Retardation Film Research Articles

59.1: Development of near Zero Optical Retardation Film from Cyclic Block Copolymers

AbstractCyclic block copolymer (CBC) is a fully saturated olefin block copolymer which can be melt cast into films with near zero optical retardation in both film plane and thickness direction. This nearly isotropic CBC film is particularly useful as a polarizer's inner protective layer and can offer a good wide‐viewing performance of IPS‐LCD TVs.

Application of Twisted Retarders to a Cholesteric Liquid Crystal Polarizer for the Control of Output Polarization States

The possibility of applying twisted retarders to a cholesteric liquid crystal polarizer for the control of polarization states has been investigated. In particular, we have focused on the application of twisted retarders to the conversion of circular polarization states into linear polarization states. It has been found that circular polarization states could be converted into arbitrary linear polarization states using twisted retarders. We have fabricated left-handed twisted retarder films using commercially available liquid crystals. Their optical characteristics were experimentally investigated and found to be in good agreement with theoretical expectations.

59.2: Development of New Optical Films for LCDs

AbstractWe have been developing retardation‐controlled polypropylene‐based films with additives. We propose new optical films having Re value (in‐plane retardation) around 100nm, or less 20nm. These films show high durability as optical properties under certain conditions. The low Re value film can be used for protection films of LCD's polarizer, and the high Re value one can be used for retardation films of VA and other modes of LCD.

Optimization of an optical configuration in a vertical alignment liquid crystal cell for wide viewing angle

We propose an optical structure for a vertical alignment (VA) liquid crystal (LC) cell with a wide viewing angle. The proposed LC cell consists of an A-plate and two C-plates for optical compensation. Optical compensation and optimization to eliminate off-axis light leakage in the entire visible wavelength range are performed on a Poincaré sphere using the Stokes vector and the Muller matrix method. After optimizing the wavelength dispersion of the retardation films that are used, we prove that the proposed VA LC cell can improve the viewing angle and contrast ratio by calculating optical characteristics, particularly in diagonal directions.

MHD Effect of Liquid Metal Film Flows as Plasma-Facing Components

Stability of liquid metal film flow under gradient magnetic field is investigated. Three dimensional numerical simulations on magnetohydrodynamics (MHD) effect of free surface film flow were carried out, with emphasis on the film thickness variation and its surface stability. Three different MHD phenomena of film flow were observed in the experiment, namely, retardant, rivulet and flat film flow. From our experiment and numerical simulation it can be concluded that flat film flow is a good choice for plasma-facing components (PFCs)

Single-mode transflective liquid crystal display tailored for wide-band single gamma curve

This paper proposes a single cell gap transflective patterned vertically aligned liquid crystal mode with the same gamma curve for both reflective and transmissive operation. The gamma curve of the proposed transflective mode is obtained by tuning the chevron-type electrode structure in the reflective part to diminish the difference of the optical polarization path on the Poincare sphere, between the transmissive and reflective parts. Wide-band characteristics can be obtained by using in-cell lambda/4 retardation films with different optic axes in the transmissive and reflective parts.

Alignment and Optical Properties of LC Retarder Film Photo-Polymerized at Various Conditions

Investigation of the properties of the liquid crystalline polymer (LCP) retarder films, formed by photo-polymerization of a reactive LC mixture at various conditions, has shown that the alignment, the birefringence and the thermal stability of the LCP film are governed by the conversion of photo-polymerization (CP) of reactive LCs. The CP of the LCP film photo-polymerized in air has increased with the intensity of irradiation light, which reduces both the degree of in-plane alignment of LCs and the birefringence but gives the better thermal stability of the film. The photo-polymerization in an inert environment has induced the higher CP and the better thermal stability of the LCP film than the in-air polymerization.

P‐199: Achromatic Reduction of Off‐Axis Light Leakage in LCDs by Self‐Compensated Phase Retardation (SPR) Film

AbstractWavelength dispersion of refractive indices of compensation films causes the problems of light leakage and color shift at oblique incident angles in the black state of liquid crystal displays. We propose a self‐compensated phase retardation (SPR) film reducing the light leakage stemming from the wavelength dispersion of compensation films. Numerical calculations show that SPR films suppress the leaked light significantly more than the state‐of‐art compensation scheme used in vertical alignment mode liquid crystal displays.

P‐190: Wide‐Band Transflective Liquid Crystal Display in a Patterned Vertically Aligned Mode with a Single Cell Gap

AbstractWe propose optical configuration for wide‐band characteristics in transflective liquid crystal display with a single cell gap at patterned vertically aligned mode. Difference of the optical path between transmissive and reflective parts is compensated by designing the electrode structure and adopting two retardation films which show wide band characteristics calculated from mirror imaging method.

P‐191: Reflective LCD Mode of Twisted Liquid Crystal Designed for Low Voltage Driving

AbstractWe have investigated a reflective type of nematic liquid crystal display (LCD) using 180° twisted state configuration in the π cell which comprises one polarizer and one optical retardation film. This reflective mode has lower driving voltage as well as sufficient gray. Consequently, proposed reflective LC mode could be suitable for low power consumption with excellent optical image by various gray levels.

