U.S. patent application number 17/708471 was filed with the patent office on 2022-07-14 for stiff interlayers for laminated glass structures.
The applicant listed for this patent is CORNING INCORPORATED. Invention is credited to William Keith Fisher, Mark Stephen Friske, Anurag Jain.
Application Number | 20220219431 17/708471 |
Document ID | / |
Family ID | 1000006239045 |
Filed Date | 2022-07-14 |
United States Patent
Application |
20220219431 |
Kind Code |
A1 |
Fisher; William Keith ; et
al. |
July 14, 2022 |
STIFF INTERLAYERS FOR LAMINATED GLASS STRUCTURES
Abstract
A new laminated glass structure for automotive glazing,
architectural window and other applications that includes two
sheets of relatively thin, optionally chemically strengthened
glass, such as Corning.RTM. Gorilla.RTM. Glass, with a composite
interlayer structure that includes at least one relatively stiff
layer having relatively high Young's modulus of 50 MPa or higher
and a relatively softer polymer layer having a relatively low
Young's modulus of 20 MPa or lower.
Inventors: |
Fisher; William Keith;
(Corning, NY) ; Friske; Mark Stephen; (Campbell,
NY) ; Jain; Anurag; (Painted Post, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING INCORPORATED |
CORNING |
NY |
US |
|
|
Family ID: |
1000006239045 |
Appl. No.: |
17/708471 |
Filed: |
March 30, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16788363 |
Feb 12, 2020 |
11305517 |
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17708471 |
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14402624 |
Nov 20, 2014 |
10596783 |
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PCT/US2013/043512 |
May 31, 2013 |
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16788363 |
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61653865 |
May 31, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 428/24983 20150115;
B32B 17/10761 20130101; B32B 2307/56 20130101; B32B 17/10779
20130101; B32B 17/10137 20130101; B32B 2307/51 20130101; B32B
2419/00 20130101; B32B 2307/40 20130101; B32B 2451/00 20130101;
B32B 17/10743 20130101; Y10T 428/2495 20150115; B32B 2307/102
20130101; B32B 2605/00 20130101; B32B 7/022 20190101; B32B 17/10752
20130101; B32B 2250/05 20130101; Y10T 428/24967 20150115; B32B
17/10788 20130101; B32B 17/10036 20130101 |
International
Class: |
B32B 17/10 20060101
B32B017/10; B32B 7/022 20060101 B32B007/022 |
Claims
1. A glass laminate comprising: a first chemically strengthened
alkali aluminosilicate glass sheet having a thickness of 1.5 mm or
less; a second glass sheet; and a composite interlayer positioned
between the first and second glass sheets, the composite interlayer
comprising: two relatively stiff polymer layers having a Young's
modulus of 50 MPa or greater, and selected from the group
consisting of polyvinyl butyral (PVB), polycarbonate (PC), or
polyethylene terephthalate (PET), and a relatively soft polymer
layer having a Young's modulus of less than 20 MPa, and selected
from the group consisting of polyvinyl butyral (PVB), acoustic
polyvinyl butyral (A-PVB), ethylene vinyl acetate (EVA),
plasticized polyvinyl chloride (PVC), or thermoplastic polyurethane
(TPU), wherein the relatively soft polymer layer is disposed
between the two relatively stiff polymer layers.
2. The glass laminate of claim 1, wherein the two relatively stiff
polymer layers have a Young's modulus of 100 MPa or greater.
3. The glass laminate of claim 1, wherein the two relatively stiff
polymer layers have a Young's modulus ranging from 100 MPa to 1000
MPa.
4. The glass laminate of claim 1, wherein the relatively soft
polymer layer has a Young's modulus of 10 MPa or less.
5. The glass laminate of claim 1, wherein the relatively soft
polymer layer has a Young's modulus ranging from 1 MPa to 10
MPa.
6. The glass laminate of claim 1, wherein the two relatively stiff
polymer layers have a Young's modulus 10-100 times greater than the
Young's modulus of the relatively soft polymer layer.
7. The glass laminate of claim 1, wherein the composite interlayer
makes up a majority of a total thickness of the glass laminate.
8. The glass laminate of claim 7, wherein the composite interlayer
makes up at least 57% of the total thickness of the glass
laminate.
9. The glass laminate of claim 7, wherein at least one of the first
or second glass sheets has a thickness ranging from 0.5 mm to 1.5
mm.
10. The glass laminate of claim 1 comprising a total thickness of
from about 2 mm to about 4 mm.
11. The glass laminate of claim 1, wherein the second glass sheet
is chemically strengthened.
12. The glass laminate of claim 1, wherein the second glass sheet
is non-chemically-strengthened.
13. The glass laminate of claim 1, wherein the first chemically
strengthened alkali aluminosilicate glass sheet comprises from 8
mol% to about 18 mol% Na.sub.2O.
14. The glass laminate of claim 1, wherein the first chemically
strengthened alkali aluminosilicate glass sheet comprises from 9
mol% to about 21 mol% Na.sub.2O.
15. The glass laminate of claim 1, wherein the first chemically
strengthened alkali aluminosilicate glass sheet is an alkali
aluminoborosilicate glass.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/788,363 filed on Feb. 12, 2020, which is a
continuation of U.S. patent application Ser. No. 14/402,624 filed
on Nov. 20, 2014, and granted as U.S. Pat. No. 10,596,783 on Mar.
24, 2020, which is a national stage application under 35 U.S.C.
.sctn. 371 of International Application No. PCT/US13/43512 filed
May 31, 2013 which claims the benefit of priority to U.S.
Provisional Application No. 61/653,865 filed on May 31, 2012, the
content of each of which is relied upon and incorporated herein by
reference in its entirety.
FIELD
[0002] The disclosure relates generally to relatively stiff
interlayer materials for laminated thin glass structures and
acoustic dampening thin glass laminate structures including such
relatively stiff interlayer, which structures may be used in
automotive glazing and other vehicle and architectural
applications.
