US 2022/0411316 A1Published application

Prestressing a flat glass by generating a gradient in the surface composition

AssigneeSchott AG

InventorsUlrich Fotheringham, Gerhard Lautenschläger, Rainer Erwin Eichholz, Jochen Alkemper

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Abstract

The invention relates to glass articles, in particular flat glasses, in the case of which the surface material has gradient material properties as a result of targeted process control which in turn lead to compressive prestressing of the surface. The invention also relates to a method for producing the glass articles and the use thereof.

Claims20

Dependent claims

A glass article, comprising:

three portions comprising an upper side surface glass, a core glass, and an underside surface glass, the upper side surface glass and the underside surface glass being present in each case to a depth of <20 nm and the core glass is present in any event at 500 nm depth, a sum of proportions of tin oxide and bismuth oxide in the underside surface glass is greater than a sum of proportions of tin oxide and bismuth oxide in the upper side surface glass, the core glass having a CTEK calculated according to the following formulas (13) and (14) in a range from 2.5 to 5.0 ppm/K:
E
pot
_
=
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
·
E
pot
,
j
∑
i
=
1
n
c
i
·
∑
i
=
1
m
z
i
,
j
,
(
54
)
CTE
Glass
=
(
50116.33042
(
kJ
Mol
)
E
pot
_
-
26.1724514
)
⁢
ppm
/
K
,
(
55
)
wherein m is a number of cation types which occur, Epot,j is a potential well depth tabulated for a jth cation type, and zi,I is a number of cations of the jth type in an ith constituent phase;
the upper side surface glass having a CTEO calculated according to the formula (14) and the following formulas (15) and (16) which is lower by at least 0.6 ppm/K in comparison with the CTEK of the core glass calculated according to the formulas (29) and (30):
E
pot
_
=
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
·
E
pot
,
j
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
=
∑
j
=
1
m
(
∑
i
=
1
n
c
i
·
z
i
,
j
)
·
E
pot
,
j
∑
i
=
1
m
(
z
i
=
1
n
⁢
c
i
·
z
i
,
j
)
,
(
56
)
∑
i
=
1
n
c
i
·
z
i
,
j
=
k
j
·
x
j
;
(
57
)
and wherein according to the following formula (10) a compressive prestress σO on the upper side surface of at least 50 MPa is produced if the values of the core glass calculated according to the following formulas (31), (29), and (37) are used for E/(1−μ) and TG and a difference CTEK−CTEO between the CTE values calculated for core glass and upper side surface glass is used for ΔCTE:
σ
O
=
E
1
-
μ
·
(
T
G
-
T
ambient
)
·
Δ
⁢
CTE
,
(
58
)
μ
=
0.17
+
Δ
⁢
μ
f
+
Δ
⁢
μ
x
,
(
59
)
E
=
(
0.683888667
(
2
·
(
1
+
μ
)
·
f
·
E
pot
_
·
s
V
m
⁢
o
⁢
l
)
-
39.4242404
)
⁢
GPa
,
(
60
)
1
V
⁢
A
-
T
G
=
(
0.002665819
·
f
W
+
0.001119212
)
·
1
K
,
(
61
)
wherein TG is an annealing point of the glass, VA is a working point of the glass, E is a modulus of elasticity of the glass, μ is Poisson's ratio of the glass, Tambient is an ambient temperature,
Δ
⁢
μ
f
=
-
[
(
1
+
μ
)
⁢
(
1
-
2
⁢
μ
)
3
⁢
1
f
]
⁢
Δ
⁢
f
,
and
⁢
f
=
Angle
⁢
condition
⁢
number
⁢
p
.
A
.
-
(
2
3
)
⁢
(
3
⁢
D
⁢
angle
degrees
⁢
of
⁢
freedom
⁢
number
⁢
p
.
A
.
-
angle
degrees
⁢
of
⁢
freedom
⁢
number
⁢
p
.
A
.
)
Angle
⁢
condition
⁢
number
⁢
p
.
A
.
.

379 more elements

A method for producing a glass article, comprising:

