| 摘要 |
The present invention relates to copolyimides of 100-70 mol % of recurring structural units of the formula I and 0-30 mol % of recurring structural units of the formula II <IMAGE> (I) <IMAGE> (II) in which za is a tetravalent aromatic tetracarboxylic acid radical other than that of thioxanthonetetracarboxylic acid, the carboxyl groups thereof in each case being located in pairs in the ortho-position or peri-position relative to one another, and xa is a divalent aromatic diamine radical which, in at least one ortho-position relative to at least one nitrogen atom, carries a hydrocarbon substituent having at least one aliphatic alpha -hydrogen atom or xa is a radical of the formula III <IMAGE> (III) in which Xc is a divalent aromatic diamine radical which, in ortho-position relative to both nitrogen atoms, carries in each case at least one mono-valent hydrocarbon substituent having at least one aliphatic alpha -hydrogen atom, &upbar& n assumes an average value of 1.0 to 2.5, Zb is as defined for Za and Xb is an aliphatic, cycloaliphatic, aromatic or araliphatic diamine radical, excluding a radical of the formula III, with the proviso that the proportion of radicals of the formula III in the formula I is selected such that the quantity of thioxanthonetetracarboxylic acid radicals, relative to the total quantity of tetracarboxylic acid units in the copolyimide, is between 1 and 30 mol %. These copolyimides have a high radiation-sensitivity and can be combined with structurally related polyimides to form photocrosslinkable compositions which can be employed for coating purposes.
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