Recording medium of improved stability

Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making

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430296, 430327, 430905, 430906, 4273855, 4284111, G03C 172

Patent

active

050028529

DESCRIPTION:

BRIEF SUMMARY
In one aspect this invention relates to a processless recording media comprising polyacetylenic crystals having improved properties.
In another aspect the invention relates to a process for preparing an imageable polyacetylenic solution prior to dispersion in a binder and coating on a film base for imaging by ionizing radiation.


BACKGROUND OF THE INVENTION

It is known that imaging layers suitable for coating on a substrate are prepared by dispersing a solution of an imageable polyacetylenic compound in a binder material and coating such dispersions on a polyester film base. In normal use, the unexposed portion of the film is not removed and is subject to development by prolonged exposure to visible light. For example, several weeks of exposure to the lighting intensity of a normal office environment or daylight can cause the background or unexposed portions of the imageable layer to turn blue. Such exposure to visible light causes degradation of the transmitted pattern by diminishing contrast between the imaged and background, or non-imaged, portions of the film.
Because the crystal size of commercially available, normally crystalline polyacetylenic compounds is often relatively large and of varying dimension and since for imageable coatings, a microcrystalline size between about 0.01 and about 5 micrometers is desirable, the commercial polyacetylenic compound is usually dissolved in a solvent from which it can be subsequently recrystallized as fine discrete crystals of more uniform microcrystalline size. An ester such as ethyl acetate is generally selected for forming the solution of the polyacetylenic compound which is subsequently dispersed as crystals in an aqueous binder solution suitable for coating on a film base. However, films prepared by this method lack the desired resistance to visible light radiation.
Accordingly, it is an object of this invention to overcome the above disadvantages by a process which is economical and commercially feasible.
Another object of this invention is to prepare an imageable polyacetylenic dispersion of improved stability with respect to visible radiation.
Another object is to provide an imageable polyacetylenic dispersion of increased sensitivity to ionizing radiation.
These and other objects of this invention will become apparent from the following description and disclosure.


THE INVENTION

According to this invention an imageable, normally crystalline polyacetylenic compound is dissolved in n-butanol to provide a solution containing a weight ratio of polyacetylene to alcohol of between about 4:1 and about 0.1:1; preferably between about 2:1 and about 1:2. To assure complete solution, the crystalline polyacetylene is desirably added with agitation over a period of from about 30 to about 90 minutes at a temperature of between about 20.degree. C. and about 75.degree. C. depending upon the polyacetylene selected. The resulting solution is then optionally filtered to remove any undissolved crystals. Preferred conditions for solubilizing the crystalline polyacetylenic compound include a temperature of from about 45.degree. C. to about 60.degree. C. under atmospheric pressure followed by filtration.
The n-butanol solvent of this invention employed for dissolution of the present polyacetylenic compounds is unique in its ability to increase resistance of polyacetylenic crystals to light exposure while providing clear, colorless dispersions when added to an aqueous binder solution. Tests with secondary butanol and many other solvents have failed to provide this improvement Additionally n-butanol possesses the ideal degree of water miscibility (9 cc in 100 g. H.sub.2 O at 15.degree. C.), solubilizing properties to give fine particle uniform dispersions of the polyacetylenes, a boiling point which permits easy separation from the polyacetylene dispersions and facility in transferring the polyacetylene from solution into the aqueous binder solution. Lower alcohols are too soluble in water to provide easy separation from aqueous gelatin. On the other hand, the higher alcoho

REFERENCES:
patent: 3844791 (1974-10-01), Bloom
patent: 4734355 (1988-03-01), Lewis

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