U.S. patent application number 11/273805 was filed with the patent office on 2006-08-31 for reactive materials for limited play optical devices and methods of making same.
This patent application is currently assigned to FlexPlay Technologies, Inc.. Invention is credited to Louis Cincotta, Edward P. Lindholm, Richard A. Minns, Larry Takiff.
Application Number | 20060194016 11/273805 |
Document ID | / |
Family ID | 32073376 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060194016 |
Kind Code |
A1 |
Lindholm; Edward P. ; et
al. |
August 31, 2006 |
Reactive materials for limited play optical devices and methods of
making same
Abstract
Methods and apparatus for making optically readable storage
media in which reading beam passes through bonding layer configured
with reactive material that transforms from optically transparent
state to optically opaque state after exposure to predefined
stimulus, thereby inhibiting access to data encoded on optically
readable storage media. The method includes steps of synthesizing
blocked dye, combining the blocked dye with carrier material,
curing the resultant combination, deblocking dye to produce a
reduced dye in the resultant bonding layer, exposing optically
readable storage media with the reactive material in its bonding
layer to predetermined stimulus. A further aspect includes
optically readable storage media wherein reading light passes
through bonding layer and data encoded information is encoded on L1
substrate. Another aspect includes processes for making optically
readable storage media with at least two mechanisms for limiting
access to encoded data of the optically readable storage media.
Inventors: |
Lindholm; Edward P.;
(Brookline, MA) ; Cincotta; Louis; (Andover,
MA) ; Takiff; Larry; (Arlington, MA) ; Minns;
Richard A.; (Arlington, MA) |
Correspondence
Address: |
MORRIS MANNING & MARTIN LLP
1600 ATLANTA FINANCIAL CENTER
3343 PEACHTREE ROAD, NE
ATLANTA
GA
30326-1044
US
|
Assignee: |
FlexPlay Technologies, Inc.
New York
NY
|
Family ID: |
32073376 |
Appl. No.: |
11/273805 |
Filed: |
November 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10651627 |
Aug 29, 2003 |
7026029 |
|
|
11273805 |
Nov 14, 2005 |
|
|
|
60415480 |
Oct 2, 2002 |
|
|
|
Current U.S.
Class: |
428/64.4 ;
G9B/7.168; G9B/7.171; G9B/7.195; G9B/7.196 |
Current CPC
Class: |
C07D 279/30 20130101;
C09B 5/60 20130101; C09B 67/009 20130101; C09B 67/0083 20130101;
C09B 69/008 20130101; G11B 7/2403 20130101; G11B 7/252 20130101;
Y10T 428/21 20150115; G11B 7/261 20130101; C09B 19/00 20130101;
C09B 67/0097 20130101; G11B 7/24038 20130101; G11B 7/2534 20130101;
G11B 7/263 20130101; C09B 5/46 20130101; G11B 7/256 20130101 |
Class at
Publication: |
428/064.4 |
International
Class: |
B32B 3/02 20060101
B32B003/02 |
Claims
1. A compound of formula I: ##STR31## wherein Y is O, S, Se,
CR.sub.17R.sub.18, NR.sub.13, wherein R.sub.13 R.sub.17, R.sub.18
is each independently selected from hydrogen, C.sub.1-C.sub.3 alkyl
and substituted aryl groups and unsubstituted aryl groups; R.sub.2,
R.sub.5, R.sub.6, and R.sub.9 each is independently selected from
hydrogen, halogen, C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6 alkoxy,
aryl, nitro, azo and fused aromatic groups; R.sub.3, R.sub.4,
R.sub.7, and R.sub.8 each is independently selected from
NR.sub.10R.sub.11, OR.sub.12, hydrogen, alkyl, aryl, azo, and fused
aromatic groups; and R.sub.10, R.sub.11, R.sub.12, R.sub.14,
R.sub.15 and R.sub.16 each is independently selected from hydrogen,
unsubstituted C.sub.1C.sub.6 alkyl, substituted C.sub.1-C.sub.6
alkyl, unsubstituted C.sub.1-C.sub.6 alkoxy, and substituted
C.sub.1-C.sub.6 alkoxy, benzyl or aryl groups.
2. The compound of claim 1, wherein Y is S.
3. The compound of claim 1, wherein R.sub.4 is selected from
NR.sub.10R.sub.11 and OR.sub.12.
4. The compound of claim 1, wherein R.sub.7 is selected from
NR.sub.10R.sub.11 and OR.sub.12.
5. The compound of claim 1, wherein Y is S; R.sub.4 and R.sub.7is
NR.sub.10R.sub.11 and R.sub.2, R.sub.3, R.sub.5, R.sub.6, R.sub.8,
and R.sub.9 each is independently selected from hydrogen, halogen,
alkyl, aryl, nitro, and fused aromatic groups.
6. The compound of claim 5, wherein R14, R15 and R16 is each
independently selected from hydrogen, unsubstituted C1-C6 alkyl,
substituted C1-C6 alkyl, unsubstituted C1-C6 alkoxy, and
substituted C1-C6 alkoxy.
7. The compound of claim 6, wherein R14, R15 and R16 is each
independently selected from methyl, ethyl, n-propyl and
isopropyl.
8. The compound of claim 7, wherein R14, R15 and R16 is
isopropyl.
9. The compound of claim 8, wherein R2, R3, R5, R6, R8, and R9 each
is hydrogen; R10 and R11 each is methyl.
10. The compound of claim 1, wherein Y is O.
11. The compound of claim 10, wherein R.sub.4 is selected from
NR.sub.10R.sub.11 and OR.sub.12.
12. The compound of claim 10, wherein R.sub.7is selected from
NR.sub.10R.sub.11 and OR.sub.12.
13. The compound of claim 10, wherein Y is O; R4 and R7 is NR10R11;
and R2, R3, R5, R6, R8, and R9 each is independently selected from
hydrogen, halogen, alkyl, aryl, nitro, and fused aromatic
groups.
14. The compound of claim 13, wherein R14, R15 and R16 is each
independently selected from hydrogen, unsubstituted C1-C6 alkyl,
substituted C1-C6 alkyl, unsubstituted C1-C6 alkoxy, and
substituted C1-C6 alkoxy.
15. The compound of claim 14, wherein R14, R15 and R16 is each
independently selected from methyl, ethyl, n-propyl and
isopropyl.
16. The compound of claim 1, wherein Y is N.
17. The compound of claim 16, wherein R.sub.4 is selected from
NR.sub.10R.sub.11 and OR.sub.12.
18. The compound of claim 16, wherein R.sub.7 is selected from
NR.sub.10R.sub.11 and OR.sub.12.
19. The compound of claim 16, wherein Y is N; R4 and R7 is NR10R11;
and R2, R3, R5, R6, R8, and R9 each is independently selected from
hydrogen, halogen, alkyl, aryl, nitro, and fused aromatic
groups.
20. An optical media comprising: a first substrate and a second
substrate, wherein at least one of said first substrate and said
second substrate has information encoding features; a bonding layer
between said first and said second substrates: wherein said bonding
layer transforms from a transparent state to an opaque state and
comprises: a carrier material, wherein said carrier material
comprises at least one of thermoplastic acrylic polymers, polyester
resins, epoxy resins, polythiolenes, ultraviolet cured organic
resins, polyurethanes, thermosettable acrylic polymers, alkyds,
vinyl resins, and combinations thereof: a reactive material,
wherein said reactive material comprises a reduced form of at least
one dye selected from azines, oxazines, thiazines, leuco-azines,
quinoneimines, indamines, indophenols, indoanilines,
anthraquinones, acridines, diarylmethane, triarylmethane and
combinations thereof; and a photostabilizing material, wherein said
photostabilizing material comprises at least one polymeric phenol
material.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 10/651,627, filed Aug. 29, 2003, which claimed
priority under 35 U.S.C. .sctn.119(e) from U.S. Provisional Patent
Application No. 60/415,480 filed Oct. 2, 2002; and which claimed
priority under 35 U.S.C. .sctn.120 from co-pending Non-Provisional
patent application Ser. No. 10/163,473 filed Jun. 5, 2002,
application Ser. No. 10/163,855 filed Jun. 5, 2002, application
Ser. No. 10/163,472 filed Jun. 5, 2002, application Ser. No.
10/163,474 filed Jun. 5, 2002, and application Ser. No. 10/163,821
filed Jun. 5, 2002, all of which claim priority to U.S. Provisional
Patent Application No. 60/295,903 filed on Jun. 5, 2001. The
disclosures of all of the above prior Patent Applications are
hereby incorporated by reference as if set forth herein in their
entirety.
FIELD OF THE INVENTION
[0002] This invention relates to optically readable data storage
media and, more particularly, to methods, compositions, and
articles of manufacture of optically readable data storage media
wherein the data is accessible for a finite period of time.
BACKGROUND OF THE INVENTION
[0003] Optical discs such as CDs and DVDs are sold and rented to
consumers. The content of the optical discs may be music, movies,
video clips, software or data. The purchase price of CDs and DVDs
can be high; this reflects the value of the information encoded on
the discs, such as movies or software, rather than the
manufacturing cost of these optical discs. Frequently, content
providers, such as movie studios or software companies, do not want
to sell at a low cost copies of their information that will have a
long lifetime in the marketplace. Consumers frequently want to
access content information only for a brief period and at a low
cost. Rentals of CDs and DVDs enable consumers to access content
information at a lower cost than if consumers had to purchase the
media, but the need to return the physical media is inconvenient.
It would be desirable to have limited play/expiring optical media
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 optical media
at low cost and with minimum changes to existing manufacturing
processes for optical discs. Finally, in order for the content
providers to be willing to provide their content through limited
play/expiring optical media, the mechanism that limits playing of
the media should not be easily defeatable, enabling access to the
content beyond the intended period of use.
[0004] Heretofore, the requirements of low cost, limited content
lifetime, avoidance of rental returns, resistance to attempts to
defeat, and minimum changes to existing manufacturing processes
referred to above have not been fully met. What is needed is a
solution that simultaneously addresses all of these requirements.
One embodiment of the present invention is directed to meeting
these requirements, among others.
[0005] Several approaches have been proposed to make a limited play
(expiring) optical disc based on a layer that changes from a
non-interfering ("transparent") state where it does not interfere
with the reliable reading of the information on the optical disc to
an interfering ("opaque") state where the layer interferes with the
reading of the data on the optical disc (e.g., see U.S. Pat. No.
5,815,484 ("Smith et al."), herein incorporated by reference in its
entirety, and U.S. Pat. No. 6,011,772 ("Rollhaus et al."), herein
incorporated by reference in its entirety. The interference may be
due to the layer becoming dark, reflective, highly birefringent,
pitting, bubbling, shattering, corroding, bending, changing
refractive properties or combinations of these, among other
possibilities.
[0006] Optical discs with such a layer changing from a transparent
to an opaque state in response to a stimulus such as exposure to
oxygen in the atmosphere, or the light of the reading laser, can be
used to manufacture limited-play optical discs (such as DVDs) that
become unusable in a predetermined way (such as within a certain
period of exposure to environmental oxygen). Such discs can find a
variety of commercial applications, such as the viewing of a video
by consumers at a moment chosen by the consumer and without the
need to return the expired optical disc.
[0007] The interfering layer that renders the disc unplayable by
inhibiting the reading of the data can be applied via a variety of
techniques to the surface of an optical disc. Such an approach,
however, has a number of disadvantages. For example, it may be
defeated by finding a way to reverse the transition of the layer to
an opaque state, such as exposing the disc to a reducing chemical
substance that reverses an oxidation reaction, or by entirely
removing the layer through chemical means (such as solvents) or
mechanical means (such as polishing or grinding). Also, adding an
additional layer can complicate manufacturing of the optical discs,
for example by requiring additional capital equipment and
additional steps in the manufacturing process, and thus can
increase the costs and/or decrease the yields for the manufacturing
of optical discs.
[0008] A protective layer engineered to resist attempts to defeat
the disc can be applied on top of the interfering layer, an
approach that has been used by at least some of the present
inventors. However, this introduces still another step in the
manufacturing process, further adding to costs and possibly further
reducing manufacturing yields. Furthermore, since the protective
layer would still be at the surface of the disc, it could still be
removed by chemical means (such as solvents) or mechanical means
(such as polishing or grinding), of could be defeated by chemical
substances that could diffuse through the protective layer and
reach the reactive layer.
[0009] As explained above, when manufacturing expiring optical
discs, it is desirable to employ a cost effective manufacturing
process and to make discs that are not easily defeatable. In
addition, it is desirable for the disc to make a rapid transition
from the playable to the expired state. Among other benefits, this
would reduce the variation of the playing period among optical
media players and drives, despite the fact that there is
substantial variability in the ability of the players and drives in
the market to play discs with a given deterioration in their
physical playability characteristics (such as the reflectivity to
the light of the reading laser).
SUMMARY OF THE INVENTION
[0010] Under a first aspect of the present invention limited play
optical devices are provided with an interstitial reactive layer
and methods of making same.
[0011] Under a second aspect of the present invention a method is
provided for authoring a master to produce a substrate of a
multi-substrate, optically-readable storage medium wherein a
topology having a plurality of pits and lands is used to create an
inverted version of the topology in which said inverted version of
the topology is used as the topology of the master.
[0012] Under a third aspect of the present invention a method is
provided for forming a multi-substrate, optically-readable storage
medium, wherein the medium has information defined as a plurality
of pits and lands on an upper substrate and said information is to
be read by light being transmitted through a lower substrate
wherein an adhesive layer bonds the upper substrate and lower
substrate together.
[0013] Under a fourth aspect of the present invention a data
storage device is provided having a first substrate halving defined
thereon a plurality of pits and lands covered by a reflective
material and a second substrate wherein a bonding layer containing
a reactive agent, which inhibits transmission of light in response
to a predetermined stimulus, resides between the first substrate
and the second substrate.
[0014] Under a fifth aspect of the present invention an adhesive is
provided for bonding a first substrate and a second substrate,
wherein said adhesive comprises a carrier material and a reactive
material that renders the data encoded substrate unreadable.
[0015] Under a sixth aspect of the present invention a mechanism is
provided that causes the data stored on an optically-readable data
storage medium to first become unreadable and second destroyed.
[0016] Under a seventh aspect of the present invention an
optically-readable data storage medium is provided having a first
substrate and a second substrate, wherein at least one of said
first substrate and said second substrate has information encoding
features, and a bonding layer between first substrate and second
substrate in which said bonding layer comprises a carrier material
and a reactive material where said reactive material changes from a
transparent state to an optically opaque state as a result of a
predefined stimulus.
[0017] Under a eighth aspect of the present invention a method
making an adhesive is provided for bonding a first substrate and a
second substrate wherein a blocked dye is combined with a carrier
material in which said blocked dye is subsequently unblocked
resulting in the reduced form of the unblocked dye.
[0018] Under another overlapping embodiment of the present
invention a class of compounds as shown below is described ##STR1##
wherein
[0019] Y is O, S, Se, CR.sub.17R.sub.18, NR.sub.13, wherein
R.sub.13, R.sub.17, R.sub.18 is each independently selected from
hydrogen, C.sub.1-C.sub.3 alkyl and substituted aryl groups and
unsubstituted aryl groups;
[0020] R.sub.2, R.sub.5, R.sub.6, and R.sub.9 each is independently
selected from hydrogen, halogen, C.sub.1-C.sub.6 alkyl,
C.sub.1-C.sub.6 alkoxy, aryl, nitro, azo and fused aromatic
groups;
[0021] R.sub.3, R.sub.4, R.sub.7, and R.sub.8 each is independently
selected from NR.sub.10, R.sub.11, OR.sub.12, hydrogen, alkyl,
aryl, azo, and fused aromatic groups; and
[0022] R.sub.10, R.sub.11, R.sub.12, R.sub.14, R.sub.15 and
R.sub.16 each is independently selected from hydrogen,
unsubstituted C.sub.1-C.sub.6 alkyl, substituted C.sub.1-C.sub.6
alkyl, unsubstituted C.sub.1-C.sub.6 alkoxy, and substituted
C.sub.1-C.sub.6 alkoxy, benzyl or aryl groups.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic cross sectional view of select stages
in the process of creating a physical stamper used in replicating
DVD-5 substrates.
