U.S. patent application number 14/314922 was filed with the patent office on 2014-10-16 for glass substrate for flat panel display.
This patent application is currently assigned to AvanStrate Inc.. The applicant listed for this patent is AvanStrate Inc.. Invention is credited to Satoshi AMI, Manabu ICHIKAWA, Akihiro KOYAMA.
Application Number | 20140309098 14/314922 |
Document ID | / |
Family ID | 47436766 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140309098 |
Kind Code |
A1 |
KOYAMA; Akihiro ; et
al. |
October 16, 2014 |
GLASS SUBSTRATE FOR FLAT PANEL DISPLAY
Abstract
A flat panel display glass substrate includes a glass
comprising, in mol %, 55-80% SiO.sub.2, 3-20% Al.sub.2O.sub.3,
3-15% B.sub.2O.sub.3, and 3-25% RO (the total amount of MgO, CaO,
SrO, and BaO). The contents in mol % of SiO.sub.2, Al.sub.2O.sub.3,
and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17. The strain
point of the glass is 665.degree. C. or more. The devitrification
temperature of the glass is 1250.degree. C. or less. The substrate
has a heat shrinkage rate of 75 ppm or less. The rate of heat
shrinkage is calculated from the amount of shrinkage of the
substrate measured after a heat treatment which is performed at a
rising and falling temperature rate of 10.degree. C./min and at
550.degree. C. for 2 hours by the rate of heat shrinkage (ppm)={the
amount of shrinkage of the substrate after the heat treatment/the
length of the substrate before the heat
treatment}.times.10.sup.6.
Inventors: |
KOYAMA; Akihiro;
(Takarazuka-shi, JP) ; AMI; Satoshi;
(Yokkaichi-shi, JP) ; ICHIKAWA; Manabu;
(Yokkaichi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AvanStrate Inc. |
Yokkaichi-shi |
|
JP |
|
|
Assignee: |
AvanStrate Inc.
Yokkaichi-shi
JP
|
Family ID: |
47436766 |
Appl. No.: |
14/314922 |
Filed: |
June 25, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13537615 |
Jun 29, 2012 |
|
|
|
14314922 |
|
|
|
|
61513205 |
Jul 29, 2011 |
|
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Current U.S.
Class: |
501/66 |
Current CPC
Class: |
C03B 25/00 20130101;
C03C 3/066 20130101; G02F 2001/133302 20130101; C03B 17/06
20130101; C03C 3/064 20130101; C03C 3/091 20130101; C03B 17/064
20130101; C03B 17/00 20130101; C03C 3/093 20130101 |
Class at
Publication: |
501/66 |
International
Class: |
C03C 3/091 20060101
C03C003/091 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 1, 2011 |
JP |
2011-147758 |
Mar 15, 2012 |
JP |
2012-059132 |
Claims
1. A flat panel display glass substrate on which a p-Si TFT can be
formed, the flat panel display glass substrate comprising a glass
comprising, as expressed in mol %: 55-80% SiO.sub.2; 3-20%
Al.sub.2O.sub.3; 3-15% B.sub.2O.sub.3; and 3-25% RO, where RO
represents the total amount of MgO, CaO, SrO, and BaO, wherein in
the glass, the contents in mol % of SiO.sub.2, Al.sub.2O.sub.3, and
B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17, the strain
point of the glass is 665.degree. C. or more, the devitrification
temperature of the glass is 1250.degree. C. or less, the glass
substrate has a rate of heat shrinkage of 75 ppm or less, and the
rate of heat shrinkage is calculated from the amount of shrinkage
of the glass substrate measured after a heat treatment which is
performed at a rising and falling temperature rate of 10.degree.
C./min and at 550.degree. C. for 2 hours by; the rate of heat
shrinkage (ppm)={the amount of shrinkage of the glass substrate
after the heat treatment/the length of the glass substrate before
the heat treatment}.times.10.sup.6.
2. A flat panel display glass substrate on which a p-Si TFT can be
formed, the flat panel display glass substrate comprising a glass
comprising, as expressed in mol %; 55-80% SiO.sub.2; 3-20%
Al.sub.2O.sub.3; 3-15% B.sub.2O.sub.3; and 3-25% RO, where RO
represents the total amount of MgO, CaO, SrO, and BaO, wherein in
the glass the contents in mol % of SiO.sub.2, Al.sub.2O.sub.3, and
B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, the
devitrification temperature of the glass is 1250.degree. C. or
less, the glass substrate has a rate of heat shrinkage of 60 ppm or
less, and the rate of heat shrinkage is calculated from the amount
of shrinkage of the glass substrate measured after a heat treatment
which is performed at a rising and falling temperature rate of
10.degree. C./min and at 550.degree. C. for 2 hours by: the rate of
heat shrinkage (ppm)={the amount of shrinkage of the glass
substrate after the heat treatment/the length of the glass
substrate before the heat treatment}.times.10.sup.6.
3. The flat panel display glass substrate according to claim 1,
wherein the glass contains, as expressed in mol %, 0-5% ZnO, in the
glass, the contents in mol % of SiO.sub.2 and Al.sub.2O.sub.3
satisfy SiO.sub.2+Al.sub.2O.sub.3.gtoreq.75%, and the contents in
mol % of RO, ZnO, and B.sub.2O.sub.3 satisfy
RO+ZnO+B.sub.2O.sub.3=7-25%.
4. The flat panel display glass substrate according to claim 2,
wherein the glass comprises, as expressed in mol %, 0-5% ZnO, in
the glass, the contents in mol % of SiO.sub.2 and Al.sub.2O.sub.3
satisfy SiO.sub.2+Al.sub.2O.sub.3.gtoreq.75%, and the contents in
mol % of RO, ZnO, and B.sub.2O.sub.3 satisfy
RO+ZnO+B.sub.2O.sub.3=7-25%.
5. The flat panel display glass substrate according to claim 1,
wherein in the glass, the sum of the MgO, CaO, SrO, and BaO
contents is 4-20 mol %.
6. The flat panel display glass substrate according to claim 2,
wherein in the glass, the sum of the MgO, CaO, SrO, and BaO
contents is 4-20 mol %.
7. The flat panel display glass substrate according to claim 1,
wherein in the glass, the ratio of the CaO content to the sum of
the MgO, CaO, SrO, and BaO contents in mol % is more than 0.5.
8. The flat panel display glass substrate according to claim 2,
wherein in the glass, the ratio of the CaO content to the sum of
the MgO, CaO, SrO, and BaO contents in mol % is more than 0.5.
9. The flat panel display glass substrate according to claim 1,
wherein the liquidus viscosity of the glass is 10.sup.4.5 dPas or
more, and the flat panel display glass substrate is obtained by
forming the glass using a downdraw process.
10. The flat panel display glass substrate according to claim 2,
wherein the liquidus viscosity of the glass is 10.sup.4.5 dPas or
more, and the flat panel display glass substrate is obtained by
forming the glass using a downdraw process.
11. The flat panel display glass substrate according to claim 1,
wherein the glass comprises substantially no As.sub.2O.sub.3 or
Sb.sub.2O.sub.3.
12. The flat panel display glass substrate according to claim 2,
wherein the glass comprises substantially no As.sub.2O.sub.3 or
Sb.sub.2O.sub.3.
13. The flat panel display glass substrate according to claim 1,
wherein the flat panel display glass substrate is a liquid crystal
display glass substrate.
14. The flat panel display glass substrate according to claim 2,
wherein the flat panel display glass substrate is a liquid crystal
display glass substrate.
15. A flat panel display glass substrate comprising a glass
comprising, as expressed in mol %: 55-80% SiO.sub.2; 3-20%
Al.sub.2O.sub.3; 3-15% B.sub.2O.sub.3; and 3-25% RO, where RO
represents the total amount of MgO, CaO, SrO, and BaO, wherein in
the glass, the contents in mol % of SiO.sub.2, Al.sub.2O.sub.3, and
B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17, the strain
point of the glass is 665.degree. C. or more, the devitrification
temperature of the glass is 1250.degree. C. or less, the glass
substrate has a rate of heat shrinkage of 75 ppm or less, and the
rate of heat shrinkage is calculated from the amount of shrinkage
of the glass substrate measured after a heat treatment which is
performed at a rising and falling temperature rate of 10.degree.
C./min and at 550.degree. C. for 2 hours by: the rate of heat
shrinkage (ppm)={the amount of shrinkage of the glass substrate
after the heat treatment/the length of the glass substrate before
the heat treatment}.times.10.sup.6.
16. A flat panel display glass substrate comprising a glass
comprising, as expressed in mol %: 55-80% SiO.sub.2; 3-20%
Al.sub.2O.sub.3; 3-15% B.sub.2O.sub.3; and 3-25% RO, where RO
represents the total amount of MgO, CaO, SrO, and BaO, wherein in
the glass, the contents in mol % of SiO.sub.2, Al.sub.2O.sub.3, and
B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, the
devitrification temperature of the glass is 1250.degree. C. or
less, the glass substrate has a rate of heat shrinkage of 60 ppm or
less, and the rate of heat shrinkage is calculated from the amount
of shrinkage of the glass substrate measured after a heat treatment
which is performed at a rising and falling temperature rate of
10.degree. C./min and at 550.degree. C. for 2 hours by: the rate of
heat shrinkage (ppm)={the amount of shrinkage of the glass
substrate after the heat treatment/the length of the glass
substrate before the heat treatment}.times.10.sup.6.
17. A flat panel display glass substrate on which a p-Si TFT can be
formed, the flat panel display glass substrate comprising a glass
comprising, as expressed in mol %: 55-80% SiO.sub.2; 3-20%
Al.sub.2O.sub.3; 3-15% B.sub.2O.sub.3; and 3-25% RO, where RO
represents the total amount of MgO, CaO, SrO, and BaO, wherein in
the glass, the contents in mol % of SiO.sub.2, Al.sub.2O.sub.3, and
B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17, the strain
point of the glass is 665.degree. C. or more, the devitrification
temperature of the glass is 1250.degree. C. or less, and the glass
substrate has a rate of heat shrinkage of 75 ppm or less after a
heat treatment in which the glass substrate is kept at Tg for 30
min, then cooled at a rate of 100.degree. C./min until the
temperature thereof reaches Tg-100.degree. C., then cooled until
the temperature reaches room temperature, and then kept at
550.degree. C. for 2 hours, wherein a rising and falling
temperature rate is 10.degree. C./min.
Description
[0001] This application is a Divisional of U.S. application Ser.
No. 13/537,615, filed Jun. 29, 2012, which claims priority to
Provisional U.S. Application No. 61/513,205 filed Jul. 29, 2011;
which claims priority to Japanese Application No. 2011-147758,
filed Jul. 1, 2011 and JP 2012-059132 filed Mar. 15, 2012, the
disclosure of each is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to glass substrates for flat
panel displays and methods for manufacturing the glass
substrates.
[0004] 2. Related Background Art
[0005] Flat panel displays with small thickness and low power
consumption, such as a thin film transistor (TFT) liquid crystal
display and an organic electroluminescence (EL) display, have in
recent years been employed as displays for mobile devices and the
like. These displays typically include a glass substrate.
[0006] There are the following types of TFTs: an amorphous silicon
(.alpha.-Si) TFT; and a polysilicon (p-Si) TFT. The p-Si TFT is
advantageous over the .alpha.-Si TFT in terms of screen resolution,
display durability, display thickness and weight, and power
consumption, and the like, i.e., the p-Si TFT can provide a
beautiful screen with a higher resolution, a display with a higher
durability, a display with a smaller thickness and a lower weight,
and lower power consumption. Conventionally, however, a high
temperature treatment is required in production of the p-Si TFT.
Therefore, the glass substrate undergoes heat shrinkage and heat
shock during production of the p-Si TFT, and therefore, glass other
than silica glass cannot be employed. As a result, it is difficult
to apply the p-Si TFT to a liquid crystal display.
[0007] However, the low-temperature polysilicon (LTPS) TFT, for
which the heat treatment is performed at lower temperature, has in
recent years been developed, and therefore, the p-Si TFT has been
applicable to the flat panel display. As a result, the display of a
small device (e.g., a mobile device, etc.) can have a beautiful
screen with a high resolution.
[0008] Note that the heat treatment in production of the p-Si TFT
still requires a temperature of as high as 400 to 600.degree. C.
Most of the conventional glass substrates for displays do not have
a sufficiently high strain point, and therefore, are likely to
undergo significant heat shrinkage due to the heat treatment in
production of the p-Si TFT, leading to a non-uniform pixel pitch.
Moreover, in recent years, there has been a demand for higher and
higher resolutions. Therefore, in order to reduce such a
non-uniform pixel pitch, it is highly desirable to reduce the heat
shrinkage of the glass substrate during production of the display.
Conventionally, glass substrates for displays which have been
developed in view of the heat shrinkage problem have been reported
(JP 2002-3240A, JP 2004-315354A, and JP 2007-302550A).
SUMMARY OF THE INVENTION
[0009] Here, the heat shrinkage of the glass substrate can be
reduced by increasing characteristic (low-temperature viscosity
characteristic) temperatures in the low temperature viscosity
range, typified by a glass transition temperature (hereinafter
referred to as a "Tg") and a strain point (the "Tg and strain
point" will be described hereinafter as typical examples of the
low-temperature viscosity characteristic temperature in this
specification). However, if the composition of a glass is modified
only for the purpose of increasing the Tg and strain point of the
glass, the devitrification resistance of the glass is likely to
deteriorate. If the devitrification resistance deteriorates, i.e.,
the devitrification temperature increases, so that the liquidus
viscosity decreases, the flexibility of the production method also
decreases. If the devitrification temperature increases, so that
the liquidus viscosity decreases, it is difficult to produce the
glass substrate, for example, by the overflow downdraw process.
[0010] Therefore, it is an object of the present invention to
provide a glass substrate for flat panel displays which
simultaneously has a high Tg and strain point and good
devitrification resistance and in which a non-uniform pixel pitch
does not occur even if the glass substrate is used in a display to
which the p-Si TFT is applied.
[0011] A first example flat panel display glass substrate on which
a p-Si TFT can be formed according to the present invention
includes a glass comprising, as expressed in mol %:
[0012] 55-80% SiO.sub.2;
[0013] 3-20% Al.sub.2O.sub.3;
[0014] 3-15% B.sub.2O.sub.3; and
[0015] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0016] in the glass, the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17,
[0017] the strain point of the glass is 665.degree. C. or more,
and
[0018] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0019] the glass substrate has a heat shrinkage rate of 75 ppm or
less.
[0020] The ratio of heat shrinkage is calculated from the amount of
shrinkage of the glass substrate measured after a heat treatment
which is performed at a rising and falling temperature rate of
10.degree. C./min and at 550.degree. C. for 2 hours by:
the ratio of heat shrinkage (ppm)={the amount of shrinkage of the
glass substrate after the heat treatment/the length of the glass
substrate before the heat treatment}.times.10.sup.6
[0021] The "ratio of heat shrinkage" as used hereinafter has the
same meaning.
[0022] A second example flat panel display glass substrate on which
a p-Si TFT can be formed according to the present invention
includes a glass comprising, as expressed in mol %;
[0023] 55-80% SiO.sub.2;
[0024] 3-20% Al.sub.2O.sub.3;
[0025] 3-15% B.sub.2O.sub.3; and
[0026] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0027] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, and
[0028] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0029] the glass substrate has a heat shrinkage rate of 60 ppm or
less.
[0030] According to a third aspect of the present invention, a flat
panel display glass substrate on which a p-Si TFT can be formed
includes a glass comprising, as expressed in mol %;
[0031] 55-80% SiO.sub.2;
[0032] 3-20% Al.sub.2O.sub.3;
[0033] 3-15% B.sub.2O.sub.3; and
[0034] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0035] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17,
[0036] the strain point of the glass is 665.degree. C. or more,
and
[0037] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0038] the glass substrate has a heat shrinkage rate of 75 ppm or
less after a heat treatment in which the glass substrate is kept at
Tg for 30 min, then cooled at a rate of 100.degree. C./min until
the temperature thereof reaches Tg-100.degree. C., then cooled
until the temperature reaches room temperature, and then kept at
550.degree. C. for 2 hours, wherein a rising and falling
temperature rate is 10.degree. C./min.
