U.S. patent application number 15/134539 was filed with the patent office on 2016-08-18 for strengthened glass substrates with glass frits and methods for making the same.
The applicant listed for this patent is CORNING INCORPORATED. Invention is credited to Melinda Ann Drake, Lisa Ann Lamberson, Robert Michael Morena.
Application Number | 20160236966 15/134539 |
Document ID | / |
Family ID | 48464105 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160236966 |
Kind Code |
A1 |
Drake; Melinda Ann ; et
al. |
August 18, 2016 |
STRENGTHENED GLASS SUBSTRATES WITH GLASS FRITS AND METHODS FOR
MAKING THE SAME
Abstract
Strengthened glass substrates with glass frits and methods for
forming the same are disclosed. According to one embodiment, a
method for forming a glass frit on a glass substrate may include
providing a glass substrate comprising a compressive stress layer
extending from a surface of the glass substrate into a thickness of
the glass substrate, the compressive stress having a depth of layer
DOL and an initial compressive stress CS.sub.i. A glass frit
composition may be deposited on at least a portion of the surface
of the glass substrate. Thereafter, the glass substrate and the
glass frit composition are heated in a furnace to sinter the glass
frit composition and bond the glass frit composition to the glass
substrate, wherein, after heating, the glass substrate has a fired
compressive stress CS.sub.f which is greater than or equal to
0.70*CS.sub.i.
Inventors: |
Drake; Melinda Ann;
(Corning, NY) ; Lamberson; Lisa Ann; (Painted
Post, NY) ; Morena; Robert Michael; (Lindley,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING INCORPORATED |
CORNING |
NY |
US |
|
|
Family ID: |
48464105 |
Appl. No.: |
15/134539 |
Filed: |
April 21, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13464493 |
May 4, 2012 |
9346708 |
|
|
15134539 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03C 3/17 20130101; C03C
3/19 20130101; C03C 17/04 20130101; Y10T 428/315 20150115; C03C
8/08 20130101; C03C 4/18 20130101; Y10T 428/24942 20150115; C03C
2204/00 20130101; C03C 3/21 20130101; C03C 4/02 20130101; C03C
2207/00 20130101 |
International
Class: |
C03C 8/08 20060101
C03C008/08; C03C 4/18 20060101 C03C004/18; C03C 3/21 20060101
C03C003/21 |
Claims
1. An automotive glazing comprising: a glass substrate comprising a
compressive stress layer extending from a surface of the glass
substrate into a thickness of the glass substrate, the compressive
stress layer having a depth of layer DOL and a fired compressive
stress CS.sub.f; a glass frit is fully vitrified and bonded to at
least a portion of the surface of the glass substrate, wherein: the
glass frit has a softening point of less than or equal to
400.degree. C., a glass transition temperature which is less than
or equal to 375.degree. C., and a sintering temperature of less
than 450.degree. C.; and the fired compressive stress CS.sub.f is
greater than or equal to 0.70 of an initial compressive stress
CS.sub.i of the glass substrate prior to the glass frit being
bonded to at least a portion of the glass substrate.
2. The glazing of claim 1, wherein the substrate comprises a
substrate coefficient of thermal expansion CTE.sub.S is in a range
from about 80.times.10.sup.-7/.degree. C. to about
95.times.10.sup.-7/.degree. C. over a temperature range from
0.degree. C. to 300.degree. C.; and the glass frit has a frit
coefficient of thermal expansion CTE.sub.F which is within
+/-10.times.10.sup.-7/.degree. C. of the substrate coefficient of
thermal expansion CTE.sub.S.
3. The glazing of claim 2, wherein the glass frit has a coefficient
of thermal expansion CTE.sub.F which is within
+/-5.times.10.sup.-7/.degree. C. of the coefficient of thermal
expansion CTE.sub.S of the glass substrate.
