U.S. patent application number 10/996782 was filed with the patent office on 2005-07-07 for polishing composition and polishing method.
Invention is credited to Ohashi, Keigo, Owaki, Toshiki.
Application Number | 20050148291 10/996782 |
Document ID | / |
Family ID | 34708651 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050148291 |
Kind Code |
A1 |
Ohashi, Keigo ; et
al. |
July 7, 2005 |
Polishing composition and polishing method
Abstract
A polishing composition contains silicon dioxide, an alkaline
compound, and water. Silicon dioxide is, for example, colloidal
silica, fumed silica, or precipitated silica. The alkaline compound
is, for example, ammonium carbonate, potassium carbonate, sodium
carbonate, ammonium hydrogen carbonate, potassium hydrogen
carbonate, sodium hydrogen carbonate, ammonium phosphate, potassium
phosphate, sodium phosphate, ammonium hydrogen phosphate, potassium
hydrogen phosphate, or sodium hydrogen phosphate. The polishing
composition can be suitably used in applications for polishing a
glass substrate.
Inventors: |
Ohashi, Keigo; (Gifu-shi,
JP) ; Owaki, Toshiki; (Konan-shi, JP) |
Correspondence
Address: |
VIDAS, ARRETT & STEINKRAUS, P.A.
6109 BLUE CIRCLE DRIVE
SUITE 2000
MINNETONKA
MN
55343-9185
US
|
Family ID: |
34708651 |
Appl. No.: |
10/996782 |
Filed: |
November 24, 2004 |
Current U.S.
Class: |
451/41 ;
51/308 |
Current CPC
Class: |
C09G 1/02 20130101; G11B
5/8404 20130101; B24B 37/044 20130101 |
Class at
Publication: |
451/041 ;
051/308 |
International
Class: |
B24B 001/00; B24D
003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2003 |
JP |
2003-396163 |
Claims
1. A polishing composition for use in an application for polishing
a glass substrate, the polishing composition comprising silicon
dioxide, an alkaline compound, and water.
2. The polishing composition according to claim 1, wherein the
silicon dioxide is colloidal silica, fumed silica, or precipitated
silica.
3. The polishing composition according to claim 2, wherein the
silicon dioxide is colloidal silica.
4. The polishing composition according to claim 3, wherein the
colloidal silica has a mean particle diameter D.sub.SA, which is
determined from the specific surface area of the colloidal silica
by a BET method, of 5 to 300 nm.
5. The polishing composition according to claim 3, wherein the
colloidal silica has a mean particle diameter D.sub.N4, which is
determined by a laser diffraction scattering method, of 5 to 300
nm.
6. The polishing composition according to claim 2, wherein the
silicon dioxide is fumed silica having a mean particle diameter
D.sub.SA, which is determined from the specific surface area of the
colloidal silica by a BET method, of 10 to 300 nm.
7. The polishing composition according to claim 2, wherein the
silicon dioxide is fumed silica having a mean particle diameter
D.sub.N4, which is determined by a laser diffraction scattering
method, of 30 to 500 nm.
8. The polishing composition according to claim 1, wherein the
content of silicon dioxide in the polishing composition is 0.1 to
50 mass %.
9. The polishing composition according to claim 8, wherein the
content of silicon dioxide in the polishing composition is 3 to 30
mass %.
10. The polishing composition according to claim 1, wherein the
alkaline compound is ammonium carbonate, potassium carbonate,
sodium carbonate, ammonium hydrogen carbonate, potassium hydrogen
carbonate, sodium hydrogen carbonate, ammonium phosphate, potassium
phosphate, sodium phosphate, ammonium hydrogen phosphate, potassium
hydrogen phosphate, sodium hydrogen phosphate, potassium
pyrophosphate, sodium pyrophosphate, potassium citrate, potassium
hydrogen citrate, potassium gluconate, potassium succinate,
ammonium acetate, potassium oxalate, ammonium hydrogen oxalate,
ammonium tartrate, potassium tartrate, ammonium hydrogen tartrate,
potassium sodium tartrate, potassium sorbate, calcium nitrate,
potassium ferricyanide, ammonium fluoride, potassium fluoride,
calcium fluoride, potassium hydroxide, ammonium hydroxide, or
tetramethyl ammonium hydroxide.
11. The polishing composition according to claim 1, wherein the
content of the alkaline compound in the polishing composition is
0.05 to 10 mass %.
