U.S. patent application number 15/283933 was filed with the patent office on 2017-04-06 for long-term bendable glass material, and method for the production of a long-term bendable glass material.
This patent application is currently assigned to Schott AG. The applicant listed for this patent is Schott AG. Invention is credited to Andreas Habeck, Markus Hei -Chouquet, Kurt Nattermann, Clemens Ottermann, Thomas Ro meier, Jurgen Vogt.
Application Number | 20170096364 15/283933 |
Document ID | / |
Family ID | 58355954 |
Filed Date | 2017-04-06 |
United States Patent
Application |
20170096364 |
Kind Code |
A1 |
Ottermann; Clemens ; et
al. |
April 6, 2017 |
LONG-TERM BENDABLE GLASS MATERIAL, AND METHOD FOR THE PRODUCTION OF
A LONG-TERM BENDABLE GLASS MATERIAL
Abstract
A long-term bendable glass material includes a glass material
having a bending radius in a range of 1 mm to 10.sup.7 mm. The
glass material is structured such that a number of breaks
developing over a course of time after a storage period of at least
one day displays a remaining probability of breaking of less than
0.1 for a storage time period of a maximum of half a year.
Inventors: |
Ottermann; Clemens;
(Hattersheim, DE) ; Nattermann; Kurt; (Ockenheim,
DE) ; Hei -Chouquet; Markus; (Bischofsheim, DE)
; Vogt; Jurgen; (Oberheimbach, DE) ; Ro meier;
Thomas; (Bodenheim, DE) ; Habeck; Andreas;
(Undenheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schott AG |
Mainz |
|
DE |
|
|
Assignee: |
Schott AG
Mainz
DE
|
Family ID: |
58355954 |
Appl. No.: |
15/283933 |
Filed: |
October 3, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03C 3/085 20130101;
B65H 75/08 20130101; C03C 3/091 20130101; C03B 23/0066 20130101;
G01N 3/20 20130101; C08K 3/40 20130101; B65H 2701/1842 20130101;
B32B 17/064 20130101 |
International
Class: |
C03C 3/091 20060101
C03C003/091; G01N 3/20 20060101 G01N003/20; C08K 3/40 20060101
C08K003/40; B65H 75/08 20060101 B65H075/08; C03B 23/00 20060101
C03B023/00; C03C 3/085 20060101 C03C003/085 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2015 |
DE |
10 2015 219 069.2 |
Sep 21, 2016 |
DE |
10 2016 218 176.9 |
Claims
1. A long-term bendable glass material, comprising: a glass
material having a bending radius in a range of 1 mm to 10.sup.7 mm,
said glass material being structured such that a number of breaks
developing over a course of time after a storage period of at least
one day displays a remaining probability of breaking of less than
0.1 for a storage time period of a maximum of half a year.
2. The long-term bendable glass material according to claim 1,
wherein said glass material is a glass ribbon having a maximum
thickness of 500 .mu.m and a minimum thickness of 3 .mu.m.
3. The long-term bendable glass material according to claim 1,
wherein said bending radius is between 10 mm to 10.sup.3 mm.
4. The long-term bendable glass material according to claim 1,
wherein said remaining probability of breaking is less than
0.01.
5. The long-term bendable glass material according to claim 1,
wherein said glass material comprises the following components in
weight-%: SiO.sub.2 40-75; Al.sub.2O.sub.3 1-25; B.sub.2O.sub.3
0-16; alkaline earth oxide 1-30; and alkali oxide 0-20.
6. The long-term bendable glass material according to claim 1,
wherein said glass material is wound onto a roll and is under a
tensile stress that is less than: 1.15 Min ( .sigma. _ a - .DELTA.
a 0.4 ( 1 - ln ( A ref A App .PHI. ) ) , .sigma. _ e - .DELTA. e
0.4 ( 1 - ln ( L ref L App .PHI. ) ) ) , ##EQU00004## whereby
.sigma..sub.a and .sigma..sub.e are average values of tensile
stress on breakages of samples of glass material that are subjected
to bending stresses, whereby L.sub.ref describes an edge length and
A.sub.ref describes a surface of a sample, whereby .sigma..sub.a is
the average value of the tensile stress in the surface of the
sample during breaking, and .sigma..sub.e is the average value of
the tensile stress on a break originating from the edge of the
sample, and whereby .DELTA..sub.e and .DELTA..sub.a are standard
deviations of the average values .sigma..sub.e or respectively
.sigma..sub.a, and whereby A.sub.app is a surface of glass material
and L.sub.app a sum of edge lengths of opposite edges of glass
material and .PHI. a maximum breakage quota of 0.1 at most within a
time period of at least half a year.
7. A method for producing long-term bendable glass material,
comprising: bending a glass material in a bending radius in a range
of 1 mm to 10.sup.7 mm; storing said bent glass material for a time
period of at least 1 day; inspecting at least a portion of said
bent glass material for damage after said storing; and classifying
said inspected bent glass material as a reject if damage is
detected or as a long-term bendable glass material if no damage is
detected.
8. The method according to claim 7, further comprising winding said
glass material onto a roll, said glass material having a maximum
thickness of 500 .mu.m and a minimum thickness of 3 .mu.m.
9. The method according to claim 8, further comprising rewinding
said wound glass material from said roll onto a second roll.
10. The method according to claim 7, wherein said glass material
comprises the following components in weight-%: SiO.sub.2 40-75;
Al.sub.2O.sub.3 1-25; B.sub.2O.sub.3 0-16; alkaline earth oxide
0-30; and alkali oxide 0-20.
11. The method according to claim 7, wherein said inspected glass
material is a cut-off of said bent glass material.
12. The method according to claim 7, wherein said glass material
comprises at least one coating.
13. The method according to claim 7, further comprising
pre-treating said glass material prior to said bending.
14. The method according to claim 7, wherein said glass material is
a composite material having a polymer film.
15. The method according to claim 7, wherein said glass material is
stored at least one of at a relative humidity in a range between
40% and 100% and at a temperature in a range between 10.degree. C.
and 30.degree. C.
