Yukito Saitoh

Ion beam alignment for liquid crystal display fabrication

The ability to align liquid crystals to a substrate is a critical step in the liquid crystal display (LCD) manufacturing process with the industry standard technique employing a mechanical rubbing technique to accomplish this function. However, mechanical rubbing can result in debris generation contaminating not only the substrate being processed but also the clean room housing the equipment. As such, post-cleaning of the display panels is required to remove the debris from the surface in addition to the physical isolation of the mechanical rubbing equipment within the clean room environment introducing considerable time and expense. In addition, uneven wear of the mechanical roller during the rubbing process may result in localized defects that will not be observed until final inspection of a completely assembled display. We have developed and introduced into LCD manufacturing a non-contact alignment technique utilizing both diamond-like carbon (DLC) and a low energy ion beam (IB). The replacement of the polyimide alignment layer with DLC results in a completely dry processing technique for both the thin film deposition and alignment steps.

Optically Compensated In-Plane-Switching-Mode TFT-LCD Panel

An optically compensated in-plane-switching-mode TFT-LCD panel was developed. The panel has an optical compensation film between a liquid crystal layer and a polarizer, and shows a significantly high-contrast viewing angle, good gray-scale capability, small color shift, and a large tolerance for cell gap non-uniformity compared with a conventional in-plane-switching-mode LCD.

An Improved Azimuthal Anchoring Energy Measurement Method Using Liquid Crystals with Different Chiralities.

An improved method for measuring the azimuthal anchoring energy of liquid crystals has been developed. Without knowing the easy axes of the cells precisely, it is possible to measure their anchoring energy precisely, using the same liquid crystals but with different chiralities for the divided cells. The principles and measurements are discussed.

56.1: Novel LC Alignment Method using Diamond Like Carbon Film and Ion Beam Alignment

A novel LC alignment method has been developed. In this, the conventional polyimide film and cloth rubbing have been replaced by a diamond-like-carbon film and an ion beam respectively. The novel method has been used in pilot-line manufacturing to produce super high quality panels: 15″ TN mode and 22″ IPS mode. These panels will be demonstrated, and the advantage of new method will be discussed.

8.1: Quarter Wave Retardation Film for Improving Viewing Angle Properties in Time‐Sequential Stereoscopic 3D Liquid Crystal Displays

We investigated how to achieve desired optical properties of quarter wave retardation films QWFs that increase the viewing angle of time-sequential stereoscopic 3D liquid crystal displays LCDs, such as high luminance, low crosstalk, low color change, and low head-tilt-angle dependency. These display properties were strongly affected by the out-of plane retardation Rth of the QWF. We developed QWFs whose in-plane and out-of-plane retardation are independently controllable by adjustment of a polymerized discotic material layer and a triacetate cellulose film, and 3D-LCDs with high viewing angle properties were realized using these QWFs whose Rth was nearly zero.

New Approach to Enhance Contrast Ratio at Normal Incidence by Controlling the Retardation of Optical Compensation Film in Vertically Aligned Liquid Crystal Displays

We found that the light leakage at normal incidence of a vertically aligned liquid crystal display (VA-LCD) in black state is strongly affected by the polarization states of obliquely incident light. Experimental results were explained by a light scattering model of substrates on both sides of a liquid crystal layer. Applying this model, we found that the contrast ratio at normal incidence can be highly enhanced by controlling the retardation value of retardation films. This is a new, effective approach to enhancement of the contrast ratio in LCDs, different from the conventional approach of simply decreasing the depolarization of the scattering media.

55.1: Development of Low Haze VA Compensation TAC Film and Proposal of Compensation Film Arrangement for Improving CR in VA Panel

We developed a low-haze VA compensation TAC film for high contrast ratio VA-LCDs, by reducing micro anisotropic nonuniform structure inside the stretched TAC film. Moreover, we found that the arrangement of our low-haze VA compensation TAC film as a single compensator on the front side of VA-LCDs with color filter on TFT arrays realizes more than 10 % higher on-axis contrast ratio than that of conventional compensation films as double compensator.

Stability of UV-Type Two-Domain Wide-Viewing-Angle Liquid Crystal Display

We calculated the Gibbs free energy for the splayed-twist state, the reversed-twist state, and the reversed-tilt state of UV-type two-domain wide-viewing-angle thin film transistor liquid crystal display (TFT-LCD) panels to evaluate the stability of the three configurations. We show that the smaller tilt angle is the dominant fact on that influences the stability of the splayed-twisted state. Further more, at high applied voltage, the reversed-tilt state is the most unstable, and is easily deformed into the reversed-twist state. Methods are therefore proposed for reducing the reversed-tilt state area. General trends of the critical voltage as a function of the chiral pitch, twist angle, cell gap, dielectric constant, and elastic constant are also discussed.

55.2: Reduction of Light Leakage by Optical Compensation Film in VA‐LCDs

We investigated a light leakage at normal incidence of a vertically aligned liquid crystal display (VA-LCD) at black state. The light leakage was strongly affected by the polarization states of light obliquely incident on the cell. Experimental results were explained by a light scattering model of substrates on both sides of liquid crystal layer. Applying this result, we showed the light leakage can be highly reduced by controlling the retardation value of optical compensation film between the cell and a backlight unit.

5.2: New Technique of Measuring of the Jones Matrix for a Polarization Medium at Oblique Light Incidence

We propose a new technique of measuring the Jones matrix for a polarization medium (ex. optical compensation film) based on ellipsometry experimental methodology at oblique light incidence. Unlike uniaxial, biaxial, and N-stacked birefringent layer models, this technique describes the mediums polarization properties directly without any assumptions about the internal microscopic physical parameters. The obtained Jones matrix gives an accurate prediction of viewing angle properties of the liquid crystal displays.