12. The polishing composition according to claim 11, wherein the
content of the alkaline compound in the polishing composition is
0.3 to 5 mass %.
13. The polishing composition according to claim 1, further
comprising an oxidizing agent.
14. The polishing composition according to claim 13, wherein the
oxidizing agent is hydrogen peroxide, ammonium persulfate,
potassium chlorate, potassium perchlorate, sodium perchlorate,
potassium periodate, sodium periodate, potassium bromate, or sodium
bromate
15. The polishing composition according to claim 13, wherein the
content of the oxidizing agent in the polishing composition is
0.005 to 10 mass %.
16. The polishing composition according to claim 15, wherein the
content of the oxidizing agent in the polishing composition is 0.03
to 5 mass %.
17. The polishing composition according to claim 1, further
comprising a chelating agent, a surfactant, or a preservative.
18. A method for polishing a glass substrate, the method
comprising: preparing a polishing composition comprising silicon
dioxide, an alkaline compound, and water; and polishing the surface
of a glass substrate, using the prepared polishing composition.
19. The method for polishing a glass substrate according to claim
18, wherein said polishing the surface of a glass substrate
comprises: preliminarily polishing the surface of the glass
substrate; and finish-polishing the surface of the preliminarily
polished glass substrate, in which the polishing composition is
used in the finish-polishing of the surface of the preliminarily
polished glass substrate.
20. The method for polishing a glass substrate according to claim
18, wherein said preparing a polishing composition comprises
diluting the polishing composition with water.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a polishing composition for
use in polishing of a glass substrate for an information-recording
medium, which is used for a hard disk and the like. The present
invention also relates to a polishing method using such a polishing
composition.
[0002] Conventionally, there is a known polishing composition for
use in applications for polishing a glass substrate for an
information-recording medium. Japanese Laid-Open Patent Publication
No. 2001-89748 discloses a polishing composition (hereinafter
referred to as the first prior art polishing composition)
containing an abrasive mainly composed of a rare earth oxide such
as cerium oxide, and water. Japanese Laid-Open Patent Publication
No. 2000-144112 discloses a polishing composition (hereinafter
referred to as the second prior art polishing composition)
containing an abrasive that comprises at least one selected from
the group consisting of an iron-containing oxide and an
iron-containing basic compound, and water. These first and second
prior art polishing compositions mechanically polish a glass
substrate by the action of the abrasive.
[0003] Requirements to be met by a polishing composition for use in
applications for polishing a glass substrate include:
[0004] (1) the surface roughness of the polished glass substrate
must be small;
[0005] (2) the polishing composition is easy to clean off, namely,
the polishing composition is easily removed by cleaning from the
glass substrate;
[0006] (3) the abrasive has good dispersibility in the polishing
composition; and
[0007] (4) the polishing composition has a high stock removal rate,
i.e., the polishing composition is highly capable of polishing a
glass substrate.
[0008] The first and second prior art polishing compositions,
however, do not satisfy the above requirements, and are thus
susceptible to improvement.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the present invention is to
provide a polishing composition that can be suitably used in
applications for polishing a glass substrate. Another object of the
present invention is to provide a polishing method using such a
polishing composition.
[0010] To achieve the foregoing and other objectives and in
accordance with the purpose of the present invention, the invention
provides a polishing composition for use in applications for
polishing a glass substrate. The polishing composition contains
silicon dioxide, an alkaline compound, and water.
[0011] The invention also provides a method for polishing a glass
substrate. The method includes preparing the above polishing
composition and polishing the surface of a glass substrate, using
the prepared polishing composition.
[0012] Other aspects and advantages of the invention will become
apparent from the following description, illustrating by way of
example the principles of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] One embodiment of the present invention will now be
described.
[0014] A glass substrate for an information-recording medium, such
as a magnetic disc, is formed of, for example, aluminosilicate
glass, soda lime glass, soda aluminosilicate glass, almino
borosilicate glass, borosilicate glass, quartz glass, or
crystallized glass. The main crystal phase of the crystallized
glass may be spodumene, mullite, aluminum borate crystal,
.beta.-quartz solid solution, .alpha.-quartz, cordierite,
enstatite, celsian, wollastonite, anorthite, forsterite, lithium
metasilicate, or lithium disilicate. A glass substrate is usually
provided to a chemical machine polishing (CMP) process so as to
have the surface thereof mirror-finished.