[0024] FIG. 2 is a schematic cross sectional view of a single layer
DVD-5 disc.
[0025] FIG. 3 is a schematic cross sectional view illustrating the
manufacturing and reading of a standard DVD-5.
[0026] FIG. 4 is a diagram representing single sided single layer,
single sided double layer, double layer single sided, and double
layer double sided DVD constructs.
[0027] FIG. 5 is a graphic depicting the index of refraction as a
function of substrate thickness for single layer and double layer
DVDs.
[0028] FIG. 6 is a schematic illustrating the read-out
possibilities for single-layer and dual-layer DVDs.
[0029] FIG. 7 is a schematic cross sectional view illustrating a
modified DVD-5 construct with the bonding layer in the optical path
of the reading laser.
[0030] FIG. 8 is schematic cross sectional view illustrating the
manufacturing and reading of an altered DVD-5 construct with the
bonding layer in the optical path of the reading laser in which the
mother stamper was used to mold the L1 substrate.
[0031] FIG. 9 is a schematic cross sectional view illustrating the
stamper reference plane of a standard DVD-5 construct wherein the
pits and lands are molded in the L0 substrate.
[0032] FIG. 10 is a schematic cross sectional view illustrating the
stamper reference plane of a modified DVD-5 constrict wherein the
pits and lands are molded in the L1 substrate.
[0033] FIG. 11 is a graphic depicting an atomic force microscope
image of a DVD-5 father stamper.
[0034] FIG. 12 is a graphic depicting an atomic force microscope
image of a DVD-5 mother stamper.
[0035] FIG. 13 is a graphic depicting an atomic force microscope
image of the L1 layer of a modified DVD-5 that was molded from a
mother stamper.
[0036] FIG. 14 is a schematic cross sectional view illustrating the
manufacturing and reading of a modified DVD-5 in which the L1 layer
was molded from a father stamper wherein the direction of the
spiral track was reversed during mastering.
[0037] FIG. 15 is a schematic cross sectional view illustrating the
stamper reference plane of a modified DVD-5 construct wherein the
pits are above the surfaces of the lands and the lands are at the
reference plane of the L1 substrate.
[0038] FIG. 16 is a schematic cross sectional view illustrating the
stamper reference plane of a modified DVD-5 construct wherein the
pits are above the reference plane of the L1 substrate and the
lands are at the reference plane of the L1 substrate.
[0039] FIG. 17 illustrates a potential synthetic pathway for the
synthesis of triisopropylsilyloxycarbonylleucomethylene blue.
[0040] FIG. 18 illustrates the cyan reflectance density of
optically readable storage media coated with
triisopropylsilyloxycarbonylleucomethy-lene blue as a function of
time in the presence 1,4-diazabicyclo[2,2,2]octane.
[0041] FIG. 19 is a graphic depicting the spectral absorption of
methelene blue.
[0042] FIG. 20 is a schematic cross sectional view illustrating a
modified DVD-9 construct, wherein the L0 layer is partially
metallized.
[0043] FIGS. 21A and 21B are graphics depicting Koch test results
for a modified DVD-5 construct wherein the pits are molded as
depressions in the L1 substrate using a father stamper in which the
direction of the spiral track is reversed during mastering.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Certain optical discs, such as DVDs, consist of two plastic
halves ("substrates"), which are metallized and bound together with
an interstitial bonding layer. It would be desirable to use an
interstitial layer between the two substrates to interfere with the
reading laser in order to inhibit reading of the disc. This would
result in a disc that is more difficult to defeat, as the two
halves of the optical disc would protect the interfering layer.
Using an interstitial layer as the interfering layer still allows
triggering the process of disc expiration. For example,
polycarbonate, which is typically used to manufacture DVD
substrates, allows the propagation of oxygen that could reach the
interstitial reactive layer and trigger a reaction that causes the
expiration of the disc. Furthermore, it would be desirable to use
the bonding layer itself as the interfering layer, for example by
changing the chemical composition of the bonding layer through the
incorporation of a reactive substance. This could simplify the
manufacturing of limited-play optical discs because no additional
layers would be introduced, and attempting to defeat the
limited-play mechanism by removing this layer could destroy the
optical disc itself, as the bonding layer is critical to the
integrity of the optical disc. However, in certain types of optical
discs, such as a DVD-5, the bonding layer is not in the optical
path. FIG. 2 illustrates a cross sectional view of the layers
typical of a DVD-5 construct. Thus while the bonding layer could
play part in an expiration process for a DVD-5 that does not rely
on direct interference with the reading laser (e.g. by corroding
the reflective metal layer that is in contact with the bonding
layer), it would not be possible to make this type of disc expire
by transitioning the bonding layer to a state that prevents the
reading laser from reading the data on the disc. Since it is often
desirable to make the disc unplayable by means of a process that
interferes with the reading laser, it is desirable to have a disc
similar to a DVD-5 where the interstitial bonding layer is in the
optical path.
[0045] In limited use optical discs where the expiration process
relies on interference with the reading laser, the data encoding
structures (such as metallized pits on a polycarbonate substrate)
typically are preserved in an expired disc, although the reading
laser is prevented from reading the encoded information. As long as
these data structures are present, there is always the possibility
of the disc being defeated by enabling the reading laser to access
the information. It would thus be desirable to have additional
mechanisms that prevent recovery of the data, such as permanently
erasing the data by compromising the integrity of the data
structures on the optical disc.
[0046] 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.
[0047] A clear conception of the advantages and features
constituting the present 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
non-limiting, embodiments illustrated in the drawings accompanying
and forming a part of this specification. It should be noted that
the features illustrated in the drawings are not necessarily drawn
to scale.
[0048] We now describe the different aspects of the current
invention, and several corresponding embodiments and examples.
[0049] DVDs are the most common optical discs used for distribution
of movies. DVDs are made from two bonded plastic substrates,
typically referred to as L0 for the bottom substrate and L1 for the
top substrate, where "top" and "bottom" refer to a DVD in a playing
position where it is read from the bottom, as is the common
convention. These substrates are molded from materials such as
polycarbonate, acrylic, or polyolefine, which is injected in a
molten form to a mold and pressed against a stamper. The process of
creating the physical stampers used in replicating the DVD
substrates is referred to as Mastering. The following procedure is
used, which is illustrated in FIG. 1: [0050] 1. Float glass blank 5
is polished and coated with a primer 10 to enhance adhesion with
the photo resist layer 15. [0051] 2. Photo resist coating 15 is
applied, baked, and then exposed to the laser for recording. The
formatted data signal is used to modulate the cutting laser of a
laser beam recorder (LBR) machine which creates pits 20 in the
glass disc. [0052] 3. The exposed glass is then developed leaving
pits 20 and lands 25 across the surface. [0053] 4. This "Glass
Master" then has a thin (110 nm) metal layer sputter-applied to
make the surface conductive for electroplating. [0054] 5. The glass
master is then placed into an electroplating solution where nickel
is formed to the desired thickness. (Typically 0.300 mm). [0055] 6.
This "Metal Father" (or "father stamper 30") is then separated from
the glass master 35 and cleaned. At this step, the metal father 30
could be used for the molding process, but if the part gets
destroyed or damaged in replication, the entire process must be
repeated. [0056] 7. Therefore, most manufacturers will grow "Metal
Mothers" (or "mother stampers 40"), which are negatives of the
father 30. Typically, four mother stampers 40 can be grown from one
father 30 without quality degradation, and from each mother 40, up
to 8 stampers ("sons 45") can be grown. [0057] 8. Stampers get sent
to replication facilities and mothers 40 are stored for reorders or
replacement parts.
[0058] In the case of a DVD-5, which is a single layer disc
illustrated in FIG. 2, the L0 substrate 100 is covered with a thin
reflective layer 105 of aluminum by a sputtering process. This
creates a metallic coating between 60 and 100 angstroms thick (the
L0 layer). The L0 substrate 100 is then bonded 110 to a blank L1
substrate 10, as illustrated in FIG. 3. For a DVD-9, which is a
two-layer disc, the L0 layer is formed as a very thin,
semi-reflective metal layer, and is typically made of gold. A fully
reflective aluminum layer is formed on the L1 substrate (the L1
layer). The two substrates are subsequently bonded with appropriate
adhesive material, which forms a transparent bonding layer, to form
the DVD-9 disc.
[0059] As seen in the DVD family illustration in FIG. 4, a DVD disc
may contain either one or two information layers for each
substrate, resulting to different types of disc capacities, such as
DVD-5 200 (single sided, single layer, 4.7 Gbyte capacity), DVD-9
205 (single sided, dual layer, 8.5 Gbyte capacity), DVD-10 210
(double sided, single layer, 9.4 Gbyte capacity), DVD-14 (double
sided, one side single layer, one side dual layer, 13.2 Gbyte
capacity), and DVD-18 215 (double sided, dual layer, 17 Gbyte
capacity).
[0060] Standards bodies have been established that suggest,
recommend and/or dictate specifications for the various disc
formats and/or disc data capacities to insure that the different
disc formats and/or disc data capacities play and/or are read by
the various media players distributed by media player
manufacturers. Examples of standards bodies include, but not
limited to, the DVD Forum (www.dvdforum.org) and European Computer
Manufacturers Association ("ECMA")
(www.ecma-international.org).
[0061] For example, a dual layer disc such as a DVD-9 205 must
conform to the "DVD Specifications for Read-Only Disc, Part 1
Physical Specifications Version 1.0", which require the following:
[0062] 1. Total Disc thickness, including bonding layer 110,
spacer(s) and label(s), shall be 1.20 mm+0.30 mm/-0.06 nm [0063] 2.
Index of refraction (RI) of the transparent substrate shall be
1.55.+-.0.10 The index of refraction of the spacer shall be (RI of
the substrate.+-.0.10) [0064] 3. Thickness of the transparent
substrate is specified as a function of its index of refraction.
Typically with polycarbonate at RI=1.56, the thickness values for
the disc substrate would be 0.57 mm-0.63 mm (see FIGS. 5A and
5B)
[0065] The standards bodies do not directly provide a specification
for the spacer layer (bonding layer 110) thickness for DVD-5 200
and DVD-10 210 formats as long as the total disc thickness conforms
to the DVD specification and the half discs (molded substrates)
conform to RI related specifications as above.
[0066] The information in DVDs is encoded in the pits 20 and lands
25 (data areas that are not pits) that are molded into the
substrates and subsequently are metallized to form the
corresponding data layer. The pits and the lands are organized in a
spiral track, which, in the case of a DVD-5 200, is read in a
clockwise direction beginning at the inside of the disc and
proceeding towards the outside of the disc. The reference area of
the disc that is not occupied by data is used for tracking of the
reading laser. The reading laser, which has a wavelength of 630-650
nanometer in vacuum, is focused on the L0 layer 100 of a DVD-5 200
or DVD-9 205, or on the L1 layer 115 of a DVD-9 by penetrating
through the semi-reflective L0 layer 100, and it is reflected back
to a photo detector. During transitions from a pit 20 to a land 25
or vice versa, interference patterns develop, which are detected by
the photo detector and result in changes in its electrical output.
These changes in the electrical output of the photo detector allow
the player to read the information recorded on the DVD.
[0067] Dual-layer discs, such as DVD-9s 205, typically utilize one
of two methods for read-out of the disc information:
[0068] A dual-layer Parallel Track Path (PTP) disc 299 will have a
Lead-in 300 and a Lead-out 305 area on both layers, as illustrated
in FIG. 6. For each layer, the lead-in 300 area is located at the
inner radius of the disc, and lead-out 305 area is located at the
outer radius of the disc. This layout structure is comparable with
the layout of the single layer 320 disc. Reading of the data is
done, as in a DVD-5, 200 from the inner radius of the disc to the
outer radius, for both layers. With propel authoring of the content
on the disc, the PTP method can allow quick access from layer to
layer, for example in order to provide background information and
commentary in one track along with the movie in the other
track.
[0069] A dual-layer Opposite Track Path (OTP) 325 disc, also
illustrated in FIG. 6, offers the possibility of seamless
continuation of the playback from the L0 100 to the L1 115 layer.
The first information layer (L0) 100 starts with a lead-in area at
the inner radius of the disc and ends with a so-called middle area
330 at the outer radius. The second information layer starts with a
Middle Area 330 at the outer radius and ends with a lead-out 300
area at the inner radius of the disc. Reading the data 335 stored
on the disc will start at the inner radius of the first information
layer and proceed until the Middle Area 330 of this layer is
reached. Then a switch over to the Middle Area in the second
information layer is made, in order to continue reading of the data
from the outer radius up to the lead-out 305 Area in the inner
radius of the second layer (L1) 115.
[0070] Single Layer Optical Discs
[0071] One embodiment of the present invention is an optical disc
similar to a DVD-5 where, unlike a standard DVD-5, the interstitial
layer 400 typically used as the bonding layer 401 is in the optical
path 405 of the reading laser (e.g., see FIG. 7). In one embodiment
of the present invention (labeled below as "Special DVD-5 design
#1"), this disc is manufactured by inverting the reflective layer
410 of a standard DVD-5, and reading the information through the
non-information-bearing substrate 415 and the bonding layer 401. In
another embodiment of the present invention (labeled below as
"Special DVD-5 design #2"), the direction of the spiral track is
inverted during mastering, the information bearing substrate is
flipped "upside down", and the information is read through the
non-information bearing substrate 415 and the bonding layer 401. In
this type of optical disc, the bonding layer 401 is an integral
part of the optical path 405 of the reading laser. Even though the
structure of the "Special DVD-5 " disc described herein differs
from a standard DVD-5, a player would play this disc as if it were
a standard DVD-5.
[0072] This embodiment of the present invention has significant
advantages in terms of allowing the manufacturing of a low-cost
"limited-play" optical disc that is resistant to attempts to defeat
it. In particular, because it does not incorporate any additional
layers compared to a standard DVD-5, it can be manufactured on
equipment designed to manufacture DVD-5 discs with minimal changes
to that equipment. Furthermore, because the bonding layer 401 is in
the optical path, 405 modifying that layer to interfere with the
reading of data in response to a predetermined stimulus results in
a disc that is very difficult to defeat, as the interfering layer
400 is protected by the two substrates 415 and 420, respectively of
the optical disc. For example, grinding the interfering layer 400
off the disc is impractical, as it would most likely destroy the
disc. Similarly, attempting to compromise the bonding/interfering
layer in other ways is likely to destroy the structural integrity
of the optical disc.
[0073] We now describe in detail the manufacturing of three
embodiments of the current invention, which we label as "Special
DVD-5 " designs 1, 2 and 3.
Special DVD-5 Design #1
[0074] In one embodiment of the invention, the above process is
modified by using the mother stamper to replicate the L1 disc
substrate 420. FIG. 3 shows how the stamper or father is used to
mold a normal single layer DVD-5 substrate. FIG. 8 illustrates
manufacturing this embodiment of the current invention by using the
mother stamper 40 and creating a disc with the bonding layer 401 in
the optical path 405.
[0075] In a normally molded standard DVD-5 information is encoded
on the L0 100 side with "pits" 20 and "lands" 25 molded on the L0
substrate 100 and metallized with a reflective metal coating, 105
as illustrated in FIG. 2, FIG. 3 and FIG. 9. In one embodiment of
the current invention, the mother stamper 40 is used to mold the L1
side 420 as shown in FIG. 8. This side is subsequently metallized
and bonded with a blank L0 substrate, 415 leaving the bonding layer
401 in the optical path, 405 as shown in FIG. 10. Using the
specified layer thickness of 0.055 mm.+-.0.015, the thickness of
the L0 substrate 100 is targeted at 0.55 mm.about.0.57 during
molding, to yield a focal length of the disc thickness (including
the bonding layer) consistent with standard DVD specifications,
allowing the player to be in the normal focusing range for reading
at L0 layer 100. Thus the player interprets the disc as a standard
single layer DVD-5. Field experience has shown that spacer layer
thickness can be maintained at 0.045.about.0.065 mm consistently in
production. This controlled variation in production along with the
reduced thickness of the molded disc keeps the focus and optics
within the specifications set by the DVD licensing authority and
the hardware manufacturers (i.e., DVD Forum).
