Note: Descriptions are shown in the official language in which they were submitted.
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DISPOSABLE OPTICAL STORAGE MEDIA AND MANUFACTURING METHOD
BACKGROUND OF THE INVENTION
Relationship to Co-Pending Applications:
This application claims priority under 35 U.S.C. 119(e) to Provisional
Application
Serial No. 60/143,474, filed July 12, 1999. This application is related to
International
Application Serial No. PCT/US00/07961, filed March 23, 2000; Provisional
Application
Serial No. 60/125,927, filed March 23, 1999; Provisional Application Serial
No.
60/128,197, filed April 7, 1999; U.S. Application Serial No. 09/507,490, filed
February
18, 2000; and U.S. Application Serial No. 09/507,224, filed February 18, 2000.
Each of
the above-identified applications is incorporated herein by reference in its
entirety.
1. Field of the Invention
The invention relates generally to the field of optical media. More
particularly, the
invention relates to time sensitive disposable optical media.
2. Discussion of the Related Art
Optical disks such as CDs and DVDs are sold and rented to consumers for use at
home. The content of the optical disks may be music, movies, software or data.
Unfortunately, the purchase of CDs and DVDs can be expensive. The cost is
associated
not primarily with the manufacturing cost of the optical disks, but with the
value of the
information, such as movies or software, encoded on the disks. Content
providers, such as
movie studios or software companies, do not want to sell at a low cost copies
of their
material that will have a long lifetime in the marketplace. Rentals of CDs and
DVDs
enable consumers to access the information at a lower cost, but the need to
return the
rentals on time is inconvenient. It would be desirable to have an optical
media (e.g., disk)
that the user could purchase at a low cost, would address the concerns of the
content
providers about lifetime of their content in the marketplace, and which would
not have the
disadvantage of having to be returned, as is the case with videotape movie
rentals today.
It would also be desirable to manufacture such an optical disk at low cost and
with
minimum changes to existing optical disk manufacturing processes.
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CDs and DVDs are generally manufactured according to the following process.
This information was downloaded from the web site of Disctronics Manufacturing
(UK)
Ltd., Southwater Business Park, Southwater, West Sussex, England on January
26, 1999,
and has been slightly edited.
3. CD Mastering
Mastering of CDs and CD-ROMs is a complex process needed to create a
stamper (used to mould the CDs) from the premastered data. The processes are
carried out in a class 1,000 clean room. Operators wear special clothing
including
face masks and footwear to minimize any particles.
4. Glass Master Preparation
1 S Glass Master Preparation of the 240 cm diameter 6mm thick glass master
starts by stripping the old photo resist from its surface (since the glass
blanks can
be recycled). This is followed by cleaning and final washing using de-ionized
water. The blank master is then dried carefully ready for the next stage.
The surface of the clean glass master is then coated with a primer and then
a photo resist layer 140 to 150 microns thick by spin coating. The thickness
should
be matched to the molding cycle time. Shorter cycle times imply a thicker
resist
layer to ensure good pit geometry. The uniformity of the layer is measured
with an
infra red laser.
The photo resist coated glass master is then baked at about 80° C
for 30
minutes. This hardens the photo resist layer ready for exposing by laser
light.
(a) Laser Beam Recording
A Laser Beam Recorder (LBR) is used to expose the photoresist layer on
the glass master where the final pits are required.
This is carried out in a class 100 controlled environment using a high power
gas laser directly from the premastered source audio or CD-ROM data. The laser
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can be blue, violet or (for DVD and CD mastering) ultra violet. The laser beam
is
modulated to expose the photoresist where pits should be while the glass
master
spins at exactly the correct linear velocity and is moved gradually and
smoothly to
maintain the correct track pitch and linear velocity.
The LBR is controlled by a PC based system which formats the data from
the source CD, U-matic or Exabyte tape with the CIRC error protection and EFM
modulation. If an error occurs which cannot be corrected during mastering the
controller will abort recording.
Speed of laser beam recording depends on the machine and input media.
At one time when every CD was audio, U-matic was the only media used and only
allow single speed mastering. Other newer media allow faster mastering up to 4
times, with even faster speeds possible. The following table summarizes the
mastering speeds for different media.
1 S Input Media Speed Comments
U-matic (1630) lx Still in use but is gradually being phased out.
Audio data is often transferred offline to a faster
format before mastering
DAT 1 x Not a preferred format for mastering
CD 4x Faster if LBR capable
CD-R 4x Depends on quality of CD-R media used and
speed of LBR
8mm Exabyte 8500 2.8x Max speed of Exabyte
8mm Eliant 820 4x Faster if LBR capable
Hard disk 4x Faster if LBR capable
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The absolute limit of speed is dictated by the robustness of the glass. For
240 mm glass plates, the practical limit is around 6x for CD mastering.
Network mastering is a new development whereby the data content of
Exabytes, CDs etc (containing the audio or other data) is transferred to a
server and
mastering carried out from this data (which can be checked prior to mastering)
via
a high speed network. Several LBRs can be connected to the network and
mastering jobs can be scheduled in advance. The result is higher speed, more
reliable mastering.
(b) Development & Metallization
The exposed photoresist surface is developed to remove the photoresist
exposed by the laser and therefore create pits in the surface. These pits
should
extend right through the photoresist to the glass underneath to achieve good
pit
geometries as specified in the Red Book. The glass itself is unaffected by
this
process and acts merely as a carrier for the photoresist.
The active surface (i.e. containing pits) of the developed glass master is
then metallized either with nickel or nickel alloy created by sputtering or
with
silver by evaporation. If nickel or nickel alloy is used this becomes part of
the
Father which is created by electroforming so the pit geometry is maintained.
If
silver is used, the nickel Father is grown on top of the silver resulting in
some
distortion of the pit shapes, but this is not usually enough seriously to
impair the
resultant pits.
(c) Electroforming
This involves creating nickel fathers, mothers and stampers by
electroforming in a class 1000 clean room environment.
The father is electroformed from the metallized glass master and then the
surface containing the 'bumps' is oxidized ready for the next stage. (This
allows the
mother to be separated from the father).
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The mother is then electroformed from the father and is an essential
intermediate stage from which the stamper(s) are then electroformed in a
similar
way.
After the mother has been created, the father can then be used as a stamper.
Only mothers are needed for subsequent stampers. Additional stampers are
created
for long runs of CDs.
The photoresist on the glass master is then removed and the glass cleaned
ready to be used again. If silver is used, it is recovered and recycled.
(d) Stamper Finishing
When the stamper has been electroformed from the mother, it requires
finishing before any discs can be replicated from it.
