High performance TAC film for LCDs

Abstract

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.

Structure and application of polarizer film for thin-film-transistor liquid crystal displays

“…TAC film is widely used as a protective and supporting film for the PVA layer by virtue of high light transmittance (>93%), low birefringence, high moisture resistance, high thermal-stability, high uniformity and good curling ability [23][24][25][26]. The chemical structure of the TAC is shown in Fig.…”

Orientation Birefringence Regulation for the Binary Blend Film of Cellulose Triacetate and Rigid-Rod-Like 5CB Molecules

“…Alternatively, solution casting is usually used for the preparation of CTA optical films in industrial production. 4 However, the viscosity of solutions containing 15% or more of CTA is extremely high. Moreover, the used solvent (dichloromethane) is highly volatile.…”

“…12,13 Therefore, the regulation of the orientation birefringence of optical films has been investigated intensely. 3,4,9,10,14,15 It has been reported that the orientation birefringence (Δn) of a polymer is determined together by the segmental polarizability and the orientation degree (f) 15−17 Here, Δn 0 denotes the intrinsic birefringence of a polymer. n ̅ , ρ, M and N A are the average refractive index, the density, the relative molecular mass, and the Avogadro's constant, respectively.…”

“…With the rapid development of liquid crystal display (LCD) technology over the past two decades, , great efforts have been paid for studying one of the key components of LCD, that is, optical films to improve the display performance . Among various kinds of optical films, cellulose triacetate (CTA) film is widely used as the polarizer protective film and the optical compensation film because of its excellent transparency and heat resistance. − As a matter of course, as an optical film, the control of optical retardation of CTA film is essential to make it suitable for multiple application modes . For instance, CTA films are expected to have zero retardation when used as polarizer protective films, while they should have appropriate retardations for the application of optical compensation films. , Meanwhile, with the ever-increasing demands of thinner display panels, thinner CTA films are desired .…”

“…For instance, CTA films are expected to have zero retardation when used as polarizer protective films, while they should have appropriate retardations for the application of optical compensation films. , Meanwhile, with the ever-increasing demands of thinner display panels, thinner CTA films are desired . However, as the intrinsic birefringence of cellulose esters themselves are very small, a thinner thickness would narrow the adjustable scope of optical retardation. , Therefore, the regulation of the orientation birefringence of optical films has been investigated intensely. ,,,,, …”