Title: Method and apparatus for producing optical recording media with accurately parallel surfaces
Abstract: An apparatus and method that produces recording media using at least two platens. A first platen is movable relative to a second platen, and each platen has respective first and second support surfaces onto which substrates are placed, the first and second substrates each having inner and outer longitudinal surfaces. A centering device aligns the respective substrates relative to a one or more reference positions, a positioning system provides a degree of parallelism between the outer longitudinal surfaces of each of the substrates and produces a desired gap between the inner longitudinal surfaces of the substrates, and a dispensing unit which emits a liquid medium within the gap between inner longitudinal surfaces of the substrates.
Patent Number: 6,881,464 Issued on 04/19/2005 to Waldman, et al.
| Inventors:
|
Waldman; David A. (Concord, MA);
Hopwood; Rod (Lexington, MA);
Ingwall; Richard T. (Newton, MA);
Panchu; YajPaul (Brighton, MA)
|
| Assignee:
|
Aprilis, Inc. (Maynard, MA)
|
| Appl. No.:
|
146497 |
| Filed:
|
May 14, 2002 |
| Current U.S. Class: |
428/64.1; 428/64.4; 156/288; 156/500 |
| Intern'l Class: |
B32B 003//02 |
| Field of Search: |
428/64.1,64.4,652,913
430/270.11,495.1,945
156/285,288,500,580
|
References Cited [Referenced By]
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| 5932045 | Aug., 1999 | Campbell et al. | 156/102.
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| 6231705 | May., 2001 | Kanashima et al.
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| 6348983 | Feb., 2002 | Curtis et al.
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| 6596104 | Jul., 2003 | Tomiyama | 156/64.
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| 6671073 | Dec., 2003 | Hegel.
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| 2002/0135829 | Sep., 2002 | Edwards et al.
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| 2002/0136143 | Sep., 2002 | Edwards.
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| 2003/0070765 | Apr., 2003 | Eichlseder | 156/580.
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| WO 99/07542 | Feb., 1999 | WO.
| |
Primary Examiner: Mulvaney; Elizabeth
Attorney, Agent or Firm: Hamilton, Brook, Smith & Reynolds, P.C.
Parent Case Text
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application No.
60/290,743, filed May 14, 2001, the entire teachings of which are
incorporated herein by reference.
Claims
What is claimed is:
1. A method for producing optical recording media, comprising the steps of:
aligning opposing support surfaces such that the opposing support surfaces
are substantially parallel;
disposing each of at least two or more substrates on a respective opposing
support surface or the at least two or more substrates together on a
single opposing support surface, the substrates having respective inner
and outer longitudinal surfaces;
aligning the substrates relative to one or more reference positions;
positioning the substrates to secure a state of parallelism between the
outer longitudinal surfaces of the substrates which is coincident with the
parallelism provided by the opposing support surfaces;
positioning the substrates to create a gap between the inner longitudinal
surfaces of the substrates while maintaining the secured state of
parallelism of the outer longitudinal surfaces of the substrates; and
dispensing a requisite amount of liquid to provide a medium between the
inner longitudinal surfaces of the substrates, wherein during dispensing
the liquid is in contact with inner longitudinal surfaces of the at least
two substrates.
2. The method of claim 1, wherein the support surfaces are provided by
rigid reference platens.
3. The method of claim 1, wherein the substrates are circular disks.
4. The method of claim 1, wherein the substrates are square shaped,
rectangular shaped, or oval shaped.
5. The method of claim 1, wherein the substrates have a center hole.
6. The method of claim 1, wherein the substrates are glass or plastic.
7. The method of claim 1, wherein the substrates have one or more straight
edges.
8. The method of claim 1, wherein the substrates have one or more curved
edges.
9. The method of claim 1, wherein the substrates have a thickness of about
between 0.1 mm to 5 mm and have a flatness of about between 1/10 to 20
waves per inch.
10. The method of claim 1, wherein the substrates have a thickness of about
between 0.1 mm to 5 mm and wherein the step of positioning the substrates
secures a parallelism between the longitudinal outer surfaces of about
between 10 .mu.radians to 5000 .mu.radians.
11. The method of claim 1, wherein aligning a reference portion of the
substrates and dispensing includes using a centering plug.
12. The method of claim 1, wherein aligning the substrates includes using a
centering device.
13. The method of claim 1, wherein aligning the substrates includes using a
two-point alignment along a curved edge.
14. The method of claim 1, wherein aligning the substrates includes using a
three point alignment of two or more straight edges.
15. The method of claim 1, wherein aligning the opposing support surfaces
includes using a three-point positioning system.
16. The method of claim 1, wherein positioning the substrates includes
using a three-point positioning system.
17. The method of claim 1, wherein the substrates have an inner diameter,
and positioning the substrates includes using a device applied through a
respective inner diameter of the substrates.
18. The method of claim 1, wherein dispensing includes dispensing the
liquid into the gap between substrates.
19. The method of claim 18, wherein dispensing includes dispensing the
liquid through a centering device used to align the substrates relative to
a center reference position.
20. The method of claim 1, wherein dispensing includes dispensing the
liquid through a device inserted into the inner diameter of one or more
disk substrates.
21. The method of claim 1, wherein dispensing includes dispensing the
liquid onto the substrate surfaces.
22. The method of claim 1, wherein dispensing includes sealing the gaps
between a device used for dispensing the liquid and the inner edges of the
substrates.
23. The method of claim 1, wherein dispensing includes applying a positive
pressure to the liquid so that it flows from the center region of the
substrates outward towards the outer edges of the substrates.
