광분해법을 이용한 액정 배향 및 광배향 TN-LCD의 전기광학 특성

Electro-optical characteristics of photo-aligned TN-LCD and LC alignment by using photo-depolymerization method

The generation of pretilt angle in nematic liquid crystal (NLC) and electro-optical (EO) characteristics of photo-aligned twisted nematic (TN)-LCD with oblique P-polarized ultraviolet (UV) light irradiation on the two kinds of the soluble polyimide (PI) surfaces containing trifluoromethyl moieties were investigated. The generated pretilt angle of NLC is about 2.5$^{\circ}$with P-polarized UV light irradiation of 20$^{\circ}$on PI-3 surface at 20 min.; However pretilt angle of about 0.5$^{\circ}$are observed on PI-1 and PI-2 surfaces. The generated pretilt angle of NLC on PI-3 surface may be attributed to the trifluoromethyl moieties attached to the lateral benzene rings. The voltage-transmittance and response time characteristics of photo-aligned TN-LCD with P-polarized UV light irradiation of 20$^{\circ}$on PI-1 surface at 20 min were almost same in comparison with the rubbing-aligned TN-LCD. However, the high threshold voltage and slow response are observed on PI-3 surface. Also, the decay time $\tau$$\sub$d/ of photo-aligned TN-LCD is attributed to the anchoring energy of NLC.