Each stamper is checked visually, the back polished, it is punched to the
required outside diameter, a hole accurately punched in the center and finally
it is
checked on a stamper player before being fitted to the press.
Stamper finishing is an important stage as it will affect the quality of the
final disc. The center hole must be accurately cut to avoid eccentricity which
could
affect the playability of CD-ROMs using modern high speed CD-ROM drives.
Also the stamper thickness must be uniform to avoid unbalance problems in the
finished discs.
Finished stampers are stored in protective plastic packages ready to be
fitted to a molding machine.
5. CD Replication & Printing
CD Replication Overview
Compact Discs, whether audio or CD-ROM, are manufactured in the same
way using the following processes:
~Injection molding of the clear polycarbonate discs using a hydraulic press.
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~Metalising to create an aluminum reflective surface
~Lacquering to protect the back of the reflective surface
~Printing of the disc label on top of the lacquer.
(a) Replication Lines
The replication of CDs in the past has been carried out using batch
processes where each stage of the process uses a different machine. In the
last few
years integrated replication lines have become the norm. Examples of such
machines are:
Single-line
A complete replication line comprising molding machine, metallizer,
1 S lacquer unit, printer (normally 3 color) and inspection. Good and bad
discs are
transferred to different spindles. Finished discs are removed on spindles for
packing.
An alternative to this does not include a printer. This allows a new job to
continue without being stopped while the printer is being setup.
Dual-line
A replication line comprising two molding machines, metallizer, lacquer
unit and inspection. This provides a better match between molding machine and
downstream equipment cycle times and is currently the most flexible solution.
Each molding machine can run different titles, the discs being separated after
inspection and placed on different spindles. Also called Duoline.
(b) Injection Molding
Optical grade polycarbonate is 'baked' to remove any moisture and is
injection molded in a high pressure molding machine (press) using the stamper
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mounted in the mould fixed to the press. This mould is in two parts and
provides a
cavity which ensures that perfectly molded discs are produced with the correct
dimensions every time. One half of the mould contains the stamper while the
other
half contains the mirror block to ensure a smooth surface.
The hydraulic press applies a force to the two halves of the mould which
are closed. Molten polycarbonate is then injected into the cavity and held in
place
by the applied pressure while the disc cools and solidifies. Pressed discs,
after
cooling, are transferred by robot arms to a spindle for the next stage in the
process.
Successful molding of CDs which meet the CD specification, require stable
processes with the machines setup correctly. Molding parameters which can
affect
the resultant CD include stamper geometry, mould temperature, polycarbonate
temperature, compression force and cycle time.
Cycle times for injection molding have decreased substantially from over
I O seconds some 10 years ago to under 4 seconds for the latest presses and
moulds. Cycle times of under 3 seconds are also becoming possible.
(c) Metallizing
The polycarbonate discs after molding are transparent. In order that the
laser can read the pits they need to be covered by a mirror surface to reflect
the
laser light.
The next stage is therefore to metalize the active surface of each disc with
aluminum by sputtering. Sputtering requires the transparent polycarbonate
discs to
be transferred to the sputtering chamber which is then quickly evacuated of
air and
filled with argon gas. The argon ions are attracted to the aluminum target by
the
use of a high voltage. As the ions strike the target, particles of aluminum
are
ejected and are deposited onto the CD surface.
Modern metalizers are capable of cycle times of under 2 seconds allowing
them to be used in duolines where one metallizer can handle the output from
two
molding machines. The fastest metallizers can achieve cycle times of 1.5
seconds.
(d) Lacquering
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The back of the aluminum layer is protected by a lacquer which is spread as
a liquid evenly across the surface of the disc by spin coating. The
centrifugal force
created by spinning the disc ensures that the lacquer covers the whole disc in
an
even layer.
It is important that the lacquer overlaps the aluminum therefore sealing it
from the elements. If left exposed, aluminum will start to oxidize within a
few
days.
The lacquer is cured by ultra-violet (UV) light producing a hard protective
surface. The discs are then ready for printing.
Lacquering involves two steps in the spin-coating process, lacquer
deposition and spin-off. Cycle times of under 2 seconds are normally achieved
by
either splitting the two steps into two stations or using two spin coating
stations.
1 S (e) Label Printing
The upper surface of a finished disc is printed with up to five colors by a
flat silk screen process. Each color requires a different screen created from
label
films produced as color separations from the artwork. Each color is printed
using a
squeegee which pushes the ink through the mesh of the screen on to the disc
surface. The inks are then cured using UV light to produce a durable surface.
For picture discs five colors are needed. These are white for the base, plus
cyan, magenta, yellow and black (CMYK). Very high quality printing can be
achieved using modern printing machines, which are capable of speeds of 70
discs
per minute or faster.
Automatic checks are carried out during this stage to ensure that all discs
being printed carry the correct catalogue number which is placed on the disc
hub
during mastering.
6. DVD Manufacture
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DVD discs are more difficult to manufacture than CDs, requiring new,
purpose designed equipment rather than upgraded equipment. DVD discs are
different from CDs in the following ways:
~Shallower pits and smaller pit size
~Smaller track pitch and tighter tolerances
~Higher mastering speeds, both in angular and linear velocity and data rate
~New data formatting requirements
~Thinner disc substrates to mould
~Tighter tolerances on tilt and fitter in particular
~Additional bonding stage
~Dual layer and double sided options
(a) DVD Mastering
The differences between DVD and CD means that much of the mastering
process for DVD needs new equipment including improved glass master
preparation, laser beam recording and developing. The photo-resist layer
should,
ideally be about 120 nm in thickness (instead of 140 nm for CD) but successful
mastering using the same thickness as for CDs is possible. Any defects or
variations in thickness of this layer must be kept very small. Laser beam
recording
requires a smaller spot size, higher numerical aperture and tighter tolerances
than
for CDs. Many LBRs designed for DVD mastering use a UV laser (instead of the
blue or violet laser used for CDs). To handle CD and DVD mastering, it is
necessary to change the numerical aperture from 0.6 for CD to 0.9 for DVD
mastering.
DVD data is formatted differently from CDs and requires new formatting
hardware/software to handle the RSPC error correction, 8 to 16 modulation and
the
higher channel data rate.
Stamper finishing requires more care than for CDs, since tilt (variations in
flatness of the final disc) is critical for DVD.
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DVD-9 (dual layer) discs require the upper layer (layer 1) to be mastered
with the turntable rotating in the reverse direction. Also, the direction of
writing
will be either from the inside to outside (parallel track) or outside to
inside
(opposite track), depending on the application requirements.
CSS (Content Scrambling System) copy protection is carried out at the
mastering stage. The data on DLT is combined with the encrypted keys and the
audio and video data scrambled using the keys which are hidden on the DVD
disc.