4. The glazing of claim 2, wherein the glass frit has a coefficient
of thermal expansion CTE.sub.F which is within
+/-2.5.times.10.sup.-7/.degree. C. the coefficient of thermal
expansion CTE.sub.S of the glass substrate.
5. The glazing of claim 2, wherein the glass frit has a coefficient
of thermal expansion CTE.sub.F which is within
+/-0.5.times.10.sup.-7/.degree. C. the coefficient of thermal
expansion CTE.sub.S of the glass substrate.
6. The glazing of claim 1, wherein the glass substrate comprises an
alkali aluminosilicate glass or an alkali borosilicate glass.
7. The glazing of claim 1, wherein the glass substrate comprises a
first surface, a second surface opposite the first surface, and a
perimeter edge, wherein the glass frit is positioned on the first
surface of the glass substrate directly adjacent to the perimeter
edge of the glass substrate.
8. The glazing of claim 7, further comprising any one or more of an
electrical lead, wires, and antennas, wherein the glass frit
conceals the one or more of the electrical lead, wires, and
antennas.
9. The glazing of claim 1, wherein the initial compressive stress
CS.sub.i is greater than about 600 MPa.
10. The glazing of claim 1, wherein the DOL is greater than about
30 .mu.m.
11. The glazing of claim 1, wherein the glass frit is substantially
black in color.
12. The glazing of claim 1, wherein the glass frit comprises a
Sb--V-phosphate glass frit composition.
13. The glazing of claim 12, wherein the glass frit composition
comprises V.sub.2O.sub.5 in an amount greater than or equal to
about 40 mol. % and less than or equal to about 60 mol. %,
P.sub.2O.sub.5 in an amount greater than equal to about 15 mol. %
and less than or equal to about 30 mol. %, and Sb.sub.2O.sub.3 in
an amount greater than or equal to about 10 mol. % and less than or
equal to about 35 mol. %.
14. The glazing of claim 12, wherein the glass frit composition
further comprises any one or more of Al.sub.2O.sub.3,
Fe.sub.2O.sub.3, and TiO.sub.2.
15. The glazing of claim 1, wherein the glass frit comprises a
composition having a glass transition temperature in the range from
about 300.degree. C. to about 350.degree. C. and a sintering
temperature from about 400.degree. C. to about 425.degree. C.
16. An automotive glazing comprising: a glass substrate comprising
a compressive stress layer extending from a surface of the glass
substrate into a thickness of the glass substrate, the compressive
stress layer having a depth of layer DOL and a fired compressive
stress CS.sub.f, and a substrate coefficient of thermal expansion
CTE.sub.S is in a range from about 80.times.10.sup.-7/.degree. C.
to about 95.times.10.sup.-7/.degree. C. over a temperature range
from 0.degree. C. to 300.degree. C. a glass frit is fully vitrified
and bonded to at least a portion of the surface of the glass
substrate, wherein the glass frit has a softening point of less
than or equal to 400.degree. C., a glass transition temperature
which is less than or equal to 375.degree. C., a sintering
temperature of less than 450.degree. C., and a frit coefficient of
thermal expansion CTE.sub.F which is within
+/-10.times.10.sup.-7/.degree. C. of the substrate coefficient of
thermal expansion CTE.sub.S; and the fired compressive stress
CS.sub.f is greater than or equal to 0.70 of an initial compressive
stress CS.sub.i of the glass substrate prior to the glass frit
being bonded to at least a portion of the glass substrate.
17. The automotive glazing of claim 16, wherein the glass frit
comprises a Sb--V-phosphate glass frit composition, the glass frit
composition includes from about 40 mol. % to about 60 mol. %
V.sub.2O.sub.5; from about 15 mol. % to about 30 mol. %
P.sub.2O.sub.5; from about 20 mol. % to about 35 mol. %
Sb.sub.2O.sub.3; from about 0 mol. % to about 2 mol. %
Al.sub.2O.sub.3; from about 0 mol. % to about 5 mol. %
Fe.sub.2O.sub.3; and from about 0 mol. % to about 2 mol. %
TiO.sub.2.