BACKGROUND
[0003] Glass laminates can be used as windows and glazing in
architectural and vehicle or transportation applications, including
automobiles, rolling stock, locomotive and airplanes. Glass
laminates can also be used as glass panels in balustrades and
stairs, and as decorative panels or covering for walls, columns,
elevator cabs, kitchen appliances and other applications. As used
herein, a glazing or a laminated glass structure is a transparent,
semi-transparent, translucent or opaque part of a window, panel,
wall, enclosure, sign or other structure. Common types of that
glazing that are used in architectural and vehicle applications
include clear and tinted laminated glass structures.
[0004] Conventional automotive glazing constructions may consist of
two plies of 2 mm soda lime glass (heat treated or annealed) with a
polyvinyl butyral PVB interlayer. These laminate constructions have
certain advantages, including, low cost, and a sufficient impact
resistance for automotive and other applications. However, because
of their limited impact resistance, these laminates usually have a
poor behavior and a higher probability of breakage when getting
struck by roadside stones, vandals and other impacts.
[0005] In many vehicle applications, fuel economy is a function of
vehicle weight. It is desirable, therefore, to reduce the weight of
glazings for such applications without compromising their strength
and sound-attenuating properties. In view of the foregoing,
thinner, economical glazings or glass laminates that possess or
exceed the durability, sound-damping and breakage performance
properties associated with thicker, heavier glazings are
desirable.
[0006] No admission is made that any reference cited herein
constitutes prior art. Applicant expressly reserves the right to
challenge the accuracy and pertinence of any cited documents.
SUMMARY
[0007] The present disclosure describes a new thin laminated glass
structure for automotive glazing, architectural window and other
applications. The new structure described herein includes two
sheets of relatively thin chemically strengthened glass, such as
Corning.RTM. Gorilla.RTM. Glass with composite interlayers that
include a relatively stiff, relatively high modulus polymer layer
and a relatively softer, lower modulus polymer layer. Such an
interlayer can impart both desirable acoustic damping properties
and rigidity, characterized by a sufficient degree of resistance to
deflection or deformation to meet automotive and architectural
specifications and standardized tests.
[0008] Thin glass laminate mechanical properties depend on the
properties of the interlayer to a greater degree than existing
relatively thick soda lime glass laminates, because the interlayer
comprises a much greater fraction of total laminate thickness for
thin glass laminates than existing soda lime glass laminates.
Properly engineered interlayers play a significant role in
determining mechanical properties of thin glass laminates, such as
its acoustic, optical, and rigidity properties. Acoustic damping of
a laminated thin glass structure is primarily determined by shear
modulus and loss factor of the polymer interlayer. When the
interlayer is a large fraction of the total glass laminate
thickness, then the bending rigidity (load deformation properties)
of the laminated thin glass structure will be largely determined by
the Young's modulus of the interlayer. Using multilayer
interlayers, these properties can be adjusted independently in each
layer in order to create a laminate having satisfactory rigidity
and acoustic damping properties.
[0009] One embodiment of the disclosure relates to a thin glass
laminate structure having two glass sheets having a thickness of
less than 1.5 mm; a composite interlayer between the two glass
sheets comprising at least one relatively stiff polymer layer
having a Young's modulus of 50 MPa or greater and a relatively soft
polymer layer having a Young's modulus of less than 20 MPa.
[0010] An additional embodiment of the disclosure relates to such a
thin glass laminate structure having two of the relatively stiff
polymer layers and the relatively soft polymer layer is located
between the two relatively stiff polymer layers.
[0011] According to some embodiments of the present disclosure, the
relatively stiff polymer layers have a Young's modulus of about 100
MPa or greater, or in a range from about 100 MPa to about 1000 MPa.
The relatively soft polymer layer has a Young's modulus of in a
range from about 1 MPa to 10 MPa, or about 10 MPa or less, or in a
range from about 1 MPa to 10 MPa.
[0012] In other embodiments hereof, the relatively stiff polymer
layer has a Young's modulus that is about 10.times. the Young's
modulus of the relatively soft polymer layer, or about 100.times.
the Young's modulus of the relatively soft polymer layer.
[0013] In other embodiments hereof, the composite interlayer may
makes up a majority of the total glass laminate thickness. The
composite interlayer may make up about 57% of the total glass
laminate thickness.
[0014] The thin glass laminate structure as in claim 1, wherein the
polymer layers are formed of a thermoplastic polymer selected from
the group consisting of PVBm, ionomer, PET, SentryGlas.RTM. from
DuPont, EVA, and TPU.
[0015] In other embodiments hereof, the thin glass sheets each have
a thickness in a range from about 0.5 mm to about 1.5 mm. The glass
sheets may additionally be chemically strengthened.
[0016] Additional features and advantages will be set forth in the
detailed description which follows, and in part will be readily
apparent to those skilled in the art from the description or
recognized by practicing the embodiments as described in the
written description and claims hereof, as well as the appended
drawings.
[0017] It is to be understood that both the foregoing general
description and the following detailed description are merely
exemplary, and are intended to provide an overview or framework to
understand the nature and character of the claims.
[0018] The accompanying drawings are included to provide a further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate one or more
embodiment(s), and together with the description serve to explain
principles and operation of the various embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a partial cross-sectional illustration of stiff
interlayer structure according an embodiment of the present
description;
[0020] FIG. 2 is a partial cross-sectional illustration of a
laminated glass structure including a relatively stiff interlayer
structure as illustrate in FIG. 1;
[0021] FIG. 3 is a plot of the results of modeling studies
comparing the load/deformation properties of laminated glass
structures that include two sheets of 0.7 mm thick Coming Gorilla
Glass interlayers formed of standard PVB, standard acoustic
tri-layer PVB and a tri-layer PVB with stiff outer layers according
to the present description; and
[0022] FIG. 4 is a depth of layer versus compressive stress plot
for various glass sheets according to embodiments hereof.
