U.S. patent application number 15/504793 was filed with the patent office on 2017-09-07 for polishing pad.
This patent application is currently assigned to FUJIMI INCORPORATED. The applicant listed for this patent is FUJIMI INCORPORATED. Invention is credited to Koji KATAYAMA, Hitoshi MORINAGA, Keigo OHASHI, Eiichi YAMADA.
Application Number | 20170252892 15/504793 |
Document ID | / |
Family ID | 55399064 |
Filed Date | 2017-09-07 |
United States Patent
Application |
20170252892 |
Kind Code |
A1 |
KATAYAMA; Koji ; et
al. |
September 7, 2017 |
POLISHING PAD
Abstract
A polishing pad capable of removing waviness of a surface of a
polishing target having a curved surface is provided. A polishing
pad (10) includes a structure (40, 50) including a polishing
surface (30) formed of a hard resin layer (40), the structure (40,
50) allowing the polishing surface (30) to follow a curved surface
of a polishing target (90).
Inventors: |
KATAYAMA; Koji; (Aichi,
JP) ; OHASHI; Keigo; (Aichi, JP) ; YAMADA;
Eiichi; (Aichi, JP) ; MORINAGA; Hitoshi;
(Aichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIMI INCORPORATED |
Kiyosu-shi, Aichi |
|
JP |
|
|
Assignee: |
FUJIMI INCORPORATED
Kiyosu-shi, Aichi
JP
|
Family ID: |
55399064 |
Appl. No.: |
15/504793 |
Filed: |
July 30, 2015 |
PCT Filed: |
July 30, 2015 |
PCT NO: |
PCT/JP2015/003854 |
371 Date: |
February 17, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24B 37/22 20130101;
B24B 37/245 20130101; B24B 37/11 20130101; B24B 37/26 20130101 |
International
Class: |
B24B 37/24 20060101
B24B037/24; B24B 37/26 20060101 B24B037/26; B24B 37/22 20060101
B24B037/22 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2014 |
JP |
2014-172978 |
Claims
1. A polishing pad comprising: a structure including a polishing
surface formed of a hard resin layer, the structure allowing the
polishing surface to follow a curved surface of a polishing
target.
2. The polishing pad according to claim 1, wherein the structure
allowing the polishing surface to follow the curved surface of the
polishing target is a two-layer structure including: a soft resin
layer that supports the hard resin layer; and the hard resin
layer.
3. The polishing pad according to claim 2, wherein a groove is
formed in the polishing surface.
4. The polishing pad according to claim 3, wherein the groove
divides the hard resin layer into a plurality of regions.
5. The polishing pad according to claim 4, wherein the groove is
also formed in the soft resin layer.
6. The polishing pad according to claim 1, wherein a groove is
formed in the polishing surface.
7. The polishing pad according to claim 6, wherein the groove
divides the hard resin layer into a plurality of regions.
Description
TECHNICAL FIELD
[0001] The present invention relates to a polishing pad.
BACKGROUND ART
[0002] Buffing is known as a processing method for smoothing a
polishing target having a curved surface, for example, a vehicle
body painting surface of an automobile and the like (for example,
PTL 1). The buffing is a method of polishing the polishing target
in such a manner that a variety of polishing agents are applied
onto a circumference (surface) of a polishing wheel (buff) made of
cloth or other materials and are then rotated.
CITATION LIST
Patent Literature
[0003] PTL 1: JP 2012-251099 A
SUMMARY OF INVENTION
Technical Problem
[0004] However, by the buffing, it has been impossible to remove
waviness of the surface of the polishing target, and it has been
difficult to realize a beautiful surface finish.
[0005] It is an object of the present invention to provide a
polishing pad capable of removing waviness of a surface a polishing
target having a curved surface.
Solution to Problem
[0006] In order to solve the above-described problem, according to
an aspect of the present invention, there is provided a polishing
pad including a structure that includes a polishing surface formed
of a hard resin layer, the structure allowing the polishing surface
to follow a curved surface of a polishing target.
