U.S. patent application number 10/980446 was filed with the patent office on 2005-06-23 for polishing composition and polishing method.
Invention is credited to Ohashi, Keigo, Owaki, Toshiki.
Application Number | 20050136803 10/980446 |
Document ID | / |
Family ID | 34674788 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050136803 |
Kind Code |
A1 |
Ohashi, Keigo ; et
al. |
June 23, 2005 |
Polishing composition and polishing method
Abstract
A polishing composition of the present invention contains
silicon dioxide, an acid, and water. Silicon dioxide is, for
example, colloidal silica, fumed silica, or precipitated silica.
The acid is, for example, hydrochloric acid, phosphoric acid,
sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric
acid, acetic acid, itaconic acid, succinic acid, tartaric acid,
citric acid, maleic acid, glycolic acid, malonic acid,
methanesulfonic acid, formic acid, malic acid, gluconic acid,
alanine, glycin, lactic acid, hydroxyethylidene diphosphonic acid,
nitrilotris(methylene phosphonic acid), or phosphonobutane
tricarboxylic acid. The pH of the polishing composition is
preferably in the range of 0.5 to 6. 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: |
34674788 |
Appl. No.: |
10/980446 |
Filed: |
November 3, 2004 |
Current U.S.
Class: |
451/41 ;
51/309 |
Current CPC
Class: |
C03C 19/00 20130101;
G11B 5/8404 20130101 |
Class at
Publication: |
451/041 ;
051/309 |
International
Class: |
B24B 001/00; B24D
003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2003 |
JP |
(PAT.)2003-374664 |
Claims
1. A polishing composition for use in an application for polishing
a glass substrate, the polishing composition comprising silicon
dioxide, an acid, 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
acid is hydrochloric acid, phosphoric acid, sulfuric acid,
phosphonic acid, nitric acid, phosphinic acid, or boric acid.
11. The polishing composition according to claim 1, wherein the
acid is acetic acid, itaconic acid, succinic acid, tartaric acid,
citric acid, maleic acid, glycolic acid, malonic acid,
methanesulfonic acid, formic acid, malic acid, gluconic acid,
alanine, glycin, lactic acid, hydroxyethylidene diphosphonic acid,
nitrilotris(methylene phosphonic acid), or phosphonobutane
tricarboxylic acid.
12. The polishing composition according to claim 1, wherein the
content of the acid in the polishing composition is 0.05 to 10 mass
%.
13. The polishing composition according to claim 12, wherein the
content of the acid in the polishing composition is 0.3 to 5 mass
%.
14. The polishing composition according to claim 1, wherein the pH
of the polishing composition is 0.5 to 6.
15. The polishing composition according to claim 14, wherein the pH
of the polishing composition is 1 to 2.5.
16. The polishing composition according to claim 1, further
comprising a chelating agent, a surfactant, or a preservative.
17. A method for polishing a glass substrate, the method
comprising: preparing a polishing composition comprising silicon
dioxide, an acid, and water; and polishing the surface of a glass
substrate, using the prepared polishing composition.
18. The method for polishing a glass substrate according to claim
17, 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.
19. The method for polishing a glass substrate according to claim
17, wherein said preparing a polishing composition comprises
diluting the polishing composition with water.
20. The method for polishing a glass substrate according to claim
19, wherein the volume of water to be used for dilution of the
polishing composition is not more than 50 times as large as the
volume of the polishing composition before dilution.
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, a polishing
composition is provided. The polishing composition, for use in
applications for polishing a glass substrate, contains silicon
dioxide, an acid, and water.
[0011] The present 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 acid, 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 acid serves as a polishing accelerator for accelerating
mechanical polishing by silicon dioxide. The reason why the acid
accelerates mechanical polishing is presumably that the acid acts
on the surface of silicon dioxide for activation, thereby
increasing the mechanical polishing force of silicon dioxide. The
acid 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 acid is weaker than the
mechanical polishing action of silicon dioxide. The acid may be an
inorganic acid or an organic acid.
[0021] Examples of the inorganic acid may include hydrochloric
acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid,
phosphinic acid, and boric acid. Examples of the organic acid may
include acetic acid, itaconic acid, succinic acid, tartaric acid,
citric acid, maleic acid, glycolic acid, malonic acid,
methanesulfonic acid, formic acid, malic acid, gluconic acid,
alanine, glycin, lactic acid, hydroxyethylidene diphosphonic acid
(abbreviation: HEDP), nitrilotris(methylene phosphonic acid)
(abbreviation: NTMP), and phosphonobutane tricarboxylic acid
(abbreviation: PBTC). Among them, hydrochloric acid, phosphoric
acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid,
acetic acid, itaconic acid, succinic acid, tartaric acid, citric
acid, maleic acid, glycolic acid, malonic acid, methanesulfonic
acid, formic acid, malic acid, gluconic acid, lactic acid, HEDP,
NTMP, or PBTC is preferable, since these acids strongly act to
accelerate mechanical polishing by silicon dioxide. Among these
preferable acids, hydrochloric acid, phosphoric acid, phosphonic
acid, tartaric acid, citric acid, maleic acid, or malonic acid is
more preferable. One or more acids may be contained in the
polishing composition.
