Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-09-05
2002-07-02
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S510000, C430S517000, C430S583000, C430S584000, C430S591000, C430S944000
Reexamination Certificate
active
06413711
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to thermally developable photothermographic materials, and in particular to a photothermographic material exhibiting improved silver image tone and superior image sharpness, reduced deterioration in storage stability, reduced residual dye staining, reduced fogging, and improvements in reduction of sensitivity and in raw stock stability.
BACKGROUND OF THE INVENTION
As is well known, when photographic materials are exposed, incident light is reflected or refracted by silver halide, additives or by the interface of a layer, resulting in blurred images and leading to deterioration in sharpness. To prevent these drawbacks are employed so-called anti-halation dyes (AH dyes) or anti-irradiation dyes (AI dyes). Performance which has been required for the AH dyes and AI dyes is having an absorption within the intended wavelengths, no unwanted influence on a silver halide emulsion and no residual color after processing a photographic material by being completely decolorized or leached out during processing.
As a result of the recent tendency of rapid access or dry processing, a dry processing system completely free of water is often employed, in which thermally developable photothermographic materials are used in a laser imager for medical diagnostic use or an image setter for graphic arts use, having an oscillation wavelength within 600 to 800 nm. A problem of residual color stains caused by dyes remaining in the photographic material after being processed arises, which is different from residual color occurring in conventional silver halide photographic materials.
Thermally developable photothermographic materials are disclosed in, for example, D. Morgan and B. Shely “Dry Silver Photographic Material”, in U.S. Pat. Nos. 3,152,904 and 3,457,075; and in D. H. Klosterboer “Thermally Processed Silver Systems” (Imaging Processes and Materials) Neblette, 8th Edition, edited by Sturge, V. Walworth, and A. Shepp, page 279, 1989), etc. The photothermographic material comprises an organic silver salt, a catalytically active amount of photo-catalyst (e.g., silver halide) and a reducing agent, which are contained in the form of a dispersion in an (organic) binder matrix. The photothermographic material forms silver through an oxidation-reduction reaction between a reducible silver source (functioning as an oxidant) and a reducing agent when exposed and heated at a high temperature (e.g., 80° C. or higher). In this case, the oxidation-reduction reaction is promoted by catalytic action of the latent image produced by exposure to light, leading to image formation, based on such exposure.
Since no water is used in processing, no dye leaches out of the photothermographic material, which produces problems in absorption in the visible region, caused by residual dyes, and for which an improvement is desired.
Representative examples of infrared absorbing AI and AH dyes are organic dyes and there have been proposed a large number of compounds, as AI and AH dyes. Specifically, cyanine dyes and oxonol dyes are often used. However, these dyes exhibit a relatively large absorption in the visible region and their degradation product, which results in an yellow absorption, are disadvantageous in terms of residual color stains, having further defects that the compounds are not only unstable and liable to decompose, but also relatively high in cost.
Some squarylium dyes are known to exhibit infrared absorption, as disclosed in JP-A 10-36695, 10-104779 and 10-158253 (hereinafterm the term JP-A refers to an unexamined, published Japanese Patent Application). JP-A 2-216140 and JP-A 10-24654 propose the use of infrared squaryliun dyes as AI and AH dyes in photothermographic materials and silver halide photographic materials. However, dyes described in JP-A 10-24654 are not suitable in spectral absorption characteristics and have an absorption in the visible region, producing the disadvantage that the photographic material is colored. Even when incorporated in the form of a solid particle dispersion, the visible absorption is still large and satisfied performance was not displayed.
To overcome such disadvantages, squarylium dyes advantageously applicable to photothermographic material to prevent deterioration in sharpness are disclosed in U.S. Pat. No. 4,508. Of these, specifically, a squarylium dye having a thiopyrylium nucleu, a squarylium dye having a pyrylium nucleus, or pyrylium croconium dye and thiopyrylium croconium dye which are similar to the squarylium dye exhibit a small absorption in the visible region, having characteristics suited to AH and AI dyes.
In cases when these squarylium dye and croconium dye are applied, as a AH or AI dye, to photothermographic materials, and specifically when used in combination with commonly known infrared sensitizing dyes, it was proved that desensitization, increased fogging or deterioration in storage stability occurred, and therefore it is important to overcome such problems.
As a result of the inventor's study of infrared sensitizing dyes used in combination with a squarylium dye, it was found that a photothermographic material exhibiting lower fogging and higher sensitivity was obtained by the use of an infrared sensitizing dye having a specific structure, thereby leading to improvements in storage stability of the photothermographic material.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a photothermographic material exhibiting superior image sharpness and raw stock stability, used for a laser imager, and also a photothermographic material exhibiting high contrast, lower fogging and higher sensitivity and superior raw stock stability, used for image setter output films.
The object of the invention can be accomplished by the following constitution:
1. A photothermographic material comprising a support, a layer containing an organic silver salt, a photosensitive silver halide and a binder, wherein a layer constituting the photothermographic material or the support contains a dye represented by the following formula (1), and the photosensitive silver halide being spectrally sensitized with at least a sensitizing dye represented by the following formulas (2a) through (2d):
wherein Q represents
x represents and oxygen or
X represents an oxygen or sulfur atom; R
1
and R
2
each represent a univalent substituent group; m and n are each 0, 1, 2, 3 or 4;
wherein Y
1
, Y
2
and Y
11
each represent an oxygen atom, sulfur atom, selenium atom or —CH═CH—; L
1
through L
9
and L
11
through L
15
each represent a methine group; R
1
, R
2
, R
11
and R
12
each represents an aliphatic group; R
3
, R
4
, R
13
and R
14
each represent an alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group or a heterocyclic ring group; W
1
, W
2
, W
3
, W
4
, W
11
, W
12
, W
13
, and W
14
each represent a hydrogen atom or a substituent group, or a non-metallic atom group necessary to form a condensed ring by bonding between W
1
and W
2
, W
3
and W
4
, W
11
and W
12
, or W
13
and W
14
, or a non-metallic atom group necessary to form a 5- or 6-membered condensed ring by bonding between R
3
and W
1
, R
3
and W
2
, R
13
and W
11
, R
13
and W
12
, R
4
and W
3
, R
4
and W
4
, R
14
and W
13
, or R
14
and W
14
; X
1
and X
11
each represent an ion necessary to compensate for an intramolecular charge; k1 and k11 represent the number necessary to compensate for an intramolecular charge; m1 is 0 or 1; n1, n2, n11 and n12 are each 0, 1 or 2, provided that n1 and n2, or n11 and n12 are 0 at the same time;
2. An image forming method, wherein the photothermographic material described in 1 is exposed to an infrared laser light;
3. The image forming method described in 2, wherein the photothermographic material is exposed with a laser scanning exposure apparatus, in which the laser light and the exposed surface of the photothermographic material are not substantially at right angles to each other;
4. The image forming method described in 2, wherein the photothermographic mater
Bierman, Muserlian and Lucas
Chea Thorl
Konica Corporation
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