24. The method of claim 1, wherein dispensing includes dispensing the
liquid onto the substrate surfaces at a radius to form an annular region.
25. The method of claim 1, wherein dispensing includes dispensing the
liquid onto the substrate surfaces at two or more radii to form two or
more annular or helical regions.
26. The method of claim 1, wherein dispensing includes dispensing the
liquid between the inner surfaces of the substrates from the outer edges
to the inner edges of the substrates so that the liquid layer is uniform.
27. The method of claim 1, wherein dispensing includes dispensing the
liquid in a radial direction while displacing gas between the inner
surfaces of the substrates to the outer edges of the substrates so that
the liquid layer is uniform without trapped gas bubbles.
28. The method of claim 1, wherein dispensing includes dispensing the
liquid from one or more edges of square or rectangular-shaped substrates,
or substrates having both straight and curved edges, while displacing gas
between the inner longitudinal surfaces of the substrates to one or more
opposing edges of the substrates so that the liquid has a defined
thickness and is provided without trapped gas bubbles.
29. The method of claim 1, further comprising the step of treating the
liquid to stabilize the medium.
30. The method of claim 29, wherein the liquid is polymerizable and
treating includes using a heat treatment.
31. The method of claim 29, wherein the liquid is polymerizable and
treating includes using actinic irradiation.
32. The method of claim 29, wherein the liquid is polymerizable and
treating includes using UV irradiation.
33. The method of claim 29, wherein treating includes treating circular
regions of the liquid medium.
34. The method of claim 33, wherein the circular regions are continuous
tracks at or near the outer and the inner edges of the substrates.
35. The method of claim 33, wherein the circular regions are two or more
continuous tracks of different radii about the center of the substrates.
36. The method of claim 29, wherein treating includes treating helical
regions of the liquid medium.
37. The method of claim 29, wherein treating includes treating discrete
regions of the liquid medium.
38. The method of claim 37, wherein the discrete regions are abutting each
other.
39. The method of claim 37, wherein the, discrete regions are separate from
each other, or partially overlapping with each other.
40. The method of claim 1, wherein dispensing is achieved by the use of
capillary forces.
41. The method of claim 1, wherein dispensing includes applying compressive
force to the liquid by application of positive pressure to the substrates
so that the liquid flows towards the center and outer edge of substrates.
42. The method of claim 1, wherein dispensing includes injecting the liquid
between the substrates while the substrates are stationary or spinning
followed by spinning the substrates to cause the liquid medium to spread
outward towards the outer edges of the substrates.
43. The method of claim 42, wherein dispensing includes applying
compressive force to the liquid by application of positive pressure to the
substrates in combination with spinning the substrates.
44. The method of claim 1, further comprising the step of securing the
position of the substrates to maintain the state of parallelism between
the outer longitudinal surfaces of the substrates.
45. A method for producing optical recording media, comprising the steps
of:
placing each of at least two substrates on a respective support surface,
each substrate having respective inner and outer longitudinal surfaces;
aligning the substrates relative to one or more reference positions;
positioning the substrates relative to each other to create a gap between
the inner longitudinal surfaces of the substrates;
positioning the substrates to secure a state of parallelism between the
outer longitudinal surfaces of the substrates;
dispensing a liquid to provide a medium between the inner longitudinal
surfaces of the substrates, wherein during dispensing the liquid is in
contact with inner longitudinal surfaces of the at least two substrates;
and
treating the liquid to stabilize the medium.
46. The method of claim 45, wherein the gap is defined with the use of at
least one mechanical stop.
47. The method of claim 46, further comprising adjusting the location of
the at least one mechanical stop with the aid of at least one linear
distance sensor.
48. The method of claim 45, wherein the gap is defined by the use of one or
more linear distance sensors.
49. The method of claim 45, wherein the gap is predetermined with the use
of a set of spacers.
50. The method of claim 49, wherein the spacers are rigidly mounted onto
one of the support surfaces.
51. The method of claim 49, wherein the spacers are variably mounted onto
one of the support surfaces.
52. The method of claim 51, further comprising interactively adjusting the
height of the spacers with the aid of an optical measuring device which
measures the tilt angle of the substrates.
53. The method of claim 52, wherein using the optical measuring device
includes adjusting the height of the support surfaces until surface
reflections from the outer surfaces of the substrates are substantially
co-linear.
54. The method of claim 45, wherein positioning the substrates to secure a
state of parallelism includes using an optical measuring device which
measures the tilt angle of the substrates, and adjusting the position of
the support surfaces until surface reflection from the outer surfaces of
the substrates are substantially co-linear.
55. An apparatus for producing recording media, comprising:
at least two platens, a first platen being movable relative to a second
platen, and the first and second platens having respective first and
second support surfaces onto which respective first and second substrates
are placed, the first and second substrates each having inner and outer
longitudinal surfaces;
an alignment device which aligns the respective substrates relative to a
one or more reference positions;
a positioning system which provides a substantial degree of parallelism
between the outer longitudinal surfaces of each of the substrates and
produces a desired gap between the inner longitudinal surfaces of the
substrates; and
a dispensing unit which emits a liquid medium within the gap between inner
longitudinal surfaces of the substrates, wherein during dispensing the
liquid is in contact with inner longitudinal surfaces of the at least two
substrates.
56. The apparatus of claim 55, further comprising a treating device for
stabilizing the liquid medium.
57. The apparatus of claim 55, wherein the treating device uses UV
radiation.
58. The apparatus of claim 55, wherein the treating device uses actinic
radiation.
59. The apparatus of claim 55, wherein the treating device uses heat
treatment.
