U.S. patent application number 09/886317 was filed with the patent office on 2002-03-28 for abrasive article, apparatus and process for finishing glass or glass-ceramic recording disks.
Invention is credited to Yamahara, Michihiro.
Application Number | 20020037687 09/886317 |
Document ID | / |
Family ID | 18686508 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020037687 |
Kind Code |
A1 |
Yamahara, Michihiro |
March 28, 2002 |
Abrasive article, apparatus and process for finishing glass or
glass-ceramic recording disks
Abstract
A process, multi-functional grinding wheel and apparatus for
mirror-finishing the edge of at least one of a cut unfinished glass
recording disk or a cut unfinished glass-ceramic recording disk.
The process includes (a) rough grinding the edge of the at least
one of the unfinished glass recording disk or the unfinished glass
ceramic recording disk with a diamond abrasive wheel to shape the
edge into a trapezoid cross section; (b) grinding the
trapezoid-shaped edge of the at least one of the glass recording
disk or the unfinished glass ceramic recording disk with a first
resin bonded grinding wheel which comprises abrasive grains having
an average particle size in the range from about 75 micrometers to
about 15 micrometers and has an axis of rotation and an annular
shape with an inside curved surface and an outside curved surface
extending along the axis of rotation; and (c) grinding the edge of
the trapezoid-shaped recording disk with a second resin bonded
grinding wheel which comprises abrasive grains having an average
particle size in the range from about 3 micrometers to about 0.2
micrometer and has an axis of rotation and an annular shape with an
inside curved surface and an outside curved surface extending along
the axis of rotation. The multi-functional grinding wheel comprises
the first grinding wheel coaxially attached to the second grinding
wheel.
Inventors: |
Yamahara, Michihiro;
(Atsugi-city, JP) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Family ID: |
18686508 |
Appl. No.: |
09/886317 |
Filed: |
June 21, 2001 |
Current U.S.
Class: |
451/43 ; 451/256;
451/44; 451/57; 451/66; G9B/5.299 |
Current CPC
Class: |
G11B 5/8404 20130101;
B24D 5/14 20130101; B24B 1/00 20130101; B24D 3/28 20130101; B24B
9/065 20130101 |
Class at
Publication: |
451/43 ; 451/44;
451/57; 451/66; 451/256 |
International
Class: |
B24B 001/00; B24B
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2000 |
JP |
2000-186327 |
Claims
What is claimed is:
1. A process for mirror-finishing the edge of at least one of a cut
unfinished glass recording disk or an unfinished glass or
glass-ceramic recording disk, said process comprising the steps of:
a. rough grinding the edge of the at least one of the unfinished
glass recording disk or the unfinished glass-ceramic recording disk
with a diamond abrasive wheel to shape the edge into a trapezoid
cross section; b. grinding the trapezoid-shaped edge of the at
least one of the glass recording disk or the unfinished
glass-ceramic recording disk with a first resin bonded grinding
wheel which comprises abrasive grains having an average particle
size in the range from about 53 micrometers to about 9.5
micrometers and has an axis of rotation and an annular shape with
an inside curved surface and an outside curved surface extending
along the axis of rotation; and c. after step b, grinding the edge
of the trapezoid-shaped recording disk with a second resin bonded
grinding wheel which comprises abrasive grains having an average
particle size in the range from about 2.5 micrometers to about 0.45
micrometer and has an axis of rotation and an annular shape with an
inside curved surface and an outside curved surface extending along
the axis of rotation.
2. The process of claim 1 wherein the abrasive grains of the first
resin bonded grinding wheel are graded according to one JIS#220,
JIS#240, JIS#280, JIS#320, JIS#360, JIS#500, JIS#600, JIS#700,
JIS#800, JIS#1000, or JIS#1200, and wherein the abrasive grains of
the second resin bonded grinding wheel are graded according to one
JIS#5000, JIS#6000, JIS#8000, JIS#10000, JIS#15000, or
JIS#20000.
3. The process of claim 2 wherein the first and second resin bonded
grinding wheels have a shore D hardness of not less than about
80.
4. The process of claim 2 wherein the first and second resin bonded
grinding wheels each have an axial groove having an inverted
trapezoid cross-sectional shape in at least one of the inside
curved surface or the outside curved surface.
5. The process of claim 4 wherein the groove is on the inside
curved surface.
6. The process of claim 2 wherein said first resin bonded grinding
wheel is coaxially attached to said second resin bonded grinding
wheel.
7. The process of claim 2 wherein said grinding is carried out in
the presence of a water stream.
8. The process of claim 2 wherein said grinding wheels have a
density in the range of about 1.6 to about 2.5 g/cm.sup.3.
9. The process of claim 2 wherein said abrasive material is
selected from the group consisting of SiC, Al.sub.2O.sub.3,
CeO.sub.2, and combinations thereof.
10. The process of claim 2 wherein said wheel shore D hardness is
in the range of about 85 to 95.
11. The process of claim 2 wherein said resin bonded abrasive
wheels are bonded with a polyurethane resin.
12. The process of claim 2 wherein the resin bonded grinding wheel
is rotated at a peripheral velocity in one direction in the range
of about 1000 to 3000 n/min. and the glass disk is rotated in an
opposite direction at a peripheral velocity in the range of about
20 to 500 m/min.
13. The process of claim 2 wherein said grinding is carried out
under a load between the grinding wheel and the disk edge in the
range of about 0.2 to 5 kg.
14. The process of claim 2 wherein the grinding time in each of
steps a, b and c is in the range of about 5 to 60 seconds.
15. The process of claim 2 wherein further comprising between steps
a and b, the step of: grinding the trapezoid-shaped edge of the at
least one of the glass recording disk or the unfinished
glass-ceramic recording disk with a resin bonded grinding wheel
which comprises abrasive grains having an average particle size in
the range from about 106 micrometers to about 53 micrometers and
has an axis of rotation and an annular shape with an inside curved
surface and an outside curved surface extending along the axis of
rotation.
16. The process of claim 2 wherein further comprising between steps
a and b, the step of: grinding the trapezoid-shaped edge of the at
least one of the glass recording disk or the unfinished
glass-ceramic recording disk with a resin bonded grinding wheel
which comprises abrasive grains graded according to one of JIS#120,
JIS#150, JIS#180, or JIS#220 and has an axis of rotation and an
annular shape with an inside curved surface and an outside curved
surface extending along the axis of rotation.
17. A multi-functional grinding wheel comprising at least one resin
bonded grinding wheel annular segment which has an axis of rotation
and an inside curved surface and an outside curved surface
extending along its axis of rotation and which comprises first
abrasive grains having an average particle size in the range from
about 53 micrometers to about 9.5 micrometers coaxially attached to
at least one other grinding wheel annular segment which comprises
second abrasive grains having an average particle size from about
2.5 micrometers to about 0.45 micrometer.
18. The multi-functional grinding wheel of claim 17 wherein the
first abrasive grains are graded according to one of JIS#220,
JIS#240, JIS#280, JIS#320, JIS#360, JIS#500, JIS#600, JIS#700,
JIS#800, JIS#1000, or JIS#1200, and wherein the second abrasive
grains are graded according to one of JIS#5000, JIS#6000, JIS#8000,
JIS#10000, JIS#15000, or JIS#20000.