[0015] Typically, the process of polishing a glass substrate is
divided into a plurality of polishing steps to be conducted, for
the purpose of improving the stock removal rate, as well as the
quality of the surface of the polished glass substrate. The
plurality of polishing steps include, for example, a step of
roughly polishing the glass substrate surface and a step of
superfinely polishing the glass substrate surface. In other words,
the plurality of polishing steps include, for example, a step of
preliminarily polishing the glass substrate surface and a step of
finish-polishing the glass substrate surface. A polishing
composition according the present embodiment is used, for example,
in the final polishing step (finish-polishing step) among the
plurality of polishing steps. The polished glass substrate is
usually subjected to a chemical strengthening process using a
low-temperature ion exchange method or the like, in order to
improve resistance to shock and vibration.
[0016] The polishing composition according to the present
embodiment contains silicon dioxide, an alkaline compound, and
water.
[0017] Silicon dioxide serves as an abrasive for mechanically
polishing a glass substrate. Silicon dioxide may be colloidal
silica, fumed silica, or precipitated silica. Among them, colloidal
silica or fumed silica is preferable as being capable of reducing
the surface roughness of a polished glass substrate, and colloidal
silica is more preferable. One or more kinds of silicon dioxide may
be contained in the polishing composition.
[0018] When silicon dioxide is colloidal silica, the mean particle
diameter D.sub.SA of colloidal silica, which is determined from the
specific surface area thereof by the BET method, is preferably in
the range of 5 to 300 nm, more preferably in the range of 5 to 200
nm, and most preferably in the range of 5 to 120 nm. The mean
particle diameter D.sub.N4 of colloidal silica, which is determined
by the laser diffraction scattering method, is preferably in the
range of 5 to 300 nm, more preferably in the range of 5 to 200 nm,
and most preferably in the range of 5 to 150 nm. When silicon
dioxide is fumed silica, the mean particle diameter D.sub.SA of
fumed silica is preferably in the range of 10 to 300 nm, more
preferably in the range of 10 to 200 nm, and most preferably in the
range of 10 to 120 nm. The mean particle diameter D.sub.N4 of fumed
silica is preferably in the range of 30 to 500 nm, more preferably
in the range of 40 to 400 nm, and most preferably in the range of
50 to 300 nm. When the mean particle diameter D.sub.SA or D.sub.N4
of colloidal silica is too small, or when the mean particle
diameter D.sub.SA or D.sub.N4 of fumed silica is too small, it is
highly possible that a sufficiently high stock removal rate will
not be obtained. When the mean particle diameter D.sub.SA or
D.sub.N4 of colloidal silica is too large, or when the mean
particle diameter D.sub.SA or D.sub.N4 of fumed silica is too
large, it is highly possible that the surface roughness of the
polished glass substrate will become large, or scratching will
occur on the surface of the polished glass substrate.
[0019] The content of silicon dioxide in the polishing composition
is preferably in the range of 0.1 to 50 mass %, more preferably in
the range of 1 to 40 mass %, and most preferably in the range of 3
to 30 mass %. When the content of silicon dioxide is less than 0.1
mass %, a sufficiently high stock removal rate might not be
obtained, or polishing the glass substrate may become difficult due
to high polishing resistance. When the content of silicon dioxide
exceeds 50 mass %, the viscosity of the polishing composition
excessively increases to make the polishing composition apt to
gelate, leading to reduction in handleability of the polishing
composition.
[0020] The alkaline compound serves as a polishing accelerator for
accelerating mechanical polishing by silicon dioxide. The reason
why the alkaline compound accelerates mechanical polishing is
presumably that the alkaline compound acts on the surface of
silicon dioxide for activation, thereby increasing the mechanical
polishing force of silicon dioxide. The alkaline compound also
corrodes or etches the glass substrate surface, as a secondary
action, to chemically polish the glass substrate surface. The
chemical polishing action of the alkaline compound is weaker than
the mechanical polishing action of silicon dioxide.
[0021] The alkaline compound may be alkali metal salt, alkaline
earth metal salt, or ammonium salt of one acid selected from
carbonic acid, phosphoric acid, pyrophosphoric acid (diphosphoric
acid), citric acid, gluconic acid, succinic acid, acetic acid,
oxalic acid, tartaric acid, sorbic acid, and nitric acid.