[0007] The above-described structure allowing the polishing surface
to follow the curved surface of the polishing target may be a
two-layer structure, which includes: a soft resin layer that
supports the hard resin layer; and the hard resin layer.
[0008] A groove may be formed in the polishing surface. This groove
may divide the hard resin layer into a plurality of regions .
Moreover, this groove may also be formed in the soft resin
layer.
Advantageous Effects of Invention
[0009] In accordance with the present invention, the polishing pad
capable of removing the waviness of the curved surface of the
polishing target can be realized.
[0010] The object and advantages of the present invention are
concretized and achieved by using the elements illustrated in the
scope of claims and combinations of the elements. It should be
interpreted that both of the above-mentioned general description
and the following detailed description are merely illustrations and
explanations, and do not limit the present invention like the scope
of claims.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. lA is a perspective view of a polishing pad according
to a first embodiment of the present invention;
[0012] FIG. 1B is a cross-sectional view of the polishing pad
illustrated in FIG. LA, taken along a line A-A;
[0013] FIG. 2A is an explanatory view of a surface shape of an
unpolished polishing target;
[0014] FIG. 2B is an explanatory view of a surface shape of an
already buffed polishing target, the surface shape being taken as a
comparative example;
[0015] FIG. 2C is an explanatory view of a surface shape of the
polishing target already polished by a polishing pad of FIG.
1A;
[0016] FIG. 2D is an explanatory view of a surface shape of the
polishing target already subjected to secondary polishing;
[0017] FIG. 3A is a top view of a polishing pad according to a
second embodiment of the present invention;
[0018] FIG. 3B is a cross-sectional view of the polishing pad
illustrated in FIG. 3A, taken along a line A-A;
[0019] FIG. 4A is a cross-sectional view of a first modification
example illustrated in FIG. 3A;
[0020] FIG. 4B is a cross-sectional view of a second modification
example of the polishing pad illustrated in FIG. 3A;
[0021] FIG. 5A is a top view of a third modification example of the
polishing pad illustrated in FIG. 3A;
[0022] FIG. 5B is a cross-sectional view of the polishing pad
illustrated in FIG. 5A, taken along a line A-A; and
[0023] FIG. 6 is a view illustrating a configuration example of an
automatic polisher that uses the polishing pad according to an
embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0024] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings.
1. FIRST EMBODIMENT
[0025] In a first embodiment, a surface of a polishing target
having a curved surface is polished by using a polishing pad having
a polishing surface formed of a hard resin layer. This polishing
pad has a structure of allowing a polishing surface, which is
formed of the hard resin layer, to follow the curved surface of the
polishing target. The polishing target may be, for example, a
resin-coated surface having a curved surface. The resin-coated
surface may be, for example, a coated surface of a vehicle body of
a vehicle or the like.
[0026] For example, the structure of allowing the polishing surface
of the polishing pad to follow the curved surface of the polishing
target may have a two-layer structure, which includes the hard
resin layer that forms the polishing surface and a soft resin layer
that supports this hard resin layer. In a case where the polishing
surface is pressed against the curved surface of the polishing
target, then the soft resin layer is distorted depending on the
curved surface, whereby the hard resin layer is warped, and the
polishing surface follows the curved surface of the polishing
target.
[0027] The structure of allowing the polishing surface of the
polishing pad to follow the curved surface of the polishing target
may be a structure, in which the hard resin layer is supported by
using an elastic member, whereby the elastic member is distorted
and the hard resin layer forming the polishing surface is warped
depending on the curved surface in the case where the polishing
surface is pressed against the curved surface of the polishing
target.
[0028] Hereinafter, a description will be made of a case where the
polishing pad according to the first embodiment has the two-layer
structure including the hard resin layer that forms the polishing
surface and the soft resin layer that supports this hard resin
layer. Note that, in the following description, the hard resin
layer that forms the polishing surface is simply written as a "hard
resin layer", and the soft resin layer that supports the hard resin
layer is simply written as a "soft resin layer".
[0029] Hereinafter, the first embodiment will be described in
detail.
1-1. Regarding Polishing Pad
[0030] FIG. 1A and FIG. 1B are referred to. A polishing pad 10 has
a two-layer structure, which includes a hard resin layer 40 and a
soft resin layer 50. The hard resin layer 40 forms a polishing
surface 30 of the polishing pad 10. The soft resin layer 50
supports the hard resin layer 40. In addition, in a case where the
polishing surface 30 is pressed against the curved surface of the
polishing target, the soft resin layer 50 is distorted depending on
the curved surface. Therefore, the hard resin layer 40 is warped
along the curved surface, and the polishing surface 30 follows the
curved surface of the polishing target.
1-2. Regarding Hard Resin Layer
[0031] In terms of A hardness defined in conformity with JIS K
6253, hardness of the hard resin layer 40 is preferably 50 degrees
or more, more preferably 60 degrees or more. Moreover, the hardness
of the hard resin layer 40 is preferably 95 degrees or less. For
example, the hardness of the hard resin layer 40 is preferably 60
degrees or more and 80 degrees or less, or the hardness of the hard
resin layer 40 is preferably 85 degrees or more and 95 degrees or
less . When the hardness of the hard resin layer 40 remains within
such a range, then the polishing for the curved surface of the
polishing target by the polishing pad 10 becomes less likely to
become copy polishing, and it becomes possible to remove waviness
of the surface of the polishing target.
[0032] A thickness of the hard resin layer 40 is not particularly
limited; however, is preferably 3.0 mm or less. Moreover, the
thickness of the hard resin layer 40 is preferably 0.5 mm or more.
When the thickness of the hard resin layer 40 remains within such a
range, then in the case where the polishing surface 30 is pressed
against the curved surface of the polishing target, it becomes easy
for the hard resin layer 40 to be warped along the curved surface
of the polishing target, and followability of the polishing surface
30 with respect to the curved surface of the polishing target is
enhanced. Therefore, such a waviness component of a surface shape
of the polishing target can be removed, and in addition, polishing
efficiency is enhanced since a contact area between the polishing
surface 30 and the curved surface is increased.
[0033] A material of the hard resin layer 40 is not particularly
limited, and just needs to be a material having the above-described
hardness. The material of the hard resin layer 40 may be, for
example, a polyurethane foam body or nonwoven fabric. The material
of the hard resin layer 40 may be, for example, nonwoven fabric in
which A hardness is 60 degrees or more and 80 degrees of less, or
may be a polyurethane foam body in which A hardness is 85 degrees
or more and 95 degrees or less.
1-3. Regarding Soft Resin Layer
[0034] In terms of E hardness defined in conformity with JIS K
6253, hardness of the soft resin layer 50 is preferably 30 degrees
or less. When the hardness of the soft resin layer 50 remains
within such a range, then it becomes easy for the soft resin layer
50 to be distorted in the case where the polishing surface 30 is
pressed against the curved surface of the polishing target. As a
result, it becomes easy for the hard resin layer 40 to be warped
along the curved surface of the polishing target, and the
followability of the polishing surface 30 with respect to the
curved surface of the polishing target is enhanced. Therefore, such
a waviness component of the surface shape of the polishing target
can be removed, and in addition, the polishing efficiency is
enhanced since the contact area between the polishing surface 30
and the curved surface is increased.
[0035] A thickness of the soft resin layer 50 is not particularly
limited; however, is preferably 5.0 mm or more. Moreover, the
thickness of the soft resin layer 50 is preferably 50 mm or less .
When the thickness of the soft resin layer 50 remains within such a
range, a distortion amount of the soft resin layer 50 and a warp
amount of the hard resin layer 40 can be ensured in the case where
the polishing surface 30 is pressed against the curved surface of
the polishing target.
[0036] The material of the soft resin layer 50 is not particularly
limited, and just needs to be a material having the above-described
hardness. The material of the soft resin layer 50 may be, for
example, a resin foam body such as a polyurethane foam body and a
polyethylene foam body.
1-4. Regarding Effects of First Embodiment
[0037] The polishing pad 10 of the first embodiment has the
polishing surface 30 formed of the hard resin layer 40. Therefore,
in comparison with the soft polishing surface, the polishing for
the surface of the polishing target is less likely to become copy
polishing. As a result, the waviness component of the surface shape
of the polishing target can be removed.
[0038] Moreover, the polishing pad 10 of the first embodiment
includes the structure of allowing the polishing surface 30 to
follow the curved surface of the polishing target. Therefore, the
polishing surface 30 follows the curved surface of the polishing
target, and accordingly, the waviness component of the surface
shape of the polishing target can be removed. In addition, the
polishing efficiency is enhanced since the contact area of the
polishing surface 30 in contact with the polishing target having
the curved surface is increased, and a time required to polish such
a relatively large polishing target can be shortened.
[0039] FIG. 2A to FIG. 2D are referred to. FIG. 2A schematically
shows a profile of the surface shape of the unpolished polishing
target. The unpolished surface shape has a surface roughness
component with a relatively high frequency and a waviness component
with a relatively low frequency.
[0040] FIG. 2B shows a profile of a surface shape of the already
buffed polishing target. In such buffing, hardness of polishing
cloth is relatively low, and the copy polishing is brought about.
Therefore, though the surface roughness component is removed, the
waviness component still remains even after the polishing.
[0041] FIG. 2C schematically shows a profile of the surface shape
of the polishing target already polished by the polishing pad 10 of
the first embodiment. The polishing surface 30 is formed of the
hard resin layer 40, and accordingly, the polishing for the surface
of the polishing target is less likely to become the copy
polishing. Therefore, the waviness component of the surface shape
of the polishing target is removed.
[0042] Ina case of removing a fine surface roughness component
after the polishing performed by the polishing pad 10, secondary
polishing for removing the surface roughness component may be
performed after such primary polishing performed by the polishing
pad 10. FIG. 2D schematically shows a profile of the surface shape
of the polishing target after the secondary polishing. By the
polishing performed by the polishing pad 10 and the secondary
polishing subsequent thereto, both of the surface roughness and
waviness of the polishing target are removed.
2. SECOND EMBODIMENT
[0043] Subsequently, a second embodiment of the present invention
will be described. Grooves are formed on a polishing surface of a
polishing pad according to the second embodiment. By a fact that
the grooves are formed on the polishing surface, it becomes easy
for the polishing surface to follow the curved surface of the
polishing surface in the case where the polishing surface is
pressed against the curved surface of the polishing target.
[0044] The grooves formed on the polishing surface may have a depth
sufficient to divide such a hard resin layer into a plurality of
pieces. The hard resin layer is divided by the grooves, whereby it
becomes possible for the hard resin layer to be displaced in an
abutting direction depending on the curved surface in the case
where the polishing surface is pressed against the curved surface
of the polishing target. Therefore, it becomes easy for the
polishing surface to follow the curved surface of the polishing
target.
[0045] The grooves as described above can be formed by removing the
resin layer of portions, which serve as the grooves, by etching and
the like, for example, after forming the two-layer structure
including the hard resin layer and the soft resin layer, however,
the present invention is not limited thereto. Moreover, the grooves
can be formed by scanning a surface of the pad by a circular
cutting blade while pressing the circular cutting blade, which
rotates at a high speed, against the pad by a predetermined amount
after forming such a two-layer structure.
[0046] The grooves, which divide the hard resin layer into a
plurality of pieces, may also be formed on the soft resin layer. By
a fact that the grooves are also formed on the soft resin layer, it
becomes easier for the hard resin layer to be displaced in the case
where the polishing surface is pressed against the surface of the
polishing target, and it becomes easy for the polishing surface 30
to follow the curved surface of the polishing target.