[0039] A first example method for manufacturing a flat panel
display glass substrate on which a p-Si TFT can be formed according
to the present invention, includes:
[0040] a melting step of melting a glass material for a glass
comprising, as expressed in mol %, 55-80% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, and 3-25% RO (the total
amount of MgO, CaO, SrO, and BaO), with the contents in mol % of
SiO.sub.2, Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfying a
relationship (SiO.sub.2+Al.sub.2O.sub.3)(B.sub.2O.sub.3)=7.5-17,
the strain point of the glass being 665.degree. C. or more, and the
devitrification temperature of the glass being 1250.degree. C. or
less, to produce a molten glass;
[0041] a forming step of forming the molten glass into a glass
plate; and
[0042] an annealing step of annealing the glass plate,
where
[0043] the glass plate has a heat shrinkage rate of 75 ppm or
less.
[0044] A second example method for manufacturing a flat panel
display glass substrate on which a p-Si TFT can be formed according
to the present invention, includes:
[0045] a melting step of melting a glass material for a glass
comprising, as expressed in mol %, 55-80% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, and 3-25% RO (the total
amount of MgO, CaO, SrO, and BaO), with the contents in mol % of
SiO.sub.2, Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfying a
relationship (SiO.sub.2+Al.sub.2O.sub.3)(B.sub.2O.sub.3)=8.45-17.0
and the devitrification temperature of the glass being 1250.degree.
C. or less, to produce a molten glass,
[0046] a forming step of forming the molten glass into a glass
plate, and
[0047] an annealing step of annealing the glass plate,
wherein
[0048] the glass plate has a heat shrinkage rate of 60 ppm or
less.
[0049] A first example flat panel display glass substrate according
to the present invention includes a glass comprising, as expressed
in mol %;
[0050] 55-80% SiO.sub.2;
[0051] 3-20% Al.sub.2O.sub.3;
[0052] 3-15% B.sub.2O.sub.3; and
[0053] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0054] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17,
[0055] the strain point of the glass is 665.degree. C. or more,
and
[0056] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0057] the glass substrate has a heat shrinkage rate of 75 ppm or
less.
[0058] A second flat panel display glass substrate according to the
present invention includes a glass comprising, as expressed in mol
%;
[0059] 55-80% SiO.sub.2;
[0060] 3-20% Al.sub.2O.sub.3;
[0061] 3-15% B.sub.2O.sub.3; and
[0062] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0063] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, and
[0064] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0065] the glass substrate has a heat shrinkage rate of 60 ppm or
less.
[0066] The glass substrate of the present invention can
simultaneously have both a high Tg and strain point and good
devitrification resistance. Therefore, according to the present
invention, a glass substrate having excellent properties can be
provided in which the heat shrinkage caused by a heat treatment
during production of a display is reduced, and therefore, the
non-uniformity of the pixel pitch does not occur.
DETAILED DESCRIPTION OF THE INVENTION
[0067] A display glass substrate according to this embodiment
includes a glass which comprises, as expressed in mol %, 55-80%
SiO.sub.2, 3-20% Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, and 3-25%
RO (the total amount of MgO, CaO, SrO, and BaO), where the contents
in mol % of SiO.sub.2, Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy
a relationship (SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17.
Another display glass substrate of this embodiment includes a glass
which comprises, as expressed in mol %, 55-80% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, and 3-25% RO (the total
amount of MgO, CaO, SrO, and BaO), where the contents in mol % of
SiO.sub.2, Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a
relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0. If the
relationship (SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17,
more preferably the relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, is
satisfied, the glass substrate of this embodiment can have an
increased Tg and strain point while maintaining good
devitrification resistance. By the increase of the Tg and strain
point, the amount of heat shrinkage occurring in a heat treatment
during production of a display is reduced. If the amounts of
SiO.sub.2 and Al.sub.2O.sub.3 are simply increased and the amount
of B.sub.2O.sub.3 is simply decreased in order to increase the Tg
and strain point, the melting temperature may increase, i.e., the
meltability may decrease. However, if SiO.sub.2, Al.sub.2O.sub.3,
and B.sub.2O.sub.3 satisfy the above relationship, the decrease of
the meltability can be reduced. In other words, the glass substrate
of this embodiment can have an increased Tg and strain point while
maintaining good devitrification resistance and good
meltability.
[0068] The glass included in the glass substrate of this embodiment
may comprise 5% or less ZnO as an optional component. In this case,
it is preferable that the contents in mol % of SiO.sub.2 and
Al.sub.2O.sub.3 satisfy SiO.sub.2+Al.sub.2O.sub.3.gtoreq.70%, more
preferably SiO.sub.2+Al.sub.2O.sub.3.gtoreq.75%, and the contents
in mol % of RO, ZnO, and B.sub.2O.sub.3 satisfy
RO+ZnO+B.sub.2O.sub.3=7-25%.
[0069] The glass included in the glass substrate of this embodiment
may have a strain point of 660.degree. C. or more. In order to more
reliably reduce the heat shrinkage during production of a flat
panel display, the strain point is preferably 665.degree. C. or
more, more preferably 675.degree. C. or more, even more preferably
680.degree. C. or more, still even more preferably 685.degree. C.
or more, still even more preferably 690.degree. C. or more, still
even more preferably 695.degree. C. or more, and still even more
preferably 700.degree. C. or more.
[0070] The meltability of a glass may be evaluated by glass
temperature (melting temperature), where the viscosity is
10.sup.2.5 dPas. The glass included in the glass substrate of this
embodiment preferably has a melting temperature of 1680.degree. C.
or less. If the melting temperature is 1680.degree. C. or less, the
glass substrate of this embodiment can have good meltability. If
the melting temperature is excessively low, the Tg and strain point
are likely to be low. Therefore, in order to achieve a high Tg and
strain point, the melting temperature needs to be fairly high.
Therefore, the melting temperature is preferably 1550-1650.degree.
C., more preferably 1550-1645.degree. C., even more preferably
1580-1640.degree. C., still even more preferably 1590-1630.degree.
C., and still even more preferably 1600-1620.degree. C.
[0071] The amount of heat shrinkage may be reduced by appropriately
adjusting conditions under which a glass is produced in addition to
the aforementioned adjustment of a glass composition. Specifically,
when the glass is annealed, then if the glass is cooled at a
necessarily and sufficiently low rate in a temperature region of Tg
to Tg-100.degree. C., the amount of heat shrinkage can be reduced.
Therefore, in the glass substrate of this embodiment, by optionally
adjusting the conditions for the annealing as appropriate in
addition to the aforementioned adjustment of a composition, the
ratio of heat shrinkage can be caused to be 75 ppm or less,
preferably 65 ppm or less, and more preferably 60 ppm or less. If
the ratio of heat shrinkage is 75 ppm or less, preferably 65 ppm or
less, and more preferably 60 ppm or less, even when the glass
substrate of this embodiment is employed in a display to which the
p-Si TFT is applied, and moreover, the display has a high
resolution, the non-uniformity of the pixel pitch can be
sufficiently reduced. In order to reliably reduce the
non-uniformity of the pixel pitch, the ratio of heat shrinkage is
preferably 55 ppm or less, more preferably 50 ppm or less, even
more preferably 45 ppm or less, still even more preferably 43 ppm
or less, still even more preferably 40 ppm or less, and still even
more preferably 38 ppm or less. In other words, the ratio of heat
shrinkage is 0-75 ppm, preferably 0-65 ppm, more preferably 0-60
ppm, even more preferably 0-55 ppm, still even more preferably 0-50
ppm, still even more preferably 0-45 ppm, still even more
preferably 0-43 ppm, still even more preferably 0-40 ppm, and still
even more preferably 0-38 ppm. Note that, in order to cause the
ratio of heat shrinkage to be zero ppm, it may be necessary to
perform the annealing for a considerably long time or perform a
heat shrinkage reduction treatment (off-line annealing) after the
annealing, leading to a reduction in productivity and an increase
in cost. In view of productivity and cost, the ratio of heat
shrinkage is, for example, 3-75 ppm, preferably 5-75 ppm, more
preferably 5-65 ppm, even more preferably 8-55 ppm, still even more
preferably 8-50 ppm, still even more preferably 10-45 ppm, still
even more preferably 10-43 ppm, still even more preferably 10-40
ppm, and still even more preferably 15-38 ppm.
[0072] The glass included in the glass substrate of this embodiment
has a devitrification temperature of 1250.degree. C. or less. If
the devitrification temperature is 1250.degree. C. or less, the
glass included in the glass substrate of this embodiment can be
advantageously easily formed by a downdraw process. As a result,
the surface quality of the glass substrate can be improved, and the
manufacturing cost of the glass substrate can be reduced. If the
devitrification temperature is excessively high, devitrification is
likely to occur, i.e., the devitrification resistance decreases.
Therefore, the devitrification temperature of the glass substrate
of this embodiment preferably 1230.degree. C. or less, more
preferably 1220.degree. C. or less, even more preferably
1210.degree. C. or less, and still even more preferably
1200.degree. C. or less. On the other hand, in order to achieve
properties of a substrate for flat panel displays, such as low heat
shrinkage and low density, the devitrification temperature of the
glass included in the glass substrate is preferably
1050-1250.degree. C., more preferably 1110-1250.degree. C., even
more preferably 1150-1240.degree. C., still even more preferably
1160-1230.degree. C., and still even more preferably
1170-1220.degree. C.
[0073] The glass included in the glass substrate of this embodiment
preferably has a liquidus viscosity of 10.sup.4.0 dPas or more,
more preferably 10.sup.45 dPas or more. If the liquidus viscosity
is 10.sup.4.0 dPas or more, the glass can be easily formed by a
float process. If the liquidus viscosity is 10.sup.45 dPas or more,
the ease of forming is further improved. Therefore, if the liquidus
viscosity is within such a range, the glass included in the glass
substrate of this embodiment can be easily formed by a downdraw
process (particularly, the overflow downdraw process). As a result,
the surface quality of the glass substrate can be improved and the
manufacturing cost of the glass substrate can be reduced. The
liquidus viscosity is more preferably 10.sup.4.5-10.sup.6.0 dPas,
more preferably 10.sup.4.5-10.sup.5.9 dPas, even more preferably
10.sup.4.6-10.sup.5.8 dPas, still even more preferably
10.sup.4.6-10.sup.5.7 dPas, still even more preferably
10.sup.4.7-10.sup.5.7 dPas, still even more preferably
10.sup.4.8-10.sup.5.6 dPas, and still even more preferably
10.sup.4.9-10.sup.5.5 dPas.
[0074] Other properties of the glass included in the glass
substrate of this embodiment are preferably within the following
ranges.
[0075] The average coefficient of thermal expansion within the
range of 100-300.degree. C. of the glass included in the glass
substrate of this embodiment is preferably less than
37.times.10.sup.-7K.sup.-1, more preferably no less than
28.times.10.sup.-7K.sup.-1 and less than
36.times.10.sup.-7K.sup.-1, even more preferably no less than
30.times.10.sup.-7K.sup.-1 and less than
35.times.10.sup.-7K.sup.-1, still even more preferably no less than
31.times.10.sup.-7K.sup.-1 and less than
34.5.times.10.sup.-7K.sup.-1, and still even more preferably no
less than 32.times.10.sup.-7K.sup.-1 and less than
34.times.10.sup.-7K.sup.-1. If the coefficient of thermal expansion
is excessively high, the heat shock or the amount of heat shrinkage
increases in the heat treatment during production of a display. On
the other hand, if the coefficient of thermal expansion is
excessively low, it is difficult to match the coefficients of
thermal expansion of peripheral materials, such as a metal and an
organic adhesive, formed on the glass substrate during production
of a display, and therefore, the peripheral materials are likely to
come off the glass substrate. In the p-Si TFT production process,
rapid heating and rapid cooling are repeatedly performed, and
therefore, greater heat shock is applied to the glass substrate.
When the glass substrate is large, a temperature difference
(temperature distribution) is likely to occur in the heat treatment
step, leading to an increase in the probability of destruction of
the glass substrate. If the coefficient of thermal expansion is
within the aforementioned range, thermal stress caused by a
difference in thermal expansion can be reduced, resulting in a
decrease in the probability of destruction of the glass substrate
in the heat treatment step. Note that when importance is put on the
matching with the coefficients of thermal expansion of the
peripheral materials, such as a metal and an organic adhesive,
formed on the glass substrate, the average coefficient of thermal
expansion within the range of 100-300.degree. C. of the glass
included in the glass substrate is preferably less than
55.times.10.sup.-7K.sup.-1, more preferably less than
40.times.10.sup.-7K.sup.-1, even more preferably no less than
28.times.10.sup.-7K.sup.-1 and less than
40.times.10.sup.-7K.sup.-1, still even more preferably no less than
30.times.10.sup.-7K.sup.-1 and less than
39.times.10.sup.-7K.sup.-1, still even more preferably no less than
32.times.10.sup.-7K.sup.-1 and less than
38.times.10.sup.-7K.sup.-1, and still even more preferably no less
than 34.times.10.sup.-7K.sup.-1 and less than
38.times.10.sup.-7K.sup.-1.
[0076] If the Tg is excessively low, the heat resistance decreases,
and in the heat treatment step, the heat shrinkage increases.
Therefore, the Tg of the glass substrate of this embodiment is
preferably 720.degree. C. or more, more preferably 740.degree. C.
or more, even more preferably 745.degree. C. or more, still even
more preferably 750.degree. C. or more, still even more preferably
755.degree. C. or more, and still even more preferably 760.degree.
C. or more.
[0077] If the density is excessively high, it may be difficult to
reduce the weight of the glass substrate, and therefore, it may be
difficult to reduce the weight of a display. Therefore, the density
of the glass substrate of this embodiment is preferably 2.6
g/cm.sup.3 or less, more preferably less than 2.5 g/cm.sup.3, even
more preferably 2.45 g/cm.sup.3 or less, still even more preferably
2.42 g/cm.sup.3 or less, and still even more preferably 2.4
g/cm.sup.3 or less. In particular, in order to reduce the weight of
the glass substrate for a flat display or an organic EL display
including the p-Si TFT, the density is preferably less than 2.5
g/cm.sup.3, more preferably 2.45 g/cm.sup.3 or less, even more
preferably 2.42 g/cm.sup.3 or less, and still even more preferably
2.4 g/cm.sup.3 or less.
[0078] If the specific resistance of a glass melt is excessively
low, then when a glass material is electrically melted, the value
of a current required for melting the glass material is excessively
large. Therefore, there may be constraints on equipment. Moreover,
the electrode is disadvantageously much consumed. On the other
hand, if the specific resistance is excessively high, then when the
glass material is melted, a current flows through heat-resistant
bricks forming a melting bath, likely leading to damage to the
melting bath. Therefore, the specific resistance at 1550.degree. C.
of the glass included in the glass substrate of this embodiment is
preferably 50-300 .OMEGA.cm, more preferably 50-250 .OMEGA.cm, even
more preferably 80-240 .OMEGA.cm, and still even more preferably
100-230 .OMEGA.cm.
[0079] If the Young's modulus and specific modulus of elasticity
(Young's modulus/density) are excessively low, the glass substrate
is bent or warped by its own weight during production of a display,
likely leading to damage to the glass substrate. In particular, if
the glass substrate is large (e.g., 2000 mm or more wide), the
damage caused by the bending or warp becomes significant.
