Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2001-03-29
2003-07-08
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064400, C428S064800, C430S270120
Reexamination Certificate
active
06589626
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to copy-protected optical information recording media and methods for manufacturing the same. More specifically, the present invention relates to the manufacture of an optically readable digital storage medium that protects the information stored thereon from being copied using conventional optical medium readers, such as CD and DVD laser readers, but permits reading of the information from the digital storage media by the same readers.
2. Background of the Invention
Optical data storage media (“optical media”) are media in which data is stored in an optically readable manner. Data on optical media are encoded by optical changes in one or more layers of the media. Optical data media are used to distribute, store and access large volumes of data. Formats of optical medium include read-only formats such as CD-DA (digital audio compact disc), CD-ROM (CD-read-only memory), DVD (digital versatile disc or digital video disc) media, write-once read-many times (WORM) formats such as CD-R (CD-recordable), and DVD-R (DVD-recordable), as well as rewritable formats such as found on magneto-optical (MO) discs, CD-RW (CD-rewriteable), DVD-RAM (DVD-Random Access Media), DVD−RW or DVD+RW (DVD-rewriteable), PD (Phase change Dual disk by Panasonic) and other phase change optical discs. Erasable, or rewritable, optical discs function in a similar manner to magneto-optical (MO) disks and can be rewritten over and over. MO discs are very robust and are geared to business applications, typically in high-capacity disk libraries.
Optical media have grown tremendously in popularity since their first introduction owing in a great deal to their high capacity for storing data as well as their open standards. For example, a commercially available magnetic floppy diskette is only capable of storing 1.44 Mb of data, whereas an optical CD-ROM of approximately the same size can have a capacity in excess of 600 MB. A DVD has a recording density which is significantly greater than a CD. For example, conventional DVD read-only discs currently have a capacity of from 4.7 GB (DVD-5, 1 side/1 layer) to 17.0 GB (DVD-18, 2 sides/2 layers), write-once DVDs a capacity of 3.95 GB (DVD-R, 1 side/1 layer) to 7.90 GB (DVD-R, 2 sides/1 layer) (newer DVD-Rs can hold up to 4.7 GB per side), and conventional rewritable DVDs of from 2.6 GB (DVD-RAM, 1 side/1 layer) to 10.4 GB (MMVF, 2 sides/1 layer). Optical discs have made great strides in replacing cassette tapes and floppy disks in the music and software industries, and significant in-roads in replacing video cassette tapes in the home video industry.
Data is stored on optical media by forming optical deformations or marks at discrete locations in one or more layers of the medium. Such deformations or marks effectuate changes in light reflectivity. To read the data on an optical medium, an optical medium player or reader is used. An optical medium player or reader conventionally shines a small spot of laser light, the “readout” spot, through the disc substrate onto the data layer containing such optical deformations or marks as the medium or laser head rotates.
In conventional “read-only” type optical media (e.g, “CD-ROM”), data is generally stored as a series of “pits” embossed with a plane of “lands”. Microscopic pits formed in the surface of the plastic medium are arranged in tracks, conventionally spaced radially from the center hub in a spiral track originating at the medium center hub and ending toward the medium's outer rim. The pitted side of the medium is coated with a reflectance layer such as a thin layer of aluminum or gold. A lacquer layer is typically coated thereon as a protective layer.
The intensity of the light reflected from a read-only medium's surface by an optical medium player or reader varies according to the presence or absence of pits along the information track. When the readout spot is over the flat part of the track more light is reflected directly from the disc than when the readout spot is over a pit. A photodetector and other electronics inside the optical medium player translate the signal from the transition points between these pits and lands caused by this variation into the 0s and 1s of the digital code representing the stored information.
A number of types of optical media are available which permit an end-user to record data on the media, such optical media generally are categorized as “writable” or “recordable,” or “re-writable.”
“Writable” or “recordable” optical media (e.g., “CD-R” discs) permit an end-user to write data permanently to the medium. Writable media are designed such that laser light in the writer apparatus causes permanent deformations or changes in the optical reflectivity of discrete areas of the data layer(s) of the medium. Numerous writable optical media are known, including those that employ a laser deformable layer in their construct upon which optically-readable areas analogous to the pits and lands found in conventional read-only optical media can be formed (See, e.g., EP-A2-0353391), those that employ a liquid-crystalline material in their data layer(s) such that irradiation with the laser beam causes permanent optical deformations in the data layer (See, e.g., U.S. Pat. No. 6,139,933 which employs such layer between two reflective layers to effect a Fabry-Perot interferometer), and those that utilize a dye that irreversibly changes state when exposed to a high power writing laser diode and maintains such state when read with a low power reading laser (so-called, WORM, write-once-read-many times, optical media).
Rewritable optical media (e.g., “CD-RW”, “DVD-RAM”, “DVD−RW”, “DVD+RW” and “PD” media) use the laser beam to cause reversible optical deformations or marks in the data layer(s), such that the data layer is capable of being written on, read, erased and rewritten on many times. Several rewritable optical media systems are known.
In one system, an optically-deformable data layer is deformed in discrete areas by the writing laser to form optical changes representative of the data, for example, pits and lands, and erased by uniformly deforming the same optically-deformable data layer, or the portion thereof wherein the data desired to be deleted is found. In another system, a photochromic material layer is used to store the data. In this system, the photochromic material reversibly changes when the material is irradiated by light possessing certain wavelengths. For example, a colorless compound may change its molecular state to a quasi-stable colored state when irradiated by ultraviolet (UV) light, yet be returned to the colorless state upon exposure to visible light. By selectively irradiating the photochromic material layer with the one wavelength to cause an optical change, and then irradiating with the other wavelength to reverse such optical change, one is permitted to write, erase, and re-write data.
Materials that changes color due to a change in crystalline state have been found to be particularly useful in re-writable media. In one system, a material which is dark in the amorphous state, but bright in the crystalline state, is used to record the data. In such system, dark amorphous marks are formed utilizing a short high-power laser pulse that melts the recording material followed by quenching to temperatures below the crystalline temperature. The data formed thereby, can be erased by heating the amorphous state over a long enough period of time between the temperature of crystallization and temperature of melt to regain the crystalline state. Ternary stoichiometric compounds containing Ge, Sb and Te (e.g., Ge
1
Sb
2
Te
4
Ge
2
Sb
2
Te
5
) are in particular known to show a large optical contrast between amorphous and crystalline phase and have acceptable melting temperatures (t
cryst
=about 150-200° C., t
melt
=about 600° C.). Alloys of such compounds with antimony (Sb), cadmium (Cd) and tin (Sn) have also been employed in rewritable media.
In rewritable optical
Drew Jeffrey M.
Selinfreund Richard H.
Vig Rakesh
Mulvaney Elizabeth
Verification Technologies, Inc.
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