DETAILED DESCRIPTION
[0023] FIG. 1 is a partial cross-sectional schematic illustration
of a polymer or composite interlayer structure (or simply an
interlayer) 10 according to an embodiment hereof. The interlayer
structure 10 may include two relatively stiff outer layers 12 and
14 laminated one either side of a central relatively soft central
layer 16. However, embodiments hereof include an interlayer 10
having a single relatively stiff layer 12 and a relatively soft
layer 16. The relatively stiff outer layers 12 and 14 may be formed
of a relatively stiff polymer, such as an ionmer. For example, the
outer layers may be formed of SentryGlas.RTM. from DuPont,
polycarbonate, or a relatively stiff polyvinyl butyral (PVB). An
example of a relatively stiff PVB is Saflex DH from Solutia. By
relatively stiff as used in the present description and the
appended claims, it is meant that the outer layers have a Young's
modulus of about 20 MPa or greater, about 50 MPa or greater, about
100 MPa or greater, or within a range from about 50 MPa to about
1000 MPa or from about 100 MPa to about 1000 MPa. The relatively
soft central layer 16 may be formed of a relatively soft polymer
material. For example, the central layer maybe formed of a
relatively soft PVB, acoustic PVB, ethylene vinyl acetate (EVA),
thermoplastic polyurethane (TPU), or other suitable polymer or
thermoplastic material. By relatively soft as used in the present
description and the appended claims, it is meant that the central
layer 16 has a Young's modulus of about 20 MPa or less, about 10
MPa or less, or within a range from about 10 MPa to about 20 MPa,
or from about 1 MPa to 10 MPa. The layers of the interlayer
structure 10 described herein may be coextruded together to form a
single interlayer sheet with multiple layers, or they may be
separately formed and then laminated together in any manner as well
known and understood in the art. According to some embodiments
hereof, the relatively stiff outer layers 12, 14 may have a Young's
modulus that is about 10.times. to about 100.times. the Young's
modulus of the relatively soft central layer 16. In the case of
coextrusion, the outer 12, 14 and central 16 layers in the
composite interlayer need to be rheologically and chemically
compatible to enable coextrusion as a single sheet.
[0024] FIG. 2 is a partial cross-sectional schematic illustration
of a laminated glass structure 20 according to an embodiment hereof
that includes the composite interlayer of FIG. 1. The laminated
glass structure includes two thin glass sheets 22 and 24 laminated
on either side of an interlayer 10 formed of two outer relatively
stiff layers 12 and 14 laminated on either side of a central
relatively soft central layer 16. Thin as used in relation to the
glass sheets in the present disclosure and the appended claims
means glass sheets having a thickness not exceeding about 1.5 mm,
not exceeding about 1.0 mm, not exceeding about 0.7 mm, not
exceeding about 0.5 mm, or within a range from about 0.5 mm to
about 1.5 mm, or from about 0.5 mm to about 1.0 mm or from about
0.5 mm to about 0.7 mm. According to some embodiments hereof, the
composite interlayer 10 makes up a large fraction of the total
laminate thickness, such as a majority (>50%) of the total
thickness of the laminated glass structure 20. For example, for
standard automotive laminated glass structures the interlayer
structure may make up about 20% of the total glass laminate
thickness, whereas for thin glass laminate structures of the
present disclosure the interlayer structure may make up about 57%
or more of the total glass laminate thickness.
[0025] According to an embodiment hereof, the glass sheets may be
formed of thin glass sheets that have been chemically strengthened
using an ion exchange process, such as Corning Gorilla.RTM. glass.
As described in U.S. Pat. Nos. 7,666,511, 4,483,700 and 5,674,790,
Corning Gorilla glass is made by fusion drawing a glass sheet and
then chemical strengthening the glass sheet. As described in more
detail hereinafter, Corning Gorilla glass has a relatively deep
depth of layer (DOL) of compressive stress, and presents surfaces
having a relatively high flexural strength, scratch resistance and
impact resistance. The glass sheets 22 and 24 and the interlayer 10
may be bonded together during a lamination process in which the
glass sheet 22, interlayer 10 and glass sheet 24 are stacked one on
top of the other, pressed together and heated to a temperature of,
by way of example, 130.degree. C. or a temperature that is near or
slightly above the softening temperature of the outer layers 12 and
14, such that the outer layers 12 and 14 of the interlayer 10 are
adhered to the glass sheets.
[0026] FIG. 3 shows results of finite element modeling studies of
0.7 mm thick Corning Gorilla Glass laminated glass structures made
using standard 0.76 mm thick monolithic PVB (0.76 SPVB) (line A),
standard acoustic tri-layer PVB (0.33 SPVB/0.15 APVB/0.33 SPVB)
(line B) and a tri-layer PVB with stiffened outer layers (0.33
SG+/0.15 APVB/0.33 SG+) (line C). The physical properties of the
outer layers for the stiffened interlayer were adjusted to those of
SentryGlas.RTM. from DuPont. The benefit of stiffening the outer
layers results in a more rigid laminate as indicated having reduced
deformation upon loading.
[0027] Suitable glass sheets may be chemically strengthened by an
ion exchange process. In such an ion exchange process, the sheet of
glass are typically immersed in a molten salt bath for a
predetermined period of time. Ions within the glass sheet at or
near the surface of the glass sheet are exchanged for larger metal
ions, for example, from the salt bath. In one embodiment, the
temperature of the molten salt bath is about 430.degree. C. and the
predetermined time period is about eight hours. The incorporation
of the larger ions into the glass strengthens the glass sheet by
creating a compressive stress in a near surface region of the glass
sheet. A corresponding tensile stress is induced within a central
region of the glass sheet to balance the compressive stress.