Alternatively, the alkaline compound may be ferricyanide, fluoride,
or hydroxide of one kind selected from alkali metal, alkaline earth
metal, and ammonia. Further alternatively, the alkaline compound
may be quaternary ammonium hydroxide. Alkali metal in the alkaline
compound may be potassium, lithium, and sodium. Alkaline earth
metal in the alkaline compound may be calcium. Among them, alkali
metal salt, alkaline earth metal salt, or ammonium salt of one acid
selected from carbonic acid, phosphoric acid, and pyrophosphoric
acid are preferable, since the stock removal rate is strongly
improved.
[0022] Specifically, examples of the alkaline compound may include
ammonium carbonate, potassium carbonate, sodium carbonate, ammonium
hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen
carbonate, ammonium phosphate, potassium phosphate, sodium
phosphate, ammonium hydrogen phosphate such as diammonium hydrogen
phosphate, potassium hydrogen phosphate such as dipotassium
hydrogen phosphate, sodium hydrogen phosphate such as disodium
hydrogen phosphate, potassium pyrophosphate, sodium pyrophosphate,
potassium citrate, potassium hydrogen citrate such as dipotassium
hydrogen citrate, potassium gluconate, potassium succinate,
ammonium acetate, potassium oxalate, ammonium hydrogen oxalate,
ammonium tartrate, potassium tartrate, ammonium hydrogen tartrate,
potassium sodium tartrate, potassium sorbate, calcium nitrate,
potassium ferricyanide, ammonium fluoride, potassium fluoride,
calcium fluoride, potassium hydroxide, ammonium hydroxide, and
tetramethyl ammonium hydroxide (TMAH). Among them, ammonium
carbonate, potassium carbonate, sodium carbonate, ammonium hydrogen
carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate,
ammonium phosphate, potassium phosphate, sodium phosphate, ammonium
hydrogen phosphate, potassium hydrogen phosphate, and sodium
hydrogen phosphate are preferable, since the stock removal rate is
strongly improved. One or more alkaline compounds may be contained
in the polishing composition.
[0023] The content of the alkaline compound in the polishing
composition is preferably in the range of 0.05 to 10 mass %, more
preferably in the range of 0.1 to 8 mass %, and most preferably in
the range of 0.3 to 5 mass %. When the content of the alkaline
compound is less than 0.05 mass %, it is highly possible that a
sufficiently high stock removal rate will not be obtained because
the alkaline compound weakly acts to chemically polish the glass
substrate surface. When the content of the alkaline compound
exceeds 10 mass %, the viscosity of the polishing composition
excessively increases to make the polishing composition apt to
gelate, which is uneconomical and further increases the possibility
of producing roughness on the surface of the polished glass
substrate.
[0024] Water serves to dissolve or disperse ingredients other than
water of the polishing composition. Water preferably contains as
little impurities as possible so as to avoid inhibiting the actions
of other ingredients. Specifically, pure water or ultrapure water,
obtained by removing impurity ions with an ion-exchange resin and
then contaminants through a filter, or distilled water, is
preferable.
[0025] The polishing composition may further contain an oxidizing
agent. The oxidizing agent serves as a polishing accelerator for
accelerating mechanical polishing by silicon dioxide by means of
oxidizing the glass substrate surface. The oxidizing agent may be
aqueous solution of hydrogen peroxide (31 mass %), or may be alkali
metal salt, such as potassium salt and sodium salt, or ammonium
salt of one acid selected from persulfuric acid, chloric acid,
perchloric acid, periodic acid, and bromic acid. Specifically,
examples of the oxidizing agent may include hydrogen peroxide,
ammonium persulfate, potassium chlorate, potassium perchlorate,
sodium perchlorate, potassium periodate, sodium periodate,
potassium bromate, and sodium bromate. Among them, hydrogen
peroxide is preferable, since hydrogen peroxide strongly act to
accelerate mechanical polishing by silicon dioxide. One or more
oxidizing agents may be contained in the polishing composition.
[0026] The content of the oxidizing agent in the polishing
composition is preferably in the range of 0.005 to 10 mass %, more
preferably in the range of 0.01 to 8 mass %, and most preferably in
the range of 0.03 to 5 mass %. When the content of the oxidizing
agent is less than 0.005 mass %, it is highly possible that a
sufficiently high stock removal rate will not be obtained because
the oxidizing agent weakly acts to accelerate mechanical polishing
by silicon dioxide. When the content of the oxidizing agent exceeds
10 mass %, the viscosity of the polishing composition excessively
increases to make the polishing composition apt to gelate, which is
uneconomical and further increases the possibility of producing
roughness on the surface of the polished glass substrate.