[0022] The content of the acid 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 acid is less than 0.05
mass %, it is highly possible that a sufficiently high stock
removal fate will not be obtained because the acid weakly acts to
accelerate mechanical polishing by silicon dioxide. When the
content of the acid 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.
[0023] 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.
[0024] The polishing composition may further contain a chelating
agent, a surfactant, a preservative, or the like according to
need.
[0025] 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.
[0026] The pH of the polishing composition is preferably not more
than 9, more preferably in the range of 0.5 to 6, further more
preferably in the range of 1 to 4, and most preferably in the range
of 1 to 2.5. When the pH is higher than 9, it is highly possible
that a sufficiently high stock removal rate will not be obtained.
When the pH is lower than 0.5, it is highly possible that the
handleability of the polishing composition will deteriorate. When
the pH of the polishing composition is set to the range of 0.5 to
6, the polishing composition is highly capable of polishing a glass
substrate, thereby to improve the stock removal rate. The pH of the
polishing composition is adjustable by changing the content of the
acid.
[0027] 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 acid in the polishing
composition after dilution might become excessively low, resulting
in failure to obtain a sufficiently high stock removal rate.
[0028] 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.
[0029] 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.
[0030] The present embodiment has the following advantages.
[0031] 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.
[0032] 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.
[0033] Furthermore, silicon dioxide has greater resistance to
agglomeration and higher dispersibility in the polishing
composition than cerium oxide (cf. later-described Examples 1 to 37
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.
[0034] The acid 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 acid,
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 acid 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.
[0035] Next, examples and comparative examples of the present
invention will be described.
[0036] An abrasive and a polishing accelerator were mixed with
water to prepare polishing compositions according to Examples 1 to
37 and Comparative Examples 1 to 5. The kinds of abrasives and
polishing accelerators used are as shown in Table 1. The pH of each
of the prepared polishing compositions according to Examples 1 to
37 and Comparative Examples 1 to 5 was measured, and the
measurement results are shown in Table 1.
[0037] The surface of a glass substrate was polished using each of
the polishing compositions according to Examples 1 to 37 and
Comparative Examples 1 to 5 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 0.12
.mu.m/minute; it was rated good when the stock removal rate was not
less than 0.08 .mu.m/minute and less than 0.12 .mu.m/minute; it was
rated slightly poor when the stock removal rate was not less than
0.05 .mu.m/minute and less than 0.08 .mu.m/minute; it was rated
poor when the stock removal rate was less than 0.05 .mu.m/minute.
These rating results are shown in the column entitled "Stock
removal rate" in Table 1.
[0038] <Polishing Condition>
[0039] Polishing machine: single-sided polishing machine 15".phi.
(3 pieces/plate), manufactured by Engis Corporation (Japan).
[0040] Material to be polished: 2.5-inch (external diameter: 63.5
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.
[0041] Polishing pad: Suede type polishing pad "Belatrix N0058,"
manufactured by Kanebo, Ltd.
[0042] Polishing pressure: 100 g/cm.sup.2 (=9.8 kPa)
[0043] Turntable rotation speed: 102 rpm
[0044] Polishing composition supplied speed: 50 ml/minute
[0045] Polishing time: 20 minutes
[0046] <Calculation Formula>
Stock removal rate [.mu.m/minute]=(Difference in mass [g] of glass
substrate before/after polishing.div.(30.02625
[cm.sup.2].times.2.52 [g/cm.sup.3]).times.10000
[.mu.m/cm]).div.polishing time [minute]
[0047] 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" column in Table 1.
[0048] 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.
[0049] Each of the polishing compositions according to Examples 1
to 37 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 calorimetric 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.
