U.S. patent number RE37,920 [Application Number 09/060,741] was granted by the patent office on 2002-12-03 for flat panel display.
This patent grant is currently assigned to Corning Incorporated. Invention is credited to Dawne M. Moffatt, Dean V. Neubauer.
United States Patent |
RE37,920 |
Moffatt , et al. |
December 3, 2002 |
Flat panel display
Abstract
A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 20 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 31-57.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, 49-67%
SiO.sub.2, at least 6% Al.sub.2 O.sub.3, the Al.sub.2 O.sub.3 being
6-14% in conjunction with 55-67% SiO.sub.2 and 16-23% in
conjunction with 49-58% SiO.sub.2, SiO.sub.2 +Al.sub.2 O.sub.3
>68%, 0-15% B.sub.2 O.sub.3, at least one alkaline earth metal
oxide selected from the group consisting of, in the proportions
indicated, 0-21% BaO, 0-15% SrO, 0-18% CaO, 0-8% MgO and 12-30%
BaO+CaO+SrO+MgO.
Inventors: |
Moffatt; Dawne M. (Corning,
NY), Neubauer; Dean V. (Horseheads, NY) |
Assignee: |
Corning Incorporated (Corning,
NY)
|
Family
ID: |
26906721 |
Appl.
No.: |
09/060,741 |
Filed: |
April 15, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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212060 |
Mar 14, 1994 |
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Reissue of: |
288300 |
Aug 10, 1994 |
05508237 |
Apr 16, 1996 |
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Current U.S.
Class: |
501/69; 501/66;
501/70; 65/99.2 |
Current CPC
Class: |
C03C
3/085 (20130101); C03C 3/091 (20130101); G02F
1/133337 (20210101) |
Current International
Class: |
C03C
3/085 (20060101); C03C 3/076 (20060101); C03C
3/091 (20060101); G02F 1/1333 (20060101); G02F
1/13 (20060101); C03C 003/078 (); C03C
003/091 () |
Field of
Search: |
;501/66,69,70
;65/90,99.2 |
References Cited
[Referenced By]
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3496401 |
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Dumbaugh, Jr. |
3978362 |
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Dumbaugh, Jr. et al. |
4012263 |
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4180618 |
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4255198 |
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Dumbaugh, Jr. |
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Dumbaugh, Jr. |
4441051 |
April 1984 |
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4634683 |
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Imai et al. |
5116787 |
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5348916 |
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5374595 |
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February 1995 |
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5489558 |
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EP |
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EP |
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2675795 |
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Oct 1992 |
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FR |
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62-7874 |
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Jul 1988 |
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JP |
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63-283710 |
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Nov 1988 |
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JP |
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63-221315 |
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1992-175242 |
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Jun 1992 |
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JP |
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Primary Examiner: Group; Karl
Attorney, Agent or Firm: Nixon Peabody LLP
Parent Case Text
This application is a Continuation-In-Part of U.S. Ser. No.
08/212,060, filed Mar. 14, 1994, now abandoned.
Claims
We claim: .[.
1. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 2.5 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 31-57.times.10.sup.-7 /.degree.C., is nominally free of
alkali metal oxides and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, 49-67%
SiO.sub.2, at least 6% Al.sub.2 O.sub.3, and Al.sub.2 O.sub.3 being
6-14% in conjunction with 55-67% SiO.sub.2 and 16-23% in
conjunction with 49-58% SiO.sub.2, SiO.sub.2 +Al.sub.2 O.sub.3
>68%, 0 to less than 8% B.sub.2 O.sub.3, at least one alkaline
earth metal oxide selected from the group consisting of, in the
proportions indicated, 0-21% BaO, 0-15% SrO, 0-7.1% CaO, 0-8% MgO
and 12-30% BaO+CaO+SrO+MgO..]..[.
2. A flat panel display in accordance with claim 1 in which the
glass panel has a CTE in the range of 31-44.times.10.sup.-7
/.degree.C. and the glass is selected from a group of
aluminosilicate sub-families consisting of glasses having
compositions consisting essentially of, as calculated in weight
percent on an oxide basis; a. 49-58% SiO.sub.2, 17.5-23% Al.sub.2
O.sub.3, 0 to less than 8% B.sub.2 O.sub.3, 0-8% MgO, 0-7.1% CaO,
0.4-13.5% SrO, 0-21% BaO and MgO+CaO+SrO+BaO being 13-28%, b.
57-66% SiO.sub.2, 8-14% Al.sub.2 O.sub.3, 0 to less than 8% B.sub.2
O.sub.3, 0-4.5% MgO, 0-7.1% CaO, 0.5-13% SrO and 2-21% BaO..].
.[.
3. A flat panel display in accordance with claim 2 in which the
glass panel has a CTE in the range of 32-40.times.10.sup.-7
/.degree.C. and the aluminosilicate sub-families consist
essentially of: a. 54-57% SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 5
to less than 8% B.sub.2 O.sub.3, 2-2.75% MgO, 1.5- <7% CaO, 2-6%
SrO and 0.5-9.5% BaO, b. 57-65.5% SiO.sub.2, 8-13% Al.sub.2
O.sub.3, 4 to less than 8% B.sub.2 O.sub.3, 2-3.5% MgO, 0-6.5% CaO,
0-13% SrO and 2-21% BaO..]. .[.
4. A flat panel display in accordance with claim 1 in which the
glass panel has a CTE in the range of 44-57.times.10.sup.-7
/.degree.C. and the glass is selected from a group of
aluminosilicate sub-families consisting of glasses having
compositions consisting essentially of, as calculated in weight
percent on an oxide basis: a. 50-57% SiO.sub.2, 16-22% Al.sub.2
O.sub.3, 0-5.5% B.sub.2 O.sub.3, 0.5-3% MgO, 1-7.1% CaO, 0.5-15%
SrO and 1-21% BaO, b. 55-67% SiO.sub.2, 6-14% Al.sub.2 O.sub.3,
0-7.5% B.sub.2 O.sub.3, 0-6.5% MgO, 0-7.1% CaO, 0-15.5% SrO, 1-9.5%
BaO and MgO+CaO+SrO+BaO being 16.5- 28%..]. .[.
5. A flat panel display in accordance with claim 4 in which the
glass panel has a CTE in the range of 45-50.times.10.sup.-7
/.degree.C. and the aluminosilicate sub-families consist
essentially of: a. 50-57% SiO.sub.2, 16-20% Al.sub.2 O.sub.3,
0-5.5% B.sub.2 O.sub.3, 2-2.75% MgO, 1-<7% CaO, 0.5-15% SrO and
1-21% BaO, b. 55-67% SiO.sub.2, 6-<13% Al.sub.2 O.sub.3, 0-7.5%
B.sub.2 O.sub.3, 2-6.5% MgO, 0-7.1% CaO, 0-14.5% SrO and 2-9.5%
BaO..]. .[.
6. A flat panel display in accordance with claim 1 in which the
glass panel has a strain point greater than 660.degree. C. and a
weight loss less than 1 mg/cm.sup.2 after immersion for 24 hours in
an aqueous 5% by weight HCl solution at 95.degree. C., the glass
being selected from a group of aluminosilicate sub-families
consisting of glasses having compositions consisting essentially
of, as calculated in percent by weight on an oxide basis: a. 54-58%
SiO.sub.2, 16-23% Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3, 2-4.5%
MgO, 1-7.1% CaO, 2.5-15.5% SrO and 0-14.5% BaO, MgO+CaO+SrO+BaO
being 15-27%, b. 55-67% SiO.sub.2, 6-14% Al.sub.2 O.sub.3, 0-7.5%
B.sub.2 O.sub.3, 0-7% MgO, 0-7.1% CaO, 0-15% SrO, 1-21% BaO,
MgO+CaO+SrO+BaO being 18-28%..]. .[.
7. A flat panel display in accordance with claim 1 in which the
glass panel has a density less than 2.5 grams/cc and a composition,
as calculated in weight percent on an oxide basis, consisting
essentially of 54.8-57% SiO.sub.2, 16.8-21.8% Al.sub.2 O.sub.3, 0
to less than 8% B.sub.2 O.sub.3, 2.2-2.5% MgO, 1.5-7.1% CaO,
4.5-5.5% SrO, 0.1-14.5% BaO, MgO+CaO+SrO+BaO being 12.5-27%..].
