Browse Prior Art Database

Liquid Crystal Cell Thickness Measurement

IP.com Disclosure Number: IPCOM000037253D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Takano, H: AUTHOR

Abstract

A filled twisted nematic liquid crystal cell thickness measurement method which make use of retardation measurement is disclosed.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Liquid Crystal Cell Thickness Measurement

A filled twisted nematic liquid crystal cell thickness measurement method which make use of retardation measurement is disclosed.

The retardation is expressed as ((n(e)-n(o)*d, where n(e) and n(o) are refractive indices for extraordinary and ordinary rays, respectively, and d is a thickness of filled liquid crystal cell. Therefore, if we know birefringence (n(e)-n(o) of the filled liquid crystal cell, we can obtain the cell thickness from its retardation. Generally, birefringence is a function of pre-tilt angle, temperature and wavelength. Unfortunately, in the case of twisted nematic liquid crystal cell, it is also a function of cell thickness. The disclosed method solves this problem.

The measurement consists of two steps. Step 1: measure a retardation of a standard filled twisted nematic liquid crystal cell, whose thickness is already known and whose condition is almost the same as those of target liquid crystal cells, and obtain the birefringence of standard cell by dividing the retardation by the cell thickness. Step 2: measure retardations of target cells and obtain target cell thickness by dividing retardation by birefringence which is obtained in Step 1.

1