Black and white thermographic recording material with...

Details Black and white thermographic recording material with... Black and white thermographic recording material with...

1999-11-23

2001-09-04

Chea, Thorl (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Thermographic process

Heat applied after imaging

C430S517000, C430S519000, C430S520000, C430S521000, C430S619000

Reexamination Certificate

active

06284442

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to thermographic recording materials with improved diagnostic capability.
BACKGROUND OF THE INVENTION
Thermal imaging or thermography is a recording process wherein images are generated by the use of thermal energy. In direct thermal thermography a visible image pattern is formed by image-wise heating of a recording material containing matter that by chemical or physical process changes colour or optical density. Such recording materials become photothermographic upon incorporating a photosensitive agent which after exposure to UV, visible or IR light is capable of catalyzing or participating in a thermographic process bringing about changes in colour or optical density.
Examples of photothermographic materials are the so called “Dry Silver” photothermographic materials of the 3M Company, which are reviewed by D. A. Morgan in “Handbook of Imaging Science”, edited by A. R. Diamond, page 43, published by Marcel Dekker in 1991.
EP-A 889 355 discloses a thermographic recording material comprising a substantially colourless support and a thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent for the substantially light-insensitive organic silver salt in thermal working relationship therewith and a binder, characterized in that a blue pigment or dye having an absorption maximum in the wavelength range from 550 to 700 nm is present in the thermosensitive element and/or any other layer on either side of the support which provides a background for viewing in transmission images produced with the thermographic recording material.
U.S. Pat. No. 5,783,380 discloses a thermally processable imaging element comprising: (1) a support; (2) a thermographic or photothermographic imaging layer on one side of the support; (3) a protective layer overlying the image-forming layer; said protective layer comprising: (A) a film forming binder; (B) a dye dispersed throughout said protective layer in an amount sufficient to impart a pre-selected color thereto; and (C) matte particles the color of the protective layer. No disclosure is made in U.S. Pat. No. 5,783,380 regarding colorant in the support.
EP-A 919 864 discloses a photothermographic element comprising at least one photosensitive layer on a support, wherein the support contains a dye of structure I:
wherein M is a multi-valent metal atom; each of R
1
, R
4
, R
5
, R
8
, R
9
, R
12
R
10
, and R
16
independently represent a hydrogen atom, or a substituted or unsubstituted, branched or unbranched alkyl group; each of R
2
, R
3
, R
6
, R
7
, R
10
, R
11
, and R
14
and R
15
independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted, branched or unbranched alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxygroup; or one cr more of the adjacent pairs R
1
and R
2
, R
2
and R
3
, R
3
and R
4
, R
5
and R
6
, R
6
and R
7
, R
7
and R
8
, R
8
and R
9
, R
9
and R
10
, R
10
and R
11
, R
11
and R
12
, R
13
and R
14
, R
14
and R
15
and R
15
and R
16
taken together may represent the atoms necessary to form a substituted or unsubstituted aromatic or heteroaromatic ring; and wherein the support has a peak absorption between about 660 nm and about 800 nm.
Imaging materials for medical applications are in general produced using a support with a particular blue pigment e.g. MACROLEX™ BLUE 3R from BAYER. The colour of such supports can be defined in terms of L*, a* and b* CIELAB-values which are determined by spectrophotometric measurements according to ASTM Norm E179-90 in a R(45/0) geometry with evaluation according to ASTM Norm E308-90. Representative supports used for medical imaging materials have CIELAB-a* values and -b* values given in the table below.
a*
b*
Dvis
MEDICAL IMAGING MATERIAL SUPPORT 1
−7  
−13.82
0.172
MEDICAL IMAGING MATERIAL SUPPORT 2
−7.22
−13.02
0.174
MEDICAL IMAGING MATERIAL SUPPORT 3
−6.86
−14.46
0.181
MEDICAL IMAGING MATERIAL SUPPORT 4
−7.92
−16.62
0.195
However, the background colour and the colour of an image is a combination of the colour of the support and the colour of the image background and the image of the particular material upon printing. In the case of conventional silver halide images the CIELAB-a* and -b* values of the image are virtually independent of image density, whereas this is not the case for thermographic recording materials based on organic silver salts and reducing agents.
The resolution of medical images, such as X-ray images, is of supreme importance in ensuring reliable diagnosis. It is desirable to improve further the diagnostic reliability of images produced with thermographic recording materials based on organic silver salts and reducing agents using a support with a particular blue pigment, whether produced by thermography or photothermography, thereby ensuring more reliable diagnosis.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide substantially light-insensitive black and white thermographic recording materials whose prints enable more reliable diagnosis.
It is therefore a second object of the present invention to provide black and white photothermographic recording materials whose prints enable more reliable diagnosis.
Further objects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
It has been surprisingly found that the use of a blue-pigmented support such as used for conventional silver halide X-ray films does not provide an image with optimum diagnostic reliability, but that incorporation of at least two colorants which are not antihalation dyes one of which is in the support and the other is in the support or in any layer making up the thermographic recording material, while ensuring that the blue background necessary for preventing over-exposure of the eyes of the viewer upon viewing in transmission with a view-box and reducing light scattering is maintained, an image with improved diagnostic capability.
The above mentioned objects are realized by a substantially light-insensitive black and white monosheet thermographic recording material having a spectrophotometrically determined maximum absorption for visible light between 570 and 650 nm and comprising a support and a thermosensitive element, said thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, wherein the substantially light-insensitive black and white monosheet thermographic recording material contains at least two colorants with maximum absorption at a wavelength between 450 nm and 700 nm; none of the at least two colorants is an antihalation dye; and at least one of the at least two colorants is incorporated in the support.
A black and white monosheet photothermographic recording material is also provided according to the present invention having a spectrophotometrically determined maximum absorption for visible light between 570 and 650 nm and comprising a support and a photo-addressable thermally developable element, said photo-addressable thermally developable element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith, photosensitive silver halide in catalytic association with the substantially light-insensitive organic silver salt and a binder, wherein the black and white monosheet photothermographic recording material contains at least two colorants with maximum absorptions at a wavelength between 450 nm and 700 nm; at least one of the at least two colorants is incorporated in the support; and none of the at least two colorants has a maximum absorption at a wavelength within 30 nm of the wavelength at which maximum spectral sensitivity of the photothermographic recording material is observed.
A thermographic recor

Affiliated with

Also associated with

Rating

Black and white thermographic recording material with... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Black and white thermographic recording material with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Black and white thermographic recording material with... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2537060