Liquid crystals (LCs) represent thermodynamically stable phases situated conceptually between an ordinary isotropic liquid and a crystalline solid. Due to a fact that LCs possess simultaneously the optical anisotropy of crystals and the fluidity of liquid, they showmany exclusive properties (optical, electrical, andmagnetic) and alignment changes by external fields at surfaces and interfaces [1]. Control of theLC alignment is the most important technology in most devices using LCs as active media. Especially, alignment of nematic LCs can be easily changed and controlled by weak external fields. It is suggested that cooperative motion of LCs may be most advantageous in changing the alignment of LC molecules by external stimuli. If a small portion of LC molecules change their alignment in response to an external stimulus, the other LC molecules also change their alignment. This means that only a small amount of energy is needed to change the alignment of whole LC molecules: such a small amount of energy as to induce an alignment change of only 1 mol% of LC molecules is enough to bring about the alignment change of the whole system [2].According to this principle, photomanipulation of the LC alignment has also been reported for polymer films containing photochromic molecules such as azobenzenes, in which a small amount of azobenzene molecules change their shape by light and then the cooperative change

of LC alignment takes place [2]. Photoalignment of LCs has attracted much attention due to its high light sensitivity and large change in refractive index. The effects of structure and density of azobenzene molecules on the photoalignment have been explored systematically [3].