19. The multi-functional grinding wheel of claim 18, wherein at
least one of the resin bonded grinding wheel segments has a groove
which is an inverted trapezoid in cross-sectional shape.
20. The multi-functional grinding wheel according to claim 19,
wherein said groove is the inside curved surface.
21. The multi-functional grinding wheel of claim 18 wherein said
grinding wheels have a density in the range of about 1.6 to about
2.5 g/cm.sup.3.
22. The multi-functional grinding wheel of claim 18 wherein said
abrasive material is selected from the group consisting of SiC,
Al.sub.2O.sub.3, CeO.sub.2, and combinations thereof.
23. The multi-functional grinding wheel of claim 18 wherein the and
resin bonded grinding wheel segments comprising the first and
second abrasive grains each have a shore D hardness of at least
80.
24. The multi-functional grinding wheel of claim 23 wherein the and
resin bonded grinding wheel segments comprising the first and
second abrasive grains each have a shore D hardness is in the range
of about 85 to 95.
25. The multi-functional grinding wheel of claim 18 wherein said
resin bonded abrasive wheel segments are bonded with a polyurethane
resin.
26. A multi-functional grinding wheel comprising at least one resin
bonded grinding wheel annular segment which has an axis of rotation
and an inside curved surface and an outside curved surface
extending along its axis of rotation and which comprises first
abrasive grains having an average particle size in the range from
about 106 micrometers to about 53 micrometers coaxially attached to
at least one other grinding wheel annular segment which comprises
second abrasive grains having an average particle size from about
53 micrometers to about 9.5 micrometers coaxially attached to at
least one other grinding wheel annular segment which comprises
third abrasive grains having an average particle size from about
2.5 micrometers to about 0.45 micrometer.
27. The multi-functional grinding wheel of claim 26 wherein the
first abrasive grains are graded according to one of JIS#120,
JIS#150, JIS#180, and JIS#220, wherein the second abrasive grains
are graded according to one of JIS#220, JIS#240, JIS#280, JIS#320,
JIS#360, JIS#500, JIS#600, JIS#700, JIS#800, JIS#1000, or JIS#1200,
and wherein the third abrasive grains are graded according to one
of JIS#5000, JIS#6000, JIS#8000, JIS#10000, JIS#15000, or
JIS#20000.
28. An apparatus for grinding a glass disk having a diamond ground
trapezoid-shaped pitted edge comprising: a multi-functional
grinding wheel comprising at least one resin bonded grinding wheel
annular segment which has an axis of rotation and an inside curved
surface and an outside curved surface extending along its axis of
rotation and which comprises first abrasive grains having an
average particle size in the range from about 53 micrometers to
about 9.5 micrometers coaxially attached to at least one other
grinding wheel annular segment which comprises second abrasive
grains having an average particle size from about 2.5 micrometers
to about 0.45 micrometer; a motor for rotating the multi-functional
grinding wheel about its axis of rotation in at least one
direction; a clamp for transversely holding the glass disk on a
rotatable shaft; a motor for peripherally rotating the transversely
deployed glass disk in a direction opposite to that of the grinding
wheel; and a lift mechanism for causing the glass disk to move
vertically and horizontally to sequentially contact the first and
second segments of the rotating grinding wheel under load to cause
the grinding wheel segments to remove pits from the pitted surface
of the disk edge.
29. The multi-functional grinding wheel of claim 28 wherein the
first abrasive grains are graded according to one of JIS#220,
JIS#240, JIS#280, JIS#320, JIS#360, JIS#500, JIS#600, JIS#700,
JIS#800, JIS#1000, or JIS#1200, and wherein the second abrasive
grains are graded according to one of JIS#5000, JIS#6000, JIS#8000,
JIS#10000, JIS#15000, or JIS#20000.
30. An apparatus for grinding a glass disk having a diamond ground
trapezoid-shaped pitted edge comprising: a multi-functional
grinding wheel comprising at least one resin bonded grinding wheel
annular segment which has an axis of rotation and an inside curved
surface and an outside curved surface extending along its axis of
rotation and which comprises first abrasive grains having an
average particle size in the range from about 106 micrometers to
about 53 micrometers coaxially attached to at least one other
grinding wheel annular segment which comprises second abrasive
grains having an average particle size from about 53 micrometers to
about 9.5 micrometers coaxially attached to at least one other
grinding wheel annular segment which comprises third abrasive
grains having an average particle size from about 2.5 micrometers
to about 0.45 micrometer; a motor for rotating the multi-functional
grinding wheel about its axis of rotation in at least one
direction; a clamp for transversely holding the glass disk on a
rotatable shaft; a motor for peripherally rotating the transversely
deployed glass disk in a direction opposite to that of the grinding
wheel; and a lift mechanism for causing the glass disk to move
vertically and horizontally to sequentially contact the first,
second, and third segments of the rotating grinding wheel under
load to cause the grinding wheel segments to remove pits from the
pitted surface of the disk edge.
31. The apparatus of claim 30 wherein the first abrasive grains are
graded according to one of JIS#120, JIS#150, JIS#180, and JIS#220,
wherein the second abrasive grains are graded according to one of
JIS#220, JIS#240, JIS#280, JIS#320, JIS#360, JIS#500, JIS#600,
JIS#700, JIS#800, JIS#1000, or JIS#1200, and wherein the third
abrasive grains are graded according to one of JIS#5000, JIS#6000,
JIS#8000, JIS#10000, JIS#15000, or JIS#20000.
Description
RELATED APPLICATIONS
[0001] This application claims priority from Japanese Patent
Application Number 2000-186327, filed Jun. 21, 2000.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a process and apparatus for
mirror-finishing the edge of an unfinished blank glass or
glass-ceramic recording disk and a resin bonded grinding wheel
useful in such a process.
[0004] 2. Related Art
[0005] Conventionally, disk materials have been widely used as
substrates for information recording media such as hard disks for
personal computers. In recent years, there have been
ever-increasing demands for glass or glass-ceramic plates capable
of recording information with high density, and attention has been
focused on the development of finishing processes for making glass
or glass-ceramic memory disks.
[0006] When a glass or glass-ceramic plate is processed into a disk
substrate for an information recording medium, a glass or
glass-ceramic plate is typically first punched out by a glass
cutter to form an unfinished recording disk. The edge of the
as-punched out plate is sharp and dangerous to handle. A chamfering
process for cutting the comers of the edge off and a finishing
process must thereafter be carried out.
[0007] Conventionally, the edge of the unfinished punched out disk
is ground and shaped into trapezoid cross-section by a diamond
wheel. A plurality of the unfinished disks are then superposed and
edge polished. Polishing typically employs a brush while supplying
cerium oxide slurry thereto as a polishing adjuvant to carry out
the edge polishing process.
[0008] During the initial grinding and shaping processes by use of
a diamond wheel, however, a number of unwanted pits are created on
the polished disk face which the subsequent brush polishing process
fails to completely remove. Consequently, fine particles derived
from shavings and polishing adjuvant enter the remaining pits as
foreign matter, and are often ejected during the subsequent
processes, causing contamination on the substrate surface.
