新型聚合物分散液晶相位光栅的制备

Preparation of Novel Polymer Dispersed Liquid Crystal Grating

把具有光敏特性的预聚物与向列相液晶按一定比例混合 ,注入表面经过取向处理的液晶盒中。以紫外灯为光源 ,通过光掩膜法 ,使混合物在光场的引发下发生相分离 ,形成液晶 /聚合物相位光栅。由于相分离后液晶在取向膜的作用下沿液晶盒面方向旋转 180° ,克服了传统液晶光栅器件对入射光偏振方向的依赖 ,提高了光的有效利用率。采用光学显微镜和He Ne激光器进行测试 ,结果表明所制样品具有较好的栅结构 ,其衍射效率不受入射光偏振方向的影响且具有电场可调性。该光栅制作方法简便 ,驱动电压低 ,在光通信器件、衍射光学、投影显示。

Photosensitive pre polymer monomers are mixed together with nematic liquid crystal in certain ratio. Then the mixture is injected into the cells for liquid crystal. The surfaces of the cells are coated with alignment films and rubbed for anti paralleled alignment. Phase separation between liquid crystal and pre polymer monomers takes place when ultraviolet light is applied with the shielding plate covering on the cells, which results in the formation of liquid crystal/polymer phase grating. Since the liquid crystal rotates 180° along the cell surfaces with the effect of alignment films, the disadvantage of traditional liquid crystal grating depending on the polarizing direction of incident light is overcome, and the utilization efficiency of light is improved. The samples are checked up by optical microscope and He Ne laser. The results indicate that the samples have clear grating structure, their diffraction efficiencies do not change with the polarizing directions of the incident lights and can be modulated by electric field. The PDLC gratings with low driving voltage could be fabricated easily. They show numerous potential applications including optical communication devices, diffractive optical elements, projection displays and light valve.