Makoto Ohashi

Magnetization, strain, and anisotropy field of Ne+ and H+ ion‐implanted layers in bubble garnet films

The effects of the implantation dose and annealing on magnetization (4πMs), lattice constant strain (Δd/d), and change in the anisotropy field (ΔHK) of a layer implanted with Ne+ or H+ ions in bubble garnet films have been investigated using a vibrating sample magnetometer (VSM), the double crystal x‐ray technique, and ferromagnetic resonance measurements. The magnetic and crystalline properties of Ne+ or H+ ion‐implanted layers were quite different. Saturation magnetization of the H+ ion‐implanted layer decreased gradually with Δd/d beyond 1%, while that of the Ne+ ion‐implanted layer decreased abruptly above 1%. ΔHK of the Ne+ ion‐implanted layer was proportional to Δd/d up to a saturation point of about 1%; however, ΔHK of the H+ ion‐implanted layer continued to increase after Δd/d passed 1%. The other distinct difference between the H+ and Ne+ ion‐implanted specimens was the temperature necessary to obtain annealing effects. In the H+ ion‐implanted layer, annealing in the lower (around 200 °C) tempera...

Wide‐viewing‐angle full‐color TFT‐LCDs

— Conventional TFT TN-LCDs display full-color images only within a narrow vertical viewing angle. Viewed obliquely, the display reverses or brightens. We studied these problems by calculating the light propagation through TN cells and concluded that these reversal phenomena are unavoidable in TN-LCDs. To widen the viewing angle, we propose a film-laid double-twisted-nematic display (FDTN), consisting of a conventional TN panel, a light-compensation panel, and two retardation films stacked together. The problem of black images appearing purple is solved using a clockwise-twisted nematic panel as an optical compensator. The viewing angle of the FDTN-LCD is about 1.5 times that of the conventional positive TN-LCD. The contrast ratio normal to the panel exceeds 100.

A full-color TFT-LCD with a polymer-dispersed structure

— A direct-view TFT-LCD with a wide viewing angle, which uses a polymer-dispersed liquid-crystal panel and a pair of polarizers, is proposed. The device has a vertical viewing-angle range of 120°, with a contrast ratio over 5:1 without display-image reversal. This is about three times the twisted-nematic displays viewing-angle range.

Development of an ion implanted bubble device with 4 µm period

A 4 μm period ion implanted bubble device has been developed employing 1 μm bubble single layer film. The design and characterization of a transfer-in gate are described. The effect of the pulse shape on operating margins has been investigated, and an auxiliary pulse added to the transfer pulse to greatly improve gate performance. This newly designed transfer-in gate has also been successfully operated as a bidirectional transfer gate. In order to decrease the access time of large capacity chips, a highly efficient method of detection at high frequencies has been devised. Characterization of the device at 300 kHz is presented.

Design and characteristics of 4 µm period ion-implanted bubble devices with major line block replicate gate

A block replicate gate composed of an ion-implanted minor loop and a permalloy major line has been developed for 4 μm period bubble devices. This gate employs a hybrid permalloy and ion-implanted bubble device with no junction between the patterns. Test chips incorporating this replicate gate, the folded minor loop, and the cusp-to-cusp bidirectional transfer gate have been fabricated and characterized for a 100 kHz triangular drive field. A bias field margin of 30 Oe was obtained at 70 Oe ± 10 % peak drive field.

Cusp-to-cusp transfer gate using folded minor loop organization for ion-implanted bubble devices

Ion-implanted bubble devices using the folded minor loop organization have been developed to relax spatial restrictions on function pattern design and improve the reliability of gate conductors. A cusp-to-cusp transfer gate using this organization has been designed in which bubbles are transferred between the cusps of the propagation patterns of the major line and minor loops. A 180° inside turn has also been designed in order to realize the folded minor loop organization. Test chips incorporating 4 μm period devices with the folded minor loop organization have been fabricated and characterized for a 100 kHz triangular drive field.

Design of a block replicate gate for ion-implanted bubble devices

A block replicate gate has been designed for 4 μm period ion-implanted bubble devices. The gate consists of a conductor lying across a V-shaped unimplanted pattern between the minor loop end and the major line. Replication is accomplished by stretching the bubble with a stretch pulse through the conductor, cutting the domain by means of the charged wall formed at the edge of the V-shaped pattern together with a pulse of short duration, then restoring the bubble to the original condition by means of another stretch pulse. A bias field margin of 20 Oe was obtained with an error rate of 10-5for a 100 kHz, 80 Oe peak triangular drive field.

Direct-view polymer-dispersed LCD with crossed Nicols and uniaxial film

— By adding a uniaxial retardation film and using a chlorinated LC mixture, the performance of polymer-dispersed LCDs with crossed Nicols (PDN-LCDs) was improved. A wide viewing angle of more than 60° (contrast ratio >5) for all azimuth directions was obtained. In the horizontal and vertical viewing azimuth, the contrast ratio was over 30 even at an inclination viewing angle of 60°.

Design of 2 µm-period minor loops in hybrid bubble memory devices

The folded minor loops for hybrid bubble memory devices with 2 μm period propagation tracks have been developed by designing junctions between permalloy and implanted tracks, as well as designing inside and outside turns. The junction from the permalloy to the implanted tracks has been successfully designed utilizing the deep potential well of the permalloy pattern for bubbles to cross the boundary. The junctions were operated successfully for the first time using 0.6 μm bubbles optimized for 2 μm period tracks. We also designed the outside and inside turns considering the demagnetizing field and the crystalline axis of the implanted layer respectively. As a result, good bias margins of turns were obtained. The bias field levels of all elements agreed quite satisfactorily. Overall bias field margins of 40 Oe has been obtained with the quasi-static drive field of 70 Oe.

A Full-Color Direct-View TFT-LCD with a Polymer-Dispersed Structure.

We propose a direct-view TFT-LCD with a wide viewing-angle which uses a polymer-dispersed liquid-crystal panel and a pair of polarizers. We call this device a polymer-dispersed LCD with crossed Nicols (PDN). The PDN allows panels to be made with low scattering levels.This suggests the use of fluorinated liquid crystals (F-LC) that show a high voltage-holding ratio in TN-LCDs. We found that F-LCs show good solubility with resins having low solubility parameters. A voltage-holding ratio of over 98% is shown, which is almost equal to the value for TN-LCD. The vertical viewing range exceeds ±60°, with a contrast ratio of over 5 and no image reversal. The range is almost three times the TN-LCD value. Molecular alignment is symmetrical and the variation of overall retardation is suppressed. The TFT-LCDs fabricated show a high contrast ratio and no imag reversal at any viewing angle.