[0027] The polishing composition may further contain a chelating
agent, a surfactant, a preservative, or the like according to
need.
[0028] The polishing composition is prepared by mixing ingredients,
other than water, with water. In the mixing, a blade-type agitator
or an ultrasonic disperser may be used. There is no limitation to
the order of mixing the ingredients, other than water, into
water.
[0029] A polishing composition according to the present embodiment
may be provided for use after dilution with water, or without
dilution. When the polishing composition is diluted with water, the
dilution ratio (ratio by volume) is preferably not more than 50
times, more preferably not more than 20 times, and most preferably
not more than 10 times. When the dilution rate exceeds 50 times,
the content of silicon dioxide and the alkaline compound in the
polishing composition after dilution might become excessively low,
resulting in failure to obtain a sufficiently high stock removal
rate.
[0030] The case where a glass substrate is polished by conducting
the two-stage polishing process consisting of the rough polishing
step and the superfine polishing step will be described. First, in
the rough polishing step, the surface of a glass substrate is
relatively roughly polished using polishing slurry containing
cerium oxide. Next, in the superfine polishing step as the final
polishing step, the glass substrate surface is superfinely polished
using the polishing composition according to the present
embodiment. In the superfine polishing, in a state where the glass
substrate attached to a polishing head is kept pressed to a
polishing pad on a turntable at constant pressure, the polishing
composition is provided to the surface of the polishing pad while
the polishing head and the turntable are rotated.
[0031] It is to be noted that a glass substrate may be polished in
a single-staged polishing process using a polishing composition
according to the present embodiment, in place of a multi-stage
polishing process.
[0032] The present embodiment has the following advantages.
[0033] A polishing composition according to the present embodiment
contains silicon dioxide as an abrasive. This reduces the surface
roughness of the polished glass substrate, as compared to a
polishing composition containing cerium oxide as an abrasive.
Presumably, this is attributed to the fact that the primary
particle of cerium oxide has an irregular form whereas the primary
particle of silicon dioxide has a spherical form. Namely, it is
presumed that, with the primary particle in spherical form, silicon
dioxide is capable of polishing the glass substrate surface more
finely than cerium oxide, thereby to reduce surface roughness of
the polished glass substrate.
[0034] Moreover, silicon dioxide has lower reactivity to a glass
substrate material than cerium oxide. For this reason, silicon
dioxide attached to the glass substrate is readily removed by
cleaning from the glass substrate without reacting with a glass
substrate material and sticking to the glass substrate surface. It
can therefore be said that a polishing composition according to the
present embodiment has the property of being readily cleaned off
from the polishing surface.
[0035] Furthermore, silicon dioxide has greater resistance to
agglomeration and higher dispersibility in the polishing
composition than cerium oxide (cf. later-described Examples 1 to 29
and Comparative Examples 4, 5). It can therefore be said that a
polishing composition according to the present embodiment also
contains an adhesive having good dispersibility.
[0036] The alkaline compound in the polishing composition acts to
accelerate mechanical polishing by silicon dioxide as well as to
chemically polish the glass substrate surface. By such actions of
the alkaline compound, the ability of the polishing composition to
polish the glass substrate improves, which leads to improvement in
stock removal rate. It should be noted that, while the alkaline
compound contributes to improvement in stock removal rate by means
of activation of the silicon dioxide surface and etching of the
glass substrate surface, it is not considered to act to oxidize the
glass substrate surface to be made brittle.
[0037] Next, examples and comparative examples of the present
invention will be described.
[0038] In each of Examples 1 to 29, an abrasive and an alkaline
compound were mixed with water, and thereafter, oxidizing agent was
further added thereto as necessary, so as to prepare a stock
solution of a polishing composition. In each of Comparative
Examples 1 to 5, an abrasive was mixed with water, and thereafter,
oxidizing agent was further added thereto as necessary, so as to
prepare a stock solution of a polishing composition. The kinds and
contents of abrasives, alkaline compounds, and oxidizing agents
used are as shown in Table 1.
