Yoshikazu Takagishi

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.

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.