Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
2001-08-28
2003-08-26
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
C430S502000, C430S503000, C430S567000, C430S546000, C430S631000, C430S556000, C430S557000
Reexamination Certificate
active
06610466
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-258159, filed Aug. 28, 2000; and No. 2001-193596, filed Jun. 26, 2001, the entire contents of both of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photographic lightsensitive material including a spectrally sensitized silver halide photographic emulsion. More particularly, the present invention relates to a photographic lightsensitive material including a silver halide photographic emulsion which exhibits increased light absorption and light absorption intensity and which has sensitizing dyes adsorbed in multilayer form stably even in the presence of an organic solvent.
2. Description of the Related Art
Intensive efforts have been exerted to enhance the sensitivity of silver halide photographic lightsensitive materials. In silver halide photographic emulsions, light sensitivity is obtained as a result of absorption of light incident on the lightsensitive material by a sensitizing dye adsorbed on the surface of silver halide grains and transfer of thus absorbed light energy to silver halide grains. Accordingly, in the spectral sensitization of silver halides, it is contemplated that increasing the light absorption per unit grain surface area of silver halide grains would enable increasing the light energy transferred to silver halides to thereby accomplish enhancement of the spectral sensitivity of silver halide grains. The increasing of the light absorption in the surface of silver halide grains can be accomplished by increasing the adsorption amount of spectral sensitizing dye per unit grain surface area.
However, there is a limit in the adsorption amount of sensitizing dye on the surface of silver halide grains, and it is difficult to adsorb dye chromophores in an amount greater than monolayer saturated adsorption (namely, one-layer adsorption). Therefore, the current situation is that, in the spectral sensitization region, the absorption of incident photons by individual silver halide grains is still low.
Proposals for resolving this matter have been made, which are as follows.
P. B. Gilman, Jr. et al., in Photographic Science and Engineering, vol. 20, no. 3, page 97 (1976), caused the first layer to adsorb a cationic dye and further caused the second layer to adsorb an anionic dye with the use of electrostatic force.
G. B. Bird et al., in U.S. Pat. No. 3,622,316, caused silver halides to adsorb a plurality of dyes in multilayer form and effected sensitization with the contribution of transfer of excitation energy of the Forster type.
Sugimoto et al., in Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-) 63-138341 and JP-A-64-84244, effected spectral sensitization by the energy transfer from luminescent dyes.
R. Steiger et al., in Photographic Science and Engineering, vol. 27, no. 2, page 59 (1983), tried spectral sensitization by the energy transfer from gelatin-substituted cyanine dyes.
Ikegawa et al., in JP-A-61-251842, effected spectral sensitization by the energy transfer from cyclodextrin-substituted dyes.
However, in these proposed methods, the extent of multilayer adsorption of sensitizing dyes on the surface of silver halide grains is actually unsatisfactory with the result that the effect of sensitivity enhancement is extremely poor. Therefore, attempts to realize a substantially effective multilayer adsorption by strengthening the interaction between dye molecules have been made.
It is disclosed in EP No. 838719A2 that increasing of the hydrophobicity of dye molecules would lead to enhancement of the interaction between dye molecules, which is effective in the formation of multilayer adsorption. However, with respect to the thus formed multilayer adsorption, it has become apparent that the state of multilayer adsorption is unstable when an organic solvent is present in the emulsion, especially when a high-boiling organic solvent such as an emulsified substance which is indispensable in the silver halide photographic lightsensitive material is present in the emulsion. Hence, it is an urgent need to develop a technology for stabilizing the state of dye multilayer adsorption.
Parton et al. (JP-A-2000-89406) describe that the stability of multilayer adsorption against external factors such as a dispersion of color forming coupler can be enhanced only when dye layers of the dye multilayer adsorption are bonded with each other through two or more noncovalent attractive forces. However, this stabilization effect is not so high, and, when employed in practicable silver halide photographic lightsensitive materials containing a high-boiling organic solvent, it is difficult to realize such a stability as can endure practical use. Furthermore, substituents are limited, so that the variety of available dyes is limited.
In contrast, it is known that a multilayer adsorption based on a combination of cationic dyes is effective in the enhancements of light absorption and sensitivity. However, the stability of multilayer adsorption is still poor against external factors such as a dispersion of color forming coupler.
The development processing time of color negative lightsensitive materials has been shortened by Kodak processing C-41 introduced in 1972. The wet processing time, not including any drying step, required by the processing is 17 min 20 sec. The processor CN-16FA introduced in the mini-lab market by Fuji Photo Film Co., Ltd. in recent years has enabled shortening the wet processing time to 8 min 15 sec. However, the current situation is that the shop processing and finishing, even speediest in view of the contemporary processing time level, still requires about 30 min to thereby compel a majority of users to make two visits to the photograph shop. Thus, further shortening of development processing time is desired in order to meet the demand for one visit to photograph shop from users.
Reduction of development time by raising the developing temperature of color developer has been investigated in order to attain shortening of color development time. However, the intended shortening is not easy because of the occurrence of sensitivity lowering and because of the increase of photographic property change due to processing variation. Improving the ratio of sensitivity/graininess by effecting a short-time processing is disclosed in JP-A-62-192740. However, the demanded level has not yet been attained thereby. Therefore, there is still a strong demand for improvement of the ratio of sensitivity/graininess and for suppression of the photographic property change due to processing variation.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a photographic lightsensitive material including a silver halide photographic emulsion which is highly sensitive and wherein sensitizing dyes are contained in multilayer form stably even in the presence of an organic solvent.
The inventors have made extensive and intensive studies with a view toward attaining the above object. As a result, it has been found that the stability of dye multilayer adsorption can be dramatically enhanced by the use of specified emulsified substance to thereby attain an effective enhancement of spectral sensitivity even in practical silver halide photographic lightsensitive materials wherein a high-boiling organic solvent is present.
Specifically, although, with respect to highly hydrophobic dyes, it is contemplated that the state of multilayer adsorption is unstable because of their high solubility in organic solvents, there is no report regarding the interrelationship between properties of high-boiling organic solvents and stability of multilayer adsorption, and there is no knowledge as to the interrelationship between properties of surfactants required for dispersing high-boiling organic solvents, or types of color forming couplers dissolved in high-boiling organic solvents, and stability of multilayer adsorption. No
Morimoto Kiyoshi
Sakurada Masami
Ueda Fumitaka
Yamada Toru
Birch & Stewart Kolasch & Birch, LLP
Fuji Photo Film Co. , Ltd.
Letscher Geraldine
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