Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-04-17
2002-05-21
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S510000, C430S517000, C430S522000, C430S531000, C430S944000
Reexamination Certificate
active
06391535
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to thermally developable silver halide photothermographic materials.
BACKGROUND OF THE INVENTION
Thermally developable silver halide photothermographic materials are disclosed in D. Morgan and B. Shely, U.S. Pat. Nos. 3,152,904 and 3,457,075, and D. H. Klisterboer, “Thermally Processed Silver Systems” in Imaging Processes and Materials, Neblette's Eighth Edition, Edited by J. M. Sturge, V. Walworth and A. Shepp, page 2, 1989.
The thermally developable silver halide photothermographic material contains a reducible silver source (such as organic silver salts), a catalytic active amount of a photocatalyst (such as silver halide), a tone modifier controlling silver image tone and a reducing agent, which are usually in the form of being dispersed in organic binder. Silver halide photothermographic materials are stable at ordinary temperatures and when heated at a high temperature (e.g., 80° C. or higher) after exposure, silver is formed through oxidation-reduction reaction between a reducible silver salt (which functions as an oxidizing agent) and a reducing agent. The oxidation-reduction reaction is catalyzed by latent images produced by exposure. Silver formed through reaction of an organic acid silver salt in exposed areas provides black-and-white images, which are in contrast to non-exposed areas. In the field of medical diagnostic and printing, advancements in the technique for processing are directed toward simplification, rapid access and friendliness to earth.
There is a system in this direction, including exposure to infrared laser (having wavelengths of 750 nm or more) and thermal processing. To obtain images with higher sharpness in this system, infrared dyes exhibiting absorption suited for infrared lasers are needed to prevent halation or irradiation. When a photosensitive layer is exposed to infrared rays, a part of the infrared rays which do not contribute to image formation penetrate to the support without being absorbed, is reflected thereon and returns to the image forming region, deteriorating sharpness of images. It is therefore necessary to absorb or shield as much as possible the infrared rays not contributing to image formation.
An antihalation layer to prevent halation is conventionally provided in any of the component layers of the photothermographic material, except for a sub-coating layer, specifically as a backing layer. However, it is impossible to completely prevent halation thereby. U.S. Pat. Nos. 4,581,323 and 4,312,941 disclose such a layer to prevent composite reflection of light scattered between layers internal to the photosensitive component. U.S. Pat. Nos. 4,477,562 and 4,409,316 disclose a peelable antihalation layer by the use of carbon black. In this method, however, the peelable layer makes difficult adhesion thereto during the stage of coating, converting or packaging and also produces colored scrap sheets. Therefore, these techniques are not desirable methods to solve the problems described above.
After being subjected to exposure and thermal processing, the photothermographic material sometimes produces nonuniformity due to interference fringes. It is contemplated that this nonuniformity due to interference fringes originates before formation of the images, i.e., at the stage of preparing the photothermographic material and its influence is displayed at the time of exposure. It is therefore desired to solve such problems.
U.S. Pat. No. 4,581,325 and European Patent 377,961 disclose photothermographic material containing polymethine and nonpolar dyes to prevent infrared halation. These dyes exhibit not only superior infrared absorptivity but also visible light absorptivity in the subsequent exposure.
JP-A 7-191432 (hereinafter, the term, JP-A means an unexamined and published Japanese Patent Application) discloses incorporation of water-soluble polymethine dyes in a hydrophilic layer of a silver halide photothermographic material. U.S. Pat. No. 5,496,695 and Tokuhyohei 9-509503 discloses squarylium dyes exhibiting no absorption in the visible region; and JP-A 7-191432 and 9-230531 disclose infrared absorbing polymethine dyes.
To solve problems described above, such as deterioration in Image sharpness and uneven density due to interference fringes produced when silver halide photothermographic materials are exposed to infrared rays to form images, the following techniques were disclosed.
The use of the squarylium dyes and polymethine dyes described above was found to be effective to some extents to prevent halation. However, incorporation of the dyes into an antihalation layer or a photosensitive layer thickens fine image portions, easily deteriorating sharpness.
JP-B 6-10735 and JP-A 8-211521 discloses methods for improving interference fringes. However, satisfactory results were not obtained. Further, it was found that when infrared absorbing compounds such as infrared dyes were used in the backing layer, remarkable interference fringes were often observed.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide silver halide photothermographic materials exhibiting antihalation effects, superior sharpness and with no uneven density due to interference fringes.
The object of the present invention can be accomplished by the following constitution:
1. A silver halide photothermographic material comprising on a support an organic silver salt and a silver halide, wherein the support has thereon a sublayer containing an infrared absorbing compound exhibiting an absorption maximum at a wavelength of 700 to 900 nm;
2. The photothermographic material described in 1., wherein the infrared absorbing compound is a water-soluble infrared absorbing compound, a compound represented by formula (I), a compound represented by formula (II), a copper-containing phosphate compound or metal oxide particles:
formula (I)
wherein Z
1
and Z
2
are each a nonmetallic atom group necessary to complete a 5- or 6-membered nitrogen-containing ring; R
1
and R
2
are each an alkyl group, an alkenyl group, or an aralkyl group; L is a linkage group, in which 5, 7 or 9 methine groups are linked with each other through conjugated double bonds; a, b and c are each 0 or 1; and X
−
is an anion;
formula (II)
wherein R
1
, R
4
, R
5
and R
8
are each a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl or aralkyl group; R
2
, R
3
, R
6
and R
7
are each a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an aryl group. a heterocyclic group or an aralkyl group, —CH
2
OR, in which R is an alkylacyl group, —C(═O)R′, —SiR″R′″R″″ or —SO
2
R′″″, in which R′, R″, R′″, R″″ and R′″″ are each an alkyl group, or R
1
and R
2
, R
3
and R
4
, R
5
and R
6
, R
7
and R
8
, or R
2
and R
3
, or R
6
and R
7
combine together with each other to form a 5-, 6- or 7-membered ring; R
9
and R
10
are each a univalent group; and n is an integer of 1 to 3;
3. The photothermographic material described in 1., wherein the infrared absorbing compound is a water-soluble infrared absorbing compound;
4. The photothermographic material described in 1., wherein the infrared absorbing compound is a compound represented by formula (I):
formula (I)
wherein Z
1
and Z
2
are each a nonmetallic atom group necessary to complete a 5- or 6-membered nitrogen-containing ring; R
1
and R
2
are each an alkyl group, an alkenyl group, or an aralkyl group; L is a linkage group, in which 5, 7 or 9 methine groups are linked with each other through conjugated double bonds; a, b and c are each 0 or 1; and X
−
is an anion;
5. The photothermographic material described in 1., wherein the infrared absorbing compound is a compound represented by formula (II):
formula (II)
wherein R
1
, R
4
, R
5
and R
8
are each a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl or aralkyl group; R
2
, R
3
, R
6
and R
7
are each a hydrogen atom, an
Arimoto Tadashi
Sasaki Takayuki
Cantor & Colburn LLP
Chea Thorl
Konica Corporation
LandOfFree
Silver halide photothermograhic 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 photothermograhic material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silver halide photothermograhic material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2915118