60. The apparatus of claim 55, further comprising a locking device which
secures in the desired degree of parallelism between the outer surfaces of
the substrates.
61. The apparatus of claim 60, wherein the locking mechanism includes a
ball that wedges between three tapered blocks to push the blocks against
three rigid shafts of the positioning system to prevent movement of the
three rigid shafts.
62. The apparatus of claim 55, wherein the dispensing unit includes a
single reservoir that holds the liquid medium, the reservoir being
connected to the centering device directly or with a tube that transmits
the medium from the reservoir to the centering device.
63. The apparatus of claim 55, wherein the dispensing unit includes a
multiplicity of reservoirs for holding a respective liquid medium, each
reservoir being connected to the centering device directly or with a
respective tube to transmit the respective medium from the reservoirs to
the centering device.
64. The apparatus of claim 55, wherein the inner surface of each substrate
is provided with a raised portion along the outer region of the
substrates, the raised portions reducing the distance between the inner
surfaces of the substrates.
65. The apparatus of claim 55, wherein the positioning system is a
three-point positioning system.
66. The apparatus of claim 65, wherein the three-point positioning system
includes rigid mounting spacers.
67. The apparatus of claim 65, wherein the three-point positioning system
includes variable mounting spacers.
68. The apparatus of claim 55, wherein the positioning system includes at
least one mechanical stop to define the gap.
69. The apparatus of claim 55, wherein the positioning system includes a
linear distance sensor that defines the gap.
70. The apparatus of claim 55, wherein the positioning system includes an
optical measuring device which measures the tilt angle of the substrates,
the desired degree of parallelism being achieved when the optical
measuring device determines that the surface reflection from the outer
surfaces of the substrates are co-linear.
71. The apparatus of claim 55, wherein the centering device is applied
through a respective inner diameter of the substrates.
72. An optical recording article, comprising:
at least two substrates; and
a medium disposed between the inner longitudinal surfaces of the two
substrates, the outer longitudinal surfaces of the substrates being
substantially parallel, wherein the optical recording article is prepared
by a process that includes the steps of:
positioning the substrates to create a gap between the inner longitudinal
surfaces of the substrates while maintaining the secured state of
parallelism of the outer longitudinal surfaces of the substrates; and
dispensing a requisite amount of liquid to provide a medium between the
inner longitudinal surfaces of the substrates, wherein during dispensing
the liquid is in contact with inner longitudinal surfaces of the at least
two substrates.
73. The article of claim 72, wherein the substrates are circular disks.
74. The article of claim 72, wherein the substrates have a center hole.
75. The article of claim 72, wherein the substrates are square shaped,
rectangular shaped, or oval shaped.
76. The article of claim 72, wherein the substrates have at least one
straight edge.
77. The article of claim 72, wherein the substrates have at least one
curved edge.
78. The article of claim 72, wherein the substrates are glass.
79. The article of claim 72, wherein the substrates are plastic.
80. The article of claim 72, wherein the substrates have a thickness of
about between 0.1 mm to 5 mm and have a flatness of about between 1/10 to
20 waves per inch.
81. The article of claim 72, wherein the substrates have a thickness of
about between 0.1 mm to 5 mm and have a parallelism between the
longitudinal outer surfaces of about between 10 .mu.radians and 5000
.mu.radians.
82. The article of claim 72, wherein the inner surface of each substrate is
provided with a raised portion along the outer region of the substrates,
the raised portions reducing the distance between the inner surfaces of
the substrates.
83. The method of claim 29 wherein the substrates have a parallelism
between the longitudinal outer surfaces of about between 10 .mu.radians to
5000 .mu.radians.
84. The method of claim 1 wherein
at least three or more substrates are disposed on opposing support
surfaces, the substrates having respective inner and outer longitudinal
surfaces; and
during dispensing the liquid is in contact with inner longitudinal surfaces
of the at least three substrates.
Description
BACKGROUND
This invention relates to a process for production of optical media in
which either an active recording medium or a bonding layer is encased
between two substrates.
Media used in certain optical data storage systems, for example digital
holographic data storage or digital video disk (DVD), preferably require
outer surfaces of the media to possess a high degree of parallelism in
order to lessen the complexity of servo systems used in existing drives or
those contemplated for holographic data storage. Methods utilized in the
industry for preparation of reasonably flat optical media (e.g. bonding
step in DVD manufacturing) are capable of implementing and maintaining
reasonable consistency for the thickness of the polymerizable bonding or
recording layer, but do not contemplate the benefits of the outer surfaces
of the media having a high degree of parallelism.
SUMMARY
Such optical media processing systems have been accepted in the industry,
and they are presumably considered to perform reasonably well for their
intended purpose. However, they are not without their shortcomings. In
particular, many of these systems are unable to account specifically for
the existence of wedge in the substrates which encase the media, due to
variations in the thickness of the substrates, or, additionally, the
medium between the substrates due to tilt of one substrate with respect to
the other. It is desirable, therefore, to produce optical recording media
with accurately parallel faces. The present invention implements a system
for the fabrication of disk media where a liquid recording or bonding
material is sandwiched between reasonably rigid substrates, such that the
outer surfaces of the finished media are of reasonable flatness and
exhibit a high degree of parallelism. This system can also be implemented
for media in the shape of a disk, square or rectangular card, or other
geometry suitable for optical storage, for example, oval-shaped medium, or
media having straight and curved edges.