2-1. Form of Grooves
[0047] FIG. 3A and FIG. 3B are referred to. The same reference
numerals are assigned to constituents having the same functions as
those in FIG. 1A. First grooves 31 and second grooves 32 are formed
on the polishing surface 30 of the polishing pad 10. The first
grooves 31 are extended in a first direction on the polishing
surface 30, and the second grooves 32 are extended along a second
direction on the polishing surface 30, which is perpendicular to
the first direction. A plurality of the first grooves 31 and a
plurality of the second grooves 32 are formed on the polishing
surface 30, whereby the grooves are formed in a grid shape on the
polishing surface 30.
[0048] The depth of the first grooves 31 and the second grooves 32
may be the same as the thickness of the hard resin layer 40. That
is to say, the hard resin layer 40 may be divided into a plurality
of regions by the first grooves 31 and the second grooves 32.
Moreover, the first grooves 31 and the second grooves 32 are formed
on only the hard resin layer 40, and are not formed on the soft
resin layer 50.
[0049] A groove width of the first grooves 31 and the second
grooves 32 is preferably 0.5 mm or more for example. Moreover, the
groove width of the first grooves 31 and the second grooves 32 is
preferably 5.0 mm or less for example. When the groove width
remains within such a range, it can become easy for the polishing
surface 30 to be warped since a displacement amount of the hard
resin layer 40 in the case where the polishing surface 30 is
pressed against the curved surface of the polishing target is
ensured while suppressing a decrease of the contact area between
the polishing surface 30 and the polishing target, the decrease
being caused by forming the grooves.
[0050] A pitch of the first grooves 31 and a pitch of the second
grooves 32 are preferably 5.0 mm or more for example. Moreover, the
pitch of the first grooves 31 and the pitch of the second grooves
32 are preferably 50 mm or less for example.
[0051] When the pitches remain within such a range, a warp amount
of the whole of the polishing surface 30 in the case where the
polishing surface 30 is pressed against the curved surface of the
polishing target can be ensured while suppressing the decrease of
the contact area between the polishing surface 30 and the polishing
target, the decrease being caused by forming the grooves.
[0052] Dimensions of these groove width and pitches are also
applied to first to third modification examples to be described
below.
2-2. Regarding First Modification Example
[0053] FIG. 4A is referred to. The depth of the first grooves 31
and the second grooves 32 maybe smaller than the thickness of the
hard resin layer 40. That is to say, the hard resin layer 40 is not
divided into the plurality of pieces by the first grooves 31 and
the second grooves 32, and a thickness of the hard resin layer 40
of portions of the first grooves 31 and the second grooves 32 is
thinner than a thickness of other portions. Rigidity of the
portions of the first grooves 31 and the second grooves 32 is
decreased, and accordingly, it becomes easy for the hard resin
layer 40 to be warped. Therefore, it becomes easy for the polishing
surface 30 to follow the curved surface of the polishing
target.
2-3. Regarding Second Modification Example
[0054] FIG. 4B is referred to. The depth of the first grooves 31
and the second grooves 32 may be larger than the thickness of the
hard resin layer 40. That is to say, the first grooves 31 and the
second grooves 32 may be formed in the hard resin layer 40 and the
soft resin layer 50. Hence, a support surface 51 of the soft resin
layer 50, which supports the hard resin layer 40, is also divided
by the first grooves 31 and the second grooves 32. A plurality of
the divided hard resin layers 40 are supported individually by a
plurality of the divided support surfaces 51. The first grooves 31
and the second grooves 32 are also formed in the soft resin layer
50, and accordingly, rigidity of the soft resin layer 50 is
decreased, and it becomes easy for the soft resin layer 50 to be
distorted depending on the curved surface in the case where the
polishing surface 30 is pressed against the curved surface of
polishing target.
