Photothermographic material

Details Photothermographic material Photothermographic material

2000-05-24

2001-10-02

Chea, Thorl (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Radiation sensitive product

Silver compound sensitizer containing

C430S617000, C430S531000

Reexamination Certificate

active

06297002

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a photothermographic material and in particular to such that for medical diagnosis.
RELATED ART
In recent years, a strong need for reducing the waste of processing solution has arisen in medical diagnosis field from the viewpoints of environmental preservation and space saving. Thus desired is a technology related to a photothermographic material for medical diagnosis allowing efficient light exposure with a laser imager, and capable of providing a clear black image with a high resolution and sharpness. Such photothermographic material can provide the customer with a heat-developing and processing system without solution-base processing chemicals, allowing easy handling and exerting no impact on the environment.
While a similar need has arisen in the field of general image forming materials, images used in the medical diagnosis field specifically require a high image quality such as excellent sharpness and graininess for fine depiction, and prefer a blue-black tone for facilitating diagnoses. Although various hard copy system using pigment or dye, exemplified as an inkjet printer and electronic photograph system, are prevailing as a general image forming system, none of which is satisfactory as an output system for medical diagnosis images.
Other type of photothermographic recording system using an organic silver salt is known, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and “Thermally Processed Silver Systems—A” by D. Klosterboer, Imaging Processes and Materials, Neblette's 8thed., edited by Sturge, V. Walworth and A. Shepp, Chapter 9, p.279, (1989). Among these, the photothermographic material generally has a photosensitive layer comprising a catalytic amount of photocatalyst (e.g., silver halide), reducing agent, reducible silver salt (e.g., organic silver salt), and an optional toning agent for controlling tone of silver image, all of which being dispersed in a binder matrix. The photothermographic material produces black silver image when heated, after light exposure, to a high temperature (e.g. 80° C. or above) through redox reaction of the silver halide or reducible silver salt (acts as an oxidizing agent) with the reducing agent. The redox reaction is promoted by a catalytic action of latent image generated by the exposure, so that the monotone silver image is formed in the exposed area, as is disclosed in a number of literatures including U.S. Pat. No. 2,910,377 and JP-B-43-4924 (the code “JP-B” as used herein means an “examined Japanese Patent Publication”), and can achieve a quality and tone satisfiable for medical diagnosis use.
It has, however, been desired to further improve such photothermographic material since the material still fails in obtaining a visibility sufficient for medical diagnosis as described above, in particular for lung field diagnosis. It is therefore an object of the present invention to provide a photothermographic material suitable for medical diagnosis, in particular for lung field diagnosis.
DESCRIPTION OF THE INVENTION
The present inventors found after extensive investigations for solving the above problems that a photothermographic material exhibiting a desirable effect can be obtained if an optical density of an image obtainable after the light exposure and development satisfies a certain condition, and if a polymer latex contained in the photosensitive layer has a molar ratio of ammonium ion/sodium ion within a range from 0 to 20, which led us to provide the present invention.
According to a first aspect of the present invention, provided is a photothermographic material containing on one side of a support a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ion and a binder, characterized in that an image obtainable after the light exposure and development satisfies a condition expressed as below:
0≦&Dgr;BG
0.5
−&Dgr;BG
2.5
<0.15
(where, &Dgr;BG
0.5
represents a value obtained by subtracting 0.5 from an optical density observed through a B filter of an image portion giving an optical density of 0.5 observed through a G filter, and &Dgr;BG
2.5
represents a value obtained by subtracting 2.5 from an optical density observed through a B filter of an image portion giving an optical density of 2.5 observed through a G filter.)
According to a second aspect of the present invention, provided is a photothermographic material having on one side of a support a photosensitive layer comprising a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ion and a binder, characterized in that the photosensitive layer is formed using a coating liquid containing a latex in an amount of 50 wt % or more of the total binder contained therein, the latex having a molar ratio of ammonium ion/sodium ion within a range from 0 to 20.
In the photothermographic material of the second aspect of the present invention, it is preferable that the polymer latex has an equilibrium moisture content of 2 wt % or less at 25° C. and relative humidity (RH) of 60%, that the photothermographic material contains an organic dicarboxylic acid, and that an image obtainable after the light exposure and development satisfies a condition expressed as below:
0≦&Dgr;BG
0.5
−&Dgr;BG
2.5
<0.15
(where, &Dgr;BG
0.5
represents a value obtained by subtracting 0.5 from an optical density observed through a B filter of an image portion giving an optical density of 0.5 observed through a G filter, and &Dgr;BG
2.5
represents a value obtained by subtracting 2.5 from an optical density observed through a B filter of an image portion giving an optical density of 2.5 observed through a G filter.)


REFERENCES:
patent: 5922529 (1999-07-01), Tsuzuki et al.

Affiliated with

Also associated with

Rating

Photothermographic 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 Photothermographic material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photothermographic material will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2609699