In one aspect of the invention, a method for producing optical recording
media includes aligning opposing support surfaces such that the opposing
support surfaces are substantially parallel, and disposing at least one
substrate on each respective opposing support surface, or both substrates
on one opposing surface, each substrate having respective inner and outer
longitudinal surfaces. Each substrate is aligned relative to one or more
reference positions, and the substrates are positioned to secure a state
of parallelism between the outer longitudinal surfaces of the substrates
which is coincident with the parallelism provided by the opposing support
surfaces. Optionally, the secured position of the substrates is locked to
maintain the state of parallelism between the outer longitudinal surfaces
of the substrates. Then the substrates are positioned to create a gap
between the inner longitudinal surfaces of the substrates while
maintaining the secured state of parallelism of the outer longitudinal
surfaces of the substrates. A requisite amount of liquid is dispensed to
provide a medium between the inner longitudinal surfaces of the
substrates, and the liquid can be treated to stabilize the medium.
Embodiments of this aspect include one or more of the following features.
The alignment of the substrates, in the case of disk type substrates or
other substrates having a center hole, includes using a centering plug,
and moving the substrates relative to each other includes using a
three-point positioning system. The alignment of the substrates, such as
those with at least one curved edge, can also be accomplished through the
use of a two-point alignment along a curved edge, or the use of at least a
three-point alignment of two or more straight edges. Alternatively, a pin
expandable in diameter, or a collet can be applied to an inner diameter of
the substrates.
The liquid medium can be dispensed through the centering plug under
positive pressure so that the liquid medium flows from the center region
of the substrates outward towards the outer edges of the substrates.
Dispensing can also be achieved with suction or capillary action or by
rotation of the substrates, or in combination with rotation of the
substrates. Alternatively, the dispensing can occur through a device
inserted into an inner diameter of the substrates. The liquid can be
dispensed onto a substrate surface, for example, at a radius to form an
annular region, or at two or more radii to form two or more annular or
helical regions. The liquid medium can, by way of example, also be
dispensed through a needle inserted in the gap between the substrates. In
another embodiment, the liquid medium can be dispensed between the inner
surfaces of the substrates from the outer edges to the inner edges of the
substrates so that the liquid layer is uniform. A positive pressure can be
applied to the substrates to create a compressive force on the liquid so
that it flow towards the center and outer edges of the substrates. The
substrates can be stationary or they can be spinning during the dispensing
process.
The liquid medium is typically polymerizable and is treatable with heat
treatment, actinic irradiation, and/or UV irradiation, or combinations
thereof. In the case of square or rectangular shaped substrates, or
substrates having both straight and curved edges, the liquid medium can
also be dispensed under positive pressure, or by use of suction or
capillary action, into the gap between the substrates so that it flows
from along one edge to the opposing outer edge of the substrate.
Alternatively, a positive pressure can be applied to the substrates to
create a compressive force on the liquid so that it flows to form a
uniform medium between the edges of the substrates. The substrates can
have a thickness of about between 0.1 mm and 5 mm and a flatness of about
1/10 to 20 waves per inch. Further, the outer longitudinal surfaces of the
substrates can have a parallelism between them of about between 10
.mu.radians to 5000 .mu.radians.
In another aspect of the invention, a method for producing optical
recording media includes placing each of at least two substrates on a
respective support surface; aligning the substrates relative to a center
reference position in the case of disk-shaped substrates, or other
reference positions, such as one or more edges in the case of square or
rectangular-shaped substrates; locking or firmly securing the position of
the substrates to secure a degree of parallelism; moving the substrates
relative to each other until there is a desired gap between the inner
surfaces of the substrates; dispensing a liquid between adjacent
substrates to uniformly fill the gap between adjacent substrates with a
requisite amount of liquid medium; and treating the liquid medium to
stabilize the thickness of the liquid medium.
Embodiments of this aspect can include using a set of spacers that are
either rigidly mounted or variably mounted to a reference surface. If the
spacers are variably mounted, the height of the spacers can be adjusted
with the aid of an optical measuring device which measures the tilt angle
of the substrates, or with the aid of linear distance devices such as
interferometric devices or strain gauges. Alternatively, one or more
mechanical stops can be used to define the gap.
In yet another aspect of the invention, an apparatus for producing
recording media include at least two platens, a first platen being movable
relative to a second platen, and the platens having respective first and
second support surfaces onto which respective first and second substrates
are placed, the first and second substrates each having inner and outer
longitudinal surfaces. The apparatus also includes a centering device for
aligning disk-type substrates relative to a center reference position or
includes a device for positioning one or more edges to a reference
position for square or rectangular-shaped substrates, or substrates having
at least one curved edge, and a three-point positioning system for
providing a desired degree of parallelism between the outer surfaces of
the substrates, and to produce a desired gap between the substrates. A
locking device secures the desired degree of parallelism between the outer
surfaces of the substrates, and a dispensing unit emits a liquid medium
within the gap between the substrates. The liquid medium is stabilized
with a treating device in a manner to preserve the thickness of the
medium, and may also preserve the parallelism of the outer surfaces of the
substrates.
The locking mechanism can include a ball that wedges between three tapered
blocks to push the blocks against three rigid shafts of the positioning
system to prevent movement of the three rigid shafts.
In some embodiments, the dispensing unit includes a single reservoir that
holds the liquid medium. The reservoir, in the case of disk-type
substrates, is directly connected to the centering hub, or other suitable
device contemplated for dispensing the liquid medium, or alternatively is
connected with a tube that transmits the medium from the reservoir to the
centering hub or other suitable dispensing device. In other embodiments,
the dispensing unit includes a multiplicity of reservoirs for holding a
respective liquid medium. In the case of disk-type substrates, each such
reservoir is connected directly to the centering hub or other suitable
dispensing devices, or is connected with a respective tube to transmit the
respective medium from the reservoir to the centering hub or other
suitable dispensing device. The centering hub, or other suitable
dispensing devices in the case of square or rectangular-shaped substrates,
or substrates containing at least one curved edge, can contain a mixing
chamber when the dispensing unit includes a multiplicity of reservoirs.