8. A method of producing a glass panel for a flat panel display
which comprises melting a batch for an aluminosilicate glass
consisting essentially of, as calculated in percent by weight on an
oxide basis, 49-67% SiO.sub.2, at least 6% Al.sub.2 O.sub.3, the
Al.sub.2 O.sub.3 being 6-14% in conjunction with 55-67% SiO.sub.2
and 16-23% in conjunction with 49-58% SiO.sub.2, SiO.sub.2
+Al.sub.2 O.sub.3 >68%, 0 to less than 8% B.sub.2 O.sub.3, at
least one alkaline earth metal oxide selected from the group
consisting of, in the indicated proportions, 0-21% BaO, 0-15% SrO,
0-7.1% CaO, 0-8% MgO and 12-30% BaO+CaO.[., .].
.Iadd.+.Iaddend.SrO+MgO, and drawing a thin sheet of molten glass
from the melt.
9. A method in accordance with claim 8 wherein the glass sheet is
drawn by a float process..[.
10. An aluminosilicate glass exhibiting a strain point higher than
640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE between 31 and 57.times.10.sup.-7 /.degree.C.,
nominally free of alkali metal oxides and having a composition
consisting essentially of, as calculated in percent by weight on an
oxide basis, 49-67% SiO.sub.2, at least 6% Al.sub.2 O.sub.3, the
Al.sub.2 O.sub.3 being 6-14% in conjunction with 55-67% SiO.sub.2
and 16-23% in conjunction with 49- 58% SiO.sub.2, SiO.sub.2
+Al.sub.2 O.sub.3 >68%, 0 to less than 8% B.sub.2 O.sub.3, at
least one alkaline earth metal oxide selected from the group
consisting of, in the proportions indicated, 0-21% BaO, 0-15% SrO,
0-7.1% CaO, 0-8% MgO and 12-30% BaO+CaO+SrO+MgO..]..[.
11. An aluminosilicate glass in accordance with claim 10 having a
CTE in the range of 31-44.times.10.sup.-7 /.degree.C. and being
selected from a group of aluminosilicate sub-families consisting of
glasses having compositions consisting essentially of, as
calculated in weight percent on an oxide basis; a. 49-58%
SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 0 to less than 8% B.sub.2
O.sub.3, 0-8% MgO, 0-7.1% CaO, 0.4-13.5% SrO, 0-21% BaO, the glass
containing at least one alkaline earth oxide in the indicated
proportion and the total BaO+CaO+SrO+MgO content being 13-28%, b.
57-66% SiO.sub.2, 8-14% Al.sub.2 O.sub.3, 0 to less than 8% B.sub.2
O.sub.3, 0-4.5% MgO, 0-7.1% CaO, 0.5-13% SrO, 2-21% BaO..]. .[.
12. An aluminosilicate glass in accordance with claim 11 in which
the glass has a CTE of 32-40.times.10.sup.-7 /.degree.C. and the
aluminosilicate sub-families consist essentially of: a. 54-57%
SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 5 to less than 8% B.sub.2
O.sub.3, 2-2.75% MgO, 1.5-<7% CaO, 2-6% SrO and 0.5-9.5% BaO, b.
57-65.5% SiO.sub.2, 8-13% Al.sub.2 O.sub.3, 4 to less than 8%
B.sub.2 O.sub.3, 2-3.5% MgO, 0-6.5% CaO, 0-13% SrO and 2-21%
BaO..]. .[.
13. An aluminosilicate glass in accordance with claim 10 having a
CTE in the range of 44-57.times.10.sup.-7 /.degree.C. and being
selected from a group of aluminosilicate sub-families consisting of
glasses having compositions consisting essentially of, as
calculated in weight percent on an oxide basis: a. 50-75%
SiO.sub.2, 16-22% Al.sub.2 O.sub.3, 0-5.5% B.sub.2 O.sub.3, 0.5-3%
MgO, 1-7.1% CaO, 0.5-15% SrO, 1-21% BaO, b. 55-67% SiO.sub.2, 6-14%
Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-6.5% MgO, 0-7.1% CaO,
0-15.5% SrO, 1-9.5% BaO, the total MgO+CaO+SrO+BaO being
16.5-28%..]. .[.
14. An aluminosilicate glass in accordance with claim 13 in which
the glass has a CTE in the range of 45-50.times.10.sup.-7
/.degree.C. and the aluminosilicate sub-families consist
essentially of: a. 50-57% SiO.sub.2, 16-20% Al.sub.2 O.sub.3,
0-5.5% B.sub.2 O.sub.3, 2-2.75% MgO, 1-<7% CaO, 0.5-15% SrO, and
1-21% BaO, b. 55-67% SiO.sub.2, 6-<13% Al.sub.2 O.sub.3, 0-7.5%
B.sub.2 O.sub.3, 2-6.5% MgO, 0-7.1% CaO, 0-14.5% SrO and 2-9.5%
BaO..]. .[.
15. An aluminosilicate glass in accordance with claim 10 having a
strain point greater than 660.degree. C. and a weight loss less
than 1 mg/cm.sup.2 after immersion for 24 hours in an aqueous 5% by
weight HCl solution at 95.degree. C. and being selected from a
group of aluminosilicate sub-families consisting of glasses having
compositions consisting essentially of, as calculated in percent by
weight on an oxide basis: a. 54-58% SiO.sub.2, 16-23% Al.sub.2
O.sub.3, 0-6% B.sub.2 O.sub.3, 2-4.5% MgO, 1-7.1% CaO, 2.5-15.5%
SrO and 0-14.5% BaO, MgO+CaO+SrO+BaO being 15-27%, b. 55-67%
SiO.sub.2, 6-14% Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-7%
MgO, 0-7.1% CaO, 0-15% SrO, 1-21% BaO, MgO+CaO+SrO+BaO being
18-28%..]. .[.
16. An aluminosilicate glass in accordance with claim 10 having a
density less than 2.5 grams/cc and a composition consisting
essentially of 54.8-57% SiO.sub.2, 16.8-21.8% Al.sub.2 O.sub.3, 0
to less than 8% B.sub.2 O.sub.3, 2.2-2.5% MgO, 1.5-7.1% CaO,
4.5-5.5% SrO, 0.1-14.5% BaO, MgO+CaO+SrO+BaO being
12.5-27%..]..[.
17. An aluminosilicate glass substrate exhibiting a strain point
higher than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2
after immersion for 24 hours in an aqueous 5% by weight HCl
solution at 95.degree. C., a CTE between 31 and 57.times.10.sup.-7
/.degree.C., nominally free of alkali metal oxides and having a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, 49-67% SiO.sub.2, at least 6% Al.sub.2
O.sub.3, the Al.sub.2 O.sub.3 being 6-14% in conjunction with
55-67% SiO.sub.2 and 16-23% in conjunction with 49- 58% SiO.sub.2,
SiO.sub.2 +Al.sub.2 O.sub.3 >68%, 0 to less than 8% B.sub.2
O.sub.3, at least one alkaline earth metal oxide selected from the
group consisting of, in the proportions indicated, 0-21% BaO, 0-15%
SrO, 0-7.1% CaO, 0-8% MgO and 12-30% BaO+CaO+SrO+MgO..]..[.
18. An aluminosilicate glass substrate in accordance with claim 17
having a CTE in the range of 31-44.times.10.sup.-7 /.degree.C. and
being selected from a group of aluminosilicate sub-families
consisting of glasses having compositions consisting essentially
of, as calculated in weight percent on an oxide basis; a. 49-58%
SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 0 to less than 8% B.sub.2
O.sub.3, 0-8% MgO, 0-7.1% CaO, 0.4-13.5% SrO, 0-21% BaO, the glass
containing at least one alkaline earth oxide in the indicated
proportion and the total BaO+CaO+SrO+MgO content being 13-28%, b.