Moreover, this conventional method generates a large amount of
waste water containing cerium oxide that may be a soil pollutant,
resulting in high waste- water treatment costs.
[0009] Additional details regarding known methods for grinding the
edge of an unfinished glass hard disks are reported, for example,
in Japanese Patent Kokai Publication No. 5759/1989, published Jan.
10, 1989, and Japanese Patent Application No. 212690/1998,
published on Feb. 15, 2000 as Japanese Patent Kokai Publication No.
2000-042889.
[0010] In recent years, demands for higher recording density in the
recording media, has dictated that the pits on the edge of the
substrate which cause contamination on the substrate surface be
substantially eliminated. Additional and/or improved methods for
polish the edge of glass or glass-ceramic disks is needed.
SUMMARY OF THE INVENTION
[0011] The present invention substantially solves certain of the
above-mentioned problems, and provides a process for finishing the
ground edge of at least one of an unfinished glass recording disk
or an unfinished glass-ceramic recording disk which substantially
eliminates pits on the disk edge and which is easily operated
substantially without causing any loss in the quality of the
finished recording medium.
[0012] The present invention provides a process for
mirror-finishing the edge of a cut of at least one of an unfinished
glass or a glass-ceramic recording disk. The process
comprising:
[0013] a. rough grinding the edge of the unfinished glass or the
glass-ceramic recording disk with a diamond abrasive wheel to shape
the edge into a trapezoid cross section;
[0014] b. grinding the trapezoid-shaped edge of the glass recording
disk or the glass-ceramic recording disk with a first resin bonded
grinding wheel which comprises abrasive grains having an average
particle size in the range from about 53 micrometers to about 9.5
micrometers (e.g., graded according to one of JIS#220 (which has an
average particle size of about 53 micrometers), JIS#240 (which has
an average particle size of about 57 micrometers), JIS#280 (which
has an average particle size of about 48 micrometers), JIS#320
(which has an average particle size of about 40 micrometers),
JIS#360 (which has an average particle size of about 35
micrometers), JIS#500 (which has an average particle size of about
30 micrometers), JIS#600 (which has an average particle size of
about 20 micrometers), JIS#700 (which has an average particle size
of about 17 micrometers), JIS#800 (which has an average particle
size of about 14 micrometers), JIS#1000 (which has an average
particle size of about 11.5 micrometers), or JIS#1200 (which has an
average particle size of about 9.5 micrometers)) and has an axis of
rotation and an annular shape with an inside curved surface and an
outside curved surface extending along the axis of rotation;
and
[0015] c. after step b, grinding the edge of the trapezoid-shaped
recording disk with a second resin bonded grinding wheel which
comprises abrasive grains having an average particle size in the
range from about 2.5 micrometers to about 0.45 micrometer (e.g.,
graded according to one of JIS#5000 (which has an average particle
size of about 2.5 micrometers), JIS#6000 (which has an average
particle size of about 2 micrometers), JIS#8000 (which has an
average particle size of about 1.2 micrometer), JIS#10000 (which
has an average particle size of about 0.6 micrometer), JIS#15000
(which has an average particle size of about 0.5 micrometer), or
JIS#20000 (which has an average particle size of about 0.45
micrometer) and has an axis of rotation and an annular shape with
an inside curved surface and an outside curved surface extending
along the axis of rotation. In one embodiment, the process further
comprises, between steps a and b, the step of grinding the
trapezoid-shaped edge of the at least one of the glass recording
disk or the unfinished glass-ceramic recording disk with a resin
bonded grinding wheel which comprises abrasive grains having an
average particle size of about 106 micrometers to about 53
micrometers (e.g., graded according to one of JIS#120 (which has an
average particle size of about 106 micrometers), JIS#150 (which has
an average particle size of about 75 micrometers), JIS#180 (which
has an average particle size of about 63 micrometers), or JIS#220
(which has an average particle size of about 53 micrometers)) and
has an axis of rotation and an annular shape with an inside curved
surface and an outside curved surface extending along the axis of
rotation.
[0016] In another aspect, the invention provides a multi-functional
grinding wheel comprising at least one resin bonded grinding wheel
annular segment which has an axis of rotation and an inside curved
surface and an outside curved surface extending along its axis of
rotation and which comprises abrasive grains having an average
particle size in the range from about 53 micrometers to about 9.5
micrometers (e.g., graded according to one of JIS#220 (which has an
average particle size of about 53 micrometers), JIS#240 (which has
an average particle size of about 57 micrometers), JIS#280 (which
has an average particle size of about 48 micrometers), JIS#320
(which has an average particle size of about 40 micrometers),
JIS#360(which has an average particle size of about 35
micrometers), JIS#500 (which has an average particle size of about
30 micrometers), JIS#600 (which has an average particle size of
about 20 micrometers), JIS#700 (which has an average particle size
of about 17 micrometers), JIS#800 (which has an average particle
size of about 14 micrometers), JIS#1000 (which has an average
particle size of about 11.5 micrometers), or JIS#1200 (which has an
average particle size of about 9.5 micrometers)) coaxially attached
to at least one other grinding wheel annular segment which
comprises abrasive grains having an average particle size from
about 2.5 micrometers to about 0.45 micrometer (e.g., graded
according to one of JIS#5000 (which has an average particle size of
about 2.5 micrometers), JIS#6000 (which has an average particle
size of about 2 micrometers), JIS#8 000 (which has an average
particle size of about 1.2 micrometer), JIS#10000 (which has an
average particle size of about 0.6 micrometer), JIS#15000 (which
has an average particle size of about 0.5 micrometer), or JIS#20000
(which has an average particle size of about 0.45 micrometer).
Optionally, the multi-functional grinding wheel further comprises
at least one resin bonded grinding wheel annular segment which has
an axis of rotation and an inside curved surface and an outside
curved surface extending along its axis of rotation and which
comprises abrasive grains having an average particle size in the
range from about 106 micrometers to about 53 micrometers (e.g.,
graded according to one of JIS#120 (which has an average particle
size of about 106 micrometers), JIS#150 (which has an average
particle size of about 75 micrometers), JIS#180 (which has an
average particle size of about 63 micrometers), or JIS#220 (which
has an average particle size of about 53 micrometers)) coaxially
attached to at least one other grinding wheel annular segment.