Therefore, the Young's modulus of the glass substrate of this
embodiment is preferably 70 GPa or more, more preferably 73 GPa or
more, even more preferably 74 GPa or more, and still even more
preferably 75 GPa or more. The specific modulus of elasticity of
the glass substrate of this embodiment is preferably 28 GPa or
more, more preferably 29 GPa or more, even more preferably 30 GPa
or more, and still even more preferably 31 GPa or more.
[0080] Next, components of the glass included in the glass
substrate of this embodiment will be described. Note that "mol %"
is simply hereinafter shortened to "%".
[0081] (SiO.sub.2)
[0082] SiO.sub.2 is a skeltal and essential component. If the
amount of SiO.sub.2 is excessively small, the acid resistance may
decrease, the Tg and strain point may decrease, the coefficient of
thermal expansion may increase, and the buffered hydrofluoric acid
(BHF) resistance may decrease. It may also be difficult to reduce
the density. On the other hand, if the amount of SiO.sub.2 is
excessively large, the melting temperature may be significantly
high, and therefore, it may be difficult to melt and form the
glass. The devitrification resistance may also decrease. Also, when
the glass is slimmed down, the etching rate cannot be sufficiently
increased. Therefore, the SiO.sub.2 content is preferably 55-80%,
more preferably 60-78%, even more preferably 62-78%, still even
more preferably 65-78%, and still even more preferably 65-75%. Note
that when the glass substrate comprises only less than 3% SrO+BaO
in order to further reduce the weight, the SiO.sub.2 content is
more preferably 67-73%, even more preferably 69-72%. In order to
sufficiently increase the etching rate when the glass is slimmed
down, the SiO.sub.2 content is more preferably 62-78%, even more
preferably 62-73%, and still even more preferably 64-70%. On the
other hand, when the glass substrate comprises 3% or more SrO+BaO,
the SiO.sub.2 content is more preferably 65-73%, even more
preferably 66-71%.
[0083] (Al.sub.2O.sub.3)
[0084] Al.sub.2O.sub.3 is an essential component which reduces
phase separating and increases the Tg and strain point. If the
amount of Al.sub.2O.sub.3 is excessively small, the glass is likely
to undergo phase separating. Also, the Tg and strain point may
decrease, so that the heat resistance may decrease, the ratio of
heat shrinkage may increase, and the Young's modulus may decrease.
Also, the rate of etching the glass cannot be sufficiently
increased. On the other hand, if the amount of Al.sub.2O.sub.3 is
excessively large, the devitrification temperature of the glass
increases, so that the devitrification resistance decreases, and
therefore, the ease of forming deteriorates. Therefore, the
Al.sub.2O.sub.3 content is preferably 3-20%, more preferably 5-18%,
and even more preferably 5-15%. Note that when the glass substrate
comprises only less than 3% SrO+BaO in order to further reduce the
weight, the Al.sub.2O.sub.3 content is more preferably 7-13%, even
more preferably 9-12%. In order to sufficiently increase the
etching rate when the glass is slimmed down, the Al.sub.2O.sub.3
content is more preferably 7-15%, even more preferably 9-14%, and
still even more preferably 10.sup.-14%. On the other hand, when the
glass substrate comprises 3% or more SrO+BaO, the Al.sub.2O.sub.3
content is more preferably 8-15%, even more preferably 10-14%.
[0085] (B.sub.2O.sub.3)
[0086] B.sub.2O.sub.3 is an essential component which reduces the
viscosity characteristic (high-temperature viscosity
characteristic) temperature in a high temperature region, typified
by the melting temperature, to improve the meltability (the
"melting temperature" will be described hereinafter as a typical
example of the "high-temperature viscosity characteristic
temperature" in this specification). If the amount of
B.sub.2O.sub.3 is excessively small, the meltability may decrease,
the BHF resistance may decrease, the devitrification resistance may
decrease, and the coefficient of thermal expansion may increase.
Also, the density may increase, so that it may be difficult to
reduce the density. On the other hand, if the amount of
B.sub.2O.sub.3 is excessively large, the Tg and strain point may
decrease, the acid resistance may decrease, and the Young's modulus
may decrease. Also, B.sub.2O.sub.3 evaporates during melting of the
glass, so that the non-uniformity of the glass may become
significant, and therefore, a cord is likely to occur. Therefore,
the B.sub.2O.sub.3 content is preferably 3-15%, more preferably
3-13%, and even more preferably 3-10%. Note that when the glass
substrate comprises only less than 3% SrO+BaO in order to further
reduce the weight, the B.sub.2O.sub.3 content is more preferably no
less than 3% and less than 9.5%, even more preferably no less than
3.5% and less than 9.2%, still even more preferably no less than 4%
and less than 8.9%, still even more preferably 5-8.5%, and still
even more preferably 6-8%. Moreover, in order to prevent the
increase of the devitrification temperature, the B.sub.2O.sub.3
content is more preferably 5-13%, even more preferably 5-12%, and
still even more preferably 6% to less than 10% (no less than 6% and
less than 10%). On the other hand, when the glass substrate
comprises 3% or more SrO+BaO, the B.sub.2O.sub.3 content is more
preferably 3-9%, even more preferably 4-8%.
[0087] (MgO)
[0088] MgO is a component which improves the meltability. MgO is
also a component which hardly increases the density compared with
other alkaline-earth metals. Therefore, if the MgO content is
relatively increased, the density of the glass can be easily
reduced. In the glass substrate of this embodiment, MgO is not
essential. However, if MgO is comprised, the meltability can be
increased and the occurrence of chips can be reduced. Therefore,
MgO may be comprised. However, if the amount of MgO is excessively
large, the Tg and strain point may decrease, the heat resistance
may decrease, and the acid resistance may decrease. Also, the
devitrffication temperature may increase, i.e., the devitrffication
resistance may decrease, and therefore, it may be difficult to
employ a downdraw process. Therefore, in the glass substrate of
this embodiment, the MgO content is preferably 0-15%, more
preferably 0-10%. Note that when the glass substrate comprises only
less than 3% SrO+BaO in order to further reduce the weight, the MgO
content is more preferably 0-5%, even more preferably 0% to less
than 2% (no less than 0% and less than 2%), still even more
preferably 0-1.5%, still even more preferably 0-1%, and still even
more preferably 0-0.5%, and still even more preferably,
substantially no MgO is comprised. Note that, as used herein,
"substantially no MgO is comprised" means that MgO is not added as
a material to the glass material, and the MgO content is preferably
0.2% or less, more preferably 0.15% or less, and even more
preferably 0.1% or less. The phrase "substantially no X (X: a
predetermined component) is comprised" has the same meaning. On the
other hand, when the glass substrate comprises 3% or more SrO+BaO,
the MgO content is more preferably 1-9%, even more preferably
2-8%.
[0089] (CaO)
[0090] CaO is a component which is effective in improving the
meltability of a glass without rapidly increasing the
devitrffication temperature of the glass. CaO is also a component
which increases the density more slowly than other alkaline-earth
metals. Therefore, if the CaO content is relatively increased, the
density of the glass can be easily reduced. If the amount of CaO is
excessively small, the meltability and devitrification resistance
are likely to decrease due to an increase in the viscosity at high
temperature. On the other hand, if the amount of CaO is excessively
large, the coefficient of thermal expansion is likely to increase.
For these reasons, the CaO content is preferably 0-20%, more
preferably 0-18%. Note that when the glass substrate comprises only
less than 3% SrO+BaO in order to further reduce the weight, the CgO
content is more preferably 3.6-16%, even more preferably 4-16%,
still even more preferably 6-16%, still even more preferably more
than 7% and no more than 16%, still even more preferably 8-13%, and
still even more preferably 9-12%. On the other hand, when the glass
substrate comprises 3% or more SrO+BaO, the CaO content is more
preferably 0-10%, even more preferably 0-5%, and still even more
preferably 0-3%.
[0091] (SrO)
[0092] SrO is a component which can decrease the devitrification
temperature of a glass. SrO is not an essential component, but if
SrO is comprised, the devitrification resistance and meltability
can be improved, and therefore, SrO may be comprised. However, if
the amount of SrO is excessively large, the density increases.
Therefore, if it is desirable that the density be reduced,
preferably substantially no SrO is comprised. Therefore, in the
glass substrate of this embodiment, the SrO content is preferably
0-10%, more preferably 0-8%. Note that, in order to further reduce
the weight, the SrO content is preferably less than 3%, more
preferably 2% or less, even more preferably 1% or less, and still
even more preferably 0.5% or less, and still even more preferably,
substantially no SrO is comprised. In other words, the SrO content
is preferably 0% to less than 3% (no less than 0% and less than
3%), more preferably 0-2%, even more preferably 0-1%, and still
even more preferably 0-0.5%, and still even more preferably,
substantially no SrO is comprised. On the other hand, if it is
desirable that the meltability be improved, the SrO content is more
preferably 1-8%, even more preferably 3-8%.
[0093] (BaO)
[0094] BaO is a component which improves the devitrification
resistance and meltability. Also, if BaO is comprised, the
coefficient of thermal expansion increases and the density
excessively increases. Therefore, in the glass substrate of this
embodiment, the BaO content is preferably 0-10%, more preferably
0-5%, even more preferably 0-2%, and still even more preferably
0-1%. In view of the environmental load problem, more preferably
substantially no BaO is comprised.
[0095] (Li.sub.2O, Na.sub.2O)
[0096] Li.sub.2O and Na.sub.2O are components which improve the
meltability of a glass, but increases the coefficient of thermal
expansion of the glass, leading to damage to a substrate in a heat
treatment during production of a display, or significantly
decreases the Tg and strain point of the glass, leading to an
excessive decrease in the heat resistance. Therefore, in the glass
substrate of this embodiment, the Li.sub.2O and Na.sub.2O content
is preferably 0-0.3%, more preferably 0-0.2%, and even more
preferably 0-0.1%, and still even more preferably, substantially no
Li.sub.2O or Na.sub.2O is comprised.
[0097] (K.sub.2O)
[0098] K.sub.2O is a component which increases the basicity of a
glass to impart refinability to the glass. K.sub.2O is also a
component which improves the meltability and decreases the specific
resistance of a glass melt. Therefore, K.sub.2O is not an essential
component, but if K.sub.2O is comprised, the specific resistance of
a glass melt can be decreased and the clarity can be increased.
However, if the amount of K.sub.2O is excessively large, the
coefficient of thermal expansion may increase, and the Tg and
strain point may significantly decrease, leading to an excessive
decrease in the heat resistance. Therefore, in the glass substrate
of this embodiment, the K.sub.2O content is preferably 0-0.8%, more
preferably 0.01-0.5%, and even more preferably 0.1-0.3%.
[0099] (ZrO.sub.2, TiO.sub.2)
[0100] ZrO.sub.2 and TiO.sub.2 are components which increase the
chemical durability and the Tg and strain point of a glass.
ZrO.sub.2 and TiO.sub.2 are not essential components, but if
ZrO.sub.2 and TiO.sub.2 are comprised, the Tg and strain point can
be increased and the acid resistance can be improved. However, if
the amounts of ZrO.sub.2 and TiO.sub.2 are excessively large, the
devitrification temperature significantly increases, and therefore,
the devitrification resistance and the ease of forming may
decrease. In particular, crystals of ZrO.sub.2 may precipitate in a
cooling step, and these inclusions may cause a deterioration in the
quality of the glass. TiO.sub.2 is also a component which adds
color to a glass, and therefore, is not suitable for display
substrates. For these reasons, in the glass substrate of this
embodiment, the ZrO.sub.2 and TiO.sub.2 contents are each
preferably 0-5%, more preferably 0-3%, even more preferably 0-2%,
still even more preferably 0-1%, and still even more preferably
less than 0.5%. Still even more preferably, the glass substrate of
this embodiment comprises substantially no ZrO.sub.2 or
TiO.sub.2.
[0101] (ZnO)
[0102] ZnO is a component which improves the BHF resistance and
meltability, and therefore, may be comprised, but is not an
essential component. However, if the amount of ZnO is excessively
large, the devitrification temperature may increase, the Tg and
strain point may decrease, and the density may increase. Therefore,
in the glass substrate of this embodiment, the ZnO content is
preferably 5% or less, more preferably 3% or less, even more
preferably 2% or less, and still even more preferably 1% or less.
Still even more preferably, the glass substrate of this embodiment
comprises substantially no ZnO. In other words, the ZnO content is
preferably 0-5%, more preferably 0-3%, even more preferably 0-2%,
and still even more preferably 0-1%. Still even more preferably,
the glass substrate of this embodiment comprises substantially no
ZnO.
[0103] (P.sub.2O.sub.5)
[0104] P.sub.2O.sub.5 is a component which decreases the melting
temperature to improve the meltability, and therefore, may be
comprised, but is not an essential component. However, if the
amount of P.sub.2O.sub.5 is excessively large, P.sub.2O.sub.5
evaporates during melting of the glass, so that the non-uniformity
of the glass becomes significant, and therefore, a cord is likely
to occur. Also, it is likely that the Tg and strain point
decreases, the acid resistance significantly deteriorates, and the
glass turns into milky white. Therefore, in the glass substrate of
this embodiment, the P.sub.2O.sub.5 content is preferably 3% or
less, more preferably 1% or less, and even more preferably 0.5% or
less. Still even more preferably, the glass substrate of this
embodiment contains substantially no P.sub.2O.sub.5. In other
words, the P.sub.2O.sub.5 content is preferably 0-3%, more
preferably 0-1%, and even more preferably 0-0.5%. Still even more
preferably, the glass substrate of this embodiment contains
substantially no P.sub.2O.sub.5.
[0105] (Refining Agent)
[0106] Any refining agent that has low environmental load and
imparts excellent clarity to a glass may be employed, i.e., the
present invention is not limited to any particular refining agent.
For example, the refining agent may be at least one selected from
the group consisting of metal oxides of Sn, Fe, Ce, Tb, Mo, and W.
If the amount of the refining agent is excessively small, the foam
quality deteriorates. Therefore, the amount of the refining agent
added is, for example, within the range of 0.01-1%, preferably
0.05-1%, more preferably 0.05-0.5%, even more preferably 0.05-0.3%,
and still even more preferably 0.05-0.2%, although it depends on
the type of the refining agent or the composition of the glass. The
refining agent is preferably SnO.sub.2. However, SnO.sub.2 is a
component which decreases the devitrification resistance of a
glass. Therefore, for example, if SnO.sub.2 is used as the refining
agent, the SnO.sub.2 content is preferably 0.01-0.3%, more
preferably 0.03-0.2%, and even more preferably 0.05-0.15%.
[0107] (Fe.sub.2O.sub.3)
[0108] Fe.sub.2O.sub.3 is a component which works as a refining
agent, and in addition, decreases the viscosity in a
high-temperature region of a glass melt, and decreases the specific
resistance. Fe.sub.2O.sub.3 is not an essential component, but is
preferably comprised in a glass which has a high melting
temperature and is therefore difficult to melt in order to decrease
the melting temperature and specific resistance. If the amount of
Fe.sub.2O.sub.3 is excessively large, color may be added to the
glass, so that the transmittance may decrease. Therefore, in the
glass substrate of this embodiment, the Fe.sub.2O.sub.3 content is
preferably 0-0.1%, more preferably 0-0.08%, even more preferably
0.001-0.05%, and still even more preferably 0.005-0.03%. Here, in a
glass having a high melting temperature, the temperature of the
melting step is high, the effect of Fe.sub.2O.sub.3 as a refining
agent is likely to decrease. Therefore, if Fe.sub.2O.sub.3 is used
singly as a refining agent, the clarity may decrease, so that the
foam quality of the glass substrate may deteriorate. Therefore,
Fe.sub.2O.sub.3 is preferably used in combination with
SnO.sub.2.
[0109] In the glass substrate of this embodiment, in view of the
environmental load problem, the Sb.sub.2O.sub.3 content is
preferably 0-0.5%, more preferably 0-0.3%, even more preferably
0-0.1%, and still even more preferably 0-0.03%. Still even more
preferably, the glass substrate of this embodiment contains
substantially no Sb.sub.2O.sub.3.
