U.S. patent application number 10/874974 was filed with the patent office on 2004-11-18 for method and apparatus for producing data storage media.
Invention is credited to Gorczyca, Thomas Bert, Meyer, Laura Jean.
Application Number | 20040227263 10/874974 |
Document ID | / |
Family ID | 24736950 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040227263 |
Kind Code |
A1 |
Gorczyca, Thomas Bert ; et
al. |
November 18, 2004 |
Method and apparatus for producing data storage media
Abstract
In one embodiment, the method for producing a stamper,
comprises: forming a nickel plated substrate having desired surface
features on one side; disposing a managed heat transfer layer on a
second side of said substrate; forming a thickness of said managed
heat transfer layer having a variation of less than about 5%; and
altering said exposed surface of said managed heat transfer layer.
Also disclosed are a method and apparatus for producing data
storage media.
Inventors: |
Gorczyca, Thomas Bert;
(Schenectady, NY) ; Meyer, Laura Jean;
(Schenectady, NY) |
Correspondence
Address: |
General Electric Company
CRD Patent Docket Rm 4A59
Bldg. K1
P.O. Box 8
Schenectady
NY
12301
US
|
Family ID: |
24736950 |
Appl. No.: |
10/874974 |
Filed: |
June 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10874974 |
Jun 23, 2004 |
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09681816 |
Jun 11, 2001 |
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6787071 |
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Current U.S.
Class: |
264/1.33 ;
264/2.5; 425/810 |
Current CPC
Class: |
Y10S 425/81 20130101;
B29C 33/04 20130101; B29D 17/005 20130101; B29C 2045/2636 20130101;
B29C 2045/2634 20130101; B29C 2043/025 20130101; B29C 33/60
20130101; B29C 43/021 20130101; B29C 45/2632 20130101 |
Class at
Publication: |
264/001.33 ;
264/002.5; 425/810 |
International
Class: |
B29D 011/00 |
Claims
What is claimed is:
1. A method for manufacturing an article, comprising: disposing a
managed heat transfer layer in operable communication with a second
surface of a stamper, wherein a first surface of said stamper
comprises surface features, wherein an exposed surface of said
managed heat transfer layer has been altered by a method selected
from the group consisting of chemically, mechanically, or a
combination thereof; disposing the stamper in a mold with at least
a portion of said exposed surface disposed in operable
communication with a mold half; injecting a molten plastic into
said mold; cooling the plastic to form said data storage media; and
releasing said data storage media from said mold.
2. The method of claim 1, further comprising forming a thickness of
said managed heat transfer layer having a variation of less than
about 5%.
3. The method of claim 2, wherein forming said substantially
uniform thickness further comprises surface lapping said exposed
surface.
4. The method of claim 3, wherein said thickness varies less than
about 3%.
5. The method of claim 4, wherein said thickness varies less than
about 1%.
6. The method of claim 5, wherein said thickness varies less than
about 0.5%.
7. The method of claim 2, wherein said lapping further comprises
grinding with sand paper having a grit particle size of less than
or equal to about 9 micrometers.
8. The method of claim 1, wherein said chemically altered exposed
surface comprises a polymer chain length shorter than a
non-chemically altered portion said managed heat transfer
layer.
9. The method of claim 1, wherein said managed heat transfer layer
comprises a material selected from the group consisting of
thermoset materials, plastics, porous metals, ceramics,
low-conductivity metal alloys, and cermets, composites, reaction
products, and combinations comprising at least one of the foregoing
materials.
10. The method of claim 9, wherein said material is selected from
the group consisting of polyimides, polyamideimides, polyamides,
polysulfone, polyethersulfone, polytetrafluoroethylene,
polyetherketone, and composites, reaction products, and
combinations comprising at least one of the foregoing
materials.
11. The method of claim 1, wherein said managed heat transfer layer
further comprises a lubricant component either incorporated into
the managed heat transfer layer or placed on its surface.
12. The method of claim 11, wherein lubricant is selected from the
group consisting of molybdenum disulfide (MOS.sub.2), graphite
fluoride (CF.sub.1.1)).sub.n, and reaction products and
combinations comprising at least one of the foregoing
lubricants.
13. The method of claim 11, wherein said managed heat transfer
layer comprises about 5 wt % to about 60 wt % of said lubricant,
based upon the total weight of the managed heat transfer layer.
14. The method of claim 13, wherein said managed heat transfer
layer comprises about 5 wt % to about 50 wt % of said lubricant,
based upon the total weight of the managed heat transfer layer.
15. The method of claim 14, wherein said managed heat transfer
layer comprises about 10 wt % to about 40 wt % of said lubricant,
based upon the total weight of the managed heat transfer layer.
16. The method of claim 11, wherein said lubricant is in the form
of a layer disposed on said exposed surface.
17. The method of claim 16, wherein said lubricant layer has a
thickness of less than or equal to about 1 micrometer.
18. The method of claim 17, wherein said thickness is about 0.01
micrometers to about 0.10 micrometers.
19. The method of claim 1, wherein said exposed surface further
comprises an area of roughness where said exposed surface operably
communicates with said mold, wherein said roughness is less than or
equal to about 0.50 micrometers, as measured from a plane of said
managed heat transfer surface.
