Hidehiro Seki

Dichroic Dyes for Guest-Host Liquid-Crystal Cells

Abstract To clarify the relation between molecular structure and an order parameter of dichroic dyes of the guest-host liquid-crystal cells, the ratio l/d of length l to diameter d of circumscribed cylinders of dichroic dyes is used as a parameter. Experimental results clarify that there exists an obvious correlation between l/d and order parameters of long axes of dye molecules; information is obtained on ordering states of dyes dissolved in a liquid crystal, especially the performance of flexible parts of dye molecules.

Guest-Host Interactions in Liquid Crystals

Abstract The liquid crystal display devices using the guest-host interactions do not require that substrates are optically flat, and have wide viewing angle. Therefore, the authors have studied the dichoric dyes used in these display devices. A part of the results obtained was described in another journal. In this paper, the authors have clarified some dyes available for the guest-host cell. The influence of the thickness of the liquid crystal layer in a cell on color switching and response characteristics have been made clear. If the product of the dye concentration and the cell thick ness is kept constant, the variation of the cell thickness will not change the color switching characteristics. The recovery time is proportional to the square of the cell thickness. By adjusting the dye concentration we can make a thin cell with a good color switching characteristic and with the short recovery time.

A Double-Layer Electrically Controlled Birefringence Liquid-Crystal Display with a Wide-Viewing-Angle Cone

An electrically controlled birefringence (ECB) LCD (liquid crystal display) has the problem of narrow viewing angle. To solve this problem, a double-layer ECB (D-ECB) LCD with a wide-viewing-angle cone under the application of voltage is proposed. In this device, each layer compensates for the variation of retardation as a function of viewing angle. This double-layer optical compensation method can be applied not only to a birefringence mode but also to an absorption mode, i.e. guest-host mode.<<ETX>>

Tilted Homeotropic Alignment of Liquid-Crystal Molecules Using the Rubbing Method

It is well known that slightly tilted homeotropic alignment of liquid-crystal molecules is obtained by oblique evaporation followed by homeotropic treatment. However, this method has disadvantages in obtaining large area uniformity and productivity because of the requirement of large vacuum equipment. In this paper, a new alignment technique of slightly tilted homeotropic alignment using the rubbing method (THR method) is proposed, and its applicability to display devices is discussed.

13.2: Color Imaging and Display System with Field Sequential OCB LCD

In this paper, a tracheal intubation apparatus with the field sequential OCB LCD is proposed. The system uses a new color imaging & display system that enables a high quality and low power display. Object illuminations of three primary colors flash sequentially and synchronize with LCD backlight flashing. Clear moving image and high color purity with wide color gamut are obtained

Light-Stability of Dichroic Guest-Host Cells

Light-stability of liquid crystal color display devices using guest-host interactions were investigated. It was found theoretically as well as experimentally that a decrease of absorbance of the guest-host cell was almost proportional to the exposed light intensity and time while the decrease was not large. Therefore, the lifetime can be calculated by extrapolation from the initial decreasing rate of absorbance obtained from an accelerated life test using an intense light. Various disazo dyes with large dichroic ratios were tested and some stable dyes were found.

A New Reflective Color Guest-Host Display with Scattering Effect

Abstract A bright reflective LCD without a backlight is a key device for portable information systems. This paper proposes a new Guest-Host type liquid-crystal display. It consists of a light control film (LCF), a phase change type Guest-Host (PCGH) liquid-crystal layer and a mirror substrate. The device docs not need a polarizer that absorbs at least half of the incident lights. The structure is simple in comparison to the reflective PCGH LCD with a geometrically controlled reflection mirror. Optimization of the characteristic of LCF in the new device will promise a very bright reflective LCD.

Rubbing Effect on Geometrical Anisotropy of Alignment Surface of Liquid Crystals

Abstract Molecular alignment of liquid-crystal affects on electro-optical characteristics in display device. Rubbing on the alignment surface is most reliable process for obtaining uniform molecular alignment in manufacturing. In this paper, fine structures of the surface of the alignment substrates were observed by atomic force microscope (AFM) and the mechanism of liquid-crystal molecular alignment was investigated. As the results, the rubbing process induces geometrical anisotropy on the substrate in specific condition and has not monotonous dependence of the rubbing condition.

Evaluation of Optical Parameter in Liquid Crystal Layer

ABSTRACT Liquid crystal displays (LCDs) are widely used in many fields for high performance, such as low power consumption, high contrast and high durability. The precise design of electro-optical performance and the controllability of the manufacturing technology in LCDs have progressed. The evaluation technology is indispensable to achieve the demand. Measurement of the retardation is one of the important evaluation technologies. It is closely related to the contrast, the viewing angle, the response speed and so on. A newly developed Senarmont method is proposed. This method gives more precise measurement accuracy and is useful the development of the LCDs performance.

Color Matching of Guest-Host Liquid Crystal Displays

Abstract A bright reflective LCD without a backlight is a key device for portable information systems. The guest-host LCDs use absorption effect of dichroic dyes and have a wide viewing angle cone. So that, complicated designs of optical compensation in birefringence or optical rotatory power modes have no use of the GH-LCDs. Black and white color of the GH-LCDs works as a light shutter of a full color display with micro-color filters and achromatic color must be displayed precisely. Then it is necessary to mix dyes for achromatic display in the GH-LCDs. In this work, the design was carried out with the Newton-Raphson method in order to obtain the optimum dye concentration. As a result, the relationship between the dye concentration and the optical property was clarified. The process gives us a helpful guideline in fabrication of the reflective color LCD and it is expected that the precise color matching improves the quality of GH-LCDs.