Toshiyuki Nakano

Experimental Study of High-Density Rewritable Optical Disk Using a Blue-Laser Diode

The read-write characteristics of an optical disk utilizing a blue-laser diode are examined, applying land and groove recording and partial response and maximum likelihood (PRML) to two optical disk systems: 1) 0.85 numerical aperture (NA) optical disk system consisting of an objective lens with NA of 0.85 and a thin cover layer on a disk with a thickness of 0.1 mm and 2) 0.65 NA optical disk system consisting of an objective lens with NA of 0.65 and a 0.6-mm-thick disk substrate. In the 0.85 NA optical disk system, the track pitch and the data bit length employed for the experiment are 0.29 µm and 0.0987 µm, respectively. These parameters correspond to a capacity of 30 GB/side. In the 0.65 NA optical disk system, they are 0.37 µm and 0.155 µm, respectively, corresponding to a capacity of 15 GB/side. A bottom channel bit error rate (ch.bER) of less than 5.0×10-5 can be obtained in these systems, and it is confirmed experimentally that the ch.bER remains below 1.0×10-4 up to 1000 cross-write cycles.

Effects of second particles on nonlinear resistance properties of microvaristor-filled composites

Microvaristors are used particularly as lightning arrestors. In addition, they are used as electric field grading materials and stress control devices to reduce the localization of electric fields in various electric equipment. Nonlinear resistance properties are generally attributed to the high-loading of microvaristor fillers in the resin. However, high-loading is prone to cause aggregation and sedimentation of microvaristor fillers in the resin. This tendency adversely affects nonlinear resistance properties based on microvaristor fillers. Therefore, secondary particles should be provided as a disperser and then these particles can help the microvaristor to disperse homogeneously. In addition, the secondary particles can act as conducting paths between microvaristor particles. In recent research, we developed an effective way to improve the nonlinear resistance properties of a microvaristor-filled composite material. In the method, we focused on the adding of the semi-conductive whiskers as secondary particles to the resin. We chose the candidates of the second particles based on the shapes and the electrical properties. We finally determined the semi-conductive whiskers with the tetrapod-like shape. The effects of secondary particles on the nonlinear resistance properties of microvaristor-filled materials are investigated in this paper.

High-Density and High-Carrier-to-Noise-Ratio Optical Disk Mastering

A scanning tunneling microscope (STM) was used to observe the surface profile of an optical disk and to quantitatively evaluate the lithography conditions in the mastering process. A high-density and high-carrier-to-noise-ratio (C/N) optical disk was achieved using precise data concerned with the relations among the mastering process, the profile of the masters, and the readout signal.

Electrical properties of composite material containing microvaristor and tetrapod ZnO

In recent years, Gas Insulated Switchgear (GIS) is becoming compact which implies a relatively high electric field in the enclosure. In the result, its compactness can make metallic particles move easily. To suppress the movement of particles in the tank of GIS, the nonlinear resistive coating has been developed [1]. The coating contains the microvaristor. However, the sedimentation of microvaristor often occurs in the microvaristor filled composite. The effective way to prevent sedimentation of microvaristors was found [2]. In the method, adding the special shaped semi-conductive zinc oxide (tetrapod ZnO) is of current interest. In this paper, the role of the second particle on the conduction was discussed.

Electrical properties of composite material containing microvaristor and semi-conductive whisker

Microvaristors are used particularly as lightning arrestors. In another case, they are used as the electrical field grading materials. Additionally, we especially focused on their low volume resistance at the composite material of the microvaristors to use it as the anti-electrostatic coating. In the previous study, we found a solution to disperse microvaristors uniformly. In that study, we used semi-conductive whiskers to disperse microvaristors uniformly and connect electrically to make conducting paths. In this paper, we focused on the adding of the semi-conductive whiskers as secondary particles to the matrix and measured electrostatic charging properties.

Electrical properties of composites with microvaristors and several secondary fillers

Reduced dimensions of Gas Insulated Switchgear (GIS) implies a relatively high electric field in the enclosure. To suppress particle movement in the GIS tank, a nonlinear resistive coating has been developed that contains microvaristor fillers. The effect of putting several secondary fillers is important to understand the mechanism of electrical properties of the composites. In this paper, the effects to the electrical properties of adding microvaristor / secondary filler content in the microvaristor filled composites were investigated. Besides, inner structure measurement, calculation, and simulation of the composite were conducted.

Electrical properties and inner structures of composite material containing microvaristor and semiconductive ZnO

Microvaristors are used particularly as lightning arrestors. Meanwhile, they are used as the electrical field grading materials. In the past study, we, we found a solution to disperse microvaristors uniformly. In that study, we used Semiconductive ZnO to disperse microvaristors uniformly and connect them electrically by making conducting paths. In this paper, we focused on the adding of the semiconductive ZnO as secondary particles to the matrix and measured electrical properties, particularly measured volume resistivity and conducting voltage in the coating. Moreover, we measured the inner structure of the coating.

Experimental study of 30 GB/side rewritable optical disk using a blue-laser diode

The read-write characteristics of a land and groove disk have been examined using a blue-laser diode, high NA objective lens and the PRML method. The wide tilt and defocus margins have been obtained and no deterioration by CW has been observed at a data bit length of 0.0987 /spl mu/m and a track pitch of 0.29 /spl mu/m. These experimental results certify the feasibility of a rewritable optical disk with a capacity of 30 GB/side.