[0017] In a further aspect, the invention provides an apparatus for
grinding a glass or glass-ceramic disk having a diamond-ground
trapezoid-shaped pitted edge comprising:
[0018] a multi-functional grinding wheel comprising at least one
resin bonded grinding wheel annular segment which has an axis of
rotation and an inside curved surface and an outside curved surface
extending along its axis of rotation and which comprises abrasive
grains having an average particle size in the range from about 53
micrometers to about 9.5 micrometers (e.g., graded according to one
of JIS#220 (which has an average particle size of about 53
micrometers), JIS#240 (which has an average particle size of about
57 micrometers), JIS#280 (which has an average particle size of
about 48 micrometers), JIS#320 (which has an average particle size
of about 40 micrometers), JIS#360 (which has an average particle
size of about 35 micrometers), JIS#500 (which has an average
particle size of about 30 micrometers), JIS#600 (which has an
average particle size of about 20 micrometers), JIS#700 (which has
an average particle size of about 17 micrometers), JIS#800 (which
has an average particle size of about 14 micrometers), JIS#1000
(which has an average particle size of about 11.5 micrometers), or
JIS#1200 (which has an average particle size of about 9.5
micrometers)) coaxially attached to at least one other grinding
wheel annular segment which comprises abrasive grains having an
average particle size from about 2.5 micrometers to about 0.45
micrometer (e.g., graded according to one of JIS#5000 (which has an
average particle size of about 2.5 micrometers), JIS#6000 (which
has an average particle size of about 2 micrometers), JIS#8000
(which has an average particle size of about 1.2 micrometer),
JIS#10000 (which has an average particle size of about 0.6
micrometer), JIS#15000 (which has an average particle size of about
0.5 micrometer), or JIS#20000 (which has an average particle size
of about 0.45 micrometer);
[0019] a motor for rotating the multi-functional grinding wheel
about its axis of rotation in at least one direction;
[0020] a clamp for transversely holding the glass or glass-ceramic
disk on a rotatable shaft;
[0021] a motor for peripherally rotating the transversely deployed
glass or glass-ceramic disk in a direction opposite to that of the
grinding wheel; and
[0022] a lift mechanism for causing the glass or glass-ceramic disk
to move vertically and horizontally to sequentially contact the
first and second segments of the rotating grinding wheel under load
to cause the grinding wheel segments to remove pits from the pitted
surface of the disk edge. Optionally, the multi-functional grinding
wheel further comprises at least one resin bonded grinding wheel
annular segment which has an axis of rotation and an inside curved
surface and an outside curved surface extending along its axis of
rotation and which comprises first abrasive grains having an
average particle size in the range from about 106 micrometers to
about 53 micrometers (e.g., graded according to one of JIS#120
(which has an average particle size of about 106 micrometers),
JIS#150 (which has an average particle size of about 75
micrometers), JIS#l 80 (which has an average particle size of about
63 micrometers), or JIS#220 (which has an average particle size of
about 53 micrometers)) coaxially attached to at least one other
grinding wheel annular segment, and the lift mechanism can move
vertically and horizontally to sequentially contact the segments of
the rotating grinding wheel under load to cause the grinding wheel
segments to remove pits from the pitted surface of the disk
edge.
[0023] In the present invention, the recording medium disk refers a
disk material used as a hard disk substrate for information
recording on and from which electronic information may be written
and read, such as a hard-disk glass or glass-ceramic substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic outline cross-sectional view that
shows the shape of the edge of a glass recording disk that has been
ground and shaped to a trapezoid shape by using a diamond
wheel.
[0025] FIG. 2 is a schematic outline cross-sectional view that
shows the shape of a groove that is formed on the outside surface
or the inside surface of a grinding wheel used in the present
invention.
[0026] FIG. 3 is a perspective view that shows one example of a
multi-functional wheel used in the present invention.
[0027] FIGS. 4(a)-(c) are various schematic outline cross-sectional
views that show a dressing process carried out on a grinding wheel
used in the present invention.
[0028] FIG. 5 is a cross-sectional view that shows one example of
the multi-functional grinding wheel to be used in the process
according to the present invention.
[0029] FIG. 6 is a perspective view that shows one example of a
grinding apparatus for conducting the process according to the
present invention.
Detailed Description
[0030] FIG. 1 shows a schematic outline cross-sectional view of the
shape of an edge of a recording disk 10 that has been ground and
shaped by a diamond wheel into a trapezoidal cross-section. The
thickness of the glass (or glass-ceramic) plate from which the disk
is cut is typically about 0.4 to about 1.4 mm, more preferably, 0.6
to 0.8 mm. In the case when the thickness of the disk plate is 0.6
mm, the upper side "a" of the trapezoid has a length of
approximately 300 micrometers, and the angle of inclination
(.theta.) on both of the sides is approximately 45.degree..
[0031] Upon grinding and shaping a fragile material such as glass
or glass-ceramic by using a diamond wheel, pits are usually formed
all through the ground surface. Therefore, on the edge of ground
and shaped disk 10, there are typically pits usually having a
diameter of 20 to 50 micrometers all through the ground
surface.
[0032] In the present invention, pits are eliminated by
mirror-finishing the edge of the unfinished disk that has been
ground and shaped into a trapezoid shape. A process according to
the invention includes at least two grinding operations after the
diamond shaping operation. A grinding process according to the
present invention preferably uses a supply of water to prevent
scattering of ground glass or glass-ceramic powder generated during
the grinding process. It is not necessary to provide a grinding aid
such as a slurry of cerium oxide powder. Therefore, no waste water
containing cerium oxide as a soil pollutant is generated during the
grinding process, thereby making it possible to reduce cleanup
costs.
[0033] In the first grinding operation, the grinding is carried by
using a resin bonded grinding wheel (hereinafter, referred to as
"first grinding wheel") having an average particle size in the
range from about 53 micrometers to about 9.5 micrometers,
preferably, about 40 micrometers to about 14 micrometers, more
preferably, about 30 micrometers to about 20 micrometers. In terms
of abrasive grain graded according to Japanese Industrial Standards
("JIS") in the range of JIS#220 to JIS#1200, preferably JIS#320 to
JIS#800, and more preferable, JIS#400 to JIS#600. Currently JIS#220
to JIS#8000 is graded according to JIS R 6001 (1998 Edition) and
JIS R 6002 (1998 Edition), the disclosures of which are
incorporated herein by reference, wherein for JIS#220, the
particles are graded with sieves, and the particle size is the mesh
size of the sieve on which not less than 40% of the particles
remain at the third stage; and wherein for JIS#240 to JIS#8000,
grading is via electrical resistance, and the particle size is 50%
point of cumulative height of the electrical resistance values
measured; and for JIS#10000 and JIS#15000, grading is via
sedimentation, and the particle size is the diameter at 50% point
of cumulative sedimentation heights. For JIS#20000, grading is via
laser light diffraction method using laser light diffraction laser
light diffraction particle size analysis meter system obtained from
Nikkiso K.K., Japan under the trade designation "MICRO TRAC",
wherein the particle size is the particle diameter at 50% point of
cumulative laser beam intensity heights.
[0034] Particle sizes greater than about JIS#220 sometimes results
in new unwanted pits on the edge of the glass plate during the
grinding process. Particle sizes finer than about JIS#1200 requires
unreasonably long process times for eliminating the pits.
[0035] Any conventional glass polishing abrasive grains may be used
as the abrasive material, for example, fused aluminum oxide
(including white fused alumina, heat-treated aluminum oxide and
brown aluminum oxide), ceria, silicon carbide, boron carbide,
titanium carbide, diamond, cubic boron nitride, garnet, fused
alumina-zirconia, and sol-gel-derived abrasive particles, and the
like. The sol-gel-derived abrasive particles may be seeded or
non-seeded. Examples of sol gel abrasive particles include those
described U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat.
No. 4,518,397 (Leitheiser et al.), 4,623,364 (Cottringer et al.),
U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe
et al.), U.S. Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No.
5,011,508 (Wald et al.), U.S. Pat. No. 5,090,968 (Pellow), U.S.