20. The method of claim 19, wherein said roughness is about 0.20
micrometers to about 0.40 micrometers.
21. The method of claim 20, wherein said roughness is about 0.25
micrometers to about 0.30 micrometers.
22. The method of claim 1, wherein a coefficient of friction of
greater than or equal to about 0.50 exists in an area of physical
contact between said managed heat transfer layer and said
support.
23. The method of claim 1, wherein said article is a data storage
media.
24. A molding apparatus for producing a data storage media
comprising: a stamper comprising a managed heat transfer layer,
wherein a first surface of said stamper comprises surface features,
and wherein an exposed surface of said managed heat transfer layer
has been altered by a method selected from the group consisting of
chemically, mechanically, or a combination thereof, and has a
thickness variation of less than about 5%; and a support for
receiving the stamper by operable communication with said managed
heat transfer layer.
25. The molding apparatus of claim 24, wherein said managed heat
transfer layer comprises a material selected from the group
consisting of thermoset materials, plastics, porous metals,
ceramics, low-conductivity metal alloys, and cermets, composites,
reaction products, and combinations comprising at least one of the
foregoing materials.
26. The molding apparatus of claim 25, wherein said material is
selected from the group consisting of polyimides, polyamideimides,
polyamides, polysulfone, polyethersulfone, polytetrafluoroethylene,
polyetherketone, and composites, reaction products, and
combinations comprising at least one of the foregoing
materials.
27. The molding apparatus of claim 24, wherein said managed heat
transfer layer further comprises a lubricant.
28. The molding apparatus of claim 27, wherein lubricant is
selected from the group consisting of molybdenum disulfide
(MOS.sub.2), graphite fluoride (CF.sub.1.1)).sub.n, and reaction
products and combinations comprising at least one of the foregoing
lubricants.
29. The molding apparatus of claim 27, wherein said managed heat
transfer layer comprises about 5 wt % to about 60 wt % of said
lubricant based upon the total weight of the managed heat transfer
layer.
30. The molding apparatus of claim 29, wherein said managed heat
transfer layer comprises about 5 wt % to about 50 wt % of said
lubricant based upon the total weight of the managed heat transfer
layer.
31. The molding apparatus of claim 30, wherein said managed heat
transfer layer comprises about 10 wt % to about 40 wt % of said
lubricant based upon the total weight of the managed heat transfer
layer.
32. The molding apparatus of claim 31, wherein said lubricant is in
the form of a layer disposed on said exposed surface.
33. The molding apparatus of claim 32, wherein said lubricant layer
has a thickness of less than or equal to about 1 micrometer.
34. The molding apparatus of claim 33, wherein said thickness is
about 0.01 micrometers to about 0.10 micrometers.
35. The molding apparatus of claim 24, wherein said exposed surface
further comprises an area of roughness where said exposed surface
operably communicates with said mold, wherein said roughness is
less than or equal to about 0.50 micrometers as measured from a
plane of said managed heat transfer surface.
36. The molding apparatus of claim 35, wherein said roughness is
about 0.20 micrometers to about 0.40 micrometers.
37. The molding apparatus of claim 36, wherein said roughness is
about 0.25 micrometers to about 0.30 micrometers.
38. The molding apparatus of claim 24, further comprising a
coefficient of friction of greater than or equal to about 0.50 in
an area of physical contact between said managed heat transfer
layer and said support.
39. A method for producing a stamper, comprising: forming a nickel
plated substrate having desired surface features on one side;
disposing a managed heat transfer layer on a second side of said
substrate; forming a thickness of said managed heat transfer layer
having a variation of less than about 5%; and altering an exposed
surface of said managed heat transfer layer, wherein said altering
is by a method selected from the group consisting of chemically
altering, mechanically altering, or a combination thereof.
40. The method of claim 39, wherein said chemically altering said
exposed surface further comprises reactive ion etching with a
selected from the group consisting of oxygen, chlorine,
hydrochloric acid, fluorocarbons, nitrogen, nitrogen oxides, argon,
boron trichloride, hydrogen, sulfur hexafluoride, and ions,
reaction products, and combinations comprising at least one of the
foregoing gases.
41. The method of claim 39, wherein chemically altering said
exposed surface further comprises exposing said exposed surface to
an aqueous caustic solution.
42. The method as in claim 41, wherein said aqueous caustic
solution comprises potassium hydroxide.
43. The method of claim 39, wherein forming said thickness further
comprises surface lapping said exposed surface.
44. The method of claim 43, wherein said thickness varies less than
about 3%.
45. The method of claim 44, wherein said thickness varies less than
about 1%.
46. The method of claim 45, wherein said thickness varies less than
about 0.5%.
47. The method of claim 43, wherein said lapping further comprises
grinding with sand paper having a particle size of less than or
equal to about 5 micrometers.
48. The method of claim 40, wherein chemically altering said
exposed surface further comprises shortening a polymer chain length
of plastic disposed at said exposed surface.
49. The method of claim 39, wherein said managed heat transfer
layer comprises a material selected from the group consisting of
thermoset materials, plastics, porous metals, ceramics,
low-conductivity metal alloys, and cermets, composites, reaction
products, and combinations comprising at least one of the foregoing
materials.