[0039] Each stock solution according to Examples 1 to 29 and
Comparative examples 1 to 5 was diluted with ultrapure water, so
that the final volume could become 10 times the initial volume,
thereby preparing a polishing composition. Using the thus obtained
polishing composition according to each of Examples 1 to 29 and
Comparative examples 1 to 5, the surface of a glass substrate was
polished under the polishing conditions described below. Herein,
the mass of each glass substrate before and after polishing was
measured, and a stock removal rate was then calculated by the
below-mentioned formula. Based on the obtained stock removal rate,
each of the polishing compositions was rated on a scale from one to
four: (1) Very Good; (2) Good; (3) Slightly Poor; and (4) Poor.
Specifically, the polishing composition was rated very good when
the stock removal rate was not less than 0.05 .mu.m/minute; it was
rated good when the stock removal rate was not less than 0.03
.mu.m/minute and less than 0.05 .mu.m/minute; it was rated slightly
poor when the stock removal rate was not less than 0.02
.mu.m/minute and less than 0.03 .mu.m/minute; it was rated poor
when the stock removal rate was less than 0.02 .mu.m/minute. These
rating results are shown in the column entitled "Stock removal
rate" in Table 1.
[0040] Polishing Condition
[0041] Polishing machine: single-sided polishing machine 15".phi.
(3 pieces/plate), manufactured by Engis Corporation (Japan).
[0042] Material to be polished: 2.5-inch (external diameter: 3.5
mm) glass substrate obtained by roughly polishing the surface of
reinforced glass, using polishing slurry containing cerium oxide,
so as to have a surface roughness Ra of 0.8 nm.
[0043] Polishing pad: Suede type polishing pad "Belatrix N0058,"
manufactured by Kanebo, Ltd.
[0044] Polishing pressure: 100 g/cm.sup.2 (=9.8 kPa)
[0045] Turntable rotation speed: 102 rpm
[0046] Polishing composition supplied speed: 50 ml/minute
[0047] Polishing time: 20 minutes
[0048] Calculation Formula
Stock removal rate [.mu.m/minute]=(Difference in mass [g] of glass
substrate before/after polishing+(30.02625 [cm.sup.2].times.2.52
[g/cm.sup.3]).times.10000 [.mu.m/cm])+polishing time [minute]
[0049] The polished glass substrate was subjected to scrub cleaning
for 30 seconds and megasonic cleaning for 45 seconds, and then spin
drying for 180 seconds. Thereafter, the surface condition of the
glass substrate was observed with an atomic force microscope
"NanoScope IIIa Dimension 3000" (scan area: 10 .mu.m.times.10
.mu.m, scan rate: 1.00 Hz, sample lines: 256), manufactured by
Digital Instruments Inc. Based on the observed number of adherents
to the glass substrate surface, each of the polishing compositions
was rated on a scale from one to four: (1) Very Good; (2) Good; (3)
Slightly Poor; and (4) Poor. Specifically, the polishing
composition was rated very good when the observed number of
adherents to the glass substrate surface was zero; it was rated
good when the number of adherents was less than 3; it was rated
slightly poor when the number of adherents was not less than 3 and
less than 5; it was rated poor when the number of adherents was not
less than 5. These rating results are shown in the column entitled
"Ease of cleaning" in Table 1.
[0050] The surface roughness Ra of the glass substrate after spin
drying was measured with an atomic force microscope "NanoScope IIIa
Dimension 3000" (scan area: 10 .mu.m.times.10 .mu.m, scan rate:
1.00 Hz, sample lines: 256, off-line filter: flatten auto order-2).
Based on the measured surface roughness Ra of the glass substrate,
each of the polishing compositions was rated on a scale from one to
four: (1) Very Good; (2) Good; (3) Slightly Poor; and (4) Poor.
Specifically, the polishing composition was rated very good when
the surface roughness Ra was less than 0.2 nm; it was rated good
when the surface roughness Ra was not less than 0.2 nm and less
than 0.25 nm: it was rated slightly poor when the surface roughness
was not less than 0.25 nm and less than 0.3 nm; it was rated poor
when the surface roughness Ra was not less than 0.3 nm. These
rating results are shown in the column entitled "Surface roughness"
in Table 1.
