Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2001-09-19
2003-06-10
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064800, C430S270140, C369S275300
Reexamination Certificate
active
06576321
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a high-density optical recording medium, in particular an optical recording medium capable of recording and/or reproducing by a plurality of laser wavelengths.
2. Description of the Related Art
Optical recording media capable of recording comprising a dye in a recording layer where a reflective layer is deposited on the recording layer for increasing a reflectance have been disclosed in, for example, Optical Data Storage 1989 Technical Digest Series, Vol. 1, 45 (1989). Since then, media employing a cyanine or phthalocyanine dye in a recording layer have been widely marketed as a CDR. These media can record data with a semiconductor laser at 780 nm and have a characteristic that they are compatible in reproduction with a commercially available CD-ROM player equipped with a semiconductor laser device at 780 nm. Furthermore, a DVD-R (Digital Versatile Disk-Recordable) medium with a capacity of 4.7 GB has been recently proposed and has been commercially available, which is capable of recording/reproducing large data such as an image and a moving picture with a red semiconductor laser at 630 to 680 nm and can be reproduced by a DVD or DVD-ROM player. More recently, investigation has been started for an HD-DVDR (High Density DVDR) with a high density of 15 GB or more which can also deal with a high-definition moving picture as a blue-violet laser at 390 to 430 nm has been available.
For making a medium applicable to high-density recording/reproduction, a system must be modified along with reduction in a laser wavelength, while absolutely such system modification must take over and stably reproduce software resources such as development software previously widely spread in existing systems and databases accumulated for a long time.
In these circumstances, a read-only medium such as CD, CD-ROM, DVD-Video and DVD-ROM may be relatively easily reproduced by a modified player equipped with a short-wavelength laser device because it basically does not use a dye and thus a reflectance, a modulation factor and a tracking output are less dependent on a wavelength.
However, in an existing CDR medium using an organic dye in a recording layer, optical properties in a recording layer is considerably dependent on a wavelength so that a reflectance, a modulation degree and a tracking output largely vary depending on a wavelength. For example, a dye used in a recording layer has a reflectance of 65% or more for a light at about 780 nm while absorbing a red light at a wavelength from 630 to 680 nm so much that a reflectance is reduced to about 10%. Furthermore, a modulation degree is also reduced and in some cases significant distortion is observed in a recording waveform. If a reflectance is about 10%, it is very difficult to detect a signal. Even if a signal can be detected, an error rate or jitter is too high to conduct reproduction by a common player.
For reproducing a CDR with quality meeting specifications for CD and DVD at individual wavelengths, for example, JP-As 8-156408, 8-310121, 9-267562 and 11-11015 have proposed that two dyes having optical sensitivity (variation in a refractive index) at wavelengths of about 780 nm and in a range of 635 to 670 nm, respectively, may be used to achieve reproduction compatibility at these wavelengths by selecting a proper lamination structure and blending them in appropriate amounts in a recording layer. However, these lamination and blending techniques practically require very narrow and severe preparation conditions (control of a film thickness and of blending) for retaining satisfactory recording properties at each wavelength. Thus, these techniques are improper to practical medium preparation. Therefore, a DVD player is now equipped with an optical system comprising substantially two laser emitting diodes at 780 and 650 nm together within a chip, for reproducing DVD and CDR.
In an existing DVDR medium using an organic dye in a recording medium as in a CDR medium, the above wavelength dependence has not been also improved at all. Thus, even when using a DVD compatible signal which can be reproduced at about 650 nm with a reflectance of 45% or more, not only a reflectance but also a signal modulation factor may be too reduced to detect a signal. In terms of combining a red and a violet laser devices, these laser devices, in principle, have different compositions and it is thus difficult to integrate these laser devices in a chip. There has been, therefore, strongly needed proposal of an optical recording medium which can properly combine reproduction at these wavelengths. JP-As 11-110815 and 11-105423 have proposed a DVDR which can be reproduced with a blue laser using a dipenylaminosqualirium or cyanostyryl compound. According to our investigation, it, however, has a problem in processability so that it cannot provide a satisfactory recording film. Except that, there have been substantially no good proposals for a DVDR medium ensuring reproduction compatibility between red and violet wavelengths.
SUMMARY OF THE INVENTION
An objective of this invention is to provide an optical recording medium capable of providing a recording/reproduction signal meeting the DVD specifications and capable of recording and/or reproduction using a violet laser at a wavelength selected from a range of 390 to 430 nm.
For solving these problems, we have intensely conducted investigation and have finally found that an azaporphyrin metal complex with 1 to 4 meso-nitrogen atoms has sharp optical absorption bands, i.e., a Soret band (blue region) and a Q band (red region) exhibits proper balance between a higher refractive index and an appropriate attenuation coefficient at wavelengths in these bands and thus in these wavelengths gives a good reproduction signal, leading to this invention.
Thus, this invention provides:
[1] an optical recording medium comprising at least a recording layer and a metal reflective layer on a transparent substrate having a groove, wherein the recording layer comprises an azaporphyrin metal complex dye with 1 to 4 meso-nitrogen atoms represented by formula (1) as a main component; recording and/or reproduction can be conducted using a laser beam with a wavelength of &lgr;1 and also with a laser beam with a wavelength of &lgr;2 shorter than &lgr;1; the recording layer has a refractive index n of 2.0 or more at &lgr;1 and 1.8 or more at &lgr;2 as well as an attenuation coefficient k of 0.04 to 0.20 at &lgr;1 and 0.30 or less at &lgr;2; and the groove in the transparent substrate has a pitch of 0.70 to 0.85 &mgr;m, a half-value width of 0.20 to 0.35 &mgr;m and an inclination angle of 45 to 65°:
wherein X
1
to X
3
independently represent nitrogen or CH; R1 to R8 are independently selected from the group consisting of hydrogen, halogen, substituted or unsubstituted alkyl with 1 to 12 carbon atoms, substituted or unsubstituted aryl with 6 to 20 carbon atoms, hydroxyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryloxy, amino or alkylamino, nitro, cyano, carboxy, substituted or unsubstituted carboxylate, substituted or unsubstituted carboxamide, alkylthio, arylthio, sulfonic, substituted or unsubstituted sulfonate, substituted or unsubstituted sulfonamide, substituted or unsubstituted silyl and siloxy; and the central metal M represents transition metal which may be charged to have a cationic salt structure;
[2] the optical recording medium as described in [1] wherein recording and reproduction can be conducted using a laser beam at a wavelength of &lgr;1 while reproduction can be conducted using a laser beam at a wavelength of &lgr;2;
[3] the optical recording medium as described in [1] or [2] wherein the laser wavelength &lgr;1 is selected from the range of 630 to 680 nm while the laser wavelength &lgr;2 is selected from the range of 390 to 430 nm;
[4] the optical recording medium as described in any of [1] to [3] wherein as determined through the substrate, a r
Koike Tadashi
Mihara Norihiko
Burns Doane , Swecker, Mathis LLP
Mitsui Chemicals Inc.
Mulvaney Elizabeth
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