50. The method of claim 49, wherein said material is selected from
the group consisting of polyimides, polyamideimides, polyamides,
polysulfone, polyethersulfone, polytetrafluoroethylene,
polyetherketone, and composites, reaction products, and
combinations comprising at least one of the foregoing
materials.
51. The method of claim 39, wherein said managed heat transfer
layer further comprises a lubricant.
52. The method of claim 49, wherein lubricant is selected from the
group consisting of molybdenum disulfide (MOS.sub.2), graphite
fluoride (CF.sub.1.1)).sub.n, and reaction products and
combinations comprising at least one of the foregoing
lubricants.
53. The method of claim 49, wherein said managed heat transfer
layer comprises about 5 wt % to about 60 wt % of said lubricant
based upon the total weight of the managed heat transfer layer.
54. The method of claim 53, wherein said managed heat transfer
layer comprises about 5 wt % to about 50 wt % of said lubricant
based upon the total weight of the managed heat transfer layer.
55. The method of claim 54, wherein said managed heat transfer
layer comprises about 10 wt % to about 40 wt % of said lubricant
based upon the total weight of the managed heat transfer layer.
56. The method of claim 39, further comprising forming a lubricant
layer on said exposed surface.
57. The method of claim 56, wherein said lubricant layer has a
thickness of less than or equal to 1 micrometer.
58. The method of claim 57, wherein said thickness is about 0.01
micrometer to about 0.10 micrometer.
59. The method of claim 39, wherein said exposed surface further
comprises an area of roughness where said exposed surface operably
communicates with said mold, wherein said roughness is less than or
equal to about 0.50 micrometers, as measured from a plane of said
managed heat transfer surface.
60. The method of claim 59, wherein said roughness is about 0.20
micrometers to about 0.40 micrometers.
61. The method of claim 60, wherein said roughness is about 0.25
micrometers to about 0.30 micrometers.
Description
BACKGROUND OF THE INVENTION
[0001] Various types of molds have long been in use for preparing
optical discs from thermoplastic resins. Molds for these purposes
are typically manufactured from metal or a similar material having
high thermal conductivity. For most purposes, high thermal
conductivity is desirable since it permits the resin in the mold to
cool rapidly, shortening the molding cycle time. At times, however,
cooling is so rapid that the resin freezes instantaneously at the
mold surface upon introduction into the mold, forming a thin solid
layer which, especially if is contains a filler, can create rough
surfaces, voids, porosity and high levels or residual stress and
orientation. In an optical disc, such imperfections impede the
optical properties and decrease or eliminate the performance of the
optical disc.
[0002] Therefore, in an injection molding of compact discs, for
audio, video, or computer data storage and retrieval applications,
heat transfer through the mold has a strong effect on molding time
and disc attributes such as birefringence, flatness, and accuracy
of feature replication.
[0003] One method for affecting heat transfer and improving the
cycle time during injection molding is known as the technique of
managed heat transfer (MHT). The basic principle of managed heat
transfer is applying a passive thermal insulating layer to the mold
to control the transient heat transfer between molten resin
materials and the mold surfaces during the injection molding. The
insulating layer comprises materials having both low thermal
diffusivity and conductivity, thus slowing the cooling of the
molded resin, and good resistance to high temperature degradation,
permitting use in a mold maintained at high temperatures. For
improving mechanical strength, abrasion resistance, oxidation
resistance and thermal conductivity, at least one skin layer may be
bonded to the insulating layer.
[0004] Another method for affecting heat transfer is forming a
synthetic resin layer on a stamper by coating or lamination before
the stamper is placed on a core molding surface of a metal
mold.
[0005] The use of a heat transfer managing layer (HTM layer) such
as the thermal insulating layer and the synthetic resin layer is
desirable so as to cause a minimal change in the size and shape of
a molding tool and equipment. However, requirements of optical
clarity, surface morphology, and replication of surface features of
submicron dimensions are very stringent for optical discs.
Therefore, common insulating materials, which do not provide a
smooth enough surface, are not stable for long periods at the mold
temperature, or cannot withstand the repeated application of high
pressure during the molding process, should be avoided.
[0006] It is also difficult to apply a thick polymer coating over a
6 inch-diameter surface without defects such as particles or
bubbles getting into the film surface. Particles may be generated
during the spin coating process as excess materials are spun off
the stamper. Particles or bubbles in the coating forms "high" spots
on the surface of the heat transfer managing layer, which causes
dimples in the molded disc, potentially forming a defective track
area.
[0007] Moreover, after applying the managing heat transfer layer to
the stamper, the stampers are typically punched to a final
dimension required for mounting onto an injection molding
equipment. This punching or trimming process also shears the
polymer coating, which, if brittle, can deposit particles in the
surface of the layer. These may become statically attached to the
polymer surface, and are not easily removed. The punch process may
also leave a raised lip around the sheared perimeter, making
mounting onto the molding machine more difficult.