[0028] Example ion-exchangeable glasses that are suitable for
forming glass laminates are alkali aluminosilicate glasses or
alkali aluminoborosilicate glasses, though other glass compositions
are contemplated. As used herein, "ion exchangeable" means that a
glass is capable of exchanging cations located at or near the
surface of the glass with cations of the same valence that are
either larger or smaller in size. One example glass composition
comprises SiO.sub.2, B.sub.2O.sub.3 and Na.sub.2O, where
(SiO.sub.2+B.sub.2O.sub.3).gtoreq.66 mol. %, and Na.sub.2O.gtoreq.9
mol. %. In an embodiment, the glass sheets include at least 6 wt. %
aluminum oxide. In a further embodiment, a glass sheet includes one
or more alkaline earth oxides, such that a content of alkaline
earth oxides is at least 5 wt. %. Suitable glass compositions, in
some embodiments, further comprise at least one of K.sub.2O, MgO,
and CaO. In a particular embodiment, the glass can comprise 61-75
mol. % SiO.sub.2; 7-15 mol. % Al.sub.2O.sub.3; 0-12 mol. %
B.sub.2O.sub.3; 9-21 mol. % Na.sub.2O; 0-4 mol. % K.sub.2O; 0-7
mol. % MgO; and 0-3 mol. % CaO.
[0029] A further example glass composition suitable for forming
glass laminates as described herein comprises: 60-70 mol. %
SiO.sub.2; 6-14 mol. % Al.sub.2O.sub.3; 0-15 mol. % B.sub.2O.sub.3;
0-15 mol. % Li.sub.2O; 0-20 mol. % Na.sub.2O; 0-10 mol. % K.sub.2O;
0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO.sub.2; 0-1 mol. %
SnO.sub.2; 0-1 mol. % CeO.sub.2; less than 50 ppm As.sub.2O.sub.3;
and less than 50 ppm Sb.sub.2O.sub.3; where 12 mol. %
(Li.sub.2O+Na.sub.2O+K.sub.2O).ltoreq.20 mol. % and 0 mol.
%.ltoreq.(MgO+CaO).ltoreq.10 mol. %.
[0030] A still further example glass composition comprises:
63.5-66.5 mol. % SiO.sub.2; 8-12 mol. % Al.sub.2O.sub.3; 0-3 mol. %
B.sub.2O.sub.3; 0-5 mol. % Li.sub.2O; 8-18 mol. % Na.sub.2O; 0-5
mol. % K.sub.2O; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. %
ZrO.sub.2; 0.05-0.25 mol. % SnO.sub.2; 0.05-0.5 mol. % CeO.sub.2;
less than 50 ppm As.sub.2O.sub.3; and less than 50 ppm
SbO.sub.2O.sub.3; where 14 mol.
%.ltoreq.(Li.sub.2O+Na.sub.2O+K2O).ltoreq.18 mol. % and 2 mol.
%.ltoreq.(MgO+CaO).ltoreq.7 mol. %.
[0031] In another embodiment, an alkali aluminosilicate glass
comprises, consists essentially of, or consists of: 61-75 mol. %
SiO.sub.2; 7-15 mol. % Al.sub.2O.sub.3; 0-12 mol. % B.sub.2O.sub.3;
9-21 mol. % Na.sub.2O; 0-4 mol. % K.sub.2O; 0-7 mol. % MgO; and 0-3
mol. % CaO.
[0032] In a particular embodiment, an alkali aluminosilicate glass
comprises alumina, at least one alkali metal and, in some
embodiments, greater than 50 mol. % SiO.sub.2, in other embodiments
at least 58 mol. % SiO.sub.2, and in still other embodiments at
least 60 mol. % SiO.sub.2, wherein the ratio
Al 2 .times. O 3 + B 2 .times. O 3 modifiers > 1 ,
##EQU00001##
where in the ratio the components are expressed in mol. % and the
modifiers are alkali metal oxides. This glass, in particular
embodiments, comprises, consists essentially of, or consists of:
58-72 mol. % SiO.sub.2; 9-17 mol. % Al.sub.2O.sub.3; 2-12 mol. %
B.sub.2O.sub.3; 8-16 mol. % Na.sub.2O; and 0-4 mol. % K.sub.2O,
wherein the ratio
Al 2 .times. O 3 + B 2 .times. O 3 modifiers > 1.
##EQU00002##
[0033] In yet another embodiment, an alkali aluminosilicate glass
substrate comprises, consists essentially of, or consists of: 60-70
mol. % SiO.sub.2; 6-14 mol. % Al.sub.2O.sub.3; 0-15 mol. %
B.sub.2O.sub.3; 0-15 mol. % Li.sub.2O; 0-20 mol. % Na.sub.2O; 0-10
mol. % K.sub.2O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. %
ZrO.sub.2; 0-1 mol. % SnO.sub.2; 0-1 mol. % CeO.sub.2; less than 50
ppm As.sub.2O.sub.3; and less than 50 ppm Sb.sub.2O.sub.3; wherein
12 mol. %.ltoreq.Li.sub.2O+Na.sub.2O+K.sub.2O.ltoreq.20 mol. % and
0 mol. %.ltoreq.MgO+CaO.ltoreq.10 mol. %.
[0034] In still another embodiment, an alkali aluminosilicate glass
comprises, consists essentially of, or consists of: 64-68 mol. %
SiO.sub.2; 12-16 mol. %Na.sub.2O; 8-12 mol. % Al.sub.2O.sub.3; 0-3
mol. % B.sub.2O.sub.3; 2-5 mol. % K.sub.2O; 4-6 mol. % MgO; and 0-5
mol. % CaO, wherein: 66 mol.
%.ltoreq.SiO.sub.2+B.sub.2O.sub.3+CaO.ltoreq.69 mol. %;
Na.sub.2O+K.sub.2O+B.sub.2O.sub.3+MgO+CaO+SrO>10 mol. %; 5 mol.
%.ltoreq.MgO+CaO+SrO.ltoreq.8 mol. %;
(Na.sub.2O+B.sub.2O.sub.3)--Al.sub.2O.sub.3.ltoreq.2 mol. %; 2 mol.
%.ltoreq.Na.sub.2O--Al.sub.2O.sub.3.ltoreq.6 mol. %; and 4 mol.
%.ltoreq.(Na.sub.2O+K.sub.2O)--Al.sub.2O.sub.3.ltoreq.10 mol.
%.