(b) DVD Replication
DVD-S and DVD-10 were the first discs to be manufactured. DVD-9 has
proved to be considerably more difficult and there is a shortage in
manufacturing
capacity for these dual layer discs. All DVD discs comprise two substrates
each
0.6mm thick and molded separately.
1 S ~For DVD-5 discs, the active substrate is metallized and then bonded with
the blank, non-metallized substrate.
~For DVD-10, both substrates are metallized
~For DVD-9 discs two metalization layers are required, one being semi-
reflective, using gold or silicon. Parameters such as tilt, bonding layer
transparency etc are more severe for DVD-9. Also the layer 1 aluminum layer
must be uniform in thickness to avoid fitter.
DVD molding is similar to CD molding but with some important
differences.
~Two pressings are needed for each final DVD disc
~Each half disc (substrate) is 0.6mm thick instead of 1.2mm
~The thinner disc also requires different molding parameters, such as a
shorter injection time and higher mould temperature.
In general, new or redesigned mounding machines are needed for DVD.
(c) DVD Bonding
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Bonding is one of the most difficult parts of the process. There are a
number of possible solutions.
~Hot melt bonding is the method used for Laserdiscs where the two
substrates just need to be glued together. It is also suitable for single
layer (single
or double sided) DVDs. The process is simple and relatively inexpensive.
~Radical UV Cured bonding is suitable for dual layer discs because it is
transparent. It involves coating one or both of the substrates with a UV cured
resin
similar to normal lacquer.
~Cationic UV Bonding involves screen printing the resin over both
substrates, curing each with UV light and then pushing the discs together.
This
method is not suitable for dual layer discs as the resin used is opaque.
Disctronics use Radical UV Cured bonding which is compatible with all
DVD formats. DVD-9 bonding is particularly difficult as the bonding layer must
~be of uniform thickness within close tolerances
~be optically transparent with no defects such as bubbles
~not introduce tilt outside the DVD specification
(d) DVD Disc Finishing
Finishing comprises label printing, for which there are a number of options,
and adding the Burst Cutting Area.
Printing options DVDS DVD9 DVD10
Normal printing on upper surface
Of disc (like CDs) Yes Yes No
Printing on inside surface of
blank substrate to give smooth
'glossy' effect Yes No No
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Pit Art where a holograph like
Image is molded into the blank
Substrate Yes No No
S Printing on both sides but only
Within hub area -- -- Yes
Burst Cutting Area (BCA) is an annular area within the disc hub where a
bar code can be written for additional information such as serial numbers.
DVD Quality Assurance
DVD inspection and testing requires the use of some different techniques,
new parameters to be tested and new readers.
~DVD glass mastering must be checked using a DVD stamper player to
check the stamper prior to replication.
~DVD inspection is similar to CD inspection but includes tilt. Discs must
be inspected after bonding as this stage can introduce tilt and other defects.
DVD-
10 discs need inspection of both top and bottom of each disc.
~DVD bit verification needs new equipment to read the data.
~DVD measurements again need new equipment plus new and modified
tests.
7. CD Packaging
There is a wide range of packaging available for audio CDs and CD-ROMs
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~Jewel case (the most common) comprises a transparent plastic case with
hinged lid, a plastic tray, inlay card and booklet.
~Slimline cases, a slimmer version with no tray, for audio singles.
~Card wallets and many other cases available.
~A range of outer packaging is used particularly for CD-ROM discs e.g. to
hold a printed manual.
(a) Machine Packing
Discs are packed in standard jewel or slimlines cases with paper parts by
automated machines and overwrapped and packed into boxes as required.
~The machine automatically takes each case and opens it ready for the disc
to be inserted.
~A robot arm transfers the printed discs from spindles and places them in
the opened cases.
~Booklets are fed to the machine by another robot arm and placed in the
jewel cases. Some machines are capable of handling two booklets per CD.
~The packaged CD can have stickers automatically added and, optionally,
can be over-wrapped.
Machines operate at speeds up to 100 CDs per minute or more. For smooth
operation at these speeds it is essential that cases and paper parts adhere to
the
specified dimensions and other physical properties.
United States Patent 5,815,484 to Smith, et al. issued on September 29, 1998
discloses a composition and method for meeting the needs stated in the Utility
section
above.
To quote Smith et al., the currently used optical disk systems operate as
follows:
In a typical optical disk for use in a computer's optical readout system, data
is
stored as a series of lands and pits. This is accomplished by stamping along
spiral
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tracks on a transparent plastic disk, overlaying this with a reflective
coating, and
thereafter superimposing a protective layer over this coating. Light from a
semi-
conductor laser is directed toward the lands and pits from below and the
reflected
light impinges upon a photodetector which converts the presence or absence of
the
pits into a binary electrical signal. Because the focused laser spot is so
minute, the
amount of information that can be stored onto the surface of the disk is
immense.
Adjacent tracks need only be spaced apart by approximately 1.6 microns and,
hence, approximately 40,000 tracks may be available on a conventional 120 mm
diameter (5 inch) optical disk. The electrical signals delivered to the
optical
readout system correspond to the magnitude of reflected light which either
increases or decreases due to interference and/or diffraction by the
preformatted
data structures.
Smith et al accomplish the goals stated above by placing an additional layer
over the
1 S protective layer. Again, quoting Smith:
More particularly, an optical disk is provided which is adapted for use in an
optical readout system of a computer that includes a light source operative to
produce an interrogating beam of light for reading data structures. Broadly,
the
optical disk according to the present invention includes a substrate and a
metallic
layer encoded with information stored as a plurality of data structures that
are
readable by the interrogating beam of light. The substrate is disposed in a
confronting relationship with the metallic layer, and a film of a reactive
compound
is superimposed over at least some of these data structures. The reactive
compound
is selected to be of a type which is operative to change physical
characteristics in
response to a selected stimulus, thereby to affect readability of the data by
the
interrogating beam.
The reactive compound is disposed between the light source's interrogating
beam and the metallic layer. This reactive compound may be interposed between
the substrate and the metallic layer and have a thickness in a range of 0.1-10
microns, and preferably 1-5 microns. Alternatively, it may be disposed on an
outer
surface of the substrate. The metallic layer is preferably contoured to
include a
sequence of pits and lands which define the plurality of data structures, with
the
reactive compound superimposed over at least some of these pits and lands.
The selected stimulus to which the reactive compound responds is selected
to be either visible light, infrared light, an ambient environment containing
light
and oxygen, or simply air. Where the stimulus is light alone, the reactive
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compound may be a photoreactive material and preferably one selected from a
spiropyran class of photochromic compounds --for example, 6-nitro-1'3'3'-
trimethylspiro-(2H-lbenzothiopyran-2,2'-indoline), or 6-nitro-1 -S-BIPS for
short,
and other related compounds.
