Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-04-12
2002-05-28
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S264000, C430S617000
Reexamination Certificate
active
06395466
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a so-called heat-developable image recording material capable of producing image through development by heating without an aid of developing solution.
BACKGROUND OF THE INVENTION
Heat-developable image recording materials capable of producing an image by heat development are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and “Imaging Processes and Materials”, Neblette's 8th ed., page 279-291, (1969). The image recording materials disclosed in these literatures contain a reducible non-photosensitive silver source (e.g., organic silver salt), a catalytic amount of photocatalyst (e.g., silver halide), a color toner for controlling color tone of silver image, and a reducing agent for silver, all of which are usually dispersed in an organic binder matrix. While the heat-developable image recording materials are stable at room temperature, they produce blackened silver when heated, after light exposure, to a high temperature (e.g., 120° C.) through redox reaction between the reducible silver source and the reducing agent. This reaction is promoted by a catalystic action of latent image generated by the exposure.
In another mode of the embodiment without using a catalytic amount of silver halide, a blackened image is also obtainable by image-wise tracing using a thermal head at high temperatures.
Such image recording materials are increasingly attracting attention as those to be combined with, for example, a laser beam drawing apparatus, since an image forming process using such materials requires no processing liquid such as developing solution but only heating, and therefore generates neither sulfurous acid gas nor ammonia gas. The laser beam drawing apparatus is utilized in medical, printing plate making, industrial and many other fields.
In general, a temperature of 110° C. or above and a heating period of 10 to 60 seconds are required to develop these heat-developable image recording materials.
Keeping pace with advances in the laser beam drawing apparatus, the output speed has been increasing, which requires improvements in sensitivity and development speed of the recording material. In recent years, a material based on infectious development by an ultrahigh contrast agent is under investigation as a heat-developable image recording material for printing plate making. More faster speed of the development is, however, desired since the development period thereof tends to become longer due to the principle of infectious development. Raising the development temperature for increasing the development speed will generally result in increased fog, so that the development temperature is limitative. It is thus needed a heat-developable image recording material allowing a high development speed within a temperature range less causative of increased fog.
Gradation hardeners for producing high-contrast image ever known include acylhydrazine derivatives disclosed in U.S. Pat. No. 3,464,738, , No. 5,512,411, No. 5,496,695 and No. 5,536,622; acrylonitrile derivatives disclosed in U.S. Pat. Nos. 5,545,515 and 5,635,339; malondialdehydes disclosed in U.S. Pat. No. 5,654,130; and isoxazoles disclosed in U.S. Pat. No. 5,705,324. Known compounds for accelerating development include amine compounds disclosed in U.S. Pat. No. 5,545,505; hydroxamic acids disclosed in U.S. Pat. No. 5,545,507; and hydrogen atom donors disclosed in U.S. Pat. No. 5,637,449.
It is, however, still insufficient to meet a desired high level of the development speed.
Another problem relates to a large dependence on the heat development temperature and difficulty in obtaining an uniform image due to non-uniform temperature distribution in a heat developing apparatus. Although the temperature distribution is required to be kept within ±1° C., and preferably ±0.5° C., it is practice difficult to meet the requirement on the commercial basis.
In particular, use of an ultrahigh contrast agent for obtaining an ultrahigh contract image tends to increase the temperature dependence, so that a technique for reducing such dependence on the heat development temperature has been desired.
SUMMARY OF THE INVENTION
It is therefore as object of the present invention to provide an improved heat-developable image recording material, in particular a high contrast heat-developable image recording material, and more specifically a heat-developable image recording material allowing a rapid development process and yielding an uniform and stable image formation.
The above object was achieved by the present invention described below:
(1) A heat-developable image recording material containing an organic silver salt, a reducing agent and an organic binder characterized in that the reducing agent comprises a combination of two or more different kinds of reductive compounds exhibiting superadditivity;
(2) The heat-developable image recording material as described in the above (1) wherein either one of the superadditive reductive compound constituting the combination is a hindered phenol compound and the other is a substituted sulfonamidephenol compound;
(3) The heat-developable image recording material as described in the above (2) wherein the hindered phenol compound is contained within a range from 1×10
−2
to 10 mol per one mol of silver, and the sulfonamidophenol compound is a range from 1×10
−4
to 1×10
−1
mol per one mol of silver;
(4) The heat-developable image recording material as described in any one of the above (1) to (3), wherein a ratio of the substituted sulfonamidophenol compound to the hindered phenol compound is within a range from 0.1 to 50 mol %.
(5) The heat-developable image recording material as described in the above (4), wherein a ratio of the substituted sulfonamidophenol compound to the hindered phenol compound is within a range from 0.5 to 20 mol %.
(6) The heat-developable image recording material as described in any one of the above (1) to (5), wherein the substituted sulfonamidophenol compound is represented by the following formula (1):
in the above formula, X
01
and X
02
independently represent a hydrogen atom; halogen atom, or substituent which is bound to the benzene ring via a carbon atom, oxygen atom, nitrogen atom, or sulfur atom; at least either of which being a sulfonamido group; R
01
, R
02
and R
03
independently represent a hydrogen atom; halogen atom, or substituent which is bound to the benzene ring via a carbon atom, oxygen atom, nitrogen atom, or sulfur atom; these substiuents may be taken together with the adjacent ones or with a benzene ring to form a cyclic structure; and at least one of X
01
, X
02
, R
01
, R
02
and R
03
is such substituent.
(7) The heat-developable image recording material as described n the above (6), wherein R
01
is not a hydrogen atom.
(8) The heat-developable image recording material as claimed in the above (6) or (7), wherein the substituted sulfonamidophenol compound is represented by the following formula (3):
in the above formula, R
01
to R
04
independently represent a hydrogen atom; halogen atom, or substituent which is bound to the benzene ring via a carbon atom, oxygen atom, nitrogen atom, or sulfur atom; these substituents may be taken together with the adjacent ones or with a benzene ring to form a cyclic structure; and Z
3
represents an aliphatic, aromatic or heterocyclic group,
(9) The heat-developable image recording material as described in any one of the above (1) to (8) wherein a photosensitive silver halide grain is contained; and
(10) The heat-developable image recording material as described in any one of the above (1) to (9) wherein an ultrahigh contrast agent is contained.
The heat-developable image recording material of the present invention allows rapid processing, has a small dependence on heat-development temperature, has a small lability against non-uniform temperature distribution in the developing apparatus, and can stably yield at uniform image. It is in particular desirable for printing plate making sin
Katoh Kazunobu
Sakai Minoru
LandOfFree
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