| 摘要 |
A colored, positive-acting, radiation-sensitive composition whose color is extinguished or greatly decreased in intensity upon irradiation comprising at least one acid-free resin, at least one component which upon irradiation yields acidic and/or free radical products, at least one acid and/or free radical sensitive dyestuff and at least one positive-acting component; positive-acting elements comprising suitable support materials at least one surface of which has been coated with the above composition and lithographic printing plates comprising the above elements, wherein the support materials are lithographically suitable support materials, whch have been imagewise exposed to radiation whereby there is a high contrast, before development, between the colored image areas and less intensely colored or colorless non-image areas, the image areas of said plates being additionally highly stable against aqueous alkaline developers after development to remove the exposed non-image areas of the composition and more highly colored than the non-image areas of the revealed substrate surface.
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