[0051] Each of the polishing compositions according to Examples 1
to 29 and Comparative Examples 1 to 5 was put into a calorimetric
tube having an inner diameter of 2.5 cm, and allowed to stand there
for one hour. Thereafter, the height of a deposit produced in the
polishing composition in each colorimetric tube was measured. Based
on the measured height of the deposit, each of the polishing
compositions was rated on a scale from one to four: (1) Very Good;
(2) Good; (3) Slightly Poor; and (4) Poor. Specifically, the
polishing composition was rated very good when the height of the
deposit was less than 1 cm; it was rated good when the height of
the deposit was not less than 1 cm and less than 2 cm: it was rated
slightly poor when the height of the deposit was not less than 2 cm
and less than 3 cm; it was rated poor when the height of the
deposit was not less than 3 cm. Those rating results are shown in
the column entitled "Dispersibility" in Table 1.
[0052] Based on the above results of the ratings for the four
items: Stock removal rate, Ease of cleaning, Surface roughness, and
Dispersibility, each of the polishing compositions was
comprehensively rated on a scale from one to four: (1) Very Good;
(2) Good; (3) Slightly Poor; and (4) Poor. Specifically, 5 points,
3 points, 1 point and 0 point were given for Very Good, Good,
Slightly Poor and Poor, respectively, and the total rating points
obtained by each polishing composition was accordingly calculated.
A polishing composition was rated very good when the total rating
points for the four items was 20, it was rated good when the total
rating points was 16 to 19, it was rated slightly poor when the
total rating points was 10 to 15, and it was rated poor when the
total rating points was 9 or less. These rating results are shown
in the column entitled "Comprehensive rating" in Table 1.
1TABLE 1 Abrasive Alkaline compound Oxidizing agent Stock Ease of
Surface Comprehensive [mass percentage] [mass percentage] [mass
percentage] removal rate cleaning roughness Dispersibility rating
Ex. 1 colloidal silica*.sup.1 potassium carbonate hydrogen peroxide
1 1 1 1 1 25% 2% 2% Ex. 2 colloidal silica*.sup.1 potassium
carbonate hydrogen peroxide 1 1 1 1 1 25% 5% 2% Ex. 3 colloidal
silica*.sup.1 potassium carbonate hydrogen peroxide 2 1 1 1 2 25%
0.2% 2% Ex. 4 colloidal silica*.sup.1 potassium carbonate hydrogen
peroxide 3 1 1 1 2 25% 0.01% 2% Ex. 5 colloidal silica*.sup.1
potassium carbonate hydrogen peroxide 3 1 1 1 2 5% 2% 2% Ex. 6
colloidal silica*.sup.1 potassium carbonate hydrogen peroxide 2 1 1
1 2 10% 2% 2% Ex. 7 colloidal silica*.sup.1 potassium carbonate
hydrogen peroxide 1 1 1 1 1 40% 2% 2% Ex. 8 colloidal silica*.sup.1
potassium carbonate -- 2 1 1 1 2 25% 2% Ex. 9 colloidal
silica*.sup.1 potassium carbonate hydrogen peroxide 2 1 1 1 2 25%
2% 0.01% Ex. 10 colloidal silica*.sup.1 potassium carbonate
hydrogen peroxide 1 1 1 1 1 25% 2% 10% Ex. 11 fumed silica*.sup.1
potassium carbonate hydrogen peroxide 1 1 3 1 2 25% 2% 2% Ex. 12
colloidal silica*.sup.1 disodium hydrogen phosphate hydrogen
peroxide 1 1 1 1 1 25% 2% 2% Ex. 13 colloidal silica*.sup.1
trisodium phosphate hydrogen peroxide 1 1 1 1 1 25% 2% 2% Ex. 14
colloidal silica*.sup.1 potassium hydrogen carbonate hydrogen
peroxide 1 1 1 1 1 25% 2% 2% Ex. 15 colloidal silica*.sup.1
potassium hydroxide hydrogen peroxide 2 1 1 1 2 25% 2% 2% Ex. 16
colloidal silica*.sup.1 potassium sodium tartrate hydrogen peroxide
2 1 1 1 2 25% 2% 2% Ex. 17 colloidal silica*.sup.1 tripotassium
phosphate hydrogen peroxide 2 1 1 1 2 25% 2% 2% Ex. 18 colloidal
silica*.sup.1 potassium pyrophosphate hydrogen peroxide 2 1 1 1 2
25% 2% 2% Ex. 19 colloidal silica*.sup.1 tripotassium citrate
