Yuzuru Tsuchiya

Deformable mirror using the PMN electrostrictor

A simple deformable bimorphous mirror using the PMN electrostrictor has been made for refocusing a light beam. Parabolic deformation of the mirror has been measured by an interferometric technique on a cycle with rising and falling electric fields. In comparison with the hard PZT piezostrictor, the electrostrictor is found to be promising for practical mirror control applications because of a large strain with neither hysteresis nor aging effects.

Approximate Formulas for a Low-Q Electromechanical Resonator and Their Applications to Electrostrictive PMN-Based Ceramics

A new approximate method for calculating the electromechanical coupling factors (kp and k31) related to transverse vibration in piezoelectric ceramics is proposed, which is applicable to a wide range of coupling factors with a considerable mechanical loss. The induced-piezoelectric resonance was measured by the transmission method on PMN-based electrostrictive resonators under an applied bias field. The electromechanical parameters were determined by using the new approximation in the temperature range -100°C to 100°C under fields up to 12×105 V/m. The electrostrictive Q31 coefficient obtained is -5.5×10-3 m4C-2 for PMN, which is in good agreement with that determined by other methods.

Thick polymer-stabilized liquid crystal films for microwave phase control

This article describes the use of thick polymer-stabilized liquid crystal films in a new design for microwave variable phase shifters. A fine μm-order sized polymer network was formed in a 100-μm-thick liquid crystal film, using a photopolymerization-induced phase-separation method to stabilize the molecular alignment of the liquid crystal. Measurement of the electro-optic properties of the liquid crystal film revealed that the relaxation response time of the liquid crystal alignment was drastically decreased by doping the polymer at a concentration of several wt %. A new variable phase shifter composed of a microstrip transmission line (length: 193 mm, width: 200 μm) was also fabricated by using the liquid crystal film as the dielectric material. This device exhibited a microwave phase shift of −80° at a frequency of 20 GHz, when a drive voltage of 70 Vrms was applied vertically to the liquid crystal film.

Electroluminescence of SrS Thin Films Activated with Nd3+, Sm3+, Dy3+, Ho3+, and Er3+ Ions

Thin electroluminescent SrS films activated with Nd3+, Sm3+, Dy3+, Ho3+, and Er3+ ions have been investigated. Their emission colors are found to be orange-white, orange, yellow, greenish white and green respectively, originating from transitions within the 4fn configuration of the rare-earth ions. The luminance levels of these devices are all over 200 cd/m2, except for that of SrS:Ho3+ (110 cd/m2), on the application of a driving voltage in the range 70–100 V with a frequency in the range 3 k–5 kHz. The main spectral regions of these spectra are found to shift to shorter wavelengths in comparison with those of the same ions in ZnS-based TFEL devices.

Fluorinated Polymer Alignment Layers Formed at Low Temperature for Plastic-Substrate-Based Liquid Crystal Devices

In this paper, we describe an alignment layer of chemically and mechanically stable fluorinated polymer for light-weight flexible liquid crystal display devices. Since the fluorinated polymer can be formed on plastic substrates at room temperature, unlike conventional polyimide, thermal distortion of the substrate does not occur. Uniform 70-nm-thick polymer thin films were obtained by spin-coating using a hydrofluoroether solvent. The orientation of the liquid crystal molecules was perpendicular to the rubbing direction of the fluorinated polymer, and the anchoring strength of the rubbed polymer was approximately 10-4 N/m. Twisted nematic liquid crystal devices using plastic substrates coated with the polymer showed good spatial uniformity and a high contrast ratio of more than 100:1.

White-emitting thin-film electroluminescence devices with SrS phosphor doubly activated with rare-earth ions

Thin-film electroluminescence (TFEL) devices with SrS-based phosphor layers have been investigated to obtain white emissions by mixing emissions of two different rare-earth activators, and new white-emitting phosphor layers, except for SrS:Pr, Ce, have been developed. SrS:Sm, Ce and SrS:Nd, Ho phosphor layers show white El-emissions, whose color coordinates correspond to points in the white area on the CIE chromaticity diagram. The EL emissions of SrS:Pr, Ce, SrS:Nd, Ce, and SrS:Ho, Ce phosphor layers are not found in the white area, but are close to the area. Luminance of the emissions, for devices driven with a sinusoidal voltage of 5 kHz, are 200–750 cd/m2, The three primary colors, red, green and blue, can be extracted from the emission of all these devices with color filters. Relative intensities of the three extracted colors are evaluated.