[0110] (Components Preferably not Comprise)
[0111] In view of the environmental load problem, the glass
substrate of this embodiment contains substantially no
As.sub.2O.sub.3, Sb.sub.2O.sub.3, PbO, or F.
[0112] Also, compound parameters of components comprised in the
glass substrate of this embodiment will be described
hereinafter.
[0113] ((SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3))
[0114] In the glass included in the glass substrate of this
embodiment, (SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3) is
preferably 7.5-17, more preferably 8-17, and even more preferably
8.45-17.0. By satisfying the relationship, the aforementioned
advantages are obtained. Note that when the glass contains only
less than 3% SrO+BaO in order to further reduce the weight, in
order to reliably obtain the advantages
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3) is preferably
8.5-15.0, more preferably 9.5-14.0, even more preferably 10.0-13.0,
and still even more preferably 10.0-12.5. Moreover, in order to
prevent the increase of the devitrification temperature and achieve
a sufficient etching rate,
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3) is preferably 8-15,
more preferably 8-13, even more preferably 8-11, and still even
more preferably 8-10. On the other hand, when the glass contains 3%
or more SrO+BaO, (SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3) is
more preferably 9.5-17.0%, even more preferably 10.0-17.0%.
[0115] (Alkaline-Earth Metal Oxides (RO: MgO+CaO+SrO+BaO))
[0116] RO is a component which improves the meltability. If the
amount of RO is excessively small, the meltability may deteriorate.
However, if the amount of RO is excessively large, the Tg and
strain point may decrease, the density may increase, the Young's
modulus may decrease, and the coefficient of thermal expansion may
increase. Therefore, in the glass included in the glass substrate
of this embodiment, the RO content is preferably 3-25%, more
preferably 4-20%. Note that when the glass contains only less than
3% SrO+BaO in order to further reduce the weight, the RO content is
more preferably no less than 5% and less than 14%, even more
preferably 6-14%, still even more preferably 8-13%, and still even
more preferably 9-12%. On the other hand, when the glass contains
3% or more SrO+BaO, the RO content is more preferably no less than
5% and less than 18%, even more preferably 8-17%.
[0117] (CaO/RO)
[0118] When the glass contains only less than 3% SrO+BaO in order
to further reduce the weight, CaO/RO is preferably 0.5 or more,
more preferably 0.7 or more, even more preferably more than 0.85,
still even more preferably 0.88 or more, still even more preferably
0.90 or more, still even more preferably 0.92 or more, and still
even more preferably 0.95 or more. In other words, CaO/RO is
preferably 0.5-1, more preferably 0.7-1, even more preferably more
than 0.85 to 1, still even more preferably 0.88-1, still even more
preferably 0.90-1, still even more preferably 0.92-1, and still
even more preferably 0.95-1. If CaO/RO is within such a range, good
devitrification resistance and meltability can be simultaneously
obtained. Moreover, the density can be reduced. If only CaO is
comprised as a material, the Tg and strain point can be further
increased than when a plurality of alkaline-earth metal oxides are
comprised. Note that even if only CaO, which is an alkaline-earth
metal oxide, is comprised as a material, the obtained glass may
contain another alkaline-earth metal oxide as an impurity. If only
CaO, which is an alkaline-earth metal oxide, is comprised as a
material, the value of CaO/RO of the obtained glass is, for
example, about 0.98-1. CaO is also a preferable component because a
material for CaO is inexpensive and easily available.
[0119] (SiO.sub.2--(Al.sub.2O.sub.3/2))
[0120] If the value of SiO.sub.2--(Al.sub.2O.sub.3/2) is
excessively small, the etching rate may increase, but the
devitrification resistance may decrease. On the other hand, if the
value is excessively large, the etching rate may decrease.
Therefore, in the glass included in the glass substrate of this
embodiment, SiO.sub.2--(Al.sub.2O.sub.3/2) is preferably 69 or
less, more preferably 50-68, even more preferably 55-65, still even
more preferably 57-63, and still even more preferably 58-62.
[0121] In order to perform etching (slimming) the glass substrate
with a high productivity, the etching rate is preferably 50 .mu.m/h
or more. On the other hand, if the etching rate is excessively
high, a problem is likely to occur in a reaction with a chemical
solution in a panel production step. Therefore, for the glass
included in the glass substrate, the etching rate is preferably 160
.mu.m/h or less. The etching rate is preferably 60-140 .mu.m/h,
more preferably 70-120 .mu.m/h. In the present invention, the
etching rate is defined as being measured under the following
conditions.
[0122] The etching rate (.mu.m/h) is represented by the amount of a
decrease in the thickness of one surface of the glass substrate per
unit time (one hour), where the glass substrate is immersed in an
etchant (an acid mixture of HF (concentration: 1 mol/kg) and HCl
(concentration: 5 mol/kg)) at 40.degree. C. for 1 hour.
[0123] (SiO.sub.2+Al.sub.2O.sub.3)
[0124] If SiO.sub.2+Al.sub.2O.sub.3 is excessively small, the Tg
and strain point are likely to decrease. On the other hand, if
SiO.sub.2+Al.sub.2O.sub.3 is excessively large, the devitrification
resistance is likely to deteriorate. Therefore, in the glass
included in the glass substrate of this embodiment,
SiO.sub.2+Al.sub.2O.sub.3 is preferably 70% or more, more
preferably 75% or more, and even more preferably 76-88%. Note that
when the glass contains only less than 3% SrO+BaO in order to
further reduce the weight, SiO.sub.2+Al.sub.2O.sub.3 is more
preferably 78-88%, even more preferably 79-85%, and still even more
preferably 80-84%. Moreover, in order to prevent the increase of
the devitrification temperature, SiO.sub.2+Al.sub.2O.sub.3 is more
preferably 76-85%, even more preferably 76-83%, and still even more
preferably 78-82%. On the other hand, when the glass contains 3% or
more SrO+BaO, SiO.sub.2+Al.sub.2O.sub.3 is more preferably 76-86%,
even more preferably 77-83%.
[0125] (Al.sub.2O.sub.3/SiO.sub.2)
[0126] If Al.sub.2O.sub.3/SiO.sub.2 exceeds 0.35, the
devitrification resistance is likely to deteriorate. On the other
hand, if Al.sub.2O.sub.3/SiO.sub.2 is 0.05 or less, the Tg and
strain point cannot be sufficiently increased. Therefore, in this
embodiment, Al.sub.2O.sub.3/SiO.sub.2 is 0.05-0.35, preferably
0.07-0.30, and more preferably 0.10-0.25.
[0127] (B.sub.2O.sub.3+P.sub.2O.sub.5)
[0128] If B.sub.2O.sub.3+P.sub.2O.sub.5 is excessively small, the
meltability is likely to decrease. On the other hand, if
B.sub.2O.sub.3+P.sub.2O.sub.5 is excessively large,
B.sub.2O.sub.3+P.sub.2O.sub.5 evaporates during melting of the
glass, so that the non-uniformity of the glass becomes significant,
and therefore, a cord is likely to occur. Moreover, the Tg and
strain point are likely to decrease. Therefore, in the glass
included in the glass substrate of this embodiment,
B.sub.2O.sub.3+P.sub.2O.sub.5 is preferably 3-15%, more preferably
3-10%. Note that when the glass contains only less than 3% SrO+BaO
in order to further reduce the weight,
B.sub.2O.sub.3+P.sub.2O.sub.5 is more preferably no less than 3%
and less than 9.5%, even more preferably no less than 4% and less
than 8.9%, still even more preferably 5-8.5%, and still even more
preferably 6-8%. Moreover, in order to improve the devitrification
resistance, B.sub.2O.sub.3+P.sub.2O.sub.5 is more preferably 5-13%,
even more preferably 5-12%, still even more preferably 6% to less
than 10% (no less than 6% and less than 10%). On the other hand,
when the glass contains 3% or more SrO+BaO,
B.sub.2O.sub.3+P.sub.2O.sub.5 is more preferably 3-9%, even more
preferably 4-8%.
[0129] (CaO/B.sub.2O.sub.3)
[0130] Note that when the glass contains only less than 3% SrO+BaO
in order to further reduce the weight, then if CaO/B.sub.2O.sub.3
is excessively low, the Tg and strain point are likely to decrease.
On the other hand, if CaO/B.sub.2O.sub.3 is excessively high, the
meltability is likely to deteriorate. Therefore, in this
embodiment, CaO/B.sub.2O.sub.3 is preferably 0.5 or more, more
preferably 0.7 or more, even more preferably 0.9 or more, still
even more preferably more than 1.2, still even more preferably more
than 1.2 and no more than 5, still even more preferably more than
1.2 and no more than 3, still even more preferably 1.3 or more and
2.5 or less, and still even more preferably 1.3 or more and 2 or
less. Moreover, in order to improve the meltability,
CaO/B.sub.2O.sub.3 is preferably 0.5-5, more preferably 0.9-3, even
more preferably more than 1 and no more than 2.5, still even more
preferably more than 1 and no more than 2, still even more
preferably more than 1.2 and no more than 2, and still even more
preferably more than 1.2 and no more than 1.5.
[0131] (SrO+BaO)
[0132] SrO and BaO are components which can decrease the
devitrification temperature of a glass. These components are not
essential, but if these components are comprised, the
devitrification resistance and meltability can be improved.
However, if the amount of these components is excessively large,
the density increases. Therefore, it is difficult to decrease the
density and reduce the weight. Also, the coefficient of thermal
expansion may increase. Therefore, in the glass included in the
glass substrate of this embodiment, SrO+BaO is preferably 10% or
less. Note that, in order to further reduce the weight, SrO+BaO is
more preferably 5% or less, even more preferably less than 3%, and
still even more preferably less than 2%. Still even more
preferably, the glass included in the glass substrate of this
embodiment contains substantially no SrO or BaO. In other words,
SrO+BaO is preferably 0-10%. In order to further reduce the weight,
SrO+BaO is more preferably 0-5%, even more preferably 0% to less
than 3% (no less than 0% and less than 3%), still even more
preferably 0% to less than 2% (no less than 0% and less than 2%),
still even more preferably 0% to less than 1% (no less than 0% and
less than 1%), and still even more preferably 0% to less than 0.5%
(no less than 0% and less than 0.5%). Still even more preferably,
the glass included in the glass substrate of this embodiment
contains no SrO or BaO.
[0133] (RO+ZnO+B.sub.2O.sub.3)
[0134] If RO+ZnO+B.sub.2O.sub.3 is excessively small, the viscosity
in a high-temperature region is likely to be high, and the clarity
and glass meltability are likely to decrease. On the other hand, if
RO+ZnO+B.sub.2O.sub.3 is excessively large, the Tg and strain point
are likely to decrease. Therefore, in the glass included in the
glass substrate of this embodiment, RO+ZnO+B.sub.2O.sub.3 is
preferably 7-30%, more preferably 10.sup.-27%. Note that when the
glass contains only less than 3% SrO+BaO in order to further reduce
the weight, RO+ZnO+B.sub.2O.sub.3 is more preferably 12-22%, even
more preferably 14-21%, and still even more preferably 16-20%.
Moreover, in order to improve the meltability,
RO+ZnO+B.sub.2O.sub.3 is more preferably 12-27%, even more
preferably 14-25%, and still even more preferably 17-23%. On the
other hand, when the glass contains 3% or more SrO+BaO,
RO+ZnO+B.sub.2O.sub.3 is more preferably 13-27%, even more
preferably 15-25%.
[0135] (Alkali Metal Oxide (R.sub.2O:
Li.sub.2O+Na.sub.2O+K.sub.2O))
[0136] R.sub.2O is a component which increases the basicity of a
glass to facilitate oxidation of a refining agent, thereby
imparting clarity to the glass. R.sub.2O is also a component which
facilitates improvement of the meltability of a glass and decrease
of the specific resistance of the glass, and may be comprised.
R.sub.2O is not an essential component, but if it is comprised, can
decrease the specific resistance and improve the clarity and
meltability. However, if the amount of R.sub.2O is excessively
large, the Tg and strain point may excessively decrease, and the
coefficient of thermal expansion may increase. Therefore, in the
glass included in the glass substrate of this embodiment, R.sub.2O
is preferably 0-0.8%, more preferably 0.01-0.5%, and even more
preferably 0.1-0.3%.
[0137] (K.sub.2O/R.sub.2O)
[0138] K.sub.2O has a larger molecular weight than those of
Li.sub.2O and Na.sub.2O, and therefore, runs off the glass
substrate to a lesser extent. Therefore, if R.sub.2O is comprised,
K.sub.2O is preferably comprised at a higher ratio. K.sub.2O is
preferably comprised at a higher ratio than that of Li.sub.2O
(K.sub.2O>Li.sub.2O is satisfied). K.sub.2O is preferably
comprised at a higher ratio than that of Na.sub.2O
(K.sub.2O>Na.sub.2O is satisfied). K.sub.2O/R.sub.2O is
preferably 0.5 or more, more preferably 0.6 or more, even more
preferably 0.7 or more, still even more preferably 0.8 or more, and
still even more preferably 0.95 or more. In other words,
K.sub.2O/R.sub.2O is preferably 0.5-1, more preferably 0.6-1, even
more preferably 0.7-1, still even more preferably 0.8-1, and still
even more preferably 0.95-1.
[0139] The glass included in the glass substrate of this embodiment
can be obtained by appropriately combining the above components.
The combination of the components is not limited. Example
combinations will be described hereinafter. The glass may
contain
[0140] 65-78% SiO.sub.2
[0141] 3-20% Al.sub.2O.sub.3
[0142] 3-15% B.sub.2O.sub.3
[0143] 0% to less than 2% (no less than 0% and less than 2%)
MgO
[0144] 3.6-16% CaO
[0145] 0-2% SrO
[0146] 0% to less than 1% (no less than 0% and less than 1%)
BaO
where
[0147] the B.sub.2O.sub.3, P.sub.2O.sub.5, and CaO contents in mol
% may satisfy relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-15% and
CaO/B.sub.2O.sub.3>1.2.
[0148] Alternatively, the glass may contain
[0149] 65-78% SiO.sub.2
[0150] 3-20% Al.sub.2O.sub.3
[0151] 3-9.5% B.sub.2O.sub.3
[0152] 0% to less than 2% (no less than 0% and less than 2%)
MgO
[0153] 3.6-16% CaO
[0154] 0-2% SrO
[0155] substantially no BaO
where
[0156] the B.sub.2O.sub.3, P.sub.2O.sub.5, and CaO contents in mol
% may satisfy relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-9.5%
and CaO/B.sub.2O.sub.3>1.2.
[0157] The glass substrate of this embodiment is a substrate for
displays. Specifically, the glass substrate of this embodiment is
suitable as a flat panel display glass substrate on which the p-Si
TFT is formed. The glass substrate of this embodiment is also
suitable as a liquid crystal display glass substrate and an organic
EL display glass substrate. In particular, the glass substrate of
this embodiment is suitable as a p-Si TFT liquid crystal display
glass substrate and organic EL display glass substrate. The glass
substrate of this embodiment is suitable as a display glass
substrate for mobile terminals for which a high resolution is
required, among other things. Alternatively, the glass substrate of
this embodiment is suitable as an oxide semiconductor thin film
flat panel display glass substrate. More specifically, the glass
substrate of this embodiment is suitable as a glass substrate used
in a flat panel display which is produced by forming an oxide
semiconductor thin film TFT on a substrate surface.
[0158] The size of the glass substrate of this embodiment can be
appropriately adjusted, depending on the size of a display to which
the glass substrate is applied, and therefore, is not particularly
limited. The length in the width direction of the glass substrate
is, for example, 500-3500 mm, preferably 1000-3500 mm, and more
preferably 2000-3500 mm. The length in the longitudinal direction
of the glass substrate, for example, 500-3500 mm, preferably
1000-3500 mm, and more preferably 2000-3500 mm. As the size of the
glass substrate increases, the productivity of liquid crystal
displays or organic EL displays is improved.