Where the stimulus is a combination of light and oxygen, the reactive
compound would therefore be photoreactive with oxygen and preferably operate
to
change its physical characteristics in response to an interrogating beam of
light
having a wavelength of approximately 650 nanometers (nm), which is encountered
with digital versatile disk (DVD) readers.
Where the environmental stimulus is simply air, the reactive compound
may be one which is operative after an accumulated duration of time to oxidize
and
alter an optical characteristic thereof. For example, such a reactive compound
would change from an optically transparent condition to an optically opaque
condition wherein it absorbs light having a wavelength within a desired range.
This
wavelength could be either 650 nanometers (nm), as discussed above, but may
also
be approximately 780 nanometers (nm). The oxidizing reactive compound may be
selected from a group of dyes consisting of methylene blue, brilliant cresyl
blue,
basic blue 3 and toluidine blue 0.
Smith et al also teach packaging of the disk in an inert environment:
For example, such an optical disk would preferably be contained in a package
in
the form of an aluminum bag coated with polyethylene. Within the hermetic
packaging would be an inert gaseous environment, such as argon or dry
nitrogen.
Heretofore, the requirements of low cost, limited content lifetime, avoidance
of
rental returns and minimum changes to existing manufacturing precesses
referred to above
have not been fully met. What is needed is a solution that simultaneously
addresses all of
these requirements. The invention is directed to meeting these requirements,
among
others.
SUMMARY OF THE INVENTION
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A goal of the invention is to simultaneously satisfy the above-discussed
requirements of low cost, limited content lifetime, avoidance of rental
returns and
minimum changes to existing manufacturing processes which, in the case of the
prior art,
are not simultaneously satisfied.
One embodiment of the invention is based on an optical disk, comprising: a
substrate; a metal layer coupled to said substrate; and a lacquer coupled to
said metal
layer, wherein optical properties of said substrate change upon an exposure of
said
substrate to air, said exposure degrading readability of data recorded on said
optical disk.
Another embodiment of the invention is based on a package containing an
optical disk,
said optical disk comprising: a substrate, a metal layer coupled to said
substrate; and a
lacquer coupled to said metal layer, wherein opening said package triggers a
process that
changes optical properties of said substrate, thereby degrading an ability to
read data
recorded on said optical disk.
Another embodiment of the invention is based on an optical disk, comprising: a
substrate; a metal layer coupled to said substrate; and a lacquer coupled to
said metal
layer, wherein at least one member selected from the group consisting of said
substrate
and said lacquer permit controlled exposure of said metal layer to air,
thereby degrading
readability of data recorded on said optical disk. Another embodiment of the
invention is
based on a package containing an optical disk, said optical disk comprising: a
substrate, a
metal layer coupled to said substrate; and a lacquer coupled to said metal
layer, wherein
opening said package triggers a process that changes reflective properties of
said metal
layer, thereby degrading an ability to read data recorded on said optical
disk.
In improvement to Smith et al, we have recognized that the use of one or more
extra layers on the disk may be augmented with additional techniques to
achieve the
required results. Furthermore, in contrast to Smith et al, we have recognized
that for
optical disks containing a "directory" or "table of contents" area, it is
advantageous to
disable said directory area rather than the entire surface of the optical
disk. Furthermore,
in contrast to Smith et al, we have recognized that a change in the physical
structure of the
disk, such as warping or enlargement of the central playing hole, can be used
to render the
disk unplayable, rather than a change in the disk's optical properties.
Finally, in addition
to the mechanisms identified by Smith et al, we have invented new mechanisms
to trigger
the process that inhibits playing the disk, such as a user action or the
centrifugal force
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resulting from playing the disk. In one embodiment, our invention consists of
a "trench"
or set of pores over the table of contents area is filled with a material that
turns opaque or
cloudy upon exposure to oxygen or other substances in the environment.
Similarly,
removal of the disk from a controlled environment (e.g., inside the packaging)
could
S gradually render the disk unplayable. For instance, at a coating or
substrate might be
transparent in a hydrogen environment but gradually become opaque or cloudy in
most or
all other environments including normal air.
We define the "substrate" to be the one or more layers through which the laser
light passes before impinging on the metal layer. Currently the substrate
layer is
polycarbonate or PMMA, but other materials known to those skilled in the art
may be
used.
We define the "lacquer" to be the layer or layers not in the path of the laser
light
during the process of reading data from the disk. One or more of these layers
may be
1 S composed a material identical or similar to the one used for the
substrate. The laser light
is not intended to pass through the lacquer. Typically a one-sided disk (such
as a CD or a
DVD-5) will have a reflective metal layer between the substrate and the
lacquer. In a two-
sided disk (such as a DVD-10), the lacquer will typically include a layer
binding together
the two sides of the disk.
One aspect of our invention consists of attacking solely, primarily or first
the table
of contents (or directory) information on an optical disk. This could be
achieved by
several approaches, such as a coating, modifying the properties of the
substrate, or
damaging the metal layer. Benefits include higher manufacturability because a
smaller
part of the disk may need to be rendered inoperable, and more abrupt
deterioration, as
instead of deteriorating parts of the video content on a DVD, possibly in a
gradual process,
attacking the table of contents will prevent the player from accessing entire
sections of the
video content, and render the disk unplayable in a relatively sharp time
frame. This is
likely to be preferable to having an extended period during which the disk is
playable, but
not at full quality. It should be noted that because of the much stronger
error correction in
the table of contents, previous approaches such as Smith et al, would likely
result in the
table of contents failing last. Our invention recognizes, however, the benefit
of having the
table of contents fail first. In order to make the table of contents (or any
other part of the
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disk) more vulnerable the disk could be mastered with a lower level of error
correction in
this region, a small set of errors could be intentionally introduced in
mastering or
manufacturing, or a substrate or coating could be used which already was less-
than-
perfectly readable.
S In a further improvement to other proposed approaches, an aspect of our
invention
consists of increasing the thickness of the material that interferes with
reading of the
optical data. For instance instead of a coating of a few microns, our
invention would
allow a layer of material up to the thickness of the substrate, possibly
reaching all the way
to the metal layer. That would facilitate interfering with the reading laser.