Free-Standing Polymer-Stabilized Ferroelectric Liquid Crystal Film: Chemical Study of Phase Separation

Abstract This paper describes a chemical study of a new free-standing ferroelectric liquid crystal film containing a rigid fiber network polymer formed by photopolymerization-induced phase separation. The liquid crystal and acrylate polymer separated from a homogeneous solution were individually dissolved by different solvents, and examined by high-performance liquid chromatography and gel permeation chromatography, respectively. The liquid crystal component segregated from the solution including 20wt% monomer had a purity of more than 96%, and contained less than 3% of decomposition products and a little remaining monomer, less than 0.3%. The measured molecular weight of the segregated polymer exhibited a broad distribution from 103 to 106 with a mean polymerization degree of about 100, which increased with monomer concentration. Such a free-standing composite film containing a rigid polymer network is applicable to a shock-resistant ferroelectric liquid crystal display panel because the transparent substrates are supported by the composite film.

Polymer-stabilized ferroelectric liquid crystal for flexible displays using plastic substrates

We have developed a ferroelectric liquid crystal device with a novel structure containing a polymer fiber network for flexible lightweight displays using thin plastic substrates. The aligned polymer fibers of sub-micrometers -diameter were formed under ultraviolet light irradiation in a heated nematic- phase solution consisting of liquid crystal and monofunctional acrylate monomer. The rigid polymer network was found to adhere to the two plastic substrates, and the uniform liquid crystal alignment provided a contrast ratio of 100:1 for a monomer concentration of 20 wt%. This device achieves a continuous grayscale capability as a result of change in the spatial distribution of small liquid crystal domains, and also exhibits a fast response time of 80 microsecond(s) due to high-purity separation of polymer and liquid crystal materials. It therefore has attractive features for flexible moving-image display applications.

Dielectric and Electromechanical Properties of PbTiO3-La(Zn2/3Nb1/3)O3 Solid Solution Ceramics

Solid solutions in the PbTiO3-La(Zn2/3Nb1/3)O3 system are formed with a perovskite structure up to 70 mol% of La(Zn2/3Nb1/3)O3 content. Dielectric and electromechanical properties of the ceramics have been measured as functions of temperature. The ferroelectric Curie temperature decreases linearly with increasing La(Zn2/3Nb1/3)O3 content. The planar coupling factor kp at room temperature shows a maximum of 23% in the composition with 13 mol% of La(Zn2/3Nb1/3)O3. A minimum of the temperature coefficient of the planar resonance frequency |Δf/fΔT| at room temperature (~3.7×10-5 K-1) is obtained at 10.5 mol% of La(Zn2/3Nb1/3)O3. By adding a small amount of MnO2 to the ceramics, the order of magnitude of |Δf/fΔT| can be reduced to ~10-6 K-1.

Video-Sensing Effects with Liquid Crystal Neutral-Density Filter.

A variable neutral-density filter using guest-host liquid crystal devices was fabricated for color video image sensing. The liquid crystal devices contain black dichroic dyes whose absorption is controlled by voltage applied to the device . The filter keeps the spectral balance of transmitted light almost constant for three primary color wavelength regions , even when its transmittance is changed. The fabricated filter exhibited a high extinction ratio of 70: 1 for an applied voltage of 20 Vrms, and the color temperature shift of the transmitted light was less than 200 K . We then developed an automatic light exposure system in which the variable filter is driven so that the video signal level is kept constant . By applying aperture control of a zoom lens to this automatic exposure system , we were able to achieve a new video effect where the focal depth of a captured image could be independently controlled while keeping the video level constant . キーワー ド:減 光 フ ィルタ,ゲ ス トホス ト液晶 ,映 像撮像 自動露出,被 写界 深度