57-66% SiO.sub.2, 8-14% Al.sub.2 O.sub.3, 0 to less than 8% B.sub.2
O.sub.3, 0-4.5% MgO, 0-7.1% CaO, 0.5-13% SrO, 2-21% BaO..]. .[.
19. An aluminosilicate glass substrate in accordance with claim 18
in which the glass has a CTE of 32-40.times.10.sup.-7 /.degree.C.
and the aluminosilicate sub-families consist essentially of: a.
54-57% SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 5 to less than 8%
B.sub.2 O.sub.3, 2-2.75% MgO, 1.5-<7% CaO, 2-6% SrO and 0.5-9.5%
BaO, b. 57-65.5% SiO.sub.2, 8-13% Al.sub.2 O.sub.3, 4 to less than
8% B.sub.2 O.sub.3, 2-3.5% MgO, 0-6.5% CaO, 0-13% SrO and 2-21%
BaO..]. .[.
20. An aluminosilicate glass substrate in accordance with claim 17
having a CTE in the range of 44-57.times.10.sup.-7 /.degree.C. and
being selected from a group of aluminosilicate sub-families
consisting of glasses having compositions consisting essentially
of, as calculated in weight percent on an oxide basis: a. 50-57%
SiO.sub.2, 16-22% Al.sub.2 O.sub.3, 0-5.5% B.sub.2 O.sub.3, 0.5-3%
MgO, 1-7.1% CaO, 0.5-15% SrO, 1-21% BaO, b. 55-67% SiO.sub.2, 6-14%
Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-6.5% MgO, 0-7.1% CaO,
0-15.5% SrO, 1-9.5% BaO, the total MgO+CaO+SrO+BaO being
16.5-28%..]. .[.
21. An aluminosilicate glass substrate in accordance with claim 20
in which the glass has a CTE in the range of 45-50.times.10.sup.-7
/.degree.C. and the aluminosilicate sub-families consist
essentially of: a. 50-57% SiO.sub.2, 16-20% Al.sub.2 O.sub.3,
0-5.5% B.sub.2 O.sub.3, 2-2.75% MgO, 1-<7% CaO, 0.5-15% SrO and
1-21% BaO, b. 55-67% SiO.sub.2, 6-<13% Al.sub.2 O.sub.3, 0-7.5%
B.sub.2 O.sub.3, 2-6.5% MgO, 0-7.1% CaO, 0-14.5% SrO and 2-9.5%
BaO..]. .[.
22. An aluminosilicate glass substrate in accordance with claim 17
having a strain point greater than 660.degree. C. and a weight loss
less than 1 mg/cm.sup.2 after immersion for 24 hours in an aqueous
5% by weight HCl solution at 95.degree. C. and being selected from
a group of aluminosilicate sub-families consisting of glasses
having compositions consisting essentially of, as calculated in
percent by weight on an oxide basis: a. 54-58% SiO.sub.2, 16-23%
Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3, 2-4.5% MgO, 1-7.1% CaO,
2.5-15.5% SrO and 0-14.5% BaO, MgO+CaO+SrO+BaO being 15-27%, b.
55-67% SiO.sub.2, 6-14% Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3,
0-7% MgO, 0-7.1% CaO, 0-15% SrO, 1-21% BaO, MgO+CaO+SrO+BaO being
18-28%..]. .[.
23. An aluminosilicate glass substrate in accordance with claim 17
having a density less than 2.5 grams/cc and a composition
consisting essentially of 54.8-57% SiO.sub.2, 16.8-21.8% Al.sub.2
O.sub.3, 0 to less than 8% B.sub.2 O.sub.3, 2.2-2.5% MgO, 1.5-7.1%
CaO, 4.5-5.5% SrO, 0.1-14.5% BaO, MgO+CaO+SrO+BaO being
12.5-27%..]..Iadd.
24. A method of producing a glass panel for a flat panel display,
by a float glass process, which comprises melting a batch for an
aluminosilicate glass consisting essentially of, as calculated in
percent by weight on an oxide basis, 60 up to 67% SiO.sub.2, at
least 6% Al.sub.2 O.sub.3, SiO.sub.2 +Al.sub.2 O.sub.3 >68%,
B.sub.2 O.sub.3 which is present in an amount of up to 8%, at least
one alkaline earth metal oxide selected from the group consisting
of, in the proportions indicated, 0-21% BaO, 0-15% SrO, 0-7.1% CaO,
0-8% MgO and 12-30% BaO+CaO+SrO+MgO and drawing a thin sheet of
molten glass from the melt..Iaddend..Iadd.
25. A method according to claim 24, wherein the aluminosilicate
glass composition consists essentially of above 60 up to 67%
SiO.sub.2..Iaddend..Iadd.
26. A method of producing a glass panel for a flat panel display
which comprises melting a batch for an aluminosilicate glass
consisting essentially of, as calculated in weight percent on an
oxide basis, above 60% up to 67% SiO.sub.2, at least 6% Al.sub.2
O.sub.3, SiO.sub.2 +Al.sub.2 O.sub.3 >68%, B.sub.2 O.sub.3 which
is present in an amount of up to 15%, at least one alkaline earth
metal oxide selected from the group consisting of, in the
proportions indicated, 0-21% BaO, 0-15% SrO, 0-7.1% CaO, 0-8% MgO
and 12-30% BaO+CaO+SrO+MgO, and drawing a thin sheet of molten
glass from the melt by a float process..Iaddend..Iadd.
27. A method of producing a glass panel for a flat panel display
which comprises melting a batch for aluminosilicate glass which is
nominally free of alkali metal oxides and has a composition that
consists essentially of, as calculated in percent by weight on an
oxide basis, 49-58% SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 0-14.5%
B.sub.2 O.sub.3, 0-8% MgO, 0-9% CaO, 0.4-13.5% SrO, 0-21% BaO, and
13-28% MgO+CaO+SrO+BaO, and drawing a thin sheet of molten glass
from the melt by a float process wherein the glass panel has a
strain point higher than 640.degree. C., a CTE in the range of
31-44.times.10.sup.-7 /.degree. C., and a weight loss less than 2.5
mg/cm.sup.2 after immersion for 24 hours in an aqueous 5% by weight
HCl solution at 95.degree. C..Iaddend..Iadd.
28. The method according to claim 27, wherein the CTE is in the
range of 32-40.times.10.sup.-7 /.degree. C..Iaddend..Iadd.
29. The method according to claim 27, wherein the glass panel has a
CTE in the range of 32-40.times.10.sup.-7 /.degree. C. and the
glass has a composition consisting essentially of, as calculated in
percent by weight on an oxide basis, 54-57% SiO.sub.2, 17.5-23%
Al.sub.2 O.sub.3, 5 to less than 8% B.sub.2 O.sub.3, 2-2.75% MgO,
1.5-<7% CaO, 2-6% SrO, and 0.5-9.5% BaO..Iaddend..Iadd.
30. A glass panel produced by the method of claim
27..Iaddend..Iadd.
31. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 2.5 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 31-44.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides, and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, 57-66%
SiO.sub.2, 8-14% Al.sub.2 O.sub.3, 0 to less than 8% B.sub.2
O.sub.3, 0-4.5% MgO, 0-7.1% CaO, 0.5-13% SrO, and 2-21%
BaO..Iaddend..Iadd.
32. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 2.5 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 32-40.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides, and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, either:
a. 54-57% SiO.sub.2, 17.5-23% Al.sub.2 O.sub.3, 5 to less than 8%
B.sub.2 O.sub.3, 2-2.75% MgO, 1.5-<7.1% CaO, 2-6% SrO, and
0.5-9.5% BaO or b. 57-65.5% SiO.sub.2, 8-13% Al.sub.2 O.sub.3, 4 to
less than 8% B.sub.2 O.sub.3, 2-3.5% MgO, 0-6.5% CaO, 0-13% SrO,
and 2-21% BaO..Iaddend..Iadd.
33. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 2.5 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 44-57.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, either:
a. 50-57% SiO.sub.2, 16-22% Al.sub.2 O.sub.3, 0-5.5% B.sub.2
O.sub.3, 0.5-3% MgO, 1-7.1% CaO, 0.5-15% SrO, and 1-21% BaO or b.