For example, it
would make it easier to absorb or reflect enough laser light to prevent the
laser from
reading the data on the disk. It would also make it substantially more
difficult for a user to
defeat this mechanism by polishing off a thin coating, either mechanically or
through the
use of a solvent. In one embodiment, this invention would consist of pores or
trenches of
appropriate dimensions that are imprinted on the substrate during the molding
process, by
1 S using a specially engineered molding plate instead of the standard flat
plate ("mirror"). In
another embodiment the shape of these pores or trenches would help prevent the
reading
of data. For example, a trench (or set of pores) with angled walls over the
directory area
of a DVD could be filled with a material that changes its refractive index
upon exposure to
the environment, or physically shrinks allowing air, other gases or vacuum to
fill in the
gap, or expands. In any of these cases, after the change in the filling
material occurs, the
laser beam may be reflected at the boundary of the trench or its interior,
thus being
prevented from reliably reading the data on the disk.
In another aspect of our invention, small bubbles, crystals, particles or
cracks could
form in the coating or substrate, making the data unreadable. For instance a
substance (in
gas, solid or other state) could gradually precipitate or otherwise separate
from other parts
of the disk and thereby create interference for the light beam. In addition to
potentially
being easier to achieve than a uniformly increasing opacity, this approach may
more
successfully interfere with the readability of the disk.
In another aspect of our invention, user action triggers the process of
destroying
information. One embodiment would place a cover on the data side of the disk,
over the
table of contents/directory area, or over the entire area, or over part
thereof. The user
would need to remove the cover to play the disk. Removal of the cover would
trigger the
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process that renders the disk unreadable. For example, it could expose an
oxidizing
coating, or would release a substance that starts a chemical reaction
affecting the substrate
and/or the metal layer. The substance could be released by breaking
microcapsules on the
cover itself or on the disk. The cover itself might provide the only barrier
protecting the
coating or the substance from the environment, or it could do so in
combination with other
means, such as airtight packaging in an inert environment. The cover might be
an
adhesive label, special printing or other type of barrier.
In another embodiment, a water-soluble opaque substance over the table of
contents or the entire surface of the disk would prevent the disk from being
played. The
user would need to wipe off with a wet cloth this substance, in order to make
the disk
playable. The water and moisture would then trigger the process that renders
the disk
unplayable. Other embodiments could require user actions such as heating or
cooling the
disk, squeezing or shaking, exposing to microwave radiation in a microwave
oven,
exposure to bright light, exposure to ultraviolet light dipping in water or
other substances,
wiping or otherwise exposing the disk to some chemical, or removing or
changing some
component of the disk. The users actions would relatively quickly render the
disk
(temporarily) playable. However, they would also set in motion a different and
effectively
irreversible sequence or set of reactions which eventually render the disk
unplayable. The
advantage of this general strategy is that instead of relying only or
primarily on relatively
passive environmental conditions to render the disk unplayable, our invention
leads the
user to take a more drastic action which may provider a sharper starting point
for the time
period before the disk becomes unplayable and expand the set of reactions and
approaches
which can be considered.
The disk could be made unplayable without changing its optical properties, by
changing its mechanical/physical properties. In one embodiment, a DVD disk
consisting
of two substrates could be warped by uneven expansion or other physical
changes in the
two substrates, or by expansion or other physical changes in an adhesive
layer, or by
expansion or other physical changes in a specially placed layer that changes
upon
exposure to moisture or content. In another embodiment, the disk might be
rendered
unplayable through fractures, either because of thereby induced mechanical
failure or
because of interference of these fractures with the ability of the laser to
read the encoded
data. In another embodiment, the central hole could be enlarged, possibly as a
result of
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materials that deteriorate either with exposure to the environment or because
of the
mechanical stresses of playing (for example, DVDs rotate at speeds up to 1600
rpm).
Playing a DVD on a standard player involves rotation at speeds up to 1600 rpm.
Mufti-speed DVD drives may utilize even higher speeds. This rotation could
provide the
triggering and/or sustaining mechanism for the process that renders the disk
unplayable.
For example, rotation at these speeds results in high centrifugal forces,
similar to a mini-
centrifuge. In one embodiment, these centrifugal forces could trigger the
diffusion or
mixing of substances that cause the disk to be unplayable. In another
embodiment,
microcapsules would break when exposed to sustained centrifugal forces, and
trigger a
reaction resulting in rendering the disk unplayable. For example, binary
substances could
react to produce an opaque substance interfering with reading of the optical
data, or a
reactive agent or a catalyst could be released that attacks the metal layer or
the substrate.
One approach would be to put such substances in small radial, spiraling or
circular
trenches or tubules in the disk.
These, and other, goals and embodiments of the invention will be better
appreciated and understood when considered in conjunction with the following
description
and the accompanying drawings. It should be understood, however, that the
following
description, while indicating preferred embodiments of the invention and
numerous
specific details thereof, is given by way of illustration and not of
limitation. Many
changes and modifications may be made within the scope of the invention
without
departing from the spirit thereof, and the invention includes all such
modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
A clear conception of the advantages and features constituting the invention,
and of
the components and operation of model systems provided with the invention,
will become
more readily apparent by referring to the exemplary, and therefore
nonlimiting,
embodiments illustrated in the drawings accompanying and forming a part of
this
specification, wherein like reference characters (if they occur in more than
one view)
designate the same parts. It should be noted that the features illustrated in
the drawings
are not necessarily drawn to scale.
FIGS. la-lb illustrate schematic side views of an optical disk, representing
an
embodiment of the invention.
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FIGS. 2a-2b illustrate schematic side views of another optical disk,
representing
another embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
The invention and the various features and advantageous details thereof are
explained more fully with reference to the nonlimiting embodiments that are
illustrated in
the accompanying drawings and detailed in the following description of
preferred
embodiments. Descriptions of well known components and processing techniques
are
omitted so as not to unnecessarily obscure the invention in detail.
The context of the invention includes reading data from an optical media.
Optical
disks represent a generic class of optical media. The sub-generic class of DVD-
ROM can
contain any digital information. DVD-Video is based on DVD-ROM standard and
also on
the standards represented by MPEG-2 and Dolby Digital. The invention can
utilize data
processing methods that transform signals produced from the data encoded on
the optical
media so as to actuate interconnected discrete hardware elements; for example,
to start,
stop and/or actuate other functions of the media reader (device) that is
accessing the data
on the optical media.
The concept of the invention includes disposable optical media, such as, for
example time-sensitive disposable digital video disk (DDVD). A DVD could be
manufactured or packaged in such a way that it can only be used for a limited
time period
or a limited number of uses.
The DVD could react with oxygen in the air so that once it was removed from an
air-tight package, the surface would obscure a fraction of the underlying
data. For
instance, some plastics may be come cloudy, or black.
The DVD could react with other constituents of air such as moisture or other
gases
so that once it was removed from an air-tight package, the surface would
obscure a
fraction of the underlying data. Again, some plastics may be come cloudy, or
black.
