Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2002-10-09
2004-08-24
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S570000, C430S573000, C430S574000, C430S575000, C430S576000, C430S581000, C430S599000, C430S600000
Reexamination Certificate
active
06780577
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photographic material in which a spectrally sensitized silver halide photographic emulsion is used.
BACKGROUND OF THE INVENTION
A great endeavor has been tried for increasing the sensitivity of a silver halide photographic material. In a silver halide photographic emulsion, a sensitizing dye adsorbed onto the surface of a silver halide grain absorbs rays of light incident on the photographic material and transmits the light energy to the silver halide grain, thereby sensitivity can be obtained. It is thought, accordingly, that the light energy transmitted to a silver halide can be increased by increasing the light absorption rate per the unit surface area of a silver halide grain in the spectral sensitization of silver halide, as a result, the enhancement of spectral sensitivity can be attained. It is preferred to increase the adsorption amount of a spectral sensitizing dye per the unit surface area of a silver halide grain for improving the light absorption rate of the surface of the silver halide grain.
However, there is a limit in the adsorption amount of a sensitizing dye onto the surface of a silver halide grain, and it is difficult to adsorb the dye chromophore of the amount more than the amount by a monolayer saturation adsorption (i.e., the adsorption by a single layer) onto a silver halide grain. Accordingly, the absorption rate of the incident light quantum of each silver halide grain in the spectral sensitization region is still low in the present situation.
The means suggested to solve these points will be described below.
P. B. Gilman, Jr. et al. tried to adsorb a cationic dye onto the first layer (of a silver halide grain) and an anionic dye onto the second layer by electrostatic force as described in
Photographic Science and Engineering
, Vol. 20, No. 3, page 97 (1976).
G. B. Bird et al. tried to multilayer-adsorb a plurality of dyes onto silver halide to effect sensitization by virtue of the transfer of Forster type excitation energy in U.S. Pat. No. 3,622,316.
Sugimoto et al. performed spectral sensitization due to energy transfer from a luminescent dye as disclosed in JP-A-63-138341 and JP-A-64-84244 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).
R. Steiger et al. tried spectral sensitization due to energy transfer from a gelatin-substituted cyanine dye in
Photographic Science and Engineering
, Vol. 27, No. 2, page 59 (1983).
Ikekawa et al. performed spectral sensitization due to energy transfer from a cyclodextrin-substituted dye in JP-A-61-251842.
Richard Parton et al. tried multilayer-adsorption using a cationic dye and an anionic dye in combination to increase sensitivity by virtue of the transfer of energy from the dye in the second layer to the dye in the first layer as disclosed in EP-A-0985964, EP-A-0985965, EP-A-0985966 and EP-A-0985965.
However, these techniques could not bring about multilayer-adsorption of sensitizing dyes onto the surface of a silver halide grain in a sufficient degree in practice, and so the improving effect of sensitivity was extremely small.
Yamashita et al. realized an increase in sensitivity by virtue of multilayer-adsorption by a cationic dye and an anionic dye having an aromatic group in JP-A-10-239789.
So-called connected dyes having two chromophores which are not conjugated separately and connected by a covalent bond are prospective for the purpose of efficiently transmitting light absorption energy to silver halide to thereby increase sensitivity and for the purpose of raising the stability of the dye in the second layer, since the dye moiety which is not adsorbed onto the silver halide and the dye moiety adsorbed onto the silver halide can be approached by the covalent bond.
Connected dyes are disclosed, e.g., in U.S. Pat. Nos. 2,393,351, 2,425,772, 2,518,732, 2,521,944, 2,592,196 and EP 565083. However, these dyes were not dyes aiming at the improvement of light absorption rate. As the dyes aiming at the improvement of light absorption rate actively, G. B. Bird, A. L. Borror et al. contrived to increase sensitivity in U.S. Pat. Nos. 3,622,317 and 3,976,493 by virtue of energy transfer by adsorbing connecting type sensitizing dye molecules having a plurality of cyanine chromophores onto silver halide to thereby heighten the light absorption rate. Ukai, Okazaki and Sugimoto proposed in JP-A-64-91134 to bond at least one substantially non-adsorptive cyanine, merocyanine or hemicyanine dye containing at least two sulfo groups and/or carboxyl groups to a spectral sensitizing dye adsorptive onto silver halide.
L. C. Vishwakarma showed a method of synthesizing a connected dye by a dehydration condensation reaction of two dyes in JP-A-6-57235. Further, L. C. Vishwakarma showed in JP-A-6-27578 that a connected dye comprising monomethine cyanine and pentamethine oxonol had red-sensitivity, but spectral sensitization by virtue of the transfer of Forster type excitation energy between the dyes was not effected in this case because the emission of the oxonol dye did not overlap the absorption of the cyanine dye. Therefore, an increase in sensitivity by the light converging function of the connected oxonol cannot be obtained.
R. L. Parton et al. reported in EP-A-887770 the enhancement of sensitivity by a compound comprising a merocyanine dye connected with a cyanine dye by a linking group containing a hetero atom, but the effect of improving light absorption was not sufficient.
M. R. Roberts et al. suggested spectral sensitization by a cyanine dye polymer in U.S. Pat. No. 4,950,587.
In the above-described multilayer adsorption systems, dye chromophores were selected so that the emission spectrum of the second layer and the absorption spectrum of the first layer overlapped each other for the purpose of rapidly bringing about Forster type energy transfer from the second layer to the first layer. (
Th. Forster, Discuss. Faraday Soc
., 27, 7, (1959).)
However, the intended sensitivity improving effect could not be obtained in practice, even in multilayer adsorption systems wherein Forster type energy transfer is capable of being brought about in theory.
As a result of eager investigation, the present inventors have found that sensitivity can be improved so long as the duration of life of excitation state of the dye in the second layer of the multilayer adsorption system is long, or the emission velocity of the dye in the second layer is great, even if the condition is not such that the emission spectrum of the second layer and the absorption spectrum of the first layer overlap each other under which Forster type energy transfer is conventionally thought to be liable to take place. That is, it has been found that higher sensitization can be realized even if Forster type energy transfer does not take place.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a silver halide photographic emulsion which is highly sensitized by multilayer adsorption of sensitizing dyes selected by reflecting the nature of excitation state directly observed.
The above object of the present invention can be attained by the following means.
(1) A silver halide photographic material containing silver halide grains onto which a sensitizing dye in the first layer and a sensitizing dye or dyes in the second or after layers are multilayer-adsorbed, wherein the fluorescence life time of the dye or dyes in the second or after layers on the silver halide grain surface measured at a maximum wavelength of fluorescence spectrum is shorter than the fluorescence life time of the dye or dyes in a gelatin dry film measured at a maximum wavelength of fluorescence spectrum.
(2) A silver halide photographic material containing silver halide grains onto which a sensitizing dye in the first layer and a sensitizing dye or dyes in the second or after layer are multilayer-adsorbed, wherein the value obtained by dividing the fluorescence yield of the dye or dyes in the second or after layers measured in a gelatin dry film by the fluorescence life time of t
Fuji Photo Film Co. , Ltd.
Letscher Geraldine
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