Pat. No. 5,139,978 (Wood), U.S. Pat. No. 5,201,916 (Berg et al.),
U.S. Pat. No. 5,227,104 (Bauer), U.S. Pat. No. 5,366,523
(Rowenhorst et al.), U.S. Pat. No. 5,429,647 (Larmie), U.S. Pat.
No. 5,498,269 (Larmie), and U.S. Pat. No. 5,551,963 (Larmie), the
disclosures of which are incorporated herein by reference.
[0036] The first grinding wheel preferably has a shore D hardness
of at least about 80; more preferably, the shore D hardness is in
the range of about 85 to 95. A shore hardness D less than about 80
may result in the grinding face being too abrasive, resulting in a
short service life of the grinding wheel. At a shore hardness D
exceeding about 95 the wheel may form unwanted large pits on the
edge of the glass or glass-ceramic plate during the grinding
process.
[0037] The density of the first grinding wheel is preferably in the
range of about 1.6 to about 2.5 g/cm.sup.3. At a density less than
about 1.6 g/cm.sup.3, the grinding face may result in its being too
abrasive, resulting in a short service life of the grinding wheel.
At a density exceeding about 2.5 g/cm.sup.3, the wheel may form
unwanted large size pits on the edge of the glass or glass-ceramic
plate during the grinding process.
[0038] The wheel bonding agent may be any suitable bonding material
that will produce a grinding wheel having the above physical
properties. A suitable bonding material is a polyurethane resin. A
preferred polyurethane is disclosed in Japanese Patent Kokai
Publication No. 294336/1990, published Dec. 5, 1990, and U.S. Pat.
No. 4,933,373 (Moren et al.), the disclosures of which are
incorporated herein by reference. This reference discloses
cross-linked polyurethane which has a glass transition temperature
of approximately 10.degree. C. and a glass transition temperature
range of approximately higher than 70.degree. C.
[0039] The first grinding wheel is preferably manufactured by using
a method disclosed in Japanese Patent Kokai Publication No.
294336/1990, published Dec. 5, 1990, and U.S. Pat. No. 4,933,373
(Moren et al.), the disclosures of which are incorporated herein by
reference. Such grinding wheels are generally known as a foamed
elastic grinding material, and examples thereof include that sold
under the trade designation "DLO WHEEL" by Sumitomo 3M K.K.,
Japan.
[0040] The first grinding wheel may be provided with a groove that
corresponds to the shape of the desired trapezoidal edge shape of
the diamond ground disk. The groove may be located on the outside
surface or the inside surface of the wheel. That is, the groove
would have an inverted trapezoidal shape and would be deployed in a
direction transverse to the axis of rotation. FIG. 2 is a schematic
outline cross-sectional view that shows the shape of the groove
formed on the outside surface or the inside surface of the grinding
wheel used in the process according to the present invention. In
this case, the upper face and right and left slanting faces of the
edge of the disk are simultaneously ground by using a single
grinding wheel. One groove or a plurality of grooves may be formed.
The edges of a plurality of disks may be simultaneously ground by
using a grinding wheel with a plurality of grooves.
[0041] The grinding wheel is preferably formed into an annular
shape with an inner curved surface and an outer curved surface, as
shown in FIG. 3. The inner curved surface portion of the wheel is
preferably used to finish the edge of the unfinished disk.
[0042] In the grinding process, the grinding wheel and disk are
preferably respectively rotated in opposite directions and a load
is applied to the disk edge so as to allow the wheel to come into
contact with the edge of the disk. The grinding conditions are
properly adjusted depending on the level of the finishing required.
In general, the conditions are set as follows: The peripheral
velocity of the grinding wheel is set in the range of approximately
1000 to 3000 m/min., the peripheral velocity of the disk is set in
the opposite direction in the range of 20 to 500 m/min., the load
is set in the range of approximately 0.2 to 5 kg, and the grinding
time is in the range of 5 to 60 seconds, more preferably, 10 to 30
seconds.
[0043] The second grinding process is carried out by using a resin
bonded grinding wheel (hereinafter, referred to as the "second
grinding wheel") containing abrasive grains having an average
particle size in the range from about 2.5 micrometers to about 0.45
micrometer, preferably, about 2 micrometers to about 0.5
micrometer, more preferably, about 1.2 micrometer to about 0.6
micrometer. In terms of abrasive grain graded according to Japanese
Industrial Standards ("JIS") in the range of JIS#5000 to JIS#20000,
preferably JIS#6000 to JIS#15000, and more preferably, JIS#8000 to
JIS#10000. Such grinding wheels are generally known as a foamed
elastic grinding material, and examples thereof include that sold
under the trade designation "DLO WHEEL" by Sumitomo 3M K.K.,
Japan.
[0044] Abrasive grains having particle sizes larger than JIS#5000
tend to cause insufficient pit removal. The abrasive grains having
particle sizes finer than JIS#20000 tend to be insufficient to
polish at an economical rate, thus taking too long a time in
eliminating pits. The density of the second grinding wheel is
preferably in the range of about 1.6 to about 2.5 g/cm.sup.3. At a
density less than about 1.6 g/cm.sup.3, the grinding face may
become too abrasive, and may result in a short service life of the
grinding wheel. At a density exceeding about 2.5 g/cm.sup.3, pits
may be created on the edge of the glass or glass- ceramic disk
during the grinding process.
[0045] Except for the different particle size of the abrasive
grains as described above, the second grinding wheel can have the
same structure as the first grinding wheel. Therefore, the second
grinding wheel may be manufactured in the same manner as the first
grinding wheel.
[0046] The grinding process of a disk with the second grinding
wheel is the same as that of the first grinding wheel. The grinding
conditions may be properly adjusted depending on the level of the
finishing required. In general, the conditions are set as follows:
The peripheral velocity of the grinding wheel is set in the range
of approximately 100 to 3000 m/min., the peripheral velocity of the
disk is preferably in the range of 20 to 500 m/min., the load is
preferably in the range of approximately 0.2 to 5 kg, and the
grinding time is preferably in the range of 5 to 60 seconds, more
preferably, 10 to 30 seconds.