SUMMARY OF THE INVENTION
[0008] It is therefore desirable to provide an apparatus, stamper,
and method for manufacturing data storage media. In one embodiment,
the method for manufacturing data storage media comprises:
disposing a managed heat transfer layer in operable communication
with a second surface of a stamper, wherein a first surface of said
stamper comprises surface features, wherein an exposed surface of
said managed heat transfer layer has been altered by a method
selected from the group consisting of chemically, mechanically, or
a combination thereof; disposing the stamper in a mold with at
least a portion of said exposed surface disposed in operable
communication with a mold half; injecting a molten plastic into
said mold; cooling the plastic to form said data storage media; and
releasing said data storage media from said mold
[0009] In one embodiment, the molding apparatus for producing data
storage media comprises: a stamper comprising a managed heat
transfer layer, wherein a first surface of said stamper comprises
surface features, and wherein an exposed surface of said managed
heat transfer layer has been altered by a method selected from the
group consisting of chemically, mechanically, or a combination
thereof, and has a thickness variation of less than about 5%; and a
support for receiving the stamper by operable communication with
said managed heat transfer layer.
[0010] In one embodiment, the method for producing a stamper,
comprises: forming a nickel plated substrate having desired surface
features on one side; disposing a managed heat transfer layer on a
second side of said substrate; forming a thickness of said managed
heat transfer layer having a variation of less than about 5%; and
altering an exposed surface of said managed heat transfer layer,
wherein said altering is by a method selected from the group
consisting of chemically altering, mechanically altering, or a
combination thereof.
[0011] The above described and other features are exemplified by
the following figure and detailed description.
BRIEF DESCRIPTION OF THE DRAWING
[0012] Referring now to the figure, in which:
[0013] FIG. 1 is a sectional side view of one embodiment of an
injection mold.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] Managed heat transfer layer can be used in injection molding
and injection-compression molding processes as layers disposed on
the backside of the stamper in order to inhibit uncontrolled
cooling of the molten material. Upon contacting the stamper, the
molten material injected into the mold rapidly cools. If the rate
of cooling is not managed, the resultant article can possess
defects such as peeling, cracking, and areas of increased stress.
The employment of a managed heat transfer layer on the back-side of
the stamper (i.e., the side opposite the surface features and
molten material contact) can control the rate of heat dissipation
from the molten material, thereby improving the resultant article.
Managed heat transfer layers are discussed in commonly assigned
U.S. Pat. No. 6,146,588, which is incorporated herein by
reference.
[0015] In order to further enhance the advantages attained by the
employment of the managed heat transfer layer, various treatments
can be employed. These treatments include: processing the managed
heat transfer layer (e.g., via polishing, reactive ion etching
(RIE), surface lapping, combinations comprising at least one of
these treatments, and the like) to attain a substantially uniform
thickness and flatness; extending the life of the managed heat
transfer layer and/or the life of the stamper; chemically altering
the surface of the managed heat transfer layer and/or applying a
coating over the managed heat transfer layer, e.g., to inhibit
adhesion to the adjacent mold half; and/or alter the coefficient of
friction, at least in specified areas of the stamper to enhance
vacuum adhesion to the mold in the clamping area. Good adhesion is
desirable in the clamping area, but not in its molding area where
the stamper presses against the mirror block. In this area, low
friction is desirable to reduce the amount of abrasion the polymer
receives with each stamping cycle.
[0016] Surface imperfections on the managed heat transfer layer can
translate through the stamper to the article during the molding
process creating random imperfections on the article surface and
possibly forming a defective article (e.g., an unreadable optical
disk). Similarly, nonuniformity of the managed heat transfer layer
can cause uneven transfer of the stamper surface features to the
article, similarly causing imperfections. Consequently, the managed
heat transfer layer preferably has a substantially uniform
thickness, i.e., a thickness that varies less than about 5% across
the entire surface. More preferably, the thickness varies less than
about 3%, with a thickness variation of less than about 1% even
more preferred, and a variation of less than about 0.5% especially
preferred. For example, the managed heat transfer layer
preferablyhas a local (i.e., across a 1 centimeter square
(cm.sup.2) area) flatness (i.e., thickness variation), of less than
about 75 nanometers (nm), with less than about 50 nm more
preferred, and less than about 25 nm especially preferred.
[0017] Substantially uniform thickness can be attained by surface
lapping using a grinding machine and very fine grit paper, i.e.,
grit paper having a grit particle size of less than or equal to
about 9 micrometers. A particle size of less than or equal to about
5 micrometers is preferred, with a grit particle size of less than
or equal to about 3 micrometers is preferred.
[0018] Surface lapping, or finishing, both remove slight amounts of
material preferably starting from the "high" spots on the polymer
coating. This is controlled by the hardness of the support material
used to press the sandpaper down on the substrate. A "soft"
material would conform to the existing surface, making it more
difficult to remove microwaviness. A "hard" sandpaper backing would
be better suited to remove surface defects (high spots) and surface
microwaviness.
[0019] Similar to initially forming a substrate comprising a
substantially uniform thickness, it is also preferred to retain the
uniform thickness, free of surface defects, e.g., peeling,
particles, or orange peel, during the use of the stamper. By
removing surface defects such as peeling, which can adversely
affect the electrical performance and aesthetics of the finished
article (e.g., data storage media, and the like), the life of the
managed heat transfer layer can be extended. For example, a typical
managed heat transfer layer has a life of about 50,000 shots or
less, by removing the peeling, the life can be extended to about
100,000 shots or more, with a life of about 200,000 shots or
greater readily attainable.
