(Photo) thermographic material with a blue background

Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging

Reexamination Certificate

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Details

C430S510000, C430S517000, C430S520000, C430S619000

Reexamination Certificate

active

06376159

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to substantially light-insensitive thermographic and photothermogryhic materials having a background for viewing in transmission images produced therewith and recording processes there for.
BACKGROUND OF THE INVENTION
Thermal imaging or thermography is a recording process wherein images are generated by the use of imagewise modulated thermal energy.
In thermography three approaches are known:
1. Imagewise transfer of an ingredient necessary for the chemical or physical process bringing about changes in colour or optical density to a receptor element containing other of the ingredients necessary for the chemical or physical process followed by uniform heating to bring about the changes in colour or optical density.
2. Thermal dye transfer printing wherein a visible image pattern is formed by transfer of a coloured species from an imagewise heated donor element onto a receptor element.
3. Direct thermal formation of a visible image pattern by imagewise heating of a recording material containing matter that by chemical or physical process changes colour or optical density.
Thermographic materials of type 3 become photothermographic if a photosensitive agent is present 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 Silvers” photographic materials of the 3M Company, which are reviewed by D. A. Morgan in “Handbook of Imaging Sciences”, edited by A. R. Diamond, page 43, published by Marcel Dekker in 1991.
Particular sorts of thermographic film have a blue background, which can vary in tone and optical density, for example, for applications such as the printing of medical images for viewing in transmission. This blue background is not aesthetic having a number of functional purposes, for example: rendering the brownish tone of developed silver images blue/black, preventing over-exposure of the eyes of the viewer upon viewing in transmission with a view-box and improving image sharpness by reducing light scattering. Current practice is to achieve this blue background by incorporating one or more blue pigments or dyes into the support, thereby avoiding possible interference between the pigment or dye necessary to obtain the blue background and the other functional ingredients in the layer structure which makes up a thermographic material. However, this practice requires pigments and dyes which can withstand the high temperatures involved in kneading these dyes and pigments into the polymer (conventionally polyethylene terephthalate), in extruding the polymer to produce the polymer sheet, in stretching the polymer sheet and in conditioning the resulting support to reduce crimp upon later exposure to high temperatures during coating, drying, conditioning and use. Furthermore, this practice also requires the holding of an inventory of different sorts of blue background support as well as substantially colourless supports for producing a complete range of thermographic materials e.g. from graphics applications requiring a substantially colourless support to medical applications requiring a blue background support. The holding of such an inventory of different sorts of blue background support as well as substantially colourless supports incurs financial penalties due to additional storage and logistical requirements as well as increasing the possibility, easy in the subdued lighting required for the coating of photosensitive thermographic products, of using the “wrong” sort of support for the production of a particular thermographic material. This is in addition to possible financial penalties incurred by the possible necessary use of more expensive pigments and dyes in the colouring of the support due to the harsher conditions involved in the incorporation process. There is therefore a necessity for thermographic materials having different blue backgrounds, which can utilize a substantially colourless support.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a substantially light-insensitive thermographic recording material having a blue background which can utilize a substantially colourless support.
It is therefore a further object of the present invention to provide a process for producing a substantially light-insensitive thermographic recording material having a blue background which can utilize a substantially colourless support.
It is therefore another object of the present invention to provide a photothermographic recording material having a blue background which can utilize a substantially colourless support.
It is therefore a still further object of the present invention to provide a process for producing a photothermographic recording material having a blue background which can utilize a substantially colourless support.
Other objects and advantages of the present invention will become clear from the further description and examples.
SUMMARY OF THE INVENTION
According to the present invention a substantially light-insensitive thermographic recording material is provided 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 said thermographic recording material.
According to the present invention a thermographic recording process is also provided comprising the steps of: bringing a substanially light-insensitive thermographic recording material, as referred to above, into the proximity of a heat source; image-wise heating of the thermographic recording material with the heat source; and removing the thermographic recording material from the heat source.
According to the present invention a photothermographic recording material excluding a palladium compound is also provided comprising a substantially colourless support and a photo-addressable thermally developable 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, photosensitive silver halide in catalytic association with the substantially light-insensitive organic silver salt 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 photo-addressable thermally developable element and/or any other layer on either side of the support.
A photothermographic recording process is also provided, according to the present invention, comprising the steps of: bringing a photothermographic recording material, as referred to above, into the proximity of a source of actinic radiation; image-wise exposing the photothermographic recording material with the source of actinic radiation; bringing the image-wise exposed photothermographic recording material into the proximity of a heat source; uniformly heating the image-wise exposed photothermographic recording material; and removing the photothermographic recording material from the heat source.
DETAILED DESCRIPTION OF THE INVENTION
Substantially
By substantially light-insensitive is meant not intentionally light sensitive. By a substantially colourless support is meant that no colouring agent has been intentially added.
Blue Pigments and Dyes
In a preferred embodiment of the substantially light-insensitive thermographic and photothermographic materials, according to the present invention, the blue pigment or dye has an absorption maximum in the wavelength range from 570 to 630

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