Light sensitive, thermally developable imaging system

DETAILED DESCRIPTION OF THE INVENTION There are a minimum of four components to the imageable systems of the present invention, and five components to the preferred constructions.
The four required ingredients are (1) a bleachabale dye or a leuco dye, (2) a nitrate salt, (3) a light sensitive diazonium salt, and (4) a polymeric resin.
An acidic material constitutes the preferred fifth ingredient.
THE BINDER Any natural or synthetic polymeric binder may be used in the practice of the present invention.
The pH of the resin has been found to affect only the speed of the decolorizing or colorizing effect.
If the speed is not important, any resin may be used.
Organic polymeric resins, preferably thermoplastic resins (although thermoset resins may be used), are generally preferred.
Where speed is more important, either the more acidic resins should be used or an acid should be added to the system to reduce the pH and increase the rate of decolorizing or colorizing (i.
e.
, leuco dye oxidizing).
Such resins as polyvinyl acetals, polyesters, polyvinyl resins, polyvinylpyrolidone, polyesters, polycarbonates, polyamides, polyvinyl butyral, polyacrylates, cellulose esters, copolymers and blends of these classes of resins, and others have been used with particular success.
Natural polymeric materials such as gelatin and gum arabic may also be used.
Where the proportions and activities of dyes and nitrate salt require a particular developing time and temperature, the resin should be able to withstand those conditions.
Generally it is preferred that the polymer not decompose or lose its structural integrity at 200.
degree.
F.
(93.
degree.
C.
) for 30 seconds and most preferred that it not decompose or lose its structural integrity at 260.
degree.
F.
(127.
degree.
C.
) for 30 seconds.
Beyond these minimal requirements, there is no criticality in the selection of a binder.
In fact, even transparency and translucency are not required, although they are desirable.
Where, for example, the polymer is itself an opaque white, the light struck and thermally treated area in decolorizable systems will become white and the non-treated areas will remain the color of the dye