[0159] The thickness of the glass substrate of this embodiment can
be appropriately adjusted, depending on the size of a display to
which the glass substrate is applied, and therefore, is not
particularly limited. However, if the glass substrate is
excessively thin, the strength of the glass substrate itself
decreases. For example, damage is likely to occur during production
of a liquid crystal display. On the other hand, if the glass
substrate is excessively thick, the glass substrate is not suitable
for a display which is desired to be thinner. Also, if the glass
substrate is excessively thick, the glass substrate has a heavy
weight, and therefore, it is difficult to reduce the weight of a
liquid crystal display. Therefore, the thickness of the glass
substrate of this embodiment is preferably 0.1-1.1 mm, more
preferably 0.1-0.7 mm, even more preferably 0.3-0.7 mm, and still
even more preferably 0.3-0.5 mm.
[0160] The glass substrate of this embodiment is manufactured by a
method including a melting step of melting a glass material to
produce molten glass, a forming step of forming the molten glass
into a glass plate, and an annealing step of annealing the glass
plate. Note that the ratio of heat shrinkage of the glass plate is
75 ppm or less, preferably 60 ppm or less. The glass included in
the glass substrate has a devitrification temperature of
1250.degree. C. or less, and contains, as expressed in mol %,
SiO.sub.2 (55-80%), Al.sub.2O.sub.3 (3-20%), B.sub.2O.sub.3
(3-15%), RO (3-25%: the total amount of MgO, CaO, SrO, and BaO) as
a glass composition. The SiO.sub.2, Al.sub.2O.sub.3, and
B.sub.2O.sub.3 contents in mol % satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17, preferably
8.45-17.0. In this case, the glass preferably has a strain point of
665.degree. C. or more.
[0161] The glass substrate of this embodiment can be manufactured
by a known method for manufacturing a glass substrate. Also, a
known forming method can be used, and a float process or a downdraw
process is preferable. In particular, the overflow downdraw process
is preferable. The glass substrate formed by tThe glass substrate
formed by the downdraw process has main surfaces which are made by
hot forming by hot forming, and therefore, is considerably highly
flat and smooth. Therefore, it is no longer necessary to polish the
surface of the glass substrate after the forming, resulting in a
reduction in manufacturing cost and an improvement in productivity.
Moreover, both main surfaces of the glass substrate formed by the
downdraw process have a uniform composition, and therefore, can be
uniformly etched during an etching process. In addition, by forming
by the downdraw process, the glass substrate can obtain a surface
condition free from a microcrack. As a result, the strength of the
glass substrate itself can be improved.
[0162] In order to manufacture the glass substrate having a heat
shrinkage ratio of 75 ppm or less, preferably 60 ppm or less, it is
desirable that conditions under which annealing is performed be
adjusted as appropriate. For example, when the downdraw process is
used, annealing is desirably performed while keeping the
temperature of the glass plate within the temperature range of
Tg.degree. C. to Tg-100.degree. C. for 20-120 sec. In other words,
when the downdraw process is used, annealing is desirably performed
so that the glass plate is cooled to the temperature range of
Tg.degree. C. to Tg-100.degree. C. in 20-120 sec. If the time is
less than 20 sec, the amount of heat shrinkage may not be
sufficiently reduced. On the other hand, if the time exceeds 120
sec, the productivity decreases and the size of the glass
manufacturing equipment (annealing furnace) increases. Therefore,
in order to reduce the ratio of heat shrinkage while keeping the
cost and productivity, annealing is preferably performed while
keeping the temperature of the glass plate within the temperature
range of Tg.degree. C. to Tg-100.degree. C. for 20-120 sec, more
preferably 30-120 sec, and even more preferably 50-100 sec. In
other words, annealing is preferably performed so that the glass
plate is cooled to the temperature range of Tg.degree. C. to
Tg-100.degree. C. in 20-120 sec, more preferably 30-120 sec, and
even more preferably 50-100 sec. Alternatively, annealing is
preferably performed so that the average rate of cooling a center
portion of the glass plate within the temperature range of
Tg.degree. C. to Tg-100.degree. C. is 50-300.degree. C./min. If the
average cooling rate exceeds 300.degree. C./min, the amount of heat
shrinkage may not be sufficiently reduced. On the other hand, if
the average cooling rate is less than 50.degree. C./min, the
productivity decreases and the size of the glass manufacturing
equipment (annealing furnace) increases. Therefore, the average
cooling rate range for reducing the ratio of heat shrinkage while
keeping the cost and productivity is preferably 50-300.degree.
C./min, more preferably 50-200.degree. C./min, and even more
preferably 60-120.degree. C./min. On the other hand, by separately
providing a heat shrinkage reduction treatment (off-line annealing)
step after the annealing step, the ratio of heat shrinkage can be
reduced. However, if the off-line annealing step is provided
separately from the annealing step, the productivity decreases and
the cost increases. Therefore, as described above, the heat
shrinkage reduction treatment (off-line annealing) of controlling
the rate of cooling the glass plate is more preferably performed in
the annealing step so that the ratio of heat shrinkage falls within
the predetermined range.
[0163] The water content of glass may be represented by a .beta.-OH
value. As the .beta.-OH value decreases, the Tg and strain point
tend to increase. On the other hand, as the .beta.-OH value
increases, the melting temperature tends to decrease. In order to
simultaneously achieve both the increase of the Tg and strain point
and the improvement of the meltability, the .beta.-OH value is
preferably 0.05-0.40 mm.sup.-1, more preferably 0.10-0.35
mm.sup.-1, even more preferably 0.10-0.30 mm.sup.-1, and still even
more preferably 0.10-0.25 mm.sup.-1. The .beta.-OH value can be
adjusted by selecting the material. For example, the .beta.-OH
value can be increased and decreased by selecting a material having
a high water content (e.g., a hydroxide material) or adjusting the
content of a material (e.g., a chloride) which reduces the water
content of a glass. The .beta.-OH value can also be adjusted by
adjusting the ratio of gas burning heating (oxygen burning heating)
and electrical heating (direct electrical heating) for melting
glass. The .beta.-OH value can also be increased by increasing the
amount of moisture in furnace atmosphere or bubbling water vapor
with respect to molten glass during the melting. Note that the
.beta.-OH value of a glass is calculated based on the infrared
absorption spectrum of the glass by the following expression:
.beta.-OH value=(1/X)log 10(T1/T2)
[0164] X: glass thickness (mm)
[0165] T1: transmittance (%) at a reference wavelength of 2600
nm
[0166] T2: minimum transmittance (%) in the vicinity of a hydroxyl
group absorption wavelength of 2800 nm
[0167] As examples of the flat panel display glass substrate of
this embodiment obtained from the present disclosure, first to
fourth glass substrates will be described hereinafter. As examples
of the method for manufacturing the glass substrate of this
embodiment obtained from the present disclosure, first to fourth
manufacturing methods will be described hereinafter.
[0168] The first flat panel display glass substrate includes a
glass comprising, as expressed in mol %:
[0169] 55-80% SiO.sub.2;
[0170] 3-20% Al.sub.2O.sub.3;
[0171] 3-15% B.sub.2O.sub.3; and
[0172] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0173] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17,
[0174] the strain point of the glass is 665.degree. C. or more,
and
[0175] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0176] the ratio of heat shrinkage of the glass substrate is 75 ppm
or less.
[0177] The second flat panel display glass substrate includes a
glass comprising, as expressed in mol %:
[0178] 55-80% SiO.sub.2;
[0179] 3-20% Al.sub.2O.sub.3;
[0180] 3-15% B.sub.2O.sub.3; and
[0181] RO (the total amount of MgO, CaO, SrO, and BaO) 3-25%
wherein
[0182] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, and
[0183] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0184] the ratio of heat shrinkage of the glass substrate is 60 ppm
or less.
[0185] The third flat panel display glass substrate includes a
glass comprising, as expressed in mol %,
[0186] 65-78% SiO.sub.2
[0187] 3-20% Al.sub.2O.sub.3
[0188] 3-15% B.sub.2O.sub.3
[0189] 0% to less than 2% MgO
[0190] 3.6-16% CaO
[0191] 0-2% SrO
[0192] 0% to less than 1% BaO
where
[0193] the contents in mol % of B.sub.2O.sub.3, P.sub.2O.sub.5, and
CaO satisfy relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-15% and
CaO/B.sub.2O.sub.3>1.2,
[0194] the strain point of the glass is 665.degree. C. or more,
and
[0195] the devitrification temperature of the glass is 1250.degree.
C. or less.
[0196] The fourth flat panel display glass substrate includes a
glass comprising, as expressed in mol %,
[0197] 65-78% SiO.sub.2
[0198] 3-20% Al.sub.2O.sub.3
[0199] 3-9.5% B.sub.2O.sub.3
[0200] 0% to less than 2% MgO
[0201] 3.6-16% CaO
[0202] 0-2% SrO
[0203] substantially no BaO
where
[0204] the contents in mol % of B.sub.2O.sub.3, P.sub.2O.sub.5, and
CaO satisfy relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-9.5% and
CaO/B.sub.2O.sub.3>1.2, and
[0205] the devitrification temperature of the glass is 1250.degree.
C. or less.
[0206] The first to fourth flat panel display glass substrates are
suitable as flat panel display glass substrates on which the p-Si
TFT is formed. In particular, the first to fourth flat panel
display glass substrates are suitable as liquid crystal display
glass substrates on which the p-Si TFT is formed. Alternatively,
the first to fourth flat panel display glass substrates are also
suitable as organic EL display glass substrates. Alternatively, the
first to fourth flat panel display glass substrates are suitable as
display glass substrates on which an oxide semiconductor thin film
transistor is formed.
[0207] The first method for manufacturing a flat panel display
glass substrate includes
[0208] a melting step of melting a glass material for a glass
comprising, as expressed in mol %, 55-80% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, and 3-25% RO (the total
amount of MgO, CaO, SrO, and BaO), with the contents in mol % of
SiO.sub.2, Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfying a
relationship (SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17.0,
the strain point of the glass being 665.degree. C. or more, and the
devitrification temperature of the glass being 1250.degree. C. or
less, to produce a molten glass,
[0209] a forming step of forming the molten glass into a glass
plate, and
[0210] an annealing step of annealing the glass plate, where
[0211] the rate of heat shrinkage of the glass plate is 75 ppm or
less.
[0212] The second method for manufacturing a flat panel display
glass substrate includes
[0213] a melting step of melting a glass material for a glass
comprising, as expressed in mol %, 55-80% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, and 3-25% RO (the total
amount of MgO, CaO, SrO, and BaO), with the contents in mol % of
SiO.sub.2, Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfying a
relationship (SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0
and the devitrification temperature of the glass being 1250.degree.
C. or less, to produce a molten glass,
[0214] a forming step of forming the molten glass into a glass
plate, and
[0215] an annealing step of annealing the glass plate, where
[0216] the rate of heat shrinkage of the glass plate is 60 ppm or
less.
[0217] The third method for manufacturing a flat panel display
glass substrate includes
[0218] a melting step of melting a glass material for a glass
comprising, as expressed in mol %, 65-78% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-15% B.sub.2O.sub.3, 0% to less than 2% MgO,
3.6-16% CaO, 0-2% SrO, and 0% to less than 1% BaO, with the
contents in mol % of B.sub.2O.sub.3, P.sub.2O.sub.3, and CaO
satisfying relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-15% and
CaO/B.sub.2O.sub.3>1.2, the strain point of the glass being
665.degree. C. or more, and the devitrification temperature of the
glass being 1250.degree. C. or less, to produce a molten glass,
[0219] a forming step of forming the molten glass into a glass
plate, and
[0220] an annealing step of annealing the glass plate.
[0221] The fourth method for manufacturing a flat panel display
glass substrate includes
[0222] a melting step of melting a glass material for a glass
comprising, as expressed in mol %, 65-78% SiO.sub.2, 3-20%
Al.sub.2O.sub.3, 3-9.5% B.sub.2O.sub.3, 0% to less than 2% MgO,
3.6-16% CaO, 0-2% SrO, and substantially no BaO, with the contents
in mol % of B.sub.2O.sub.3, P.sub.2O.sub.3, and CaO satisfying
relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-9.5% and
CaO/B.sub.2O.sub.3>1.2 and the devitrification temperature of
the glass being 1250.degree. C. or less, to produce a molten
glass,
[0223] a forming step of forming the molten glass into a glass
plate, and
[0224] an annealing step of annealing the glass plate.
[0225] In the annealing steps of the first to fourth manufacturing
methods of the flat panel display glass substrate, a heat shrinkage
reduction treatment for reducing the rate of heat shrinkage is
preferably performed by controlling the rate of cooling the glass
plate. Also, in the annealing steps, the heat shrinkage reduction
treatment is more preferably performed so that the average cooling
rate of a center portion of the glass plate within the temperature
range of Tg.degree. C. to Tg-100.degree. C. is 50-300.degree.
C./min.
EXAMPLES
[0226] Next, the glass substrate of the present invention will be
described in detail by way of example. Note that the present
invention is not intended to be limited to examples described
below.
[0227] <First Glass Substrate>
[0228] The first glass substrate will be described by way of
example. Note that the first glass substrate includes a glass
comprising, as expressed in mol %:
[0229] 55-80% SiO.sub.2;
[0230] 3-20% Al.sub.2O.sub.3;
[0231] 3-15% B.sub.2O.sub.3; and
[0232] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0233] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=7.5-17,
[0234] the strain point of the glass is 665.degree. C. or more,
and
[0235] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0236] the rate of heat shrinkage of the glass substrate is 75 ppm
or less.
Examples 1-1 to 1-24 and Comparative Examples 1-1 to 1-6
[0237] Sample glasses of Examples 1-1 to 1-24 and Comparative
Examples 1-1 to 1-6 were produced by a procedure described below so
that the sample glasses have glass compositions shown in Tables 1-1
and 1-2. For the obtained sample glasses and sample glass
substrates, devitrification temperature, Tg, average coefficient of
thermal expansion within the range of 100-300.degree. C., rate of
heat shrinkage, density, strain point, melting temperature (glass
temperature where viscosity is 10.sup.2.5 dPas), liquidus
viscosity, and specific resistance at 1550.degree. C., were
measured.
[0238] (Production of Sample Glass)
[0239] Initially, glass material batches (hereinafter referred to
as "batches") having glass compositions shown in Tables 1-1 and 1-2
were prepared using typical glass materials, i.e., silica, alumina,
boron oxide, potassium carbonate, basic magnesium carbonate,
calcium carbonate, strontium carbonate, tin dioxide, and iron(III)
oxide, in amounts which would provide 400 g of a glass.
[0240] The prepared batch was melted, followed by refining, in a
platinum crucible. Initially, the crucible was held for 4 hours in
an electrical furnace which was set to 1575.degree. C. to melt the
batch. Next, the temperature of the electrical furnace was
increased to 1640.degree. C., and the platinum crucible was held
for 2 hours to perform refining on the glass melt. Thereafter, the
glass melt was poured onto an iron plate outside the furnace, and
was cooled and solidified to obtain a glass piece. Following this,
an annealing process was performed on the glass piece. In the
annealing process, the glass piece was held for 2 hours in another
electrical furnace which was set to 800.degree. C., and thereafter,
cooled for 2 hours until the temperature dropped to 740.degree. C.,
and further cooled for 2 hours until the temperature dropped to
660.degree. C. Thereafter, the electrical furnace was turned off,
and the glass piece was cooled to room temperature. The glass piece
after the annealing process was a sample glass. The sample glass
was used to measure properties (devitrification temperature,
melting temperature, specific resistance, density, coefficient of
thermal expansion, and Tg and strain point), which are not affected
by annealing conditions and/or cannot be measured in the form of a
substrate.
