Optical information recording medium

Details Optical information recording medium Optical information recording medium

1998-08-03

2001-01-02

Evans, Elizabeth (Department: 1774)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S064200, C428S064400, C428S064800, C428S913000, C430S270180, C430S270200, C430S495100, C430S945000, C369S283000, C369S288000

Utility Patent

active

06168844

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording medium, and more particularly to a writeable optical information recording medium comprising at least a light absorbing layer and light reflecting layer on a transparent substrate.
2. Description of the Related Art
Conventional, writeable optical information recording media are based on the structure wherein a light absorbing layer, comprising an organic dye, is established on a transparent substrate which is pre-grooved in a spiral pattern, and a light reflecting layer, comprising a metal film or the like, is further established on the light absorbing layer, as in Japanese Patent Publication No. 07-105065.
Information is recorded as follows. A recording beam, such as a laser beam, is shone on this optical information recording medium from the substrate side thereof. The light absorbing layer absorbs the energy and a pit is recorded by the heating or decomposition of the dye in the light absorbing layer, or the thermal deformation of the substrate.
Such a writeable optical information recording medium is generally known as a “CD-R”. A CD-R is essentially a compact disk (CD) for playback purposes or a disk such as a CD-ROM; this can only be written to once and the records cannot be removed. For this reason, these have come to be widely used, especially in the field of information processing.
With the increasing amounts of information to be recorded and the ever more highly complex levels of information processing, the speed of recording on and reading from optical information recording media have both been increasing for the past several years. 6× recording apparatuses and 15× CD-ROM drives for reading disks were common in the CD-R market by the end of 1996.
When recording at high speeds, like at 6×, for example, the line speed is multiplied six times and a high output laser beam is radiated for ⅙ of each period of time corresponding to each pit length nT of the EFM signal. As a result, an optical information recording medium recorded with a signal having pit lengths within the prescribed range of 3 T to 11 T is attained.
Consequently, in order to control the length of each recorded pit T, the recording apparatus must have a precision greater than in conventional recording at an equivalent speed. Also, because pits of each prescribed length must be formed in only a fraction of the time used before now, the impact of heat generated during recording and of heat interference on the recording medium is accordingly greater than before. A consequent problem is that the jitter, which results from the thermal heterogeneity generated during high speed recording, has been made worse.
In other words, it becomes impossible to attain an adequate reflectivity where k and dav are high at the wavelength at which data are to be recorded, when k is the imaginary number portion of the complex index of refraction of the film in the aforementioned light absorbing layer, and dav is the mean film thickness of the light absorbing layer. Oppositely, when k and dav are small, adequate reflectivity can be attained, but the recording sensitivity drops and sufficient recording becomes impossible, even with the recording laser at maximum power.
When the aforementioned k and dav are high, a reflectivity Rtop of 65% or greater cannot be achieved with a disk as the recording medium.
Oppositely, when k and dav are low, the problems are that a laser at sufficiently low power cannot effect recording and the increased jitter makes it difficult to adjust to high speed recording as discussed above.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide an optical information recording medium, which is recordable at high speeds because of increased sensitivity to the recording beam.
It is another object of the present invention to provide an optical information recording medium with increased sensitivity to the recording beam, resulting in good sensitivity and no variations in the recording characteristics, meaning little difference in sensitivity, even when recording with a similar, but different type of laser.
It is another object of the present invention to provide an optical information recording medium, which makes possible sufficient reflectivity and stable recording and. which can reduce jitter.
It is another object of the present invention to provide an optical information recording medium, with good recording sensitivity and playback characteristics because of adjusting the following to within an appropriate range: the imaginary number portion k of the complex index of refraction of the film in the light absorbing layer, the mean film thickness dav of the light absorbing layer, and the absorbency A related thereto.


REFERENCES:
patent: 5161150 (1992-11-01), Namba
patent: 5316814 (1994-05-01), Sawada et al.
patent: 5415914 (1995-05-01), Arioka et al.
patent: 5547728 (1996-08-01), Cunningham et al.
patent: 0353393 (1990-02-01), None
patent: 0396040 (1990-04-01), None
patent: 0840307 (1997-10-01), None
patent: 7105065 (1995-11-01), None

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