[0047] The trapezoid-shaped edge of an unfinished glass or
glass-ceramic disk may also be mirror-finished by carrying out
three grinding processes. In this case, in the first grinding
process, grinding is carried out by using a resin bonded grinding
wheel containing abrasive grains having a particle size of JIS#120,
JIS#150, JIS#180, or JIS#220 (about 106 micrometers to about 53
micrometers), in the second grinding process, grinding is carried
out by using a resin bonded grinding wheel containing abrasive
grains having an average particle size in the range from about 53
micrometers to about 9.5 micrometers (e.g., graded to one of
JIS#220 (which has an average particle size of about 53
micrometers), JIS#240 (which has an average particle size of about
57 micrometers), JIS#280 (which has an average particle size of
about 48 micrometers), JIS#320 (which has an average particle size
of about 40 micrometers), JIS#360 (which has an average particle
size of about 35 micrometers), JIS#500 (which has an average
particle size of about 30 micrometers), JIS#600 (which has an
average particle size of about 20 micrometers), JIS#700 (which has
an average particle size of about 17 micrometers), JIS#800 (which
has an average particle size of about 14 micrometers), or JIS#1000
(which has an average particle size of about 11.5 micrometers),
more preferably, about 30 micrometers to about 20 micrometers
(e.g., graded a JIS grade selected from the group consisting of
JIS#400 (which has an average particle size of about 30
micrometers), of JIS#500 (which has an average particle size of
about 25 micrometers) JIS#600 (which has an average particle size
of about 20 micrometers), and in the third grinding process,
grinding is carried out by using a third resin bonded grinding
wheel containing abrasive grains having an average particle size
from about 11.5 micrometers to about 0.45 micrometer (e.g., graded
to one of JIS#1000 (which has an average particle size of about
11.5 micrometers), JIS#1200 (which has an average particle size of
about 9.5 micrometers), JIS#1500 (which has an average particle
size of about 8 micrometers), JIS#2000 (which has an average
particle size of about 6.7 micrometers), JIS#2500 (which has an
average particle size of about 5.5 micrometers), JIS#3000 (which
has an average particle size of about 4 micrometers), JIS#4000
(which has an average particle size of about 3 micrometers),
JIS#6000 (which has an average particle size of about 2
micrometers), JIS#8000 (which has an average particle size of about
1.2 micrometer), JIS#10000 (which has an average particle size of
about 0.6 micrometer), JIS#15000 (which has an average particle
size of about 0.5 micrometer), or JIS#20000 (which has an average
particle size of about 0.45 micrometer)), more preferably, about
1.2 micrometer to about 0.6 micrometer (e.g., graded to one of
JIS#8000 or JIS#10000).
[0048] The grinding wheels used in the grinding processes on the
present invention may be used as an independent device in each of
the grinding processes. Preferably, the first grinding wheel and
the second grinding wheel are joined to form a multi-functional
grinding wheel, and this may be used in the respective grinding
processes.
[0049] FIG. 3 shows a perspective view of one example of an
annular-shaped multi-functional grinding wheel 30 to be used in the
process according to the present invention. In FIG. 3, a first
grinding wheel segment 31 and a second grinding wheel segment 32
are laminated and joined to each other coaxially. In this case,
shifting is made from the first grinding process to the second
process by only moving the disk in the axial direction; therefore,
it is possible to eliminate time consuming tasks to exchange the
wheels when shifting is made from the first grinding process to the
second grinding process, consequently simplifying the grinding
processes.
[0050] Moreover, the coaxially laminated and joined structure
preliminarily makes it possible to minimize the grinding face of
the first grinding wheel and the second grinding wheel, and
consequently to uniformly finish the edge of the glass or
glass-ceramic disk substrate.
[0051] In general, an attaching or detaching process of a
mono-functional grinding wheel may cause an error in the mounting
position. For this reason, each time the grinding wheel is attached
or detached in a grinding process for the edge of a disk, offsets
may occur in the circularity and concentricity of the disk,
resulting in deviations in the dimensional precision and quality in
the recording medium substrate. However, in the case when the
multi-functional grinding wheel according to the present invention
is used, neither the attaching nor the detaching operation of a
wheel is required upon shifting from the first grinding process to
the second grinding process and thus no deviation occurs in the
quality of the finished recording medium substrate.
[0052] The method for bonding one abrasive wheel segment to another
segment may easily be accomplished, for example, with double sided
adhesive tape, a bonding agent, or with bolts.
[0053] In FIG. 3 the width 11 of the first grinding wheel segment
and the width 12 of the second grinding wheel segment are not
necessarily the same, and may be appropriately changed. In the case
when one of them is more abrasive, it is preferable to increase the
thickness of the more abrasive one.
[0054] Thus, the service lives of the two wheels can be made
coincident with each other when the two wheels are used in the same
grinding process. More preferably, the widths of the respective
grinding wheel segments are proportional to the degree abrasiveness
of the wheel segments.
[0055] The multi-functional grinding wheel may be provided with a
groove that corresponds in shape to the trapezoid edge shape of the
unfinished glass or glass-ceramic disk. That is, the groove has an
inverted trapezoidal shape, transverse to the shaft, as shown in
FIG. 5. One groove or a plurality of grooves may be formed. In the
case when there is a difference in the abrasive property of the
respective grinding wheel segments constituting a multi-functional
grinding wheel, it is preferable to increase the number of grooves
in the more abrasive grinding wheel segment in the same manner as
the width of the grinding wheel.
[0056] In the case when a plurality of unfinished glass or
glass-ceramic plate edges are simultaneously ground, the gap
between the grooves is preferably constantly spaced all over the
entire length of the multi-functional grinding wheel. In this case,
the respective grinding wheel segments constituting the
multi-functional grinding wheel would have a number of grooves in
proportion to the respective length of each segment.
[0057] A structure in which a plurality of the first grinding wheel
segments are coaxially laminated and a structure in which a
plurality of the second grinding wheel segments are coaxially
laminated may be further laminated and combined coaxially to form
another multi-functional grinding wheel. Moreover, in order to deal
with the grinding operation consisting of the three processes,
three different types of grinding wheel segments may be laminated
and combined coaxially to form a multi-functional wheel.
[0058] FIG. 5 is a cross-sectional view that shows one example of
the multi-functional grinding wheel 50 which may be used in the
process according to the present invention formed by joining 3
different grinding wheel segments 51, 52 and 53, respectively. The
combined grinding wheel 50 is annular in shape, and is intended to
grind the trapezoidal edge of a glass or glass-ceramic plate by
using the inside surface of the grinding wheel as grinding surface.
Grinding wheel 50 is rotated about axis of rotation 55 in use.
[0059] In this grinding wheel, a first grinding wheel segment 51, a
second grinding wheel segment 52, and a third grinding wheel
segment 53 are laminated and joined to each other coaxially. The
trapezoidal edge of a glass or glass-ceramic plate makes contact
with the grinding surface on the inside surface of the grinding
wheel to provide grinding efficiency. The grinding wheel is
provided with plurality of internal radial grooves 54, each of
which corresponds in shape to the trapezoidal edge of the glass or
glass-ceramic plate to be finished.
[0060] FIG. 6 is a perspective view that shows one example of a
grinding apparatus for conducting the process according to the
present invention, by using the above described multi-functional
grinding wheel 50. The grinding apparatus has a rotatable annular
grinding wheel 50 which includes internal grooves 54, the
circumferencial trapezoidal edge 61 of a glass plate 60 is pressed
into a grinding groove 54 provided on the inside surface of the
grinding wheel 50, and the trapezoidal edge of the glass plate 60
is ground to remove pits.
[0061] Grinding wheel 50 is made with a radial curvature which is
larger than that of the glass plate 60, and the grinding wheel 50
is able to contain the trapezoidal edge of the glass plate 60.
Plural grooves 54 correspond in shape to the trapezoidal edge of
the glass plate 60 and extend in a circle along the inner surface
of annular grinding wheel 50. Grinding wheel 50 is rotatably
supported by mechanism 62 which is rotated by a suitable motor
63.