[0241] The sample glass was cut, ground, and polished to produce a
sample glass substrate of 30 mm.times.40 mm.times.0.7 mm whose top
and bottom surfaces are a mirror surface. The sample glass
substrate was used to measure .beta.-OH, which is not affected by
annealing conditions.
[0242] Moreover, the sample glass substrate was formed into a
rectangular parallelepiped having a width of 5 mm and a length of
20 mm by a commonly used glass processing technique. The resulting
sample glass substrate was kept at Tg for 30 min, and thereafter,
cooled at a rate of 100.degree. C./min until the temperature
reached Tg-100.degree. C. and then cooled until the temperature
reached room temperature. The sample glass substrate for
measurement of heat shrinkage was thus prepared.
[0243] (Method for Measuring Devitrification Temperature)
[0244] The sample glass was pulverized, and was passed through a
2380-.mu.m sieve. Glass particles which were retained on a
1000-.mu.m sieve were obtained. The glass particles were immersed
in ethanol, followed by ultrasonic cleaning and then drying in a
constant temperature bath. Twenty-five grams of the dried glass
particles were placed to substantially a uniform thickness in a
platinum boat having a width of 12 mm, a length of 200 mm, and a
depth of 10 mm. The platinum boat was held for 5 hours in an
electrical furnace having a temperature gradient of
1080-1320.degree. C. (for Examples 1-1 to 1-6, 1-8 to 1-24 and
Comparative Examples 1-1 and 1-3 to 1-5) or 1140-1380.degree. C.
(for Examples 1-7 and Comparative Examples 1-2 and 1-6).
Thereafter, the platinum boat was removed from the furnace.
Devitrification occurring inside the glass was observed by a
50.times. optical microscope. A highest temperature at which
devitrification was observed was defined as a devitrification
temperature.
[0245] (Melting Temperature)
[0246] The melting temperature of the sample glass was measured
using a platinum sphere dragging type automatic viscometer. A
temperature at which the viscosity was 10.sup.2.5 dPas was
calculated from the measurement result, and was defined as the
melting temperature.
[0247] (Liquidus Viscosity)
[0248] A viscosity at the devitrification temperature was
calculated from the measurement result of the melting temperature,
and was defined as a liquidus viscosity.
[0249] (Specific Resistance)
[0250] The specific resistance of the sample glass as it is melted
was measured by four-terminal sensing using the 4192A LF impedance
analyzer (manufactured by HP). The specific resistance value at
1550.degree. C. was calculated from the measurement result.
[0251] (Method for Measuring Average Coefficient of Thermal
Expansion and Tg within Range of 100-300.degree. C.)
[0252] The sample glass was processed into the form of a cylinder
having a diameter (.phi.) of 5 mm and a length of 20 mm, and was
used as a test piece. The temperature and the amount of
expansion/shrinkage of the test piece were measured in the process
of increasing the temperature of the test piece using a
differential thermal dilatometer (Thermo Plus2 TMA8310). In this
case, the rate of increasing the temperature was 5.degree. C./min.
The average coefficient of thermal expansion and the Tg within the
temperature range of 100-300.degree. C. were measured based on the
measurement results of the temperature and the amount of
expansion/shrinkage of the test piece. Note that the Tg as used
herein refers to a value of a sample glass which was measured by
holding a glass piece in another electrical furnace which was set
to 800.degree. C. for 2 hours, cooling the glass piece for 2 hours
until the temperature dropped to 740.degree. C., and then cooling
the glass piece for 2 hours until the temperature dropped to
660.degree. C., and thereafter, turning off the electrical furnace,
and cooling the glass piece until the temperature dropped to room
temperature.
[0253] (Strain Point)
[0254] The sample glass was cut and ground into the form of a prism
having a 3-mm square base and a length of 55 mm, and was used as a
test piece. The test piece was measured using a beam bending
measurement device (manufactured by TokyoKogyo Co., Ltd.). The
strain point was calculated by a beam bending technique (ASTM
C-598).
[0255] (Density)
[0256] The sample glass was mirror-polished to produce a plate-like
sample of 5.times.30.times.30 mm. This sample was used to measure
the density of the glass using Archimedes' technique.
[0257] (Rate of Heat Shrinkage)
[0258] The rate of heat shrinkage was calculated from the amount of
shrinkage of the glass substrate for measurement of heat shrinkage
after a heat treatment at 550.degree. C. for 2 hours using the
following expression:
the rate of heat shrinkage (ppm)={the amount of shrinkage of the
glass substrate after the heat treatment/the length of the glass
substrate before the heat treatment}.times.10.sup.6
[0259] In this example, the amount of shrinkage was specifically
measured by the following technique.
[0260] The heat shrinkage sample glass was heated from room
temperature to 550.degree. C. using a differential thermal
dilatometer (Thermoflex TMA8140 manufactured by Rigaku
Corporation), was held for 2 hours, and was cooled to room
temperature. The amount of shrinkage of the sample glass between
before and after the heat treatment was measured. In this case, the
rate of increasing the temperature was 10.degree. C./min.
[0261] (Etching Rate)
[0262] The glass substrate was immersed in an etchant (an acid
mixture of HF (concentration: 1 mol/kg) and HCl (concentration: 5
mol/kg)) at 40.degree. C. for 1 hour. Thereafter, a reduction
(.mu.m) in the thickness of one surface of the glass substrate was
measured. The reduction (.mu.m) per unit time (one hour) was
defined as an etching rate (.mu.m/h).
TABLE-US-00001 TABLE 1-1 Examples 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8
Compo- SiO.sub.2 71.7 71.6 70.8 70.5 70.5 70.3 69.4 69.7 sition
B.sub.2O.sub.3 6.0 6.0 6.9 7.4 7.4 7.8 8.7 9.7 (mol %)
Al.sub.2O.sub.3 11.1 11.1 11.0 10.9 10.9 10.9 10.8 10.8 K.sub.2O
0.17 0.17 0.17 0.17 0.40 MgO 1.0 CaO 11.1 11.1 11.0 10.9 9.9 10.9
9.8 8.9 SrO 0.8 0.8 BaO SnO.sub.2 0.08 0.08 0.08 0.08 0.08 0.08
0.08 0.08 Fe.sub.2O.sub.3 0.022 0.022 0.022 0.022 (SiO.sub.2 +
Al.sub.2O.sub.3)/ 13.8 13.8 11.8 11.0 11.0 10.3 9.2 8.3
B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 82.8 82.6 81.8 81.4 81.4
81.2 80.2 80.5 RO + B.sub.2O.sub.3 + 17.1 17.1 17.9 18.3 18.3 18.7
19.3 19.4 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.15 0.15 0.15 0.15 0.15
0.15 0.15 0.15 RO 11.1 11.1 11.0 10.9 10.9 10.9 10.6 9.7
B.sub.2O.sub.3 + P.sub.2O.sub.5 6.0 6.0 6.9 7.4 7.4 7.8 8.7 9.7
CaO/RO 1 1 1 1 0.91 1 0.93 0.92 SiO.sub.2--Al.sub.2O.sub.3/2 66.1
66.0 65.4 65.0 65.0 64.8 64.1 64.3 .beta.-OH 0.11 0.12 0.11 0.11
0.12 0.13 0.13 0.11 Properties devitrification 1233 1230 1213 1189
1206 1187 <1140 1151 temperature (.degree. C.) Tg (.degree. C.)
782 776 766 758 751 761 741 745 average coeffi- 34.2 34.0 32.9 32.6
33.1 33.2 36.3 29.6 cient of thermal expansion (.times.10.sup.-7)
(100-300.degree. C.) rate of heat 31 36 44 48 52 46 40 32 shrinkage
(ppm) density (g/cm.sup.3) 2.41 2.41 2.40 2.39 2.39 2.38 2.40 2.37
strain point (.degree. C.) 723 716 707 709 704 707 685 695 melting
1644 1632 1620 1608 1609 1610 1644 1650 temperature (.degree. C.)
liquidus viscosity 5.0 5.0 5.1 5.2 5.0 5.2 5.3 5.5 (log .eta.)
specific resistance 243 193 194 195 194 248 170 253 (.OMEGA. cm)
(1550.degree. C.) etching rate (.mu.m/h) 65 65 67 69 69 69 72 71
Examples 1-9 1-10 1-11 1-12 1-13 1-14 1-15 Compo- SiO.sub.2 67.2
66.7 69.7 67.5 67.3 67.8 66.9 sition B.sub.2O.sub.3 4.7 5.0 5.0 7.5
8.3 7.8 9.2 (mol %) Al.sub.2O.sub.3 12.5 13.2 12.2 12.9 12.7 12.5
12.2 K.sub.2O 0.17 0.17 0.17 0.20 0.17 0.17 0.17 MgO 6.9 7.4 5.8
CaO 1.7 1.3 1.42 11.7 11.5 11.5 11.4 SrO 6.8 6.2 5.7 BaO SnO.sub.2
0.09 0.09 0.09 0.10 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.02 0.02 0.02
0.02 (SiO.sub.2 + Al.sub.2O.sub.3)/ 17.0 16.0 16.4 10.7 9.7 10.3
8.6 B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 79.7 79.9 81.9 80.4
80.0 80.4 79.2 RO + B.sub.2O.sub.3 + 20.1 19.9 17.9 19.2 19.8 19.4
20.5 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.19 0.20 0.18 0.19 0.19 0.18
0.18 RO 15.4 14.9 12.9 11.7 11.5 11.5 11.4 B.sub.2O.sub.3 +
P.sub.2O.sub.5 4.7 5.0 5.0 7.5 8.3 7.8 9.2 CaO/RO 0.11 0.09 0.11 1
1 1 1 SiO.sub.2--Al.sub.2O.sub.3/2 61.0 60.1 63.6 61.1 61.0 61.6
60.8 .beta.-OH 0.13 0.13 0.14 0.12 0.11 0.11 0.10 Properties
devitrification 1241 1219 1215 1230 1220 1236 1193 temperature
(.degree. C.) Tg (.degree. C.) 749 764 768 763 754 760 741 average
coeffi- 39.8 36.4 33.6 36.0 35.9 36.0 36.1 cient of thermal
expansion (.times.10.sup.-7) (100-300.degree. C.) rate of heat 42
29 27 28 33 31 40 shrinkage (ppm) density (g/cm.sup.3) 2.58 2.55
2.52 2.40 2.41 2.42 2.40 strain point (.degree. C.) 694 712 711 712
702 710 695 melting 1532 1538 1553 1587 1582 1579 1567 temperature
(.degree. C.) liquidus viscosity 4.3 4.5 4.7 4.6 4.7 4.6 4.9 (log
.eta.) specific resistance 203 203 236 137 133 129 142 (.OMEGA. cm)
(1550.degree. C.) etching rate (.mu.m/h) 83 85 73 80 82 80 83
TABLE-US-00002 TABLE 1-2 Examples 1-16 1-17 1-18 1-19 1-20 1-21
1-22 1-23 1-24 Compo- SiO.sub.2 67.64 72.0 66.5 66.5 66.5 63.5 70.5
70.5 70.5 sition B.sub.2O.sub.3 7.83 6.4 9.5 9.5 4.5 4.5 7.4 7.4
7.4 (mol %) Al.sub.2O.sub.3 12.73 11.4 11.4 12.4 10.4 10.4 10.9
10.9 10.9 K.sub.2O 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 MgO
2.0 CaO 6.5 9.9 12.3 11.3 18.3 21.3 8.9 9.9 8.9 SrO 5 1.0 2.0 BaO
SnO.sub.2 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08
Fe.sub.2O.sub.3 0.022 0.022 0.022 0.022 0.022 0.022 0.022 0.022
0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/ 10.3 13.1 8.2 8.3 16.9 16.2
11.0 11.0 11.0 B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 80.4 83.4
77.9 78.9 76.9 73.9 81.4 81.4 81.4 RO + B.sub.2O.sub.3 + 19.4 16.3
21.8 20.8 22.8 25.8 18.3 18.3 18.3 ZnO Al.sub.2O.sub.3/SiO.sub.2
0.19 0.16 0.17 0.19 0.16 0.16 0.15 0.15 0.15 RO 11.5 9.9 12.3 11.3
18.3 21.3 10.9 10.9 10.9 B.sub.2O.sub.3 + P.sub.2O.sub.5 7.83 6.4
9.5 9.5 4.5 4.5 7.4 7.4 7.4 CaO/RO 0.57 1 1 1 1 1 0.82 0.91 0.82
SiO.sub.2--Al.sub.2O.sub.3/2 61.3 66.3 60.7 60.2 61.2 58.2 65.0
65.0 65.0 .beta.-OH 0.12 0.12 0.11 0.11 0.10 0.10 0.12 0.12 0.12
Properties devitrification 1221 1235 1196 1208 1228 1206 1201 1207
1200 temperature (.degree. C.) Tg (.degree. C.) 758 781 731 743 739
732 742 752 753 average coeffi- 38.2 33.3 37.2 36 46.8 50.9 30.4
35.0 35.8 cient of thermal expansion (.times.10.sup.-7)
(100-300.degree. C.) rate of heat 33 23 47 39 49 54 39 34 33
shrinkage (ppm) density (g/cm.sup.3) 2.48 2.38 2.40 2.40 2.50 2.55
2.38 2.41 2.42 strain point (.degree. C.) 703 731 681 693 689 682
695 702 703 melting 1595 1640 1554 1560 1548 1541 1614 1610 1608
temperature (.degree. C.) liquidus viscosity 4.8 4.9 4.7 4.6 4.3
4.4 5.1 5.0 5.1 (log .eta.) specific resistance 138 207 179 191 108
73 193 196 197 (.OMEGA. cm) (1550.degree. C.) etching rate
(.mu.m/h) 83 64 83 85 81 92 69 69 69 Comparative Examples 1-1 1-2
1-3 1-4 1-5 1-6 Compo- SiO.sub.2 71.7 71.7 66.4 67.64 67.64 67.64
sition B.sub.2O.sub.3 4.0 11.0 7.83 7.83 7.83 (mol %)
Al.sub.2O.sub.3 11.1 11.1 10.9 12.73 12.73 12.73 K.sub.2O 0.18 0.17
0.17 0.17 MgO 2.8 1 3 5 CaO 13.1 17.1 6.8 10.5 8.5 6.5 SrO 1.69 BaO
SnO.sub.2 0.08 0.09 0.09 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.03 0.022
0.022 0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/ 20.7 7.0 10.3 10.3 10.3
B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 82.8 82.8 77.4 80.4 80.4
80.4 RO + B.sub.2O.sub.3 + 17.1 17.1 22.3 19.4 19.4 19.4 ZnO
Al.sub.2O.sub.3/SiO.sub.2 0.15 0.15 0.16 0.19 0.19 0.19 RO 13.1
17.1 11.3 11.5 11.5 11.5 B.sub.2O.sub.3 + P.sub.2O.sub.5 4.0 11.0
7.83 7.83 7.83 CaO/RO 1 1 0.60 0.91 0.74 0.57
SiO.sub.2--Al.sub.2O.sub.3/2 66.1 66.1 61.0 61.3 61.3 61.3
.beta.-OH 0.13 0.11 0.11 0.11 0.11 0.12 Properties devitrification
1282 1330 1196 1260 1294 1324 temperature (.degree. C.) Tg
(.degree. C.) 786 826 707 758 749 746 average coeffi- 29.8 41.0
34.3 34.4 33.3 32.8 cient of thermal expansion (.times.10.sup.-7)
(100-300.degree. C.) rate of heat 17 13 114 32 37 38 shrinkage
(ppm) density (g/cm.sup.3) 2.445 2.510 2.40 2.41 2.40 2.40 strain
point (.degree. C.) 725 774 660 708 697 691 melting 1675 1701 1529
1585 1580 1577 temperature (.degree. C.) liquidus viscosity 4.7 4.4
4.6 4.4 4.2 4.0 (log .eta.) specific resistance 230 188 165 132 130
128 (.OMEGA. cm) (1550.degree. C.) etching rate (.mu.m/h) 65 65 82
83 81 79
[0263] The glass substrates of Examples 1-1 to 1-24 had a Tg of
720.degree. C. or more, and the rate of heat shrinkage and
devitrification temperature thereof satisfied the conditions of the
first glass substrate of the present invention. The glasses of
Examples 1-1 to 1-24 had a melting temperature of 1680.degree. C.
or less, i.e., good meltability. Therefore, the glass substrates of
Examples 1-1 to 1-24 have excellent properties and can be used in
displays to which the p-Si TFT is applied. On the other hand, the
ratios of heat shrinkage or devitrification temperatures of the
glasses of Comparative Examples 1-1 to 1-6 did not satisfy the
conditions of the first glass substrate of the present invention.