16. A method for proof testing glass material, comprising: bending
a glass material; storing said bent glass material for a period of
at least 1 day; determining a crack depth in said glass material
after said storing; comparing said determined crack depth with a
predefined crack depth; and classifying said glass material as a
long-term bendable glass material if said crack depth is less than
said predetermined crack depth such that a remaining probability of
breaking is less than 0.1 for a maximum storage period of half a
year.
17. The method according to claim 16, further comprising defining
said predetermined crack depth as ((K.sub.1cR)/(Ed)).sup.2, wherein
K.sub.1c is a fracture toughness of said glass material, R is a
bending radius of said glass material, E is an elasticity modulus
of said glass material, and d is a thickness of said glass
material.
18. The method according to claim 17, wherein at least one of said
fracture toughness is in a range of 0.1 to 1.5 MPa m, said
elasticity modulus is in a range of 40 to 150 GPa, and said bending
radius is in a range of 1 mm to 10.sup.7 mm.
19. The method according to claim 16, wherein said glass material
comprises the following components in weight-%: SiO.sub.2 40-75;
Al.sub.2O.sub.3 1-25; B.sub.2O.sub.3 0-30; and alkali oxide
0-20.
20. The method according to claim 16, wherein said glass material
comprises at least one coating.
21. The method according to claim 16, further comprising
pre-treating said glass material prior to said bending.
22. The method according to claim 16, wherein said glass material
is a composite material having a polymer film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a long-term bendable glass
material. The invention also relates to a method for the production
of a long-term bendable glass material and its use as a curved
glass substrate.
[0003] 2. Description of the Related Art
[0004] Glasses having thicknesses of less than 500 .mu.m--so-called
thin glasses--are used in many fields of technology, e.g.,
displays, screens for optoelectronic components, encapsulations and
electric insulating layers.
[0005] In order to be able to handle thin glasses in further
processing, as well as in storage and transportation, the thin
glass ribbon can be wound into a roll. Thus, the glass can be
directly unwound from the roll and worked with during subsequent
processing. However, one problem hereby is that glass ribbons can
be damaged after having been produced; for example, the glass
ribbon may have damage along the edges, or cracks. During winding,
the glass ribbon is moreover subjected to stresses, such as bending
stresses in the glass. These damages and stresses, in particular
bending stresses, can result in breakages of the wound glass
ribbons. A single breakage can cause considerable problems due to
the finishing process having to be interrupted during unwinding of
the ribbon at the breakage point. Breaking of the wound glass
ribbon can result in situations where damaged glass surfaces that,
for example, have cracks in the edge region of the glass ribbon
cause crack progression or even breaking to occur. Such a thin
glass is, in addition, also used as a curved glass substrate, for
example, as a cover glass for a curved display, whereby it is
continuously subjected to tensile stress on one side.
[0006] It must hereby be ensured that a crack progression that
could result in a crack or break is made impossible.
[0007] US 2013/0196 163 A1 describes a method for bending of glass,
wherein a glass web is laminated onto a reinforcing film so that
during bending the neutral plane of the deflection curve is located
in the reinforcing film and the glass web in its entirety is
located in the deflection-induced compressive stress zone. This
requires reinforcing films whose thickness is a multiple of the
glass thickness. A slow spreading and thus glass-hard curing
adhesive with high strength must be used for the laminate. With the
high strength, however, problems can arise if the adhesive cannot
easily be removed or removed at all. In any case, the removal of
the adhesive represents an additional necessary processing step
prior to customization cutting. Moreover, the winding direction is
defined. In regard to the breaking strength of the wound glass, the
spread of the adhesion and a stress relaxation in the strengthening
film must be considered. If, due to the stress relaxation, the
neutral plane migrates into the glass web, the glass incurs tensile
stress that can even increase during unwinding.
[0008] U.S. Pat. No. 8,241,751 describes a glass roll with a low
instantaneous likelihood of breakage if a minimum bending radius is
adhered to for the curvatures. However, the document does not
address the aspect of delayed breaks. In particular, breaks that
occur on the edges of the glass ribbon are also ignored. For the
dimensioning standards described in the document, glass breakage is
to be expected within a very short time period.
[0009] WO 2012/176594 A1 suggests that, during transfer of one roll
to the next roll, a relative humidity of 40% rF or less should be
adhered to in order to avoid a break during the transfer. This
should reduce the likelihood of breaks. The method suggested in WO
2012/176 594 A1 shows the best results for relative humidity of
<1%. The method according to WO 2012/176594 A1, however, only
serves the short-term stabilization of the glass ribbon during
processing while significantly reducing the humidity. A long-term
stabilization improvement of the thin glass in general further
processing, or as end product, is not achieved.
[0010] A glass element having a thickness of 25 .mu.m to 125 .mu.m
has become known from U.S. Pat. No. 9,321,679. From U.S. Pat. No.
9,321,679 it became evident that, with a radius of curvature of 3
mm to 20 mm at 25.degree. C. for at least 60 minutes, no breakage
occurs in the glass material. Weibull distributions for
verification of the advantages of the etch step are also
illustrated in U.S. Pat. No. 9,321,679. Not shown in U.S. Pat. No.
9,321,679 is a proof-test for long-term bendable glass material, or
criteria that can be applied to a long-term bendable glass
material.
[0011] Generally, glass materials having a thickness of <500
.mu.m--so-called thin glasses--are not immediately processed
further. Rather, the glass material is wound into rolls and stored
for a certain period of time. Transportation from storage to an
establishment conducting further processing causes additional
dynamic loads.
[0012] In wound glass rolls, the glass is generally under stress,
such as bending stress. In addition, glass ribbons have edge damage
or cracks. This can result in the wound glass ribbons breaking,
thus rendering further processing impossible. It is therefore
desirable to provide a criterion, or proof-test, that permits
statements of whether a glass material is long-term bendable. A
proof-test is a momentary test and is characterized in that a
target value is specified, an actual value is determined, and the
actual value is compared to the target value. If, for example, in a
proof-test for a long-term bendable glass material the actual value
is the crack depth and the crack depth is less than the target
value, such as a specified crack depth, then the wound glass
material is classified as long-term bendable
[0013] What is needed in the art is a long-term bendable glass
material which can be stored over a long period of time with a very
low probability of breaking.