[0035] The chemically-strengthened as well as the
non-chemically-strengthened glass, in some embodiments, is batched
with 0-2 mol. % of at least one fining agent selected from a group
that includes Na.sub.2SO.sub.4, NaCl, NaF, NaBr, K.sub.2SO.sub.4,
KCl, KF, KBr, and SnO.sub.2.
[0036] In one example embodiment, sodium ions in the glass can be
replaced by potassium ions from the molten bath, though other
alkali metal ions having a larger atomic radius, such as rubidium
or cesium, can replace smaller alkali metal ions in the glass.
According to particular embodiments, smaller alkali metal ions in
the glass can be replaced by Ag+ ions. Similarly, other alkali
metal salts such as, but not limited to, sulfates, halides, and the
like may be used in the ion exchange process.
[0037] The replacement of smaller ions by larger ions at a
temperature below that at which the glass network can relax
produces a distribution of ions across the surface of the glass
that results in a stress profile. The larger volume of the incoming
ion produces a compressive stress (CS) on the surface and tension
(central tension, or CT) in the center region of the glass. The
compressive stress is related to the central tension by the
following relationship:
CS = CT .function. ( t - 2 .times. DOL DOL ) ##EQU00003##
where t is the total thickness of the glass sheet and DOL is the
depth of exchange, also referred to as depth of layer.
[0038] According to various embodiments, thin glass laminates
comprising one or more sheets of ion-exchanged glass and having a
specified depth of layer versus compressive stress profile possess
an array of desired properties, including low weight, high impact
resistance, and improved sound attenuation.
[0039] In one embodiment, a chemically-strengthened glass sheet can
have a surface compressive stress of at least 300 MPa, e.g., at
least 400, 500, or 600 MPa, a depth of at least about 20 .mu.m
(e.g., at least about 20, 25, 30, 35, 40, 45, or 50 .mu.m) and/or a
central tension greater than 40 MPa (e.g., greater than 40, 45, or
50 MPa) and less than 100 MPa (e.g., less than 100, 95, 90, 85, 80,
75, 70, 65, 60, or 55 MPa).
[0040] An example embodiment is illustrated in FIG. 4, which shows
a depth of layer versus compressive stress plot for various glass
sheets. In FIG. 4, data from a comparative soda lime glass are
designated by diamonds "SL" while data from chemically-strengthened
aluminosilicate glasses are designated by triangles "GG." As shown
in the illustrated embodiment, the depth of layer versus surface
compressive stress data for the chemically-strengthened sheets can
be defined by a compressive stress of greater than about 600 MPa,
and a depth of layer greater than about 20 micrometers. A region
200 is defined by a surface compressive stress greater than about
600 MPa, a depth of layer greater than about 40 micrometers, and a
tensile stress between about 40 and 65 MPa. Independently of, or in
conjunction with, the foregoing relationships, the
chemically-strengthened glass can have depth of layer that is
expressed in terms of the corresponding surface compressive stress.
In one example, the near surface region extends from a surface of
the first glass sheet to a depth of layer (in micrometers) of at
least 65-0.06(CS), where CS is the surface compressive stress and
has a value of at least 300 MPa. This linear relationship is
pictured by the sloped line in FIG. 4. Satisfactory CS and DOL
levels are located above the line 65-0.06(CS) on a plot of DOL on
the y-axis and CS on the x-axis.
[0041] In a further example, the near surface region extends from a
surface of the first glass sheet to a depth of layer (in
micrometers) having a value of at least B-M(CS), where CS is the
surface compressive stress and is at least 300 MPa. In the
foregoing expression, B can range from about 50 to 180 (e.g., 60,
70, 80, 90, 100, 110, 120, 130, 140, 150, 160.+-.5), and M can
range independently from about -0.2 to -0.02 (e.g., -0.18, -0.16,
-0.14, -0.12, -0.10, -0.08, -0.06, -0.04.+-.-0.01).
[0042] A modulus of elasticity of a chemically-strengthened glass
sheet can range from about 60 GPa to 85 GPa (e.g., 60, 65, 70, 75,
80 or 85 GPa). The modulus of elasticity of the glass sheet(s) and
the polymer interlayer can affect both the mechanical properties
(e.g., deflection and strength) and the acoustic performance (e.g.,
transmission loss) of the resulting glass laminate.
[0043] Example glass sheet forming methods include fusion draw and
slot draw processes, which are each examples of a down-draw
process, as well as float processes. The fusion draw process uses a
drawing tank that has a channel for accepting molten glass raw
material. The channel has weirs that are open at the top along the
length of the channel on both sides of the channel. When the
channel fills with molten material, the molten glass overflows the
weirs. Due to gravity, the molten glass flows down the outside
surfaces of the drawing tank. These outside surfaces extend down
and inwardly so that they join at an edge below the drawing tank.
The two flowing glass surfaces join at this edge to fuse and form a
single flowing sheet. The fusion draw method offers the advantage
that, because the two glass films flowing over the channel fuse
together, neither outside surface of the resulting glass sheet
comes in contact with any part of the apparatus. Thus, the surface
properties of the fusion drawn glass sheet are not affected by such
contact.
[0044] The slot draw method is distinct from the fusion draw
method. Here the molten raw material glass is provided to a drawing
tank. The bottom of the drawing tank has an open slot with a nozzle
that extends the length of the slot. The molten glass flows through
the slot/nozzle and is drawn downward as a continuous sheet and
into an annealing region. The slot draw process can provide a
thinner sheet than the fusion draw process because only a single
sheet is drawn through the slot, rather than two sheets being fused
together.
[0045] Down-draw processes produce glass sheets having a uniform
thickness that possess surfaces that are relatively pristine.
Because the strength of the glass surface is controlled by the
amount and size of surface flaws, a pristine surface that has had
minimal contact has a higher initial strength. When this high
strength glass is then chemically strengthened, the resultant
strength can be higher than that of a surface that has been a
lapped and polished. Down-drawn glass may be drawn to a thickness
of less than about 2 mm. In addition, down drawn glass has a very
flat, smooth surface that can be used in its final application
without costly grinding and polishing.