The mixing chamber can contain structural elements or protrusions. As the
flow of liquids introduced into the chamber encounters these protrusions,
turbulence is produced in the liquids, which facilitates mixing of
multiple liquid components into a uniform solution.
The inner surface of each substrate can be provided with a raised portion
along the outer region of the substrates. The raised portions reduce the
distance between the inner surfaces of the substrates. The three-point
positioning system can include rigid mounting spacers or variable mounting
spacers for defining a desirable gap between the inner surfaces of the
substrates.
Among other advantages, the foregoing system and method permits preparation
of media capable for use in optical recording that require a high degree
of parallelism of the outer surfaces of the substrates. Such a system and
method takes into account and compensates for the wedge in the substrates.
Furthermore, it provides a means by which liquid materials can be
introduced between substrates into gaps of various dimensions, and the
liquid is uniformly distributed within the gap without the presence of air
bubbles. If the liquid media are polymerizable then this system and method
provides a way for reacting the material by thermal and/or photo-chemical
methods so as to secure and maintain the defined parallelism between outer
surfaces of the substrates of the media. The system and method described
for dispensing the fluid material within the gap dimensions can be used
for a wide range of viscosities for fluids used or contemplated for use in
DVD bonding or bonding of other types of optical storage media such as
disks of other sizes or cards, and/or holographic recording media. The
methods described for securing and maintaining the defined high degree of
parallelism between outer surfaces of the substrates can also serve as
providing for structural features that are useful for optical servo
systems.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, features and advantages of the invention
will be apparent from the following more particular description of
preferred embodiments of the invention, as illustrated in the accompanying
drawings in which like reference characters refer to the same parts
throughout the different views. The drawings are not necessary to scale,
emphasis instead being placed upon illustrating the principles of the
invention.
FIG. 1 is a front view of an optical recoding media producing system in
accordance with the invention.
FIGS. 2A and 2B are side views of the optical recording media producing
system of FIG. 1.
FIG. 2C is a top view of a locking mechanism of the system of FIG. 1.
FIG. 3 is a side view of a centering hub to align substrates and dispense a
liquid medium between adjacent substrates.
FIG. 4 is a flow diagram of a sequence of automated steps to produce
optical recording media.
FIGS. 5A and 5B is an alternative embodiment of a three-point positioning
system for the media producing system of FIG. 1.
FIG. 6 is another alternative embodiment of a three-point positioning
system.
FIGS. 7A and 7B illustrate an alternative embodiment of a centering hub to
dispense multiple liquid media.
FIG. 8 is a side view of a pair of substrates provided with gaskets or
raised portions to prevent the overflow of liquid medium beyond the outer
edges of the substrates.
DETAILED DESCRIPTION OF THE INVENTION
A description of preferred embodiments of the invention follows.
The optical recording media producing system of the present invention is
illustrated generally at 10 in FIG. 1. The media producing system 10 is a
system to fabricate optical media in which an active recording medium (or
a bonding layer as used in DVD technology) is encased between two
substrates. A particular feature of the system 10 is that it is able to
produce a medium with a high degree of parallelism between the outer
surfaces of the substrates. Additionally, the medium is produced uniformly
without the presence of trapped gas bubbles within the medium. Each
substrate may be a single sheet or disk of plastic or glass, or may
consist of laminated sheets or disks of plastic and/or glass that sandwich
other bonding or recording layers. The sheet may be square or rectangular
or oval, or have a shape of any other suitable geometry that may contain
straight and/or curved edges.
As an overview, when the system 10 is in use, an operator places each of
two substrates 12, 14 on a respective support surface, such as the inner
surfaces of a lower platen 16 and an upper platen 18. These platens are
fabricated to provide a high degree of surface flatness and surface
quality that may generally be referred to as optical flatness. A desired
degree of parallelism between the inner longitudinal surfaces of the
platens, i.e., the opposing support surfaces, is achieved and the state of
parallelism is secured such that the inner longitudinal surfaces of the
platens are substantially parallel before the substrates are placed on the
platens.
Once placed on the platens, the central axes with respect to the
longitudinal surfaces of the substrates, if they are disk-type substrates,
are aligned to a center reference position with a centering hub 19, and
the substrates 12, 14 are then brought together so that the inner surfaces
of the substrates 12, 14 are in contact with each other. The
center-aligned positions of the disk-type substrates are maintained by
securing the substrates to the platens, thereby establishing and locking
in parallelism between the outer longitudinal surfaces of the substrates
to maintain the achieved level of parallelism between the platens.
Similarly, aligned positions of square or rectangular-shaped substrates or
other suitably shaped substrates are maintained by securing the substrates
to the platens, thereby establishing and locking in parallelism between
the outer surfaces of the substrates to maintain the achieved level of
parallelism between the platens. The substrates can have a thickness of
about between 0.1 mm to 5 mm and have a flatness of about 1/10 to 20 waves
per inch. The parallelism between the longitudinal outer surfaces of the
substrates is about between 10 .mu.radians and 5000 .mu.radians.
The substrates are then brought slightly apart, for example, by dialing in
a gap with a control panel 21. A dispensing unit 17, which includes a
dispensing reservoir 22 connected to the centering hub 19, in the case of
disk-type substrates, with a tube 26, dispenses a liquid medium from the
centering hub 19 and into the defined gap between the substrates 12, 14.