18. The automotive glazing of claim 17, wherein the glass frit
composition is free of antimony and compounds containing
antimony.
19. The automotive glazing of claim 17, wherein the glass substrate
comprises a first surface, a second surface opposite the first
surface, and a perimeter edge, wherein the glass frit is positioned
on the first surface of the glass substrate directly adjacent to
the perimeter edge of the glass substrate, wherein the glazing
further comprises any one or more of an electrical lead, wires, and
antennas attached to the glass substrate, and wherein the glass
frit conceals the one or more of the electrical lead, wires, and
antennas.
20. An automotive glazing comprising: a glass substrate comprising
a first surface, a second surface opposite the first surface, a
perimeter edge, and any one or more of an electrical lead, wires,
and antennas, the glass substrate further comprising a compressive
stress layer extending from a surface of the glass substrate into a
thickness of the glass substrate, the compressive stress layer
having a depth of layer DOL and a fired compressive stress CS.sub.f
that is greater than or equal to 420 MPa and a substrate
coefficient of thermal expansion CTE.sub.S is in a range from about
80.times.10.sup.-7/.degree. C. to about 95.times.10.sup.-7/.degree.
C. over a temperature range from 0.degree. C. to 300.degree. C.; a
glass frit fully vitrified and bonded to at least a portion of the
first surface of the glass substrate directly adjacent to the
perimeter edge of the glass substrate, wherein the glass frit has a
softening point of less than or equal to 400.degree. C., a glass
transition temperature which is less than or equal to 375.degree.
C., a sintering temperature of less than 450.degree. C., and a frit
coefficient of thermal expansion CTE.sub.F which is within
+/-10.times.10.sup.-7/.degree. C. of the substrate coefficient of
thermal expansion CTE.sub.S.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional and claims the benefit of
priority under 35 U.S.C. .sctn.120 of U.S. patent application Ser.
No. 13/464,493 filed on May 4, 2012, the content of which is relied
upon and incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] The present specification generally relates to strengthened
glass substrates and, more specifically, to ion-exchange
strengthened glass substrates with glass frits applied to at least
a portion of the surface and methods for making the same.
[0004] 2. Technical Background
[0005] Ion exchange strengthening is used to improve the mechanical
resistance of glass in numerous applications ranging from hand-held
consumer smart-phones and electronic tablets to automotive glazing.
Ion exchange strengthening is of particular interest in automotive
glazing. Conventional automotive glazing is typically formed from
soda-lime silica glass that has been thermally tempered to induce a
surface compressive stress and improve the resistance of the
glazing to mechanical failure following damage such as scratches,
chips or the like. However, the amount of residual compressive
stress imparted by thermal tempering is not high (on the order of
200 MPa-300 MPa). Accordingly, automotive glazing needs to be
relatively thick to assure that the glazing will withstand high
mechanical loads before failure occurs.
[0006] Ion exchange processes generally impart a greater amount of
compressive stress (typically on the order of 600 MPa to 800 MPa)
to glass articles compared to thermal tempering processes.
Accordingly, ion exchanged glass articles generally have a greater
resistance to mechanical failure than similar glass articles which
are thermally tempered. This means that the ion exchanged glass
articles may be formed with a reduced thickness while still
retaining the same or even improved resistance to mechanical
failure relative to thermally tempered glass articles.
[0007] However, in the case of automotive glazing, the compressive
stress introduced by ion exchange may be diminished during
subsequent processing steps, such as the application of glass frit
to the surface of the automotive glazing, thereby mitigating the
benefits of ion exchange strengthening.
[0008] Accordingly, a need exists for alternative strengthened
glass substrates with glass frits which retain the benefits of ion
exchange strengthening.
