Methine compound and silver halide photographic material

Details Methine compound and silver halide photographic material Methine compound and silver halide photographic material

2000-11-22

2002-10-15

Letscher, Geraldine (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Radiation sensitive product

Silver compound sensitizer containing

C430S582000, C430S583000, C430S584000, C430S585000, C430S586000, C430S587000, C430S588000, C430S570000

Reexamination Certificate

active

06465166

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a spectrally sensitized silver halide photographic emulsion and a photographic light-sensitive material using such an emulsion.
BACKGROUND OF THE INVENTION
Hitherto, considerable efforts have been made to increase the sensitivities of silver halide photographic materials. The silver halide photographic emulsions constituting a photographic material get sensitivities through a mechanism that the sensitizing dyes adsorbed to the surfaces of silver halide grains absorb light incident on the photographic material and the light energy absorbed by the dyes is transferred to the silver halide grains. In the spectral sensitization of silver halide, therefore, an increase in spectral sensitivity is thought to be achieved by raising the light-absorption rate per unit grain surface area of silver halide grains to increase the light energy transferred to silver halide. In order to raise the light-absorption rate on the silver halide grain surface, it would be proper to increase the quantity of spectral sensitizing dye adsorbed per unit grain surface area.
However, there is a limit to a quantity of sensitizing dye adsorbed to the silver halide grain surface, and so it is difficult to make dye chromophores adsorb to the grain surface in a quantity larger than the quantity for saturated adsorption in a state of single layer (namely one-layer adsorption). Accordingly, the absorption rate of incident photons by individual silver halide grains in a spectral sensitization region is still low under present conditions.
The methods hitherto proposed to solve such a problem are described below.
According to the method proposed by P. B. Gilman, Jr. et al. in
Photographic Science and Engineering,
vol. 20, No. 3, p. 97 (1976), a cationic dye is adsorbed as the first layer and then the second layer is formed by making an anionic dye adsorb to the cationic dye through the use of electrostatic force.
In the method disclosed by G. B. Bird et al. in U.S. Pat. No. 3,622,316, dyes of many kinds are adsorbed to silver halide in a multi-layer state, and the silver halide is sensitized by contribution of Forster-type excited energy transfer.
In JP-A-63-138341 and JP-A-64-84244 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), Sugimoto et al. disclose the spectral sensitization by energy transfer from luminescent dyes.
The attempt at spectral sensitization by energy transfer from gelatin-substituted cyanine dyes is reported by R. Steiger in
Photographic Science and Engineering,
vol. 27, No. 2, p. 59 (1983).
Ikegawa et al. disclose in JP-A-61-251842 the spectral sensitization by energy transfer from cyclodextrin-substituted dyes.
The dyes having in each molecule two separate chromophores which are not conjugated but connected together by covalent bond(s), or the so-called connecting dyes, are disclosed in, e.g., U.S. Pat. Nos. 2,393,351, 2,425,772, 2,518,732, 2,521,944 and 2,592,196, and European Patent 565,083. Therein, however, those dyes are not aimed at an increase in light-absorption rate. As to the cases aimed positively at improvement in light-absorption rate, the attempts to increase the light-absorption rate by adsorption of connected sensitizing dye molecules having plural cyanine chromophores per molecule and achieve sensitization by contribution of energy transfer are disclosed by G. B. Bird, A. L. Borror et al. in U.S. Pat. Nos. 3,622,317 and 3,976,493.
In JP-A-64-91134, Ukai, Okazaki and Sugimoto advance the proposal to bind at least one substantially non-adsorptive cyanine, merocyanine or hemicyanine dye having at least two sulfo and/or carboxyl groups to a spectral sensitizing dye which can be adsorbed to silver halide.
On the other hand, L. C. Vishwakarma discloses in JP-A-6-57235 the method of synthesizing connecting dyes by dehydration condensation of two dyes. Further, he discloses in JP-A-6-27578 that the connecting dye consisting of a monomethinecyanine and a pentamethineoxonol has red sensitivity. In this case, however, there is no overlap between the luminescence of the oxonol and the absorption of the cyanine, and so the spectral sensitization by excited energy transfer of Förster type is not caused between dye moieties; as a result, there is no hope of an increase in sensitivity by light-condensing action of oxonol.
Further, the connecting dyes having special linking groups are proposed by R. L. Parton et al. in EP-A1-887700.
In addition, the spectral sensitization by cyanine dye polymers are proposed by M. R. Roberts et al. in U.S. Pat. No. 4,950,587.
As mentioned above, a large number of studies have so far been made for the purpose of improving the light-absorption rate, but any of them fails in achieving a sufficient effect of increasing light-absorption rate as well as satisfactory increase in sensitivity.
In the case of color photosensitive materials, it is further required to put their spectral sensitivities in the intended wavelength regions. For spectrally sensitizing a silver halide photosensitive material, the absorption of a sensitizing dye in a state of monomer is not used, but the J-band formed upon adsorption of sensitizing dyes to the surface of silver halide grains is generally utilized. The J-band has a very sharp absorption at wavelengths shifted to the longer wavelength side than the wavelengths at which the dye monomer shows its absorption. Therefore, the J-band is very useful for putting both light-absorption and spectral sensitivity in the desired wavelength region. Even if the adsorption of sensitizing dye to the grain surface in a multiple layer enables an increase in light-absorption rate, the sensitizing dye exhibits very broad absorption so far as the dye which is not directly adsorbed to silver halide grains, namely the dye forming the second layer and above, is in a state of monomer. Accordingly, the adsorption in a monomer state cannot impart practical spectral sensitivity to photosensitive materials.
On the other hand, each of color sensitive regions has a width of about 100 nm, and it is undesirable that greater differences than needed arise between the sensitivities to rays of light in the foregoing wavelength region.
Under these circumstances, it has been desired to develop arts of confining the absorption and the spectral sensitivity within the desired width of each color sensitive region, and besides, reducing variations in spectral absorptivity and sensitivity as greatly as possible in regard to the light of the foregoing wavelength region while increasing the areal intensity of light absorption per unit grain surface area by multi-layer adsorption of sensitizing dye to the silver halide grain surface.
On the other hand, it has been found that silver halide grains tend to agglomerate when sensitizing dye is adsorbed to the grain surface in a multiple layer, because the quantity of gelatin adsorbed is decreased to lower protective colloid ability. Therefore, it has also been desired to develop arts of achieving both multi-layer adsorption of sensitizing dye and control of grain agglomeration.
As a method for fulfilling those desires, we have already found the method of using an aromatic group-containing dye or the method of using an aromatic group-containing cationic dye in combination with an anionic dye, as disclosed in JP-A-10-239789, JP-A-8-269009, JP-A-10-123650 and JP-A-8-328189. However, such a method uses a highly hydrophobic dye as sensitizing dyes, so that it has a problem of causing a high level of residual color of dyes after processing, as compared with the cases of using conventional sensitizing dyes.
SUMMARY OF THE INVENTION
Therefore, one object of the present invention is to provide a high speed silver halide photographic emulsion wherein the grain agglomeration is prevented, and at the same time to provide a photographic light-sensitive material comprising such an emulsion, and further to provide a silver halide photographic material which is reduced in residual color of dyes after processing.
Another object of the invention is to

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