[0020] Removal of the peeling can be attained by a polishing or
surface lapping process that removes about 2 micrometers (.mu.m) of
material or less, with removal of about 1 .mu.m or less preferred,
and removal of about 0.5 .mu.m or less especially preferred. Such
limited removal of material can allow re-flattening of the managed
heat transfer layer without reducing its effectiveness in managing
the heat transfer.
[0021] In addition to extending the life of the managed heat
transfer layer via removal of peeling, life extension can be
attained by reducing adhesion of a used managed heat transfer layer
to the adjacent mold half, and by improving friction and wear
properties of the managed heat transfer layer. Essentially, after a
period of employment of the managed heat transfer layer in molding
equipment, the layer can adhere to the adjacent mold half, e.g.,
the mirror block on the molding equipment, resulting in damage to
the heat transfer layer and mirror block upon removal of the
stamper and managed heat transfer layer.
[0022] Reduction of adhesion to the molding equipment, as well as
reduced friction and improved wear, can be attained by chemically
altering the surface of the managed heat transfer layer that
interfaces with the mold half. Chemically altering the surface can
comprise changing, e.g., reducing, the surface polymer(s) chain
length, and/or chemically reacting the surface polymer(s) with
another material to change the chemical composition thereof.
Chemical alteration can be accomplished via a chemical and/or
plasma process. A chemical process can comprise exposing the
surface to an aqueous caustic solution (e.g., an aqueous solution
of an alkali or alkaline earth metal hydroxide, carbonate, or a
combination comprising at least one of the foregoing solutions,
such as potassium carbonate, barium hydroxide, potassium hydroxide,
and the like) to reduce the polymer length, surface modulus, and
hardness. For example, a polyimide managed heat transfer layer can
be exposed to 2 wt % potassium hydroxide dissolved in and 80/20
mixture of ethanol and water to remove about 1 micrometer/minute
(.mu.m/min) of the polyimide coating. After etching, modulus for
the polyimide surface is about 100 kilopounds per square inch
(Kpsi) vs. 400 Kpsi for that of the bulk.
[0023] Alternatively, plasma or reactive ion etch can be employed
to change the surface properties of the managed heat transfer
layer. Parameters controlling reactive ion etching include the type
and concentration of gas(es) present during the plasma process, the
operating conditions that include temperature, pressure, power and
frequency, and the chamber materials that can comprise metal,
glass, and/or plastics such as tetrafluoroethylene fluorocarbon
polymers (e.g., Teflon). Exposure of a managed heat transfer layer
to the reactive ion etch chemistry can change its surface chemistry
to provide more desirable properties. The reactive ion etching can
be a dry etching, which breaks polymer chains and volatilizes them
resulting in slow etching of the polymer, leaving a composite
managed heat transfer layer having a surface with low weight
average molecular weight (Mw) chains present and thus lower modulus
than that found in the bulk of the layer, or it can fluorinate
areas on the polymer chain, greatly reducing frictional wear on the
surface during subsequent use in molding equipment.
[0024] Generally, a plasma reactive ion etching system employs a
gas such as oxygen (O.sub.2), chlorine (Cl.sub.2), hydrochloric
acid (HCl), fluorocarbons (e.g., Freong, CF.sub.4, CHF.sub.3, and
the like), nitrogen (N.sub.2), nitrogen oxide (N.sub.2O), argon
(Ar), boron trichloride (BCl.sub.3), hydrogen (H.sub.2), sulfur
hexafluoride (SF.sub.6), and the like, as well as ions, reaction
products, and combinations comprising at least one of the foregoing
gases. For example, oxygen can be used in a reactive ion etch
system to etch organic polymers. The plasma dissociates the oxygen
into ions that readily oxidize organic material it contacts with
into volatile compounds such as carbon dioxide, water, and nitric
oxide. In another example, a polyimide managed heat transfer layer
can be exposed to a fluorine ambient, such as trifluoromethane
(CHF.sub.3) plasma, which can be controlled to leave a fluorinated
polymer layer on the polyimide to reduce surface adhesion and
friction to the molding equipment.
[0025] Reactive ion etch systems generally consist of a vacuum
chamber containing parallel plate electrodes, the cathode being
powered by an rf generator at a frequency sufficient to form the
plasma (e.g., for most gases, typically at a frequency of about
13.56 MHz), while the second electrode, or anode, is grounded.
During etching, substrates are placed on the cathode, the chamber
is evacuated and gases are introduced and regulated at low
pressure, typically less than 1 Torr. By controlling the pressure,
power and bias voltage on the cathode, RIE systems can etch a
pattern either isotropically, that is, in all directions at and
equal rate, or anisotropically, which means it predominately etches
vertically, maintaining the original pattern width.
[0026] Alternative, or in addition, to chemically altering the
surface of the managed heat transfer layer, friction and adhesion
can be adjusted by employing a lubricant, either in the managed
heat transfer layer and/or as a coating or film on the surface of
the managed heat transfer layer, between the managed heat transfer
layer and the molding equipment. Various layers that can be
deposited with a substantially uniform thickness, will impart the
desired lubricity, and is compatible with the molding conditions
can be employed. Some possible lubricants include molybdenum
disulfide (MOS.sub.2), graphite fluoride (CF.sub.1.1)).sub.n,
silicone oils (such as polydimethylsiloxane and the like),
fluorocarbon oils (such as perfluoropolyethers (Fomblin or Krytox)
and the like), surfactants (such as FC430 commercially available
from 3M, and the like), petroleum oils, and the like, as well as
reaction products and combination comprising at least one of any of
the foregoing lubricants.
