Keiji Suga

25 Gbyte Read-Only Memory Disk by Injection-Compression Molding Process

We studied the feasibility of fabricating a disk replica at a recording capacity of 25 Gbytes by a conventional injection molding process. This work is the first attempt at fabricating a disk replica using a stamper recorded by an electron beam recorder. The bottom jitter value of the injection-molded disk was 9.3% when using a conventional equalizer and 6.5% when using an additional limit equalizer. These values were highly similar to those of the photo-polymer (2P) disk. The residual error on the axial tracking of the injection-molded disks was smaller than that of the 2P disk, and the residual error on the radial tracking was almost the same as that of the 2P disk.

Superlarge-capacity optical disk with multilayer structure fabricated using a photopolymer sheet

We have been studying a multilayer disk in order to realize a 12-cm-diameter optical disk with the recording capacity of 100 GB or more. We tried to fabricate a multilayer disk using a photopolymer sheet. We developed a new sheet, and confirmed the performance of this sheet. A single layer disk made using this sheet had a value of 5.3%, and a 25 GB capacity. Then we fabricated a dual layer disk. The thickness variations from the disk surface to each recording layer were ±0.6 µm and ±0.7 µm. These results indicated the possibility of realizing a multilayer disk for a high-numerical-aperture (high-NA) system. We will evaluate the signals reproduced from the multilayer disk in the next step.

Mechanism of Radial Skew Generation of an Optical Disk

It is important to control radial skew in order to realize a high-density optical disk. However, the causes of the radial skew had not been made clear. In this paper we will describe the causes. We also developed a new method to analysis for the radial skew. By using this method, we found that the temperature difference between a static cavity surface and a moving cavity surface caused the radial skew, which fluctuated on a radius. We also found that a mechanical ejector pushout, and the temperature difference between sprue parts and cutter parts caused the central skew component of the disk. At the same time, we were also able to realize that the radial skew was caused by the stumper came from the thermal resistance between the stumper and the cavity.