SUMMARY OF THE INVENTION
[0014] The present invention provides a long-term bendable glass
material as a thin glass, which is stored or used, whereby tensile
stress acting over a long time period upon one side and which
during further processing of a stored glass roll or during the
course of the long-term use has a very low probability of breaking
or whereby breakage is avoided.
[0015] In addition, a method to produce a long-term bendable glass
material, use of a long term-bendable glass material and a
proof-test for long-term bendable glass material is provided.
[0016] During a proof-test for a long-term bendable glass material,
the actual value, namely the crack depth, is compared with a target
value, namely the specified crack depth. If the actual value is
less than the target value, then a glass material is classified as
long-term bendable. With a glass material so classified, the
probability of breaking is below 0.1. The crack depth is a measure
for the edge stability. The crack depth is thereby a measure for
the breaking stress. The critical crack depth for a glass material
from which point in time breaking occurs due to tension stress is
determined by the following glass parameters: fracture toughness of
the glass material, the elasticity modulus of the glass material,
the thickness of the glass material and the bending radius of the
glass material. The following applies for crack depth a.sub.c:
a.sub.c=((K.sub.1cR)/(Ed)).sup.2, whereby K.sub.1c is the fracture
toughness, R is the bending radius, E is the elasticity radius and
d is the thickness of the glass material. For current glass
materials the fracture toughness is in the range of 0.1 to 1.5 MPa
m. With an elasticity modulus of 75 GPa, a thickness of 100 .mu.m,
and a bending radius of 75 mm, a critical or specified crack depth
of 49 .mu.m results. According to such a proof-test, every glass
roll having a crack depth greater than 49 .mu.m, for example 60
.mu.m, is classified as non-long-term bendable. If the crack depth
is less than 49 .mu.m, for example 30 .mu.m, the glass material is
categorized as long-term bendable, since then also during storage
over a time period of at least 1 day, such as 5 days, 10 days, 50
days, or 300 days, a remaining probability of breaking of less than
0.05, such as 0.01, is achieved for a storage time period of a
maximum of at least half a year (6 months), such as one year, 2
years, or a maximum of 5 years.
[0017] A glass will generally break as soon as the specified crack
depth is exceeded.
[0018] According to one aspect of the present invention, a
long-term bendable glass material, which can be in the form of a
glass material wound onto a roll, such as a glass ribbon having a
thickness of less than 500 .mu.m, such as 350 .mu.m, and a minimum
thickness of 5 .mu.m, such as 20 .mu.m to 200 .mu.m, is provided
whereby the long-term bendable glass material is structured such
that the number of breaks N(t) in a bent glass having a bending
radius R in the range of 1 mm to 10.sup.7 mm, such as 5 mm to
10.sup.6 mm or 10 to 10.sup.3 mm, developing over the course of
time only displays a very low, or no, probability of breaking after
a storage period of at least one day, such as at least 3 days, at
least 5 days, at least 7 days, at least 10 days, at least 50 days,
at least 150 days, or at least 300 days. In the present
application, "low probability of breaking or remaining probability
of breaking" refers to a probability of breaking .PHI. of less than
0.1, such as less than 0.05, or less than 0.01 for a maximum
storage period of at least half a year, such as one year, 2 years
or 5 years. These probabilities of breaking are attained if the
depth of cracks in the glass material do not exceed certain values.
The critical crack depth from which breaking occurs is
a.sub.c=((K.sub.1cR)/(Ed)).sup.2.
[0019] In a proof-test, this critical depth of cracks is the
specified depth of cracks (target-value). Surprisingly, it has been
demonstrated that a probability of breaking--according to the
present invention--of less than 0.1 is achieved, if the depth of
cracks is less than previously stated.
[0020] Glasses which possess such characteristics distinguish
themselves through a very low probability of breaking with
long-term bendability, as well as long-term storage in roll form or
long-term use as curved substrate.
[0021] The glass material can be one having a thickness of less
than 500 .mu.m, such as less than 350 .mu.m, and a minimum
thickness of 3 .mu.m. The glass thickness can be within the range
of 20 .mu.m to 200 .mu.m. Exemplary glass thicknesses are 5, 10,
15, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210 or 280
.mu.m.
[0022] If the glass is wound onto a roll, the core diameter of the
roll can be greater than 75 mm, such as greater than 100 mm,
greater than 150 mm, greater than 300 mm, greater than 400 mm,
greater than 500 mm, or greater than 600 mm.
[0023] Surprisingly, it has been demonstrated that the glasses
formed according to the present invention, such as those in the
form of thin glass ribbons or thin glass laminate ribbons that are
wound bent onto rolls, are clearly more stable in further
processing than curved glasses, which can be in the form of glass
rolls that do not achieve the cited probabilities of breaking of
less than 0.1 after the specified times. An additional advantage of
the present invention is that thin glass ribbons, or thin glass
laminate ribbons, that have critical cracks and damage along edges
are very easily recognized and can be discarded.
[0024] In order to increase the stability of glass rolls, provision
can be made to rewind the wound glass rolls after a certain storage
time period. Rewinding may, for example, occur in a roll-to-roll
process.
[0025] Surprisingly, it was noted that glass ribbons displaying the
described breaking behavior and which, during the cited storage
period of at least one day, such as at least 3 days, at least 5
days, at least 7 days, at least 10 days, at least 50 days at least
150 days, or at least 300 days have a probability of breaking .PHI.
of less than 0.1, such as less than 0.05 or less than 0.01 for a
maximum storage period of half a year, such as one year, 2 years,
and 5 years and possess clear stabilization and higher durability
in subsequent processing and further conversion. In particular,
they distinguish themselves through long-term bendability. The
probability of breaking indicates the probability of a break. 0.1
hereby corresponds to a probability of 10%, 0.05 to a probability
of 5%, 0.03 to a probability of 3% and 0.01 to a probability of 1%.
The glass ribbons can be wound onto glass rolls.