[0027] If the lubricant is applied as a layer, the layer can be
deposited by any technique capable of attaining the desired
lubricity and thickness uniformity. Some possible techniques
include spin coating, spraying, vapor deposition (e.g., chemical
vapor deposition, plasma enhanced chemical vapor deposition, and
the like), electrodeposition coating, meniscus coating, spray
coating, extrusion coating, and the like, as well as combinations
comprising at least one of these techniques. Typically, if a layer
is employed, the layer preferably has a sufficient thickness to
reduce the coefficient of friction between the layer and the
molding equipment to about 0.5 or less. For example, the layer can
have a thickness of about 1 micrometer or less, with a thickness of
about 0.5 micrometers or less preferred, and a thickness of about
0.1 micrometers or less especially preferred. If the lubricant is
combined into the managed heat transfer layer, less than or equal
to about 60 weight percent (wt %) lubricant can be employed, with
less than or equal to about 50 wt % preferred, and less than or
equal to about 40 wt % lubricant especially preferred, based upon
the total weight of the managed heat transfer layer. It is further
preferred to employ greater than or equal to about 5 wt %
lubricant, with greater than or equal to about 10 wt % lubricant
preferred, based upon the total weight of the managed heat transfer
layer.
[0028] Although random imperfections and non-uniform thickness in
the managed heat transfer layer are not desirable, it can be
advantageous to impart areas of increased friction on the surface
of the managed heat transfer layer to enhance the ability of the
molding equipment to retain the stamper in place. Preferably, the
areas of increased thickness have a sufficiently small surface
roughness (e.g., non-uniform thickness) to prevent translation of
the roughness to the article, while enhancing stamper retention in
the molding equipment. Generally, a roughness of less than or equal
to about 0.50 .mu.m is employed, with a roughness of less than or
equal to about 0.40 .mu.m preferred, and less than or equal to
about 0.30 .mu.m especially preferred, as measured from a plane of
said managed heat transfer surface. It is also preferred to employ
a roughness of greater than about 0.20 .mu.m, with a roughness of
greater than about 0.25 .mu.m more preferred. Note, such roughness
will still retain a substantially uniform thickness (e.g., a
thickness variation of less than about 5%). It is especially
preferred to increase the coefficient of friction to about 0.5 or
so, with a coefficient of friction of about 1.0 or greater more
preferred in the areas of contact with the mold, e.g., areas of
vacuum contact.
[0029] Another issue that can increase the coefficient of friction
and thus abrasion between the mirror block and the managed heat
transfer layer is static charge buildup between the layers. A
mirror block will often be coated with a hard, electrically
insulating coating such as silicon nitride or diamond. Managed heat
transfer layers can also be electrically non-conductive if made out
of unfilled or undoped plastic coatings. Slight movement between
the layers during mold operation can result in static charge
build-up between them since the charge is not able to dissipate (or
flow) through the insulator coatings to a neutral surface. This
static charge increases the coefficient of friction, accelerating
wear of both surfaces.
[0030] Coating of the managed heat transfer layer and/or mirror
block with a static dissipating material such as an alkyl
quaternary ammonium compound would allow the static charge to flow
to a neutral site reducing the coefficient of friction.
Alternatively, if the managed heat transfer coating was inherently
electrically conductive, such as a low thermal conductive metal
alloy, or a graphite filled or doped plastic material, coating with
an electrically conductive material would not be as beneficial.
Combining a lubricant with an electrically conductive compound for
coating on non-electrically conductive managed heat transfer layer
and mirror surfaces is preferred. For example, incorporating
graphite fibers into the polymer used for forming the managed heat
transfer layer would provide an electrically conductive coating.
Application of MoS.sub.2 on the surface of the graphite fiber
filled polymer will provide a lubricated, electrically conductive
managed heat transfer layer.
[0031] After prolonged use of the managed heat transfer layer in
the molding equipment, it is possible that the surface
modifications and lubricity at the surface has degraded enough such
that the stamper no longer produces good quality disks. If this
occurs, it is possible to repolish and/or surface treat the managed
heat transfer layer again using the same techniques described above
to render the stamper useful in subsequent data storage media
(e.g., CD disks and the like) production.
[0032] Referring to the FIG. 1, a sectional side view of an
injection mold 10 including a managed heat transfer layer 12 and a
pair of mold halves 14 of high thermally conductive material
forming a mold cavity 16 is illustrated. Thermally insulative is
meant to include materials having coefficients of thermal
conductivity less than that of the stamper employed in the molding
press. Generally, a nickel stamper is used which has a thermal
conductivity of about 92 watts per meter Kelvin (W/m.multidot.K).
Any material having thermal conductivity lower than that of the
nickel stamper, such as thermal conductivity of less than or equal
to about 50 W/m.multidot.K would slow down the transfer of heat
from the mold chamber to the mold press. Thermally conductive is
meant to include materials having coefficients of thermal
conductivity greater than or equal to about 100 W/m.multidot.K.
