Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-05-04
2001-12-04
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S607000, C430S567000, C430S569000, C430S966000, C430S967000
Reexamination Certificate
active
06326135
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silver halide radiographic product designed for exposure to high energy ionizing radiation, a new industrial radiographic system, and a method for obtaining an industrial radiographic image. More particularly, it relates to a product for high energy industrial radiography with improved latent image keeping and higher speed.
BACKGROUND
Industrial radiography is a non-destructive method for the inspection and analysis of defects in items made of, for example, glass, paper, wood or metal. This method is widely used in the aeronautical, nuclear and petroleum industries for the detection of defects in welds and texture of materials in aircraft and nuclear reactor parts and in pipe lines.
This method involves exposing a radiographic product containing a silver halide emulsion to high energy ionizing radiation, generally X or &ggr; rays. The sensitivity of the radiographic emulsions to X and &ggr; rays is due to the absorption of part of these rays by the silver halide grains, causing a secondary emission of electrons, and thereby forming an internal latent image. The radiographic product is then developed and fixed.
Unlike medical radiographic films, which are exposed through luminescent screens that re-emit visible light, films for industrial radiography do not need to be sensitive to visible light, and so are generally not color-sensitive. Films for industrial radiography are either exposed directly to ionizing radiation, or exposed through a screen that intensifies the ionizing radiation. These intensifying screens, generally made of metal, increase the proportion of the ionizing radiation that can be absorbed by the silver halide grains.
Products for industrial radiography generally use a silver halide emulsion made mostly of thick grains (cubic or other solid shape) to absorb as much of the ionizing radiation crossing the emulsion layer as possible.
Also known are films for industrial radiography comprising emulsions made of specific tabular grains such as those described, for example, in U.S. Pat. No. 4,883,748 or Patent Application EP 757,286. When a radiographic product comprising tabular grain emulsions is exposed to ionizing radiations the keeping of the latent image is impaired.
SUMMARY OF THE INVENTION
The object of this invention is to provide a new product for industrial radiography in which the keeping of the latent image obtained by exposure to ionizing radiation is improved. Another object of this invention is to provide a radiographic product of improved radiographic sensitivity.
These and other objects are achieved by this invention, which concerns a non-color-sensitive radiographic product designed for exposure to ionizing radiation of energy equal to at least 40 keV containing at least 50 mg/dm
2
of silver, which comprises a support coated on at least one of its sides with a layer of silver halide emulsion in which at least 50% of the grains are tabular grains, and at least 0.05 mmol/mol Ag of a compound of formula
wherein R
1
and R
2
each independently represent an atom of hydrogen, an alkyl group comprising from 1 to 5 atoms of carbon, substituted or not, a hydroxyl group, or a benzyl group, and R
3
and R
4
each independently represent a hydrogen, or alkyl group comprising from 1 to 5 atoms of carbon, or jointly represent the atoms necessary to form a heterocycle of 4 to 6 atoms, substituted or not.
The present invention further concerns a method of formation of an image in an industrial radiography product that involves the exposure of the photographic product to ionizing radiation of energy equal to at least 40 keV to form a latent image, and the subsequent development of the product to form a radiographic image.
DESCRIPTION OF PREFERRED EMBODIMENTS
In an embodiment of the invention, the radiographic product is exposed to radiation in the energy range 40 keV to 20 MeV.
In particular, this new radiographic product unexpectedly shows an improved keeping of the latent image obtained on exposure to ionizing radiation. The product of the invention also shows higher speed on exposure to ionizing radiation of energy greater than or equal to 400 keV.
One or more compounds (I) can be incorporated into the radiographic product of this invention.
Preferably, the quantity of compound (I) incorporated ranges from 0.1 mmol/mol of silver to 0.5 mmol/mol of silver.
In the scope of the invention, R
1
and R
2
can be independently straight-chain or branched-chain alkyl groups. R
1
and R
2
can be methyl, ethyl, propyl, butyl or pentyl groups, preferably methyl. In a specific embodiment, R
1
is a hydrogen atom or a hydroxyl group, and R
2
is an alkyl group, preferably methyl.
R
3
and R
4
can be independently straight-chain or branched-chain alkyl groups. R
3
and R
4
can each independently be, for example, a methyl, ethyl, propyl, butyl or pentyl group. When R
3
and R
4
jointly comprise the atoms necessary to form a heterocycle, that heterocycle can contain a further atom of nitrogen and (or) oxygen. The heterocycle thus obtained can comprise 5 to 6 members, forming, for example, a morpholino, pyrrolidino, piperidino, or piperazino group etc.
Useful compounds (I) in the present invention are, for example:
In the invention, the radiographic product comprises a quantity of silver in the range 50 to 200 mg/dm
2
.
The radiographic product of the invention comprises at least one tabular grain emulsion. “Tabular grains” are defined as grains possessing two parallel sides of greater surface area than the other sides of the grain. These grains are characterized by their aspect ratio (R), which is the ratio of the mean equivalent circular diameter (ECD) to the mean thickness of the grains (e).
In the scope of the invention, the tabular grain emulsion is an emulsion in which at least 50%, and preferably at least 80% of the grains are tabular grains of aspect ratio greater than or equal to 2, preferably in the range 5 to 20.
Such emulsions are, for example, described in
Research Disclosure
September 1996, 591, Section I (referred to hereafter as
Research Disclosure
).
Useful emulsions in the scope of this invention preferably contain silver halide grains made up essentially of silver bromide, i.e., the main silver halide in the grains is silver bromide. The silver halide grains that can be used in the scope of the invention can additionally contain silver iodide or silver chloride. In one embodiment, the grains in the emulsion of the radiographic product of the invention contain at least 90% (mol) silver bromide. These grains can additionally contain a quantity of silver chloride or iodide less than or equal to 10% (mol).
In a preferred embodiment, the silver halide grains in the emulsions for industrial radiography are silver bromo-iodide grains containing a quantity of iodide less than 3% iodide, the iodide being either localized in a part of the silver halide grain volume or spread evenly throughout that volume.
The emulsions in the radiographic product of the present invention comprise silver halide grains dispersed in a binder, conventionally a water-permeable hydrophilic colloid such as gelatin, gelatin derivatives, albumin, a polyvinyl alcohol, vinyl polymers, etc.
These silver halide emulsions can contain dopants such as rhodium, indium, osmium or iridium ions etc. (see Section I-D3 of
Research Disclosure
) generally in small amounts. These dopants are generally incorporated during the making of the emulsion.
The silver halide emulsions can be chemically sensitized using the methods described in section IV of
Research Disclosure
. The chemical sensitizers generally used are compounds of sulfur and(or) selenium and(or) gold.
The silver halide emulsions can also contain, among other substances, optical brighteners, antifoggants, surfactants, plastifiers, lubricants, hardening agents, stabilizers, and absorption and(or) diffusion agents such as those described in Sections II-B, VI, VII, VIII, and IX of
Research Disclosure.
The radiographic product of the invention can comprise, in addition to the silve
Droin Gerard M.
Roussilhe Jacques
Baxter Janet
Eastman Kodak Company
Walke Amanda C.
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