Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
1999-01-25
2003-03-11
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
C430S567000, C430S569000, C430S581000, C430S583000, C430S584000, C430S585000, C430S586000, C430S587000, C430S588000, C430S590000, C430S591000, C430S592000, C430S600000
Reexamination Certificate
active
06531272
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a color photographic element having improved photographic response.
Definitions
A tabular grain emulsion is one in which at least 50 percent of total grain projected area is accounted for by tabular grains.
As employed herein the term “tabular grain” is employed to indicate grains that have two parallel major faces substantially larger than any remaining face and that exhibit an aspect ratio of at least 2.
Aspect ratio is the ratio of tabular grain equivalent circular diameter (ECD) divided by thickness (t). The average aspect ratio of a tabular grain emulsion is the ratio of average grain ECD divided by average grain thickness.
A 3D emulsion is one in which at least 50 percent of total grain projected area is accounted for by 3D grains. As used herein, the term “3D grain” refers to non-tabular morphologies, for example cubes, octahedra, rods and spherical grains, and to tabular grains having an aspect ratio of less than 2.
In referring to grains and emulsions containing two or more halides, the halides are named in order of ascending concentrations.
BACKGROUND OF THE INVENTION
It is a long-standing objective of color photographic origination materials to maximize the overall response to light while maintaining the lowest possible granularity. Increased photographic sensitivity to light (commonly referred to as photographic speed) allows for improved images captured under low light conditions or improved details in the shadowed regions of the image. In general, the overall light sensitivity provided by the light sensitive silver halide emulsions in such systems is determined by the size of the emulsions. Larger emulsions capture more light. In color photographic elements, upon development, the captured light is ultimately converted into dye deposits which constitute the reproduced image. However, the granularity expressed by these dye deposits is directly proportional to the grain size of the silver halide emulsion. Thus, larger silver halide emulsion grains have higher sensitivity to light but also lead to higher granularity in the reproduced image. It has been a long-standing problem to provide materials which maximize the response to light of a silver halide emulsion for any given grain size.
It is of particular interest to find solutions to this problem for large emulsions with the potential for providing high speed (preferably ISO 400 or greater) color photographic materials. Such high speed materials have a number of potential applications. They are particularly valuable for use in cameras with zoom lenses and in single use cameras (also called “film with lens” units). Zoom lenses generally have smaller apertures (higher f-numbers) than comparable fixed focus lenses. Thus, zoom lenses, while giving increased flexibility in composition of a pictorial scene, deliver less light to the camera film plane. Use of high speed films allows the flexibility of zoom lenses while still preserving picture taking opportunities at low light levels. In single use cameras, lens focus is fixed. Here, high speed films allow use of a fixed aperture having a higher f-number, thus increasing the available depth of field, an important feature in a fixed focus camera. For single use cameras with flash, higher film speed allows pictures to be taken with a less energetic flash, enabling more economical manufacture of the single use unit.
The problem of maximizing response of the emulsion grain to light is particularly important for the blue sensitive emulsions of high speed materials, since standard scene illuminants are at least somewhat deficient in blue light. As a result, 3D AgBrI emulsions with light absorption enhanced by high iodide content are generally employed in the fast yellow emulsion layer of the highest speed color photographic films. Unfortunately, these large fast yellow 3D emulsions also compromise the acutance of underlying layers. Tabular grains as fast yellow emulsions offer advantages for acutance of underlying layers but up until now have been deficient for adequate speed/granularity.
SUMMARY OF THE INVENTION
We have discovered that adding a fragmentable electron donor to an emulsion comprising large tabular grains enables these emulsions to achieve speed/granularity adequate for high speed photography.
One aspect of this invention comprises a multicolor photographic element comprising a support bearing a cyan dye image-forming unit comprising at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler, wherein at least one of said layers comprises large tabular grains having an equivalent circular diameter (ECD) of greater than 2 &mgr;m and contains a fragmentable electron donating compound is of the formula: X—Y′ or a compound which contains a moiety of the formula —X—Y′; wherein
X is an electron donor moiety, Y′ is a leaving proton H or a leaving group Y, with the proviso that if Y′ is a proton, a base, &bgr;
−
, is covalently linked directly or indirectly to X, and wherein:
1) X—Y′ has an oxidation potential between 0 and about 1.4 V; and
2) the oxidized form of X—Y′ undergoes a bond cleavage reaction to give the radical X
•
and the leaving fragment Y′; and, optionally,
3) the radical X
•
has an oxidation potential ≦−0.7V (that is, equal to or more negative than about −0.7V).
Another aspect of this invention comprises a single use camera comprising a roll of film, a taking lens, a shutter release, a film advance and a viewfinder, wherein the roll of film comprises a transparent support bearing a cyan dye image-forming unit comprising at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler, wherein at least one of said layers comprises large tabular grains having an average equivalent circular diameter of greater than 2 &mgr;m and contains a fragmentable electron donor compound of the formula X—Y′ or a compound which contains a moiety of the formula —X—Y′; wherein
X is an electron donor moiety, Y′ is a leaving proton H or a leaving group Y, with the proviso that if Y′ is a proton, a base, &bgr;
−
, is covalently linked directly or indirectly to X, and wherein:
1) X—Y′ has an oxidation potential between 0 and about 1.4 V; and
2) the oxidized form of X—Y′ undergoes a bond cleavage reaction to give the radical X
•
and the leaving fragment Y′; and, optionally,
3) the radical X
•
has an oxidation potential ≦−0.7V (that is, equal to or more negative than about −0.7V).
DETAILED DESCRIPTION OF THE INVENTION
In accordance with this invention a silver halide emulsion contains a fragmentable electron donating (FED) compound which enhances the sensitivity of the emulsion. The fragmentable electron donating compound is of the formula X—Y′ or a compound which contains a moiety of the formula —X—Y′; wherein
X is an electron donor moiety, Y′ is a leaving proton H or a leaving group Y, with the proviso that if Y′ is a proton, a base, &bgr;
−
, is covalently linked directly or indirectly to X, and wherein:
1) X—Y′ has an oxidation potential between 0 and about 1.4 V; and
2) the oxidized form of X—Y′ undergoes a bond cleavage reaction to give the radical X
&b
Friday James A.
Hansen Jeffrey C.
Lenhard Jerome R.
Muenter Annabel A.
Pepe Joseph P.
Baxter Janet
Eastman Kodak Company
Rice Edith A.
Walke Amanda C.
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