Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1999-03-31
2001-09-18
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C428S064400
Reexamination Certificate
active
06292457
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to optical media and, more particularly, to the reflecting layer typically found on recordable optical media.
DESCRIPTION RELATIVE TO THE PRIOR ART
Recordable optical media such as recordable compact disks (CD-R) and recordable digital versatile disks (DVD-R), that is data disks upon which information can be written after the manufacture thereof, are known. The media is usually in the form of a disk but can be in other forms such as optical tape or optical data cards. Recordable optical media typically have a transparent substrate, a dye containing recording layer is disposed on top of the substrate, a reflective layer is formed on top of the dye layer, and a protective layer is formed on top of the reflective layer. The transparent substrate typically has a groove on its surface. Embossing or injection molding can form the groove.
It is known to provide a dye containing recording layer wherein the dye is a metallized phthalocyanine dye. Reference is made to U.S. Pat. 5,646,273 assigned to Mitsui Toatsu Chemicals, Inc. It is also known to provide a stabilizer for such a layer as is described in U.S. Pat. No. 5,492,744 also assigned to Mitsui Toatsu Chemicals, Inc.
Typical recordable optical media use a thin layer of gold as the reflective layer. (CD-ROM or “stamped” CDs often have an aluminum reflective layer. However, since a recordable CD requires that the light pass through the dye containing recording layer during writing and reading, a higher reflectivity material, such as gold, is needed for a recordable CD.) The gold reflective layer exhibits both high stability and high reflectivity. However, gold is expensive and has recently been replaced by silver by a number of CD-R manufacturers. Silver, in addition to being much less expensive, also has a slightly higher reflectivity at the wavelength of light used by CD readers and writers. However, silver is also known to be more reactive than gold. We have found that in accelerated keeping tests, recordable CDs with silver reflective layers often display less than desired stability. Trade journals have indicated that many customers have concerns over the expected lifetime of recordable optical disks with silver reflective layers. A benchmark test of the stability of optical media is the length of time which media with data recorded on them can survive in a high temperature and humidity environment. A condition frequently selected by testers is 80° C. and 85% relative humidity. Typically, media fabricated with 100% silver as the reflective layer will work well initially but will fail this incubation condition in a time much less than media with a gold reflective layer.
In U.S. Pat. No. 5,415,914, there is described an optical recording disk having two reflecting layers. The lower layer can be “silver, gold and alloys thereof”. However, we have found that silver and gold alloys do not work with all dye containing recording layers. In fact, the reflective layers of the present invention have been tested on the layers described in U.S. Pat. No. 5,773,193 of the present assignee. The described incubation tests with the reflective layer described in this specification cause this media to fail. Other references, including those of the present assignee, also indicate that gold-silver alloys can be used but give no guidance regarding useful reflective layers that will withstand incubation.
It would be desirable to develop optical media, such as CD-R or DVD-R, with a reflective layer that would have the reduced price of silver, the high reflectivity of both silver and gold, and a stability much greater than is provided by a pure silver reflective layer.
SUMMARY OF THE INVENTION
The present invention provides a dye-based recordable optical medium such as CD-R and DVD-R with an improved reflective layer which has a reflectivity comparable to gold or silver, a cost substantially less than gold, and a stability substantially greater than pure silver.
In accordance with the present invention, there is provided recordable optical media comprising:
a) a transparent substrate;
b) a dye recording layer containing a metal complex of a porphym or phthalocyanine dye on said transparent substrate;
c) a reflective layer on said dye recording layer wherein the reflective layer comprises a mixture of silver and gold in such proportions that the gold comprises between about 0.5 and 15 atomic percent of said mixture; and
d) a protective layer on said reflective layer.
The combination of a recording layer containing a metal complex of a porphyrin or phthalocyanine type dye with the particular reflective layer provides the desired cost savings and stability.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be described in particular reference to CD-R media and disks but it will be understood that the invention is equally applicable to DVD-R disks and other dye -based recordable optical media as well.
Recordable optical media includes a transparent substrate with a dye-containing recording layer (sometimes referred to simply as a “dye recording layer”), a reflective layer, and a protective layer (or layers). Fabrication of the recordable media begins with a transparent substrate which is typically polycarbonate, formed by injection molding most often with a spiral groove embossed in one surface in the manner of commercially available CD-R's.
The substrate may be any transparent material that satisfies the mechanical and optical requirements. The substrate is generally pregrooved with groove depths from 20 nm to 250 nm, groove widths 0.2 to 1 &mgr;m and a pitch 0.5 to 2&mgr;m. As noted, the preferred material is polycarbonate. Other useful materials include glass, polymethylmethacrylate and other suitable polymeric materials.
In accordance with the present invention, the dye-containing recording layer contains a metal complex of a porphyrin or phthalocyanine dye. Suitable dyes are illustrated in Formulas I and II below;
wherein
X represents a metal selected from the group consisting of Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pd, Sn and Pb. The metals Mg, Si, V, Zn and Pd are preferred;
the R groups (1 through 12) can be the same or different and can independently be selected from hydrogen or alkyl of 1-12 carbon atoms or cycloalkyl of 6-10 carbon atoms or aryl of 6-10 carbon atoms or allyl or such alkyl, cycloalkyl, aryl and allyl groups substituted with one or more groups chosen from hydroxy, acyloxy, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkylaminosulfonyl, arylaminosulfonyl, thiocyano, cyano, nitro, halogen, alkoxycarbonyl, aryloxycarbonyl, acetyl, aroyl, alkylaminocarbonyl, arylaminocarbonyl, alkylaminocarbonyloxy, arylaminocarbonyloxy, acylamino, amino, alkylamino, arylamino, carboxy, sulfo, trihalomethyl, alkyl, aryl, substitiuted aryl, hetaryl, or substituted hetero aryl, alkylureido, arylureido, succinimido, phthalimido or,
any two of the R groups located on adjacent ring carbons may be combined together to form a 5- or 6-membered saturated or unsaturated (aromatic) hetero- or carbocyclic ring, for example R
1
and R
8
, R
2
and R
3
, R
4
and R
5
and R
5
and R
6
may form a fused ring leading to the dyes of Formula III-IV;
wherein
X represents a metal and is selected from the group consisting of Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pd, Sn and Pb. Metals Mg, Si, V, Zn and Pd are preferred;
the R groups (13 through 20) can be the same or different and can independently be selected from hydrogen or alkyl of 1-12 carbon atoms or cycloalkyl of 6-10 carbon atoms or aryl of 6-10 carbon atoms or allyl or such alkyl, cycloalkyl, aryl and allyl groups substituted with one or more groups chosen from hydroxy, acyloxy, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkylaminosulfonyl, arylaminosulfonyl, thiocyano, cyano, nitro, halogen, alkoxycarbonyl, aryloxycarbonyl, acetyl, aroyl, alkylaminocarbonyl, arylaminocarbonyl, alkylaminocarbonyloxy, arylaminocarbonyloxy, acylamino, amino, alkylamino, arylamino, carboxy, sulfo, t
Cunningham Michael P.
Preuss Donald R.
Dinh Tan
Eastman Kodak Company
Hawley J. Jeffrey
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