[0033] Cooling lines 18, such as copper pipes, are provided in each
mold half 14 for receiving a cooling fluid to reduce cycle time. At
least one compact disc or optical disc stamper 20 is positioned in
the mold cavity 16 as shown and secured therein in a known manner.
The stamper 20 has a grooved or pitted surface 22 carrying
information. If desired, a second stamper 23, optionally comprising
surface features on all, part, or none of its surface, can
additionally be positioned in mold cavity 16. For purposes of
example, a smooth surface of the stamper is represented by portion
19 and a grooved or pitted surface of the stamper for carrying
information is represented by portion 17. Typically, the stamper
comprises electroplated nickel, chrome, titanium, copper, silicon
however, other materials, metals, and the like, as well as alloys
composites, cermets, and combinations comprising at least one of
the foregoing materials can be employed. Meanwhile, the mold halves
typically comprise a ferrous material such as steel or the like,
although other metals and/or alloys can similarly be employed.
[0034] Each mold half 14 can have a surface 21 disposed adjacent to
the managed heat transfer layer 12 that optionally includes a
surface-finished layer (e.g., lubricant layer, polished surface,
lapped surface, and the like) 12S. The managed heat transfer layer
12 may be in the form of a single thin insulating layer or
multilayer insulated structure that can be fabricated from low
thermally conductive materials such as thermoplastic materials,
thermoset materials, plastic composites, porous metals, ceramics,
and low-conductivity metal alloys, and metal oxides, as well as
cermets, composites, reaction products, and combinations comprising
at least one of the foregoing materials. Possible metal materials
include Nichrome (60% Ni and 20% Cr), Invar (64% Fe, 36% Ni),
titanium, and the like. Possible ceramics include aluminum oxide,
silicon oxide, aluminum nitride, and silicon carbide, and the like.
Possible plastics include amorphous, crystalline, and/or
semicrystalline materials and reaction products and combinations
comprising at least one of the foregoing materials. Typical
plastics used for forming the managed heat transfer layer comprise
polyimides, polyamideimides, polyamides, polysulfone,
polyethersulfone, polytetrafluoroethylene, and polyetherketone, as
well as composites, reaction products, and combinations comprising
at least one of the foregoing materials and/or a plastic set forth
below. The plastic is typically applied in uncured form (e.g., as a
polyamic acid in the case of a polyimide or polyamideimide) and
subsequently heat cured. Preferably, the managed heat transfer
layer is flexible film such as a polyimide film manufactured under
the trademark KAPTON.
[0035] Generally, the managed heat transfer layer has a thickness
that is greater than about 0.1 mil (0.00254 millimeters (mm)), with
greater than about 0.5 mils (0.0127 mm) preferred. It is further
preferred to have a thickness of less than about 5 mils (0.127 mm),
with less than about 2 mils (0.0508 mm) more preferred.
[0036] In addition to the above materials, the managed heat
transfer layer can comprise fillers. The fillers should have a size
and geometry that does not interfere with the primary and secondary
surface features. Some possible filler include glass, aluminum
silicate (AlSiO.sub.3), barium sulfate (BaSO.sub.4), alumina
(Al.sub.2O.sub.3), silica, and the like, or a layer of filled
polyimide resin coated with a layer of non-filled polyimide resin,
as well as combinations and layers, comprising at least one of the
foregoing fillers.
[0037] During molding, molten plastic resin 44 can be injected into
the mold cavity 16 via a sprue bushing 36 and a sprue 38. Possible
plastics include amorphous, crystalline, and/or semicrystalline
materials and reaction products and combinations comprising at
least one of the foregoing materials. For example the plastic can
comprise: polyvinyl chloride, polyolefins (including, but not
limited to, linear and cyclic polyolefins and including
polyethylene, chlorinated polyethylene, polypropylene, and the
like), polyesters (including, but not limited to, polyethylene
terephthalate, polybutylene terephthalate, polycyclohexylmethylene
terephthalate, and the like), polyamides, polysulfones (including,
but not limited to, hydrogenated polysulfones, and the like),
polyimides, polyether imides, polyether sulfones, polyphenylene
sulfides, polyether ketones, polyether ether ketones, ABS resins,
polystyrenes (including, but not limited to, hydrogenated
polystyrenes, syndiotactic and atactic polystyrenes, polycyclohexyl
ethylene, styrene-co-acrylonitrile, styrene-co-maleic anhydride,
and the like), polybutadiene, polyacrylates (including, but not
limited to, polymethylmethacrylate, methyl methacrylate-polyimide
copolymers, and the like), polyacrylonitrile, polyacetals,
polycarbonates, polyphenylene ethers (including, but not limited
to, those derived from 2,6-dimethylphenol and copolymers with
2,3,6-trimethylphenol, and the like), ethylene-vinyl acetate
copolymers, polyvinyl acetate, liquid crystal polymers,
ethylene-tetrafluoroethylene copolymer, aromatic polyesters,
polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene
chloride, tetrafluoroethylene fluorocarbon polymers (e.g.,
Teflons). The plastic may also or alternatively comprise
thermosetting resins such as epoxy, phenolic, alkyds, polyester,
polyimide, polyurethane, mineral filled silicone, bis-maleimides,
cyanate esters, vinyl, and benzocyclobutene resins. Additionally,
the plastic may comprise blends, copolymers, mixtures, reaction
products and composites comprising at least one of the foregoing
thermoplastics and/or thermosets. For example, "Nylon 6" or "Nylon
12" or "Nylon 6,6" which are commercially available, can be
employed.
