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1 前言 不加电场而通过光化学方法使液晶分子取向发生变化,一般有以下三种途径:1、在液晶中掺入光反应性分子,通过光照引起相变;2、光反应性分子与高分子液晶材料相结合,用线偏振光照射引起再取向;3、通过光化学反应使基板表面的分子结构发生变化,利用这种变化,控制液晶相的取向。本文主要讨论第三种方式。 液晶的开关功能是通过表面作用先均匀取向,然后在电场作用下使取向发生变化而实现的。也就是说,是通过基板表面对液晶分子的取向限制作用和变化的电场实现再取向的。如果基板表面在电场以外的外界作用下,其结构发生变化的话,那么有可能只依靠这个外界的作用实现开关功能。1988年有人提出上述建议,并把对液晶具有光控取向功能的表面称为指令表面（command一surface）。
1 Preface There is the following three ways to change the orientation of liquid crystal molecules by photochemical method without electric field: 1, Including photoreactive molecules in liquid crystal, causing phase change by light; 2, Photoreactive molecules and polymers Liquid crystal material combined with linear polarized light irradiation reorientation; 3, through the photochemical reaction of the substrate surface molecular structure changes, the use of this change, the control of the liquid crystal phase orientation. This article focuses on the third way. Liquid crystal switch function is through the surface of the first uniform orientation, and then under the action of the electric field to change the orientation achieved. That is, reorientation is achieved by the substrate surface restricting the orientation of the liquid crystal molecules and changing the electric field. If the substrate surface in the electric field outside the role of the outside world, its structure changes, then it is possible to rely solely on the role of the outside world to achieve the switching function. The suggestion was made in 1988 and the surface having the function of light-oriented alignment of the liquid crystal is called a command surface.