[0062] Trapezoidal edge-shaped plate 60 is supported for rotation
on suction plate 64 which holds under vacuum plate 60. A motor 65
supported in a suitable frame 66 is provided for rotating glass
plate 60. A lift mechanism (not shown) is provided for moving glass
plate 60 vertically or horizontally. Glass plate 60 is introduced
into inside of annular grinding wheel 50, and its circumferencial
edge 61 is pressed into grinding groove 54 while the glass plate
and the grinding wheel are rotated in opposite directions.
[0063] When the edge of the glass (or glass-ceramic) disk is ground
according to the above-described grinding apparatus, the
circumference of the glass (or glass-ceramic) disk is in contact
with the grinding groove for a longer period of time than by use of
the exterior surface of a flat grinding wheel.
[0064] In general, a grinding wheel needs to be subjected to a
dressing process to recover its grinding strength and shape after a
predetermined service time. For example, in the case of a grinding
wheel having a groove in its peripheral portion with a shape
corresponding to the shape of an object to be ground, the dressing
process is generally carried out as follows: First, a grinding
wheel is removed from the driving shaft of a grinding device, and
this is attached to a driving device. Next, a dresser is pressed
onto the inside surface of the grinding wheel to grind it to a flat
face. Thereafter, another dresser having the same shape as the
object to be ground is pressed onto the inside surface of the
grinding wheel to form a groove corresponding to the shape of the
object to be ground.
[0065] The grinding wheel according to the present invention which
has an internal groove corresponding to the shape of the edge of an
unfinished trapezoidal edge disk is dressed more easily than with
conventional dressing processes.
[0066] FIG. 4 shows a cross-sectional outline view that shows the
method for carrying out the dressing process on a grinding wheel
used in the process according to the present invention. FIG. 4(a)
shows a cross-sectional outline shape of the peripheral face of a
grinding wheel at the initial stage of a grinding process. Here, an
unfinished trapezoidal edge disk 40 is ground by a groove 41 having
an inverted trapezoidal shape.
[0067] FIG. 4(b) shows a cross-sectional shape of the peripheral
face of the grinding wheel that has been used for a predetermined
time. The groove 42 becomes deeper due to abrasion, and a
protrusion 43 between grooves is formed. Since the protrusion 43
between grooves wears down surface 44 of the disk 40, it is
necessary to remove protrusion 43 through a dressing process.
[0068] FIG. 4(c) schematically shows a dressing method which
features a dresser 45, which has the same outer diameter and the
same edge shape as a trapezoidal edged disk 40 and also has a
thickness "m" that is not less than the groove pitch "n" of the
grinding wheel.
[0069] The application of the dresser having the above-mentioned
specific dimensions makes it possible to carry out a dressing
process on the grinding wheel without the need for preliminarily
carrying out a grinding process so as to make the grinding face of
the grinding wheel flat.
[0070] In dressing the grinding wheel depicted in FIG. 6, it is not
necessary to remove the grinding wheel from the driving shaft of
the grinding device; thus, the operation is simplified. Moreover,
since the outer diameter of the dresser is the same as that of the
unfinished trapezoidal edge disk, the dressing operation is carried
out in the same manner as the grinding operation except that the
disk is replaced by a dresser. Therefore, it is possible to reduce
equipment costs and also to simplify the operation.
EXAMPLES
[0071] The invention is further illustrated by the following
examples wherein all parts and percentages are by weight unless
otherwise noted.
Example 1
[0072] A glass disk, 2 mm in thickness, 63.5 mm in diameter and 20
mm in hole diameter, was prepared as an unfinished recording disk
plate. The edge of this disk plate was ground and shaped into a
trapezoid shape as illustrated in FIG. 1 by using a JIS#500
(average particle size of about 25 micrometers) diamond grinding
wheel having a diameter of 63.5 mm and a hole diameter of 20 mm,
the wheel being available under the trade designation "MED 500"
from Mitsubishi Material K.K., Japan. The length of the upper side
"a" of the trapezoid was approximately 400 micrometers, and the
angle of inclination (.theta.) on both of the ends was
approximately 45.degree.. Pits were formed on the upper face of the
edge of the glass disk being finished and the right and left
slanting faces.
[0073] The abrasive wheels included a first abrasive wheel, a
JIS#600 (average particle size of about 20 micrometers) alumina
grinding wheel having a diameter 160 mm, a density 1.8 g/cm.sup.3,
a shore D hardness 90 available under the trade designation "DLO
WHEEL" from Sumitomo 3M K.K., Japan and a second abrasive wheel, a
JIS#10000 (average particle size of about 0.6 micrometer) cerium
oxide grinding wheel having a diameter 160 mm, a density 2.0
g/cm.sup.3, a shore D hardness 95 available under the trade
designation "DLO WHEEL" from Sumitomo 3M K.K., Japan. A groove
having a shape corresponding to the shape of the edge of the glass
disk was formed on each of the grinding wheels by using a
dresser.
[0074] First, the edge of the glass disk being finished was ground
by using the JIS#600 (average particle size of about 20
micrometers) alumina grinding wheel. The following grinding method
was used. The JIS#600 (average particle size of about 20
micrometers) alumina grinding wheel and the edge ground disk plate
were respectively rotated in opposite directions, and a load was
applied so as to allow them to contact each other. The grinding
conditions were: a peripheral velocity of 2000 n/min of the
grinding wheel, a peripheral velocity of 46 R.P.M. of the glass
disk being finished, a load of 2 to 5 kg, and a grinding time of 10
seconds.
[0075] Next, the JIS#600 (average particle size of about 20
micrometers) alumina grinding wheel was replaced by the JIS#10000
(average particle size of about 0.6 micrometer) cerium oxide
grinding wheel, and the same method was carried out to grind the
edge of the glass disk being finished. The grinding conditions
were: a peripheral velocity of 2000 m/min. of the grinding wheel, a
peripheral velocity of 46 R.P.M. of the partially finished disk
plate, under a load of 2 to 5 kg, and for a grinding time of 10
seconds.
[0076] After the grinding process, the ground face was visually
observed under a laser microscope, and a pit removing rate was
calculated. An outline measuring device (made by "Mitsuotoyo" K.K.)
was used to measure the curvature of the angle of the end face.
Table 1 (below) shows the results of the tests.
[0077] In the present example, upon making a shift from the first
grinding process to the second grinding process, the grinding
wheels were exchanged on the grinding device which caused an error
in the mounting position of the grinding wheel, and the peripheral
face "a" of the disk plate (see FIG. 1) was not made completely
flat.
Example 2
[0078] The edge of the unfinished recording disk plate of the type
described in Example 1 was ground and shaped into a trapezoid shape
in the same manner as Example 1.
[0079] The abrasive wheel segments included a JIS#600 (average
particle size of about 20 micrometers) aluminum oxide grinding
wheel ("DLO WHEEL" made by Sumitomo 3M K.K., diameter 160 mm,
density 1.8 g/cm.sup.3, shore D hardness 90) and a JIS#10000
(average particle size of about 0.6 micrometer) cerium oxide
grinding wheel ("DLO WHEEL" made by Sumitomo 3M K.K., diameter 160
mm, density 2.0 g/cm.sup.3, shore D hardness 95). These two
segments were bonded to each other with their axes being coincident
with a bonding agent ("SCOTCH-WELD DP-420" made by Sumitomo 3M
K.K.). A groove having a shape corresponding to the shape of the
trapezoidal edge of the unfinished disk plate was formed on the
inner annular surface of each of the grinding wheel segment by
using a dresser.