[0038] Various thermoplastic materials may be used such as
polyamide, for example, "Nylon 6" or "Nylon 12" or "Nylon 6,6"
which are commercially available"; and other polymers such as
polyesters, poly(butylene terephthalate) (PBT), poly(ethylene
terephthalate) (PET), and PBT with soft ether linkages formed of
polycarbonate and methylene, polyether ketones, polyetherimides,
polylactams, polypropylenes, polyethylenes, polystyrene (PS),
styrene acrylonitrile, acrylonitrile butadiene terpolymers,
polyphenylene oxide/polystyrene and polyphenylene oxide/nylon and
high impact styrenes filled or unfilled and blends thereof.
[0039] Heat from the plastic 44 is absorbed through the stamper 20.
The managed heat transfer layer preferably prevents quick cooling
of the plastic 44, regulating heat transfer. This results in a hot
plastic surface at the interface between the stamper 20 and the
plastic 44 for a short time period. The managed heat transfer layer
12 and the stamper 20 cooperate to provide the desired surface
quality to the produced article (e.g., data storage media).
EXAMPLE 1
[0040] Ni stamper (commercially available from Technicolor,
Ruckersville, Va.), for manufacture of CD-ROM, was cleaned using
propanol solvent and clean-room Texwipe cloth. Approximately 10
grams polyimide solution (Dupont, P12611) was dispensed on the
center of the stamper and it was spun at 800 revolutions per minute
(rpm) for 30 seconds to obtain a uniform coating on the stamper
backside surface. The coating was baked in an oven with ramped
temperature from 100.degree. C. to 400.degree. C. over 4 hours and
held at 400.degree. C. for 1 hour to obtain a final cured film
thickness of approximately 24 .mu.m. After curing, the front side
having information of the stamper was protected by application of
Nitto tape, then the other side was subjected to a surface
treatment by using Model P-127 High Quality Micro Sander lapping
machine (commercially available from Record Products of America,
Hamden, Conn.) with a fine paper (9 micrometer Imperial Lapping
Paper commonly available from 3M.RTM.). Preliminary surface
roughness (Ra) for the cured polyimide was 107 nanometers (nm),
after polishing it was reduced to 48 nanometers.
EXAMPLE 2
[0041] A Ni stamper having a polyimide layer was prepared as in
Example 1. With the front side having information of the stamper
protected, the other side was subjected to a surface treatment by
using an etching of 2 wt % potassium hydroxide dissolved in and
80/20 mixture of ethanol and water which will remove about 1
micrometer/minute of the polyimide coating. After etching for 1
minute, the modulus for the polyimide surface was about 100 Kpsi
vs. 400 Kpsi for that of the bulk.
EXAMPLE 3
[0042] A Ni stamper having a polyimide layer was prepared as in
Example 1. With the front side having information of the stamper
protected, the other side was subjected to plasma treatment by
using a reactive ion etching system (Anelva, Model 506 Parallel
Plate System) in which CHF.sub.3 gas at a flow rate of 200 standard
cubic centimeters (sccm) at a pressure of 500 milliTorr using an rf
frequency of 13.56 megahertz (MHz) and 300 watts (W) power. Using
these conditions, a fluorinated carbon layer was deposited on the
polyimide layer at a deposition rate of approximately 500
angstroms/minute.
EXAMPLE 4
[0043] On a Ni stamper substrate, approximately 10 grams polyimide
solution (Dupont, P12611) was dispensed in the center. The stamper
was spun at 800 rpm for 30 seconds to obtain a uniform coating on
the stamper backside surface. The coating was baked in an oven with
ramped temperature from 100.degree. C. to 400.degree. C. for over 4
hours and held at 400.degree. C. for 1 hour to obtain a final cured
film thickness of approximately 24 .mu.m. After cure, the front
information side was protected with Nitto tape and the backside
managed heat transfer polymer layer was hand polished to remove
film defects due to particles and bubbles. A 3M.RTM. hard rubber
sanding block was used with 12,000 grit Micro Mesh cushioned
abrasive sand paper commercially available from Micro-Surface
Finishing Products, Inc., Wilton, Iowa. Preliminary surface
roughness for the cured polyimide was 107 nanometers, after
polishing it was reduced to 24 nanometers.
[0044] In the above examples, particles and small bubbles that can
exist in the non-treated managed heat transfer layers were removed.
Also, dimples and flaws were removed to result in a local flatness
of less than about 50 nm. Further, when installing the stampers
prepared in the examples to a mold, injecting plastic (e.g.,
polycarbonate and the like) to the mold to form an article (e.g.,
optical discs, and various other articles requiring a smooth
surface), imperfections on the surface of the storage media was
reduced. Imperfections on the optical disk commonly consist of
dimples (caused by bubbles or particles on the managed heat
transfer layer) or microwaviness (caused by non-uniform coating of
the managed heat transfer layer) both of which can interfere with
play back of information on the disk. Surface treatments of the
managed heat transfer layer removes these imperfections and allows
much longer lifetime in the mold apparatus due to reduced abrasion
during the molding process.
[0045] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes maybe made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *