TECHNICAL FIELD
[0001] The present invention relates to a grinding material.
BACKGROUND ART
[0002] In general, for example, a grinding material containing fixed abrasive grains is
used for processing a glass substrate used for an electronic device such as a hard
disk. As such a grinding material, a grinding material having a structure in which
a grinding layer containing abrasive grains and a binder is overlaid on a surface
of a base is known (for example, see Japanese Patent No.
6091704). In a conventional grinding material, the grinding layer has a plurality of regions
(grinding portions) separated by grooves on a surface of the grinding layer, and the
maximum peak height of surfaces of the grinding portions is controlled, whereby both
a high level of processing efficiency and a high level of finished flatness are achieved.
[0003] In the conventional grinding material, which is used in fixed abrasive grinding,
the grinding layer is gradually worn by grinding, and a life of the grinding material
ends when the grinding layer is worn out. Therefore, to extend the lifetime of the
conventional grinding material, the thickness of the grinding layer, i.e., the height
of each of the grinding portions needs to be increased.
[0004] However, when the height of the grinding portion is directly increased, the aspect
ratio of the grinding portion is increased; consequently, the grinding portion is
likely to collapse at a time of grinding. Accordingly, the grinding material is likely
to reach the end of its life due to the collapse of the grinding portion. When the
aspect ratio of the grinding portion is reduced to prevent the grinding portion from
collapsing, the area of each grinding portion is increased. In the case where each
grinding portion has a large area, when the grinding layer is formed by printing or
the like, warpage of the base is likely to occur with hardening shrinkage of the grinding
layer. Therefore, warpage of the base may make it difficult to perform uniform grinding.
Although warpage of the base is reduced by increasing the average thickness of the
base, the reduction is limited. Furthermore, when the thickness of the base is increased,
the flexibility and ductility of the base decrease, making it difficult for the grinding
material to follow the surface shape of a workpiece. Thus, a grinding rate may also
decrease.
PRIOR ART DOCUMENTS
PATENT DOCUMENTS
[0005] Patent Document 1: Japanese Patent No.
6091704
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0006] The present invention has been made in view of the foregoing disadvantages, and it
is an object of the present invention to provide a grinding material in which grinding
portions can be increased in thickness while a decrease in grinding rate is inhibited.
MEANS FOR SOLVING THE PROBLEMS
[0007] As a result of an intensive investigation of a grinding material in which, even when
grinding portions are thick, warpage of a base is less likely to occur while a decrease
in grinding rate is inhibited, the present inventors have found that warpage of the
base is dramatically ameliorated by adjusting the thickness of the base and arranging
the grinding portions in a staggered manner, thereby accomplishing the present invention.
Although the reason why warpage of the base is dramatically ameliorated by arranging
the grinding portions in a staggered manner is not clear, it is presumed that the
staggered arrangement of the grinding portions makes it easy for warpage occurring
in grinding portions, which are alternately arranged, to be cancelled out.
[0008] That is to say, according to an aspect of the invention made for solving the aforementioned
problems, a grinding material includes a base, and a grinding layer overlaid on a
front face side of the base and containing abrasive grains and a binder. The grinding
layer includes a plurality of columnar grinding portions. The plurality of the grinding
portions are configured so that the grinding portions are arranged in a staggered
manner. The average thickness of the grinding portions is no less than 300 µm. The
area of a top face of each of the grinding portions is no less than 6 mm
2. The average thickness of the base is no less than 300 µm and no greater than 3,000
µm.
[0009] In the grinding material, the area of the top face of each of the grinding portions
is no less than the lower limit; therefore, even when the average thickness of the
grinding portions is no less than the lower limit, the grinding portions are resistant
to collapse at a time of grinding. Furthermore, in the grinding material, the average
thickness of the base is no less than the lower limit, and the plurality of the grinding
portions are configured so that the grinding portions are arranged in a staggered
manner; therefore, even when the average thickness of the grinding portions is no
less than the lower limit, warpage of the base is less likely to occur. Moreover,
in the grinding material, the average thickness of the base is no greater than the
upper limit; therefore, the surface shape of a workpiece can be easily followed, and
the grinding rate can be increased. Thus, in the grinding material, the grinding portions
can be increased in thickness while a decrease in grinding rate is inhibited.
[0010] The ratio of the average thickness of the grinding portions to the average thickness
of the base is preferably no less than 0.7 and no greater than 4. The ratio of the
average thickness of the grinding portions to the average thickness of the base is
set to be no less than the lower limit, whereby the grinding portions can be increased
in thickness while a decrease in grinding rate is inhibited. Furthermore, the ratio
of the average thickness of the grinding portions to the average thickness of the
base is set to be no greater than the upper limit, whereby warpage of the base can
be inhibited.
[0011] The value obtained by dividing the area of the top face of each of the grinding portions
by the average thickness of the grinding portions is preferably no less than 0.015
mm
2/µm and no greater than 0.04 mm
2/µm. When the value obtained by dividing the area of the top face of each of the grinding
portions by the average thickness of the grinding portions is set to fall within the
above range, the grinding portions can be increased in thickness while warpage of
the base is inhibited.
[0012] The area of the top face of each of the grinding portions is preferably no greater
than 100 mm
2, and the average thickness of the grinding portions is preferably no greater than
5,000 µm. When the area of the top face of each of the grinding portions is set to
be no greater than the upper limit, warpage of the base can be inhibited. Furthermore,
when the average thickness of the grinding portions is set to be no greater than the
upper limit, the grinding portions can be made resistant to collapse.
[0013] The binder preferably contains a thermosetting resin as a principal component. The
binder contains the thermosetting resin as a principal component, whereby, for example,
glass breakage at a time of grinding a glass material can be inhibited.
[0014] The expression "a plurality of grinding portions are configured so that the grinding
portions are arranged in a staggered manner" refers to an array of grinding portions
which are arranged at regular intervals in a plurality of columns that are parallel
to each other, wherein, in a direction that passes through a center of a grinding
portion in one column and is orthogonal to the one column, a center of a grinding
portion in a column adjacent to the one column is not located. Furthermore, the term
"principal component" as referred to means a component having the highest content,
wherein the content thereof is preferably no less than 50% by mass, and more preferably
no less than 90% by mass.
EFFECTS OF THE INVENTION
[0015] As described in the foregoing, in the grinding material according to the present
invention, the grinding portions can be increased in thickness while a decrease in
grinding rate is inhibited. Therefore, the grinding material according to the present
invention has a long lifetime.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
Fig. 1 is a schematic partial planar view of a grinding material according to an embodiment
of the present invention.
Fig. 2 is a schematic partial cross-sectional view taken along line A-A in Fig. 1.
Fig. 3 is a schematic partial cross-sectional view of a grinding material according
to an embodiment different from that in Fig. 2.
DESCRIPTION OF EMBODIMENTS
[0017] An embodiment of the present invention will be described below in detail with appropriate
reference to the drawings.
[0018] A grinding material 1 shown in Figs. 1 and 2 includes a base 10, a grinding layer
20 overlaid on a front face side of the base 10, and an adhesion layer 30 overlaid
on a back face side of the base 10. Furthermore, the grinding layer 20 has a plurality
of grinding portions 20a and a groove 20b provided between the grinding portions 20a.
[0019] The grinding material 1 is suitably used, for example, as a fixed abrasive grinding
material for surface grinding of a glass material, particularly for surface grinding
of an aluminosilicate glass substrate, which is used for cover glass, a hard disk,
and the like.
Base
[0020] The base 10 is a plate-like or sheet-like member for supporting the grinding layer
20.
[0021] A principal component of the base 10 is not particularly limited, and examples thereof
include polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP),
polyethylene (PE), polyimide (PI), polyethylene naphthalate (PEN), aramid, aluminum,
copper, and the like. Of these, PET, PC and aluminum that offer superior adhesion
to the grinding layer 20 are preferred. Furthermore, a surface of the base 10 may
be subjected to a treatment for enhancing adhesion, such as a chemical treatment,
a corona treatment, or a primer treatment.
[0022] Furthermore, the base 10 preferably has flexibility or ductility. When the base 10
thus has flexibility or ductility, whereby the grinding material 1 follows the surface
shape of a workpiece and the contact area between a grinding surface and the workpiece
is increased, the grinding rate is further increased. Examples of a material of the
base 10 having flexibility include PET, PC, and the like. Furthermore, examples of
a material of the base 10 having ductility include aluminum, copper, and the like.
[0023] The shape and size of the base 10 are not particularly limited, and the base 10 may
have, for example, a square shape measuring no less than 140 mm and no greater than
160 mm per side, a discoid shape with a diameter of no less than 200 mm and no greater
than 2,022 mm, an annular shape with an outer diameter of no less than 200 mm and
no greater than 2,022 mm and an inner diameter of no less than 100 mm and no greater
than 658 mm, or the like. Alternatively, a plurality of bases 10 aligned on a planar
surface may be supported by a single support.
[0024] The lower limit of the average thickness of the base 10 is 300 µm, and preferably
500 µm. Meanwhile, the upper limit of the average thickness of the base 10 is 3,000
µm, and preferably 1,000 µm. When the average thickness of the base 10 is less than
the lower limit, warpage of the base 10 may be likely to occur. Conversely, when the
average thickness of the base 10 is greater than the upper limit, the flexibility
of the base 10 may be insufficient, and an effect of increasing the grinding rate
may be insufficient.
Grinding Layer
[0025] In the grinding layer 20, each of the grinding portions 20a contains a plurality
of abrasive grains 21 and a binder 22.
Abrasive Grains
[0026] Examples of the abrasive grains 21 include diamond abrasive grains, alumina abrasive
grains, silica abrasive grains, ceria abrasive grains, silicon carbide abrasive grains,
and the like. Of these, diamond abrasive grains, which are harder than the other abrasive
grains, are preferred. By using diamond abrasive grains as the abrasive grains 21,
grinding force can be increased, and the grinding rate can be further increased.
[0027] It is to be noted that diamonds of the diamond abrasive grains may be monocrystalline
or polycrystalline, or may be Ni-coated or subjected to other treatments. Of these,
monocrystalline diamonds and polycrystalline diamonds are preferred. Monocrystalline
diamonds are harder than the other diamonds and have high cutting force. Furthermore,
polycrystalline diamonds are easily cleaved between microcrystals constituting a polycrystal
and can thus resist dulling, so that the grinding rate will not be reduced significantly
even when grinding is performed for a long period of time.
[0028] The average grain diameter of the abrasive grains 21 is appropriately selected in
view of the grinding rate and the surface roughness of a workpiece after grinding.
The lower limit of the average grain diameter of the abrasive grains 21 is preferably
2 µm, more preferably 10 µm, and still more preferably 15 µm. Meanwhile, the upper
limit of the average grain diameter of the abrasive grains 21 is preferably 150 µm,
more preferably 125 µm, and still more preferably 100 µm. When the average grain diameter
of the abrasive grains 21 is less than the lower limit, the grinding force of the
grinding material 1 may be insufficient, and the grinding rate may decrease. Conversely,
when the average grain diameter of the abrasive grains 21 is greater than the upper
limit, the grinding accuracy may be impaired. The term "average grain diameter" as
referred to herein means the 50% value (50% grain diameter, D50) on the cumulative
grain size distribution curve based on the volume as measured by, for example, laser
diffraction.
[0029] The lower limit of the content of the abrasive grains 21 in the grinding portions
20a is preferably 0.5% by volume, more preferably 2% by volume, and still more preferably
4% by volume. Meanwhile, the upper limit of the content of the abrasive grains 21
is preferably 55% by volume, more preferably 45% by volume, and still more preferably
35% by volume. When the content of the abrasive grains 21 is less than the lower limit,
the grinding force of the grinding layer 20 may be insufficient. Conversely, when
the content of the abrasive grains 21 is greater than the upper limit, the grinding
layer 20 may fail to hold the abrasive grains 21.
Binder
[0030] A principal component of the binder 22 is not particularly limited, and examples
thereof include a resin and an inorganic substance. Of these, a resin, particularly
a thermosetting resin, which is less likely to cause glass breakage at a time of grinding
a glass material and is suitable for glass grinding, is preferred.
[0031] Examples of the resin include resins such as polyurethane, a phenol resin, epoxy,
polyester, cellulose, an ethylene copolymer, polyvinyl acetal, an polyacrylic acid
and a salt thereof, polyacrylic acid ester, polyvinyl alcohol, polyvinyl chloride,
polyvinyl acetate, and polyamide. Of these, polyacrylic acid ester, epoxy, polyester,
and polyurethane, with which favorable adhesion to the base 10 can be easily ensured,
are preferred, and thermosetting epoxy is more preferred. It is to be noted that at
least part of the resin may be cross-linked.
[0032] Furthermore, examples of the inorganic substance include a silicic acid salt, a phosphate,
polyvalent metal alkoxide, and the like. Of these, a silicic acid salt that offers
high abrasive-grain holding force is preferred. Examples of such a silicic acid salt
include sodium silicate, potassium silicate, and the like.
[0033] It is to be noted that, depending on the purpose, the binder 22 may appropriately
contain any of a variety of auxiliary agents and additives, such as a dispersant,
a coupling agent, a surfactant, a lubricant, a defoaming agent, and a colorant.
Others
[0034] Furthermore, in the grinding layer 20, the grinding portions 20a may contain a filler.
Examples of such a filler include oxides such as alumina, silica, cerium oxide, magnesium
oxide, zirconia, and titanium oxide and composite oxides such as silica-alumina, silica-zirconia,
and silica-magnesia. These may be used alone, or as needed, two or more kinds of these
may be used in combination. Of these, alumina that offers high grinding force is preferred.
[0035] Although the average grain diameter of the filler depends on the average grain diameter
of the abrasive grains 21, the lower limit of the average grain diameter of the filler
is preferably 0.01 µm, and more preferably 2 µm. Meanwhile, the upper limit of the
average grain diameter of the filler is preferably 40 µm, more preferably 20 µm, and
still more preferably 15 µm. When the average grain diameter of the filler is less
than the lower limit, the filler may have an insufficient effect of increasing the
elastic modulus of the binder 22, and thus, the grinding rate may decrease. Meanwhile,
when the average grain diameter of the filler is greater than the upper limit, the
filler may inhibit the grinding force of the abrasive grains 21.
[0036] Furthermore, the average grain diameter of the filler is preferably smaller than
the average grain diameter of the abrasive grains 21. The lower limit of the ratio
of the average grain diameter of the filler to the average grain diameter of the abrasive
grains 21 is preferably 0.01, more preferably 0.05, and still more preferably 0.1.
Meanwhile, the upper limit of the ratio of the average grain diameter of the filler
to the average grain diameter of the abrasive grains 21 is preferably 0.8, and more
preferably 0.6. When the ratio of the average grain diameter of the filler to the
average grain diameter of the abrasive grains 21 is less than the lower limit, the
filler may have an insufficient effect of increasing the elastic modulus of the binder
22, and thus, the grinding rate may decrease. Conversely, when the ratio of the average
grain diameter of the filler to the average grain diameter of the abrasive grains
21 is greater than the upper limit, the filler may inhibit the grinding force of the
abrasive grains 21.
[0037] Although the content of the filler in the grinding portions 20a depends on the content
of the abrasive grains 21, the lower limit of the content of the filler in the grinding
portions 20a is preferably 15% by volume, and more preferably 30% by volume. Meanwhile,
the upper limit of the content of the filler is preferably 75% by volume, and more
preferably 72% by volume. When the content of the filler is less than the lower limit,
the filler may have an insufficient effect of increasing the elastic modulus of the
binder 22, and thus, the grinding rate may decrease. Conversely, when the content
of the filler is greater than the upper limit, the filler may inhibit the grinding
force of the abrasive grains 21.
Grinding Portions
[0038] Each of the grinding portions 20a has a columnar shape. That is to say, the area
of a bottom face of each of the grinding portions 20a is no less than 0.9 times and
no greater than 1.5 times, preferably no less than 0.93 times and no greater than
1.2 times, and more preferably no less than 0.95 times and no greater than 1.05 times
the area of a top face of a corresponding grinding portion of the grinding portions
20a.
[0039] The plurality of the grinding portions 20a have an identical shape and are configured
so that the grindings portions 20a are arranged in a staggered manner. The shape of
the top face of each of the grinding portions 20a may be a circular shape as in Fig.
1, a square shape, a polygonal shape, or the like. In view of an effect of reducing
warpage of the base 10, a circular shape and a square shape, which have relatively
low anisotropy, are preferred, and a circular shape is particularly preferred.
[0040] The plurality of the grinding portions 20a are arranged in a plurality of columns
that are parallel to each other. The intervals between the grinding portions 20a arranged
in one column (distance between centers thereof and pitch) are uniform. The intervals
between the grinding portions 20a are identical among the plurality of the columns.
Furthermore, the intervals between the columns (the distance between straight lines
connecting the centers of the grinding portions 20a in the respective columns) are
equal to the intervals between the grinding portions 20a. Moreover, the centers of
the grinding portions 20a in a column adjacent to the one column are located in directions
that are orthogonal to the one column, namely, the midpoints of the straight lines
connecting the centers of the grinding portions 20a adjacent to each other in the
one column. In short, the positions of the grinding portions 20a in the column adjacent
to the one column are shifted from the positions of the grinding portions 20a in the
one column by a half pitch. Thus, as for the arrangement of the plurality of the grinding
portions 20a, an identical pattern is repeated every other column of the plurality
of the columns. The plurality of the grinding portions 20a are arranged in this manner,
whereby warpage of the base 10 can be effectively reduced.
[0041] The lower limit of the average pitch of the grinding portions 20a arranged in one
column is preferably 3 mm, and more preferably 5 mm. Meanwhile, the upper limit of
the average pitch is preferably 15 mm, and more preferably 10 mm. When the average
pitch is less than the lower limit, the average area of the top faces of the grinding
portions 20a cannot be increased, and the grinding portions 20a may be likely to collapse
at a time of grinding. Conversely, when the average pitch is greater than the upper
limit, the width of the groove 20b between the grinding portions 20a adjacent to each
other may increase, and warpage of the base 10 may easily occur.
[0042] The lower limit of the average area of the top faces of the grinding portions 20a
is 6 mm
2, and preferably 15 mm
2. Meanwhile, the upper limit of the average area of the top faces of the grinding
portions 20a is preferably 100 mm
2, and more preferably 30 mm
2. When the average area of the top faces of the grinding portions 20a is less than
the lower limit, the grinding portions 20a may be likely to collapse at a time of
grinding. Conversely, when the average area of the top faces of the grinding portions
20a is greater than the upper limit, warpage of the base 10 may easily occur.
[0043] The lower limit of the area occupancy percentage of the plurality of the grinding
portions 20a with respect to the entirety of the grinding layer 20 is preferably 5%,
more preferably 20%, and still more preferably 30%. Meanwhile, the upper limit of
the area occupancy percentage of the grinding portions 20a is preferably 60%, and
more preferably 55%. When the area occupancy percentage of the grinding portions 20a
is less than the lower limit, a pressure applied at a time of grinding may be excessively
concentrated on the grinding portions 20a having a small area, and thus, the grinding
portions 20a may be separated from the base 10. Conversely, when the area occupancy
percentage of the grinding portions 20a is greater than the upper limit, the contact
area between the grinding layer 20 and a workpiece may increase at a time of grinding,
and thus, the grinding rate may decrease owing to frictional resistance. It is to
be noted that the concept "the area of the entirety of the grinding layer" also involves
the area of the groove in the grinding layer.
[0044] The lower limit of the average thickness of the grinding portions 20a is 300 µm,
and preferably 1,000 µm. Meanwhile, the upper limit of the average thickness of the
grinding portions 20a is preferably 5,000 µm, and more preferably 3,000 µm. When the
average thickness of the grinding portions 20a is less than the lower limit, the lifetime
may be insufficient. Conversely, when the average thickness of the grinding portions
20a is greater than the upper limit, the grinding portions 20a may be likely to collapse
at a time of grinding.
[0045] The lower limit of the ratio of the average thickness of the grinding portions 20a
to the average thickness of the base 10 is preferably 0.7, and more preferably 1.
Meanwhile, the upper limit of the ratio of the average thickness of the grinding portions
20a is preferably 4, and more preferably 2.5. When the ratio of the average thickness
of the grinding portions 20a is less than the lower limit, even though the grinding
rate is decreased by increasing the thickness of the base 10, the increase in thickness
of the base 10 may fail to have a sufficient effect of reducing warpage thereof. Conversely,
when the ratio of the average thickness of the grinding portions 20a is greater than
the upper limit, warpage of the base 10 may be likely to occur.
[0046] The lower limit of the value obtained by dividing the area of the top face of each
of the grinding portions 20a by the average thickness of the grinding portions 20a
(the area to thickness ratio) is preferably 0.015 mm
2/µm, and more preferably 0.02 mm
2/µm. Meanwhile, the upper limit of the area to thickness ratio is preferably 0.04
mm
2/µm, and more preferably 0.03 mm
2/µm. When the area to thickness ratio is less than the lower limit, the grinding portions
20a may be likely to collapse at a time of grinding. Conversely, when the area to
thickness ratio is greater than the upper limit, warpage of the base 10 may easily
occur.
Groove
[0047] A bottom face of the groove 20b is constituted by the surface of the base 10.
[0048] Although the average width of the groove 20b is determined by the area of the top
face of each of the grinding portions 20a and the area occupancy percentage thereof,
the lower limit of the average width of the groove 20b is preferably 0.3 mm, and more
preferably 0.5 mm. Meanwhile, the upper limit of the average width of the groove 20b
is preferably 10 mm, and more preferably 8 mm. When the average width of the groove
20b is less than the lower limit, the groove 20b may be clogged with abrasive powder
generated due to grinding. Conversely, when the average width of the groove 20b is
greater than the upper limit, a workpiece may be likely to be caught in the groove
20b at a time of grinding, and thus, the workpiece may be damaged. It is to be noted
that the term "average width of the groove" as referred to herein means, as shown
in Fig. 1, the length of a portion in which a straight line L, connecting centers
M of the grinding portions 20a that are adjacent to each other in one column, passes
through the groove 20b ("D" in Fig. 1).
Adhesion Layer
[0049] The adhesion layer 30 is a layer which fixes the grinding material 1 to a support
which supports the grinding material 1 and attaches the grinding material 1 to a grinding
apparatus.
[0050] An adhesive used as the adhesion layer 30 is not particularly limited, and examples
thereof include a reactive adhesive, an instantaneous adhesive, a hot melt adhesive,
a tacky adhesive which is a detachable adhesive, and the like.
[0051] As the adhesive used as the adhesion layer 30, a tacky adhesive is preferred. By
use of a tacky adhesive as the adhesive used for the adhesion layer 30, the grinding
material 1 can be detached from the support for replacement, which facilitates reuse
of the grinding material 1 and the support. Such a tacky adhesive is not particularly
limited, and examples thereof include an acrylic tacky adhesive, an acryl-rubber tacky
adhesive, a natural rubber tacky adhesive, a synthetic rubber tacky adhesive such
as a butyl rubber tacky adhesive, a silicone tacky adhesive, a polyurethane tacky
adhesive, and the like.
[0052] The lower limit of the average thickness of the adhesion layer 30 is preferably 0.05
mm, and more preferably 0.1 mm. Meanwhile, the upper limit of the average thickness
of the adhesion layer 30 is preferably 0.3 mm, and more preferably 0.2 mm. When the
average thickness of the adhesion layer 30 is less than the lower limit, the adhesive
force may be insufficient, and the grinding material 1 may be separated from the support.
Conversely, when the average thickness of the adhesion layer 30 is greater than the
upper limit, workability may be impaired; for example, due to the thickness of the
adhesion layer 30, it may be difficult to cut the grinding material 1 into a desired
shape.
Method for Producing Grinding Material
[0053] For example, the grinding material 1 can be produced by a production method including
a preparation step, a grinding layer-forming step, and s an adhesion layer-attaching
step.
Preparation Step
[0054] In the preparation step, a composition for a grinding layer containing the abrasive
grains 21 and the binder 22 is prepared.
[0055] Specifically, a composition for a grinding layer containing materials for forming
the abrasive grains 21 and the binder 22 is prepared as a coating liquid. It is to
be noted that the content of the abrasive grains 21 in a solid content corresponds
to the content of the abrasive grains 21 in the grinding portions 20a after the production;
therefore, the amount of the solid content is appropriately determined so that the
content of the abrasive grains 21 in the grinding portions 20a can be a desired value.
[0056] Furthermore, to control the viscosity and fluidity of the coating liquid, a diluent
such as water or alcohol is added. Due to the dilution, a portion of the abrasive
grains 21 contained in the grinding portions 20a can be made to protrude from a surface
of the binder 22. That is to say, by adding the diluent, when the composition for
the grinding layer is dried in the grinding layer-forming step, the thickness of the
binder 22 decreases, whereby the protruding amount of the abrasive grains 21 can be
increased. Thus, due to the dilution, a high grinding rate can be achieved from an
initial stage of grinding.
Grinding Layer-Forming Step
[0057] In the grinding layer-forming step, the grinding layer 20 is formed by printing the
composition for the grinding layer, the composition having been prepared in the preparation
step. The grinding layer-forming step includes a coating step and a drying step.
Coating Step
[0058] In the coating step, the surface of the base 10 is coated with the composition for
the grinding layer.
[0059] Specifically, by use of the coating liquid, which has been prepared in the preparation
step, the grinding layer 20, which has the plurality of the grinding portions 20a
and the groove 20b provided between the grinding portions 20a, is formed on the surface
of the base 10 by a printing process. To form the groove 20b, a mask having a shape
corresponding to the shape of the groove 20b is prepared, and the coating liquid is
printed through the mask. Examples of the printing process include screen printing,
metal mask printing, and the like.
[0060] As the mask for printing, a mask made of SUS or a fluorocarbon resin is preferred.
The mask made of SUS or a fluorocarbon resin can be increased in thickness; therefore,
the grinding portions 20a having a large average thickness can be easily formed.
[0061] The thickness of the grinding portions 20a can be adjusted mainly by the thickness
of the mask and the coating amount. Therefore, in the coating step, the coating amount
of the composition for the grinding layer is preferably adjusted so that the average
thickness of the grinding portions 20a can be a desired value.
Drying Step
[0062] In the drying step, the coating liquid (the composition for the grinding layer) after
the coating step is dried by heating. By being dried by heating, the coating liquid
is hardened, and consequently, the grinding layer 20 is formed. The drying step is
performed after the mask is removed.
[0063] The lower limit of the heating temperature in the drying step is preferably 80°C,
and more preferably 100°C. Meanwhile, the upper limit of the heating temperature is
preferably 300°C, and more preferably 200°C. When the heating temperature is less
than the lower limit, the composition for the grinding layer may fail to be sufficiently
hardened, the wear amount may increase, and the lifetime of the grinding material
1 may be shortened. Conversely, when the heating temperature is greater than the upper
limit, the grinding portion 20a may be altered by heat.
[0064] Although the heating time in the drying step depends on the heating temperature,
the lower limit the heating time is preferably 2 hours, and more preferably 2.5 hours.
Meanwhile, the upper limit of the heating time is preferably 40 hours, more preferably
32 hours, and still more preferably 20 hours. When the heating time is less than the
lower limit, the composition for the grinding layer may fail to be sufficiently hardened,
the wear amount may increase, and the lifetime of the grinding material 1 may be shortened.
Conversely, when the heating time is greater than the upper limit, the production
efficiency may be impaired.
Adhesion Layer-Attaching Step
[0065] In the adhesion layer-attaching step, the adhesion layer 30 is overlaid on the back
face side of the base 10. Specifically, for example, the adhesion layer 30, which
has a tape shape and has been formed in advance, is attached to the back face of the
base 10.
Advantages
[0066] In the grinding material 1, the area of the top face of each of the grinding portions
20a is no less than 6 mm
2; therefore, even when the average thickness of the grinding portions 20a is no less
than 300 µm, the grinding portions 20a are resistant to collapse at a time of grinding.
Furthermore, in the grinding material 1, the average thickness of the base 10 is no
less than 300 µm, and the plurality of the grinding portions 20a is configured so
that the grinding portions 20a are arranged in a staggered manner; therefore, even
when the average thickness of the grinding portions 20a is no less than 300 µm, warpage
of the base 10 is less likely to occur. Moreover, in the grinding material 1, the
average thickness of the base 10 is no greater than 3,000 µm; therefore, the surface
shape of a workpiece can be easily followed, and the grinding rate can be increased.
Thus, in the grinding material 1, the thickness of the grinding portions 20a can be
increased while a decrease in grinding rate is inhibited.
Other Embodiments
[0067] The present invention is not limited to the aforementioned embodiment, and can be
implemented in variously modified or improved embodiments other than that described
above.
[0068] Although the interval between the columns of the plurality of the grinding portions
is equal to the interval between the grinding portions in one column in the above
embodiment, the interval between the columns may be different from the interval between
the grinding portions in one column. For example, the grinding portions may be arranged
in one column and a column adjacent to the one column, and a grinding portion in the
one column and two grinding portions that are in the column adjacent to the one column,
the two grinding portions being the closest to the grinding portion, may form a regular
triangle. It is to be noted that, in the case where the interval between the columns
is different from the interval between the grinding portions in one column, the interval
between the columns is preferably no less than 3 mm and no greater than 15 mm. When
the interval between the columns is less than the lower limit, the average area of
the top faces of the grinding portions cannot be increased, and the grinding portions
may be likely to collapse at a time of grinding. Conversely, when the interval between
the columns is greater than the upper limit, the width of the groove between the columns
adjacent to each other may increase, and warpage of the base may easily occur.
[0069] Furthermore, although the positions of the grinding portions in one column are shifted
from the positions of the grinding portions in a column adjacent to the one column
by a half pitch in the above embodiment, the amount of the positional shift is not
limited to the half pitch and may be, for example, 1/3 pitch. In this case, as for
the arrangement of the plurality of the grinding portions, an identical pattern is
repeated every third column.
[0070] Although the grinding material includes the adhesion layer in the above embodiment,
the adhesion layer is not an essential constituent feature and can be omitted. In
the case where the grinding material does not include the adhesion layer, the adhesion
layer-attaching step is omitted from the method for producing a grinding material.
[0071] Alternatively, as illustrated in Fig. 3, a grinding material 2 may include a support
40, which is overlaid on a back face side of the grinding material 2 with the adhesion
layer 30 therebetween, and a second adhesion layer 31, which is overlaid on a back
face side of the support 40. Since the grinding material 2 includes the support 40,
the grinding material 2 is easy to handle.
[0072] Examples of a principal component of the support 40 include thermoplastic resins
such as polypropylene, polyethylene, polytetrafluoroethylene, and polyvinyl chloride;
and engineering plastics such as polycarbonate, polyamide, and polyethylene terephthalate.
Such a material is used as a principal component of the support 40, whereby the support
40 has flexibility, the grinding material 2 follows the surface shape of a workpiece,
and the grinding surface can easily come in contact with the workpiece; thus, the
grinding rate is further increased.
[0073] The average thickness of the support 40 may be, for example, no less than 0.5 mm
and no greater than 3 mm. When the average thickness of the support 40 is less than
the lower limit, the strength of the grinding material 2 may be insufficient. Meanwhile,
when the average thickness of the support 40 is greater than the upper limit, it may
be difficult to attach the support 40 to a grinding apparatus, or the flexibility
of the support 40 may be insufficient.
[0074] The adhesives which may be used as the adhesive layer 30 are also applicable to the
second adhesive layer 31. Furthermore, the average thickness of the second adhesion
layer 31 may be similar to that of the adhesion layer 30.
EXAMPLES
[0075] Hereinafter, the present invention will be explained in more detail by way of Examples
and Comparative Examples, but the present invention should not be construed as being
limited to the following Examples.
Example 1
[0076] Diamond abrasive grains ("SCMD-C12-22", manufactured by Zhengzhou Sino-Crystal Diamond
Co., Ltd.; average grain diameter: 16 µm), alumina (Al
2O
3, "LA4000", manufactured by Pacific Rundum Co.,Ltd.; average grain diameter: 4 µm)
as a filler, and an epoxy resin ("JER828", manufactured by Mitsubishi Chemical Corporation)
as a binder were mixed, and the content of the diamond abrasive grains in the solid
content and the content of the filler in the solid content were adjusted to be 3%
by volume and 75% by volume, respectively, whereby a coating liquid was obtained.
[0077] As a base, a base (average thickness: 500 µm) containing polycarbonate, which is
a thermosetting resin, as a principal component was prepared, and a surface of the
base was coated with the coating liquid by printing. As a printing pattern, a metal
mask having an average thickness of 350 µm and provided with openings each having
a circular shape with a diameter of 3.9 mm in a planar view (average area: 11.95 mm
2) was used, wherein the area occupancy percentage of the openings was 9%. It is to
be noted that the openings are arranged in a staggered manner. Furthermore, the coating
amount was adjusted so that the average thickness of grinding portions was 350 µm.
The coating liquid was dried in an oven at 120°C for 16 hours to be hardened. In this
manner, a grinding material of Example 1 was obtained.
Example 2
[0078] An aluminum sheet (A1050; average thickness: 300 µm) was prepared as a base, and
a surface of the base was coated with a coating liquid similar to that of Example
1 by printing. As a printing pattern, a metal mask having an average thickness of
350 µm and provided with openings each having a square shape measuring 2.6 mm per
side in a planar view (average area: 6.76 mm
2) was used, wherein the area occupancy percentage of the openings was 44%. It is to
be noted that the openings are arranged in a staggered manner. Furthermore, the coating
amount was adjusted so that the average thickness of grinding portions was 350 µm.
The coating liquid was dried in an oven at 120°C for 16 hours to be hardened. In this
manner, a grinding material of Example 2 was obtained.
Example 3
[0079] An aluminum sheet (average thickness: 300 µm) was prepared as a base, and a surface
of the base was coated with a coating liquid similar to that of Example 1 by printing.
As a printing pattern, a fluorocarbon resin mask having an average thickness of 1,000
µm and being provided with openings each having a circular shape with a diameter of
6 mm in a planar view (average area: 28.27 mm
2) was used, wherein the area occupancy percentage of the openings was 44%. It is to
be noted that the openings are arranged in a staggered manner. Furthermore, the coating
amount was adjusted so that the average thickness of grinding portions was 1,000 µm.
The coating liquid was dried in an oven at 120°C for 16 hours to be hardened. In this
manner, a grinding material of Example 3 was obtained.
Example 4
[0080] A grinding material of Example 4 was obtained in a manner similar to that of Example
3, except that a base (average thickness: 500 µm) containing polycarbonate as a principal
component was used as a base.
Example 5
[0081] Abase (average thickness: 500 µm) containing polycarbonate as a principal component
was prepared as a base, and a surface of the base was coated with a coating liquid
similar to that of Example 1 by printing. As a printing pattern, a fluorocarbon resin
mask having an average thickness of 350 µm and being provided with openings each having
a square shape measuring 2.6 mm per side in a planar view (average area 6.76 mm
2) was used, wherein the area occupancy percentage of the openings was 44%. It is to
be noted that the openings are arranged in a staggered manner. Furthermore, the coating
amount was adjusted so that the average thickness of grinding portions was 350 µm.
The coating liquid was dried in an oven at 120°C for 16 hours to be hardened. In this
manner, a grinding material of Example 5 was obtained.
Comparative Example 1
[0082] Abase (trade name "Melinex S", manufactured by Teijin DuPont Films Co., Ltd.; average
thickness: 75 µm) containing polyethylene terephthalate as a principal component was
prepared as a base, and a surface of the base was coated with a coating liquid similar
to that of Example 1 by printing. As a printing pattern, a metal mask having an average
thickness of 350 µm and being provided with openings each having a square shape measuring
1.5 mm per side in a planar view (average area: 2.25 mm
2) was used, wherein the area occupancy percentage of the openings was 36%. It is to
be noted that the openings were regularly arrayed in a block pattern. Furthermore,
the coating amount was adjusted so that the average thickness of grinding portions
was 350 µm. The coating liquid was dried in an oven at 120°C for 16 hours to be hardened.
In this manner, a grinding material of Comparative Example 1 was obtained.
Comparative Example 2
[0083] A grinding material of Comparative Example 2 was obtained in a manner similar to
that of Comparative Example 1, except that an aluminum sheet (average thickness: 300
µm) was used as a base.
Comparative Example 3
[0084] Abase (average thickness: 100 µm) containing polycarbonate as a principal component
was prepared as a base, and a surface of the base was coated with a coating liquid
similar to that of Example 1 by printing. As a printing pattern, a fluorocarbon resin
mask having an average thickness of 1,000 µm and being provided with openings each
having a circular shape with a diameter of 6 mm in a planar view (average area: 28.27
mm
2) was used, wherein the area occupancy percentage of the openings was 44%. It is to
be noted that the openings are arranged in a staggered manner. Furthermore, the coating
amount was adjusted so that the average thickness of grinding portions was 1,000 µm.
The coating liquid was dried in an oven at 120°C for 16 hours to be hardened. In this
manner, a grinding material of Comparative Example 3 was obtained.
Comparative Example 4
[0085] Abase (average thickness: 500 µm) containing polycarbonate as a principal component
was prepared as a base, and a surface of the base was coated with a coating liquid
similar to that of Example 1 by printing. As a printing pattern, a fluorocarbon resin
mask having an average thickness of 350 µm and being provided with openings each having
a square shape measuring 4 mm per side in a planar view (average area: 16 mm
2) was used, wherein the area occupancy percentage of the openings was 34%. It is to
be noted that the openings were regularly arrayed in a block pattern. Furthermore,
the coating amount was adjusted so that the average thickness of grinding portions
was 350 µm. The coating liquid was dried in an oven at 120°C for 16 hours to be hardened.
In this manner, a grinding material of Comparative Example 4 was obtained.
Evaluation
[0086] Regarding to the grinding materials of Examples 1 to 5 and Comparative Examples 1
to 4, warpage of the grinding material, the lifetime of the grinding material, and
the collapse resistance of the grinding portions were evaluated in accordance with
the following criteria. The results are shown in Table 1.
