The authors have developed liquid crystalline retardation films to improve certain aspects of LCD image quality such as viewing angle performance and coloration. We have successfully created several types of optical retardation films using a rod-like liquid crystalline polymer. The resulting liquid crystalline polymer films have several advantages over conventional uni- or biaxially stretched retardation films. Precisely controlled structures such as twisted nematic, homogeneous nematic, hybrid nematic and homeotropic structures can provide ideal compensation of various LCD types, such as STN, TN, ECB, VA and IPS-LCDs. Twisted nematic film effectively prevents coloration of STN-LCDs, which is a critical flaw affecting color representation. Short pitch cholesteric film, which utilizes said rod-like liquid crystalline polymer and is the optical equivalent of a negative C-plate, can expand the viewing angle of VA-LCDs. Hybrid nematic film is quite unique in that the film functions not only as a wave plate but also as a viewing angle compensator for TN and ECB-LCDs. Homeotropic film, which acts as a positive-C plate, greatly improves the viewing angle performance of IPS and CPVA-LCDs. Our homeotropically aligned liquid crystalline film, called “NV film”, is the world’s thinnest retardation film. The thickness of the liquid crystalline layer is a mere 1 micrometer. Homeotropic film can be used to expand the viewing angle not only of LCDs but also OLED displays. And NV film, when used in in combination with a quarter wavelength plate, can expand the viewing angles of the circular polarizers used to prevent reflection in OLED displays.
We have developed liquid crystalline retardation films to improve quality of images of LCDs such as their viewing angle performance and coloration. We have achieved to make many types of optical retardation films by using rod-like liquid crystalline polymer (LCP). The resulting liquid crystalline polyesters film has several advantages over conventional uni- or biaxial stretched retardation film. Optical well-controlled structures such as twisted nematic, hybrid nematic and homeotropic structures could be stabilized for ideal compensation of various LCD modes including TN, STN, ECB, VA and IPS modes. Twisted nematic film is effective to cancel coloration in STN mode that is a fatal drawback for color representation. Hybrid nematic film is quite unique film because the film works not only as a wave plate but also as a viewing angle compensator for TN and ECB modes. By using rod-like LCP, it is also possible to make negative-C plate and positive-C plate. Negative-C plate could be realized by using a short pitch cholesteric alignment and positive-C plate could be realized by using homeotropic alignment. Viewing angle performances of various LCD modes compensated with the LCP films are reported in this study.
We have studied the lasing characteristics from a dye-doped nematic layer sandwiched by two polymeric cholesteric liquid crystal (PCLC) films as photonic band gap materials. The nematic layer possessing birefringence brings about the following remarkable optical characteristics; (1) reflectance in the photonic band gap (PBG) region exceeds 50% due to the retardation effect, being unpredictable from a single CLC film, (2) efficient lasing occurs either at the notch of PBG or at the photonic band edge, (3) the lasing emisions contain both right- and left-circular polarizations, and (4) tunable lasing can be achieved by the reorientation of nematic liquid crystal molecule under the application of an electric field.
We report optical and photoresponsive behavior of nonlinear liquid crystals in two-dimensional (2D) periodic structure. 2D structure made of photoresist and titania is constructed by interference photolithography using grating mask. Then azobenzene-doped nematic liquid crystal is infiltrated into these arrays, and photoresponsive behavior of the azobenzene-doped liquid crystal in the periodic structure is investigated. In particular, we show that the diffraction from these liquid crystal infiltrated grating structures can be optically modulated by an Ar+ laser at 488 nm.