[0076] For the replication facility, most applications would remain
unchanged in the actual pressing and bonding portions of
production. The main areas of change would be in the LBR (laser
beam recording) and developing areas of mastering. Typically,
masters are cut with larger pit volumes to compensate for plastic
shrinkage and replication inefficiencies. The ratio of pit to land
areas on a disc is measured by a term called asymmetry. Because
asymmetry is a ratio of pit to land area, and because for each pit
area, typically defined by I3 to I14 pit, there is an equal and
opposite land area I3 to I14 land, typically it is easier for
manufacturers to target a positive asymmetry (larger pit area) to
account for loses in replication to the plastic substrate. For
example, the master may be cut with a positive 10.about.12% for
asymmetry, while the end result from molding may be 5.about.7%. The
specification for the disc substrate is:
-0.05.ltoreq.asymmetry.ltoreq.+0.15. In the case of DVD discs, a
positive asymmetry represents a larger pit volume compared with the
land area.
[0077] For this embodiment of the invention, it may be desirable to
change the asymmetry set point on the LBR to produce a higher
asymmetry value on the father stamper while subsequently increasing
the asymmetry on the mother stamper used for molding. Asymmetry can
be changed on the master by modifying the power of exposure,
focusing intensity and offset, developing time/endpoint detection,
or baseline (control of how fast the laser diode cuts the laser
exposure beam off between exposure). There are many other possible
ways to control asymmetry, but the basic process or set point
control would be the easiest to implement. This process of molding
from the mother stamper would also eliminate the need to grow
additional stampers and the subsequent yield loses attributed to
the family process.
[0078] In this embodiment of the invention, the pits 20 are molded
in the L1 layer 420 using a mother stamper, 40 and as a result the
surface of the pits 20 is elevated relative to the reference plane
450 of the L1 layer 420 as illustrated in FIG. 10. This reference
plane 450 is typically used for tracking by the disc player
(tracking area). By contrast, in a normal DVD-5 the pits 20 are
molded as cavities in the L0 substrate 100 as illustrated in FIG.
9. Using the common convention of describing a disc as if it is in
a play position where it is read from the bottom, and a convention
that we will follow hereinafter unless otherwise specified, in a
normal DVD-5 the pits 20 are lower than the reference plane 450,
while the lands 25 are at the reference plane 450 (see FIG. 9). In
the embodiment of the invention described above the blank L0
substrate 415 and the bonding layer 401 are below the L1 substrate
420 in the optical path 405 of the reading laser, and the surface
of the pits 20 in the L1 substrate 420 is below the reference plane
450 while the lands 25 are at the reference plane 450 (see FIG.
10). Note that this construction requires the pits 25 to be molded
in an unconventional way (they protrude from the reference plane
450 of the disc), which is achieved by molding the L1 substrate 420
from a mother stamper 40. FIG. 11 shows an Atomic Force Microscope
(AFM) image of a Father stamper 30 for a DVD-5, FIG. 12 shows an
AFM image of the corresponding Mother stamper 40, and FIG. 13 shows
an AFM image of the L1 layer of a Special DVD-5 Design #1, molded
from the Mother stamper 40.
[0079] This molding required for this embodiment of the invention
can present certain challenges. In a typical injection molding
process, the polymer material flows around the pits 20 on the
stamper, which are raised from the reference plane 450. This is
easier than to mold from the mother, where the polymer material
must flow into cavities that will form the pits 20 on the separated
part. As the material flows over the surface of the mother stamper
40, the molecular chains cool off through contact with the
relatively colder reference surface of the stamper. After the mold
is completely filled, then pressure must be applied to bend and
force the cooler polymer material into the pit 20 cavities.
Although this method is capable to reproduce discs within the
specifications of a standard DVD-5 configuration, the molding
process is more difficult. However, one skilled in the art can
address such challenges by adjusting the process characteristics of
the molding machine, e.g., by increasing mold surface temperature
and cycle time. Alternatively appropriate materials with higher
melt flow rate could be used, such as PMMA or high melt flow rate
polycarbonate. For example, General Electric's SPOQ research grade
polycarbonate has twice the melt flow rate of standard grade
polycarbonate.
[0080] As long as the index of refraction (RI) of the bonding
adhesive used is approximately equal to the RI of the L0 substrate
415, the thickness of the bonding layer 401 is uniform, and the
thickness of the L0 substrate 415 has been adjusted to compensate
for the presence of the bonding layer 401 in the optical path 405
of the reading layer, the player will not be able to distinguish
Special DVD-5 Design #1 from a standard DVD-5. Experience has shown
that playable discs can be manufactured even without these
adjustments, because most players will play discs that do not fully
conform to the DVD specification (e.g., DVD Forum and/or ECMA), as
long as the departure from the specification is not excessive.
EXAMPLE 1
Special DVD-5 Design #1
[0081] A father stamper 30 was mastered with slightly increased
symmetry (positive asymmetry=larger pits 20 compared to lands 25).
The asymmetry can be increased or decreased many ways. The simplest
method and the one used for this design, was to increase the
development time (endpoint detection set point) to overdevelop the
pits 20. By lengthening the development process, the pit volume
surrounding, that which was exposed, will increase in volume
causing a shift to positive asymmetry.
[0082] A mother Stamper 40 was grown from the father stamper 30 as
with a normal family process. Disc substrates were molded from the
mother stamper 40, taking advantage of the larger indentation
caused by the positive asymmetry. The larger pits 20 that resulted
from molding with the mother 40 helped to compensate for the
additional shrinkage of the pit 20, which is now an extremity to
the body of the substrate, rather than a cavity as in the standard
molding process. Typically, the molten plastic flows around the
pits 20 in a normal (father 30 or son 45) stamper like a river
flows around a hill. As the level rises, the hill or the pit 20
will be covered. As the molten plastic flows across the cooler
stamper surface, a skin layer forms right on the surface that acts
as a heat insulator. This allows for the plastic to maintain its
flow rate necessary to form the pit volume without undue stress or
cooling. In the case of Special DVD-5 design #1, the plastic has to
flow into the indentations of the mother stamper 40, rather than
around the bumps of a father/son stamper 30 and 45 respectively.
This is difficult because as the plastic flows across the surface
of the mother stamper 40, it again forms a skin layer on the
surface. Then as the mold volume increases with continued injection
and packing/holding time, the molten plastic must be forced into
the indentation. Because this skin layer is solidified typically
below the glass transitional temperature of the plastic, the
material does not free flow into the indentation. Because the
pit-forming plastic in the L1 substrate 420 of Special DVD-5 design
#1 is not in the optical path of the reading laser, the material
can be filled with greater force without the concern for
birefringence and residual stress, although there is a limit to the
pressure due to warping (tilt) caused by excessive packing pressure
on the plastic. In this example, the combination of larger
indentations in the mother stamper 40 as well as increased mold
temperatures assisted in replicating the desired pits 20.
Typically, in direct water injection systems for the mold heating
and cooling, safety interlocks of 120.degree. CC. max temperature
limit the temperature of the water. By using a 50/50 solution of
glycol and water, the temperature can be effectively run at max
temperature of 130.degree. C. This added temperature assists in
keeping the skin layer in the molten state, close to its glass
transition temperature, which facilitates the replication of L1
substrates 420 for Special DVD-5 design #1. Also, the mother
stamper 40 must be filled quickly with molten plastic in order to
prevent skinning on the surface.
[0083] L1 substrates 420 were molded as above using a mother
stamper 40. FIG. 13 shows an Atomic Force Microscope (AFM) image of
an L1 layer 420 molded from a mother stamper 40. FIGS. 11 and 12
show AFM images of the father 30 and mother 40 stampers used in the
process. For these discs to be formed, it was necessary to raise
the melt temperature from 360.degree. C. to 390.degree. C. while
maintaining a mold temperature of 121.degree. C. compared to the
standard of around 100.degree. C. The clamp force was set at
maximum of 30 tons and the filling time was decreased from 0.13 to
0.09 seconds. These parameters were adjusted until the proper pit
20 formations were achieved.
[0084] The molded L1 substrates 420 were bonded using optical grade
UV curable DVD adhesives, as used in DVD-9 production, to blank L0
substrates 415, to manufacture design #1 of the Special DVD-5. L0
substrates 415 were molded at a thickness of 0.55.about.0.57 mm
(i.e., 30.about.50 micron thinner than standard DVD halves) to
compensate for the bonding layer in the optical path, thus
preserving the same focal depth for the information-carrying layer
as in a standard DVD-5.
Special DVD-5 Design #2
[0085] The electronics of optical media drives, including DVD
players, are typically designed to read the information contained
in a layer on the disc by identifying the interference patterns
caused by transitions from a "land" 25 to a "pit" 20 in that layer.
The pits 20 are often molded with a height approximately equal to,
and typically somewhat less than, one quarter of the wavelength of:
the reading laser. For example, in DVDs the typical wavelength of
the reading laser is 635-650 nanometers (in vacuum), or 410-420 nm
in a material with RI=1.55 (which is typical of the materials used
to manufacture the DVD substrates), and thus the height of the pits
20 in a standard DVD-5 should be approximately 100-105 nanometers.
Consequently, a transition from a land 25 to a pit 20 or vice versa
corresponds to a change to the path of the reading laser of
approximately one half wavelength, or a phase change of
approximately 180 degrees. Two identical waves with a phase
difference of 180 degrees will interfere with each other and cancel
out, and the electronics of the optical drive are designed to
detect the resulting interference patterns. Using the standard
convention of the disc being read from below, in a standard DVD-5
the surface of the pits 20 is below the surface of the land 25, and
a transition from a land 25 to a pit 20 is a "down" transition,
while a transition from a pit 20 to a land 25 is an "up"
transition. If the height of the pits 20 is one quarter of the
wavelength of the reading laser then a transition from a land 25 to
a pit 20 in a standard DVD-5 is a "down" transition that
corresponds to a phase change of -180 degrees, and a transition
from a pit to a land 25 is an "up" transition that corresponds to a
phase change of -180 degrees. If all "up" and a "down" transition
differ by 360 degrees, as in the case described above, their
effects will be identical. One implication of this is that the pits
20 of a DVD-5 could be molded in the opposite direction, i.e., with
the pit surface approximately one quarter wavelength above the land
25 surface, and the electronics of the optical disc player are
unlikely to be influenced by whether a detected transition is in
the "up" or "down" direction, i.e. whether a pit 20 area is higher
or lower than the land 25 area.
[0086] In a standard DVD-5, the laser pick up will read through the
L0 substrate 100 focusing on the pits 20 aligned in a spiral track.
The rotation of the disc would be in the counterclockwise direction
(as seen from the side of the reading laser), and the spiral track
would be in the clockwise direction. Given that the pit 20
direction can be reversed without changing the electrical signal
seen by the player, in another embodiment of the current invention
the pits 20 are molded as depressions 500 into the L1 substrate
420, by employing a normal (father/son) DVD-5 stamper 30/45, as
illustrated in FIG. 14. The direction of the spiral track is
reversed during mastering, as the disc will be read from the side
of the bonding layer 401, rather than through the substrate as in a
standard DVD-5. The resulting disc has information encoded as a
DVD-5, although the pits 20 are formed in the L1 layer 420: the
surfaces of the pits 20 are above the surfaces of the lands 25, and
the lands 25 are at the reference plane of the L1 layer 420, as
illustrated in FIG. 15. The pit 20 width, length, height, and shape
give the corresponding HF signals needed to decode the data on the
DVD. The signals are encoded utilizing an eight-to-fourteen
modulation (EFM) signal. The pit 20 edges and slopes of the
sidewalls serve to distinguish the logical transition of 0's and
1's. This results in pit 20 length units measured as 3 units long
to 14 units long, which set the frequency limits of the EFM signal,
read from the disc. This measurement is commonly referred to as
3T-14T signal with T referring to a period of time. As long, as the
pits 20 are replicated in standard fashion, the player will still
be able to distinguish the pit 20 start and end position, while
reading from the reverse side, to correctly identify its data
identity. In many circumstances this will be the preferred
embodiment of the invention, as it does not require molding from
the mother stamper 40, as is the case with Special DVD-5 design #1
above.
[0087] The actual height of the pits 20 in a standard DVD-5 is
typically somewhat less than one quarter wavelength of the reading
laser. This is intended to avoid complete cancellation of the
reflected laser during a pit-to-land transition, which facilitates
the functioning of player electronics. For example, a value of
0.88*(laser wavelength)/4 is sometimes recommended, i.e.
approximately 90 nanometers for a material with RI=1.55. Thus it
may be desirable to mold the pit 20 surfaces in this embodiment of
the current invention somewhat higher than one quarter the
wavelength of the reading laser, so that the change in the path of
the reading laser during a transition from a land 25 to a pit 20 in
the special DVD-5 design #2 will be exactly one wavelength longer
than the corresponding change in a standard DVD-5. For example, if
the reading laser wavelength is 650 nanometers (i.e., 420 nm in a
polycarbonate substrate of RI=1.55), and the pits in a standard
DVD-5 are 90 nanometers, the pits 20 in this embodiment (Special
DVD-5 design #2) can be molded at 120 nanometers, i.e., one half
wavelength (210 nm) from the position of the pit 20 surface in
design #1.
EXAMPLE 2
Special DVD-5 Design #2
[0088] A special stamper for molding L1 substrates 420 for Special
DVD-5 Design #2 was produced through a modified mastering process,
where the direction of rotation of the laser beam recorder
turntable was reversed during the cutting process, resulting in a
spiral tracking path in the opposite direction from that in a
normal DVD-5. This stamper was produced by forcing the turntable to
rotate in the reverse direction from cutting a normal DVD-5, while
the content information was fed to the laser beam recorder as a
DVD-5 image. The scanning velocity that is normally preset for DVD
formats was manually set to the velocity of 3.49 m/s typical in
DVD-5 mastering. L1 substrates 420 were then molded on standard
molding machines set up for DVD-5 fabrication.
[0089] Some of the molded L1 substrates 420 were bonded using
optical grade UV curable DVD adhesives to blank L0 substrates 415,
to manufacture design #2 of the Special DVD-5. As in Example 1, the
L0 substrates 415 were molded at a thickness of 0.55.about.0.57 mm
(i.e., 30.about.50 micron thinner than standard DVD halves) to
compensate for the bonding layer 401 in the optical path, thus
preserving the same focal depth for the information-carrying layer
as in a standard DVD-5. To bond the discs, the machines were placed
into a DVD-9 production mode and the semi-reflective metallizer for
the L0 layer was taken offline. Then the cure time was adjusted to
compensate for the decrease in cure exposure needed due to the
missing semi-reflective layer. Curing was basically set for a DVD-5
disc, and the disc was flipped to cure through the L0 layer. This
function is typically reserved for DVD-9 production.
[0090] The discs were then tested with a Koch DVD testing system
and played in four different DVD players. They performed
indistinguishably from regular DVD-5 discs, as illustrated in FIGS.
21 and 22. Also, the discs played with no errors in an additional
three DVD players and two DVD-ROM drives.
[0091] Some of the molded substrates were used to manufacture discs
with a reactive bonding layer (see Example 9).
Special DVD-5 Design #3
[0092] The electronics of optical media drives, including DVD
players, can be designed to read the information contained in a
layer on the disc by identifying pits 20 and lands 25 in that layer
based on the absolute and/or relative elevation of these pits 20
and lands 25, thus distinguishing between an "up" and a "down"
transition in the information encoding layer, but without being
influenced by the elevation of the pits 20 and lands 25 relative to
the reference plane 450 of the layer. Thus in another embodiment of
the current invention, during mastering the direction of the spiral
track is reversed and also the pits 20 and lands 25 are reversed,
so that the pits 20 become lands 25 on the resulting stamper 30,
and lands 25 become pits 555. The L1 substrate 420 is then molded
by employing 550 a normal (father) stamper 30 and is bonded to a
blank L0 substrate 415. The resulting disc has information encoded
as a DVD-5, the relative elevation of pits and lands, and the "up"
and "down" transitions in the information encoding layer, are
identical to a DVD-5. Specifically, the surface of the pits is
below the surface of the lands. However, while in a standard DVD-5
the surface of the lands is at the reference plane of the L0 layer,
in this embodiment it is the surface of the lands 560
(corresponding to pits on a standard DVD-5 ) that is at the
reference plane of the L1 layer, with the pits 565 (corresponding
to lands on a regular DVD-5 ) being above this reference plane, as
illustrated in FIG. 16.
The Reactive Bonding Layer
[0093] Another embodiment of the present invention is having a
reactive material incorporated in an interstitial layer. In one
embodiment, the interstitial layer is the bonding layer of the
disc.
[0094] In one embodiment of the invention, the stimulus triggering
the reaction is exposure to atmospheric oxygen. Upon exposure to
oxygen, a reactive material, e.g., leuco methylene blue, which is
essentially colorless, is oxidized to form an opaque or semi-opaque
layer (e.g., the deep blue dye, methylene blue). Data storage media
with the opaque/semi-opaque layer can no longer be played in media
players. By adjusting the time it takes to turn opaque, this method
can be used to provide limited-play data storage media having the
desired life for the given application.
[0095] The reactive layer, which comprises both a carrier and a
reactive material, should initially have sufficient transmission to
enable data retrieval by the data storage media device, and
subsequently form a layer which inhibits data retrieval by that
device (e.g., which absorbs a sufficient amount of light i.e.,
incident and/or reflected light) at the wavelength of the laser in
the given device). Typically a layer that allows an initial percent
reflectivity from the reflective layer of about 50% or greater can
be employed, with an initial percent reflectivity of about 65% or
greater preferred, and an initial percent reflection of about 75%
or greater more preferred. Once the media has been exposed to
oxygen, e.g., air, for a desired period of time (e.g., the desired
allowable pity time of the media), the layer preferably comprises a
percent reflectivity of about 45% or less, with about 30% or less
preferred, about 20% or less more preferred, and about 15% or less
especially preferred.
[0096] Possible reactive materials include, but are not limited to,
oxygen sensitive leuco or reduced forms of phenothiazines,
phenoxazines, and phenazinies, whose members include: Methylene
Blue, Brilliant Cresyl Blue, Basic Blue 3, Methylene Green,
Taylor's Blue, Meldola's Blue, New Methylene Blue, Thionin, Nile
Blue, Celestine Blue, and Toluidine 0, as well as reaction products
and combinations comprising at least one of the foregoing material;
the structures of which are set forth below: TABLE-US-00001
##STR2## Methylene B 661 nm ##STR3## Brilliant Cresyl Blue 622 nm
##STR4## Toluidine Blue O 626 nm ##STR5## Basic Blue 3 654 nm
##STR6## Methylene Green 657, 618 nm ##STR7## Taylor's Blue 649 nm
##STR8## Janus Green B 660, 395 nm ##STR9## Meldola's Blue 570 nm
##STR10## New Methylene Blue 630, 591 nm ##STR11## Thionin 598 nm
##STR12## Nile Blue 638 nm ##STR13## Celestine Blue 642 nm
[0097] A method of synthesis of leucomethylene blue and the oxygen
dependent reoxidation to form the colored form of the methylene
blue dye is shown below: ##STR14## In addition to the above
reactive materials, numerous other dyes and light blocking
materials, can be synthesized to operate to render the data storage
media limited play. For example, some other possible reactive
materials can be found in U.S. Pat. No. 4,404,257, hereafter
incorporated by reference, and U.S. Pat. No. 5,815,484, hereafter
incorporated by reference. Additional examples include.
[0098] (a) leuco-azine dyes., such as those disclosed in U.S. Pat.
No. 4,710,570, herein incorporated by reference in its entirety
##STR15## in which:
[0099] X is O, S, NR.sub.2
[0100] Z completes a fused aromatic or hetercyclic ring system
[0101] N is 0 or 1 to allow one R.sup.1 ring substituent
[0102] Q represents CR.sub.4R.sub.5 in which at least one of
R.sub.4 and R.sub.5 is an electronegative group or R.sub.4 and
R.sub.5 may complete a ring, or
[0103] when X is S, Q may represent NR.sub.3 in which R.sub.3 is an
aromatic or heterocyclic group.
[0104] (b) quinoneimines, including indamines, indophenols, and
indoanilines, such as those disclosed in U.S. Pat. No. 5,424,475,
herein incorporated by reference in its entirety and for example,
include the following: ##STR16## where X, Y, and Z can be but are
not limited to: hydrogen, alkyl, alkoxy, aryl, substituted alkyl,
alkoxy, and aryl, OH, CN, halogens, NR.sub.6R.sub.7, SR.sub.8,
SO.sub.2R.sub.9 where R.sub.2--R.sub.9 may be hydrogen alkyl, aryl,
substituted alkyl or aryl, or may represent the atoms necessary to
complete an aromatic or acyclic ring system which may contain
heteroatoms and substitution.
[0105] (c) anthraquinones; and include, for example, ##STR17##
where R1 and R2 can be but are not limited to: hydrogen, alkyl,
alkoxy, aryl, substituted alkyl, alkoxy, and aryl, OH, CN,
halogens, NR5R6, SR7, SO2R8 where R5-R8 may be hydrogen, alkyl,
aryl, substituted alkyl or aryl, or may represent the atoms
necessary to complete an aromatic or acyclic ring system which may
contain heteroatoms and substitution.
[0106] (d) acridinies; and include, for example, ##STR18## where
R.sub.1--R.sub.4 call be but are not limited to: hydrogen, alkyl,
aryl, substituted alkyl or aryl, or may represent the atoms
necessary to complete an aromatic or acyclic ring system which may
contain heteroatoms with substitution, and R.sub.5 can be but is
not limited to: hydrogen, alkyl, aryl, substituted alkyl and aryl
groups.
[0107] (e) and di- and triarylmethane dyes, such as those disclosed
in U.S. Pat. No. 5,330,864 and herein incorporated by reference in
its entirety and include for example, ##STR19## where X and Y can
be but are not limited to: hydrogen, alkyl, alkoxy, aryl,
substituted alkyl, alkoxy, and aryl, OH, CN, halogens, NR6R7, SR8,
SO2R9 where R2-R7 may be hydrogen alkyl, aryl, substituted alkyl or
aryl, or may represent the atoms necessary to complete all aromatic
or acyclic ring system which may contain heteroatoms and
substitution. It is understood that RI can be a substituted
aryl.
[0108] Additional reactive materials include, but are not limited
to, pH indicator materials, materials that undergo
photopolymerization, materials that produce precipitates, and light
activated chemistries.
[0109] The reactive materials can further comprise a mixture
comprising at least one of any of the above mentioned reactive
materials.
[0110] In one embodiment of the present invention, the reactive
material is mixed with a carrier for deposition on and/or
impregnation into at least a portion of the surface of the
substrate. Possible carriers comprise the thermoplastic acrylic
polymers, polyester resins, epoxy resins, polythiolenes, UV curable
organic resins, polyurethanes, thermosettable acrylic polymers,
alkyds, vinyl resins and the like, as well as combinations
comprising at least one of the foregoing carriers. Polyesters
include, for example the reaction products of aliphatic
dicarboxylic acids including, e.g., fumaric or maleic acid with
glycols, such as ethyleneglycol, propyleneglycol, neopentylglycol,
and the like, as well as reaction products and mixtures comprising
at least one of the foregoing.
[0111] Some epoxy resins, which can be the used as the organic
resin, include monomeric, dimeric, oligomeric, or polymeric epoxy
material containing one or a plurality of epoxy functional groups.
For example, reaction products of his phenol-A and epichlorohydrin,
or the epichlorohydrin with phenol-formaldehyde resins, and the
like. Other organic resins can be in the form of mixtures of
polyolefin and polythiols, such as shown by Kehr et al, U.S. Pat.
No. 3,697,395 and U.S. Pat. No. 3,697,402, hereafter incorporated
by reference.
A Non-Bonding Reactive Layer
[0112] Optionally, the reactive layer can be applied to the
substrate using various coating techniques such as painting,
dipping, spraying, spin coating, screen printing, and the like. For
example, the reactive layer can be mixed with a relatively volatile
solvent, preferably an organic solvent, which is substantially
inert towards the polycarbonate, i.e., will not attack and
adversely affect the polycarbonate, but which is capable of
dissolving the carrier. Examples of some suitable organic solvents
include ethylene glycol diacetate, butoxyethanol, the lower
alkanols, and the like.
[0113] For surface coatings, the reactive layer may also optionally
contain various additives such as flatting agents, surface active
agents, thixotropic agents, and the like, and reaction products and
combinations comprising at least one of the foregoing additives.
The thickness of the reactive layer is dependent upon the
particular reactive material employed, the concentration thereof in
the reactive layer, and the desired absorption characteristics of
the layer both initially and after a desired period of time.
Development of Blocked Reactive Compounds
[0114] One embodiment of the present invention is the use of
blocked forms of the reactive compounds in the reactive layer.
These compounds will unblock within a predetermined time period
after the disc is manufactured or packaged, and typically before
the disc is used by the consumer. This is desirable when the
stimulus that triggers the reaction that causes the disc to become
unplayable (e.g., atmospheric oxygen) can trigger this reaction
during the manufacturing of the disc, and thus measures need to be
taken so that the reactive compound is not activated during the
manufacturing of the disc. For example, in the case of oxygen
triggered reactions, unless a blocked form of the reactive compound
is used, manufacturing may need to take place in an oxygen free
environment, such as a nitrogen atmosphere.
[0115] One embodiment of the present invention comprises the use of
a chemically blocked and/or modified and/or protected reactive
substance(s) for the purpose of producing optical discs that become
unplayable after being exposed to a triggering stimulus and/or
stimuli (e.g., oxygen, pH change). Specific exemplary blocked dyes
and methods of preparing dye precursors are disclosed. Leuco dye
precursors which permit the deblocking and oxidation of the leuco
dye precursors at acceptable rates and methods of applying dyes and
dye precursors to optical discs both on the surface of optical
discs and as bonding layers for optical discs are disclosed. Also
disclosed is the use of bases to increase the rate of methylene
blue generation in blocked leuco dye-containing layers in or on
optical discs, and the use of silyating agents such as
hexamethyldisilazane to stabilize the blocked leuco dye in coating
fluids.
[0116] In one embodiment of the invention, to manufacture an
optical disc that becomes unplayable after being removed from its
package (a "limited-play disc"), the disc incorporates a reactive
layer with a composition containing a leuco dye which oxidizes to a
colored dye which absorbs light at the wavelength of the reading
laser of an optical disc player, preventing enough of the reading
laser light from being reflected off the disc to render the disc
unplayable. The oxidation of: the leuco dye can be initiated by
exposure of the coating containing the dye to atmospheric oxygen,
which diffuses through the coating to oxidize the leuco dye
molecules. One problem with putting such a coating on the surface
of the disc is the possibility of the coating being removed by a
consumer to make the disc permanently playable. Another problem
with putting such a coating on the surface of an optical disc is
that this requires an additional step in the disc manufacturing
process, entailing higher cost, special tooling for production
equipment, and inevitably lower manufacturing yields. Finally, the
oxygen-sensitive fluid used to make such a coating is difficult to
handle because of its oxygen sensitivity.
[0117] In some methods of coating a leuco-dye-containing fluid on
the surface of an optical disc, some of which were described above,
the coating is solvent based and the solvent must evaporate to
yield a hard coat containing the leuco dye and any other components
required, typically bound in a polymer matrix. There are several
disadvantages to such a solvent coating. First, most of the solvent
based fluid is spun off of the disc during a spin coating
manufacturing process and is difficult or impossible to recover due
to solvent evaporation, which both wastes fluid (increasing the
cost of the process) and fouls the coating equipment. Second,
evaporation of the solvent takes time, which reduces the rate at
which such coated discs can be manufactured and thereby increases
the cost of the process. Third, the solvent vapors emitted by the
coated disc during the coating and drying process must be vented
from the manufacturing equipment, increasing the cost of the
installed equipment and presenting process and environmental
obstacles to disc replicators considering adopting this
manufacturing process.
[0118] All of the problems discussed in the previous two paragraphs
could be avoided if the leuco dye could be coated in a solventless,
light or radiation cured (hereafter called generically "UV-cured")
layer, and if this layer could be the same as the optical disc
bonding layer that is used to bond the two substrates which compose
certain types of optical disc, such as a DVD. The major obstacle to
creating such a system is that many leuco dyes, and in particular
leucomethylene blue (hereafter "LMB", which has been used by the
present inventors to render DVDs unplayable in a solvent-based,
surface coated system), inhibit both radical and cationic
polymerization reactions of the type used to cure UV-curable
monomers such as the acrylates that are commonly used as adhesives
for bonding DVD substrates. The oxidized dyes (including methylene
blue) also are inhibitors of such polymerization reactions. So
putting a leuco dye (which will inevitably contain some of the
oxidized, colored dye) in a UV-curable composition will either
prevent the UV-curing from taking place, or slow the UV-curing and
make the process much less economical by reducing the rate at which
discs can be manufactured. Moreover, the process of UV-curing can
result in some of the leuco dye becoming oxidized if any oxygen or
other oxidizing agent is present in the layer to be cured,
resulting in a product prematurely containing oxidized dye which
may interfere with the readability of the disc or change the rate
at which it becomes unreadable after exposure to oxygen.
[0119] Chemically blocked (sometimes called "protected" and/or
"modified") leuco dyes (also called "leuco dye precursors") are
known and have been used for decades in applications such as
"carbonless copy paper". In particular, blocked versions of
leucomethylene blue are known and have been used in such
applications, and one such compound at least,
benzoyl-leucomethylene blue (BLMB), is commercially available.
However, we have found that BLMB does not deblock easily enough to
yield an acceptable limited play DVD product. Other blocked
leucomethylene blue compounds share this problem, or deblock too
easily such that oxidizable leucomethylene blue is generated in the
coating fluid before it is desired.
[0120] We have found that
triisopropylsilyloxycarbonylleucomethylene blue (hereafter
"TIPSOCLMB"), whose structure and exemplary synthesis are
illustrated in FIG. 17 and described in Example 4, has the
following desirable properties for use in creating limited-play
DVDs: [0121] 1. It is readily synthesized in two steps from
commercially available starting materials. By isolating and
purifying the BOC-LMB produced in the first step as shown in FIG.
17, the TIPSOCLMB is prepared from a pure compound rather than from
the typically very impure methylene blue. [0122] 2. It can be
incorporated into an acrylate formulation described in Example 5 in
which it is stable (to conversion to oxidized methylene blue) for
at least several weeks at temperatures below 0.degree. C., allowing
coating formulations to be prepared at one facility and shipped to
another facility for DVD manufacturing if desired. [0123] 3. It can
be deblocked in a period of a week or less, presumably by a
hydrolysis reaction involving water or other nucleophiles which can
either be provided in the acrylate formulation or be absorbed from
the atmosphere in which the DVD is manufactured or in the DVD
packaging material. Nucleophiles that have shown utility for
deblocking are fluoride ion and carboxylate ion, both of which can
deblock under essentially neutral pH conditions. [0124] 4. The
deblocked LMB is stable (to oxidation to methylene blue) in the
absence of oxygen. The rate at which the deblocked LMB oxidizes in
the presence of oxygen call be controlled by regulating the
effective pH of the coating formulation. It is known in the art
that the rate of oxidation of LMB increases as the pH of its
environment increases. Thus the rate of oxidation can be increased
by the addition of basic substances that are soluble in the matrix
containing deblocked or blocked LMB and which do not react with the
matrix or substrate used. One such basic compound is DABCO
(1,4-diazabicyclo[2.2.2]octane), an amine. Other amines may be
added or substituted. Further, the addition of a strong protic acid
Such as camphorsulfonic acid decreases the rate of LMB oxidation in
a polymer film. [0125] 5. In the absence of water or other
nucleophiles, it is a stable solid which can be stored after
synthesis for at least several months, even in the presence of
oxygen. Acrylate-based coating fluids containing TIPSOCLMB can be
handled in the presence of oxygen until the deblocking reaction has
taken place, which reaction is slow enough that the handling of the
coating fluid during the DVD manufacturing process can be done in
normal (undried) air and is not difficult.
EXAMPLE 3
BocLMB Preparation
[0126] ##STR20##
[0127] t-BOC-LMB: To 3.6 L of de-ionized water in a 22 liter flask
was added 600 grams of methylene blue trihydrate which was
dissolved by stirring. Sodium dithionite (sodium hydrosulfite), 600
grams, was added to the stirred solution that was blanketed by
nitrogen. Over the course of 10 minutes was added 2.4 L of 10%
sodium hydroxide solution followed by 9.6 L of methylene chloride.
The tip speed of the blade should be 130-150 ft/mm; stirring too
rapidly affords excessive rag layer/emulsion. The solution was
stirred for 30 minutes. After stirring for 30 minutes, the layers
were allowed to separate. The leuco methylene blue/methylene
chloride layer was pressure transferred with N.sub.2 to a 4 L
separatory funnel, which was also equipped with a N.sub.2 bubbler.
The transfer was done in two portions, allowing time for the layers
to separate. The methylene chloride solution was transferred into a
nitrogen filled 12-liter flask equipped with an overhead stirrer,
as shown in the figure below. ##STR21##
[0128] When the methylene chloride solution had been completely
transferred to the flask, 30 grams of 4-dimethylaminopyridine were
added to the solution. The separatory funnel was replaced with an
addition funnel containing 770 g of di-t-butyl-dicarbonate that was
then added dropwise to the LMB methylene chloride solution, and the
solution was stirred overnight at ambient temperature. Care was
taken to blanket the leuco methylene blue solution with nitrogen
during each step of the process. About 95+% of the methylene
chloride was removed by distillation at which time.about.9 liters
of heptane were added. Distillation was continued until the
distillate temperature reached 52.degree. CC. The resultin g
blue-gray solid was filtered and washed with 3 L of heptane and
then 3 L of methanol to afford 360 g (58% yield) of t-BOC-LMB.
Methylene Blue (Tipsoc-LMB) ##STR22##
[0129] Tipsoc-LMB: In a 12-L, 3-necked, round-bottomed flask
equipped with an overhead stirrer, addition funnel, condenser, and
a nitrogen bubbler, was dissolved 360 g t-BOC-LMB in 2.5 L
methylene chloride to give a bluish solution. To this solution was
added 240 g of 2,6-lutidine, followed by dropwise addition of 430 g
of triisopropylsilyl trifluoromethanesulfonate (TipsOTf) over 1
hour. The greenish-blue reaction mixture was then stirred under
reflux 6 hours and allowed to stir at ambient temperature
overnight.
[0130] The solution was then concentrated on a rotary evaporator
under vacuum to remove most of the methylene chloride, resulting in
a dark green-blue mixture. This mixture was split in two portions
and each portion was added to 3 L of hot heptane. It is desirable
to keep water out of the heptane in this step and all subsequent
steps. Each was stirred until a deep blue residue separated from
the hot heptane solution containing Tipsoc-LMB. The hot heptane
solution was decanted from the residue and allowed to cool in a
N.sub.2 bag for 48-hour_period before filtering. The product was
filtered under a N.sub.2 blanket, it is desirable to minimize
moisture exposure, and dried in a nitrogen bag to yield 268 g of a
first crop of Tipsoc-LMB.
[0131] The Tipsoc-LMB was recrystallized by dissolving the 268
grams of Tipsoc-LMB in 2.5 liters of boiling heptane containing 14
grams of decolorizing carbon, Pac 200 from Norit Americas zinc. In
small scale recrystallizations, Calgon AQ-30 granulated carbon has
also been effective. The hot heptane solution, which should be
essentially colorless, was filtered through a pad of dry Celite and
cooled to afford 200 grams of 99.75% pure Tipsoc-LMB, m.p.
118-119.
[0132] Examples 5 and 6 illustrate how TIPSOCLMB can be
incorporated in a coating fluid that can be UV-cured to create a
reactive layer containing TIPSOCLMB. Example 7 illustrates how the
above technique can produce an interstitial reactive layer, which
allows the Special DVD-5 designs 1, 2 and 3 to be used to
manufacture expiring optical discs. Example 8 illustrates how
TIPSOCLMB deblocks and becomes oxygen sensitive LMB in either a
surface or an interstitial layer. When exposed to oxygen, the LMB
oxidizes into methylene blue, as illustrated by the increasing cyan
density in FIG. 18; methylene blue strongly absorbs light in the
650 nm wavelength, as illustrated in FIG. 19.
EXAMPLE 5
Formulation of Coating Fluid Containing TIPSOCLMB
[0133] 80 mg TIPSOCLMB
[0134] 80 mg Irgacure 819 (Ciba Geigy; sensitizer)
[0135] 4.0 ml CD-501 acrylate (Sartomer;
propoxylated[6]trimethylolpropanetriacrylate)
[0136] 18.5 mg 1,4-diazabicycle[2.2.2]octane ("Dabco"; Aldrich;
base)
[0137] 155 .mu.l 1,1,1,3,3,3-hexamethyldisilazane (""HMDZ";
Aldrich"; stabilizer)
[0138] The TIPSOCLMB, Irgacure 819, and Dabco are weighed into a
brown glass bottle, a stir bar is added, the CD-501 is poured in to
the proper weight, and the HMDZ is added by syringe. Dry nitrogen
is blown into the bottle for a few minutes and the bottle is capped
and the cap covered by parafilm. The contents are stirred at room
temperature for at least two hours to dissolve the solids. If not
all of the material is used, blow the bottle with nitrogen, cap and
seal with parafilm, and store in a freezer; warm the bottle before
opening to prevent water from condensing in the bottle.
EXAMPLE 6
Preparation of Disk Surface-Coated with TIPSOCLMB/Acrylate
Formulation
[0139] A DVD clear half disk (an unmetalized 0.6 mm thick and 120
mm diameter polycarbonate disc) or a full DVD (two layers bonded
together, back to back with a adhesive) is centered on a laboratory
spin coating turntable rotating at roughly 60 rpm's. A 4 ml
solution from example #5 is then applied uniformly in a circular
ring by a syringe at about a 34 to 40 mm diameter from the center
of the disc. The spin speed is then rapidly increased to about 200
rpm for about 15 seconds, resulting in a coating of
acrylate/TIPSOCLMB fluid about five .mu.m thick. The spinning is
slowed; excess fluid wiped off of the edge of the disk with a
tissue and base solvent, if available, and then removed to a lab
bench. At this point, the disc is subjected to about five flashes
from a Norlite 400 xenon flash lamp at its max setting. The time
between flashes is dictated by the charging of the flash lamp, but
should be sufficient as to not induce added stress from heat
generated in the cure (typically about 5 seconds). This process
will yield a clear, uncolored, fully cured acrylate film. Other
disks are also prepared with similar acrylate formulations that
contain either no Dabco or 10.times. the amount of Dabco described
in Example 5.
EXAMPLE 7
Preparation of Disk Sandwich-Coated with TIPSOCLMB/Acrylate
Formulation
[0140] A DVD hall disk is centered data side up on the turntable as
stated above. The turntable is held stationary while the fluid is
dispensed on the data side in a manner creating drops with a
syringe roughly 3.about.5 mm round. These are evenly spaced about 3
mm apart on a diameter of 30.about.40 mm. The disc to be bonded is
then placed data side facing the solution and slightly bowed away
from the bottom disc by the edges. The disc will be lowered at
angle until the first contact point between a fluid drop and top
disc occurs. We do not want to place the top disc immediately on
the bottom because of entrapped air and subsequent bubbles.
Therefore, to get a more uniform capillary flow, we can rotate the
disc in a clockwise rotation while keeping it slightly bent under
light pressure until each of the fluid drops begins to form a
capillary bridge ring. Once the capillary ring is completed, the
top disc can be released and the capillary action will continue. We
can wait for the capillary flow to cover the surface, or we can
spin the disc at 100 rpm's until the material at least reaches the
maximum OD diameter. At this point the turntable can be turned on
and rotated at about 500 rpm's for 5 seconds. This will level the
spacer layer (adhesive layer) and remove excess material from the
OD. The disc edge can then be wiped and the disc will then be UV
cured. It is important that prior to curing, the disc halves be
aligned as close as possible to avoid center hole misalignment an
subsequent play back problems. At this point, the disc is subjected
to about 20.about.30 flashes from a Norlite 400 xenon flash lamp at
its max setting. The time between flashes is dictated by the
charging of the flash lamp, but should be sufficient as to not
induce added stress from heat generated in the cure (Typically 5
seconds). This process will yield a clear, uncolored, fully cured
acrylate film. Other disks are prepared with similar acrylate
formulations that contain either no Dabco or 10.times. the amount
of Dabco described in Example 5.
EXAMPLE 8
Deblocking and Oxidation of TIPSOCLMB in Surface and
Sandwich-Coated Disks, and the Effect of a Base Included in the
Coating Formulation
[0141] Disks prepared as described in Examples 6 and 7 were cut
into six `chips` each and the chips were stored in either dry
nitrogen, dry air, or room air (average RH about 30%) and their
cyan reflectance densities were recorded periodically with an
X-Rite 504 densitometer (the samples stored in nitrogen were only
tested at the start and end of the experiment as they were visibly
unchanged and it was desired to minimize their exposure to oxygen).
In all cases the samples stored in nitrogen showed no methylene
blue (MB) generation, as expected. Incorporating
1,4-diazabicyclo[2.2.2]octane (Dabco) into an acrylate formulation
at 1.0 equivalent with respect to the TIPSOCLMB gave very
significant acceleration of the deblocking/oxidation rate compared
to a control (FIG. 18), while a higher concentration of this
compound was actually less effective. In general the open samples
(those with the TIPSOCLMB layer coated on top of a DVD half without
any cover) generated MB only slightly faster than the sandwich
structures, indicating that deblocking and oxidation of the LMB is
not significantly limited by the transfer of either water or oxygen
through an unmetallized 0.6 mm polycarbonate layer. Rather, the
deblocking of the TIPSOCLMB is likely to be rate-limiting in these
systems. The control samples without any added base shows
noticeably faster MB generation in room air than in dry air,
suggesting that moisture in the air speeds deblocking in this
sample.
[0142] Example 9 illustrates how a reactive bonding layer was
incorporated into Special DVD-5 Design #2, thus manufacturing a
disc that was normally playable like a DVD-5 and subsequently
became unplayable.
EXAMPLE 9
Incorporating TIPSOCLMB into a Special DVD-5 Design #2 Bonding
Layer
[0143] A set of experiments was performed to test whether a
formulation containing TIPSOCLMB, Irgacure-819, Dabco,
1,1,1,3,3,3-hexamethyldisila-zane (as a fluid stabilizer), and
Sartomer CD-501 acrylate monomer could be used as a DVD adhesive to
produce playable DVDs. Using the formulation described in Example
5, filtered through a 1.0 .mu.m glass syringe filter, the fluid was
syringed onto either clear or metallized Special DVD-5 Design #2
halves manufactured as in Example 2. A DVD half disk is centered
data side up on the turntable as stated above. The turntable is
held stationary while the fluid is dispensed on the data side in a
manner by creating drops with a syringe roughly 3.about.5 mm round.
These are evenly spaced circularly about a diameter of 30.about.40
mm. The disc to be bonded is then placed data side facing the
solution and slightly bowed away from the bottom disc by the edges.
The disc will be lowered at an angle until the first contact point
between the fluid and top disc occurs. We do not want to place the
top disc immediately on the bottom because of entrapped air and
subsequent bubbles. Therefore, to get a more uniform capillary
flow, we can rotate the disc in a clockwise rotation while keeping
it slightly bent under light pressure until each of the fluid drops
begins to form a capillary bridge ring. Once the capillary ring is
completed, the top disc can be released and the capillary action
will continue. We can wait for the capillary flow to cover the
surface, or we can spin the disc at 100 rpm until the material
reaches the maximum OD diameter. At this point the turntable can be
turned up and rotated at about 500 rpm's for 5 seconds to thin out
the adhesive and achieve a resulting 50 .mu.m adhesive films
(determined by profilometry). This will level the spacer layer
(adhesive layer) and remove excess material from the OD. The disc
edge can then be wiped and then the disc UV cured. It is important
that prior to curing, the disc halves be aligned as close as
possible to avoid center hole misalignment an subsequent play back
problems. At this point, the disc is subjected to about 20.about.30
flashes from a Norlite 400 xenon flash lamp at its max setting. The
time between flashes is dictated by the charging of the flash lamp,
but should be sufficient as to not induce added stress from heat
generated in the cure (Typically 5 seconds). This process will
yield a clear, uncolored, fully cured acrylate film that plays on
the DVD test player.
[0144] The discs were manufactured under normal ambient conditions,
and were subsequently put in a nitrogen box for 3-4 days, to remove
the oxygen dissolved in the substrates (which in this example took
all estimated 12-20 hours), and to allow TIPSOCLMB to unblock into
LMB (which in this example took 2-3 days).
[0145] The Special DVD-5 design #2 discs were subsequently removed
from the nitrogen box and were measured for reflectivity at the 650
nm wavelength as a function of time. The discs were clear and
playable for 12-16 hours after which time they turned dark blue
within 24 hours and became unplayable with reflectivities under 2%
at 650 nm.
Multiple-Layer Optical Discs
[0146] As seen in the DVD family illustration in FIG. 4, in a dual
layer optical disc designed to read multiple layers from one side,
the spacer (bonding) layer is in the optical path. In the case of
Dual Layer DVDs, the given specification for this spacer layer
thickness is 0.055.+-.0.015 mm. The thickness of the substrate for
a dual layer DVD with optical path bonding is typically
0.550.about.0.641 mm.
[0147] Incorporating a reactive compound inhibiting the reading,
laser in the bonding layer 800 of either type of dual-layer disc
would only inhibit the player from reading the L1 layer 805, as the
bonding layer 800 is not in the optical path for reading the L0
layer 810. Furthermore, the metal 815 in the L0 layer 810 might act
as a barrier preventing a predetermined stimulus such as moisture
or oxygen to permeate to the reactive compound in the bonding layer
800 in a controllable manner.
[0148] One method around this potential problem would be as
follows. Typically, when a player or a drive begins reading a disc,
it looks for the table of contents or information area in the
lead-in area for the L0 layer 810 (see FIG. 6). When authoring the
disc, it is possible to have the L0 lead-in 820 area contain
commands to directly access the L1 layer 805. In order to be able
to read the L0 layer 810 to direct the play sequence to the L1 805,
we would have to metallize the L0 side 810. This would then
possibly interfere with the reactive adhesive material 800 causing
unstable or uncontrolled kinetics of reaction that would be
dependent on the permeability of the metal layer. One approach
around this would be to change the metallizer masking for the L0
semi-reflective layer 800, which is typically run out to 58 mm to
59 mm radius on the disc, to something closer to the lead-in or
information data area on the L0.
[0149] To facilitate activation of the reactive material 800, e.g.,
when the activating stimulus is oxygen or moisture that might be
prevented from reaching the reactive bonding layer 800 because of
the L0 metal layer 820, part of the L0 layer 810 can be masked
during metallization, so that pelt of the reactive layer will be
easier to expose to the stimulus and thus the corresponding part of
the L0 layer will be disabled. These discs would have a partially
metallized L0 layer 810, as illustrated in FIG. 20. For example, if
only the lead-in area or program start portion of the L0 layer 810
is metallized, the player is able to read the lead-in data, and is
able to access the information stored on L1 layer 805. As only a
small area on the L0 layer 810 would be metallized, a substantial
part of the reactive bonding layer would be in direct contact with
the L0 substrate 810, which is typically permeable by stimuli such
as oxygen or moisture. When the reactive bonding layer responds to
the appropriate stimuli and starts interfering with the reading
laser, the player is no longer able to access the corresponding
part of the L1 layer 805.
[0150] Another embodiment of the present invention is utilizing
authoring techniques, such as sequencing and branching commands to
be executed by the optical media player, to ensure that making a
certain part of a disc unplayable will interfere with playing other
parts of the disc, or the entire disc. The part of the disc made
unplayable for this purpose may be in the single layer of a
one-layer disc, or in any of the layers of a multi-layer disc. For
example, one embodiment of this invention consists of a DVD-9
authored so that making a certain part of the L1 layer unplayable
would interfere with playing other parts of the disc, or the
entirety of the disc. For example, reading the L0 layer lead-in
area would direct the player to access a part of the L1 layer that
would become unreadable when the reactive layer starts interfering
with the reading laser, which would cause the disc to be
inoperable. A DVD-9 disc can be authored so that all or part of the
L1 layer is essential in order to play any information on L0 and/or
L1. For example each chapter on the disc can be authored so that it
requires reading certain information on L1 before proceeding.
[0151] In another embodiment of this invention, activation of the
reactive material is facilitated by controlling the deposition of
the L0 layer. For example, fast deposition of a gold or silver or
silicon L0 layer though sputtering is known to result in grainy
dendritic formations that are easier to penetrate by oxygen and
moisture. Also, a thinner L0 layer can be deposited, which is
easier to penetrate by oxygen and moisture. While depositing grainy
or thin L0 layers may be unacceptable for a permanent, archival
quality disc, it is often adequate for a limited use, expiring
disc.
EXAMPLE 10
DVD-9 Discs with TIPSOCLMB Incorporated in a Reactive Bonding
Layer
[0152] A DVD-9 with parallel track path encoding can have two
distinctly different layers for play back. In the encoding or data
mastering process, the Lead-in area normally found on the L0 disc,
can have information telling the reading players to read from
either or both layers on the disc. Therefore, for this example
using a reactive bonding material, the reactive layer could prevent
play back from the L1 layer while not affecting the L0. For this
example corresponding L0 and L1 masters were manufactured, and L0
and L1 substrates were normally molded and metallized.
[0153] The DVD halves were bonded as in example 9 above using an
adhesive containing the formulation TIPSOCLMB, Irgacure-819, Dabco,
1,1,1,3,3,3-hexamethyldisilazane (as a fluid stabilizer), and
Sartomer CD-501 acrylate monomer described in Example 5. The
solution was filtered through a 1.0-.mu.m glass syringe filter. A
DVD half disk is centered data side up on the turntable as stated
above. The turntable is held stationary while the fluid is
dispensed on the data side in a manner by creating drops with a
syringe roughly 3.about.5 mm round. These are evenly spaced
circularly about a diameter of 30.about.40 mm. The disc to be
bonded is then placed data side facing the solution and slightly
bowed away from the bottom disc by the edges. The disc will be
lowered at an angle until the first contact point between the fluid
and top disc occurs. We do not want to place the top disc
immediately on the bottom because of entrapped air and subsequent
bubbles. Therefore, to get a more uniform capillary flow, we can
rotate the disc in a clockwise rotation while keeping it slightly
bent under light pressure until each of the fluid drops begins to
form a capillary bridge ring. Once the capillary ring is completed,
the top disc can be released and the capillary action will
continue. We can wait for the capillary flow to cover the surface,
or we can spin the disc at 100 rpm until the material reaches the
maximum OD diameter. At this point the turntable can be turned up
and rotated at about 500 rpm's for 5 seconds to thin out the
adhesive and achieve a resulting 50 .mu.m adhesive films
(determined by profilometry). This will level the spacer layer
(adhesive layer) and remove excess material from the OD. The disc
edge can then be wiped and then the disc UV cured. It is important
that prior to curing, the disc halves be aligned as close as
possible to avoid center hole misalignment an subsequent play back
problems. At this point, the disc is subjected to about 20-30
flashes from a Norlite 400 xenon flash lamp at its max setting. The
time between flashes is dictated by the charging of the flash lamp,
but should be sufficient as to not induce added stress from heat
generated in the cure (Typically 5 seconds). This process will
yield a clear, uncolored, fully cured acrylate film that plays on
the DVD test player.
[0154] The discs were manufactured under normal ambient conditions,
and were subsequently put in a nitrogen box for 7 days, to remove
the oxygen dissolved in the substrates (which would take an
estimated 12-20 hours), and to allow TIPSOCLMB to unblock into LMB
(which was estimated to take up to 5-6 days). The discs were
subsequently removed from the nitrogen box and were normally
playable on both the L0 and L1 layer for 2-3 (lays on a Pioneer
player. After 7 days of exposure to ambient oxygen, the discs
became unplayable on the L1 layer, although they would play
normally on the L0 layer.
EXAMPLE 11
DVD-9 Discs with Partially Metallized L0 Layer
[0155] As in example 10 above, DVD-9 master tapes were generated
with the data area being identified on layer L1 and the L0 layer
serving only to provide the lead-in and subsequent table of
contents relating to the disc type and information. During play
back, the L0 lead-in would instruct the disc to read from the L1
data side. In this case, we would not have to metalize the entire
surface of the L0 layer because there is no information to be read
outside of the lead-in area. Therefore. DVD-9 master tapes were
produced with lead-in and command information on L0 and data area
on L1. Typically, the metalizer masking covers areas from 25 mm
through 118 mm diameters on both layers. Being as the lead-in area
data covers the diameters of 25.2 mm to a maximum of 48 mm, and the
subsequent information area starts at no less than 48 mm diameter,
the metalizer masking can be reduced to cover the lead-in only.
This would allow a reflective signal to read the lead-ill on the L0
layer and then switch to the L1 layer for data playback without
having to read through additional semi-reflective metal.
[0156] In this example, we manufactured donut-masking plates that
dropped into the metalizer OD mask assembly. By registering the
masking from the OD, we are able to reduce the metalized diameter
to an area allowing lead-in playback. We extended the mask just
outside of the lead-in 48 mill diameter in order to compensate for
eccentricity tolerance with the masking position. Additionally, in
order to prevent a reflective spike from the transition of clear
disc area to metalized disc area when reading the L1 layer, the
edge of the masking was slightly raised above the disc to cause a
shadowing or tapered layer uniformity. This would cause a gradual
focusing compensation rather than a large "speed bump" effect
causing its radial noise and focusing error to fall out of
specification and perhaps jump track.
[0157] The resulting DVD-9 halves were bonded as in Example 10. The
DVD-9s constructed were tested for playability in a Pioneer DVD
player and in a DVD-ROM drive, and were subsequently put in a
nitrogen box for 7 days, so that the TIPSOCLMB would unblock into
LMB. The discs were subsequently removed from the nitrogen box and
were clear and playable for 12-16 hours, and turned dark blue
within 24 hours after that, becoming unplayable. The discs were
effectively prevented from having information read from either L0
or L1.
Controlling the Timing of the Reaction
[0158] Preferably, the data quality of the disc should remain high
for the intended period of use and then decay rapidly resulting in
a rapid degradation of the ability to read data off the optical
disc. One benefit of this embodiment of the present invention is
that for a broad class of stimuli, such as those requiring
diffusion of a substance through a barrier layer, incorporating the
reactive material in all interstitial layer results in substantial
advantages regarding the timing characteristics of the
reaction.
[0159] One method of achieving the above mentioned desirable timing
characteristics is to use a reactive interstitial material between
the disc substrates, as described earlier, which reacts with a
substance that needs to diffuse through the substrates of the disc.
For example, if the reactive material is sensitive to oxygen, there
will be an extended period in which there will be no reaction while
the oxygen diffuses through the disc substrates. Once oxygen
reaches the reactive layer, the resulting reaction can be fast,
resulting in rapid expiration of the disc.
[0160] When oxygen is used as the diffusing substance, it may be
necessary to remove oxygen that dissolves in the disc during the
different stages of its manufacture. This can be done, for example,
by storing the discs in a vacuum or in an oxygen free environment
for an appropriate period of time. It has been established
theoretically and experimentally that 24 hours is an adequate
period to extricate oxygen dissolved in a 0.6 mm thick
polycarbonate disc substrate. Alternatively, if a blocked reactive
material is used as described earlier-, all oxygen scavenging
material, such as iron or an organometallic compound, can be used
to extricate oxygen from the optical disc before the blocked
reactive material unblocks. This method has several manufacturing
advantages; for example, it can avoid oxygen extrication during
manufacturing of the disc by including the oxygen scavenging
material in the packaging of the disc, which allows the extrication
of the oxygen to take place after the disc is manufactured and
packaged.
[0161] Another means for controlling the timing of the expiration
of the disc is to include in or adjacent to the reactive layer a
finite, controlled quantity of an appropriate protective substance,
such as all antioxidant in the case that the reactive layer reacts
with oxygen. The protective substance would prevent the reactions
that cause the disc to expire until such time as the anti-oxidant
was consumed, at which time the disc would rapidly degrade and
become unplayable. For example, an organometallic compound that
reacts with oxygen can be packaged with the disc to protect the
disc from oxidation while in the package. Alternatively, the
organometallic compound can be incorporated into the substrate,
thus continuing to protect the metal layer for a period of time
alter the package has been opened.
[0162] Depletion of a protective substance could be combined with
diffusion of the triggering substance through the substrate of the
disc, to result in longer delays before the disc expires, or to
enable finer control of the characteristics of the expiration
process, such as the steepness of reflectivity degradation.
Example of Antioxidant in Reactive Layer
[0163] Alternatively, the protective substance may be a reducing
agent which may be incorporated into the reactive bonding layer
itself. In an experiment in which the concentration of TLMB was
also varied and shown to have an effect, the play time was shown to
be more greatly affected by varying the amount of stannous
ethylhexanoate reducing agent (see Table I). TABLE-US-00002 TABLE I
Concentration Play Time (hrs) Formulation # TLMB Sn(II) EtHexanoate
short long A 1% 2% 14 22 B 1% 4% 38 55 C 0.5% 2% 18 26 D 0.5% 4% 46
58
[0164] DVD-5 discs were made using a TIPSOCLMB-containing adhesive
formulation, and deblocked in an oxygen-free atmosphere for 48
hours at 60.degree. C. At that time the discs were exposed to
ambient room air and the rate of methylene blue color development
was quantified with an X-Rite reflection densitometer. The short
Play Time was chosen to be the time at which the cyan density
increased by 0.35, which roughly corresponds to a playability
cutoff at 45% reflectance as typified by a low quality DVD player.
The long Play Time was chosen to be the time at which the cyan
density increased by 0.85, which roughly corresponds to a
playability cutoff at 10% reflectance as typified by a high quality
DVD player.
[0165] The most likely mechanism for this extended play is
reduction of the initially formed methylene blue dye back to the
leuco form until most of the reducing agent is consumed. Alternate
mechanisms. Such as the stannous compound acting as a primary
oxygen scavenger to consume oxygen before the leuco dye is
affected, are also possible.
[0166] The mobility within the cured matrix is expected to have a
significant effect upon the reduction rate; indeed, the calculated
glass transition temperature (Tg of the monomers used in this
example is -34.degree. C. In such a soft matrix, adequate molecular
mobility should exist to allow molecular contact of reducing agent
and dye molecules.
[0167] Alternate reducing agents might include other Sn(II)
compounds which would be soluble in the UV cure formulation, such
as acetylacetonate chelates, fatty alpha-aminoacid chelates and
salts; soluble iron(II) compounds, such as fatty carboxylates and
chelates such as acetylacetonates: ascorbic acid and its
derivatives such as ascorbyl palmitate; hydroquinones, such as
2,5-di-tert-amylhydroquinone; alkylhydroxylamines; hydrazines;
dithionates with a solubilizing counterion; reducing saccharides
such as glucose; alpha-hydroxyketones, such as acetol;
appropriately substituted boron and silicon hydrides. Although many
of these materials are difficultly soluble in current active
adhesive formulations, a more expeditious choice of monomers and
oligimers might allow the use of one of these alternate reducing
agents while still providing good adhesive and dye stabilization
properties.
Preventing Photobleaching of Expired Discs
[0168] Polyhydroxystyrenes (for example, PHS-XE-01, available from
ChemFirst Electronic Materials L. P, 14785 Preston Road, Suite 480,
Dallas, Tex. 75254-912), hive been found to be effective
photostabilizers for azine dyes in UV cured adhesives. Enhanced
photostabilization of azine dyes occurs in formulations in which
the selected monomer mixture has a more hydrophobic character. The
hydrophobic character may be characterized in this system by
alcohol group content; low levels of alcohol groups result in a
more hydrophobic matrix compared to higher levels of alcohol. In
one experiment, the ratio of monomers (Sartomer SR395, isodecyl
acrylate; Sartomer SR495, caprolactone acrylate; and Sartomer
SR349, ethoxylated bisphenol A diacrylate) was varied such that the
weight % of SR495 (hydroxy containing monomer) ranged from 39% to
62%. Improved photostability of the methylene blue (produced via
in-situ deblocking and oxidation of TIPSOC-LMB) in the respective
cured bonding adhesives was found in the formulation with the lower
alcohol content.
EXAMPLE A
[0169] A series of Part A mixtures was formulated by dissolving
polyhydroxystyrene (PHS) into a liquid mixture of varying ratios of
two Sartomer monomers, SR495 and SR349 at 60.degree. C. The basic
deblocking catalyst, Tinuvin 292, and photoinitiator were added
sequentially after all of the PHS had dissolved. The resulting
mixtures were stirred until clear mixtures were obtained. The Part
B solution was made by dissolving TIPSOC-LMB powder in Sartomer
SR395 with slight warming. TABLE-US-00003 Part A Stock Solutions
(grams) Component I II III SR495 30.0 40.0 50.0 SR349 30.0 20.0
10.0 PHS 9.78 9.78 9.78 T292 0.232 0.232 0.232 IC819 1.60 1.60 1.60
Component Part B Stock Solution (grams) SR395 12.0 TIPSOC-LMB
0.960
[0170] The complete active adhesive mixtures were made by adding
0.27 grams of Part B with vigorous shaking to 3.58 grams of each of
the three Part A formulations described above. The resulting
component ratios of the three formulations is shown in the
following chart. TABLE-US-00004 % (wt/wt) Component I II III SR495
39.00 51.94 64.93 SR349 39.00 25.97 12.98 PHS 12.70 12.7 12.7 T292
0.30 0.3 0.3 IC819 2.08 2.08 2.08 SR395 6.49 6.49 6.49 TIPSOC-LMB
0.52 0.52 0.52
[0171] Discs were assembled by spreading 0.6 grams of the full
adhesive between two clear LO polycarbonate half discs, and curing
the adhesive with a 2 second exposure of a Xenon Corporation DVD
xenon flashlamp. The colorless discs were deblocked and oxidized to
methylene blue for 24 hours in a 60.degree. C. oven for 24 hours.
The relative rate of deblocking was estimated from the cyan optical
density that was quantified with an X-Rite reflection densitometer
against a white background; a higher density of methylene blue
indicates a higher deblocking conversion. After the deblocking
period, the colorized discs were placed 2'' from a bank of 40 W
cool white fluorescent bulbs for 9 days, after which the cyan
optical density was recorded; a higher density indicates higher
retained methylene blue dye after the light exposure period, and
thus better photostability. The following table shows that the
deblocking rate is increased with higher levels of the alcohol
containing monomer, SR495, and that photostability (resistance to
light fading), is best with lower levels of SR495. TABLE-US-00005
Cyan Density (X-Rite) Formulation % SR495 24 hrs 60.degree. C. 9
days Lights I 39 2.02 2.43 II 52 2.35 1.36 III 65 2.78 1.05
[0172] Bonding agents prepared with alkoxylated monomers have shown
similar effects: increasing levels of Sartomer monomers SR502
(ethoxylated-9 trimethylol triacrylate) and CD501 (propoxylated-6
trimethylol triacrylate) result in increasingly poor photostability
of TIPSOC-LMB derived methylene blue even in the presense of
polyhydroxystyrenes.
[0173] An additional benefit of a polymeric light stabilizer is
that a higher concentration of photostabilizer may be incorporated
into the adhesive mixture with the upper limit to be found only as
a result of high viscosity. Usable adhesives with concentrations of
PHS as high as 25% by wt have been formulated; conventional
monomeric phenolic organic compounds tend to form crystals which
have been found to limit their solubility and thus their utility in
active adhesive formulations.
[0174] A polymeric phenol made by the acid catalyzed addition of
hydroxyphenyl carbinol, known as PHS-B available from ChemFirst
Electronic Materials L.P, has also been found to be very effective
as a photostabilizer in these systems. Copolymers of
4-hydroxystyrene such as with styrene and butyl acrylate also show
photostabilization effects in bonding resins; many copolymers would
be expected to be effective here.
[0175] The photostability of azine dyes other than methylene blue
is also improved with the addition of polyhydroxystyrene
polymers.
EXAMPLE B
[0176] This example incorporates the use of a photostabilizer
(polyhydroxystyrene) to prevent photobleaching of the oxidized
disc. Excessive photobleaching of the methylene blue chromophore
would lead to defeat of the limited play mechanism and result in a
playable disc after exposure to a strong light source.
[0177] This example also incorporates the use of a reducing agent
which results in an increase in the play time. The 4% level of
stannous ethylhexanoate in this formulation provides a disc with
play time of about 24 hours, whereas discs made using this
formulation without added reducing agent provide a play time of
about 8 hours. TABLE-US-00006 Component: Wt. grams Final Wt % Part
A: Sartomer SR440 32.50 10.08% Sartomer SR238 65.00 20.16% Sartomer
SR495 97.50 30.24% PHS8EO1 39.00 12.09% Tinuvin 292 0.75 0.23%
Irgacure 819 5.20 1.61% Part B: Sartomer SR339 65.00 20.16%
TIPSOC-LMB 4.50 1.40% Stannous 2-Ethylhexanoate 13.00 4.03%
[0178] Part A was prepared by first combining the Sartomer monomers
SR440, SR495 and SR231 (Sartomer Company, 502 Thomas Jones Way,
Exton, Pa. 19341), followed by the dissolution of the
polyhydroxystyrene (PHS-8EO1; Triquest, LP. 14785 Preston Road,
Dallas, Tex. 75254-9123) with stilling and slight warming to
60.degree. C. With continued stirring, the Tinuvin 292 (Ciba
Specialty Chemcals, 540 White Plains Road, Tarrytown, N.Y.
10591-9005) was then added, followed by the Irgacure 819 (Ciba
Specialty Chemcals, 540 White Plains Road, Tarrytown, N.Y.
10591-9005). The mixture was stirred in the dark until homogeneous.
Part A is very stable and may be stored in the dark at about room
temperature for several months before use.
[0179] Part B was prepared by dissolving TIPSOC-LMB in Sartomer
SR339 under a nitrogen atmosphere with slight warming to 50.degree.
CC. After cooling, the stannous ethylhexanoate (Sigma-Aldrich) was
added and the solution was briefly stirred until homogeneous. Part
B has limited stability and should be used within 8 hours.
[0180] The full active adhesive was then prepared by the addition
of Part B to Part A followed by vigorous mixing at room temperature
in the dark. The adhesive was used within four hours of mixing.
[0181] Additionally, photostability can be improved by adding
resorcinol derivatives such as 4-hexylresorcinol or
4-cholorresorcinol Photostability may be further improved by
increasing the TIPSOC concentration applied to the disc.
Monomer Selection
[0182] The monomers in the above examples were selected for their
contribution to the following properties:
Solvency
[0183] The monomers of the present invention provide good ability
to keep all the components in solution and free from particulate
matter both during storage and during mixing of Parts A and B.
Viscosity
[0184] Because the polymeric nature of the preferred
photostabilizer (PHS) tends to result in high mixture viscosities
of the uncured resins, most monomers were selected for their low
viscosity attributes in each functional group. Low viscosity of the
uncured resin helps provide good flow characteristics during the
spreading and spinning of the bonding agent between the two halves
of the DVD during assembly.
Surface Tension
[0185] Spreading of the uncured bonding agent between the disc
halves during manufacture is also facilitated in bonding agents
that have lower surface tension.
Deblocking Rate
[0186] TIPSOC groups are deblocked with materials that are common
to hydrolysis reactions; that is, water and alcohols with catalysis
by bases and acids. The goal of the deblocking rate is to form
sufficient LMB within one week at room temperature in the cured
packaged disc.
Extended Playtime Resulting from Added Reducing Agents
[0187] Cured bonding agents that rely on stannous 2-ethylhexanoate
to extend the useful playtime have been found to exhibit longer
playtimes when higher levels of hydrophilic monomers are used. In
some disc systems, this varies from 10 hours in cured discs without
SR495 up to 24 hours in discs with 40% SR495.
Bond Strength
[0188] Multifunctional acrylates are used to provide crosslink
density which contribute to the firmness and strength of the cured
bonding resin. This, along with adhesion, helps maintain the
alignment and physical dimensions of the DVD disc.
Photostability
[0189] Photostabilization of azine dyes occurs in part when the
highly polar ionic azine dyes are formed in mediums of decreasing
polarity with increasing levels of PHS.
[0190] The monomers from the above examples include:
SR495:
[0191] The polarity of the monomer blend contributes to the
photostabilization by PHS of the resultant azine dyes. In the above
examples, low levels of SR495, the alcohol containing caprolactone
acrylate, result in better photostability of the expired disc, but
those low levels of hydroxyl groups have an adverse effect on the
deblocking rate of TIPSOC-LMB in the intially formed disc. Thus,
the optimum level of the alcohol containing moiety is determined by
the balance of these two effects, photostability and deblocking
rate, and for the above examples is about 30% caprolactone
acrylate.
[0192] Alternate high polarity monomers that increase deblocking
rates have a similar adverse effect upon photostability; these
include ethylene and propylene oxide derivatives and other monomers
that contain polyether moieties. Similar effects were also seen
with N-vinylpyrrolidone. These, and other hydrophilic acrylates may
have advantage in other azine dye containing bonding agents
assuming a proper balancing of properties.
[0193] Alternate hydroxyl containing monomers also include, but are
not limited to hydroxyethyl acrylate, hydroxypropyl acrylate,
hydroxybutyl acrylate, diethylene glycol monoacrylate and
methacrylates as may be appropriate according to availability,
toxicity and handling.
SR238, Hexanediol Diacrylate
[0194] This multiftmctional acrylate contributes to crosslink
density, which contributes to the strength of the cured adhesive.
SR238 also contributes strongly to low viscosity of the uncured
mixture and to the hydrophobic character of the cured resin. Other
multifunctional acrylates that would also be expected to provide
good results, assuming rebalancing of properties as described
above, include trimethylolpropane triacrylate (SR35 1), and 1,3-
and 1,4-butanediol diacrylates (SR212 and SR213), pentaerythritol
triacrylate (SR444) pentaerythritol tetraacrylate (SR295),
dipentaerythritol tetracrylate (SR355) and dipentaerythritol
pentaacrylate (SR399). Alkoxylated multifuntional monomers may also
be used with the appropriate balancing of properties. Oligimeric
monomers such as epoxy and urethane acrylates, which typically are
higher in viscosity than the materials described in this
disclosure, may have advantage in some systems.
SR440, Isooctyl Acrylate
[0195] The incorporation of isooctyl acrylate (SR440) and also
isodecyl acrylate (SR395), which are low surface tension materials
(28 and 28.6 dynes/cm, respectively), has been observed to reduce
the amount of incorporated air bubbles during manufacture and thus
provides a higher disc yield. SR440 was found to be preferred over
SR395 because of its greater range of solvency for PHS in
combination with the other monomers. These monomers also contribute
to low viscosity, low Tg, and low polarity. Many other alkyl
acrylates would be expected to have a similar effect.
SR339, Phenoxyethyl Acrylate
[0196] This aromatic monomer is used as the main Part B monomer as
it provides good solvency for both TIPSOC-LMB and the inadvertently
formed methylene blue. It has been found that small amounts of
TIPSOC-LMB deblocking do not effect the functioning of the
resultant discs. Less polar monomers force the methylene blue to
separate as crystals which require filtration to prevent disc
defects. Another benefit of SR339 is that it provides a solution
polarity that easily mixes with the PHS containing Part A without
causing precipitation or other adverse mixing phenomena. One
adverse effect of SR339 is a lowering of photostability, but the
system may be rebalanced with a higher PHS level or a lower SR495
level.
Additional Deblocking Mechanisms
[0197] Carbamates can be used as protective groups for amines.
Carbamates can be removed (de-blocked) by a variety of methods.
These methods include, for example, acid and base hydrolysis,
hydrogenolysis, .beta.-eliminations with base, chemical reductions,
electrolysis, thermolysis and photolysis. (See T. W. Greene and P.
G. M. Wuts, Protective Groups in Organic Synthesis, 3.sup.rd
Edition, John Wiley & Sons, pp 503-550, 1999 and references
therein.)
[0198] Moreover, de-blocking mechanisms may also release various
reagents which are useful for or aid in the generation of the
colorless leuco-dye or the oxidized colored dye. For example,
Patent #JP2000343837A, herein incorporated by reference in its
entirety, uses thermal release of an acid to catalyze the
de-blocking of t-BOC-LMB. Photoacid generators can also be used in
a similar manner. The photorelease of radicals can be used to
oxidize leuco-dyes(see for example U.S. Pat. No. 3,445,234 herein
incorporated by reference in its entirety). Also, the thermal
release of amines via hydrolysis of carbamates are also known, and
include, for example, U.S. Pat. No. 6,015,771, hydrolysis
incorporated by reference in its entirety.
A. Thermolysis
[0199] U.S. Pat. No. 4,602,263 and U.S. Pat. No. 4,826,976, both
herein incorporated by reference in their entirety, teach the use
of the thermally unstable carbamate moiety to protect dyes.
B. Photolysis
[0200] Photochemically labile protective groups are known. See, for
example, V. N. R. Pillai, Synthesis, 1 (1980); Leuco methylene blue
color formers with UV light including t-BOC (J Photopolymer Science
and Technology, 14, 245-250 (2001); and Japanese Patent No.
JP06032940, herein incorporated by reference, which uses
leuco-methylene blue carbamates for measuring the quantity of UV
radiation.
[0201] Additional photolabile protecting groups include, for
example, those described in the following references and the
references incorporated therein. Tetrahedron Letters, No. 12, pp
1029-1030, 1979; Proc. Natl. Acad. Sci. USA, Vol 96, pp 1193-1200,
February 1999; Tetrahedron Letters, 40, pp 1441-1444, 1999; and
Synthesis, pp 1-26, January 1980. The following carbamates can be
cleaved by photolysis: m-Nitrophenyl carbamate, 3,5-Dimethoxybenzyl
carbamate, o-nitrophenyl carbamate, 2-(2-nitrophenyl)ethyl
carbamate, 4-methoxyphenacyl catbamate, and
3,4-dimethoxy-6-nitrobenzyl carbamate. C. Electrolysis
##STR23##
[0202] Examples include those materials described in the following
references and the references listed therein:
[0203] 1. L. Van Hijfte and R. D. Little, J. Org. Chem., 50, 3940
(1985)
[0204] 2. M. F. Semmelhack and G. E. Heinsohn, J. Am. Chem. Soc.,
94, 5139 (1972)
[0205] 3. V. G. Mairianovsky, Angew. Chem. Int. Ed. Engl., 15, 281
(1976)
D. .beta.-Eliminations/Assisted .beta.-Eliminations
[0206] One aspect of the present invention provides compounds of
Formula (I): ##STR24##
[0207] Q is ally group capable of undergoing acid or base
hydrolysis. Q can be removed under the appropriate conditions,
which then causes the decarboxylation of the free carbamate group.
Q can also be a group which ring closes on the carbonyl to
eliminate the blocking group to furnish the leuco dye. The leuco
dye is thereby unblocked, which if formed in the presence of
oxygen, undergoes oxidation to the colored form of the dye.
Representative groups for Q can be, but are not limited to
C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6 alkoxy,
--CH.sub.2-CH.sub.2X, aryl, substituted aryl, benzyl, substituted
benzyl, and SiR.sub.14R.sub.15R.sub.16, wherein X is either a
leaving group capable of undergoing an E1 or E2 elimination
reaction (.beta.-elimination) or a moiety which can act as a
nucleophile capable of ring closing;
[0208] R.sub.14, R.sub.15 and R.sub.16 each is independently
selected from hydrogen, unsubstituted C.sub.1-C.sub.6 alkyl,
substituted C.sub.1-C.sub.6 alkyl, unsubstituted C--C.sub.6 alkoxy,
substituted C.sub.1-C.sub.6 alkoxy, benzyl and aryl groups. See,
for example, T. W. Greene and P. G. M. Wuts, Protective Groups in
Organic Synthesis, 3.sup.rd Edition, John Wiley & Sons, pp
540-2, 1999 and references therein.
[0209] Accordingly, a second aspect of the present invention
provides compounds of Formula (II): ##STR25##
[0210] Z is ally group capable of undergoing a .beta.-elimination
reaction. It has been disclosed that, in general, nitrogens
protected by carbamoyl moieties that have attached to the
corresponding carbamoyl oxygen a group capable of undergoing a
.beta.-elimination reaction will be deblocked under mildly basic
conditions. This structure may be represented by Formula (III):
##STR26##
[0211] Where Z is a substituent (carbanion-stabilizing group)
capable of activating an adjacent moiety, L (Z itself call
represent a protected group that must first be activated in order
to assist in the .beta.-elimination. See, for example, T. W. Greene
and P. G. M. Wuts, Protective Groups in Organic Synthesis, 3.sup.rd
Edition, John Wiley & Sons, pp 540-545, 1999 and references
therein, that is capable of undergoing a .beta.-elimination
reaction. Where "dye" when taken with a carbamoyl moiety is a
colorless precursor of the dye ("dye-precursor-"), said Z-L-being
substituted on the dye precursor such that the precursor is
maintained in its colorless form, at least until the
.beta.-elimination reaction is initiated.
[0212] beta.-elimination reactions are well known in the art and
represent base promoted 1, 2-elimination reactions. The release of
a leaving group in this reaction (-Carbamoyl-Dye in formula (III)
above) can be greatly accelerated when a carbanion-stabilizing
group Z, is placed .beta. to the leaving group. The choice of
stabilizing group Z determines the rate at which the leaving group,
Carbamoyl-Dye, is released. Any moiety that undergoes
.beta.-elimination may be employed as Z-L in formula (XI) above,
provided that the elimination rate for the moiety provides the dye
at a useful rate in a given color generating system. The rate
constants for various leaving groups in elimination reactions of
.beta.-substituted sulphones, .beta.-substituted phenyl ketones and
.beta.-substituted esters have been reported by Charles J. M.
Stirling, et al, J. Chem. Soc. (B), 672-684 (1970); Charles J. M.
Stirling et al, J. Chem. Soc. Chem. Commun., 941 (1975); and
Charles J. M. Stirling, Acc. Chem. Res. 12, 198-203 (1979).
Examples of some leaving groups from a carbon system include --SMe;
--SPh; --SePh; --OPh; --OMe; --P(O)(OEt).sub.2; --NHTs;
--C(Me).sub.2NO.sub.2; --N(Me)Ts; --N(Me)Ac; --N(Ph)Ac; --N(Ph)Ts;
--N(Ph)CO.sub.2CH.sub.2Ph and --N(Me)CO.sub.2Ph wherein Me, Et, Ph.
Ac and Ts represent methyl, ethyl, phenyl, acetyl and tosyl,
respectively. In particular, the carbamoyloxy leaving group in
conjunction with sulfones has been reported by Kader, A. T. and
Stirling, C. J. M., J. Chem. Soc. Chem. Commun., 363, (1962).
[0213] A variety of amides are used in the art to protect amine
functional groups (Greene pp. 550-564). Simple aides are generally
very stable to acid or basic hydrolysis. However, the lability of
the haloacetyl derivatives to mild acid hydrolysis makes the use of
this moiety more practical for our application. In particular, the
trifluoroacetyl group may be particularly advantagous (R. S. Goody
and R. T. Walker, Tetrahedron Lett., 289 (1967) as well as
substituents that contain a neighboring hydroxyl group that can
participate in an intramolecular hydrolysis (E. R. Kiroft, P.
Dorff, and R. Kullinig, J. Org. Chem., 54, 2936 (1989). Another
useful approach makes use of amides that are cleaved by
intramolecular cyclization after activation (by reduction,
photolysis, hydrolysis, silyl group cleavage). The concept of
assisted cleavage is generalized below (see, for example, T. W.
Greene et al. p. 561). As an example, one might have an alcohol
group that is protected in the form of an ester which following
hydrolysis induces deprotection by intramolecular addition to the
amide carbonyl. ##STR27##
[0214] In this Scheme R.sub.2NH would represent a leuco dye
available for dye formation.
II. Novel Generation of Dyes
[0215] The interfering layer of the present invention that renders
the disc unplayable by inhibiting the reading of the data does not
need to be derived directly from blocked precursors of oxygen
sensitive leuco dyes such as those disclosed above. [0216] 1. One
embodiment could use blocked/protected intermediates that when
activated (by any of the methods described above) would result in
the formation of the leuco-dye "in-situ" in a stepwise manner. The
colorless leuco-dye would then be oxidized in the presence of
oxygen to the highly colored dye. The following scheme resulting in
the blue dye, indigo, is illustrative of the embodiment. ##STR28##
[0217] 2. Oxidative coupling of one or more primary intermediates
with one another or with one or more secondary intermediates can
lead to highly colored compounds. These coloring systems are
familiar to those in the photographic/imaging industries. The
coupling of a color developer with a dye forming coupler moiety
substituted at the coupling carbon with a thermally, photolytically
or hydrolytically removable leaving group is known in dye
chemistry. These intermediates may be protected or blocked using
methods known in the art and activated to deblocked by any of the
methods discussed above. The de-blocked intermediates are then free
to interact in a color forming reaction. E. Combinations of
De-Blocking Method
[0218] Combinations of de-blocking can be applied either to an
individual leuco-dye (see assisted .beta.-eliminations), to
mixtures of leuco-dyes where each incorporates a different
de-blocking method, or to a mixture of a single leuco-dye that is
protected with a variety of de-blocking groups (see, for example,
Krieg-Kowald, US Patent Application Publication US Published
Utility Patent Application No. 2002/0102499A1, Aug. 1, 2002 and
herein incorporated by reference in its entirety).
[0219] It should be understood that combinations of any of the
disclosed de-blocking mechanisms can be used to gain better control
of the de-blocking kinetics, increase stability of the interfering
layer towards bleaching or to satisfy other stability requirements
related to the blocked dye (or leuco dye). For example, a
combination of a basic hydrolysis and photolytic de-blocking can be
used to give added protection against attempts to photobleach the
oxidized dye (methylene blue) which is generated via the base
assisted de-blocking reaction.
Preventing Expired Discs from Playing in Future Generation
Players.
[0220] Future generations of optical discs and players are
typically developed to offer increased performance for consumers
and other users of the technology. For example, DVDs offer
increased storage capacity compared to CDs, and the next generation
of "blue laser" DVDs will offer improved capacity compared to
today's DVDs. Subsequent generations of optical storage media, such
as the "DVR" format currently under development, will have even
greater capacity and performance.
[0221] Optical media players are typically engineered with the
ability to play previous generations of discs. For example, while
CD players employ a laser with a wavelength of 780 nanometers to
read CDs, DVD players typically employ their reading laser with a
wavelength of 650 nanometers to read CD discs. The next generation
DVDs ("blue laser DVDs") is designed to be read with a laser with a
wavelength of 450-460 nanometers; the "DVR" format will use lasers
emitting around 405 nm. Future generation players are likely to be
able to read current DVDs with their 450-460 nanometer or 405
nanometer lasers.
[0222] Dyes used to inhibit the reading laser in current optical
disc players are typically designed to interfere with the reading
laser employed by these players; such dyes, however, may not
interfere with the reading laser future players, which is likely to
have a shorter wavelength. The implication is that expired discs,
even though they may not play in the current generation of players,
they may become playable when future generation players become
available. Dyes used to inhibit the reading laser in current DVD
players are typically designed to interfere with a 650 nanometer
reading laser; such dyes, however, may not interfere with a reading
laser in the 450-460 nanometer rage. For example, methylene blue,
which is one of the read inhibit dyes proposed in Smith et al.
while strongly absorbent in the 650 nanometer wavelength, it is
essentially transparent in the 450-460 nanometer range (see FIG.
19). The implication is that expired DVDs may play in blue laser
DVD players.
[0223] Another embodiment of the present invention is an optical
disc that will not play in future generation players, thus
preventing an expired disc from becoming playable when future
generation players (blue laser DVD players) become available. This
can be accomplished by incorporating in the optical path of the
disc a selectively interfering layer that will interfere with the
reading laser of future generation players, and thus will inhibit
reading of the disc in such players. Such a layer can be designed
by incorporating a dye or pigment that does not interfere with the
reading laser in a certain type of players, but does interfere with
the reading laser in other types of players (or will change to
become interfering in response to a predetermined stimulus). For
example, Acridine Yellow [135-49-9], is essentially transparent at
the 635-650 nanometer wavelength but strongly absorbs at the
450-460 and 405 nanometer wavelengths (absorption max in ethanol at
462 nm, molar absorptivity=37,000 M.sup.-1cm.sup.-1). Alternatively
9,10-bis(phenylethynyl)anthracene [10075-85-1] also does not absorb
at all in the 635-650 nanometer range, but is strongly absorbent in
the 450-460 and 405 nanometer range (absorbance max 455 nm in
cyclohexane, molar absorptivity 33,000 M.sup.-1cm.sup.-1). Other
classes of dyes and pigments that can be used for blocking blue
laser light (at either 450-460 or 405 nm) include aromatic
hydrocarbons, azo dyes, cyanines, polymethines, carotinoids,
hemicyanines, styryls, quinaldines, coumarins, di- and
triarylmethines, anthraquinones, nitro and nitrosos. As mentioned
above, methylene blue is essentially transparent at the 450-460
nanometer wavelengths, but strongly absorbs at the 635-650
nanometer range.
[0224] In one embodiment of the current invention, the selectively
interfering layer is a dedicated layer in the optical path of the
reading laser. In another embodiment, which is likely to be the
preferred embodiment because it does not introduce an additional
design element for the optical disc, the selectively interfering
layer is combined with another element of the disc, such as the
substrate or the reactive layer. For example, this could be
accomplished by mixing an appropriate dye or pigment, such as
Acidine Yellow [135-49-9] or 9,10-bis(phenylethynyl)anth-racene
[10075-85-1], with the polycarbonate or other polymer used to mold
the substrate of the disc, or with the reactive layer in an
expiring disc, such as the bonding layer in the special DVD-5
designs described earlier.
[0225] Optionally, the reactive material belongs to the class of
dyes known as Fluoran dyes. A Fluoran dye can be blocked and/or
protected and/or modified with a chemical moiety. Once unblocked
the Fluoran dye, in response to a triggering stimulus and/or
stimuli, would transition from a colorless form to black. Such a
system would not require an additional dye or pigment to insure
that the disc, once expired, does not play in media players of
different wavelengths.
Use of Additional Mechanisms to Prevent Recovery of Data
[0226] Another embodiment of the present invention is combining the
mechanism(s) that prevent reading of the optical disc by inhibiting
the reading laser with additional mechanism(s) for preventing
recovery of the information encoded in the data structures on the
disc. These additional mechanism(s) can be designed with less
accurate control of the timing of their activation than the
mechanism(s) that work by inhibiting the reading laser. Thus it may
be desirable to combine the mechanism that controls expiration of
the optical disc by interfering with the residing laser with
additional mechanism(s) that permanently prevent the recovery of
the data on the optical disc. For example, a disc may become
unplayable by transitioning a layer in the optical path from
transparent to opaque in a controlled time period, for example
approximately 24 hours after a predetermined stimulus, such as
removing the disc from its packaging. In addition, a secondary
mechanism could corrode the metal layer on the disc, such mechanism
acting over a longer period of time, such as 1-2 weeks, and being
triggered by the same or a different stimulus. Additional
mechanisms may also be employed, such as an additive that degrades
the polycarbonate material from which the disc is composed, which
process can be triggered by the same stimulus (such as exposure to
ambient air), or a different stimulus (such as the centrifugal
forces generated when a disc is played in a CD or DVD player).
Other triggering stimuli for these backup mechanisms can include
various constituents of air, light, physical motion, and time from
manufacturing or packaging. Many other mechanisms are possible.
[0227] One method of accomplishing this is to deposit a layer of
metallic silver separated from the information bearing aluminum
layer by a material incorporated for this purpose, or by an
existing material, such as the bonding layer or one of the
substrates of the optical disc. This silver layer can be above or
below the aluminum layer, and if it is below (and thus in the
optical path of the reading laser) it needs to be sufficiently
transparent initially so that the reading laser can read the
information on the aluminum layer.
[0228] In one embodiment of the invention, a DVD-9 disc is
manufactured with a reactive bonding layer consisting of a material
with appropriate dielectric properties, and with appropriate
selection of metals for L0 and L1. For example, L0 can be made of
silver and L1 can be made of aluminum.
[0229] When a silver layer and an aluminum layer are separated by
an appropriate dielectric material, then upon exposure to oxygen
the silver serves as a cathodes on which O.sub.2 is reduced, and
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 separating material. To grow the dendrite
through the separating material it is desirable to use a material
that has some ionic conductivity. Several likely separating
materials consist of or contain 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.sup.+Cu.sup.+ or Tl.sup.+). Thallium is less preferred due to
its toxicity.
[0230] The chemical equations are as follows:
[0231]
[0232] Silver is air-oxidized: 4Ag+O.sub.2.fwdarw.Ag.sub.2O
(complexed with lacquer)
Ag.sub.2O+H.sub.2O+complexant.fwdarw.2Ag.sup.+
(complexed)+20H.sup.-
[0233] Ag.sup.+ is reduced by aluminum, which is oxidized (if
Ag.sup.+ is mobile in the lacquer, which is designed to conduct
Ag.sup.+) Ag.sup.++Al.fwdarw.Al.sup.3+++3Ag.sup.0
Al.sup.3+++3OH.sup.-.fwdarw.Al(OH).sub.3.fwdarw.Al(O)OH+H.sub.2O
[0234] 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.
[0235] Alternatively, one embodiment of the present invention takes
advantage of technology employed in the photographic industry. This
technology is used to remove the silver image following the
development of the dye images in color photography. This is
accomplished through a technique called "bleaching" where the
silver image is oxidized to silver ion and then removed with a
silver solvent (fixing). The list of possible oxidants is large and
include, for example, the mechanism depicted below: ##STR29##
[0236] The ferrous ion is air oxidized to the ferric ion, which is
capable of oxidizing the silver forming ferrous ion which in turn
can then complete the cycle again. The silver ion is capable of
migration, thereby compromising the integrity of the information.
The redox reaction becomes more thermodynamically favorable
depending on the chelator (counter ion) used to solublize the iron
(EDTA, 8-hydroxquinoline, phenanthroline, acetoacetonate,
ferrocene, etc.).
[0237] Additionally, there are a variety of compounds known in the
photographic field that act as accelerators of the bleaching
reaction. These include, for example, but not by way of limitation:
polyoxyethylene polymers containing side chains with thioether
groups, mercaptotriazoles, mercaptothiadiazoles,
mercaptoimidazoles, mercaptotetiazoles, imidazoles,
monothioglycerol, cystine, cysteine, cystamine, thiourea
derivatives, thioamide compounds, aminoalkylene thiols, etc.
Compounds known as anti-foggants have also been shown to act as
bleach accelerators.
[0238] According to another overlapping embodiment of the present
invention Fe.sup.+2 is solubilized with a low potential chelator
that is displaced after packaging with a high potential chelator
following a de-blocking mechanism.
[0239] Optionally, hydroquinone-quinone redox chemistry can be used
to accomplish the same thing as the ferrous salts. A blocked
hydroquinone is de-blocked in the package and air oxidized to the
quinone on exposure to air which in turn oxidizes the silver. This
approach can also take advantage of bleaching accelerators.
##STR30##
[0240] Alternatively, other ways of permanently corroding data
layers via the reactive layer can be employed. For example, certain
embodiments of this invention may have a bonding layer that
promotes the corrosion of the reflective metal layer or may involve
the diffusion of some substance from the bonding layer to the
reflective layer(s). For example, the presence of halide ions has
been observed to corrode thin silver layers and prevent reading of
the DVD. Mechanisms could be envisioned to release or activate
halide ions and thus inhibit reading of the data. In other
embodiments, the additional mechanisms will not be part of the
bonding material. For example, a precursor of a corrosive substance
may be deposited adjacent to the metal layer. When oxygen or some
other appropriate substance diffuses through the substrate and
reaches the corrosive precursor, a reaction could be initiated that
results in producing a corrosive substance that over a period of
time permanently destroys the data structures on the disc.
Alternatively, the material in the Substrate of the disc, such as
polycarbonate, could be engineered so that it degrades over a
period of time, thus making the disc unusable. Such substances and
reactions are known to the skilled in the art.
[0241] 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.
[0242] 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.
[0243] The transparency of a polymer film can be changed by any of
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.
[0244] 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.
[0245] 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 or base; 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.
[0246] The following paragraph should be eliminated. You
misinterpreted my use of the indigo dyes. I had two possible uses
of indigo dyes. 1) they were an example of the possible generation
of leuco-dyes in-situ meaning the leuco form of the dye is actually
synthesized (through a deblocking mechanism) in the disk in an
unprotected form 2) since they ale highly insoluble when formed,
they could also be used as an example of the generation of a
precipitate to block the reading laser.
[0247] Accordingly, the present invention has been described at
some degree of particularity directed to the exemplary embodiments
of the present invention. It should be appreciated, though, that
the present invention is defined by the following claims construed
in light of the pr*or art so that modifications or changes may be
made to the exemplary embodiments of the present invention without
departing from the inventive concepts contained herein.
EQUIVALENTS
[0248] As will be apparent to those skilled in the art to which the
invention pertains, the present invention may be embodied in forms
other than those specifically disclosed above without departing
from the spirit or essential characteristics of the invention. The
particular embodiments of the invention described above are,
therefore, to be considered as illustrative and not restrictive.
The scope of the invention is as set forth in the appended claims
rather than being limited to the examples contained in the
foregoing description.
[0249] What is claimed as new and desired to be protected by
letters patent is set forth in the following claims.
* * * * *