High performance TAC film for LCDs

Tri-acetyl cellulose (TAC) films are widely used as a protective film for polarizers because it has high light transmittance, low birefringence, high moisture permeability, high uniformity and good curling property. This paper describes TAC film technologies, especially about the birefringence control of TAC film. Making use of the controlled birefringence, the TAC film comes to take an active role in optical compensation of LCDs as well as protection of polarizers. The out-of-plane birefringence of the TAC film can be controlled by additives, and the in-plane birefringence can be controlled by stretching. Coating a discotic material on the TAC film gives an additional optical compensation layer. With these technologies, we were able to develop an optical compensation film called WV film, which remarkably improves the viewing angle characteristics for TN-LCDs. Recently, we have developed and commercialized a new WV film for the OCB mode. OCB is known to have a very fast optical response time and promising as a next generation LCD-TV. The OCB-WV film has realized excellent viewing angle characteristics for OCB as well as a high on-axis contrast ratio. TAC film technologies open up possibilities of developing various types of optical compensation films suited for all LCD modes.