The melting temperature of the glass of Comparative Example 2
exceeded 1680.degree. C., i.e., good meltability was not obtained.
Thus, the glass substrates of Comparative Examples 1-1 to 1-6 were
not suitable for displays to which the p-Si TFT is applied.
Example 1-25
[0264] A glass material prepared to have a composition shown in
Example 1-4 was melted at 1560-1640.degree. C., followed by
refining at 1620-1670.degree. C. and then stirring at
1440-1530.degree. C., using continuous melting equipment including
a melting bath of fire bricks and a refining bath (adjustment bath)
of a platinum alloy. Thereafter, the glass material was formed into
a thin plate having a thickness of 0.7 mm by the overflow downdraw
process, followed by cooling at an average rate of 100.degree.
C./min within the temperature range of Tg.degree. C. to
Tg-100.degree. C., thereby obtaining a glass substrate for liquid
crystal displays (or organic EL displays). Note that the
aforementioned properties of the obtained glass substrate were
measured. Note that, for properties (density, strain point,
expansion coefficient, and Tg) which cannot be measured in the form
of a substrate, the glass substrate was melted again to produce a
sample glass according to the aforementioned sample production
process, and the properties of the sample glass were measured.
[0265] The glass substrate of Example 1-25 thus obtained had a
melting temperature of 1610.degree. C., a .beta.-OH value of 0.20
mm.sup.-1, a Tg of 754.degree. C., a strain point of 697.degree.
C., and a heat shrinkage rate of 51 ppm, and the other properties
thereof were similar to those of Example 1-4. Thus, the glass
substrate of Example 1-25 had a Tg of 720.degree. C. or more and a
melting temperature of 1680.degree. C. or less, i.e., a high Tg and
strain point and good meltability. Moreover, the rate of heat
shrinkage and devitrification temperature satisfied the conditions
of the first glass substrate of the present invention. Note that
the glass substrate of Example 1-25 has a .beta.-OH value which is
greater than that of Example 1-4 by about 0.1 mm.sup.-1, and
therefore, has a Tg which is lower than that of Example 1-4 by
2-3.degree. C., and the Tg is still sufficiently high. Therefore,
the glass substrate of Example 1-25 has excellent properties and
can be used in displays to which the p-Si TFT is applied.
Example 1-26
[0266] A glass substrate was produced using a glass material
prepared to have a glass composition shown in Example 1-12 in a
manner similar to that of Example 1-25, and the properties of the
glass substrate were measured.
[0267] The glass substrate of Example 1-26 thus obtained had a
melting temperature of 1585.degree. C., a .beta.-OH value of 0.21
mm.sup.-1, a Tg of 761.degree. C., a strain point of 710.degree.
C., and a heat shrinkage rate of 31 ppm, and the other properties
thereof were similar to those of Example 1-12. Thus, the glass
substrate of Example 1-26 had a Tg of 720.degree. C. or more and a
melting temperature of 1680.degree. C. or less, i.e., a high Tg and
strain point and good meltability. Moreover, the rate of heat
shrinkage and devitrification temperature satisfied the conditions
of the first glass substrate of the present invention. Note that
the glass substrate of Example 1-26 has a .beta.-OH value which is
greater than that of Example 1-12 by about 0.1 mm.sup.-1, and
therefore, has a Tg which is lower than that of Example 1-12 by
2-3.degree. C., and the Tg is still sufficiently high. Therefore,
the glass substrate of Example 1-26 has excellent properties and
can be used in displays to which the p-Si TFT is applied.
[0268] <Second Glass Substrate>
[0269] The second glass substrate will be described by way of
example. Note that the second glass substrate includes a glass
comprising, as expressed in mol %;
[0270] 55-80% SiO.sub.2;
[0271] 3-20% Al.sub.2O.sub.3;
[0272] 3-15% B.sub.2O.sub.3; and
[0273] 3-25% RO (the total amount of MgO, CaO, SrO, and BaO)
wherein
[0274] in the glass the contents in mol % of SiO.sub.2,
Al.sub.2O.sub.3, and B.sub.2O.sub.3 satisfy a relationship
(SiO.sub.2+Al.sub.2O.sub.3)/(B.sub.2O.sub.3)=8.45-17.0, and
[0275] the devitrification temperature of the glass is 1250.degree.
C. or less, and
[0276] the rate of heat shrinkage is 60 ppm or less.
[0277] Examples and comparative examples of the sample glass having
glass compositions shown in Tables 2-1 and 2-2 were produced in a
manner similar to that of the examples and comparative examples of
the first glass substrate, and the properties thereof were
measured.
TABLE-US-00003 TABLE 2-1 Examples 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
Compo- SiO.sub.2 71.7 71.6 70.8 70.5 70.5 70.3 69.4 67.2 sition
B.sub.2O.sub.3 6.0 6.0 6.9 7.4 7.4 7.8 8.7 4.7 (mol %)
Al.sub.2O.sub.3 11.1 11.1 11.0 10.9 10.9 10.9 10.8 12.5 K.sub.2O
0.17 0.17 0.17 0.17 0.40 0.17 MgO 1.0 6.9 CaO 11.1 11.1 11.0 10.9
9.9 10.9 9.8 1.7 SrO 0.8 6.8 BaO SnO.sub.2 0.08 0.08 0.08 0.08 0.08
0.08 0.08 0.09 Fe.sub.2O.sub.3 0.022 0.022 0.022 0.022 (SiO.sub.2 +
Al.sub.2O.sub.3)/ 13.8 13.8 11.8 11.0 11.0 10.3 9.2 17.0
B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 82.8 82.6 81.8 81.4 81.4
81.2 80.2 79.7 RO + B.sub.2O.sub.3 + 17.1 17.1 17.9 18.3 18.3 18.7
19.3 20.1 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.15 0.15 0.15 0.15 0.15
0.15 0.15 0.19 RO 11.1 11.1 11.0 10.9 10.9 10.9 10.6 15.4
B.sub.2O.sub.3 + P.sub.2O.sub.5 6.0 6.0 6.9 7.4 7.4 7.8 8.7 4.7
CaO/RO 1 1 1 1 0.91 1 0.93 0.11 SiO.sub.2--Al.sub.2O.sub.3/2 66.1
66.0 65.4 65.0 65.0 64.8 64.1 61.0 .beta.-OH 0.11 0.12 0.11 0.11
0.12 0.13 0.13 0.13 Properties devitrification 1233 1230 1213 1189
1206 1187 <1140 1241 temperature (.degree. C.) Tg (.degree. C.)
782 776 766 758 751 761 741 749 average coeffi- 34.2 34.0 32.9 32.6
33.1 33.2 36.3 39.8 cient of thermal expansion (.times.10.sup.-7)
(100-300.degree. C.) rate of heat 31 36 44 48 52 46 40 42 shrinkage
(ppm) density (g/cm.sup.3) 2.41 2.41 2.40 2.39 2.39 2.38 2.40 2.58
strain point (.degree. C.) 723 716 707 709 704 707 685 694 melting
1644 1632 1620 1608 1609 1610 1644 1532 temperature (.degree. C.)
liquidus viscosity 5.0 5.0 5.1 5.2 5.0 5.2 5.3 4.3 (log .eta.)
specific resistance 243 193 194 195 194 248 170 203 (.OMEGA. cm)
(1550.degree. C.) etching rate (.mu.m/h) 65 65 67 69 69 69 72 83
Examples 2-9 2-10 2-11 2-12 2-13 2-14 2-15 Compo- SiO.sub.2 66.7
69.7 67.5 67.3 67.8 66.9 67.64 sition B.sub.2O.sub.3 5.0 5.0 7.5
8.3 7.8 9.2 7.83 (mol %) Al.sub.2O.sub.3 13.2 12.2 12.9 12.7 12.5
12.2 12.73 K.sub.2O 0.17 0.17 0.20 0.17 0.17 0.17 0.17 MgO 7.4 5.8
CaO 1.3 1.42 11.7 11.5 11.5 11.4 6.5 SrO 6.2 5.7 5 BaO SnO.sub.2
0.09 0.09 0.10 0.08 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.02 0.02 0.02
0.02 0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/ 16.0 16.4 10.7 9.7 10.3
8.6 10.3 B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 79.9 81.9 80.4
80.0 80.4 79.2 80.4 RO + B.sub.2O.sub.3 + 19.9 17.9 19.2 19.8 19.4
20.5 19.4 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.20 0.18 0.19 0.19 0.18
0.18 0.19 RO 14.9 12.9 11.7 11.5 11.5 11.4 11.5 B.sub.2O.sub.3 +
P.sub.2O.sub.5 5.0 5.0 7.5 8.3 7.8 9.2 7.83 CaO/RO 0.09 0.11 1 1 1
1 0.57 SiO.sub.2--Al.sub.2O.sub.3/2 60.1 63.6 61.1 61.0 61.6 60.8
61.3 .beta.-OH 0.13 0.14 0.12 0.11 0.11 0.10 0.12 Properties
devitrification 1219 1215 1230 1220 1236 1193 1221 temperature
(.degree. C.) Tg (.degree. C.) 764 768 763 754 760 741 758 average
coeffi- 36.4 33.6 36.0 35.9 36.0 36.1 38.2 cient of thermal
expansion (.times.10.sup.-7) (100-300.degree. C.) rate of heat 29
27 28 33 31 40 33 shrinkage (ppm) density (g/cm.sup.3) 2.55 2.52
2.40 2.41 2.42 2.40 2.48 strain point (.degree. C.) 712 711 712 702
710 695 703 melting 1538 1553 1587 1582 1579 1567 1595 temperature
(.degree. C.) liquidus viscosity 4.5 4.7 4.6 4.7 4.6 4.9 4.8 (log
.eta.) specific resistance 203 236 137 133 129 142 138 (.OMEGA. cm)
(1550.degree. C.) etching rate (.mu.m/h) 85 73 80 82 80 83 83
TABLE-US-00004 TABLE 2-2 Examples 2-16 2-17 2-18 2-19 2-20 2-21
2-22 2-23 Compo- SiO.sub.2 72.0 66.5 66.5 66.5 63.5 70.5 70.5 70.5
sition B.sub.2O.sub.3 6.4 9.5 9.5 4.5 4.5 7.4 7.4 7.4 (mol %)
Al.sub.2O.sub.3 11.4 11.4 12.4 10.4 10.4 10.9 10.9 10.9 K.sub.2O
0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 MgO 2.0 CaO 9.9 12.3 11.3
18.3 21.3 8.9 9.9 8.9 SrO 1.0 2.0 BaO SnO.sub.2 0.08 0.08 0.08 0.08
0.08 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.022 0.022 0.022 0.022 0.022
0.022 0.022 0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/ 13.1 8.2 8.3 16.9
16.2 11.0 11.0 11.0 B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 83.4
77.9 78.9 76.9 73.9 81.4 81.4 81.4 RO + B.sub.2O.sub.3 + 16.3 21.8
20.8 22.8 25.8 18.3 18.3 18.3 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.16
0.17 0.19 0.16 0.16 0.15 0.15 0.15 RO 9.9 12.3 11.3 18.3 21.3 10.9
10.9 10.9 B.sub.2O.sub.3 + P.sub.2O.sub.5 6.4 9.5 9.5 4.5 4.5 7.4
7.4 7.4 CaO/RO 1 1 1 1 1 0.82 0.91 0.82
SiO.sub.2--Al.sub.2O.sub.3/2 66.3 60.7 60.2 61.2 58.2 65.0 65.0
65.0 .beta.-OH 0.12 0.11 0.11 0.10 0.10 0.12 0.12 0.12 Properties
devitrification 1235 1196 1208 1228 1206 1201 1207 1200 temperature
(.degree. C.) Tg (.degree. C.) 781 731 743 739 732 742 752 753
average coeffi- 33.3 37.2 36 46.8 50.9 30.4 35.0 35.8 cient of
thermal expansion (.times.10.sup.-7) (100-300.degree. C.) rate of
heat 23 47 39 49 54 39 34 33 shrinkage (ppm) density (g/cm.sup.3)
2.38 2.40 2.40 2.50 2.55 2.38 2.41 2.42 strain point (.degree. C.)
731 681 693 689 682 695 702 703 melting 1640 1554 1560 1548 1541
1614 1610 1608 temperature (.degree. C.) liquidus viscosity 4.9 4.7
4.6 4.3 4.4 5.1 5.0 5.1 (log .eta.) specific resistance 207 179 191
108 73 193 196 197 (.OMEGA. cm) (1550.degree. C.) etching rate
(.mu.m/h) 64 83 85 81 92 69 69 69 Comparative Examples 2-1 2-2 2-3
2-4 2-5 2-6 Compo- SiO.sub.2 71.7 71.7 66.4 67.64 67.64 67.64
sition B.sub.2O.sub.3 4.0 11.0 7.83 7.83 7.83 (mol %)
Al.sub.2O.sub.3 11.1 11.1 10.9 12.73 12.73 12.73 K.sub.2O 0.18 0.17
0.17 0.17 MgO 2.8 1 3 5 CaO 13.1 17.1 6.8 10.5 8.5 6.5 SrO 1.69 BaO
SnO.sub.2 0.08 0.09 0.09 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.03 0.022
0.022 0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/ 20.7 7.0 10.3 10.3 10.3
B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 82.8 82.8 77.4 80.4 80.4
80.4 RO + B.sub.2O.sub.3 + 17.1 17.1 22.3 19.4 19.4 19.4 ZnO
Al.sub.2O.sub.3/SiO.sub.2 0.15 0.15 0.16 0.19 0.19 0.19 RO 13.1
17.1 11.3 11.5 11.5 11.5 B.sub.2O.sub.3 + P.sub.2O.sub.5 4.0 11.0
7.83 7.83 7.83 CaO/RO 1 1 0.60 0.91 0.74 0.57
SiO.sub.2--Al.sub.2O.sub.3/2 66.1 66.1 61.0 61.3 61.3 61.3
.beta.-OH 0.13 0.11 0.11 0.11 0.11 0.12 Properties devitrification
1282 1330 1196 1260 1294 1324 temperature (.degree. C.) Tg
(.degree. C.) 786 826 707 758 749 746 average coeffi- 29.8 41.0
34.3 34.4 33.3 32.8 cient of thermal expansion (.times.10.sup.-7)
(100-300.degree. C.) rate of heat 17 13 114 32 37 38 shrinkage
(ppm) density (g/cm.sup.3) 2.445 2.510 2.40 2.41 2.40 2.40 strain
point (.degree. C.) 725 774 660 708 697 691 melting 1675 1701 1529
1585 1580 1577 temperature (.degree. C.) liquidus viscosity 4.7 4.4
4.6 4.4 4.2 4.0 (log .eta.) specific resistance 230 188 165 132 130
128 (.OMEGA. cm) (1550.degree. C.) etching rate (.mu.m/h) 65 65 82
83 81 79
[0278] <Third Glass Substrate>
[0279] The third glass substrate will be described by way of
example. Note that the third glass substrate includes a glass
comprising, as expressed in mol %,
[0280] 65-78% SiO.sub.2
[0281] 3-20% Al.sub.2O.sub.3
[0282] 3-15% B.sub.2O.sub.3
[0283] 0% to less than 2% MgO
[0284] 3.6-16% CaO
[0285] 0-2% SrO
[0286] 0% to less than 1% BaO
where
[0287] the contents in mol % of B.sub.2O.sub.3, P.sub.2O.sub.5, and
CaO satisfy relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-15% and
CaO/B.sub.2O.sub.3>1.2,
[0288] the strain point of the glass is 665.degree. C. or more,
and
[0289] the devitrification temperature of the glass is 1250.degree.
