Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2002-06-11
2004-05-18
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064800, C430S270140
Reexamination Certificate
active
06737143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical recording medium, an optical recording method, and an optical recording device, and particularly to an optical recording medium capable of recording information therein, reproducing the information thereof, and overwriting therein by exposing them to light beams, thereby causing a change in optical properties in the transmittance and reflectivity of the recording material constituting the media.
2. Description of the Related Art
a. Related Art Concerning an Optical Recording Medium Having Overwritable Capability (for Information Recording):
(1) A recording medium using a cyanine dye as a recording material: disclosed in Japanese Patent Laid-Open Nos. 82093/1982, 56892/1983, 112790/1983, 114989/1983, 85791/1984, 83236/1985, 89842/1985, and 25886/1986.
(2) A recording medium using a phthalocyanine dye as a recording material: disclosed in Japanese Patent Laid-Open Nos. 150243/1986, 177287/1986, 154888/1986, 246091/1986, 39286/1987, 37991/1988, and 39888/1988.
b. Related Art Concerning Compact Disc Recordable (CD-R) Which is Overwritable:
(1) Those using the combination of a cyanine dye and a metal reflective layer as a recording material: disclosed in Japanese Patent Laid-Open Nos. 159842/1989, 42652/1990, 13656/1990, and 168446/1990.
(2) Those using a phthalocyanine dye (azaanulene dye) as a recording material: disclosed in Japanese Patent Laid-Open Nos. 176585/1989, 215466/1991, 113886/1992, 226390/1992, 1272/1993, 171052/1993, 116456/1993, 268227/1995, and 314897/1995.
(3) Those using an azo metal chelate dye as a recording material: disclosed in Japanese Patent Laid-Open Nos. 46186/1992, 141489/1992, 361088/1992, 279580/1993, 51673/1995, 161069/1995, 37272/1995, 71867/1995, 231866/1996, and 295811/1996.
c. Related Art Concerning a Digital Versatile Disc Recordable (DVD-R) Having a Large Capacity:
(1) Those using the combination of a cyanine dye and a metal reflective layer as a recording material: reported in PIONEER R&D vol. 6, No. 2 (1996), “Development of DVD-Recordable” and “Fundamental Development of DVD-R dye disc”; ISOM/ODS '96 (1996), and “High Density of Recording on Dye Material Disc Approach for 4.7G”.
(2) Those using a polymethine dye as a recording material: disclosed in Japanese Patent Laid-Open Nos. 83577/1998, 119434/1998, 149583/1998, 188339/1998 and 278426/1998.
(3) Those using the combination of a polymethine dye and an optical stabilizing material as a recording material: disclosed in Japanese Patent Laid-Open No. 109475/1998, 109476/1998, 134413/1998 and 166739/1998.
(4) Those using the combination of an azo metal chelate dye and a metal reflective layer as a recording material; disclosed in Japanese Patent Publication No. 67438/1993 and Japanese Patent Laid-Open Nos. 161069/1995, 156408/1996, 231866/1996, 332772/1996, 58123/1997, 175031/1997, 193545/1998, 274732/1998, 277703/1997, 6644/1998, 6650/1998, 6651/1998, 36693/1998, 44606/1998, 58828/1998, 86519/1998, 149584/1998, 157293/1998, 157300/1998, 157301/1998, 157302/1998, 181199/1998, 181201/1998, 181203/1998, 181206/1998, 188340/1998, 188341/1998, 188358/1998, 208303/1998, 214423/1998, 228671/1998, and 12483/1999.
(5) Those using the combination of a tetraazaporphyrin (polphyrazine) dye and a metal reflective layer as a recording material: disclosed in Japanese Patent Laid-Open No. 267562/1997, 309268/1997 and 856/1998.