hydrogen peroxide 2 1 1 1 2 25% 2% 2% Ex. 20 colloidal
silica*.sup.1 lithium hydroxide hydrogen peroxide 2 1 1 1 2 25% 2%
2% Ex. 21 colloidal silica*.sup.1 sodium hydroxide hydrogen
peroxide 2 1 1 1 2 25% 2% 2% Ex. 22 colloidal silica*.sup.1
ammonium hydroxide hydrogen peroxide 3 1 1 1 2 25% 2% 2% Ex. 23
colloidal silica*.sup.1 TMAH hydrogen peroxide 3 1 1 1 2 25% 2% 2%
Ex. 24 colloidal silica*.sup.1 calcium nitrate hydrogen peroxide 3
1 1 1 2 25% 2% 2% Ex. 25 colloidal silica*.sup.1 potassium
carbonate hydrogen peroxide 2 1 1 1 2 25% 2% 2% Ex. 26 colloidal
silica*.sup.1 potassium carbonate sodium perchlorate 2 1 1 1 2 25%
2% 2% Ex. 27 colloidal silica*.sup.1 potassium carbonate sodium
bromate 2 1 1 1 2 25% 2% 2% Ex. 28 colloidal silica*.sup.2
potassium carbonate hydrogen peroxide 2 1 1 1 2 25% 2% 2% Ex. 29
fumed silica*.sup.2 potassium carbonate hydrogen peroxide 1 1 3 1 2
25% 2% 2% C. Ex. 1 colloidal silica*.sup.1 -- -- 4 1 1 1 3 25% C.
Ex. 2 colloidal silica*.sup.1 -- hydrogen peroxide 4 1 1 1 3 25% 2%
C. Ex. 3 fumed silica*.sup.1 -- -- 2 1 3 1 3 25% C. Ex. 4 cerium
oxide -- -- 1 4 4 4 4 25% C. Ex. 5 iron oxide -- -- 2 3 3 4 4
25%
[0053] In the "Abrasive" column in Table 1:
[0054] "colloidal silica.sup.*1" is colloidal silica having a mean
particle size D.sub.SA of 80 nm and a mean particle size D.sub.N4
of 80 nm;
[0055] "colloidal silica.sup.*2" is colloidal silica having a mean
particle size D.sub.SA of 20 nm and a mean particle size D.sub.N4
of 40 nm;
[0056] "fumed silica.sup.*1" is fumed silica having a mean particle
size D.sub.SA of 30 nm and a mean particle size D.sub.N4 of 170
nm;
[0057] "fumed silica.sup.*2" is fumed silica having a mean particle
size D.sub.SA of 20 nm and a mean particle size D.sub.N4 of 140
nm;
[0058] "cerium oxide" is cerium oxide (Ce.sub.2O.sub.3) having a
mean particle size D.sub.50 of 450 nm; and
[0059] "iron oxide" is iron oxide (.alpha.-Fe.sub.2O.sub.3) having
a mean particle size D.sub.50 of 450 nm.
[0060] The mean particle size D.sub.50 of cerium oxide and iron
oxide were measured using a Coulter counter "LS-230", manufactured
by Beckman Coulter Inc.
[0061] In the "Oxidizing agent" column in Table 1, "hydrogen
peroxide" is aqueous solution of hydrogen peroxide (31 mass %).
[0062] As shown in Table 1, each of the polishing compositions
according to Examples 1 to 29 was not rated as poor for any rating
item, and was rated as either very good or good for the
"Comprehensive rating". This result suggests that the polishing
compositions according to Examples 1 to 29 are useful in
applications for polishing a glass substrate. It was found from the
rating results of the polishing compositions according to Examples
1 and 5 to 7 that the stock removal rate improves, in particular,
by setting the content of silicon dioxide (abrasive) to not less
than 25 mass %, and more specifically in the range of 25 to 40 mass
%. It was also found from the rating results of the polishing
compositions according to Examples 1 to 4 that the stock removal
rate improves, in particular, by setting the content of alkaline
compound to not less than 2 mass %, and more specifically in the
range of 2 to 5 mass %. It was further found from the rating
results of the polishing compositions according to Examples 1, 9,
and 10 that the stock removal rate improves, in particular, by
setting the content of the acid to not less than 2 mass %, and more
specifically in the range of 2 to 10 mass %.
[0063] The present examples and embodiments are to be considered as
illustrative and not restrictive and the invention is not to be
limited to the details given herein, but may be modified within the
scope and equivalence of the appended claims.
* * * * *