[0055] Moreover, the support surface 51 that supports the hard
resin layer 40 is divided, whereby binding force between the
support surfaces 51 is decreased, and it becomes easy for the
divided hard resin layers 40 to be displaced independently of one
another. Therefore, the displacement amount of the hard resin layer
50 in the abutting direction is increased, and it becomes easy for
the polishing surface 30 to follow the curved surface of the
polishing target.
2-4. Regarding Third Modification Example
[0056] FIG. 5A and FIG. 5B are referred to. On the polishing
surface 30, only the first grooves 31 are formed, and the second
grooves 32 are not formed. The plurality of first grooves 31 are
formed on the polishing surface 30, whereby the grooves are formed
in a stripe shape on the polishing surface 30.
[0057] The depth of the first grooves 31 may be larger than the
thickness of the hard resin layer 40. That is to say, the first
grooves 31 may be formed in the hard resin layer 40 and the soft
resin layer 50. Hence, the support surface 51 of the soft resin
layer 50, which supports the hard resin layer 40, is also divided
by the first grooves 31. A plurality of the divided hard resin
layers 40 are supported individually by a plurality of the divided
support surfaces 51. Note that the depth of the first grooves 31
may be the same as or smaller than the thickness of the hard resin
layer 40.
[0058] The second grooves 32 are omitted, and the grooves in a
stripe shape are formed on the polishing surface 30, whereby
strength of the polishing surface can be enhanced, and a number of
man-hours for forming the grooves is reduced, resulting in
contribution to cost reduction. Moreover, the first grooves 31 are
also formed in the hard resin layer 40, whereby a decrease of the
followability of the polishing surface 30, which is caused since
the second grooves 32 extended in the second direction are not
formed, is reduced.
3. REGARDING POLISHING METHOD
[0059] A configuration of a polishing device using the polishing
pad 10 and a polishing method using the polishing pad 10 are not
particularly limited. For example, the polishing pad 10 may be
attached onto a tip end of a hand polisher, and may be used for a
manual operation of polishing the surface of the polishing target
having the curved surface. Moreover, the polishing pad 10 may be
used for polishing treatment by an automatic polisher as described
below.
3-1. Configuration Example of Automatic Polisher
[0060] FIG. 6 is referred to. An automatic polisher 1 includes: a
robot arm 2; a polishing pad 10; a polishing tool 4; a pressing
pressure detector 5; and a controller 7. Reference numeral 90
denotes a polishing target. The polishing target 90 may be, for
example, a vehicle body of an automobile or the like, in which a
surface is coated with resin. The robot arm 2 has a plurality of
joints 20, 21 and 22, and can move a tip end portion 23, onto which
the polishing pad 10, the polishing tool 4 and the pressing
pressure detector 5 are attached, in a plurality of directions.
[0061] The polishing tool 4 is attached onto the tip end portion 23
through the pressing pressure detector 5, and by driving means
built in the polishing tool 4, rotates the polishing pad 10 about a
direction perpendicular to the polishing surface 30, the direction
being taken as a rotation axis. The controller 7 controls a
behavior of the robot arm 2 and the rotation of the polishing pad
10. From a polishing agent feeding mechanism (not shown), the
polishing agent is fed between the polishing pad 10 and the
polishing target 90. The controller 7 presses the polishing pad 10
against a surface of the polishing target 90 by the robot arm 2,
then rotates the polishing pad 10, and thereby polishes the surface
of the polishing target 90.
[0062] The pressing pressure detector 5 detects pressing pressure
of the polishing surface 30 against the polishing target 90. Based
on a detection result by the pressing pressure detector 5, the
controller 7 may adjust such force of pressing the polishing
surface 30 against the polishing target 90. The controller 7 may
control the robot arm 2 so that the polishing surface 30 can move
across the surface of the polishing target 90 while constantly
maintaining the pressing force of the polishing surface 30 against
the polishing target 90.
[0063] In a case of removing a fine surface roughness component
after the polishing performed by the polishing pad 10, secondary
polishing for removing the surface roughness component may be
performed. In this case, after the polishing by the polishing pad
10 is performed, the polishing pad attached onto the polishing tool
4 is replaced, and the surface of the polishing target 90 is
polished by using a polishing pad having lower hardness than the
polishing pad 10.