[0046] In the float glass method, a sheet of glass that may be
characterized by smooth surfaces and uniform thickness is made by
floating molten glass on a bed of molten metal, typically tin. In
an example process, molten glass that is fed onto the surface of
the molten tin bed forms a floating ribbon. As the glass ribbon
flows along the tin bath, the temperature is gradually decreased
until a solid glass sheet can be lifted from the tin onto rollers.
Once off the bath, the glass sheet can be cooled further and
annealed to reduce internal stress.
[0047] Glass sheets can be used to form glass laminates. As defined
herein, a thin glass laminate structure may include two
chemically-strengthened glass sheets and a polymer interlayer
formed between the glass sheets. The polymer interlayer can
comprise a monolithic polymer sheet, a multilayer polymer sheet, or
a composite polymer sheet. The polymer interlayer can be, for
example, one or more PVB sheets and/or one or more SentryGlas
sheets.
[0048] Glass laminates for automotive glazing and other
applications can be formed using a variety of processes. In an
example process, one or more sheets of chemically-strengthened
glass sheets are assembled in a pre-press with a polymer
interlayer, tacked into a pre-laminate, and finished into an
optically clear glass laminate. The assembly, in an example
embodiment that comprises two glass sheets, involves laying down a
first sheet of glass, overlaying a polymer interlayer, such as a
PVB (or SentryGlas) sheet, laying down a second sheet of glass, and
then trimming the excess PVB to the edges of the glass sheets. The
tacking step can include expelling most of the air from the
interfaces and partially bonding the PVB to the glass sheets. The
finishing step, typically carried out at elevated temperature and
pressure, completes the mating of each of the glass sheets to the
polymer interlayer.
[0049] The polymer (or thermoplastic), such as PVB or SentryGlas,
may be applied as a preformed polymer interlayer. The polymer layer
can, in certain embodiments, have a thickness of at least about
0.125 mm (e.g., 0.125, 0.25, 0.375, 0.5, 0.75, 0.76 or 1 mm). The
thermoplastic layer can cover most or, preferably, substantially
all of the opposed major faces of the two glass sheets. The
interlayer may also cover the edge faces of the glass sheets after
laminating. The glass sheet(s) in contact with the thermoplastics
layer may be heated above the softening point of the polymer, such
as, for example, at least 5.degree. C. or 10.degree. C. above the
softening point, to promote bonding of the thermoplastic material
to the glass. The heating can be performed with the glass ply in
contact with the thermoplastic layers under pressure.
[0050] Select commercially available polymer interlayer materials
for the interlayer 16 are summarized in Table 1, which provides
also the glass transition temperature and modulus for each product
sample. Glass transition temperature and modulus data were
determined from technical data sheets available from the vendor or
using a DSC 200 Differential Scanning Calorimeter (Seiko
Instruments Corp., Japan) or by ASTM D638 method for the glass
transition and modulus data, respectively. A further description of
the acrylic/silicone resin materials used in the ISD resin is
disclosed in U.S. Pat. No. 5,624,763, and a description of the
acoustic modified PVB resin is disclosed in Japanese Patent No.
05138840, the entire contents of which are hereby incorporated by
reference in their entirety.
TABLE-US-00001 TABLE 1 Example Polymer Interlayer Materials
Interlayer Material T.sub.g(.degree. C.) Modulus, psi (MPa) EVA
(STR Corp., Enfield, CT) -20 750-900 (5.2-6.2) EMA (Exxon Chemical
Co., -55 <4,500 (27.6) Baytown, TX) EMAC (Chevron Corp., Orange,
TX) -57 <5,000 (34.5) PVC plasticized (Geon Company, -45
<1500 (10.3) Avon Lake, OH) PVB plasticized (Solutia, 0 <5000
(34.5) St. Louis, MO) Polyethylene, Metallocene-catalyzed -60
<11,000 (75.9) (Exxon Chemical Co., Baytown, TX) Thermoplastic
polyurethanes -40 ISD resin (3M Corp., Minneapolis, MN) -20
Acoustic modified PVB 140 (Sekisui KKK, Osaka, Japan) Uvekol A
(liquid curable resins) (Cytec, Woodland Park, NJ)
[0051] A modulus of elasticity of the polymer interlayer can range
from about 1 MPa to 75 MPa (e.g., about 1, 2, 5, 10, 15, 20, 25, 50
or 75 MPa). At a loading rate of 1 Hz, a modulus of elasticity of a
standard PVB interlayer can be about 15 MPa, and a modulus of
elasticity of an acoustic grade PVB interlayer can be about 2
MPa.
[0052] A plurality of polymer interlayers may be incorporated into
a thin glass laminate to provide complimentary or distinct
functionality, including adhesion promotion, acoustic control, UV
transmission control, and/or IR transmission control.
[0053] During the lamination process, the interlayer is typically
heated to a temperature effective to soften the interlayer, which
promotes a conformal mating of the interlayer to respective
surfaces of the glass sheets. For PVB, a lamination temperature can
be about 140.degree. C. Mobile polymer chains within the interlayer
material develop bonds with the glass surfaces, which promote
adhesion. Elevated temperatures also accelerate the diffusion of
residual air and/or moisture from the glass-polymer interface.
[0054] The optional application of pressure both promotes flow of
the interlayer material, and suppresses bubble formation that
otherwise could be induced by the combined vapor pressure of water
and air trapped at the interfaces. To suppress bubble formation,
heat and pressure can be simultaneously applied to the assembly in
an autoclave.
[0055] Thin glass laminates can be formed using substantially
identical glass sheets or, in alternate embodiments,
characteristics of the individual glass sheets such as composition,
ion exchange profile and/or thickness can be independently varied
to form an asymmetric glass laminate.
