Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2000-11-06
2002-12-24
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064500, C430S270130
Reexamination Certificate
active
06497935
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase-change optical information recording medium, which can be employed in optical memory appliances, more particularly to a phase-change optical information recording medium in the form of a rewritable compact disk, which is generally referred to as compact disk CD-RW.
2. Discussion of Background
As one of optical information memory media capable of recording information, reproducing recorded information and erasing the same with the application of magnetic waves such as laser beam thereto, the so-called phase-change optical information recording medium is known, which utilizes reversible phase changes from a crystalline state to an amorphous state and vice versa, or from one crystalline state to another crystalline state and vice versa.
Of such optical information memory media, the phase-change optical information recording media have been particularly subjected to vigorous research and development activities, since “overwrite”, which would be extremely difficult to perform in the case of magneto-optical memory media, can be carried out by the phase-change optical information recording media with the application of a single beam thereto, and accordingly the optical system on a drive side for the phase-change optical information is simpler in mechanism than that for the magneto-optical memory media.
Conventionally, CDs (compact disks) have been recording media exclusively for reproducing for use with audio appliances or used as reproducing computer software. However, there have been placed on the market CD-Rewritable (usually abbreviated to CD-R), which is an optical information recording medium in which information can be recorded in the CD format, and CD-ReWritable (usually abbreviated to CD-RW), in which the above-mentioned phase-change material is employed, so that they find a variety of applications in the recording media for computers.
Previously, the standards for the phase-change optical recording media CD-RW (hereinafter simply referred to as DC-RW) were limited only to the recording at 2.4 to 2.8 m/s (2×line velocity recording), corresponding to double speed. As a matter of course, a long recording time is required at such a slow speed line velocity, so that there has been a demand for a rewritable CD capable of recording at much higher speed.
On the other hand, it has also been expected that CD-RW could be used as a 1×line velocity recording medium for use with audio appliances or the like.
In order to meet such various demands for recording applications, there have been demanded and in fact have been developed CD-RW media capable of performing multi-speed recording at a plurality of different line velocities on the same medium, namely, which are capable of performing recording at 2×line velocity and 4×line velocity, and also at 1×line velocity.
However, there is still a strong demand for further the enlargement of an effective range of the recording line velocities, and improvements, in particular, with respect to high quality recording at a low line velocity, and excellent compatibility with recording apparatus.
Furthermore, in the course of such various demands for recording applications, recently there has been developed a CD recorder for audio use. In accordance with the development of the CD recorder, there is increasing a demand for a recording medium which has high overwrite durability at low line velocity recording and is capable of attaining high quality recording.
Conventionally a storage capacity of 74 minutes or less has been mainly used. However, recently, CDs with a storage capacity of more than 74 minutes are increasing, which are for audio use. Under such circumstances, the demand for a recording medium with a larger storage capacity is increasing for backing up such long time recorded CDs.
SUMMARY OF THE INVENTION
In view of the above-mentioned status of the prior art in the field of this technology, a first object of the present invention is to provide a phase-change multi-speed optical information recording medium which is capable of recording at different line velocities, has excellent overwrite durability, with minimized reproduction errors, and which is also capable of attaining high quality signal recordings at low line velocities.
A second object of the present invention is to provide a phase-change multi-speed optical information recording medium which has a larger storage capacity than that in general use, namely, a larger memory capacity than that of a. phase-change optical information recording CD-RW currently in general use.
By use of the phase-change multi-speed optical information recording medium of the present invention, an unconventionally effective recording method can be carried out at a low line velocity recording, with excellent durability to overwrite, and appropriate suitability for recording apparatus used in practice. Furthermore, in the present invention, the layer structure of the recording medium including a substrate structure is so optimized that the storage capacity is maximized.
The above-mentioned objects of-the present invention can be achieved by a phase-change optical information recording medium which comprises a substrate and a recording layer provided on the substrate, the recording layer comprising a phase-change recording material capable of recording information, reproducing recorded information, and erasing recorded information reversibly with reversible phase changes in the phase-change recording material, with successive formation of a recording mark with a low reflectivity and a length of at least one unit extending in an optical recording scanning direction, and a space with a high reflectivity and a length of at least one unit extending in the optical recording scanning direction, wherein information is recorded by a plurality of signals being recorded in the recording layer, each signal constituting a recording mark area including a recording initiation marking portion with (a) a length of at least two times a minimum length of the recording mark and (b) a width (W
1
) of at least 1.1 times an average width (W
2
) of the other portion of the recording mark area.
In the above phase-change optical information recording medium, the space, when having a maximum length in terms of the unit, may have a signal level Itop, the recording initiation marking portion may have a signal level Ibtmf, and the other portion of the recording mark area may have a signal level Ibtme, which signal levels rtop, Ibtmf and Ibtme satisfy the formula I:
I
top−
Ibtmf≧
(
I
top−
Ibtme
)
By the thus formed recording mark, recording can be attained with high quality signals with excellent overwrite durability.
Further, in the above phase-change optical information recording medium, the phase-change recording material for the recording layer may comprise constituent elements Ag, In, Sb, Te, and N or O, with the respective composition ratios &agr;, &bgr;, &ggr;, &dgr; and &egr;, in terms of atomic % being:
0<&agr;≦10
3≦&bgr;≦15
50≦65 ≦65
20≦&dgr;≦35
0≦&egr;≦10, wherein &agr;+&bgr;+&ggr;+&dgr;+&egr;=100.
By the provision of the recording layer with the above-mentioned-composition, signal recording performance at low line velocity can be further improved, and the compatibility of this recording medium with other recording apparatus and the range of the corresponding line velocities can be significantly enlarged.
In the above-mentioned phase-change optical information recording medium, the information can be recorded in the phase-change recording material with a different recording line velocity which is either a high recording line velocity or a low recording line velocity, the high recording line velocity being at least 1.2 times the low recording line velocity, the low recording line velocity being any of (1) 1.2 m/s to 1.4 m/s, (2) 2.4 m/s to 2.8 m/s, or (3) 4.8 m/s to 5.6 m/s.
By the above-mentioned recording line velocities, high quality r
Cooper & DunhamLLP
Evans Elizabeth
Ricoh & Company, Ltd.
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