3-2. Regarding Polishing Agent
[0064] A description will be made of an example of the abrasives
for use in the above-described polishing method.
[0065] As the polishing agent, slurry can be used, which contains
abrasive grains selected from: particles composed of an oxide of
silicon or a metal element, such as silica, alumina, ceria,
titania, zirconia, iron oxide and manganese oxide; organic
particles composed of thermoplastic resin; and organic-inorganic
composite particles.
[0066] For example, for the polishing agent, it is preferable to
use alumina slurry, which enables a high polishing speed and is
easily available.
[0067] As alumina, there are .alpha.-alumina, .beta.-alumina,
.UPSILON.-alumina, .theta.-alumina and the like, which have crystal
forms different from one another, and an alumina compound called
hydrated alumina is also present. From a viewpoint of the polishing
speed, those containing .alpha.-alumina as amain component are more
preferable as the abrasive grains.
[0068] A mean particle diameter of the abrasive grains is
preferably 0.1 .mu.m or more, more preferably 0.3 .mu.m or more. As
the mean particle diameter is becoming larger, the polishing speed
is enhanced. In a case where the mean particle diameter remains
within the above-described range, it becomes easy to enhance the
polishing speed to a level that is particularly suitable for
practical use.
[0069] Moreover, the mean particle diameter is preferably 10.0
.mu.m or less, more preferably 5.0 .mu.m or less. As the mean
particle diameter is becoming smaller, dispersion stability of the
polishing agent is enhanced, and a scratch is suppressed from
occurring on the polishing surface.
[0070] In such a case where the mean particle diameter remains
within the above-described range, it becomes easy to enhance the
dispersion stability of the polishing agent and surface accuracy of
the polishing surface to levels which are particularly suitable for
practical use. Note that the mean particle diameter of the abrasive
grains can be measured by a pore electrical resistance method
(Coulter principle) method (measuring machine: Multisizer Type-III
made by Beckman Coulter, Inc.).
[0071] A content of the abrasive grains in the polishing agent is
preferably 0.1 mass % or more, more preferably 0.2 mass % or more,
still more preferably 0.5 mass % or more. As the content of the
abrasive grains is becoming larger, the polishing speed is
enhanced. In a case where the content of the abrasive grains
remains within the above-described range, it becomes easy to
enhance the polishing speed to the level that is particularly
suitable for practical use.
[0072] Moreover, the content of the abrasive grains is preferably
50 mass % or less, more preferably 25 mass % or less, still more
preferably 20 mass %. In a case where the content of the abrasive
grains remains within the above-described range, cost of the
polishing agent can be suppressed. Moreover, a surface defect can
be further suppressed from occurring on the surface of the
polishing target already polished by the polishing agent.
[0073] Besides the above-described abrasive grains, the polishing
agent may appropriately contain other components such as
lubricating oil, an organic solvent, a surfactant, and a
thickener.
[0074] The lubricating oil may be synthetic oil, mineral oil,
vegetable oil, or a combination of these.
[0075] The organic solvent may be alcohol, ether, glycols or
glycerins as well as a hydrocarbon-based solvent.
[0076] The surfactant may be so-called anion, cation, nonion or
amphoteric surfactant.
[0077] The thickener may be a synthetic thickener, a cellulose
thickener, or a natural thickener.
3-3. Regarding Secondary Polishing
[0078] Hardness of a polishing pad for use in the secondary
polishing is preferably lower than the hardness of the hard resin
layer 40 of the polishing pad 10. In terms of A hardness, for
example, the hardness of the polishing pad for use in the secondary
polishing is preferably less than 50 degrees, more preferably 40
degrees of less. Moreover, the hardness of the polishing pad for
use in the secondary polishing is preferably 30 degrees or more.
When the hardness of the polishing pad remains within such a range,
it becomes possible to remove the fine surface roughness component
on the surface of the polishing target.
[0079] A material of the polishing pad for use in the secondary
polishing is not particularly limited, and just needs to be a
material having the above-described hardness. The material of the
polishing pad for use in the secondary polishing may be, for
example, nonwoven fabric or suede. For example, the material of the
polishing pad for use in the secondary polishing may be suede in
which A hardness is 30 degrees or more to 40 degrees or less.
[0080] The polishing pad for use in the secondary polishing may
have a two-layer structure in a similar way to the polishing pad
10. That is to say, the polishing pad for use in the secondary
polishing may have a two-layer structure including: a relatively
hard first layer that forms the polishing surface; and a relatively
soft second layer that supports the first layer.
[0081] Hardness of the first layer is preferably lower than the
hardness of the hard resin layer 40 of the polishing pad 10. In
terms of A hardness, for example, the hardness of the first layer
is preferably less than 50 degrees, more preferably 40 degrees of
less. Moreover, the hardness of the first layer is preferably 30
degrees or more.
[0082] Thickness of the first layer is preferably 3.0 mm or less.
Moreover, the thickness of the first layer is preferably 0.5 mm or
more. When the thickness of the first layer remains within such a
range, then in the case where the polishing surface is pressed
against the curved surface of the polishing target, it becomes easy
for the first layer to be warped along the curved surface of the
polishing target, the contact area between the polishing surface
and the curved surface is increased, and the polishing efficiency
is enhanced.
[0083] A material of the first layer is not particularly limited,
and just needs to be a material having the above-described hardness
. The material of the first layer may be, for example, nonwoven
fabric or suede. For example, the material of the first layer may
be suede in which A hardness is 30 degrees or more to 40 degrees or
less.
[0084] A configuration of the second layer may be similar to the
configuration of the soft resin layer 50 of the polishing pad
10.
[0085] Grooves may also be formed on the polishing surface of the
polishing pad for use in the secondary polishing in a similar way
to the polishing pad 10 according to the second embodiment.
4. EXAMPLE
[0086] A hard resin layer, in which a thickness is 1.5 mm, a
material is a polyurethane foam body, and A hardness is 90, and a
soft resin layer, in which a thickness is 30.0 mm, a material is a
polyurethane foam body, and E hardness is 20, were laminated on
each other to form a polishing pad, and a resin-coated surface
thereof was polished. On the hard resin layer, grid-like grooves,
in which a width is 2.0 mm, a pitch is 20.0 mm, and a depth is 3.0
mm, were formed by scanning a surface of the pad by a circular
cutting blade while pressing the circular cutting blade, which
rotates at a high speed, against the pad by a predetermined amount
after forming such a two-layer structure. Moreover, alumina slurry
was used as a polishing agent.
[0087] As a result, a finish of a flat glossy surface, in which
arithmetic mean waviness (Wa) is 0.05 .mu.m or less, and filterable
maximum waviness (Wcm) is 0.3 .mu.m or less, was able to be
realized.
[0088] All the examples and conditional terms, which are described
herein, are intended for instructive purposes for helping readers
understand the present invention and a concept thereof given by the
inventors for the progress of the technology. The present invention
should be interpreted without being limited to the examples and the
conditions, which are specifically described above, and to the
configurations of the examples in this specification, which are
related to exemplification of superiority and inferiority of the
present invention. While the embodiments of the present invention
have been described in detail, it should be understood that it is
possible to add various changes, substitutions, and modifications
to the present invention without departing from the spirit and
scope of the present invention.
REFERENCE SIGNS LIST
[0089] 1 automatic polisher [0090] 2 robot arm [0091] 4 polishing
tool [0092] 5 pressing pressure detector [0093] 7 controller [0094]
10 polishing pad [0095] 30 polishing surface [0096] 31 first groove
[0097] 32 second groove [0098] 40 hard resin layer [0099] 50 soft
resin layer [0100] 51 support surface
* * * * *