[0056] Thin glass laminates can be used to provide beneficial
effects, including the attenuation of acoustic noise, reduction of
UV and/or IR light transmission, and/or enhancement of the
aesthetic appeal of a window opening. The individual glass sheets
comprising the disclosed thin glass laminates, as well as the
formed laminates, can be characterized by one or more attributes,
including composition, density, thickness, surface metrology, as
well as various properties including mechanical, optical, and
sound-attenuation properties. Various aspects of the disclosed thin
glass laminates are described herein.
[0057] The weight savings associated with using thinner glass
sheets can be seen with reference to Table 2, which shows the glass
weight, interlayer weight, and glass laminate weight for exemplary
thin glass laminates having a real dimension of 110 cm.times.50 cm
and a polymer interlayer comprising a 0.76 mm thick sheet of PVB
having a density of 1.069 g/cm3.
TABLE-US-00002 TABLE 2 Physical properties of glass sheet/PVB/glass
sheet laminate. Thickness Glass Weight PVB weight Laminate weight
(mm) (g) (g) (g) 4 5479 445 11404 3 4110 445 8664 2 2740 445 5925
1.4 1918 445 4281 1 1370 445 3185 0.7 959 445 2363 0.5 685 445
1815
[0058] As can be seen with reference to Table 2, by decreasing the
thickness of the individual glass sheets, the total weight of the
laminate can be dramatically reduced. In some applications, a lower
total weight translates directly to greater fuel economy.
[0059] The thin glass laminates can be adapted for use, for
example, as windows or glazings, and configured to any suitable
size and dimension. In embodiments, the glass laminates have a
length and width that independently vary from 10 cm to 1 m or more
(e.g., 0.1, 0.2, 0.5, 1, 2, or 5 m). Independently, the glass
laminates can have an area of greater than 0.1 m2, e.g., greater
than 0.1, 0.2, 0.5, 1, 2, 5, 10, or 25 m2.
[0060] The thin glass laminates can be substantially flat or shaped
for certain applications. For instance, the glass laminates can be
formed as bent or shaped parts for use as windshields or cover
plates. The structure of a shaped glass laminate may be simple or
complex. In certain embodiments, a shaped glass laminate may have a
complex curvature where the glass sheets have a distinct radius of
curvature in two independent directions. Such shaped glass sheets
may thus be characterized as having "cross curvature," where the
glass is curved along an axis that is parallel to a given dimension
and also curved along an axis that is perpendicular to the same
dimension. An automobile sunroof, for example, typically measures
about 0.5 m by 1.0 m and has a radius of curvature of 2 to 2.5 m
along the minor axis, and a radius of curvature of 4 to 5 m along
the major axis.
[0061] Shaped thin glass laminates according to certain embodiments
can be defined by a bend factor, where the bend factor for a given
part is equal to the radius of curvature along a given axis divided
by the length of that axis. Thus, for the example automotive
sunroof having radii of curvature of 2 m and 4 m along respective
axes of 0.5 m and 1.0 m, the bend factor along each axis is 4.
Shaped thin glass laminates can have a bend factor ranging from 2
to 8 (e.g., 2, 3, 4, 5, 6, 7, or 8).
[0062] Methods for bending and/or shaping thin glass laminates can
include gravity bending, press bending and methods that are hybrids
thereof. In a traditional method of gravity bending thin, flat
sheets of glass into curved shapes, such as automobile windshields,
cold, pre-cut single or multiple glass sheets are placed onto the
rigid, pre-shaped, peripheral support surface of a bending fixture.
The bending fixture may be made using a metal or a refractory
material. In an example method of the present disclosure, an
articulating bending fixture may be used. Prior to bending, the
glass typically is supported only at a few contact points. The
glass is heated, usually by exposure to elevated temperatures in a
lehr, which softens the glass allowing gravity to sag or slump the
glass into conformance with the peripheral support surface.
Substantially the entire support surface generally will then be in
contact with the periphery of the glass.
[0063] A related technique is press bending where flat glass sheets
are heated to a temperature corresponding substantially to the
softening point of the glass. The heated sheets are then pressed or
shaped to a desired curvature between male and female mold members
having complementary shaping surfaces. In embodiments, a
combination of gravity bending and press bending techniques can be
used.
[0064] A total thickness of the thin glass laminate can range from
about 2 mm to about 4 mm, where the individual glass sheets (e.g.,
one or more chemically-strengthened glass sheets) can have a
thickness of from about 0.5 to about 2 mm (e.g., 0.1, 0.2, 0.3,
0.5, 0.7, 1, 1.4, 1.7, or 2 mm). In embodiments, a
chemically-strengthened glass sheet can have a thickness of less
than about 1.4 mm or less than about 1.0 mm. In further
embodiments, a thickness of a chemically-strengthened glass sheet
can be substantially equal to a thickness of a second glass sheet,
such that the respective thicknesses vary by no more than 5%, e.g.,
less than 5, 4, 3, 2 or 1%. According to embodiments, the second
(e.g., inner) glass sheet can have a thickness less than about 2.0
mm (e.g., less than 1.4 mm). Without wishing to be bound by theory,
Applicants believe that a thin glass laminate comprising opposing
glass sheets having substantially identical thicknesses can provide
a maximum coincidence frequency and corresponding maximum in the
acoustic transmission loss at the coincidence dip. Such a design
can provide beneficial acoustic performance for the glass laminate,
for example, in automotive applications.
[0065] Example glass laminate structures are illustrated in Table
3, where the abbreviation GG refers to a chemically-strengthened
aluminosilicate glass sheet, and the term "soda lime" refers to a
non-chemically-strengthened glass sheet. As used herein, the
abbreviations "SP," "S-PVB" or simply "PVB" may be used for
standard grade PVB. The abbreviations "AP" or "A-PVB" are used for
acoustic grade PVB.