The DVD could react to light, such as the laser light that is used to read
data, so
that it could not be read again after some number of readings. This could be a
photochemical process similar to photography or the clouding of a substance
when
exposed to light.
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The DVD could react to ambient room light so that it could not be read again
after
some number of readings. Again, this could be a photochemical process similar
to
photography or the clouding of a substance when exposed to light.
An electrostatic or mechanical reaction could occur when the DVD is removed
from the packaging which sets in motion a timed destruction of the data. The
effect could
be powered by a small battery or simply the energy released when the DVD is
removed
from the package.
The process of removing the DVD from the packaging or playing it in a device
could set off the timing in any other way. For example, removing the DVD from
the
packaging might break a seal exposing either the data side or the label side
of a single-
sided DVD to reactants contained within either the DVD or the packaging
materials, thus
triggering the process that renders the DVD unusable after a certain period of
time or a
certain number of uses.
The DVD player could actively read some encrypted identifying information from
the DVD and refuse to play it again. This could be implemented either by
actively
modifying the DVD or by storing this information in the player or in a
network.
The degradation can be relatively sudden (S-shaped), if possible, so that
there
would be minimal affect on the data for some initial period, and then a rapid
loss of data.
For instance, by including in the DVD a finite, controlled quantity of
antioxidant along
with a substance that reacts to oxygen, it could be possible to initially
protect the data, and
then when the anti-oxidant was used up, rapidly have the DVD degrade.
The invention can readily apply to related media such as compact discs (CDs),
Laser disks, CD-ROMs, tapes, etcetera. Applications of the invention include
storage of
limited-viewing movies, which could supplant the video rental market. Other
applications
of the invention include "trial" disks with music, software or other digital
information,
mail order catalogs for music, videos, software, data, games, etceteras hybrid
disks with
some permanent components (e.g., coming attractions), games with limited time
for
completion, etcetera.
The time during which the data would be useable could range from less than a
few
seconds to more than several weeks. The time during which the data would be
useable
could be limited to a single playing, some finite number of uses, or even a
random number
of uses.
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An extra layer on the disk is not required to achieve the desired results. In
one
embodiment, exposure to the ambient environment will damage the performance of
the
metal layer.
The term "substrate" is defined herein to be the one or more layers through
which
the laser light passes before impinging on the metal layer. The substrate can
be
polycarbonate, but other materials known to those skilled in the art may be
used.
The term lacquer is defined herein to be the layer or layers on the back of
the disk.
One or more of these layers may be composed of a material identical, or
similar, to the one
used for the substrate. The laser light is not intended to pass through the
lacquer.
Typically a one-sided disk (such as a CD or a DVD-5) will have a reflective
metal layer
between the substrate and the lacquer. In a two-sided disk (such as a DVD-10),
the
lacquer will typically include a layer binding together the two sides of the
disk.
In one embodiment, the invention includes an optical disk on which the
metallic
layer containing the data is not completely protected from the ambient
environment. For
example, a portion of the surface may deliberately not be coated by the
lacquer or
substrate. This permits the unprotected portion of the metallic layer to be
acted upon by
the ambient environment. The reflective metal may react with a component of
air. For
example, an aluminum layer may be oxidized by the oxygen in air to aluminum
oxide.
After a period of exposure to the ambient environment the quality of the
signal reflected
by the metallic layer will degrade, resulting in poor data quality or even the
inability to
read the data on the disk.
The rate of degradation can be defined by the metal. It is accelerated when
the
metal is magnesium or silver and is decelerated when the metal is aluminum. If
the metal
is in electrical contact with a second metal, the degradation is accelerated.
For example,
contacting of aluminum with silver, gold or copper accelerates the
degradation. In
general, contacting of magnesium or aluminum with a more noble metal
accelerates the
degradation of the magnesium or the aluminum layer. When two metals are used,
the rate
of degradation can be adjusted through the ratio of their exposed areas. When
the two
different metals are overlapping films, the rate of degradation is also
determined by the
overlap.
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It is not necessary that the entire surface be unprotected. For example, it is
sufficient to leave unprotected only key portions of the optical disk that
contain data
necessary to read the remainder of the disk.
It is possible to control the time required for the metallic layer of the
optical disk to
degrade by controlling the thickness, quality or composition of the substrate
or lacquer.
For example, a substrate or lacquer may be chosen such that the flux of
oxygen, nitrogen,
water or hydrogen sulfide reaching the metallic surface is a function of the
thickness of the
layer. Alternatively, the materials comprising the substrate or lacquer may be
chosen such
that layers of equal thickness have different permeabilities to oxygen, water
or hydrogen
sulfide. In such a way optical disks can be designed to fail at a desired time
after exposing
them to the destructive environment, e.g., one hour, six hours, 24 hours, 48
hours, 72
hours or one week.
Alternative Embodiment
Another composition that performs a similar function is one in which the
substrate
itself is modified over time. The modification of the substrate could cause it
to change its
optical qualities, thereby degrading the signal reaching the reader. These
optical qualities
could include its index of refraction or its transparency.
Moreover, the modification of the substrate could cause the underlying metal
layer
to change its optical properties, as described above. In this way, a time-
sensitive substrate
and/or lacquer could be combined with a reflective layer that becomes non-
reflective.
The transparency of a polymer film can be changed by the following: reaction
of
the film with water; reaction of the film with oxygen; or crystallization of
the polymer,
meaning increased alignment of polymer molecules in the film.
As an example, a substrate could be chosen that is changed by components in
air
such as oxygen or water. For example, oxygen could oxidize the substrate,
causing a
change in its transparency or its index of refraction. Alternatively, the
substrate could be
designed to absorb water in the air, causing it to swell and change its
optical properties.
Another example is that the substrate could change its permeability to oxygen
over time,
thereby permitting the oxidation of the metallic layer. In the later case, the
overall time
sensitivity of the optical media could be a function of the properties of both
the substrate
and/or lacquer and the reflective layer.
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The substrate or the metallic layer could also be made sensitive to specific
wavelengths of light. Exposure to these wavelengths would cause a change in
the optical
qualities of the layer, thereby degrading the signal reaching the reader.
Examples include
photodepolymerization of the substrate; photogeneration of acid;
photogeneration of
singlet oxygen; and unzipping of the polymers (e.g., fissure of cross linking
hydrogen
bonds). Incorporation of light-activated catalysts into the substrate or the
metallic layer
can assist in this process.