[0026] The consistencies of all samples ensue from a Weibull
distribution. The reason for this is the static distribution of the
lengths of the micro-cracks, in other words of the crack depth of
the micro-cracks. As soon as the underlying distribution is known,
a probability of breaking at certain stresses can be specified for
each sample. This probability of breaking, however, also depends
upon the length of the sample. The longer the sample, the more
probable it is that a longer crack occurs. The parameters of a
Weibull distribution that were measured by a (destructive) test on
one sample set (all samples having the same length L.sub.0) are:
.sigma.=characteristic breaking stress and m=Weibull modulus. If
both these parameters for edge- and surface processing, and the
size of the samples with which these parameters were determined,
are known, then the probability of breaking .PHI.(.sigma.) can thus
be calculated for a sample with length L that was under tensile
stress as:
.PHI.(.sigma.)=1-exp{-(L/L.sub.0)(.sigma./.sigma..sub.0).sup.m).
[0027] With glasses that are subjected to the proof-test,
subcritical crack growth occurs during tensile stress. This means
that all cracks that reach the critical crack length during the
time period of the proof-test will result in a break. The storage
is therefore a test with which all micro-cracks that are not
shorter than the critical crack length are rejected. Cracks that do
not lead to a break within the proof-test, will also not lead to a
break subsequently.
[0028] Surprisingly, it was demonstrated that with glass material
that was classified in the proof-test as being sufficiently stable,
an increase in strength occurred. A reason for this is a filleting
of the crack tips and thus a resulting increase in strength. As was
surprisingly demonstrated, a glass that survived the proof-test can
be subjected to considerably greater stress than is applied in the
proof-test without the glass breaking, since a strengthening occurs
in the glass. The stress to which the glass is subjected may be
5-20% greater than stress determined by the bending radius in the
proof-test.
[0029] According to one embodiment of the present invention, the
wound glass ribbons are placed onto a roll core immediately
following production. Subsequently, they are stored, whereby prior
to placement onto the roll core, borders--if present--are trimmed
from the glass ribbon. The duration of storage of the wound glass
ribbons for the proof-test is at least one day and can be a maximum
of 60 days, such as 8 days to 30 days.
[0030] Storage of the roll according to the present invention can
occur at a relative humidity rF in the range of 40% rF to 100% rF,
such as 50% rF to 95% rF, 60% rF, or 90% rF. The stored glass rolls
can be stored in an enclosed room at temperatures in a range
between 10.degree. C. and 30.degree. C., such as 15.degree. C. to
25.degree. C. or 18.degree. C. to 23.degree. C.
[0031] As described previously, the long-term bendable glass
material can be not only thin glass, but also a thin glass
laminate, such a polymer coated thin glass film is described, for
example, in WO 00/66507, the disclosure content of which is
incorporated into the current application by reference. In the case
of the thin glass laminate according to WO 00/66507, a polymer
layer consisting of a silicone polymer, a sol-gel polymer, a
polycarbonate, a polyethersulfone, a polyacrylate, a polyimide, a
cycloolefin-copolymer, a polyarylate or a silicone resin is applied
to a thin glass film consisting of aluminosilicate glass,
alumino-borosilicate glass or borosilicate glass, such as a
non-alkaline borosilicate glass.
[0032] Example glass materials that are suitable for the production
of glass ribbons having a thickness of less than 500 .mu.m are
glasses having the following composition in weight-%:
SiO.sub.2: 40-75;
[0033] Al.sub.2O.sub.3 1-25; B.sub.2O.sub.3: 0-16; alkaline earth
oxide: 1-30; and alkali oxide: 0-20, such as 0-2.
[0034] Generally, all glass compositions are suitable from the
aforementioned composition ranges. Exemplary glasses can have a low
content of alkali oxides, i.e., an alkali content in a range of 0-2
weight-%, such as glasses AF32, AF37 and AF45 by Schott AG.,
Mainz.
[0035] In one exemplary embodiment, the thin glass is a lithium
aluminosilicate glass having the following composition (in
weight-%):
TABLE-US-00001 Composition (Weight-%) SiO.sub.2 55-69
Al.sub.2O.sub.3 18-25 Li.sub.2O 3-5 Na.sub.2O + K.sub.2O 0-30 MgO +
CaO + SrO + BaO 0-5 ZnO 0-4 TiO.sub.2 0-5 ZrO.sub.2 0-5 TiO.sub.2 +
ZrO.sub.2 + SnO.sub.2 2-6 P.sub.2O.sub.5 0-8 F 0-1 B.sub.2O.sub.3
0-2
[0036] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0037] Another exemplary lithium aluminosilicate glass of the
present invention can consist of the following composition (in
weight-%):
TABLE-US-00002 Composition (Weight-%) SiO.sub.2 57-66
Al.sub.2O.sub.3 18-23 Li.sub.2O 3-5 Na.sub.2O + K.sub.2O 3-25 MgO +
CaO + SrO + BaO 1-4 ZnO 0-4 TiO.sub.2 0-4 ZrO.sub.2 0-5 TiO.sub.2 +
ZrO.sub.2 + SnO.sub.2 2-6 P.sub.2O.sub.5 0-7 F 0-1 B.sub.2O.sub.3
0-2
[0038] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0039] Another exemplary lithium aluminosilicate glass of the
present invention can consist of the following composition (in
weight-%):
TABLE-US-00003 Composition (Weight-%) SiO.sub.2 57-63
Al.sub.2O.sub.3 18-22 Li.sub.2O 3.5-5 Na.sub.2O + K.sub.2O 5-20 MgO
+ CaO + SrO + BaO 0-5 ZnO 0-3 TiO.sub.2 0-3 ZrO.sub.2 0-5 TiO.sub.2
+ ZrO.sub.2 + SnO.sub.2 2-5 P.sub.2O.sub.5 0-5 F 0-1 B.sub.2O.sub.3
0-2
[0040] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0041] In one exemplary embodiment, the thin glass is a soda-lime
glass having the following composition and contains (in
weight-%):
TABLE-US-00004 Composition (Weight-%) SiO.sub.2 40-81
Al.sub.2O.sub.3 0-6 B.sub.2O.sub.3 0-5 Li.sub.2O + Na.sub.2O +
K.sub.2O 5-30 MgO + CaO + SrO + BaO + ZnO 5-30 TiO.sub.2 +
ZrO.sub.2 0-7 P.sub.2O.sub.5 0-2
[0042] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0043] Another exemplary soda-lime glass of the present invention
can consist of the following composition (in weight-%):
TABLE-US-00005 Composition (Weight-%) SiO.sub.2 50-81
Al.sub.2O.sub.3 0-5 B.sub.2O.sub.3 0-5 Li.sub.2O + Na.sub.2O +
K.sub.2O 5-28 MgO + CaO + SrO + BaO + ZnO 5-25 TiO.sub.2 +
ZrO.sub.2 0-6 P.sub.2O.sub.5 0-2
[0044] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0045] Another exemplary soda-lime glass of the present invention
can consist of the following composition (in weight-%):
TABLE-US-00006 Composition (Weight-%) SiO.sub.2 55-76
Al.sub.2O.sub.3 0-5 B.sub.2O.sub.3 0-5 Li.sub.2O + Na.sub.2O +
K.sub.2O 5-25 MgO + CaO + SrO + BaO + ZnO 5-20 TiO.sub.2 +
ZrO.sub.2 0-5 P.sub.2O.sub.5 0-2
[0046] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0047] In one exemplary embodiment, the thin glass is a
borosilicate glass having the following composition (in
weight-%):
TABLE-US-00007 Composition (Weight-%) SiO.sub.2 60-85
Al.sub.2O.sub.3 0-10 B.sub.2O.sub.3 5-20 Li.sub.2O + Na.sub.2O +
K.sub.2O 2-16 MgO + CaO + SrO + BaO + ZnO 0-15 TiO.sub.2 +
ZrO.sub.2 0-5 P.sub.2O.sub.5 0-2
[0048] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0049] Another exemplary borosilicate glass of the present
invention can consist of the following composition (in
weight-%):
TABLE-US-00008 Composition (Weight-%) SiO.sub.2 63-84
Al.sub.2O.sub.3 0-8 B.sub.2O.sub.3 5-18 Li.sub.2O + Na.sub.2O +
K.sub.2O 3-14 MgO + CaO + SrO + BaO + ZnO 0-12 TiO.sub.2 +
ZrO.sub.2 0-4 P.sub.2O.sub.5 0-2
[0050] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0051] Another exemplary borosilicate glass of the present
invention can consist of the following composition (in
weight-%):
TABLE-US-00009 Composition (Weight-%) SiO.sub.2 63-83
Al.sub.2O.sub.3 0-7 B.sub.2O.sub.3 5-18 Li.sub.2O + Na.sub.2O +
K.sub.2O 4-14 MgO + CaO + SrO + BaO + ZnO 0-10 TiO.sub.2 +
ZrO.sub.2 0-3 P.sub.2O.sub.5 0-2
[0052] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0053] In one exemplary embodiment, the thin glass is an alkali
metal aluminosilicate glass consisting of the following composition
(in weight-%):
TABLE-US-00010 Composition (Weight-%) SiO.sub.2 40-75
Al.sub.2O.sub.3 10-30 B.sub.2O.sub.3 0-20 Li.sub.2O + Na.sub.2O +
K.sub.2O 4-30 MgO + CaO + SrO + BaO + ZnO 0-15 TiO.sub.2 +
ZrO.sub.2 0-15 P.sub.2O.sub.5 0-10
[0054] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0055] Another exemplary alkali metal aluminosilicate glass of the
present invention can consist of the following composition (in
weight-%):
TABLE-US-00011 Composition (Weight-%) SiO.sub.2 50-70
Al.sub.2O.sub.3 10-27 B.sub.2O.sub.3 0-18 Li.sub.2O + Na.sub.2O +
K.sub.2O 5-28 MgO + CaO + SrO + BaO + ZnO 0-13 TiO.sub.2 +
ZrO.sub.2 0-13 P.sub.2O.sub.5 0-9
[0056] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0057] Another exemplary alkali metal aluminosilicate glass of the
present invention can consist of the following composition (in
weight-%):
TABLE-US-00012 Composition (Weight-%) SiO.sub.2 55-68
Al.sub.2O.sub.3 10-27 B.sub.2O.sub.3 0-15 Li.sub.2O + Na.sub.2O +
K.sub.2O 4-27 MgO + CaO + SrO + BaO + ZnO 0-12 TiO.sub.2 +
ZrO.sub.2 0-10 P.sub.2O.sub.5 0-8
[0058] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0059] In one exemplary embodiment, the thin glass is an
aluminosilicate glass with low alkali content and consisting of the
following composition (in weight-%):
TABLE-US-00013 Composition (Weight-%) SiO.sub.2 50-75
Al.sub.2O.sub.3 7-25 B.sub.2O.sub.3 0-20 Li.sub.2O + Na.sub.2O +
K.sub.2O 0-4 MgO + CaO + SrO + BaO + ZnO 5-25 TiO.sub.2 + ZrO.sub.2
0-10 P.sub.2O.sub.5 0-5
[0060] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0061] Another exemplary aluminosilicate glass with low alkali
content of the present invention can consist of the following
composition (in weight-%):
TABLE-US-00014 Composition (Weight-%) SiO.sub.2 52-73
Al.sub.2O.sub.3 7-23 B.sub.2O.sub.3 0-18 Li.sub.2O + Na.sub.2O +
K.sub.2O 0-4 MgO + CaO + SrO + BaO + ZnO 5-23 TiO.sub.2 + ZrO.sub.2
0-10 P.sub.2O.sub.5 0-5
[0062] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0063] Another exemplary aluminosilicate glass with low alkali
content of the present invention can consist of the following
composition (in weight-%):
TABLE-US-00015 Composition (Weight-%) SiO.sub.2 53-71
Al.sub.2O.sub.3 7-22 B.sub.2O.sub.3 0-18 Li.sub.2O + Na.sub.2O +
K.sub.2O 0-4 MgO + CaO + SrO + BaO + ZnO 5-22 TiO.sub.2 + ZrO.sub.2
0-8 P.sub.2O.sub.5 0-5
[0064] Potentially, coloring oxides can be added, such as
Nd.sub.2O.sub.3, Fe.sub.2O.sub.3, CoO, NiO, V.sub.2O.sub.5,
MnO.sub.2, TiO.sub.2, CuO, CeO.sub.2, Cr.sub.2O.sub.3; 0-2 weight-%
As.sub.2O.sub.3, Sb.sub.2O.sub.3, SnO.sub.2, SO.sub.3, Cl, F and/or
CeO.sub.2 can be added as a refining agent; and 0-5 weight-% rare
earth oxides can also be added in order to introduce magnetic,
photon- or optical functions into the glass layer or plate. The
total volume of the total composition is 100 weight-%.
[0065] The glass material can be a thin glass or glass film having
a thickness of less than 500 .mu.m, such as less than 350 .mu.m and
a minimum thickness of 3 .mu.m. The thickness can be in the range
of 20 .mu.m to 200 .mu.m. Exemplary glass film thicknesses are 5,
10, 15, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210 or
280 .mu.m.
[0066] By rewinding the glass ribbons and changing the direction of
curvature after a quarter or half of the total storage period, the
stability can be further increased. The glass is hereby rewound in
a roll-to-roll process.
[0067] The bent glass, such as wound glass, is subjected to a
moderate tensile stress .sigma..sub.app that is less than the
following mathematical term:
1.15 Min ( .sigma. _ a - .DELTA. a 0.4 ( 1 - ln ( A ref A App .PHI.
) ) , .sigma. _ e - .DELTA. e 0.4 ( 1 - ln ( L ref L App .PHI. ) )
) ##EQU00001##
whereby .sigma..sub.a and .sigma..sub.e are average values of the
tensile stress on breakages of thin glass samples that are
subjected to bending stresses, whereby L.sub.ref describes the edge
length and A.sub.ref describes the surface of the samples, whereby
.sigma..sub.a is the average value of the tensile stress in the
surface of the sample during breaking, and .sigma..sub.e is the
average value of the tensile stress on a break originating from the
edge of the sample, and whereby .DELTA..sub.e and .DELTA..sub.a are
the standard deviations of the average values .sigma..sub.e or
respectively .sigma..sub.a, and whereby A.sub.app is the surface of
the thin glass and L.sub.app the added edge lengths of opposite
edges of the thin glass material and .PHI. a predetermined maximum
breakage quota within a time period of at least half a year.
[0068] The bent glasses, which can be glasses that are wound into
rolls, such as thin glasses having a thickness of less than 500
.mu.m, such as less than 350 .mu.m. The minimum thickness can be 3
.mu.m. An exemplary thickness range is between 20 .mu.m and 200
.mu.m. Exemplary glass film thicknesses are 5, 10, 15, 25, 30, 35,
50, 55, 70, 80, 100, 130, 145, 160, 190, 210 or 280 .mu.m.
[0069] The information in regard to the maximum tensile stress for
the bent glasses, such as glass rolls, is based on the recognition
that breaks along the edges and in the surface of the glass trace
back to various defects in the glass, and that the probabilities of
breakage are statistically independent of each other. Thus, glass
strengths in regard to break resistance along the edges and in the
surface are considered independent of each other.
[0070] The actual break resistance is calculated according to the
above mathematical term through the minimum of the tensile stresses
on breaks in the surface and along the edges. In this way, the
typically different life spans of the thin glasses are also
considered in regard to breaks along the edges and on surfaces that
occur during bending. When specifying a life span, the maximum
probability of breakage .PHI. can be 0.1 or less (in other words
10% max.), such as less than 0.05 (less than 5%) or less than 0.03
(less than 3%) when storing long-term in a rolled state, or in a
bent state, or during utilization in bent state.
[0071] A low probability of breaking in specified storage
conditions is noted with mostly alkali-free borosilicate glasses.
Such exemplary borosilicate glasses have a composition including
the following components in weight-% on oxide basis:
SiO.sub.2: 40-75;
[0072] Al.sub.2O.sub.3: 1-25; B.sub.2O.sub.3: 0-16; alkaline earth
oxide: 1-30; and alkali oxide: 0-1.
[0073] Other exemplary glasses have a composition including the
following components in weight-% on oxide basis:
SiO.sub.2: 45-70;
[0074] Al.sub.2O.sub.3: 5-25; B.sub.2O.sub.3: 1-16; alkaline earth
oxide: 1-30; and alkali oxide: 0-1.
[0075] In addition to the bendable long-term storable and usable
glass materials, the present invention also provides a method for
the production of a long-term bendable glass material, which can be
in the form of a glass material that is wound onto a roll, such as
a glass ribbon having a thickness of less than 500 .mu.m, such as
less than 350 .mu.m, and a minimum thickness of 3 .mu.m, such as in
the range of 20 .mu.m to 200 .mu.m. The method includes the
following steps: the glass material is initially bent in a bending
radius R in the range of 1 mm to 10.sup.7 mm, such as 5 mm to
10.sup.6 mm or 10 to 10.sup.3 mm. The bent glass material is stored
for a time period of at least 1 day, such as at least 3 days, at
least 5 days, at least 7 days, at least 10 days, at least 50 days,
at least 150 days, or at least 300 days; after storage over a time
period of at least 1 day, such as at least 3 days, to at most 500
days, such as at least 50 days to at most 300 days, the bent glass
material is inspected for cracks, breaks, tears, fracture points,
and defects, and the bent glass material or a cut-off of the bent
glass material is classified as reject with a defect marking if
damage such as cracks, breaks, tears, fracture points, and defects
has been detected, or the bent glass material is classified as a
long-term bendable glass material if damage has not been
detected.
[0076] In order to increase the stability of the glass ribbons,
provision can be made to rewind the glass roll one time or several
times. This can occur in a roll-to-roll process.
[0077] "Reject" is also to be understood that damaged sections such
as those with cracks, breaks, tears, fracture points, and defects
are marked and are rejected or removed in a later step.
[0078] The marking can occur on the glass ribbon with the
assistance of a defect marking that is placed, for example, on a
defect point F.sub.i at a location (x.sub.i, y.sub.i) on the glass
ribbon.
[0079] The placement of defect markings has made it possible that
entire sections of the glass ribbons no longer have to be removed
as rejects. Rather, the placement of a defect marking F.sub.i has
enabled processors of a glass roll to identify the section of the
glass ribbon with the defect and thus to not utilize it in the
manufacture of products which--due to the defect--cannot be
produced according to specification. For example, the defect
markings can be read and considered during processing of the glass
roll or the glass ribbon when unwinding the glass roll, such as
when unraveling the endless ribbon. Accordingly, a further damage
inspection can be foregone during further processing. In addition,
reject rates can be reduced. Waste due to contaminations of the
glass ribbon that are erroneously classified as defect points can
be avoided since the defect inspection occurs earlier, such as
immediately following drawing of the glass ribbon from the melt and
prior to winding or laminating of the glass ribbon. If the layers
of the glass ribbon are separated by removable separation layers
that are connected with the glass ribbon, the defect marking can
also be placed on the separation layer. If the glass ribbon also
comprises a metal layer or plastic layer that is connected with the
glass layer, the defect marking may also be placed on the metal
layer or plastic layer. The previously described classified or
categorized glass materials are characterized by a long-term
bendability whereby practically no damage occurs during the storage
period or utilization in bent state, in other words under tensile
stress on one glass material side.
[0080] In the bent condition, long-term bendable glass materials
can have bending radii R in the range of 1 mm to 10.sup.7 mm, such
as 5 mm to 10.sup.6 mm or 10 to 10.sup.3 mm.
[0081] The glass material can have a thickness of less than 500
.mu.m, such as less than 350 .mu.m, and a minimum thickness of 3
.mu.m, such as within the range of 20 .mu.m to 200 .mu.m. Exemplary
glass thicknesses are 5, 10, 15, 25, 30, 35, 50, 55, 70, 80, 100,
130, 145, 160, 190, 210 or 280 .mu.m. If a long-term bendable glass
material is wound onto a roll, the core diameter of the roll can be
greater than 75 mm, such as greater than 100 mm, greater than 150
mm, greater than 300 mm, greater than 400 mm, greater than 500 mm,
or greater than 600 mm.
[0082] Storage of the roll according to the present invention can
occur at a relative humidity rF in the range of 40% rF to 100% rF,
such as 50% rF to 95% rF or between 60% rF and 90% rF. The roll can
be subjected to a temperature between 10.degree. C. and 30.degree.
C., such as between 15.degree. C. and 25.degree. C. or in between
18.degree. C. and 23.degree. C. and to standard atmospheric
conditions. Storage in a humid environment, as opposed to dry
storage, allows for healing of the cracks to possibly occur.
Generally, it would be expected that the glasses that are stored
infinitely would break. However, this is countered by a healing of
the cracks due to aging of the glass. Storage in a humid
environment is conducive to healing of cracks, since healing of
cracks is achieved by a rapid filleting of the cracks. Generally,
it has turned out that the more humid the storage, the more rapid
the filleting of the cracks. Filleting of cracks ensures that no
more cracks originate and that the cracks can no longer spread. In
addition, the strength of the glass or glass ribbon is
increased.
[0083] The effect of the aging of the glass is at 0-40%, such as 5%
or 5-20% of the strength increase over time.
[0084] In the process of producing a glass with low probability of
breaking, rewinding of the glass material or a conversion into
sheets from the stored roll and/or inspection of the roll for
breaks in the glass occurs after storage, whereby screening occurs
of wound glass or respectively wound roll, with detection of
defects.
[0085] The glass material can be a thin glass or a glass film
having a thickness of less than 500 .mu.m, such as less than 350
.mu.m. The minimum thickness can be 3 .mu.m. An exemplary thickness
range is between 20 .mu.m and 200 .mu.m. Exemplary glass film
thicknesses are 5, 10, 15, 25, 30, 35, 50, 55, 70, 80, 100, 130,
145, 160, 190, 210 or 280 .mu.m.
[0086] Regarding the different glass materials, exemplary glass
materials are previously described herein. Exemplary glasses can
have a low content of alkali oxides, i.e., have an alkali content
in a range of 0-2 weight-%, such as glasses AF32, AF37 and AF45 by
Schott AG., Mainz.
[0087] The present invention moreover provides the use of a glass
material--that, according to the present invention, is classified
as long-term bendable glass material--as a bent glass substrate,
such as one having a bending radius of 1 to 10.sup.7 mm, such as 5
to 10.sup.6 mm or 10 to 10.sup.3 mm. The long-term bendable glass
materials are initially wound onto a glass roll and are stored for
an extended period of time. Subsequently, glass segments are
unwound from the roll and are subjected to a permanent tensile
stress. This causes bending of the glass to a curved glass
substrate having the previously cited bending radii. The curved
glass substrate may be used, for example, in a curved display as a
cover glass or as glass on a touch panel. Rewinding is also
possible.
[0088] The present invention also provides a proof-test or test
method for characterization of a long-term bendable glass material.
The proof-test includes storage of a glass material, which can be
in the form of a wound glass material, such as a glass ribbon
having a thickness of less than 500 .mu.m or less than 350 .mu.m
and a minimum thickness of 3 .mu.m or within the range of 20 .mu.m
to 200 .mu.m for a storage period of at least 1 day, such as at
least 3 days, at least 5 days, at least 7 days, at least 10 days,
at least 50 days, at least 150 days, or at least 300 days. After
the storage time, a crack depth in the glass ribbon is determined
and compared with a predefined crack depth. If the crack depth is
less than the predefined crack depth, then the glass material is
determined to be a long-term bendable glass material, so that the
probability of breaking 0 is less than 0.05, such as less than
0.01, for a maximum storage period of half a year, such as one
year, 2 years and a maximum of 5 years.
BRIEF DESCRIPTION OF THE DRAWINGS
[0089] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0090] FIG. 1 is a progression of a break development for a 50
.mu.m thick thin glass film of glass AF32;
[0091] FIG. 2 is break progression for a 100 .mu.m thick thin glass
film of glass AF32;
[0092] FIG. 3 is a Weibull-diagram of strength (breaking stress)
over the probability of failure of a reference glass sample;
[0093] FIG. 4 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
30 mm;
[0094] FIG. 5 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
25 mm;
[0095] FIG. 6 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
22.5 mm;
[0096] FIG. 7 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
20 mm;
[0097] FIG. 8 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
17 mm;
[0098] FIG. 9 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
15 mm; and
[0099] FIG. 10 is a Weibull-diagram of strength (breaking stress)
over the probability of failure for a glass sample with a radius of
14 mm.
