Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-03-29
2003-03-18
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S505000, C430S569000
Reexamination Certificate
active
06534256
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-091213, filed Mar. 29, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a silver halide photographic lightsensitive material improved with respect to a ratio of photographic speed/radiation fog.
In recent years, the demands for photographic lightsensitive materials, especially lightsensitive materials for photographing, are becoming stricter. It is now demanded to attain not only a high photographic speed but also a further reduction of radiation fog. Thus, it is desired to develop an emulsion improved with respect to them.
The techniques for enhancing the photographic speed of silver halide emulsions include one wherein tabular silver halide grains (hereinafter simply referred to as “tabular grains”) are incorporated in silver halide emulsions. With respect to tabular grains, for example, U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306 and 4,459,353, Jpn. Pat. Appln. KOKAI Publication No. (herein after referred to as JP-A-) 59-99433 and JP-A-62-209445 disclose processes for producing the same and techniques for use thereof. It is known that the tabular grains are advantageous in attaining, for example, an enhancement of photographic speed including enhancement of color sensitization efficiency by sensitizing dyes, an enhancement of photographic speed/graininess relations, an enhancement of sharpness attributed to specific optical properties of tabular grains, and an enhancement of covering power. Generally, in enhancing the photographic speed of silver halide emulsions, it is effective to employ tabular grains of large size and high aspect ratio.
On the other hand, it has been found that, the greater the enhancement of photographic speed, the more serious the problem of photographic performance deterioration by prolonged storage. The problem is especially serious with respect to color negative photographic lightsensitive materials with a photographic speed of ISO 400 or more. The causes of the photographic performance deterioration by prolonged storage involve not only hitherto well-known heat and moisture but also natural radiation (environmental radiation or cosmic rays). The lightsensitive material having been exposed to natural radiation suffers from an increase of fog density and, accompanying the same, a deterioration of graininess. As countermeasures to the deterioration of photographic performance by natural radiation, there are known, for example, the method of reducing the coating amount of silver (JP-A-63-226650 and JP-A-63-226651) and the method of reducing the potassium content of photographic lightsensitive materials (JP-A-2-836). Further, as measures for reducing the radiation fog, there are known the method of adding a mercaptoazole-type dye (JP-A-2-190851), the method of using a compound other than chloroauric acid as a gold sensitizer (JP-A-4-67032, JP-A-4-68337 and JP-A-4-75053), and the method of forming development initiation points on a single plane (for example, JP-A-5-216246). However, the tabular grains of large equivalent circle diameter and small grain thickness tend to suffer from radiation fog, and hence only the measures described in the above patent application specifications do not provide satisfactory countermeasures to the deterioration of photographic performance by natural radiation. Therefore, there is a demand for simultaneously attaining an enhancement of photographic speed and an enhancement of resistance to radiation with respect to these grains.
Moreover, in the above patent application specifications, there is no description relating to the speed at 3×10 9 sec exposure time being lower than the speed at 10
−5
sec exposure time by 30 or more in terms of speed unit, which is a feature of the emulsion which can be used in the silver halide photographic lightsensitive material of the present invention. The photographic performance at 10
−6
sec or less exposure time has not yet been studied partly because the exposure time is in the range not employed in practical photographing and partly because a special exposure device (laser) must be used under ultra-short duration exposure. Further, there is no literature referring to the interrelationship between photographic speed under ultra-short duration exposure and photographic speed under radiation.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to improve the ratio of photographic speed/radiation fog of a silver halide photographic lightsensitive material. More specifically, it is an object of the present invention to provide a silver halide photographic lightsensitive material which realizes a reduction of radiation fog without any significant detriment to the practical photographic speed at usual exposure time ({fraction (1/100)} sec) and the practical reciprocity law (10
−5
to 10 sec exposure).
The inventor has made extensive and intensive studies. As a result, it has first been found that there is a correlation between the photographic speed under 10
−6
sec or less ultra-short duration exposure and the photographic speed under radiation with respect to tabular grains of large equivalent circle diameter and small grain thickness. Further, it has been found that a lightsensitive material improved with respect to the ratio of photographic speed/radiation fog can be obtained by carrying out, for example, not only reducing of the amount of gold used in after-ripening but also reducing of the amount of Ir in silver halide grains, increasing of the surface iodide content of silver halide grains, lowering of the (100) face proportion to grain side faces, etc. to thereby produce an emulsion exhibiting a large reciprocity low failure under ultra-short duration exposure without detriment to the photographic speed under {fraction (1/100)} sec exposure and the reciprocity law under 10
−5
to 10 sec exposure. Accordingly, the present invention provides the following silver halide photographic lightsensitive material.
(1) A silver halide photographic lightsensitive material comprising at least one lightsensitive silver halide emulsion layer on a support, wherein the lightsensitive material exhibits a speed at 3×10
−9
sec exposure time being lower than a speed at 10
−5
sec exposure time by 30 or more in terms of speed unit;
(2) The silver halide photographic lightsensitive material according to item (1) above, wherein the lightsensitive material exhibits a speed at 10
−5
sec exposure time being higher than a speed at 10 sec exposure time by 0 to 60 in terms of speed unit;
(3) The silver halide photographic lightsensitive material according to item (2) above, wherein the lightsensitive material exhibits a speed at 3×10
−9
sec exposure time being lower than a speed at 10
−5
sec exposure time by 50 or more in terms of speed unit;
(4) The silver halide photographic lightsensitive material according to any of items (1) to (3) above, wherein the at least one lightsensitive silver halide emulsion layer comprises an emulsion containing silver halide grains having a variation coefficient of equivalent circle diameter distribution of all the grains which is in a range of 40 to 3%, and 50% or more of the total projected area of all the silver halide grains is occupied by tabular grains of silver iodobromide or silver iodochlorobromide having (111) faces as main planes, the tabular grains having an equivalent circle diameter of 3.0 &mgr;m or more and a thickness of 0.25 &mgr;m or less;
(5) The silver halide photographic lightsensitive material according to item (4) above, wherein the variation coefficient of equivalent circle diameter distribution of the silver halide grains contained in the emulsion is in a range of 25 to 3%;
(6) The silver halide photographic lightsensitive material according to item (4) or (5) above, wherein 50% or more of th
Baxter Janet
Fuji Photo Film Co. , Ltd.
Walke Amanda C.
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