Preferably, the data quality of the disk remains high for the intended period
of use
and then decays rapidly. One method of accomplishing this is to print a layer
of metallic
silver on the back of the disk, over the lacquer. Upon exposure to air the
silver serves as a
cathode, on which 02 is reduced; aluminum serves as an anode. Corrosion is
fast only if a
short develops between the silver and the aluminum layers. The development of
the short
results from the growth of a silver dendrite through the lacquer.
To grow the dendrite through the lacquer it is desirable to use a lacquer that
has
some ionic conductivity. Typically the lacquer is a polyacrylate. If the
polyacrylate is
slightly hydrolyzed, or if it is, for example, a 2-hydroxyethylacrylate
copolymer, there will
be some ionic conductivity. Preferred are co-polymers of poly(acrylonitrile),
or of poly(4-
vinylpyridine), or of poly(1-vinylimidazole). All of these should conduct
silver, copper or
thallium ions (Ag+ Cu+ or Tl+). Thallium is less preferred due to its
toxicity.
The chemical equations are as follows:
Silver is air-oxidized:
4Ag + O z -~ Ag Z O (complexed with lacquer)
Ag 2 O + H Z O + complexant -> 2Ag+ (complexed) + 20H
Ag+ is reduced by aluminum, which is oxidized (if Ag+ is mobile in the
lacquer,
which is designed to conduct Ag+)
A13+ +30H ~ AI(OH)3 ~ AI(O)OH+H20
Ag+ +A1 ~ A13+ +3Ag°
A silver dendrite starts growing from the aluminum to the silver. When the two
layers are shorted, the "switch" between a battery's (Al) anode and (Ag)
cathode is closed.
Corrosion is rapid and catastrophic. One skilled in the art will recognize
that other similar
metals may be substituted for Al and Ag in this example.
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Given a suitable substrate, the aluminum and silver coatings could be sputter
deposited. The lacquer could be spin coated.
Another aspect of the invention is a composition comprising a degradable
optical
disk as described in this section packaged in an enclosure and atmosphere that
protects it
from the environmental stimulus that causes its failure. For example, the
optical disk
described above could be packaged in a metallized foil package containing a
gas such as
carbon dioxide, nitrogen or argon. The pressure of gases) in the package can
be sub-
atmospheric, preferably less than I torr. Inert gases such as argon are
preferred. This
would serve to protect the optical disk from oxygen, water, and/or light of
certain
wavelengths.
Another aspect of the invention is a method of manufacturing the degradable
optical disk described above. The method involves coating the substrate or
lacquer
described above onto the metallic layer so that it partially or completely
covers the disk, so
that the optical signal from the disk degrades when exposed to a preselected
environmental
stimulus.
Another aspect of the invention is a method of manufacturing the degradable
optical disk with a process that changes the optical properties of the
substrate and/or the
reflective properties of the metal layer in a way that can be partially or
fully reversed,
resulting in a fully or partially reversible loss of the ability to read the
data on the optical
disk.
Subsequently the disk can be exposed to a "reversing environment" that
partially or
fully reverses the impact of the previous step. The disk is subsequently
packaged in a
"preserving environment" (which may be identical to or different from the
reversing
environment). Opening the package results in a loss of the "preserving
environment"
and/or exposure to ambient conditions of oxygen, moisture and/or light, which
will result
in renewed degradation or loss of the ability to read data from the disk
within a certain
time period. It is preferable that this last degradation of the disk be
difficult or impractical
to reverse. For example, certain salts could be mixed with the polycarbonate
pellets used
in injection molding of the substrate. During the process of injection
molding, these salts
may interact with oxygen, carbon dioxide and/or water to form opaque compounds
that
modify the optical properties of the substrate. After the steps in the
traditional
manufacturing process, the optical disks could be chemically reduced in a
hydrogen
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atmosphere, once again rendering the polycarbonate substrate transparent to
the reading
laser. Subsequently the disks could be packaged in a hydrogen environment.
Opening the
package would result in the loss of the reducing hydrogen and exposure to
atmospheric
oxygen, moisture and carbon dioxide, rendering the polycarbonate substrate
opaque after
S a controlled time period.
Another aspect of the invention is a mechanical device which sets in motion a
timed destruction of the data when the optical disk is removed from the
packaging. In one
embodiment, removing the disk from the packaging might break a seal exposing
either the
data side or the label side of a single-sided disk to reactants contained
within either the
disk itself or the packaging materials, thus triggering the process that
renders the disk
unusable after a certain period of time or a certain number of viewings. For
example, a
reducing gas could be stored in a compartment of the package apart from the
disk. The
disk comprises a protective layer that prevents oxidation of the underlying
substrate or
metal. The package is designed such that when the package is opened for the
first time a
seal is broken and the reducing gas contacts a surface of the disk, thereby
causing the
protective layer to be destroyed. The substrate or metal layer that had been
protected from
oxidation by the protective layer would then be susceptible to oxidation by
air, as
described above.
Alternatively, a timed destruction of the data can be triggered by electric
current or
charge provided by a small battery, or simply the energy released when the
disk is
removed from the package. For example, a reversible chromophore could be used.
The
chromophore is reduced to a colorless state when the potential is applied.
When the
potential is removed, the chromophore is gradually regenerated by oxidation by
oxygen in
air. In the regenerated state the chromophore absorbs light.
Alternatively, a charge storing device such as a small battery built into the
packaging material, could provide an electric field that inhibits the reaction
that destroys
the disk's ability to read data. The process of removing the optical disk from
its packaging
would then interrupt the inhibiting field, thus triggering the process that
destroys the disk's
ability to read data. For example, the battery applies a potential to the
metal layer which
maintains the metal layer in a reduced state. When the potential is removed
the metal
layer begins to oxidize when contacted with an oxidizer such as oxygen in the
air.
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Another aspect of the invention is a method of manufacturing the degradable
optical disk and packaging it in an enclosure and/or atmosphere that protects
it from the
environmental stimulus that causes its failure. The invention further
comprises controlling
the exposure of the finished optical disk to the environmental stimulus that
causes its
failure during the manufacturing and/or the packaging operations. For example,
optical
disks manufactured today may sit unpackaged for a substantial amount of time
before
being packaged. Such a time lag may act to significantly degrade the signal
quality of the
optical disks of this invention before the disks are even packaged. Therefore,
the optical
disk should be packaged in the protective enclosure and/or atmosphere within
24 hours of
its production, preferably within 8 hours of its production, more preferably
within one
hour of its production and most preferably within 30 minutes of its
production. Stated a
different way, the optical disk should be packaged in its protective enclosure
and/or
atmosphere in a time period of less than 20% and preferably less than 10% of
its expected
degradation time.