[0050] 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 Polishing Stock Abrasive accelerator removal Ease of
Surface Comprehensive [mass percentage] [mass percentage] pH rate
cleaning roughness Dispersibility rating Ex. 1 colloidal silica
maleic acid 1.3 1 1 1 1 1 20% 3% Ex. 2 colloidal silica maleic acid
1.6 1 1 1 1 1 20% 1% Ex. 3 colloidal silica maleic acid 2.2 1 1 1 1
1 20% 0.1% Ex. 4 colloidal silica maleic acid 5.0 2 1 1 1 2 20%
0.04% Ex. 5 colloidal silica maleic acid 8.5 3 1 1 1 2 20% 0.01%
Ex. 6 colloidal silica maleic acid 1.5 1 1 1 1 1 10% 1% Ex. 7
colloidal silica maleic acid 1.4 3 1 1 1 2 1% 1% Ex. 8 fumed silica
maleic acid 1.7 1 1 3 1 2 20% 1% Ex. 9 colloidal silica maleic acid
2.6 1 1 1 1 1 40% 1% Ex. 10 colloidal silica phosphoric acid 1.6 1
1 1 1 1 20% 3% Ex. 11 colloidal silica phosphoric acid 1.9 1 1 1 1
1 20% 1% Ex. 12 colloidal silica phosphoric acid 2.5 1 1 1 1 1 20%
0.1% Ex. 13 colloidal silica phosphoric acid 9.0 3 1 1 1 2 20%
0.01% Ex. 14 colloidal silica phosphoric acid 1.7 2 1 1 1 2 10% 1%
Ex. 15 colloidal silica phosphoric acid 1.7 3 1 1 1 2 1% 1% Ex. 16
fumed silica phosphoric acid 1.9 1 1 3 1 2 20% 1% Ex. 17 colloidal
silica phosphoric acid 2.8 1 1 1 1 1 40% 1% Ex. 18 colloidal silica
methanesulfonic acid 1.1 1 1 1 1 1 20% 1% Ex. 19 colloidal silica
HEDP 1.4 1 1 1 1 1 20% 1% Ex. 20 colloidal silica NTMP 1.4 1 1 1 1
1 20% 1% Ex. 21 colloidal silica hydrochloric acid 1.4 1 1 1 1 1
20% 1% Ex. 22 colloidal silica PBTC 1.5 1 1 1 1 1 20% 1% Ex. 23
colloidal silica maleic acid 1.5 1 1 1 1 1 20% 1% Ex. 24 colloidal
silica phosphinic acid 1.7 1 1 1 1 1 20% 1% Ex. 25 colloidal silica
tartaric acid 2.1 1 1 1 1 1 20% 1% Ex. 26 colloidal silica malonic
acid 2.2 1 1 1 1 1 20% 1% Ex. 27 colloidal silica citric acid 2.4 1
1 1 1 1 20% 1% Ex. 28 colloidal silica malic acid 2.4 1 1 1 1 1 20%
1% Ex. 29 colloidal silica formic acid 2.6 1 1 1 1 1 20% 1% Ex. 30
colloidal silica glycolic acid 2.8 1 1 1 1 1 20% 1% Ex. 31
colloidal silica itaconic acid 2.9 1 1 1 1 1 20% 1% Ex. 32
colloidal silica gluconic acid 2.9 1 1 1 1 1 20% 1% Ex. 33
colloidal silica succinic acid 3.2 1 1 1 1 1 20% 1% Ex. 34
colloidal silica acetic acid 3.8 2 1 1 1 2 20% 1% Ex. 35 colloidal
silica boric acid 7.8 2 1 1 1 2 20% 1% Ex. 36 colloidal silica
alanine 8.6 2 1 1 1 2 20% 1% Ex. 37 colloidal silica glycin 8.6 2 1
1 1 2 20% 1% C. Ex. 1 colloidal silica -- 10.3 4 1 1 1 3 20% C. Ex.
2 colloidal silica aluminum nitrate 3.4 4 1 1 1 3 25% 1% C. Ex. 3
colloidal silica ammonium molybdate 5.4 4 1 1 1 3 20% 1% C. Ex. 4
cerium oxide -- 6.9 1 4 3 4 4 25% C. Ex. 5 iron oxide -- 6.9 2 3 3
4 4 25% In the "Abrasive" column in Table 1: "Colloidal silica" 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; "Fumed silica" is fumed
silica having a mean particle size D.sub.SA of 30 nm and a mean
particle size D.sub.N4 of 90 nm; "Cerium oxide" is cerium oxide
(Ce.sub.2O.sub.3) having a mean particle size D.sub.50 of 450 nm;
and "Iron oxide" is iron oxide (.alpha.-Fe.sub.2O.sub.3) having a
mean particle diameter D.sub.50 of 450 nm. The mean particle
diameters D.sub.50 of cerium oxide and iron oxide were measured
using a Coulter counter "LS-230", manufactured by Beckman Coulter
Inc.
[0051] As shown in Table 1, each of the polishing compositions
according to Examples 1 to 37 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 37 are useful in
applications for polishing a glass substrate. It was found from the
rating results of the polishing compositions according to Examples
2, 6, 7 and 9 that, when the acid (polishing accelerator) is maleic
acid, an organic acid, the stock removal rate improves, in
particular, by setting the content of silicon dioxide (abrasive) to
not less than 10 mass %, and more specifically in the range of 10
to 40 mass %. It was also found from the rating results of the
polishing compositions according to Examples 11, 14, 15 and 17
that, when the acid is phosphoric acid, an inorganic acid, the
stock removal rate improves, in particular, by setting the content
of silicon dioxide to not less than 20 mass %, and more
specifically in the range of 20 to 40 mass %. It was further found
from the rating results of the polishing compositions according to
Examples 1 to 5 and 10 to 13 that the stock removal rate improves,
in particular, by setting the content of the acid to not less than
0.1 mass %, and more specifically in the range of 0.1 to 3 mass
%.
[0052] 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.
* * * * *