Patterned polyimide film, a photosensitive polyamide acid derivative and an electrophoretic image-display cell

A method of forming a patterned polyimide film on a substrate, which patterned polyimide film is provided with an electrically conductive layer at its surface facing away from the substrate, said method comprising:

• (a) providing said substrate with a layer of a negative-acting photosensitive polyamide acid derivative which is obtained by reacting polyamide acid with at least one compound of the formula 1 ##STR12## in which R.sub.1 and R.sub.2 both independently represent a lower alkyl group of 1-4 carbon atoms or a hydrogen atom,
• R is an alkylene group of 1-5 carbon atoms,
• X is an oxygen atom or the group --N(R.sub.3)--, in which R.sub.3 is a hydrogen atom or a lower alkyl group of 1-4 carbon atoms, and m has the value 0 or 1, on the condition that in at least one compound that is used the value of m is 1;
• (b) applying a layer of a photosensitive photoresist on said layer of photosensitive polyamide derivative;
• (c) exposing the resultant assembly patternwise;
• (d) developing the resultant patternwise exposed photoresist layer to remove the exposed portions of said photoresist layer;
• (e) applying to the remaining portions of said photoresist layer and to the exposed portions of said layer of the polyamide derivative an electrically conductive layer;
• (f) removing, by means of a lift-off process, the remaining portions of said photoresist layer and the overlying portions of said electrically conductive layer;
• and
• (g) subjecting portions of said polyamide derivative remaining on said substrate to a heat treatment and imidization to form a polyimide.