Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-09-24
2003-02-25
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
Reexamination Certificate
active
06524783
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-294852, filed Sep. 27, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to, in particular, a silver halide photographic lightsensitive material whose deterioration of photographic properties due to radiation is alleviated.
2. Description of the Related Art
Recently, requirements of photographic lightsensitive materials, in particular, of image-taking photosensitive material have become stricter and stricter. In addition to high sensitivity, it is required to further reduce the graininess deterioration due to radiation exposure, and an improved emulsion to be used for the photographic material is required.
There is a technique of including tabular silver halide grains (hereinafter referred to as “tabular grains”) in order to achieve a highly sensitive silver halide emulsion. A method of manufacturing and a technique of using tabular grains are disclosed in U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306, and 4,459,353, and Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as “JP-A-”) 59-99433 and JP-A-62-209445. Known advantages of tabular grains are an enhancement of sensitivity, including improvements in the color sensitizing efficiency by sensitizing dyes, improvements in the sensitivity/graininess relationship, improvements in the sharpness due to specific optical characteristics of tabular grains, and improvements in the covering power, etc. Generally, in order to improve the sensitivity of a silver halide emulsion, it is effective to use tabular grains of a large size and a high aspect ratio.
In the meantime, it has been gradually found that deterioration of photographic properties due to long-term storage of photographs is increased as sensitivity is improved more and more. In particular, it is a great problem in a color negative photographic lightsensitive material of ISO 400 or more. Deterioration of photographic properties due to long-term storage is caused by natural radiation (environmental radioactivity and cosmic rays), in addition to heat and moisture that are conventionally well known. The photosensitive materials exposed to natural radiation give raise to increment in fog density and deterioration of graininess. As measures against such deteriorations in photographic properties due to natural radiation, a method of reducing the application amount of silver (JP-A's-63-226650 and 63-226651), and a method of reducing the potassium content in a photographic lightsensitive material (JP-A-2-836), etc. are known. In addition, as a method of reducing fog from radiation, disclosed are a method of adding methylocyan dyes (JP-A-2-190851), a method of using a compound other than chloroauric acid as a gold sensitizer (JP-A's-4-67032, 4-68337 and 4-75053), and a method of forming development initiating points on the same plane (JP-A-5-216246). However, these documents only refer to techniques for improving the sensitivity and reducing the fog due to radiation, and do not clearly refer to a method of improving granularity which deteriorates due to radiation.
It was considered that the cause of deterioration of graininess due to radiation was the generation of locally high-density portions after development, because a plurality of grains are exposed by one photon of radiation. However, recently a cause other than the above has been clarified. It is reported that a plurality of development initiating points per grain are formed by irradiation of radiation. In such a case, when development is performed, only areas having the grains having a plurality of development initiating points per grain are developed early, and high-density portions locally appear. The greater the grain size of silver halide is, the more this effect is likely to occur (P. Broadhead., Imaging. Sci. J. 46. 107 (1998)). However, the above information only clarifies a phenomenon caused by radiation, and does not disclose at all a method of reducing the effects of radiation on granularity. As other measures for reducing the effects of radiation on granularity, there are a method of performing sufficient development (GB 2313673A), and a method of applying a physical pressure to a photosensitive material after application (WO00/38011). However, these methods are complicated and have problems for practical use. Further, these patents do not describe improvement of a reduction in the effects of radiation on granularity, by using the emulsion of the present invention.
Generally, it has been considered that the distribution of development initiating points in the case of performing exposure by light conforms to a Poisson distribution. Supposing that the ratio of grains having development initiating points of number x is P(x), P(x) is expressed by the following formula using the mean value n of development initiating points per grain.
P
(
x
)=(
e
−n
×n
x
)/
x!
However, it was not clear whether P(x) actually conforms to the above formula, and what distribution P(x) has in the case of performing exposure by radiation.
BRIEF SUMMARY OF THE INVENTION
The inventors of the present invention have examined representative photographic lightsensitive materials. Thereby they have revealed that, in the case of performing exposure by light, the distribution of development initiating points conforms to a Poisson distribution, or is more concentrated than a Poisson distribution. Further, they have also revealed that, in the case of performing exposure by radiation, the distribution of development initiating points does not conform to a Poisson distribution, and the distribution is more dispersed than a Poisson distribution. Specifically, it was revealed that when enough light to expose 50-55% (number ratio) of the grains to have at least one respective development initiating point is applied, the ratio of the number of silver halide grains having two or more development initiating points per grain to the silver halide grains having at least one development initiating point of all the photographic lightsensitive materials that the present inventors measured, was less than 35%. In the meantime, when enough radiation to expose 50-55% (number ratio) of the grains to have at least one respective development initiating point is irradiated, the ratio of the number of silver halide grains having two or more development initiating points per grain to the silver halide grains having at least one development initiating point of all the photographic lightsensitive materials that the present inventors measured was, 45% or more. As described above, in the case of performing exposure by radiation, the number of development initiating points per grain is greater than that in the case of performing exposure by light, which causes the problem of deterioration of graininess.
An object of the present invention is to provide a photographic lightsensitive material whose granularity deterioration due to radiation is alleviated, and whose sensitivity/radiation fog ratio is improved.
As a result of diligent research, the inventor of the present invention has found that, an emulsion containing a smaller number of grains having a plurality of development initiating points per grain when irradiated, can be obtained by, for example, introducing a dislocation line inside the grains, adding a metal ion or metal complex inside the grains, or applying pressure inside the grains with a dissolver, into tabular grains each having a large grain size and a large aspect ratio. And the use of such an emulsion in a photosensitive material can alleviate granularity deterioration due to radiation and decrease sensitivity to radiation.
The above object has been achieved by the following items (1)-(7).
(1) A silver halide photographic lightsensitive material having at least one lightsensitive silver halide emulsion layer on a support, wherein at l
LandOfFree
Silver halide photographic lightsensitive material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silver halide photographic lightsensitive material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silver halide photographic lightsensitive material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3130573