Stock material or miscellaneous articles – Circular sheet or circular blank – Recording medium or carrier
Reexamination Certificate
1998-06-18
2001-09-11
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Circular sheet or circular blank
Recording medium or carrier
C428S064200, C428S064400, C428S064700, C428S064800, C428S065100, C264S001330, C430S270110, C430S270140, C430S270200, C430S270210, C369S013010
Reexamination Certificate
active
06287662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aqueous dispersion recording medium, and more particularly to a writable optical data recording medium having at least a light-absorbing layer and a light-reflecting layer on a light-transmitting substrate.
2. Description of Related Art
Conventional writable optical data recording media are essentially structures in which a light-absorbing layer consisting of an organic dye or the like is located on a light-transmitting substrate having spirally formed pregrooves, and a light-reflecting layer consisting of a metal film or the like is located on the light-absorbing layer, as described in Japanese Patent Publication 7-105065, for example.
Data is recorded when laser-based recording light is directed onto the optical data recording medium from the substrate side so as to allow the energy to be absorbed by the light-absorbing layer, and recording pits are formed as a result of the heating and decomposition of the dye in the light-absorbing layer, thermal deformation of the substrate, and so forth.
Such writable optical data recording media are generally known as “CD-Rs.” Such CD-Rs characteristically are capable of only a single recording, which cannot be erased, and are highly compatible with read-only CDs (compact discs) and CD-ROMs, making them quite popular, particularly in the data processing fields.
The growth of data as well as the increasing sophistication and complexity of data processing have led to more rapid recording on optical data recording media and more rapid read-out in the last several years. 6× recording devices and 15× read-out CD-ROM drives became commercially available by the end of 1996 in the CD-R market.
Efforts have been made to obtain an optical data recording medium in which the recording speed is 6 times faster, assuming, for example, 6× high speed recording, where the medium is irradiated with high output laser light in time increments that are about ⅙ the time corresponding to the pit length nT of the EFM signal, resulting in the recording of signals within a stipulated range of pit lengths 3T to 11T.
Accordingly, precision greater than that of conventional equal-speed recording is needed in order to control the T recording pit length of recording devices.
Since it is also necessary to form pits of a prescribed length in a fraction of the conventional time on recording media, the effects of heat and thermal interference during recording are far greater than in the past.
Thermal irregularities produced during such high speed recording thus result in worse jitter, causing deviation in pit length.
In Japanese Laid-Open Patent Application 4-192131, for example, dyes such as benzoindodicarbocyanin and indodicarbocyanin are mixed as the light-absorbing substance in the light-absorbing layer.
That is, the benzoindodicarbocyanin is added as a light-absorbing agent, and the indodicarbocyanin is added as an agent to increase the reflectivity. The benzoindodicarbocyanin absorbs the recording light and thus decomposes, but the indocarbocyanin does not absorb the recording light and is thus not decomposed. Sufficient modulation thus cannot be achieved or the jitter deteriorates when the light-absorbing layer has a film thickness of less than 100 nm. In other words, these problems come about when there is a lower proportion of molecules absorbing laser light in the film.
These problems occur when two or more dyes are mixed as the light-absorbing substance and also when just one dye is used, and are the effects of molecular and association absorption in the absorbance spectra described below.
SUMMARY OF THE INVENTION
With the foregoing in view, an object of the present invention is to provide an optical data recording medium in which the shape of the dye spectrum is controlled so as to enable improvements in the recording speed during high speed recording, jitter, and modulation.
Another object of the present invention is to provide an optical data recording medium that has a dye film with a thin film thickness per unit absorbance (unit absorbance thickness).
Yet another object of the present invention is to provide an optical data recording medium in which the light-absorbing substance (dye) in the light-absorbing layer of the dye film has a sharp absorbance spectrum peak.
That is, in the present invention, it was noted that the recording and playback properties can be improved by making the light-absorbing layer as thin as possible, by improving the recording sensitivity using a dye (such as a benzoindocyanin dye) with less association absorption on the short wavelength side and more molecular absorption on the long wavelength side of the dye in the light-absorbing layer, and by keeping the unit absorbance thickness within a small prescribed range. The present invention is an optical data recording medium, which comprises: a light-transmitting substrate; a light-absorbing layer that is located on the substrate and that contains a light-absorbing substance constructed of a dye that absorbs laser light-based recording light; and a light-reflecting layer that is located on the light-absorbing layer and that reflects laser light, said recording light being used to irradiate said light-absorbing layer to record data, wherein the optical data recording medium is characterized in that 0<D/C≦100, and 80≦D/B, where D (nm) is the mean film thickness of the light-absorbing layer, C (Abs) is the maximum absorbance (based on molecular absorption) of the light-absorbing substance, B (Abs) is the maximum absorbance (based on association absorption) of the light-absorbing substance, D/C is the unit absorbance thickness based on the molecular absorption, and D/B is the unit absorbance thickness based on the association absorption.
The lower the D/C value the better, although this value depends on the dye material, and is virtually unaffected by the structure of the recording medium.
The D/C value is 0<D/C≦100. When the value is greater than 100, the film thickness D is too great relative to the maximum absorbance C based on molecular absorption, resulting in excessive dye film thickness during the manufacture of the disk and making it impossible to achieve satisfactory modulation and jitter specifications during recording and playback.
The unit absorbance thickness D/B based on the aforementioned association absorption should be D/B≦300.
The D/B value is 80≦D/B. When the value is less than 80, the absorption peak on the short wavelength side is too great relative to the film thickness D, with a corresponding decrease in the absorption peak on the long wavelength side, making it impossible to record with sufficiently low laser power because of the decrease in the absolute absorption of the dye at the recording laser wavelength at the tail of the peak on the longer wavelength side of the absorption peak on the long wavelength side.
Conversely, when the D/B value is greater than 300, there is a correspondingly excessive increase in the absorption peak on the long wavelength side, so that, in contradistinction to the reasons given above, the excessive absolute absorption of dye at the laser wavelength makes it impossible to obtain adequate reflectivity during play back and prevents satisfactory specifications from being met.
H≦180 nm is preferred, where H is the half-width at the wavelength of the maximum absorption peak of the aforementioned light-absorbing substance.
The value H is H≦180 nm. When a material with a value greater than 180 is used, recording with sufficiently low jitter is not possible.
The maximum absorbance C of the aforementioned light-absorbing substance should be 0.6≦C≦1.1.
The value C is 0.6≦C≦1.1. When the value is greater than 1.1 (Abs), the absorptivity at the laser wavelength is too great, the balance in pit length is lost during pit recording within the stipulated pit length range of 3T to 11T, it becomes difficult to record pits of the prescribed length, deformation and distortion tend to be produced, p
Hamada Emiko
Matsumoto Takanobu
Shin Yuaki
Takagishi Yoshikazu
Chen Vivian
Ostrolenk Faber Gerb & Soffen, LLP
Taiyo Yuden Co. Ltd.
LandOfFree
Optical data recording medium does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical data recording medium, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical data recording medium will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452871