Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2001-08-02
2003-09-30
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064800, C430S270140
Reexamination Certificate
active
06627288
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a porphycene compound useful as a dye, a pigment, a photoelectric functional material and a recording or storage material, in particular as a recording dyestuff for a large recordable optical recording medium whereby information can be recorded and/or reproduced using a blue and/or red laser beam. This invention also relates to an optical recording medium comprising the porphycene compound.
This invention also relates to an optical information recording medium comprising a recording layer capable of high-density recording where recording is particularly conducted using a blue-violet laser with a wavelength of 400 to 410 nm.
2. Description of the Related Art
It is well known that a CD-R (CD-Recordable) has been proposed and developed as a recordable optical recording medium complying to Compact Disk (hereinafter, referred to as CD) specifications and that it has been wide spread for music reproduction and an information terminal.
Generally, a near infrared semiconductor laser at 770 nm to 830 nm is used for recording and/or reproduction of the optical recording medium, where a signal is recorded on a recording layer made of, for example, an organic dye on a substrate in a heat mode. Specifically, when the recording layer is irradiated with a laser beam, optical absorption occurs so that the organic dye generates heat, by which a pit is formed in the recording layer. A recording signal can be detected from difference in a reflectance between areas with and without the pit during laser-beam irradiation.
Such a medium is compliant with CD specifications such as Red Book and Orange Book and is, therefore, characterized in that it may be interchangeably used in a CD and a CD-ROM players. The existing medium, however, has a recording capacity of about 680 MB, which is not adequate in the light of recording of a moving picture. Thus, there has been the need for a higher density and a larger capacity in an information recording medium as a quantity of information has been dramatically increased.
A higher density of a recording medium may be achieved by reducing a wavelength of a laser beam used in recording and reproduction and increasing a numerical aperture (N.A.) in an objective lens. There has been practically used a short wavelength laser at, e.g., 680 nm, 670 nm, 660 nm, 650 nm or 635 nm. Thus, reduction in a wavelength of a semiconductor laser, increase of an N.A. in an objective lens and a data compaction technique have allowed us to obtain an optical recording medium capable of recording a moving picture or a large quantity of information. Consequently, a recordable digital versatile disk (hereinafter, referred to as DVD-R) has been developed as a recordable optical recording medium in response to the above laser beam. A DVD-R is an optical recording medium with a recording capacity of 3.9 GB or 4.7 GB which is writable only once. There has been further the need for developing an optical disk exhibiting good recording properties suitable to the capacity. A red laser used in the medium has a wavelength of 550 nm to 700 nm, preferably about 635 nm to 660 nm. Optical recording media which have been suggested for the conditions include magneto-optical media, phase-change recording media, chalcogen-oxide optical recording media and organic-dye optical recording media. Among these, organic-dye optical recording media might be preferable in the light of their lower cost and good processability.
Recordable optical recording media comprising a recording layer in which a dye is employed and a reflecting layer formed on the recording layer for improving a reflectance have become widely marketed as recordable compact disks (Compact Disk Recordable; CD-R) employing a cyanine or phthalocyanine dye in a recording layer since they have been disclosed in, for example, Optical Data Storage 1989 Technical Digest Series Vol. 1, 45 ('89). These media may permit recording with a semiconductor laser at 780 nm and the data may be reproduced by a widely marketed CD or CD-ROM player equipped with a semiconductor laser device at 780 nm.
Furthermore, DVD-R media with a capacity of 4.7 GB in one side have been recently marketed as an optical recording medium with a higher density than a CD and capable of recording and reproduction of a moving picture with TV quality, in which recording is conducted using a red semiconductor laser with an emission wavelength of 635 to 660 nm and which can be reproduced by a growing commercial DVD video player or DVD-ROM player. Such a DVD-R medium also employs a lamination structure where a dye such as a cyanine and an azo dyes is used in a recording layer and a reflecting layer is formed, having a disk structure where two substrates with a thickness of 0.6 mm are laminated.
It is expected that much higher recording will be in future required, resulting in a larger capacity of 15 to 30 GB. It may be, therefore, inevitable to use a laser with a much shorter wavelength to achieve such a recording density. Therefore, a dye exhibiting good recording properties within a wavelength range of 300 to 500 nm will be required as a recording dye used in a future organic-dye type of optical recording medium.
In terms of a medium which can conduct higher-density recording than a DVD-R using an organic dye as a recording layer, JP-A 10-302310 has disclosed that a laser with an emission wavelength of 680 nm or less may be used to achieve a density corresponding to a recording capacity of 8 GB or more. The publication has suggested that a laser at 680 nm or less may be focused using an objective lens having an N.A. of 0.7 or more through a light transmitting layer with a thickness of 10 to 177 &mgr;m to achieve recording with a large capacity of 8 GB or more.
Meanwhile, there have been, as a blue laser, developed a laser at 410 nm using a GaN material and a SHG laser at 425 nm which is a combination of a semiconductor laser and an optical waveguide device (See e.g., Nikkei Electronics No.708, p.117, Jan. 26 (1998)). There have been attempts for developing a dye for a blue semiconductor laser in response to such a laser.
Since Nichia Corporation distributed samples of a GaN semiconductor laser with blue-violet emission at an emission wavelength of 390 to 430 nm from the beginning of 1999, there has been investigated a medium which has a further higher density capacity of 15 GB or more in one side and can record a moving picture for about 2 hours with an HDTV (high definition television) broadcasting quality (hereinafter, referred to as an “HD-DVD-R medium”). Such an HD-DVD-R medium with a high density capacity allow us to conduct recording for about 6 hours with image quality in current broadcasting. It has been, therefore, paid much attention as a new recording medium in place of a home VTR. A technical review of a medium using an inorganic recording film made of a phase change material has been published in Nikkei Electronics, No. 751, p.117, Sep. 6 (1999).
To date, dyes recordable with a blue laser at 400 nm to 500 nm include cyanine dyes described in JP-As 4-74690 and 6-40161; porphyrin dyes described in JP-As 7-304256, 7-304257, 8-127174 and 11-334207; polyene dyes described in JP-As 4-78576 and 4-89279; azo dyes described in JP-As 11-334204 and 11-334205; dicyanovinylphenyl dyes described in JP-A 11-304206; coumarin compounds described in JP-A 2000-43423; and pyrimidine compounds described in JP-A 2000-163799.
Other examples include an optical recording medium described in JP-A 11-53758 comprising two layers, i.e., a recording layer mainly containing, e.g., a porphyrin dye or cyanine dye as an organic dye for forming a recording layer and a metal reflecting layer mainly containing silver; an optical recording medium described in JP-A 11-203729 with an improved medium configuration which has a blue-laser sensitive dye layer comprising a cyanine dye responding to a blue laser and a red-laser sensitive dye layer to allow us to conduct recording in two wavelength regions; an optical recording medium desc
Inoue Shinobu
Koike Tadashi
Misawa Tsutami
Nishimoto Taizo
Ogiso Akira
Burns Doane , Swecker, Mathis LLP
Mitsui Chemicals Inc.
Mulvaney Elizabeth
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