Warpage of Grinding Material
[0087] Warpage of the grinding material was visually judged in accordance with the following
criteria.
- A: there is no deformation on a rear side of the base (a side opposite to the surface
on which the grinding layer is formed), and no warpage is recognized.
- B: although deformation is observed on the rear side of the base, when left to stand
on a flat surface, the grinding material follows the flat surface.
- C: deformation is observed on the rear side of the base, and, when the grinding material
is left to stand on a flat surface, a bend-back thereof is recognized.
Lifetime of Grinding Material
[0088] The lifetime of the grinding material is conceived to be determined by the average
thickness of the grinding portions. Therefore, the evaluation was carried out in accordance
with the following criteria.
- A: the average thickness of the grinding portions is no less than 1,000 µm, and the
lifetime is long.
- B: the average thickness of the grinding portions is no less than 300 µm and less
than 1,000 µm, and the lifetime is somewhat short.
- C: the average thickness of the grinding portions is less than 300 µm, and the lifetime
is short.
Collapse Resistance of Grinding Portions
[0089] The collapse resistance of the grinding portions is conceived to be determined by
the ratio of the area of a top face of each of the grinding portions to the height
of the corresponding grinding portion. Specifically, the collapse resistance is conceived
to become higher as the value obtained by dividing the area of the top face of each
of the grinding portions by the average thickness of the grinding portions (the area
to thickness ratio) becomes larger. Therefore, the area to thickness ratio was calculated,
and the obtained value was employed in the following criteria.
- A: the area to thickness ratio is no less than 0.02 mm2/µm, and the grinding portions are resistant to collapse.
- B: the area to thickness ratio is no less than 0.015 mm2/µm and less than 0.02 mm2/µm, and the grinding portions are relatively resistant to collapse.
- C: the area to thickness ratio is less than 0.015 mm2/µm, and the grinding portions are likely to collapse.
Table 1
|
Grinding portion |
Base |
Height ratio (grinding portion/base) |
Evaluation results |
Shape |
Arrangement |
Diameter or length per side |
Area |
Percentage occupancy |
Height |
Area/height |
Thickness |
Material |
Warpage |
Lifetime |
Falling over resitance |
|
|
(mm) |
(mm2) |
(%) |
(µm) |
(mm2/µm) |
(µm) |
|
Example 1 |
Circular |
Staggered |
3.9 |
11.95 |
9 |
350 |
0.034 |
500 |
PC |
0.70 |
A |
A |
A |
Example 2 |
Square |
Staggered |
2.6 |
6.76 |
44 |
350 |
0.019 |
300 |
A1 |
1.17 |
A |
B |
B |
Example 3 |
Circular |
Staggered |
6 |
28.27 |
44 |
1,000 |
0.028 |
300 |
A1 |
3.33 |
B |
A |
A |
Example 4 |
Circular |
Staggered |
6 |
28.27 |
44 |
1,000 |
0.028 |
500 |
PC |
2.00 |
A |
A |
A |
Example 5 |
Square |
Staggered |
2.6 |
6.76 |
44 |
350 |
0.019 |
500 |
PC |
0.70 |
A |
B |
B |
Comparative Example 1 |
Square |
Block |
1.5 |
2.25 |
36 |
350 |
0.006 |
75 |
PET |
4.67 |
C |
B |
C |
Comparative Example 2 |
Square |
Block |
15 |
2.25 |
36 |
350 |
0.006 |
300 |
A1 |
1.17 |
A |
B |
C |
Comparative Example 3 |
Circular |
Staggered |
6 |
28.27 |
44 |
1,000 |
0.028 |
100 |
PC |
10.00 |
C |
A |
A |
Comparative Example 4 |
Square |
Block |
4 |
16 |
34 |
350 |
0.046 |
500 |
PC |
0.70 |
C |
B |
A |
[0090] With regard to the material of the base in Table 1, "PC" denotes polycarbonate, "PET"
denotes polyethylene terephthalate, and "Al" denotes an aluminum sheet.
[0091] Table 1 indicates that in each of the grinding materials of Examples 1 to 5, the
grinding portions are resistant to collapse, the grinding layer is thick, and the
lifetime is long, while warpage of the base is suppressed. Meanwhile, in each of the
grinding materials of Comparative Examples 1 and 3, in which the average thickness
of the base is less than 300 µm, warpage of the base occurs. In the grinding material
of Comparative Example 2, in which the area of the top face of each of the grinding
portions is less than 6 mm
2, the grinding portions are likely to collapse. In the grinding material of Comparative
Example 4, in which the grinding portions are not arranged in a staggered manner,
warpage of the base occurs.
[0092] The aforementioned results indicate that by arranging grinding portions of a grinding
material in a staggered manner, setting the area of a top face of each of the grinding
portions to be no less than 6 mm
2, and setting the average thickness of a base to be no less than 300 µm, a grinding
material can be obtained in which warpage of the base is suppressed, the grinding
portions are resistant to collapse, and the average thickness of a grinding layer
is no less than 300 µm; and which has a long lifetime and a high grinding rate.
INDUSTRIAL APPLICABILITY
[0093] In the grinding material according to the present invention, the thickness of grinding
portions can be increased while a decrease in grinding rate is inhibited. Thus, the
grinding material according to the present invention has a long lifetime.
EXPLANATION OF THE REFERENCE SYMBOLS
[0094]
1, 2 grinding material
10 base
20 grinding layer
20a grinding portion
20b groove
21 abrasive grains
22 binder
30 adhesion layer
31 second adhesion layer
40 support