A Nod Optical Measurement Method for the Determination of LC Pretilt Angle without a Restriction of Pretilt Magnitude and a Cell Gap of LC

Abstract

To measure a pretilt angle in liquid crystal cells, a crystal rotation method is commonly used because of its advantages such as high precision, short measurement time and small measurement area The method, however, has the restrictions on measurable pretilt rang and available cell thickness; pretilt in the range of about 16–60 degrees cannot be measured and the cell thickness should be larger than about 1μm. We developed a new pretilt measurement method without the restrictions of cell condition. In our new method, a pretilt angle is determined from a specific polarization direction of incident light, for which either ordinary or extraordinary wave is excited inside the cell. This method permits us to easily and accurately measure the pretilt angle in full range of 0–90 degrees.

Key Words:

• liquid crystal
• pretilt angle
• measurement method
• optical measurement
• crystal- rotation method