[0100] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0101] Referring now to the drawings, and more particularly to
FIGS. 1 and 2, the probability of breakage is given over time for a
multitude of glass rolls having a diameter of 85 mm, including a
glass roll having a thickness of 50 .mu.m. Intermediate layers
consisting of a physically crosslinked, closed-cell
polyolefin-foam, as offered under the trade name Alveolit by
SEKISUI ALVEO BS GmbH/D-Bad Sobernheim is inserted between the
individual glass layers. The glass rolls are enclosed in plastic
covers and are stored at room temperature. The moisture was hereby
variable between 20% and 85%. Overall, several observations were
conducted. The total observation period was 300 days. The
development of a break in a 50 .mu.m thick thin glass film of AF32
is illustrated in FIG. 1. As can be seen, the probability of
breaking strongly increases initially and remains then on a largely
constant level. At best, a small increase can be detected after a
certain storage time.
[0102] Rolls of thin glass ribbons with a thickness of 50 .mu.m
consisting of an alkali-free alumino-borosilicate glass were
inspected as glass material. This glass AF32 by Schott AG., Mainz
is a glass consisting of the following components in weight-%:
SiO.sub.2: 61.4;
[0103] Al.sub.2O.sub.3: 17.5; B.sub.2O.sub.3: 10.5; alkaline earth
oxide: 10.3; and alkali oxide: 0.
[0104] As can be seen in FIG. 1, the number of breaks strongly
increases at the beginning to 4 breaks/km length of film and
increases only slowly with extended storage times. After 4 weeks or
30 days, a virtually stationary state is reached and no significant
increase in the number of breaks is detected. The probability of
breaks after 30 days is less than 0.03, such as less than 0.01.
Over several months of storage period, the glass film shows no
significant increase in the number of breaks
[0105] The following applies to the tension .sigma. in the glass
roll:
.sigma. = E t 2 R ##EQU00002##
E=the Young's (elastic) modulus which, in the case of AF32 is 74
GPa; t=the glass thickness which, in the case of AF32 is 50 .mu.m;
and the core diameter R of the roll=85 mm.
[0106] For the tension .sigma. for the roll consisting of a 50
.mu.m thick AF32 glass film this suggests a value of approximately
21 MPa for the tension in the glass roll; for a 100 .mu.m thick
glass film a tension of 45 MPa.
[0107] FIG. 2 illustrates the results for a 100 .mu.m thick AF32
glass film. As can be seen from FIG. 2, the number of breaks also
increases rapidly in this case within 25 days. In contrast to the
50 .mu.m thick glass film, the level from which the number of
breaks remains largely constant is reached only after more than 100
days. As in the case with the 50 .mu.m thick glass film, the
probability of breaking when stored longer than 150 days is 0.01,
in other words 1% lower. For the tension in the glass roll, a value
of .sigma.=45 MPa is determined.
[0108] The glass rolls that are stored over at least 1 day, such as
at least 5 days, at least 7 days, at least 10 days, at least 50
days, at least 150 days, or at least 300 days with low probability
of breaking are categorized as remaining stable over a long-term
storage period, or long-term bendable, or usable in a curved state.
Such glasses find use in curved indicator devices, such as curved
cover glasses or display glasses.
[0109] Surprisingly, after conducting the proof-test, i.e.,
classifying the glass material as long-term bendable, an increase
in strength was achieved due to filleting of the crack tips.
[0110] With glass that is subjected to the proof-test, subcritical
crack formation occurs due to tensile stress. This means that all
cracks that reach the critical crack length, i.e., the
predetermined crack length during a given time period, will result
in a break. Storage in accordance with the proof-test is therefore
a test during which glasses with micro-cracks that are not shorter
than the critical crack length--that is the target value--are
rejected. Cracks that do not lead to a break within the first short
time period, will also not lead to a break after a long time
period.
[0111] This makes it possible to put a greater load onto the glass
roll after conducting the proof-test. It has been shown that loads
can be greater of up to 20% than in the proof-test. The range of
the possible load increase is therefore 0 to 20%. Values of 5%,
10%, 15% load increase are possible. As is the case in the
proof-test, the load is adjusted through the winding radius. The
following applies for the tensile stress:
.sigma. = E t 2 R ##EQU00003##
whereby: t: is the thickness of the glass material; R: is the
winding radius; and E: is the Young's modulus.
[0112] FIGS. 3-10 demonstrate the surprising fact that the glass
becomes stronger during storage.
[0113] FIG. 3 illustrates the Weibull diagram as strengths of a
reference sample.
[0114] FIGS. 4-10 illustrate the Weibull diagrams of glasses that
were stored longer, after conducting the proof-test and under
greater loads than during the proof-test as a comparison to a
reference sample from FIG. 3. In FIG. 4, the inspected sample had a
radius of 30 mm; in FIG. 5, the inspected sample had a radius of 25
mm; in FIG. 6, the inspected sample had a radius of 22.5 mm; in
FIG. 7, the inspected sample had a radius of 20 mm; in FIG. 8, the
inspected sample had a radius of 17 mm; in FIG. 9, the inspected
sample had a radius of 15 mm; and in FIG. 10, the inspected sample
had a radius of 14 mm. The glasses are maintained over a longer
time period under strong tension after the proof-test was
conducted.
[0115] Surprisingly, it can be appreciated from FIGS. 4-10 that the
samples with high strengths become clearly worse, but the samples
whose original strength is not much above the load limit are
clearly better. However, if the stresses become too great, the
effect is no longer easily recognizable.
[0116] With the present invention, it has been recognized for the
first time how one can proceed in order to facilitate a long-term
bendability for glass on a roll or in a curved application.
Moreover, a proof-test is provided with which it is possible to
classify long-term bendable glass samples.
[0117] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *