731, 3,976,493, 3,976,640, 3,622,316, Kokai Sho 64(1989)91134, and EP 565,074). This approach suffers from the fact that when the two dyes are connected they can interfere with each other's performance, e.g., not aggregating on or adsorbing to the silver halide grain properly.
In a similar approach, several dye polymers were synthesized in which cyanine dyes were tethered to poly-L-lysine (U.S. Pat. No. 4,950,587). These polymers could be combined with a silver halide emulsion, however, they tended to sensitize poorly and dye stain (an unwanted increase in D-min due to retained sensitizing dye after processing) was severe in this system and unacceptable.
A different strategy involves the use of two dyes that are not connected to one another. In this approach the dyes can be added sequentially and are less likely to interfere with one another. Miysaka et al. in EP 270 079 and EP 270 082 describe silver halide photographic element having an emulsion spectrally sensitized with an adsorbable sensitizing dye used in combination with a non-adsorbable luminescent dye which is located in the gelatin phase of the element. Steiger et al. in U.S. Pat. Nos. 4,040,825 and 4,138,551 describe silver halide photographic element having an emulsion spectrally sensitized with an adsorbable sensitizing dye used in combination with second dye which is bonded to gelatin. The problem with these approaches is that unless the dye not adsorbed to the grain is in close proximity to the dye adsorbed on the grain (less than 50 angstroms separation) efficient energy transfer will not occur (see T. Förster,
Disc. Faraday Soc.,
27, 7 (1959)). Most dye off-the-grain in these systems will not be close enough to the silver halide grain for energy transfer, but will instead absorb light and act as a filter dye leading to a speed loss. A good analysis of the problem with this approach is given by Steiger et al. (
Photogr. Sci. Eng.,
27, 59 (1983)).
A more useful method is to have two or more dyes form layers on the silver halide grain. Penner and Gilman described the occurrence of greater than monolayer levels of cyanine dye on emulsion grains,
Photogr. Sci. Eng.,
20, 97 (1976); see also Penner,
Photogr. Sci. Eng.,
21, 32 (1977). In these cases, the outer dye layer absorbed light at a longer wavelength than the inner dye layer (the layer adsorbed to the silver halide grain). Bird et al. in U.S. Pat. No. 3,622,316 describe a similar system. A requirement was that the outer dye layer absorb light at a shorter wavelength than the inner layer. The problem with previous dye layering approaches was that the dye layers described produced a very broad sensitization envelope. This would lead to poor color reproduction since, for example, the silver halide grains in the same color record would be sensitive to both green and red light.
Yamashita et al. (EP 838 719 A2) describes the use of two or more cyanine dyes to form dye layers on silver halide emulsions. The dyes are required to have at least one aromatic or heterocyclicaromatic substitutent attached to the chromophore via the nitrogen atoms of the dye. This is undesirable because such substitutents can lead to large amounts of retained dye after processing (dye stain) which affords increased D-min. We have found that this is not necessary and that neither dye is required to have at least one aromatic or heterocyclicaromatic substitute attached to the chromophore via the nitrogen atoms of the dye. The dyes of our invention give increased photographic sensitivity.
Yasuhiro et al. (U.S. Pat. No. 4,518,689) describe an inner latent image type silver halide photographic emulsion spectrally sensitized with a cationic monomethine dye and an anionic monmethine dye. Yamashita et al. (Japenese Kokai Patent Application No. Hei 10 [1998]-171058) describes the use of two or more dyes to form dye layers on silver halide emulsions characterized by containing an anionic dye and a cationic dye where the charge of either the anionic dye or the cationic dye is 2 or greater.
However, the methods described above do not sufficiently provide increased sensitivity. Thus, further technology is required.
PROBLEM TO BE SOLVED BY THE INVENTION
Not all the available light is being collected in many photographic systems. The need is especially great in the blue spectral region where a combination of low source intensity and relatively low dye extinction result in deficient photoresponse. The need for increased light absorption is also great in the green sensitization of the magenta layer of color negative photographic elements. The eye is most sensitive to the magenta image dye and this layer has the largest impact on color reproduction. Higher speed in this layer can be used to obtain improved color and image quality characteristics. The cyan layer could also benefit from increased red-light absorption which could allow the use of smaller emulsions with less radiation sensitivity and improved color and image quality characteristics. For certain applications it may be useful to enhance infrared light absorption in infrared sensitized photographic elements to achieve greater sensitivity and image quality characteristics.
SUMMARY OF THE INVENTION
Commonly assigned, co-pending application Ser. No. 09/151,915, filed on Sep. 11, 1998 describes increased light absorption in a photographic system. This is achieved by forming two dye layers on silver halide held together by more than one non-covalent force by use of at least one dye having at least one anionic substituent and at least one dye having at least one cationic substituent. However, we have found that increasing light absorption in this manner is less effective than desired in photographic materials that contain anionic surfactants, such as those generally used to make color coupler dispersions. We have found that blue dyes in particular, are easily attracted by other chemical species in the emulsion with affinity to blue dye molecules, which ultimately results in the disruption of the dye layers. The net result of these undesirable competitive interactions is decreased light absorption and reduced speed. We have now found that certain dye structures provide the desired enhanced light absorption in a color photographic element, including photographic elements that contain an anionic surfactant in the coupler dispersion.
We have found t
Andrievsky Andrei
Harrison William J.
Parton Richard L.
Penner Thomas L.
Chea Thorl
Eastman Kodak Company
Rice Edith A.
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