55-67% SiO.sub.2, 6-14% Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3,
0-6.5% MgO, 0-7.1% CaO, 0-15.5% SrO, 1-9.5% BaO, and
MgO+CaO+SrO+BaO being 16.5-28%..Iaddend..Iadd.
34. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 2.5 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 45-50.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, either:
a. 50-57% SiO.sub.2, 16-20% Al.sub.2 O.sub.3, 0-5.5% B.sub.2
O.sub.3, 2-2.75% MgO, 1-<7% CaO, 0.5-15% SrO, and 1-21% BaO or
b. 55-67% SiO.sub.2, 6-<13% Al.sub.2 O.sub.3, 0-7.5% B.sub.2
O.sub.3, 2-6.5% MgO, 0-7.1% CaO, 0-14.5% SrO, and 2-9.5%
BaO..Iaddend..Iadd.
35. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 660.degree. C., a weight
loss less than 1 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 31-57.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides and has a composition consisting essentially
of, as calculated in percent by weight on an oxide basis, either:
a. 54-58% SiO.sub.2, 16-23% Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3,
2-4.5% MgO, 1-7.1% CaO, 2.5-15.5% SrO, and 0-14.5% BaO,
MgO+CaO+SrO+BaO being 15-27% or b. 55-67% SiO.sub.2, 6-14% Al.sub.2
O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-7% MgO, 0-7.1% CaO, 0-15% SrO,
1-21% BaO, and MgO+CaO+SrO+BaO being 18-28%..Iaddend..Iadd.
36. A flat panel display comprising an aluminosilicate glass panel
that exhibits a strain point higher than 640.degree. C., a weight
loss less than 2.5 mg/cm.sup.2 after immersion for 24 hours in an
aqueous 5% by weight HCl solution at 95.degree. C., a CTE in the
range of 31-57.times.10.sup.-7 /.degree. C., is nominally free of
alkali metal oxides, has a density less than 2.5 grams/cc, and a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, 54.8-57% SiO.sub.2, 16.8-21.8% Al.sub.2
O.sub.3, 0 to less than 8% B.sub.2 O.sub.3, 2.2-2.5% MgO, 1.5-7.1%
CaO, 4.5-5.5% SrO, 0.1-14.5% BaO, and MgO+CaO+SrO+BaO being
12.5-27%..Iaddend..Iadd.
37. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 31-44.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, 57-66% SiO.sub.2, 8-14% Al.sub.2 O.sub.3,
0 to less than 8% B.sub.2 O.sub.3, 0-4.5% MgO, 0-7.1% CaO, 0.5-13%
SrO, and 2-21% BaO..Iaddend..Iadd.
38. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 32-40.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 54-57% SiO.sub.2, 17.5-23%
Al.sub.2 O.sub.3, 5 to less than 8% B.sub.2 O.sub.3, 2-2.75% MgO,
1.5-<7% CaO, 2-6% SrO, and 0.5-9.5% BaO or b. 57-65.5%
SiO.sub.2, 8-13% Al.sub.2 O.sub.3, 4 to less than 8% B.sub.2
O.sub.3, 2-3.5% MgO, 0-6.5% CaO, 0-13% SrO, and 2-21%
BaO..Iaddend..Iadd.
39. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 44-57.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 50-57% SiO.sub.2, 16-22%
Al.sub.2 O.sub.3, 0-5.5% B.sub.2 O.sub.3, 0.5-3% MgO, 1-7.1% CaO,
0.5-15% SrO, and 1-21% BaO or b. 55-67% SiO.sub.2, 6-14% Al.sub.2
O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-6.5% MgO, 0-7.1% CaO, 0-15.5%
SrO, 1-9.5% BaO, and the total MgO+CaO+SrO+BaO being
16.5-28%..Iaddend..Iadd.
40. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 45-50.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 50-57% SiO.sub.2, 16-20%
Al.sub.2 O.sub.3, 0-5.5% B.sub.2 O.sub.3, 2-2.75% MgO, 1-<7%
CaO, 0.5-15% SrO, and 1-21% BaO or b. 55-67% SiO.sub.2, 6-<13%
Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3, 2-6.5% MgO, 0-7.1% CaO,
0-14.5% SrO, and 2-9.5% BaO..Iaddend..Iadd.
41. An aluminosilicate glass that exhibits a strain point higher
than 660.degree. C., a weight loss less than 1 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 31-57.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 54-58% SiO.sub.2, 16-23%
Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3, 2-4.5% MgO, 1-7.1% CaO,
2.5-15.5% SrO, 0-14.5% BaO, and MgO+CaO+SrO+BaO being 15-27% or b.
55-67% SiO.sub.2, 6-14% Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3,
0-7% MgO, 0-7.1% CaO, 0-15% SrO, 1-21% BaO, and MgO+CaO+SrO+BaO
being 18-28%..Iaddend..Iadd.
42. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 31-57.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, has a
density less than 2.5 grams/cc, and a composition consisting
essentially of, as calculated in percent by weight on an oxide
basis, 54.8-57% SiO.sub.2, 16.8-21.8% Al.sub.2 O.sub.3, 0 to less
than 8% B.sub.2 O.sub.3, 2.2-2.5% MgO, 1.5-7.1% CaO, 4.5-5.5% SrO,
0.1-14.5% BaO, and MgO+CaO+SrO+BaO being
12.5-27%..Iaddend..Iadd.
43. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 31-44.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, 57-66% SiO.sub.2, 8-14% Al.sub.2 O.sub.3,
0 to less than 8% B.sub.2 O.sub.3, 0-4.5% MgO, 0-7.1% CaO, 0.5-13%
SrO, and 2-21% BaO..Iaddend..Iadd.
44. A aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 32-40.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 54-57% SiO.sub.2, 17.5-23%
Al.sub.2 O.sub.3, 5 to less than 8% B.sub.2 O.sub.3, 2-2.75% MgO,
1.5-<7% CaO, 2-6% SrO, and 0.5-9.5% BaO or b. 57-65.5%
SiO.sub.2, 8-13% Al.sub.2 O.sub.3, 4 to less than 8% B.sub.2
O.sub.3, 2-3.5% MgO, 0-6.5% CaO, 0-13% SrO, and 2-21%
BaO..Iaddend..Iadd.
45. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 44-57.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 50-57% SiO.sub.2, 16-22%
Al.sub.2 O.sub.3, 0-5.5% B.sub.2 O.sub.3, 0.5-3% MgO, 1-7.1% CaO,
0.5-15% SrO, and 1-21% BaO or b. 55-67% SiO.sub.2, 6-14% Al.sub.2
O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-6.5% MgO, 0-7.1% CaO, 0-15.5%
SrO, 1-9.5% BaO, and the total MgO+CaO+SrO+BaO being
16.5-28%..Iaddend..Iadd.
46. An aluminosilicate glass that exhibits a strain point higher
than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2 after
immersion for 24 hours in an aqueous 5% by weight HCl solution at
95.degree. C., a CTE in the range of 45-50.times.10.sup.-7
/.degree. C., is nominally free of alkali metal oxides, and has a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, either: a. 50-57% SiO.sub.2, 16-20%
Al.sub.2 O.sub.3, 0-5.5% B.sub.2 O.sub.3, 2-2.75% MgO, 1-<7%
CaO, 0.5-15% SrO, and 1-21% BaO or b. 55-67% SiO.sub.2, 6-<13%
Al.sub.2 O.sub.3, 0-7.5% B.sub.2 O.sub.3, 2-6.5% MgO, 0-7.1% CaO,
0-14.5% SrO, and 2-9.5% BaO..Iaddend..Iadd.
47. An aluminosilicate glass panel that exhibits a strain point
higher than 660.degree. C., a weight loss less than 1 mg/cm.sup.2
after immersion for 24 hours in an aqueous 5% by weight HCl
solution at 95.degree. C., a CTE in the range of
31-57.times.10.sup.-7 /.degree. C., is nominally free of alkali
metal oxides and has a composition consisting essentially of, as
calculated in percent by weight on an oxide basis, either: a.
