Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Patent
1993-03-13
1995-01-03
Bowers, Jr., Charles L.
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
430503, 430567, 430379, G03C 146
Patent
active
053785916
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a reversal color photographic material.
The silver halide materials, reversal or not, for the color reproduction generally include three blue, green and red-sensitive elements respectively which respectively provide the yellow, magenta and cyan components of the subtractive synthesis in the color image.
The reversal materials are those, which after being exposed, undergo a silver development of the latent image (black and white development), then a reversal, which consists in rendering developable the unexposed residual silver halides by means of a fogging exposure or a chemical fog, and subjecting these fogged silver halides to a color-forming development in the presence of a color developing agent and a coupler, the latter being generally incorporated into the reversal material.
Each sensitive element includes, in one or more layers, silver halide emulsions having different speeds. In general, the fastest emulsions comprise the coarsest silver halide grains whereas the slowest ones contain the smallest grains, although the speed differences may be adjusted in another way, for example by means of different chemical sensitizations.
Such emulsion mixtures sensitized to the same region of the visible spectrum, in one or more layers, are conventionally used in order to decrease the contrast and in general, to obtain the desired curve shapes, acting on the mixture proportions.
Thus, for example, British Patents 732,691 and 818,687 and German Patent 1,121,470 disclose mixtures of slow and fast emulsions, in the same layer or in separate layers of color photographic materials.
It is advantageous for such mixtures to use silver halide emulsions comprising grains exhibiting a narrow grain distribution, or monodisperse emulsions. Indeed, these emulsions can be prepared in a more reproducible way and by blending these monodisperse emulsions, the curve shapes can be adjusted according to the desired results.
Monodisperse emulsions, in the present disclosure, are emulsions which grain size distribution or variation coefficient (COV) is equal or less than 20%. The variation coefficient is represented by the formula: ##EQU1## wherein .sigma. is the standard deviation and D the average grain size, represented by the average diameter when the grains are spherical and by the average value of the diameter of the circular images having the same surface as the projected images of the grains, when the grains are not spherical.
Methods for preparing monodisperse emulsions are disclosed, for example in U.S. Pat. No. 3,574,628 and British Patent 1,586,412; the latter patent mentions that such monodisperse emulsions can be used in any types of photographic materials, particularly in reversal color materials. In various patents, for example in French Patent 1,367,941 and U.S. Pat. No. 3,761,276, color photographic materials are disclosed wherein all the emulsions are monodisperse.
However, the monodisperse emulsions exhibit the drawback that the coarse grain emulsions, having a grain size more than 1 .mu.m, are very sensitive to the processing conditions, for example to the stirring and the developing agent ageing, and/or exhibit a slow color development kinetics with some couplers.
These developability problems associated to monodisperse emulsions are well known and it has already been attempted to solve them.
For example, U.S. Pat. No. 4,640,890 discloses a reversal color photographic material wherein all the slow emulsions are monodisperse emulsions, the size distribution of the fast emulsions being not critical. Color photographic materials wherein a mixture, in one or more layers, of polydisperse and monodisperse emulsions is used, are disclosed for example in U.S. Pat. Nos. 4,554,245, 4,670,375, and 4,727,016. However, it was observed that, with such materials, reciprocity law failures cannot be reduced as they are advantageously when all the emulsions are monodisperse. Moreover, it can be seen according to the comparative examples of U.S. Pat. No. 4,640,890, that this structure does not provi
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"Some Aspects of the Reciprocity Law in Silver Chloride Emulsions" by P. Faelens, pp. 100-105, Photographic Science & Engineering, vol. 26, No. 2, Mar. 1982.
Droin Gerard M.
Kempen Simone J.
Bowers Jr. Charles L.
Eastman Kodak Company
Letscher Geraldine
Stewart Gordon M.
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