Emiko Hamada

High Density Optical Recording on Dye Material Discs: An Approach for Achieving 4.7 GB Density

High density optical media is proposed together with a recording method for achieving a density of 4.7 GB per single 12 cm diameter disc at a recording speed of 3.5 m/s.

Ten-Year Overview and Future Prospects of Write-Once Organic Recordable Media

The CD-R market has grown rapidly since the development of this media in 1988. In addition, PC applications have continued to demand ever higher recording speeds. In order to achieve higher speed recording, it is necessary to reduce thermal interference during the recording process. Higher density recording is subject to the same effects of thermal interference as higher speed recording. To directly compare such thermal effects during recording on different density disks with different scanning velocities, we introduce a new parameter. Applying this parameter, it can be clearly demonstrated that thermal interference in higher density digital versatile disc-recordable (DVD-Rs) is approximately equal to that in 8x-speed recording with the lower density CD-R. Today, the possibility of 4x-speed DVD-R recording has already been confirmed. It can thus be concluded that write-once organic recordable media with a 15 GB capacity per 12 cm diameter disk format is very promising, because the thermal effects associated with the 15 GB recordable media are shown to be equivalent to those in 4x-speed DVD-R.

CD-Compatible Write-Once Disc With High Refrectivity

A high reflectivity write-once disc with specifications satisfying the CD Standard has been developed. The new disc realizes a reflectivity greater than 70% and employs a simple configuration with a substrate, photo-absorption layer, reflection layer and protection layer. Since there is no space between layers, high durability is assured. Recording is performed when the substrate resin expands and intrudes into the photo-absorption layer, mixing with the decomposed dye materials. The specifications of the new disc are completely compatible with the current CD Standard, while the discs simple configuration realizes low cost processability.

Recording process of recordable compact disc

A recordable compact disc (CD-R), developed by the authors in 1988, is now widely used for professional audio and data applications. It is a write-once optical disc consisting of a polycarbonate substrate, a light absorbing layer of dyes, a light reflecting layer of metal, and a protective layer. The main features of CD-R compared with other recordable optical discs are its high reflectivity of more than 70% and a large modulation amplitude of around 75% for compatibility with existing compact disc (CD) systems. The disc structure for achieving such high reflectivity and some analyses of the recording mechanism were reported by the authors in 1989. Further discussions on the recording mechanism were made by Holtslag et. al. in 1991. However, those papers did not clarify the mechanism of obtaining the large signal modulation. This paper reports that both the decomposition of dye in the light absorbing layer during recording and the deformation of the substrate surface are the key factors causing the large modulation of the CD-R.

Approach for High Speed Recording of 4.7 GB Digital Versatile Disc-Recordable

The demand for digital versatile disc-recordable (DVD-R) is currently undergoing explosive growth and both higher speed recording and higher density are required. This paper examines the potential for achieving 4x-speed recording on 4.7 GB DVD-R media. 1x-speed and 2x-speed recording are examined experimentally and by computer simulation, and actual recorded signals are found to be in good agreement with predictions based on computer simulation of thermal interference profiles. Based on these results, the heat design technology needed to realize high speed recording is identified and the potential for 4x-speed recording is demonstrated theoretically.