54-58% SiO.sub.2, 16-23% Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3,
2-4.5% MgO, 1-7.1% CaO, 2.5-15.5% SrO, 0-14.5% BaO, and
MgO+CaO+SrO+BaO being 15-27% or b. 55-67% SiO.sub.2, 6-14% Al.sub.2
O.sub.3, 0-7.5% B.sub.2 O.sub.3, 0-7% MgO, 0-7.1% CaO, 0-15% SrO,
1-21% BaO, and MgO+CaO+SrO+BaO being 18-28%..Iaddend..Iadd.
48. An aluminosilicate glass panel that exhibits a strain point
higher than 640.degree. C., a weight loss less than 2.5 mg/cm.sup.2
after immersion for 24 hours in an aqueous 5% by weight HCl
solution at 95.degree. C., a CTE in the range of
31-57.times.10.sup.-7 /.degree. C., is nominally free of alkali
metal oxides, has a density less than 2.5 grams/cc, and a
composition consisting essentially of, as calculated in percent by
weight on an oxide basis, 54.8-57% SiO.sub.2, 16.8-21.8% Al.sub.2
O.sub.3, 0 to less than 8% B.sub.2 O.sub.3, 2.2-2.5% MgO, 1.5-7.1%
CaO, 4.5-5.5% SrO, 0.1-14.5% BaO, and MgO+CaO+SrO+BaO being
12.5-27%..Iaddend.
Description
FIELD OF THE INVENTION
A flat panel display device having an aluminosilicate glass panel
exhibiting physical and chemical properties necessary for such
devices and their production.
BACKGROUND OF THE INVENTION
Flat panel displays have received a great deal of attention
recently. Thus far, much of the attention has centered on small
units such as are used in laptop computers. However, increasing
consideration is being given to larger units for information and
entertainment applications. One particular form of flat panel
display is known as a liquid crystal display.
Liquid crystal displays (LCDs) are flat panel display devices which
depend upon external sources of light for illumination. They may
take one of two basic matrix types, intrinsic or extrinsic matrix
addressed. The intrinsic matrix type relies upon the threshold
properties of the liquid crystal material. The extrinsic, or active
matrix (AM), type has an array of diodes, metal-insulator-metal
(MIM) devices, or thin film transistors (TFTs), that supplies an
electronic switch to each pixel.
In both cases, two sheets of glass form the structure of the
display. The separation between the two sheets is the critical gap
dimension, of the order of 5-10 .mu.m. The glass sheets must be
transparent, and must withstand the chemical conditions to which
they are exposed during display processing. Otherwise, the needs of
the two matrix types differ.
Intrinsically addressed LCDs are fabricated using thin film
deposition techniques at temperatures .ltoreq.350.degree. C.,
followed by photolithographic patterning. As a result, the
substrate requirements therefore are often the same as those for
segmented displays. Soda-lime-silica glass with a barrier layer has
proven to be adequate for most needs.
A high performance version of intrinsically addressed LCDs, the
super twisted nematic (STN) type, has an added requirement of
extremely precise flatness for the purpose of holding the gap
dimensions uniform. Because of that requirement, soda-lime-silica
glass used for those displays must be polished. Alternatively, a
precision formed, barium aluminoborosilicate glass, marketed by
Corning Incorporated, Corning, N.Y. as Code 7059, may be used
without polishing.
Extrinsically addressed LCDs can be further subdivided into two
categories; viz., one based on MIM or amorphous silicon (a-Si)
devices, and the other based on polycrystalline silicon (poly-Si)
devices. The substrate requirements of the MIM or a-Si type are
similar to the STN application. Corning Code 7059 sheet glass is
the preferred substrate because of its very low sodium content,
i.e., less than 0.1% Na.sub.2 O by weight, its dimensional
precision, and its commercial availability.
Devices formed from poly-Si, however, are processed at higher
temperatures than those that are employed with a-Si TFTs.
Substrates capable of use temperatures (taken to be 25.degree. C.
below the strain point of the glass) of 600.degree.-800.degree. C.
are demanded. The actual temperature required is mandated by the
particular process utilized in fabricating the TFTs. Those TFTs
with deposited gate dielectrics require 600.degree.-650.degree. C.,
while those with thermal oxides call for about 800.degree. C.
Both a-Si and poly-Si processes demand precise alignment of
successive photolithographic patterns, thereby necessitating that
the thermal shrinkage of the substrate be kept low. The higher
temperatures required for poly-Si mandate the use of glasses
exhibiting higher strain points than soda-lime-silica glass and
Corning Code 7059 glass in order to avoid thermal deformation of
the sheet during processing. As can be appreciated, the lower the
strain point, the greater this dimensional change. Thus, there has
been considerable research to develop glasses demonstrating high
strain points so that thermal deformation is minimized during
device processing at temperatures greater than 600.degree. C., and
preferably, higher than 650.degree. C.
U.S. Pat. No. 4,824,808 (Dumbaugh, Jr.) lists four properties which
have been deemed mandatory for a glass to exhibit in order to fully
satisfy the needs of a substrate for LCDs:
First, the glass must be essentially free of intentionally added
alkali metal oxide to avoid the possibility that alkali metal from
the substrate can migrate into the transistor matrix;
Second, the glass substrate must be sufficiently chemically durable
to withstand the reagents used in the TFT matrix deposition
process;
Third, the expansion mismatch between the glass and the silicon
present in the TFT array must be maintained at a relatively low
level even as processing temperatures for the substrates increase;
and
Fourth, the glass must be capable of being produced in high quality
thin sheet form at low cost; that is, it must not require extensive
grinding and polishing to secure the necessary surface finish.
That last requirement is most difficult to achieve inasmuch as it
demands a sheet glass production process capable of producing
essentially finished glass sheet. Currently, the overflow downdraw
sheet manufacturing process is employed. This process is described
in U.S. Pat. No. 3,338,696 (Dockerty) and U.S. Pat. No. 3,682,609
(Dockerty). That process requires a glass exhibiting a very high
viscosity at the liquidus temperature plus long term stability,
e.g., periods of 30 days, against devitrification at melting and
forming temperatures.
Corning Code 7059 glass, supra, is currently employed in the
fabrication of LCDs. That glass, consisting essentially, in weight
percent, of about 50% SiO.sub.2, 15% B.sub.2 O.sub.3, 10% Al.sub.2
O.sub.3, and 24% BaO, is nominally free of alkali metal oxides, and
exhibits a linear coefficient of thermal expansion, CTE,
(25.degree.-300.degree. C.) of about 46.times.10.sup.-7 /.degree.C.
and a viscosity at the liquidus temperature in excess of 60,000
Pa.s (600,000 poises). The high liquidus viscosity of the glass
enables it to be drawn into sheet via the overflow downdraw sheet
processing technique, but its relatively low strain point
(.about.593.degree. C.) is adequate only for processing a-Si
devices and not for poly-Si devices.
Accordingly, extensive research has been directed at developing
glasses designed to meet at least three general requirements.
Initially, the glasses had to be adapted to use in fabricating
poly-Si devices. Next, they had to be capable of being formed into
sheet by the overflow downdraw process. Finally, they had to have
linear CTEs that closely matched silicon.
The fruits of such research are reported, for example, in U.S. Pat.
Nos. 4,409,337; 4,824,808; 5,116,787; 5,116,788; and 5,116,789, all
issued in the name of W. H. Dumbaugh, Jr. The properties of these
glasses, as well as their shortcomings, are reviewed in pending
application Ser. No. 08/008,560 filed in the names of Dumbaugh, Jr.
et al. and assigned to the assignee of the subject application.
A recent advance in liquid crystal technology termed
"chip-on-glass" (COG) has further emphasized the need for the
substrate glass to closely match silicon in thermal expansion.