Similarly, the dispensing unit 17, which includes the dispensing reservoir
22 and the tube 26, or some other means of carrying the fluid, dispenses a
liquid medium from along one edge of rectangular or square-shaped
substrates or other suitably shape substrates, or from any other region
between the substrates into the defined gap between the substrates.
After the liquid medium fills the gap, a treating device 23 is used to
stabilize the liquid medium that is usually a polymerizable substance.
Alternatively, rather than using the centering hub 19 to center the
substrates and to dispense the liquid medium, a separate centering device
can be used to center the substrates, and then a different dispensing hub
can be employed to dispense the liquid. Particular features of the system
10 and the process to produce the recording medium are described in detail
below.
The system 10 also includes a vacuum source 28 which is connected to both
the lower and upper platens 16, 18 with a set of vacuum lines 30. The
lower and upper platens 16, 18 are provided with a series of holes
connected to submerged tracks (not shown) so that the vacuum source 28
draws a vacuum through the lines 30 and the series of holes in each of the
platens to create suction in the submerged tracks to hold the substrates
to the platens. In the embodiment shown in FIG. 1, the upper platen 18 is
rigidly affixed to the upper portion of a support base 24 of the system
10. The lower platen 16, on the other hand, moves up and down in the
direction of the double arrow A--A. Alternatively, the substrates 12, 14
can be secured to the platens by any other suitable mechanism, and/or the
upper platen 18 is moveable while the lower platen 16 remains stationary.
The system 10 is provided with a three-point positioning system 32 that
facilitates aligning the substrates 12, 14 so that the outer surfaces of
the substrates are highly parallel. The positioning system 32 includes
three rigid shafts 34, 36, and 38, each shaft having an upper end
protruding into an upper frame 40 and provided with a V-shaped groove 42
in which a ball 44 sits. The lower platen 16 sits on top of the three
balls 44. The three rigid shafts 34, 36, and 38 are positioned to provide
a three-point support for the lower platen 16. The lower ends of the rigid
shafts 34, 36, and 38 are mounted in a lower frame 46 in a manner which
allows the lower ends to slide up and down in a respective hole 48 of the
lower frame 46. The lower ends of the rigid shafts 34, 36, and 38 are also
provided with a set of springs 50 which are arranged to push the rigid
shafts 34, 36, and 38 away from the lower frame 46. An enlarged end 47 of
each shaft 34, 36, and 38 has a diameter that is larger than the diameter
of the respective holes 48 to prevent the shafts from completely sliding
out of the holes 48.
The lower frame 46 is also able to move up and down in the direction of the
double arrow A--A. The lower frame 46 is connected to a stationary drive
motor 52 through a screw drive 54 (or, alternatively, a piston driven by
hydraulic or gas pressure). The lower frame 46 and the screw drive 54 are
coupled together in a manner that converts rotary motion of the screw
drive 54 to linear movement of the lower frame 46. Hence, as the lower
frame 46 moves upwards, a compressive force is imparted to each of the
rigid shafts 34, 36, and 38 through the respective springs 50. Note that
each of the shafts 34, 36, and 38 are moveable independently of each
other. Thus as the lower frame 46 moves upward, the compressive force
imparted to each shaft is transferred to the base of the lower platen 18
in a manner such that the compressive force can differ to facilitate
adjusting and reducing the tilt of the inner surface of the lower platen
16 relative to the inner surface of the upper platen 18.
Referring now to FIGS. 2A and 2C, there is shown a locking mechanism 60
used to secure the lower and upper platens 16, 18 in place after the
desired degree of parallelism has been achieved. The locking mechanism 60
includes three tapered blocks 62, 63, and 64. A ball 66 that is positioned
directly above a moveable platform 68 is located within a cone shaped
inner region 70 defined by the three tapered blocks 62, 63, and 64. The
three tapered blocks 62, 63, and 64 move independently from one another
and are positioned next to a respective rigid shaft 38, 34, and 36.
After the drive motor 52 rotates the screw drive 54 to move the lower
platform 46 and hence the lower platen 16 upwards such that the inner
surfaces of the platens 16, 18 achieve the desired degree of parallelism,
the lower platform 46 will be slightly deflected as indicated by ".DELTA."
(FIG. 2B). The operator locks the lower platen 16 in place by moving a
handle 55 into a locking position (the locking mechanism is released by
moving the handle 55 in the opposite direction). The movement of the
handle 55 causes the platform 68 and hence the ball 66 to rise upwards. As
the ball 66 moves upwards, it pushes against the inner surfaces of the
three tapered blocks 62, 63, and 64 in a manner that causes the three
tapered blocks to move outwards in the direction of the arrow B against
the rigid shafts 34, 36, and 38. The position of the ball 66 is locked in
place such that friction between the outer surfaces of the three tapered
blocks 62, 63, and 64 and the respective rigid shafts 38, 34, and 36
prevents the shafts from moving. Other methods of securing and locking the
positions of the platens 16, 18 to achieve the desired degree of
parallelism between the inner surfaces of 16, 18 are also contemplated.
Referring now to FIG. 3 and back to FIG. 1, to fill the gap between the
substrates 12, 14, the liquid medium flows from the dispensing reservoir
22, in the case of disk-type substrates, to the centering hub 19 and
collects in an inner chamber 82 of the centering hub 19. From the inner
chamber 82, the liquid medium is emitted through a series of horizontal
orifices 84, extending from the inner chamber 82 to the outer surface of
the centering hub 19, and fills the entire gap region between the two
substrates 12, 14. Alternatively, the liquid medium is emitted through a
continuous orifice from the inner chamber 82. The tube 26 is made of
stainless steel, Teflon, Teflon coated tubing, or any other suitable
material that is chemically inert to the liquid medium. The centering hub
19 is provided with two O-rings 90 that form a seal with the inner edges
of the substrates 12, 14 to prevent the liquid medium from flowing between
the centering hub 19 and the outer surfaces of the substrates 12, 14.
