The property of the unidirectional out-of-plane tilt angle in a nematic liquid crystal is investigated in view of van-der-Waals interaction between nematic liquid crystal molecules and three layers: the anisotropic polyimide layer, the isotropic polyimide layer, and the substrate layer. Dependence of the pretilt angle on the total thickness of the polyimide layer and the thickness of the anisotropic layer oriented by rubbing is estimated from experiment and theory. Our results show that the screening factor increases with the increase of the thickness of the isotropic layer. (c) 2006 Wiley Periodicals, Inc.