Thus, the initial LCD devices did not have their driver chips
mounted on the substrate glass. Instead, the silicon chips were
mounted remotely and were connected to the LCD substrate circuitry
with compliant or flexible wiring. As LCD device technology
improved and as the devices became larger, these flexible mountings
became unacceptable, both because of cost and of uncertain
reliability. This situation led to Tape Automatic Bonding (TAB) of
the silicon chips. In that process the silicon chips and electrical
connections to the chips were mounted on a carrier tape, that
subassembly was mounted directly on the LCD substrate, and
thereafter the connection to the LCD circuitry was completed. TAB
decreased cost while improving reliability and increasing the
permitted density of the conductors to a pitch of approximately 200
.mu.m--all significant factors. COG, however, provides further
improvement over TAB with respect to those three factors. Hence, as
the size and quality requirements of LCD devices increase, COG is
demanded for those devices dependent upon the use of integrated
circuit silicon chips. For that reason, the substrate glass must
demonstrate a linear coefficient of thermal expansion closely
matching that of silicon; i.e., the glass must exhibit a linear
coefficient of thermal expansion (0.degree.-300.degree. C.) between
31-44.times.10.sup.-7 /.degree.C., most preferably
32-40.times.10.sup.-7 /.degree.C.
The high viscosity value at the liquidus required for the overflow
downdraw process, 600,000 poises (60,000 Pa.s), has been difficult
to obtain in conjunction with the several other properties required
for poly-Si devices. Consequently, attention has been given to
other sheet-forming processes where the viscosity factor is not of
such great significance. These include the float process and a
redraw process.
The float process involves drawing a continuous sheet of glass over
the surface of a molten metal, such as molten tin. The surface
contacting the molten metal is not exposed during drawing, and
hence is relatively smooth and free from defects. This has the
virtue of requiring finishing of only one surface. It is a primary
purpose of the present invention to provide panels for flat panel
display devices, in particular, LCD devices embodying poly-Si
chips. A further purpose is to provide such panels that can be
fabricated by a method other than the overflow downdraw process,
such as the float process.
SUMMARY OF THE INVENTION
The present invention resides in a flat panel display comprising an
aluminosilicate glass panel that exhibits a strain point higher
than 640.degree. C., CTEs in the range of 31-57.times.10.sup.-7
/.degree.C., a weight loss less than 20 mg/cm.sup.2 after immersion
for 24 hours in an aqueous 5% by weight HCl solution at 95.degree.
C., that is nominally free from alkali metal oxides and has a
composition consisting essentially, calculated in weight percent on
the oxide basis, of 49-67% SiO.sub.2, at least 6% Al.sub.2 O.sub.3,
the Al.sub.2 O.sub.3 being 6- 14% in conjunction with 55-67%
SiO.sub.3 and 16-23% in conjunction with 49-58% SiO.sub.2,
SiO.sub.2 +Al.sub.2 O.sub.3 >68%, 0-15% B.sub.2 O.sub.3, at
least one alkaline earth metal oxide selected from the group
consisting of, in the preparations indicated, 0-21% BaO, 0-15% SrO,
0- 18% CaO, 0-8% MgO and 12-30% BaO+CaO+SrO+MgO.
The invention further resides in a method of producing a glass
panel for a flat panel display which comprises melting a batch for
an aluminosilicate glass consisting essentially of, as calculated
in percent by weight on an oxide basis, 49-67% SiO.sub.2, at least
6% Al.sub.2 O.sub.3, the Al.sub.2 O.sub.3 being 6-14% in
conjunction with 55-67% SiO.sub.2 and 16-23% in conjunction with
49-58% SiO.sub.2, SiO.sub.2 +Al.sub.2 O.sub.3 >68%, 0-15%
B.sub.2 O.sub.3, at least one alkaline earth metal oxide selected
from the group consisting of, in the indicated proportions, 0-21%
BaO, 0-15% SrO, 0-18% CaO, 0-8% MgO and 12-30% BaO+CaO, SrO+MgO,
and drawing a thin sheet of molten glass from the melt.
The invention also contemplates an aluminosilicate glass exhibiting
a strain point higher than 640.degree. C., a weight loss less than
20 mg/cm.sup.2 after immersion for 24 hours in an aqueous 5% by
weight HCl solution at 95.degree. C., a CTE between 31 and
57.times.10.sup.-7 /.degree.C., nominally free of alkali metal
oxides and having a composition consisting essentially of, as
calculated in percent by weight on an oxide basis, 49-67%
SiO.sub.2, at least 6% Al.sub.2 O.sub.3, the Al.sub.2 O.sub.3 being
6-14% in conjunction with 55-67% SiO.sub.2 and 16-23% in
conjunction with 49-58% SiO.sub.2, SiO.sub.2 +Al.sub.2 O.sub.3
>68%, 0-15% B.sub.2 O.sub.3, at least one alkaline earth metal
oxide selected from the group consisting of, in the proportions
indicated, 0-21% BaO, 0-15% SrO, 0-18% CaO, 0-8% MgO and 12-30%
BaO+CaO+SrO+MgO.
DESCRIPTION OF THE INVENTION
The invention arose from a desire for flat display device panels
that could be produced by a method that did not impose the
requirement of the overflow downdraw process. In particular, it was
desired to avoid the need for the very high viscosity at the
liquidus temperature of over 60,000 Pa.s (600,000 poises).
At the same time, certain other requirements must be met, however.
These include a glass strain point greater than 640.degree. C.,
good chemical durability, freedom from alkali metals and a
controlled coefficient of thermal expansion (CTE).
We have found that these several requirements may be met by members
of a nominally alkali metal-free, aluminosilicate glass family
having compositions, calculated on an oxide basis, consisting
essentially of 49-67% SiO.sub.2, at least 6% Al.sub.2 O.sub.3, the
Al.sub.2 O.sub.3 being 6-14% Al.sub.2 O.sub.3 in conjunction with
55-67% SiO.sub.2, and 16-23% in conjunction with 49-58% SiO.sub.2,
SiO.sub.2 +Al.sub.2 O.sub.3 >68%, 0-15% B.sub.2 O, at least one
alkaline earth metal oxide selected from the group consisting of,
in the proportions indicated, of 0-21% BaO, 0-15% SrO, 0-18% CaO,
0-8% MgO and 12-30% BaO+SrO+CaO+MgO.
Compliance with those specified composition intervals has been
found necessary in order to obtain glasses illustrating the desired
matrix of chemical, forming, and physical properties, as is
demonstrated below.
SiO.sub.2 and Al.sub.2 O.sub.3 are the glass-forming oxides. At
least 49% SiO.sub.2 and 6% Al.sub.2 O.sub.3 are required for this
purpose, as well as to provide the desired high strain point. Glass
melting tends to become difficult with SiO.sub.2 contents greater
than 67% and Al.sub.2 O.sub.3 contents greater than 23%.
SiO.sub.2 and Al.sub.2 O.sub.3 are also of concern with respect to
glass durability. In this respect, however, the SiO.sub.2 and
Al.sub.2 O.sub.3 contents are interdependent. Thus, with Al.sub.2
O.sub.3 contents in the range of 6-14%, a SiO.sub.2 content of at
least 55%, and preferably at least 60%, is necessary to provide the
required chemical durability. With an Al.sub.2 O.sub.3 content in
the range of 16-23%, the SiO.sub.2 content may be as low as 49%
while obtaining adequate durability. The total SiO.sub.2 +Al.sub.2
O.sub.3 content should be greater than about 68% to achieve the
desired durability.
B.sub.2 O.sub.3 tends to soften the glass, that is, lower the
melting temperature and facilitate melting. However, it lowers the
strain point and is detrimental to durability, particularly in
large amounts. Consequently, the B.sub.2 O.sub.3 content should not
exceed about 15%, and preferably is no more than 8%.
Where silicon chips are to be mounted on the glass, and a CTE of
31-44.times.10.sup.-7 /.degree.C. is necessary, BaO content is
preferably maintained low. Other alkaline earth metal oxides and/or
Al.sub.2 O.sub.3 may be substituted.
In general, the alkaline earth metals increase CTE in this order
Ba>Sr>Ca>Mg with BaO having the greatest effect and MgO
the least.
In addition to the constituents recited above, a variety of
optional constituents are also contemplated. These include
TiO.sub.2, ZrO.sub.2, ZnO, La.sub.2 O.sub.3, Ta.sub.2 O.sub.5,
Nb.sub.2 O.sub.5 and Y.sub.2 O.sub.3. Preferably, these oxides are
not present in amounts exceeding about 5% by weight since they tend
to increase density and may decrease the strain point. In general,
any benefits, such as to refractive index or durability, may be
obtained otherwise.
