Akio Kumada

Transparent flat panel piezoelectric speaker

This invention intends to provide a speaker which assumes a comparatively large area in a device without spoiling various display effects. The transparent flat panel speaker of this invention is a speaker of high efficiency which can give forth a sound volume large considering the small-sized device even when driven by a low voltage. The transparent flat panel speaker of this invention comprises, at least, a transparent resonator plate and a plate of a piezoelectric material held between at least one pair of electrodes, the resonator being excited by the piezoelectric material plate, a periphery of the resonator plate having a shape which is represented by a curve or in which straight lines are connected by smooth curves with at least two centers of curvature. As the peripheral shapes, an ellipse, a curve expressed by Xn /a+Yn /b=1, a plane figure obtained by molding the corners of a polygon circumscribed or inscribed to an ellipse, etc. are especially favorable for the speaker.

Ultrasonic motor using bending, longitudinal and torsional vibrations

An ultrasonic motor having a cantilever type longitudinal/torsional vibration coupling element with a beam and a rotor rotated by the vibration of the beam. The rotor is provided with contacting surface for only contacting the beam in the outer peripheral portion of the surface of the beam away from the torsional vibration axis of the beam.

An electrooptic image storage device using field induced reversible transitions between AFE and FE phases of PLZT ceramics

Abstract Field induced reversible transitions between AFE and FE phases of PLZT ceramics are considered to realize a high contrast image storage and display device. The proposed field-induced phase transition takes the material from a non-scattering AFE phase to a scattering FE phase, and returns the material to the original AFE phase by the application of a reverse field. The transitions can be accomplished by relatively low electric fields of several kV/cm. The required double hysteresis loops which indicate the reversible phase changes between AFE and FE phases were obtained in the composition of PLZT-7.6/70/30. Typical characteristic features accompanying the phase transitions are explained in terms of the phase relations of PLZT ceramics.

Display applications of field-enforced phase transition in PLZT ceramics

Abstract Experiments to determine the applicability of field-enforced reversible transitions between antiferroelectric and ferroelectric phases in PLZT 7.9/70/30 ceramic to flat panel picture display devices reveal that the ceramic has three remarkable advantages over ordinary ferroelectric phase PLZT ceramics. They are: (1) the high transparency of the antiferroelectric PLZT 7.9/70/30 ceramic makes possible a higher contrast display material, (2) the absence of remanent polarization when no electric field is applied makes possible a faster erase display material, and (3) the linear relation between the field-induced scattered light intensity and the simultaneously induced ferroelectric polarization makes possible the control of gray-scale in a display by controlling the polarization charge switched.

Observation of phase boundaries between ferro- and paraelectric phases in Gd2(MoO4)3 crystals

Abstract Phase boundaries between paraelectric and ferroelectric phases have been observed under crossed polarizers. Parallel to the crystal b -axis there is a sharp phase boundary, whereas a gradual transition region exists along the b -axis. When an electric field is applied domain switching occurs, and as a result the phase front moves so that it becomes parallel with the b -axis. The observation of a sharp boundary strongly suggests that the transition is first order.

Display device with transparent cover as a vibrator of a sound generator

Disclosed is a display device including a transparent piezoelectric element having transparent electrodes coated on both surfaces thereof, bonded by transparent adhesive material on an inner surface of a transparent cover to be arranged in front of a display panel of the display device. The transparent cover works as a vibration generator of a sound source. The thickness of the transparent electrodes are selected to serve as an anti-reflection layer of the near ultraviolet light. Relative dimensions of and positional relation between the transparent cover and the piezoelectric element are limited in predetermined ranges to assure high quality of display characteristic and sufficient volume of sound.

Artificial creation of threshold characteristics in the domain switching of ferroelectric—Ferroelastic Gadolinium molybdate

A new method of providing artificially well-defined threshold characteristics in the domain switching of ferroelectric-ferroelastic Gd 2 (MoO 4 ) 3 single crystals is presented and experimentally confirmed. The essence of the idea lies in the utilization of a coupling effect between the strain and the polarization which is a characteristic of ferroelectric-ferroelastic crystals. The potential barrier required for electrical switching with a definite threshold is produced by the strain due to locally deposited surface films, which results in strain-induced multidomain regions beneath the films and stabilizes the domain wall at the end of strain-free switching regions. The measured characteristics of the threshold switching elements were as follows; threshold voltage V_{t}=190 V and switching time t_{s} = 0.6 ms at applied full voltage V_{f} = 250 V. These threshold switching elements have potential applications to a ferroelectric light valve array and a ferroelectric memory device.

Observation of double hysteresis loops in Gd2(MoO4)3

Abstract Clear double hysteresis loops of Gd2(MoO4)3 were observed just above the phase transition temperature Tc The sample was a c-plate, 50 μm thick, 3.8 mm long, and 3.3 mm wide, coated with transparent electrodes of SnO2. The double hysteresis loops were clearly observed in the temperature range Tc + 0.1 to 0.5°C under an applied A.C. field Ea = 3 × 106 V/m of 5 × 10 −3 Hz. The obtained value of (∂E/∂T) = 6.54 × 106 (V/m. deg) agrees well with the value of (ΔS/ΔPs ) ≊ 5.7 × 106 (V/m. deg).

A high contrast image display device using a PLZT ceramic

A high contrast image display device using a PLZT ceramic plate which has field-induced, reversible phase transition between the light scattering ferroelectric (FE) phase and the nonscattering antiferroelectric (AFE) phase is described.A coarse-grained (grain size > 10 μm), thicker ceramic plate and a long focus lens are required for projecting a high contrast image with a schlieren system.The value of contrast ratio produced by a 200 μm thick, 7.6/70/30 PLZT ceramic plate, when used in the image projection system described in this paper, exceeded 50:1, and the insertion loss of the plate was less than 1 dB.