We have investigated the formation of polymer walls using a patterned electric field for rugged liquid crystal (LC) displays. The patterned electric field induces patterned phase separation. The LC molecules segregate in the high electric field regions, i.e. pixels, whereas the monomers segregate in the low field regions, i.e. inter-pixels. Subsequent photo-polymerization forms polymer walls between the pixels. We discuss the features of polymer walls formed by using this novel method.