Alkali metals and halides tend to poison liquid crystal fluids, and
hence are avoided except as unavoidable impurities.
A commonly accepted measure of chemical durability is weight loss
when a glass sample is immersed in a 5% by weight solution of HCl
for 24 hours at 95.degree. C. For present purposes, the weight loss
must be less than 20 mg/cm.sup.2, is preferably below 5, and most
preferably below one mg/cm.sup.2.
There are two levels of coefficient of thermal expansion (CTE) that
are relevant in glass panels for display panels, particularly LCD
devices. One level is based on what had become a standard in the
trade, Code 7059 glass. That glass has a CTE of 46.times.10.sup.-7
/.degree.C., and a CTE range of 44-57.times.10.sup.-7 /.degree.C.
has been considered compatible. Preferably, the range is
45-50.times.10.sup.-7 /.degree.C.
We have found two aluminosilicate sub-families A and B that provide
CTE values at this level. Glasses having compositions that fall
within these sub-families consist essentially of, as calculated in
weight percent on an oxide basis:
A B SiO.sub.2 50-57 55-67 Al.sub.2 O.sub.3 16-22 6-14 B.sub.2
O.sub.3 0-5.5 0-7.5 MgO 0.5-3 0-6.5 CaO 1-12.5 0-18.5 SrO 0.5-15
0-15.5 BaO 1-21 1-9.5 MgO + CaO + SrO + BaO -- 16.5-28
The other CTE level is based on a desire to match silicon, thus
permitting direct chip attachment. Silicon has a CTE of
36.times.10.sup.-7 /.degree.C. Accordingly, a CTE range for glass
panels may be 31-44.times.10.sup.-7 /.degree.C., preferably
32-40.times.10.sup.-7 /.degree.C.
To achieve CTE values within these ranges, we have found two
aluminosilicate sub-families C and D that meet the requirement.
Glasses having compositions that fall within these sub-families
consist essentially of, as calculated in weight percent on an oxide
basis:
C D SiO.sub.2 49-58 57-66 Al.sub.2 O.sub.3 17.5-23 8-14 B.sub.2
O.sub.3 0-14.5 0-13 MgO 0-8 0-4.5 CaO 0-9 0-9 SrO 0.4-13.5 0.5-13
BaO 0-21 2-21 MgO + CaO + SrO + BaO 13-28
In another aspect, the invention contemplates a method of producing
panels for LCD devices by melting a glass as described above,
forming sheet glass from the melt by such processes as the float
process, redrawing or rolling, and cutting the sheet into panel
size.
DESCRIPTION OF PREFERRED EMBODIMENTS
Table I reports a number of glass compositions. The compositions
are expressed in terms of parts by weight on the oxide basis,
illustrating the compositional parameters of the present inventive
glasses. The sum of the individual components closely approximates
100, being slightly lower due to omission of a fining agent, such
as As.sub.2 O.sub.3. Hence, for all practical purposes, the listed
values may be considered to reflect weight percent.
The actual batch materials may comprise the desired oxides. They
may also comprise other compounds, which, when melted together with
the other batch constituents, will be converted into the desired
oxides in the proper proportions. For example, CaCO.sub.3 and
BaCO.sub.3 can supply the source of CaO and BaO, respectively.
Glass batches based on these compositions were compounded. The
batches were tumble mixed together thoroughly to assist in
obtaining a homogeneous melt, and then charged into platinum
crucibles. After placing lids thereon, the crucibles were
introduced into furnaces operating at temperatures of 1650.degree.
C. To assure the formation of glasses free form inclusions and
cords, a two-step melting practice was undertaken. The batch was
first melted for about 16 hours and stirred. It was thereafter
poured as a fine stream into a bath of tap water to form
finely-divided particles of glass. This process is termed
"drigaging" in the glass art. In the second step, the
finely-divided glass particles (after drying) were remelted at
1650.degree. C. for about four hours. The melts were stirred in
both directions, i.e., both clockwise and counterclockwise. The
melts were then poured onto steel plates to make glass slabs having
the approximate dimensions 18".times.6".times.0.5"
(.about.45.7.times.15.2.times.1.3 cm). Those slabs were then
transferred immediately to an annealer operating at about
725.degree. C.
It must be recognized that the above description reflects a
laboratory melting procedure only. Thus, the inventive glasses are
quite capable of being melted and formed utilizing large scale,
commercial glass melting and forming equipment. Where desired,
fining agents, such as the oxides of arsenic and antimony, may be
added in customary amounts. The small residual remaining in the
glass has no substantial effect upon the physical properties of the
glass.
Table I also recites measurements of several chemical and physical
properties determined on the glasses in accordance with measuring
techniques conventional in the glass art. The linear coefficient of
thermal expansion (CTE) over the temperature range
0.degree.-300.degree. C. is expressed in terms of .times.10.sup.-7
/.degree.C. The softening point (S.P.), and the strain point (St.P)
are expressed in terms of .degree.C., and were determined via fiber
elongation. The durability (Dur) in HCl was evaluated by
determining the weight loss (mg/cm.sup.2) after immersion in a bath
of aqueous 5% by weight HCl operating at 95.degree. C. for 24
hours.
TABLE I 1 2 3 4 5 6 SiO.sub.2 65 65.4 50.6 65 55.7 64.7 Al.sub.2
O.sub.3 8.2 13 22.1 8.1 13.6 8.0 B.sub.2 O.sub.3 7.8 -- 6.0 5.8 5.1
-- MgO 3.1 -- -- 0.3 3.0 -- CaO -- -- -- 18 7.1 5.7 SrO 13 0.4 12.8
-- 5.2 12.9 BaO 2.2 20.7 8.2 2.2 9.3 7.7 CTE 38.6 38.9 41.3 48.5
46.8 49.4 St.P. 692 810 719 669 662 710 S.P. 1016 985 1003 1093 913
980 Dur. 2.73 0.03 6.65 0.69 0.22 0.01 7 8 9 10 11 12 SiO.sub.2
50.3 49.9 65.3 61.2 50.3 50.3 Al.sub.2 O.sub.3 20.1 21.8 8.0 13.3
21.5 21.7 B.sub.2 O.sub.3 0.6 -- -- 5.5 -- -- MgO 0.6 5.9 5.9 2.9
5.8 3.1 CaO 6.4 0.3 -- 8.7 0.6 9.2 SrO 0.4 0.5 12.6 5.9 0.4 13 BaO
20.9 20.5 7.0 2.4 20.2 2.2 CTE 48.7 43.5 44.9 43.4 43.6 51.3 St.P.
734 750 714 674 744 728 S.P. 1008 1013 993 928 1012 972 Dur. 4.9
5.4 0.01 0.07 5 240
Table IA records the same glass compositions but reported in terms
of mole percent on the oxide basis.
TABLE IA 1 2 3 4 5 6 SiO.sub.2 72.43 80.18 63.56 68.05 64.03 75.05
Al.sub.2 O.sub.3 5.33 9.38 16.36 5.02 9.20 5.48 B.sub.2 O.sub.3
7.52 0.00 6.48 5.28 5.04 0.00 MgO 5.16 0.00 0.00 0.39 5.12 0.00 CaO
0.00 0.00 0.00 20.19 8.72 7.09 SrO 8.39 0.28 9.33 0.00 3.49 8.67
BaO 0.97 9.93 4.04 0.90 4.18 3.51 7 8 9 10 11 12 SiO.sub.2 63.65
62.03 73.34 61.56 62.46 56.70 Al.sub.2 O.sub.3 14.96 15.94 5.27
10.57 15.70 14.39 B.sub.2 O.sub.3 0.67 0.00 0.00 0.00 0.00 0.00 MgO
1.23 11.05 9.90 0.33 10.76 15.59 CaO 8.63 0.42 0.00 18.83 0.81 3.72
SrO 0.27 0.34 8.20 0.00 0.26 8.42 BaO 10.35 9.97 3.09 8.54 9.82
0.95
An examination of the above glasses illustrates the care in
composition control that must be exercised in preparing glasses to
provide the several properties that characterize the present
invention. Thus, compositions 1, 4 and 9 are quite similar, except
that 1 has a substantial SrO content, 4 has a substantial CaO
content, and 9 omits B.sub.2 O.sub.3 in favor of BaO. The
consequence is a continuously higher strain point from 1 to 4 to 9,
with 1 being marginally acceptable.
Comparisons also illustrate the effect of various oxide contents on
durability. Thus, comparing compositions 11 and 12 indicates that
substituting alkaline earth metal oxides has an enormous effect on
durability. Also, comparing compositions 1 and 6 suggests the
beneficial effect of omitting B.sub.2 O.sub.3 in favor of alkaline
earth metal oxides.
As noted earlier, a preferred CTE range for glass panels compatible
with Code 7059 glass is 45-50.times.10.sup.-7 /.degree.C. Glasses
in aluminosilicate sub-families A' and B' have CTEs in this range
and have compositions consisting essentially of, as calculated in
weight percent on an oxide basis:
A' B' SiO.sub.2 50-57 55-67 Al.sub.2 O.sub.3 16-20 6-<13 B.sub.2
O.sub.3 0-5.5 0-7.5 MgO 2-2.75 2-6.5 CaO 1-<7 0-17.5 SrO 0.5-15
0-14.5 BaO 1-21 2-9.5
TABLE II sets forth exemplary compositions within these
sub-families. Compositions 13, 14 and 15 exemplify the A'
sub-family, while 16, 17 and 18 exemplify the B' sub-family.
TABLE II 13 14 15 16 17 18 SiO.sub.2 56.1 52.9 53.9 65.5 56.6 66.9
Al.sub.2 O.sub.3 17.0 18.2 18.0 8.1 11.2 6.1 B.sub.2 O.sub.3 -- 2.0
4.7 -- 7.4 -- MgO 2.3 2.4 2.4 6.1 2.2 6.2 CaO 6.8 6.9 6.5 5.2 2.1
-- SrO 5 5.1 5.1 12.9 12.0 13.3 BaO 12.9 12.6 9.6 2.2 8.7 7.5 CTE
48.3 48.4 45.3 48.1 47.3 45.5 Strain 718 695 677 693 650 699 HCl
0.08 0.62 1.9 0.03 0.3 0.01 Density 2.31 2.80 2.70 2.70 2.72
2.73
Preferred CTE ranges for glass panels adapted to use with silicon
have been noted as having a CTE range of 32-40.times.10.sup.-7
/.degree.C. Glasses in aluminosilicate sub-families C' and D' have
CTEs within that range and have compositions that consist
essentially of, as calculated in weight percent on an oxide
basis:
C' D' SiO.sub.2 54-57 57-65.5 Al.sub.2 O.sub.3 17.5-23 8-13 B.sub.2
O.sub.3 5-15 4-13 MgO 2-2.75 2-3.5 CaO 1.5-<7 0-6.5 SrO 2-6 0-13
BaO 0.5-9.5 2-21
TABLE III sets forth exemplary compositions within these
sub-families. The C' sub-family is exemplified by compositions 19,
20 and 21, while the D' sub-family is exemplified by compositions
22, 23 and 24.
TABLE III 19 20 21 22 23 24 SiO.sub.2 56.6 55.5 56.2 64.6 65 64.3
Al.sub.2 O.sub.3 22.4 18.4 22.9 12.9 8.2 13 B.sub.2 O.sub.3 7.8 9.3
5.9 4.4 7.8 4.4 MgO 2.3 2.3 2.4 2.2 3.1 2.2 CaO 3.4 6.9 4.9 6.3 --
6.3 SrO 4.9 5.0 5.0 0.8 13 1.2 BaO 2.6 2.6 2.7 8.8 2.2 8.7 CTE 32.2
40 35.4 38.8 38.6 38.8 Strain 692 666 706 683 692 686 HCl 1.8 2.6
0.8 0.02 2.7 0.02 Density 2.52 2.54 2.56 2.55 2.54 2.56
In a preferred embodiment of the invention, a glass panel for a
flat panel display has a strain point greater than 660.degree. C.
and has a weight loss less than 1 mg/cm.sup.2 in the HCl test
described earlier. We have found that glasses having compositions
falling within two aluminosilicate sub-families meet these
preferred qualifications. The two families, E and F, have
compositions consisting essentially of, as calculated in weight
percent on an oxide basis:
E F SiO.sub.2 54-58 55-67 Al.sub.2 O.sub.3 16-23 6-14 B.sub.2
O.sub.3 0-6 0-7.5 MgO 2-4.5 0-7 CaO 1-12.5 0-18.5 SrO 2.5-15.5 0-15
BaO 0-14.5 1-21 MgO + CaO + SrO + BaO 15-27 18-28
TABLES IVE and IVF set forth, in approximate weight percent as
analyzed on an oxide basis, the compositions and relevant
properties of several representative examples of each sub-family,
respectively:
TABLE IVE 25 26 27 28 29 30 SiO.sub.2 55.16 56.95 56.7 57.63 58.19
54.69 Al.sub.2 O.sub.3 18.19 16.81 22.63 19.21 19.43 17.79 B.sub.2
O.sub.3 0.95 0 0.997 5.33 5.35 0.94 MgO 2.23 2.25 2.31 2.6 2.67
2.17 CaO 1.46 4.7 6.7 8.63 8.76 1.39 SrO 13.06 4.82 4.86 5.5 5.61
14.25 BaO 8.94 14.47 5.77 1.09 0 8.76 CTE 45.4 46.8 41.8 42 41 46.8
Strain 731 724 748 684 688 722 HCl 0.074 0.06 0.57 0.16 0.48 0.11
Density 2.79 2.429 2.676 2.579 2.564 2.819
TABLE IVF 31 32 33 34 35 36 SiO.sub.2 55.7 55.53 56.9 65.49 66.93
66.85 Al.sub.2 O.sub.3 13.6 13.3 13.03 8.14 6.1 6.23 B.sub.2
O.sub.3 5.1 3.2 7.3 0 0 0 MgO 3 2.27 2.2 6.08 6.23 0.13 CaO 7.1
4.08 0 5.16 0 5.69 SrO 5.2 12.59 11.9 12.92 13.26 13.29 BaO 9.3
9.03 8.7 2.22 7.48 7.8 CTE 46.8 50.2 45 48.1 45.5 50.9 Strain 662
675 662 693 699 699 HCl 0.22 0.076 0.31 0.03 0.0134 0.0058 Density
2.705 2.799 2.692 2.695 2.725 2.741
A further preferred embodiment constitutes glass panels having a
density less than 2.5 grams/cc. Glasses meeting this requirement
fall within an aluminosilicate sub-family G having the following
constituent ranges consisting essentially of, as analyzed on an
oxide basis:
SiO.sub.2 54.8-57 Al.sub.2 O.sub.3 16.8-21.8 B.sub.2 O.sub.3 0-14
MgO 2.2-2.5 CaO 1.5-9.5 SrO 4.5-5.5 BaO 0.1-14.5 MgO + CaO + SrO +
BaO 12.5-27
TABLE V sets forth in approximate weight percent, as analyzed on an
oxide basis, compositions and relevant properties for
representative examples:
TABLE V 37 38 39 40 41 42 SiO.sub.2 55.9 56.08 56.95 56.14 56.6
56.72 Al.sub.2 O.sub.3 21.73 16.98 16.81 21.1 16.92 19.04 B.sub.2
O.sub.3 9.76 0 0 1.06 0.99 9.73 MgO 2.45 2.28 2.25 2.28 2.31 2.37
CaO 2.36 6.78 4.7 5.59 9.4 6.95 SrO 5.13 5 4.82 4.84 4.78 5.07 BaO
2.67 12.86 14.47 8.99 8.91 0.12 CTE 31.2 48.3 46.8 43.6 49.3 37.6
Strain 680 718 724 737 710 670 HCl 3.36 0.08 0.06 0.27 0.15 4.15
Density 2.496 2.312 2.429 2.467 2.265 2.494
* * * * *