melting glass raw materials;
forming a glass article from the glass melt;
and
cooling the glass article;
wherein the glass article comprises three portions comprising an upper side surface glass, a core glass, and an underside surface glass, the upper side surface glass and the underside surface glass being present in each case to a depth of <20 nm and the core glass is present in any event at 500 nm depth, a sum of proportions of tin oxide and bismuth oxide in the underside surface glass is greater than a sum of proportions of tin oxide and bismuth oxide in the upper side surface glass, the core glass having a CTEK calculated according to the following formulas (13) and (14) in a range from 2.5 to 5.0 ppm/K:
E
pot
_
=
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
·
E
pot
,
j
∑
i
=
1
n
c
i
·
∑
i
=
1
m
z
i
,
j
,
(
63
)
CTE
Glass
=
(
50116.33042
(
kJ
Mol
)
E
pot
_
-
26.1724514
)
⁢
ppm
/
K
,
(
64
)
wherein m is a number of cation types which occur, Epot,j is a potential well depth tabulated for a jth cation type, and zj,I is a number of cations of the jth type in an ith constituent phase;
the upper side surface glass having a CTEO calculated according to the formula (14) and the following formulas (15) and (16) which is lower by at least 0.6 ppm/K in comparison with the CTEK of the core glass calculated according to the formulas (29) and (30):
E
pot
_
=
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
·
E
pot
,
j
∑
i
=
1
n
c
i
·
∑
i
=
1
m
z
i
,
j
=
∑
j
=
1
m
(
∑
i
=
1
n
c
i
·
z
i
,
j
)
·
E
pot
,
j
∑
j
=
1
m
(
∑
i
=
1
n
c
i
·
z
i
,
j
)
,
(
65
)
∑
i
=
1
n
c
i
·
z
i
,
j
=
k
j
·
x
j
;
(
66
)
and wherein according to the following formula (10) a compressive prestress σO on the upper side surface of at least 50 MPa is produced if the values of the core glass calculated according to the following formulas (31), (29), and (37) are used for E/(1−μ) and TG and a difference CTEK−CTEO between the CTE values calculated for core glass and upper side surface glass is used for ΔCTE:
σ
O
=
E
1
-
μ
·
(
T
G
-
T
ambient
)
·
Δ
⁢
CTE
,
(
67
)
μ
=
0.17
+
Δ
⁢
μ
f
+
Δ
⁢
μ
x
,
(
68
)
E
=
(
0.683888667
(
2
·
(
1
+
μ
)
·
f
·
E
pot
_
·
z
V
m
⁢
o
⁢
l
)
-
39.4242404
)
⁢
GPa
,
(
69
)
1
V
⁢
A
-
T
G
=
(
0.002665819
·
f
W
+
0.001119212
)
·
1
K
,
(
70
)
wherein TG is an annealing point of the glass, VA is a working point of the glass, E is a modulus of elasticity of the glass, μ is Poisson's ratio of the glass, Tambient is an ambient temperature,
Δ
⁢
μ
f
=
-
[
(
1
+
μ
)
⁢
(
1
-
2
⁢
μ
)
3
⁢
1
f
]
⁢
Δ
⁢
f
,
and
⁢
f
=
Angle
⁢
condition
⁢
number
⁢
p
.
A
.
-
(
2
3
)
⁢
(
3
⁢
D
⁢
angle
⁢
degrees
of
⁢
freedom
⁢
number
⁢
p
.
A
.
-
angle
⁢
degrees
of
⁢
freedom
⁢
number
⁢
p
.
A
.
)
Angle
⁢
condition
⁢
number
⁢
p
.
A
.

381 more elements

Dependencies are inferred from the claim text.

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Abstract

A glass article, comprising:

three portions comprising an upper side surface glass, a core glass, and an underside surface glass, the upper side surface glass and the underside surface glass being present in each case to a depth of <20 nm and the core glass is present in any event at 500 nm depth, a sum of proportions of tin oxide and bismuth oxide in the underside surface glass is greater than a sum of proportions of tin oxide and bismuth oxide in the upper side surface glass, the core glass having a CTEK calculated according to the following formulas (13) and (14) in a range from 2.5 to 5.0 ppm/K:
E
pot
_
=
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
·
E
pot
,
j
∑
i
=
1
n
c
i
·
∑
i
=
1
m
z
i
,
j
,
(
54
)
CTE
Glass
=
(
50116.33042
(
kJ
Mol
)
E
pot
_
-
26.1724514
)
⁢
ppm
/
K
,
(
55
)
wherein m is a number of cation types which occur, Epot,j is a potential well depth tabulated for a jth cation type, and zi,I is a number of cations of the jth type in an ith constituent phase;
the upper side surface glass having a CTEO calculated according to the formula (14) and the following formulas (15) and (16) which is lower by at least 0.6 ppm/K in comparison with the CTEK of the core glass calculated according to the formulas (29) and (30):
E
pot
_
=
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
·
E
pot
,
j
∑
i
=
1
n
c
i
·
∑
j
=
1
m
z
i
,
j
=
∑
j
=
1
m
(
∑
i
=
1
n
c
i
·
z
i
,
j
)
·
E
pot
,
j
∑
i
=
1
m
(
z
i
=
1
n
⁢
c
i
·
z
i
,
j
)
,
(
56
)
∑
i
=
1
n
c
i
·
z
i
,
j
=
k
j
·
x
j
;
(
57
)
and wherein according to the following formula (10) a compressive prestress σO on the upper side surface of at least 50 MPa is produced if the values of the core glass calculated according to the following formulas (31), (29), and (37) are used for E/(1−μ) and TG and a difference CTEK−CTEO between the CTE values calculated for core glass and upper side surface glass is used for ΔCTE:
σ
O
=
E
1
-
μ
·
(
T
G
-
T
ambient
)
·
Δ
⁢
CTE
,
(
58
)
μ
=
0.17
+
Δ
⁢
μ
f
+
Δ
⁢
μ
x
,
(
59
)
E
=
(
0.683888667
(
2
·
(
1
+
μ
)
·
f
·
E
pot
_
·
s
V
m
⁢
o
⁢
l
)
-
39.4242404
)
⁢
GPa
,
(
60
)
1
V
⁢
A
-
T
G
=
(
0.002665819
·
f
W
+
0.001119212
)
·
1
K
,
(
61
)
wherein TG is an annealing point of the glass, VA is a working point of the glass, E is a modulus of elasticity of the glass, μ is Poisson's ratio of the glass, Tambient is an ambient temperature,
Δ
⁢
μ
f
=
-
[
(
1
+
μ
)
⁢
(
1
-
2
⁢
μ
)
3
⁢
1
f
]
⁢
Δ
⁢
f
,
and
⁢
f
=
Angle
⁢
condition
⁢
number
⁢
p
.
A
.
-
(
2
3
)
⁢
(
3
⁢
D
⁢
angle
degrees
⁢
of
⁢
freedom
⁢
number
⁢
p
.
A
.
-
angle
degrees
⁢
of
⁢
freedom
⁢
number
⁢
p
.
A
.
)
Angle
⁢
condition
⁢
number
⁢
p
.
A
.
.

379 more elements