Thermographic recording element

Details Thermographic recording element Thermographic recording element

1998-04-28

2003-07-01

Chea, Thorl (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Radiation sensitive product

Silver compound sensitizer containing

C430S264000, C430S598000, C430S619000, C503S216000

Reexamination Certificate

active

06586170

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a thermographic recording element and more particularly, to a photothermographic recording element suited for the manufacture of graphic printing plates.
2. Prior Art
Photothermographic materials which are processed by a photothermographic process to form photographic images are disclosed, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075, D. Morgan and B. Shely, “Thermally Processed Silver Systems” in “Imaging Processes and Materials,” Neblette, 8th Ed., Sturge, V. Walworth and A. Shepp Ed., page 2, 1969.
These photothermographic materials generally contain a reducible silver source (e.g., organic silver salt), a catalytic amount of a photocatalyst (e.g., silver halide), a toner for controlling the tone of silver, and a reducing agent, typically dispersed in a binder matrix. Photothermographic materials are stable at room temperature. When they are heated at an elevated temperature (e.g., 80° C. or higher) after exposure, redox reaction takes place between the reducible silver source (functioning as an oxidizing agent) and the reducing agent to form silver. This redox reaction is promoted by the catalysis of a latent image produced by exposure. Silver formed by reaction of the organic silver salt in exposed regions provides black images in contrast to unexposed regions, forming an image.
Such photothermographic materials have been used as microphotographic and radiographic photosensitive materials. However, only a few have been used as a graphic printing photosensitive material because the image quality is poor for the printing purpose as demonstrated by low maximum density (Dmax) and soft gradation.
With the recent advance of lasers and light-emitting diodes, scanners and image setters having an oscillation wavelength of 600 to 800 nm find widespread use. There is a strong desire to have a high contrast photosensitive material which has so high sensitivity and Dmax that it may comply with such output devices. The demand for simple dry processing is also increasing.
U.S. Pat. No. 3,667,958 discloses that a photothermographic element comprising a polyhydroxybenzene combined with a hydroxylamine, reductone or hydrazine has high image quality discrimination and resolution. This combination of reducing agents, however, was found to incur an increase of fog.
U.S. Pat. No. 5,496,695 discloses a heat-developable photothermographic element comprising an organic silver salt, a silver halide, a hindered phenol, and a certain hydrazine derivative. These hydrazine derivatives were found still insufficient to accomplish a maximum ultimate density or ultrahigh contrast.
U.S. Pat. No. 5,545,515 discloses the use of acrylonitriles as the co-developer. The hydrazine compounds used therein fail to achieve a fully satisfactory high contrast while the occurrence of black peppers was ascertained.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermographic recording element having a high sensitivity and high Dmax and free of black peppers. Another object of the present invention is to provide a printing plate-forming photosensitive element which can be processed in a fully dry basis without a need for wet processing and produce images of quality.
According to the invention, there is provided a thermographic recording element having at least one image forming layer. The element contains an organic silver salt, a reducing agent, and at least one of substituted alkene derivatives of the general formulae (1) through (14).
In formulae (1) through (14), W is an electron attractive group, D is an electron donative group, and H is hydrogen. The groups represented by W or D attached to the same carbon atom, taken together, may form a cyclic structure. The compound may assume either a trans or a cis structure when both trans and cis structures are possible with respect to W or D. Two W groups in formula (14) form a cyclic structure.
In one preferred embodiment, the thermographic recording element further contains a hydrazine derivative of the general formula (I).
In formula (I), R
2
is an aliphatic, aromatic or heterocyclic group, R
1
is hydrogen or a block group, G
1
is —CO—, —COCO—, —C(═S)—, —SO
2
—, —SO—, —PO(R
3
)— or iminomethylene group, R
3
is selected from the same range as defined for R
1
and may be different from R
1
, A
1
and A
2
are independently hydrogen, alkylsulfonyl, arylsulfonyl or acyl groups, at least one of A
1
and A
2
is hydrogen, and letter m1 is equal to 0 or 1, with the proviso that R
1
is an aliphatic, aromatic or heterocyclic group when m1 is 0.
In one preferred embodiment, the thermographic recording element further contains a photosensitive silver halide so that the element may be photosensitive. That is, a photothermographic (or photosensitive, heat-developable) recording element is provided.
DETAILED DESCRIPTION OF THE INVENTION
The thermographic (or heat-developable) recording element of the invention has at least one image forming layer and contains an organic silver salt and a reducing agent. Preferably it further contains a photosensitive silver halide whereby the invention constitutes a photo-thermographic (or photosensitive, heat-developable) recording element. According to the feature of the Invention, the element further contains substituted alkene derivatives of the general formulae (1) through (14). The inclusion of such substituted alkene derivatives not only provides the thermographic recording element with a high Dmax, high sensitivity, and fully high contrast, but is also effective for suppressing the occurrence of black peppers.
These advantages are enhanced by further adding a hydrazine derivative of the general formula (I).
Substituted Alkene Derivative
First, the substituted alkene derivatives of the general formulae (1) through (14) are described in detail.
In formulae (1) through (14), W is an electron attractive group, D is an electron donative group, and H is a hydrogen atom. The groups represented by W or D attached to the same carbon atom, taken together, may form a cyclic structure. When both trans and cis structures are possible with respect to W or D, the compound may assume either a trans or a cis structure. Two W groups in formula (14) form a cyclic structure.
In formulae (1) through (14), the electron attractive groups represented by W include halogen atoms, cyano groups, nitro groups, alkenyl groups, alkynyl groups, acyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, alkylsulfonyl groups, arylsulfonyl groups, carbamoyl groups, carbonamide groups, sulfamoyl groups, sulfonamide groups, trifluoromethyl groups, trichloromethyl groups, phosphoryl groups, carboxy groups (or salts thereof), sulfo groups (or salts thereof), heterocyclic groups, imino groups, and phenyl groups having such electron attractive groups as a substituent. These groups may have substituents, examples of which include halogen atoms (e.g., fluorine, chlorine, bromine and iodine atoms), alkyl groups (including aralkyl, cycloalkyl and active methine groups), alkenyl groups, alkynyl groups, aryl groups, heterocyclic groups, quaternized nitrogen atom-containing heterocyclic groups (such as pyridinio), acyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, carbamoyl groups, carboxy groups or salts thereof, sulfonylcarbamoyl groups, acylcarbamoyl groups, sulfamoylcarbamoyl groups, carbazoyl groups, oxalyl groups, oxamoyl groups, cyano groups, thiocarbamoyl groups, hydroxy groups, alkoxy groups (including groups containing recurring ethyleneoxy or propyleneoxy units), aryloxy groups, heterocyclic oxy groups, acyloxy groups, (alkoxy or aryloxy) carbonyloxy groups, carbamoyloxy groups, sulfonyloxy groups, amino groups, (alkyl, aryl or heterocyclic) amino groups, N-substituted nitrogenous heterocyclic groups, acylamino groups, sulfonamide groups, ureido groups, thioureido groups, imide groups, (alkoxy or aryloxy) carbonylamino groups, sulfamoylamino groups, semicarbazide groups, thiosemicarbazide groups, hydrazino groups, quaternary ammonio groups,

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