P‐179: Modeling and Prototyping of Optically Compensated VA LCD

AbstractA new double‐layer thin retardation film developed by Crysoptix provides an efficient optical compensation of vertically aligned LCD. The advantages of Thin Birefringent Film (TBF™) technology enable in‐cell application of the retarder. The VA LC cell prototyping confirms the optical simulation data.

Retardation Films and Their Application to LCDs

Retardation Films and Their Application to LCDs

Wide Viewing Transflective Liquid Crystal Display with a Patterned Electrode

We studied various dynamic characteristics of the transflective liquid crystal display (LCD) having a single cell gap and a single liquid crystal (LC) mode simultaneously. In this configuration, intrinsic optical path difference between transmissive and reflective part was compensated by modifying LC's optic axis with different patterned electrode configurations and voltage application. The angle of electrode was designed to induce appropriate optical retardations in each part and the resultant electro-optic characteristics were matched identically. Also, we minimized the mismatches in grey level by optimizing the angle of reflective part through the simulation. Moreover, the wide viewing characteristics of transflective LCD was verified from the 8-domain LC structure of our sample while only 4-domains can be achieved in the conventional case. By using this technique, we can easily achieve transflective LCD of good performances under same optical setup such as polarizers and retardation films over the whole panel area without complicated fabrication.

Relationship between Molecular Orientation of Rubbed Polyimide Alignment Layer and That of Liquid-Crystalline Polymer Film Coated on the Alignment Layer

The molecular orientation of the coating type of retardation film was investigated. The retardation film was created by photopolymerization of a liquid-crystalline (LC) monomer coated on a rubbed polyimide alignment layer. The relationship between the molecular orientation of a rubbed polyimide film and that of mesogens in a photopolymerized liquid crystal coated on the polyimide film has been investigated using optical measurements. It was found that the inclination angle of the refractive index ellipsoide and the optical retardation of photopolymerized LC films are strongly related to the optical properties of the rubbed polyimide film regardless of the rubbing conditions.

Azodyes as Photoalignment Materials for Polymerizable Liquid Crystals

We demonstrate the excellent photoalignment capability of sulfuric azodyes for polymerizable liquid crystals (PLC) whose anisotropic films are extensively studied as basic elements of many passive optical devices (e.g., retardation films, polarizers, and color filters). These dyes exhibit a high affinity to various substrates and insolubility in PLC and organic solvents commonly used for their dilution. An extremely low exposure dose (less than 50 mJ) is needed to induce an excellent planar alignment of PLC. This alignment can be easily patterned using minimal numbers of masks and exposure steps. No sign of alignment deterioration is observed after photopolymerization. These imply that new photoalignment materials can be effectively used for the industrial production of optical films based on PLC. Particularly, they suit the continuous manufacturing process for such films.

34.5L: Late‐News Paper: Low Cost Retarder‐less Transflective IPS‐LCD

AbstractA transflective IPS‐LCD without retardation films, which degrade transmissive contrast, is developed. This is realized by altering the voltage applied to the transmissive and the reflective region independently. A 2.36‐in. LCD fabricated using this technology attained the reflectance and the reflective contrast of 7.5% and 3.1, respectively, as well as the transmissive characteristics comparable to those of a conventional transmissive IPS‐LCD.

L‐3: Late‐News Paper: Extremely Broadband Retardation Films

AbstractWe disclose here the design and construction of retardation films with any desired dispersion properties by using conventional dispersive uniaxial retardation films. In particular we demonstrate the design of retardation films which have constant retardation over the entire visible spectrum. They also have very large viewing angles.

51.1: Invited Paper: Viewing‐Angle Compensation of TN‐ and ECB‐LCD Modes by Using a Rod‐Like Liquid Crystalline Polymer Film

AbstractWe have developed a liquid crystalline retardation film technology by using a rod‐like liquid crystalline polymer (LCP) for various LCD modes. In particular, considerable improvements in viewing angle performance have been achieved for the Twisted Nematic (TN) and the transmissive/transflective Electrically Controlled Birefringence (ECB) modes by using hybrid aligned nematic film ‘NH Film’.

Retardation‐controlling color filter with two directly stacked retardation layers

Abstract— A polymerizable liquid crystal (PLC), the orientation of which can be frozen, is useful for making retardation layers. In this paper, a new color filter (CF) with retardation‐controlling layers made of PLC is reported. It has a positive A‐plate and a negative C‐plate, both directly stacked on a color‐filter layer. These two retardation layers exhibit good orientation ability, and function well as retarders, even when they are only 1/10 or less as thick as ordinary retardation films. The new CF also has excellent thermal stability. The change in retardation after heat treatment at 200°C for 30 min is around 5%, and there is no observable peeling. A prototype VA‐LCD made with our new CF provides good optical compensation, with the light leakage being extremely low in all azimuthal directions. This technology is very useful for making thin, highly reliable color filters for LCDs, even with other modes.

An IPS‐LCD with a high contrast ratio of over 80:1 at all viewing angles

Abstract— A 32‐in. IPS‐LCD with a significantly wide‐viewing‐angle performance has been developed using a new optical compensation method. It provides a contrast ratio of over 80:1 at all viewing angles, which enhances its color saturation at oblique angles. According to our study, it is important to shorten the path of the optical compensation in the Poincaré sphere. We have found an effective method using two retardation films, one with an Nz value larger than 0.5 and one with a value smaller than 0.5.