[0066] Applicants have shown that the laminate glass structures
disclosed herein have excellent durability, impact resistance,
toughness, and scratch resistance. As is well known among skilled
artisans, the strength and mechanical impact performance of a glass
sheet or laminate can be limited by defects in the glass, including
both surface and internal defects. When a glass laminate is
impacted the impact point is put into compression, while a ring or
"hoop" around the impact point, as well as the opposite face of the
impacted sheet, are put into tension. Typically, the origin of
failure will be at a flaw, usually on the glass surface, at or near
the point of highest tension. This may occur on the opposite face,
but can occur within the ring. If a flaw in the glass is put into
tension during an impact event, the flaw will likely propagate, and
the glass will typically break. Thus, a high magnitude and depth of
compressive stress (depth of layer) is preferable. The addition of
controlled flaws to surface 3 and acid etch treatment of surfaces 2
and 4 provide such laminates with the desired breakage performance
upon internal and external impact events.
[0067] Due to chemical strengthening, one or both of the external
surfaces of the thin glass laminates disclosed herein are under
compression. In order for flaws to propagate and failure to occur,
the tensile stress from an impact must exceed the surface
compressive stress at the tip of the flaw. In embodiments, the high
compressive stress and high depth of layer of
chemically-strengthened glass sheets enable the use of thinner
glass than in the case of non-chemically-strengthened glass.
[0068] In an embodiment hereof, a thin glass laminate can comprise
inner and outer glass sheets, such as chemically-strengthened glass
sheets wherein the outer-facing chemically-strengthened glass sheet
has a surface compressive stress of at least about 300 MPa, e.g.,
at least 400, 450, 500, 550, 600, 650, 700, 750 or 800 MPa, a depth
of at least about at least about 20 .mu.m (e.g., at least about 20,
25, 30, 35, 40, 45, or 50 .mu.m) and/or a central tension greater
than about 40 MPa (e.g., greater than about 40, 45, or 50 MPa) and
less than about 100 MPa (e.g., less than about 100, 95, 90, 85, 80,
75, 70, 65, 60, or 55 MPa) and the inner-facing glass sheet (e.g.,
an inner chemically-strengthened glass sheet) has a surface
compressive stress of from one-third to one-half the surface
compressive stress of the outer chemically-strengthened glass
sheet, or equal that of the outer glass sheet.
[0069] In addition to their mechanical properties, the acoustic
damping properties of the disclosed thin glass laminates have also
been evaluated. As will be appreciated by a skilled artisan,
laminated structures with a central acoustic interlayer 16, such as
a commercially available acoustic PVB interlayer, can be used to
dampen acoustic waves. The chemically-strengthened thin glass
laminates disclosed herein can dramatically reduce acoustic
transmission while using thinner (and lighter) structures that also
possess the requisite mechanical properties for many glazing
applications.
[0070] The present disclosure describes thin glass laminate
structures 20 made using a composite interlayer 10 consisting of
relatively stiff, rigid outer layers 12 and 14 combined with a
relatively softer sound damping central layer 16. The stiff layers
12 and 14 provide improved load/deformation properties to laminates
made using relatively thin glass, while the softer sound damping
central layer 16 provide improved acoustics through reduced sound
transmission.
[0071] Acoustic damping is determined by interlayer shear modulus
and loss factor. When the interlayer is a large fraction of the
total laminate thickness the bending rigidity (load deformation
properties) will largely be determined by Young's modulus. Using
multilayer interlayers these properties can be adjusted
independently resulting in a laminate with satisfactory rigidity
and acoustic damping.
[0072] Laminated thin glass structures according to the present
description may be used as decorative and sound dampening panels on
kitchen appliances and in elevator cabs, for example, as well as
for windows in vehicle and architectural applications. In an
appliance application, for example, a transparent thin glass
laminate as described herein may be adhered to the stainless steel
front of a dishwasher or other appliances in order to provide a
scratch resistant, easy to clean surface and sound insulating
properties, while retaining the beauty of the stainless steel that
is visible through the thin glass laminate. Alternatively, the
glass laminate may be colored or patterned, such as with a wood,
stone, granite, marble, picture, graphic or any other desired
pattern, in order to provide a sound dampening decorative glass
panel on a devise or structure. In an appliance application, such a
decorative panel may replace or eliminate the need for the
stainless steel panel.
[0073] Commercially available interlayers that are candidates for
to be used to produce the composite interlayer include SentryGlas
Ionomer+PVB; SentryGlas Ionomer+acoustic PVB (e.g. Sekisui's thin
0.4 mm thick acoustic PVB); SentryGlas Ionomer+EVA; SentryGlas
Ionomer+TPU; stiff PVB (e.g. Saflex DG)+standard PVB; stiff
PVB+acoustic PVB; stiff PVB+EVA; and stiff PVB+TPU. The use of all
PVB layers, e.g. for each of the outer layers 12 and 14 and the
central layer 16, may be advantageous because of the chemical
compatibility between the layers. SentryGlas is less chemically
compatibility with other interlayer materials such as EVA or PVB
and may require a binder film (for example: a polyester film)
between the outer and central layers.
[0074] The present description discloses light-weight thin glass
laminates having acceptable mechanical and acoustic damping
properties. The present description also discloses polymer
interlayers and laminated thin glass structures whose mechanical
and acoustic properties can be independently engineered by
relatively simple adjustments of properties of the individual
layers of the polymer interlayer. The layers of the laminated glass
structures described herein are individual layers, films or sheet
that are bonded together during the lamination process. The layers
of the interlayer structures 10 described herein may be coextruded
together to form a single interlayer sheet with multiple
layers.
[0075] Unless otherwise expressly stated, it is in no way intended
that any method set forth herein be construed as requiring that its
steps be performed in a specific order. Accordingly, where a method
claim does not actually recite an order to be followed by its steps
or it is not otherwise specifically stated in the claims or
descriptions that the steps are to be limited to a specific order,
it is no way intended that any particular order be inferred.
[0076] It will be apparent to those skilled in the art that various
modifications and variations can be made without departing from the
spirit or scope of the invention. Since modifications combinations,
sub-combinations and variations of the disclosed embodiments
incorporating the spirit and substance of the invention may occur
to persons skilled in the art, the invention should be construed to
include everything within the scope of the appended claims and
their equivalents.
* * * * *