For a photo-degradable polymeric alignment layer (CBDA-ODA polyimide), the better LC alignment is obtained by LPUV irradiation of it with 5∼10 times less dosage than that inducing the maximum anisotropy of it. This LC alignment is improved by cleaning of the LPUV-irradiated alignment layer with water and/or IPA. It has turned out that the wet cleaning process removes the fragments or by-products formed by photo-decomposition of the polyimide and thus makes its surface more stable. This effect of the post-UV cleaning results in improvement of the LC alignment and the LC cell's properties.