[0080] First, the JIS#600 (average particle size of about 20
micrometers) aluminum oxide grinding wheel segment was used to
grind the edge of the disk. In the grinding process, the grinding
wheel and the glass disk plate were rotated in opposite directions,
and a load was applied to allow contact between the disk edge and
the groove. The grinding conditions were: a peripheral velocity of
2000 m/min. of the grinding wheel, a peripheral velocity of 46
R.P.M. of the disk plate, under a load of 2 to 5 kg, and for a
grinding time of 10 seconds.
[0081] Next, the partially finished glass disk plate was axially
shifted, and the JIS#10000 (average particle size of about 0.6
micrometer) cerium oxide grinding wheel segment was used to grind
the edge of the partially finished glass disk plate. The grinding
conditions were: a peripheral velocity of 2000 m/min. of the wheel,
a load of 2 to 5 kg, a peripheral velocity of 46 R.P.M. of the
glass disk plate, and a grinding time of 20 seconds.
[0082] The pit removing rate of the ground face and the curvature
of the angle of the end face were calculated in the same manner as
Example 1. The results are shown in Table 1 (below).
[0083] In this Example, since no exchanging process of grinding
wheels was made upon making a shift from the first grinding process
to the second grinding process, no error occurred in the mounting
position of the grinding wheel; therefore, the disk peripheral face
shown as "a" in FIG. 1 was made completely flat.
Comparative Example A
[0084] The edge of the same type of recording glass disk plate as
used in Example 1 was ground and shaped into a trapezoid shape in
the same manner as Example 1. A plurality of these discs was
superposed and fixed to a rotary shaft.
[0085] The edge of the disk plate was ground with grinding brush.
The grinding method was as follows: The grinding brush and the
unfinished disk plate were rotated in opposite directions, and
while supplying a water slurry containing 10 to 20 weight % of
cerium oxide as a grinding aid at a rate of 10 liter/min, and then
the edge of the unfinished glass disk plate and the brush were
allowed to contact each other. The grinding conditions were: a
peripheral velocity of 1000 m/min. of the grinding brush, a
peripheral velocity of 46 R.P.M. of the glass disk plate and
periods of grinding time of 60 seconds and 3600 seconds.
[0086] The pit removing rate of the ground face and the curvature
of the angle of the end face were calculated in the same manner as
Example 1. The results are shown in Table 1 (below).
[0087] In the conventional brush grinding method, since a plurality
of the unfinished glass disk plates were superposed, the brush was
not sufficiently applied to portions at which the disks are
adjacent to each other, resulting in an insufficient pit removing
rate. In contrast, at the tip of the edge of the unfinished glass
disk plate, since abrasion by the brush developed rapidly, the
curvature of the edge became too great after the grinding
process.
Comparative Example B
[0088] Comparative Example B was Example 1 in the specification of
Japanese Patent Application No. 212690/1998, published Feb. 15,
2000, as Japanese Patent Kokai Publication No. 2000-042889, the
disclosure of which is incorporated herein by reference.
[0089] The edge of an unfinished recording disk plate of the type
described in Example 1 was ground and shaped into a trapezoid shape
in the same manner as Example 1.
[0090] A JIS#220 (average particle size of about 53 micrometers)
aluminum oxide grinding wheel ("DLO WHEEL" made by Sumitomo 3M
K.K., diameter 160 mm, density 1.0 g/cm.sup.3, shore D hardness 35)
was prepared. A groove having a shape corresponding to the shape of
the edge of the unfinished disk plate was formed on this grinding
wheel by using a dresser.
[0091] The edge of the unfinished disk plate was ground by using
this grinding wheel. The following grinding method was used. The
grinding wheel and the disk were rotated in opposite directions,
and a load was applied so as to allow them to contact each other.
The grinding conditions were: a peripheral velocity of 2000 m/min.
of the grinding wheel, a peripheral velocity of 46 R.P.M. of the
disk, a load of 2 to 5 kg, and a grinding time of 10 seconds.
[0092] The pit removing rate of the ground face and the curvature
of the angle of the end face were calculated in the same manner as
Example 1. The results are shown in Table 1 (below).
Comparative Example C
[0093] Comparative Example C was Example 2 in the specification of
Japanese Patent Application No. 212690/1998, published Feb. 15,
2000, as Japanese Patent Kokai Publication No. 2000-042889, the
disclosure of which is incorporated herein by reference.
[0094] The edge of the same type of unfinished glass recording disk
plate used in Example 1 was ground and shaped into a trapezoid
shape in the same manner as Example 1.
[0095] Three JIS#220 (average particle size of about 53
micrometers) aluminum oxide grinding wheels ("DLO WHEEL" made by
Sumitomo 3M K.K., diameter 50 mm, density 1.5 g/cm.sup.3, shore D
hardness 35) were prepared. The three grinding wheels were set to a
grinding device (a hard disk end-face grinding device made by
Shonan Engineering K.K.) capable of simultaneously grinding the
upper face and the right and left slanting faces of the edge of the
desk raw plate, and a grinding process was carried out under the
conditions of a peripheral velocity of 500 mm/sec. and a grinding
time of 30 seconds.
[0096] The pit removing rate of the ground face and the curvature
of the angle of the end face were calculated in the same manner as
Example 1. The results are shown in Table 1, below.
1 TABLE 1 Example 1 Example 2 Comparative Comp. Comp. First Second
First Second Example 1 Ex. 2 Ex. 3 Grinding Hardness 90 95 90 95 --
35 35 Wheel (Shore D) Density 1.8 2.0 1.8 2.0 -- 1.0 1.0
(g/cm.sup.3) Abrasive Al.sub.2O.sub.3 CeO.sub.2 Al.sub.2O.sub.3
CeO.sub.2 -- Al.sub.2O.sub.3 Al.sub.2O.sub.3 grain Particle 600
10000 60 10000 -- 220 220 size (JIS) Grinding Peripheral 2000 2000
2000 2000 1000 2000 500 Condi- velocity tions (m/min.) Load 2 to 5
2 to 5 2 to 5 2 to 5 -- 2 to 5 0.2 to 2 (kg) Time 10 10 10 20 60
3600 10 30 (sec.) Results Removing >95 >95 >95 >95 5 95
80 95 of rate of Grinding large pits (%).sup.a Removing >10
>80 >10 >95 0 90 0 0 rate of small pits (%).sup.b
Curvature <10 <10 <10 <10 <50 <100 <35 <20
(micrometer) .sup.aRemoval rate of large pits having a diameter of
not less than 10 micrometers. .sup.bRemoval rate of small pits
having a diameter of not more than 10 micrometers.
[0097] The present invention has now been described with reference
to several embodiments thereof. It will be apparent to those
skilled in the art that many changes can be made in the embodiments
described without departing from the scope according to the
invention. Thus, the scope of the present invention should not be
limited to the structures described herein, but rather by the
structures described by the language of the claims, and the
equivalents of those structures.
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