Other methods of providing a seal with the substrates to prevent the
liquid medium from flowing onto the outer surfaces of the substrates 12,14
are also contemplated.
In one embodiment, a vacuum pump or source 85 is connected to the centering
hub 19 with a tube 86, and the centering hub 19 is provided with an inner
channel 87 extending from the point of connection with the tube 86 to a
region above the top O-ring 90. The vacuum source 85 draws a vacuum to
seal the centering hub 19 by suction to the substrates, so that the medium
can be dispensed under specific environmental conditions, such as, for
example, anhydrous and/or anaerobic conditions exclusively to the region
of the gap between the substrates. Alternatively, the dispensing device
can be sealed by application of suction in a manner such that the device
seals to the outer surface of the topmost substrate and to the bottom
platen such as within the inner diameter of the platen. As the dispensed
liquid flows uniformly in the radial direction from the centering hub 19
to the outer edges of the substrates 12, 14, the defined gap dimension
between the inner surfaces of the substrates 12, 14 remains fixed.
Further, the dispensed liquid medium uniformly displaces the gas between
the inner surfaces of the substrates 12, 14 as the liquid medium flows
towards the outer edges of the substrates 12, 14, thereby forming a
uniform liquid layer of a defined thickness void of any trapped gas
bubbles. The positive pressure setting used to dispense the liquid medium
can be adjusted in accordance with the viscosity of the fluid to ensure
rapid dispensing of the liquid into the region between the substrates 12,
14. Alternatively, the requisite amount of fluid can be dispensed by
linear motion of a piston that is located within the dispensing device or
at a suitable position outside the device, such as by a cylindrical piston
that is positionally controlled by use of hydraulic or gas pressure or
other suitable means that may for example use actuators.
The liquid medium is typically polymerizable such that it can be treated
and stabilized in a number of ways. For instance, the treating device 23
(FIG. 1) used to stabilize the liquid medium after it has been dispensed
can be a series of light emitting diodes (LEDs) positioned over the inner
surfaces of one or both platens. The LEDs emit visible radiation that is
transmitted through the transparent substrates to the liquid medium.
Alternatively, UV radiation, actinic radiation, or heat treatment sources
can be used alone or in combination to stabilize the liquid medium. If UV
or actinic radiation is employed, the polymerizable liquid must be
photo-chemically active to the wavelength of the radiation. Alternatively,
or in combination with above, the edges of the polymerizable liquid medium
at or near the edges of the substrates can be treated by application of UV
radiation, actinic radiation, or heat treatment sources. Typical sources
of actinic radiation include LEDs, laser diodes, other laser sources,
strobe flash sources such as Xenon flash units, incandescent sources,
halogen lamps, and the like.
Referring now to FIG. 4, there is shown a process 1000 for fabricating
optical recording media with the system 10.
First, in a step 1002, the operator or computer controller activates the
drive motor 52 thereby raising the lower frame 46 in the Z-direction.
Hence, the lower platen is 16 is moved upwards until it is in contact with
the upper platen 18. The two platens are brought together so that there is
no gap between them. The uniform intimate contact between the inner
longitudinal surfaces of the platens defines the desired high degree of
parallelism such that the inner longitudinal surfaces of the platens are
substantially parallel.
Next, in a step 1004, the locking mechanism 60 is activated to secure the
state of parallelism achieved between the inner surfaces of the platens
16, 18.
Subsequently, in a step 1006, the drive motor 52 separates the platens 16,
18 to adjust the distance between the platens so that the substrates 12,
14 can be positioned between the platens. Then in a step 1007 the
substrates 12, 14 are placed separately or together on opposing inner
surfaces of the respective platens 16, 18. That is, each substrate can be
placed on respective opposing inner surfaces or both substrates can be
placed on one opposing inner surface.
Next, in a step 1008, the operator uses the centering hub 19 to align the
central axes of the substrates 12, 14 to a reference center position or
location. In this embodiment, for example, the center plug 19 is inserted
in the inner diameter holes of the platens 16,18 and the substrates 12, 14
to align the substrates relative to each other and to the center of the
platens. Alternatively, a two-point alignment system can be used that, for
example, touches two points along the curved surface of the substrates 12,
14 in a manner such that the touch points are located at a fixed position
relative to the reference center location of the platens, or a pin
expandable in diameter, or a collet can be applied to the inner diameters
of the substrates. Then in a step 1010, the substrates 12, 14 are secured
to the platens 16, 18 with a suction created with a vacuum drawn by the
vacuum source 28.
Afterwards, in a step 1012, the drive motor 52 raises the lower frame 46 in
the Z-direction. Hence, the lower platen 16 is moved upwards until the
lower substrate 12 is in contact with the upper substrate 14 secured to
the upper platen 18. The two substrates 12, 14 are brought together to
define the zero gap position between the two substrates. The uniform
intimate contact between the outer longitudinal surfaces of the substrates
and the inner longitudinal surfaces of the platens assures that the
desired high degree of parallelism between the outer surfaces of the
substrates 12, 14 is coincident with the parallelism exhibited between the
inner surfaces of the platens 16, 18. Then, as the top platen 18 remains
fixed in place, the lower platen 16 is moved in the Z-direction to provide
the desired gap between the inner opposing surfaces of the two substrates
12, 14. Note that while the lower platen 16 is moved, the achieved state
of parallelism is unperturbed. Alternatively, the lower platen 16 is moved
in the Z-direction to a defined location, such as by use of one or more
mechanical stops, to provide the desired gap between the inner opposing
surfaces of the two substrates 12, 14.
Next, in a step 1014, the liquid medium is dispensed through the centering
plug 19 to fill the space of the gap between the inner surfaces of the
substrates 12, 14. In particular, the fluid is emitted through the
horizontal holes 84 of the centering hub 19 under positive pressure so
that the fluid flows outward from the centering hub 19 towards the outer
edges of the substrates 12, 14 to fill the entire gap between the two
substrates. Although the fluid is under a positive pressure, the O-rings
90 prevent the fluid medium from flowing into the region between the
centering plug 19 and the inner edges of the substrates 12, 14.
Alternatively, the liquid medium can be dispensed through a device inserted
near the inner edge of the substrates. The device can dispense the liquid
medium onto the substrate surface, for example, at a radius to form an
annular region, or at two or more radii to form two or more annular or
helical regions. The liquid medium can alternatively be dispensed between
the inner surfaces of the substrates from the outer edges to the inner
edges of the substrates to form a uniform liquid layer. A needle can be
inserted into the gap between the substrates through which the liquid
medium is dispensed. Furthermore, by applying a positive pressure to the
substrates, a compressive force can be applied to the liquid medium so
that the liquid medium flows towards the center and the outer edges of the
substrates to form a uniform liquid layer. The compressive force can be
applied while the substrates are stationary, or while they are spinning.
After the medium fills the gap between the substrates, the medium is
treated with UV radiation emitted from the treating device 23, in a step
1016, to stabilize the structure of the medium. Alternatively, actinic
radiation or heat treatment, or combinations thereof, can be used to treat
the polymerizable liquid layer.
Application of heat treatment or irradiation can be directed to regions of
dispensed liquid located between the inner surfaces of substrates and
abutting the inner and outer edges of the substrates. For example, these
regions can be circular in a continuous track around the disk near the
outer and inner edges of the disk, or the regions can be helical shaped
tracks. In another embodiment, application of heat or irradiation can
occur additionally or independently at locations between the inner and
outer edges of the substrates, which by way of example could be other
continuous tracks of different radii, or small circular spots at locations
arranged in concentric rings or helical shaped tracks, about the center
hole of the substrates 12, 14. Other examples include application of heat
or irradiation to create localized polymerized regions in the form of
discrete spots of various geometric shapes and sizes at particularly
desirable locations. These spots can be fully separated, or perhaps
partially overlapping, in groups of spots. Such groups could be abutting
or separated from other such groups. By way of example, these spots can be
located in circular or helical type tracks around the disk at any desired
location of the disk, or in rows or columns or other particularly useful
configurations at any desired location in the case of square or
rectangular-shaped or other suitably shaped substrates. The extent of
polymerization resulting from the heat or irradiation treatment is
sufficient to form locations of polymerized structure that exhibit
requisite mechanical integrity, and the dimensions of the spots or rings,
in which such polymerization takes place, is sufficient to provide for
overall requisite mechanical integrity to maintain the state of
parallelism.
The regions that are polymerized for the purpose of maintaining the high
degree of parallelism between the outer surfaces of the substrates can
also be used as structural features designed for providing servo features
in the finished optical media. For example, if the polymerized regions are
created in a manner that results in formation of holograms at these
locations, then changes in reflectivity from these regions, due to
diffraction by the holograms, can be used for optical servo methods. For
example, reflection holograms can be recorded in these regions during
light induced polymerization by use of light emitting devices, such as
diodes or lasers or flash lamps. The locations of these reflection
holograms can be used to diffract light of a particular wavelength at a
particular angle useful for optical servo systems.
In the embodiment described above, the gap between inner surfaces of the
substrates 12, 14 is created by moving the lower platen away from the
upper platen a predetermined distance as dialed in with the control panel
21. There are, however, other mechanisms that can be used to create this
gap. For instance, there is shown in FIGS. 5A and 5B, a lower platen 2000
provided with a set of three rigid spacers 2002 shaped as spherical balls
which sit on top of an inner surface 2004 (serving as a reference surface)
of the bottom platen 2000 and are secured to the bottom platen 2000 with a
respective pin 2006. The three spacers are positioned equidistance from
each other about the outer region of the lower platen 2000, but may be
positioned at any suitable distance from each other about the outer region
or inner regions of the lower platen 2000 or any other region that is
inside and/or outside of where substrates will be positioned. A gap,
"h.sub.1 ", is created between the two platens by moving the lower platen
2000 towards an upper platen 2010 with, for example, a drive mechanism as
described above, until the top of the three spacers 2002 are in contact
with the inner surface 2012 of the upper platen 2010. Alternatively, the
lower platen 2000 can be stationary while the upper platen 2010 is moved.
In either case, the gap "h.sub.1 " between the inner surfaces of the upper
platen 2010 and the lower platen 2000 is the same as the diameter of the
three spacers 2002 and would be equal to the aggregate of the thickness of
the substrates and the desired thickness of the liquid medium. In the case
of a multiplicity of square or rectangular-shaped substrates positioned
between inner surfaces of the platens 2004, 2012 there may be more than
three of such rigid spacers 2002 shaped as spherical balls which sit on
top of an inner surface 2004 (serving as a reference surface) of the
bottom platen 2000. In other embodiments, the gap is defined with the use
of o