C. or less.
[0290] Examples and comparative examples of the sample glass having
glass compositions shown in Table 3 were produced in a manner
similar to that of the examples and comparative examples of the
first glass substrate, and the properties thereof were
measured.
TABLE-US-00005 TABLE 3 Examples 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9
3-10 3-11 Compo- SiO.sub.2 71.7 71.6 70.8 70.5 70.5 70.3 67.5 67.3
67.8 66.9 72.0 sition B.sub.2O.sub.3 6.0 6.0 6.9 7.4 7.4 7.8 7.5
8.3 7.8 9.2 6.4 (mol %) Al.sub.2O.sub.3 11.1 11.1 11.0 10.9 10.9
10.9 12.9 12.7 12.5 12.2 11.4 K.sub.2O 0.17 0.17 0.17 0.17 0.20
0.17 0.17 0.17 0.17 MgO 1.0 CaO 11.1 11.1 11.0 10.9 9.9 10.9 11.7
11.5 11.5 11.4 9.9 SrO BaO SnO.sub.2 0.08 0.08 0.08 0.08 0.08 0.08
0.10 0.08 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.022 0.022 0.022 0.022
0.02 0.02 0.02 0.02 0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/ 13.8 13.8
11.8 11.0 11.0 10.3 10.7 9.7 10.3 8.6 13.1 B.sub.2O.sub.3 SiO.sub.2
+ Al.sub.2O.sub.3 82.8 82.6 81.8 81.4 81.4 81.2 80.4 80.0 80.4 79.2
83.4 RO + B.sub.2O.sub.3 + 17.1 17.1 17.9 18.3 18.3 18.7 19.2 19.8
19.4 20.5 16.3 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.15 0.15 0.15 0.15
0.15 0.15 0.19 0.19 0.18 0.18 0.16 RO 11.1 11.1 11.0 10.9 10.9 10.9
11.7 11.5 11.5 11.4 9.9 B.sub.2O.sub.3 + P.sub.2O.sub.5 6.0 6.0 6.9
7.4 7.4 7.8 7.5 8.3 7.8 9.2 6.4 CaO/RO 1 1 1 1 0.91 1 1 1 1 1 1
SiO.sub.2--Al.sub.2O.sub.3/2 66.1 66.0 65.4 65.0 65.0 64.8 61.1
61.0 61.6 60.8 66.3 .beta.-OH 0.11 0.12 0.11 0.11 0.12 0.13 0.12
0.11 0.11 0.10 0.12 Properties devitrification 1233 1230 1213 1189
1206 1187 1230 1220 1236 1193 1235 temperature (.degree. C.) Tg
(.degree. C.) 782 776 766 758 751 761 763 754 760 741 781 average
coeffi- 34.2 34.0 32.9 32.6 33.1 33.2 36.0 35.9 36.0 36.1 33.3
cient of thermal expansion (.times.10.sup.-7) (100-300.degree. C.)
rate of heat 31 36 44 48 52 46 28 33 31 40 23 shrinkage (ppm)
density (g/cm.sup.3) 2.41 2.41 2.40 2.39 2.39 2.38 2.40 2.41 2.42
2.40 2.38 strain point (.degree. C.) 723 716 707 709 704 707 712
702 710 695 731 melting 1644 1632 1620 1608 1609 1610 1587 1582
1579 1567 1640 temperature (.degree. C.) liquidus viscosity 5.0 5.0
5.1 5.2 5.0 5.2 4.6 4.7 4.6 4.9 4.9 (log .eta.) specific resistance
243 193 194 195 194 248 137 133 129 142 207 (.OMEGA. cm)
(1550.degree. C.) etching rate (.mu.m/h) 65 65 67 69 69 69 80 82 80
83 64 Examples Comparative Examples 3-12 3-13 3-14 3-1 3-2 3-3 3-4
3-5 3-6 Compo- SiO.sub.2 66.5 70.5 70.5 71.7 71.7 66.4 67.64 67.64
67.64 sition B.sub.2O.sub.3 9.5 7.4 7.4 4.0 11.0 7.83 7.83 7.83
(mol %) Al.sub.2O.sub.3 11.4 10.9 10.9 11.1 11.1 10.9 12.73 12.73
12.73 K.sub.2O 0.17 0.17 0.17 0.18 0.17 0.17 0.17 MgO 2.8 1 3 5 CaO
12.3 9.9 8.9 13.1 17.1 6.8 10.5 8.5 6.5 SrO 1.0 2.0 1.69 BaO
SnO.sub.2 0.08 0.08 0.08 0.08 0.09 0.09 0.08 0.08 0.08
Fe.sub.2O.sub.3 0.022 0.022 0.022 0.03 0.022 0.022 0.022 (SiO.sub.2
+ Al.sub.2O.sub.3)/ 8.2 11.0 11.0 20.7 7.0 10.3 10.3 10.3
B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 77.9 81.4 81.4 82.8 82.8
77.4 80.4 80.4 80.4 RO + B.sub.2O.sub.3 + 21.8 18.3 18.3 17.1 17.1
22.3 19.4 19.4 19.4 ZnO Al.sub.2O.sub.3/SiO.sub.2 0.17 0.15 0.15
0.15 0.15 0.16 0.19 0.19 0.19 RO 12.3 10.9 10.9 13.1 17.1 11.3 11.5
11.5 11.5 B.sub.2O.sub.3 + P.sub.2O.sub.5 9.5 7.4 7.4 4.0 11.0 7.83
7.83 7.83 CaO/RO 1 0.91 0.82 1 1 0.60 0.91 0.74 0.57
SiO.sub.2--Al.sub.2O.sub.3/2 60.7 65.0 65.0 66.1 66.1 61.0 61.3
61.3 61.3 .beta.-OH 0.11 0.12 0.12 0.13 0.11 0.11 0.11 0.11 0.12
Properties devitrification 1196 1207 1200 1282 1330 1196 1260 1294
1324 temperature (.degree. C.) Tg (.degree. C.) 731 752 753 786 826
707 758 749 746 average coeffi- 37.2 35.0 35.8 29.8 41.0 34.3 34.4
33.3 32.8 cient of thermal expansion (.times.10.sup.-7)
(100-300.degree. C.) rate of heat 47 34 33 17 13 114 32 37 38
shrinkage (ppm) density (g/cm.sup.3) 2.40 2.41 2.42 2.445 2.510
2.40 2.41 2.40 2.40 strain point (.degree. C.) 681 702 703 725 774
660 708 697 691 melting 1554 1610 1608 1675 1701 1529 1585 1580
1577 temperature (.degree. C.) liquidus viscosity 4.7 5.0 5.1 4.7
4.4 4.6 4.4 4.2 4.0 (log .eta.) specific resistance 179 196 197 230
188 165 132 130 128 (.OMEGA. cm) (1550.degree. C.) etching rate
(.mu.m/h) 83 69 69 65 65 82 83 81 79
[0291] <Fourth Glass Substrate>
[0292] The fourth glass substrate will be described by way of
example. Note that the fourth glass substrate includes a glass
comprising, as expressed in mol %,
[0293] 65-78% SiO.sub.2
[0294] 3-20% Al.sub.2O.sub.3
[0295] 3-9.5% B.sub.2O.sub.3
[0296] 0% to less than 2% MgO
[0297] 3.6-16% CaO
[0298] 0-2% SrO
[0299] substantially no BaO
where
[0300] the contents in mol % of B.sub.2O.sub.3, P.sub.2O.sub.5, and
CaO satisfy relationships B.sub.2O.sub.3+P.sub.2O.sub.5=3-9.5% and
CaO/B.sub.2O.sub.3>1.2, and the devitrification temperature of
the glass is 1250.degree. C. or less.
[0301] Examples and comparative examples of the sample glass having
glass compositions shown in Table 4 were produced in a manner
similar to that of the examples and comparative examples of the
first glass substrate, and the properties thereof were
measured.
TABLE-US-00006 TABLE 4 Examples 4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9
4-10 Compo- SiO.sub.2 71.7 71.6 70.8 70.5 70.5 70.3 67.5 67.3 67.8
66.9 sition B.sub.2O.sub.3 6.0 6.0 6.9 7.4 7.4 7.8 7.5 8.3 7.8 9.2
(mol %) Al.sub.2O.sub.3 11.1 11.1 11.0 10.9 10.9 10.9 12.9 12.7
12.5 12.2 K.sub.2O 0.17 0.17 0.17 0.17 0.20 0.17 0.17 0.17 MgO 1.0
CaO 11.1 11.1 11.0 10.9 9.9 10.9 11.7 11.5 11.5 11.4 SrO BaO
SnO.sub.2 0.08 0.08 0.08 0.08 0.08 0.08 0.10 0.08 0.08 0.08
Fe.sub.2O.sub.3 0.022 0.022 0.022 0.022 0.02 0.02 0.02 0.02
(SiO.sub.2 + Al.sub.2O.sub.3)/ 13.8 13.8 11.8 11.0 11.0 10.3 10.7
9.7 10.3 8.6 B.sub.2O.sub.3 SiO.sub.2 + Al.sub.2O.sub.3 82.8 82.6
81.8 81.4 81.4 81.2 80.4 80.0 80.4 79.2 RO + B.sub.2O.sub.3 + 17.1
17.1 17.9 18.3 18.3 18.7 19.2 19.8 19.4 20.5 ZnO
Al.sub.2O.sub.3/SiO.sub.2 0.15 0.15 0.15 0.15 0.15 0.15 0.19 0.19
0.18 0.18 RO 11.1 11.1 11.0 10.9 10.9 10.9 11.7 11.5 11.5 11.4
B.sub.2O.sub.3 + P.sub.2O.sub.5 6.0 6.0 6.9 7.4 7.4 7.8 7.5 8.3 7.8
9.2 CaO/RO 1 1 1 1 0.91 1 1 1 1 1 SiO.sub.2--Al.sub.2O.sub.3/2 66.1
66.0 65.4 65.0 65.0 64.8 61.1 61.0 61.6 60.8 .beta.-OH 0.11 0.12
0.11 0.11 0.12 0.13 0.12 0.11 0.11 0.10 Properties devitrification
1233 1230 1213 1189 1206 1187 1230 1220 1236 1193 temperature
(.degree. C.) Tg (.degree. C.) 782 776 766 758 751 761 763 754 760
741 average coeffi- 34.2 34.0 32.9 32.6 33.1 33.2 36.0 35.9 36.0
36.1 cient of thermal expansion (.times.10.sup.-7) (100-300.degree.
C.) rate of heat 31 36 44 48 52 46 28 33 31 40 shrinkage (ppm)
density (g/cm.sup.3) 2.41 2.41 2.40 2.39 2.39 2.38 2.40 2.41 2.42
2.40 strain point (.degree. C.) 723 716 707 709 704 707 712 702 710
695 melting 1644 1632 1620 1608 1609 1610 1587 1582 1579 1567
temperature (.degree. C.) liquidus viscosity 5.0 5.0 5.1 5.2 5.0
5.2 4.6 4.7 4.6 4.9 (log .eta.) specific resistance 243 193 194 195
194 248 137 133 129 142 (.OMEGA. cm) (1550.degree. C.) etching rate
(.mu.m/h) 65 65 67 69 69 69 80 82 80 83 Examples Comparative
Examples 4-11 4-12 4-13 4-1 4-2 4-3 4-4 4-5 4-6 Compo- SiO.sub.2
72.0 70.5 70.5 71.7 71.7 66.4 67.64 67.64 67.64 sition
B.sub.2O.sub.3 6.4 7.4 7.4 4.0 11.0 7.83 7.83 7.83 (mol %)
Al.sub.2O.sub.3 11.4 10.9 10.9 11.1 11.1 10.9 12.73 12.73 12.73
K.sub.2O 0.17 0.17 0.17 0.18 0.17 0.17 0.17 MgO 2.8 1 3 5 CaO 9.9
9.9 8.9 13.1 17.1 6.8 10.5 8.5 6.5 SrO 1.0 2.0 1.69 BaO SnO.sub.2
0.08 0.08 0.08 0.08 0.09 0.09 0.08 0.08 0.08 Fe.sub.2O.sub.3 0.022
0.022 0.022 0.03 0.022 0.022 0.022 (SiO.sub.2 + Al.sub.2O.sub.3)/
13.1 11.0 11.0 20.7 7.0 10.3 10.3 10.3 B.sub.2O.sub.3 SiO.sub.2 +
Al.sub.2O.sub.3 83.4 81.4 81.4 82.8 82.8 77.4 80.4 80.4 80.4 RO +
B.sub.2O.sub.3 + 16.3 18.3 18.3 17.1 17.1 22.3 19.4 19.4 19.4 ZnO
Al.sub.2O.sub.3/SiO.sub.2 0.16 0.15 0.15 0.15 0.15 0.16 0.19 0.19
0.19 RO 9.9 10.9 10.9 13.1 17.1 11.3 11.5 11.5 11.5 B.sub.2O.sub.3
+ P.sub.2O.sub.5 6.4 7.4 7.4 4.0 11.0 7.83 7.83 7.83 CaO/RO 1 0.91
0.82 1 1 0.60 0.91 0.74 0.57 SiO.sub.2--Al.sub.2O.sub.3/2 66.3 65.0
65.0 66.1 66.1 61.0 61.3 61.3 61.3 .beta.-OH 0.12 0.12 0.12 0.13
0.11 0.11 0.11 0.11 0.12 Properties devitrification 1235 1207 1200
1282 1330 1196 1260 1294 1324 temperature (.degree. C.) Tg
(.degree. C.) 781 752 753 786 826 707 758 749 746 average coeffi-
33.3 35.0 35.8 29.8 41.0 34.3 34.4 33.3 32.8 cient of thermal
expansion (.times.10.sup.-7) (100-300.degree. C.) rate of heat 23
34 33 17 13 114 32 37 38 shrinkage (ppm) density (g/cm.sup.3) 2.38
2.41 2.42 2.445 2.510 2.40 2.41 2.40 2.40 strain point (.degree.
C.) 731 702 703 725 774 660 708 697 691 melting 1640 1610 1608 1675
1701 1529 1585 1580 1577 temperature (.degree. C.) liquidus
viscosity 4.9 5.0 5.1 4.7 4.4 4.6 4.4 4.2 4.0 (log .eta.) specific
resistance 207 196 197 230 188 165 132 130 128 (.OMEGA. cm)
(1550.degree. C.) etching rate (.mu.m/h) 64 69 69 65 65 82 83 81
79
[0302] The flat panel display glass substrate of the present
invention is suitable for flat panel displays in which the p-Si is
used, and is particularly suitable as a glass substrate for liquid
crystal displays and organic EL displays in which the p-Si TFT is
used. The flat panel display glass substrate of the present
invention is suitable as a display glass substrate for mobile
terminals for which a high resolution is required, among other
things.
[0303] Note that the specific embodiments or examples described in
the "DETAILED DESCRIPTION OF THE INVENTION" section are only for
the purpose of illustrating the technical aspects of the present
invention, and are not to be construed in a narrow sense by
limiting the present invention to such specific examples. Various
changes and modifications can be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
* * * * *