(6) Those using, as a recording material, the combination of a dye other than those described above and a metal reflective layer: disclosed in Japanese Patent Laid-Open Nos. 86517/1998, 93788/1998, 226172/1998, 244752/1998, 287819/1998, 297103/1998, 309871/1998, and 309872/1998.
(7) Those using, as a recording material, the combination of a cyanine dye, an azo metal chelate dye (salt forming dye) and a metal reflective layer: disclosed in Japanese Patent Publication No. 51682/1995 and Japanese Patent Laid-Open No. 34499/1999, WO98/29257, Japanese Patent Laid-Open Nos. 323478/1997, 195242/1999, 250505/1999, 168237/2000, 190641/2000, 190642/2000 and 198273/2000.
(8) Those using, as a recording material, the combination of a formazan (metal chelate) dye and a dye other than those described above: disclosed in Japanese Patent No. 2791944, Japanese Patent Laid-Open Nos. 295079/1996, 95520/1997, 193546/1997 and 337958/1998.
(9) Those using, as a recording material, the combination of a dipyrromethene (metal chelate) dye and a dye other than those described above: Japanese Patent Laid-Open Nos. 162430/1998, 166732/1998, 226172/1998, 42858/1999, 92682/1999, 165465/1998, 208111/1999, 227332/1999, 227333/1999, 255774/1999 and 256057/1999.
As described above, a number of optical recording media have been so far proposed. Now, DVD-R is under development as a next generation disc with a large capacity. To increase the recording capacity of DVD-R, development of various recording materials that can minimize the size of a recording pit, adoption of image compression techniques such as MPEG 2 and technical development to shorten the wavelength of a semiconductor laser for the recording pit reading are necessary.
An AlGaInP laser diode having a wavelength of 670 nm is the only red semiconductor laser available in the market for use in a bar code reader and a measuring instrument. With a trend toward high-density optical discs, the red semiconductor laser has been introduced into the optical storage market.
To standardize a driving system for a DVD, laser diodes having wavelengths of 630 and 670 nm are employed now for a light source. On the other hand, driving systems for a read-only DVD-ROM are put on the market, with the light sources for the driving systems having a wavelength of about 650 nm. Under such circumstances, the most preferred are DVD-R media capable of recording information therein and reading the information therefrom at wavelengths of 630 to 690 nm. A squarylium compound can be given as one example of the materials used for a recording layer of an optical recording medium which carries out recording and reading by the light pickup using a laser having a wavelength of 630 to 690 nm. The squarylium compound however is not generally suited for use in an optical recording medium because of insufficient photo stability. An azo metal chelate compound, on the other hand, can be given as one example of a dye having high light resistance. However, it involves the problem that the reflectivity is insufficient when it is used alone as a recording material.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a recording material for an optical recording medium suited for a DVD-R system using a semiconductor laser having an oscillation wavelength in a short wavelength region compared with the above-described conventional system, an optical recording medium showing excellent light resistance and shelf life, in particular, when it contains a squarylium compound; an optical recording method and an optical recording device each using the above-described optical recording medium.
The present inventors have carried out an extensive investigation. As a result, it has been found that an optical recording medium with high reliability, high reflectivity and low jitter can be provided by using a metal-chelated squarylium compound, thereby improving optical stability; by mixing therewith an azo metal chelate compound having high light resistance, thereby imparting the recording medium with higher light resistance and higher shelf life; and by using a metal-chelated squarylium compound, thereby improving the absorption coefficient of the recording medium, leading to the completion of the first and second optical recording media of the present invention.
It has also been found that an optical recording medium suitable for use in a next-generation optical disc system with a large capacity using a semiconductor laser having an oscillation wavelength of 690 nm or less and at the same time having excellent light resistance and shelf life is available by using, as a main component o
Kinugasa Motoharu
Noguchi Soh
Sato Tsutomu
Shimizu Ikuo
Tomura Tatsuya
Cooper & Dunham LLP
Mulvaney Elizabeth
Ricoh & Company, Ltd.
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