It is also possible to manufacture and/or store the unpackaged optical disk in
an
environment that does not cause its degradation. Such an environment might be,
for
example, a nitrogen atmosphere, substantially zero air, or controlled
lighting. Such an
approach may be less desirable than promptly packaging the disk in a
protective enclosure
and/or atmosphere due to the high costs associated with these special
environments.
Another aspect of the invention is a method of use of the optical disk
described
above, comprising packaging the disk in an enclosure and/or atmosphere that
protects it
from the environmental stimulus that causes its failure, then opening the
package and
exposing it to the environmental stimulus that causes its failure.
It is desirable to have the level of degradation be minimal for some initial
period,
and then speed up resulting in a rapid degradation of the ability to read data
off the optical
disk. One method of accomplishing this is the growth of dendrites through the
lacquer, as
described above. Another means for accomplishing this is to include a finite,
controlled
quantity of antioxidant along with a substance that reacts with oxygen. The
anti-oxidant
would protect the data from oxidation reactions until such time as the anti-
oxidant was
consumed, at which time the disk would rapidly degrade. For example, an
organometallic
compound that reacts with oxygen can be packaged with the disk to protect the
disk from
oxidation while in the package. Alternatively, the organometallic compound can
be
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incorporated into the substrate, thus continuing to protect the metal layer
for a period of
time after the package has been opened.
The term coupled, as used herein, is defined as connected, although not
necessarily
directly, and not necessarily mechanically. The term substantially, as used
herein, is
defined as approximately (e.g., preferably within 10% of, more preferably
within 1% of,
most preferably within 0.1 % of).
The particular material used for the substrates can be any substantially
transparent
material. Polymeric materials are preferred, such as, for example,
polycarbonate, acrylic
(polymethylmethacralate PMMA) or polyolefine. For the manufacturing operation,
it is an
advantage to employ a polycarbonate material.
However, the particular material selected for the substrate is not essential
to the
invention, as long as it provides the described function. Normally, those who
make or use
the invention will select the best commercially available material based upon
the
economics of cost and availability, the expected application requirements of
the final
product, and the demands of the overall manufacturing process.
While not being limited to any particular performance indicator or diagnostic
identifier, preferred embodiments of the invention can be identified one at a
time by
testing for an accurate and precise time-sensitive decay of optical
properties. More
specifically, both the onset and duration of decay should be predictable. A
sudden
deterioration (brief duration of decay) is preferred, for example,
approximately one hour.
For instance, preferred embodiments of the invention can be identified one by
one by
testing for the presence of a narrow standard distribution of the time from
activating event
(e.g., exposure to air) to 50% optical deterioration (e.g., 50% loss of
transmissivity or 50%
loss of reflectivity). Many other optical (e.g., material property) tests are
possible.
Examples
Specific embodiments of the invention will now be further described by the
following, nonlimiting examples which will serve to illustrate in some detail
various
features of significance. The examples are intended merely to facilitate an
understanding
of ways in which the invention may be practiced and to further enable those of
skill in the
art to practice the invention. Accordingly, the examples should not be
construed as
limiting the scope of the invention.
Example 1
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Referring to FIGS. 1 a-1 b, edge views of an optical disk 100 with a pseudo-
transmissive read inhibitor are shown. The optical disk 100 includes a
substrate 110, a
reflective layer 120 and a lacquer layer 130. FIG. la shows the optical disk
100 in a first
state wherein the substrate 110 is substantially optically transmissive. FIG.
1 b shows the
optical disk 100 in a second state wherein the substrate is substantially
optically non-
transmissive. The transformation from the first state to the second state is
at-least-in-part a
function of time from an initializing event, in this particular example, the
opening of a
substantially gas impermeable membrane (not shown) that encloses the optical
disk 100
while it is packed, shipped and sold.
Example 2
Referring to FIGS. 2a-2b, edge views of an optical disk 200 with a pseudo-
reflective read inhibitor are shown. The optical disk 200 includes a substrate
210, a data
encoded component 220 and a lacquer layer 230. In this example, the data
encoded
component 220 is a thin film of metal. FIG. 1 a shows the optical disk 200 in
a first state
1 S wherein the data encoded component 220 is substantially optically
reflective. FIG. 1 b
shows the optical disk 200 in a second state wherein the data encoded
component 220 is
substantially optically non-reflective. As in the first example, the
transformation from the
first state to the second state is at-least-in-part a function of time from an
initializing event,
in this second example, the opening of a substantially air tight laminated
polymeric
container (not shown) that encloses the optical disk 200 while it is packed,
shipped and
sold.
Practical Applications of the Invention
A practical application of the invention that has value within the
technological arts
is time-sensitive optical media. Further, the invention is useful in
conjunction with DVD-
ROM (such as are used for the purpose of software), or in conjunction with DVD-
Audio
(such as are used for the purpose of music), or in conjunction with DVD-video
(such as
are used for the purpose of movies), or the like. There are virtually
innumerable uses for
the invention, all of which need not be detailed here.
Advantages of the Invention
An optical media with time-sensitive properties, representing an embodiment of
the invention, can be cost effective and advantageous for at least the
following reasons.
The invention allows a low cost retail product. The invention yields a product
having the
CA 02379104 2002-O1-10
WO 01/04887 PCT/US00/18944
potential of a limited content lifetime. The invention permits the avoidance
of rental
returns. The invention and minimum changes to existing manufacturing
precesses.
All the disclosed embodiments of the invention described herein can be
realized
and practiced without undue experimentation. Although the best mode of
carrying out the
invention contemplated by the inventors is disclosed above, practice of the
invention is not
limited thereto. Accordingly, it will be appreciated by those skilled in the
art that the
invention may be practiced otherwise than as specifically described herein.
For example, the individual components need not be formed in the disclosed
shapes, or assembled in the disclosed configuration, but could be provided in
virtually any
shape, and assembled in virtually any configuration. Further, the individual
components
need not be fabricated from the disclosed materials, but could be fabricated
from virtually
any suitable materials. Further, although the optical media described herein
can be a
physically separate module, it will be manifest that the optical media may be
integrated
into the apparatus with which it is associated. Furthermore, all the disclosed
elements and
features of each disclosed embodiment can be combined with, or substituted
for, the
disclosed elements and features of every other disclosed embodiment except
where such
elements or features are mutually exclusive.
It will be manifest that various additions, modifications and rearrangements
of the
features of the invention may be made without deviating from the spirit and
scope of the
underlying inventive concept. It is intended that the scope of the invention
as defined by
the appended claims and their equivalents cover all such additions,
modifications, and
rearrangements. The appended claims are not to be interpreted as including
means-plus-
function limitations, unless such a limitation is explicitly recited in a
given claim using the
phrase "means-for." Expedient embodiments of the invention are differentiated
by the
appended subclaims.
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