SUMMARY
[0009] According to one embodiment, a method for forming a glass
frit on a glass substrate may include providing a glass substrate
comprising a compressive stress layer extending from a surface of
the glass substrate into a thickness of the glass substrate, the
compressive stress having a depth of layer DOL and an initial
compressive stress CS.sub.i. A glass frit composition may be
deposited on at least a portion of the surface of the glass
substrate. Thereafter, the glass substrate and the glass frit
composition are heated in a furnace to sinter the glass frit
composition and bond the glass frit composition to the glass
substrate. After heating, the glass frit composition is fully
vitrified and the glass substrate has a fired compressive stress
CS.sub.f which is greater than or equal to 0.70*CS.sub.i.
[0010] In another embodiment, a method for forming a glass frit on
a glass substrate may include providing a glass substrate
comprising a compressive stress layer extending from a surface of
the glass substrate into a thickness of the glass substrate. The
compressive stress may have a depth of layer DOL and an initial
compressive stress CS.sub.i. A glass frit composition may be
deposited on at least a portion of the surface of the glass
substrate. The glass frit composition may have a softening point
which is less than or equal to 400.degree. C. Thereafter, the glass
substrate and the glass frit composition may be heated in a furnace
to a temperature less than or equal to 450.degree. C. such that,
after heating, the glass frit composition is fully vitrified,
sintered, and bonded to the glass substrate.
[0011] In yet another embodiment, a glass substrate may include a
compressive stress layer extending from a surface of the glass
substrate into a thickness of the glass substrate. The compressive
stress may have a depth of layer DOL and a fired compressive stress
CS.sub.f. A glass frit may be fully vitrified and bonded to at
least a portion of the surface of the glass substrate. The glass
frit may have a softening point of less than or equal to
400.degree. C., a glass transition temperature which is less than
or equal to 375.degree. C., and a sintering temperature of less
than 450.degree. C. The fired compressive stress CS.sub.f of the
glass substrate may be greater than or equal to 0.70 of an initial
compressive stress CS.sub.i of the glass substrate prior to the
glass frit being bonded to at least a portion of the glass
substrate.
[0012] Additional features and advantages of the strengthened glass
substrates with glass frits will be set forth in the detailed
description which follows, and in part will be readily apparent to
those skilled in the art from that description or recognized by
practicing the embodiments described herein, including the detailed
description which follows, the claims, as well as the appended
drawings.
[0013] It is to be understood that both the foregoing general
description and the following detailed description describe various
embodiments and are intended to provide an overview or framework
for understanding the nature and character of the claimed subject
matter. The accompanying drawings are included to provide a further
understanding of the various embodiments, and are incorporated into
and constitute a part of this specification. The drawings
illustrate the various embodiments described herein, and together
with the description serve to explain the principles and operations
of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 schematically depicts a strengthened glass substrate
with a glass frit applied to the perimeter of the glass substrate
according to one or more embodiments shown and described
herein;
[0015] FIG. 2 schematically depicts a partial cross section of the
strengthened glass substrate of FIG. 1; and
[0016] FIG. 3 graphically depicts the glass transition temperature
(y-axis) as a function of the concentration of V.sub.2O.sub.5
(x-axis) for substitutions of V.sub.2O.sub.5 for Sb.sub.2O.sub.3 in
an exemplary glass frit composition.
DETAILED DESCRIPTION
[0017] Reference will now be made in detail to embodiments of the
strengthened glass substrates with glass frits and methods for
making the same, examples of which are illustrated in the
accompanying drawings. Whenever possible, the same reference
numerals will be used throughout the drawings to refer to the same
or like parts. One embodiment of a strengthened glass substrate
with a glass frit is schematically depicted in FIG. 1. In one
embodiment, the method for forming the glass frit on the glass
substrate may include providing a glass substrate comprising a
compressive stress layer extending from a surface of the glass
substrate into a thickness of the glass substrate. The compressive
stress may have a depth of layer DOL and an initial compressive
stress CS.sub.i. A glass frit composition may be deposited on at
least a portion of the surface of the glass substrate. Thereafter,
the glass substrate and the glass frit composition are heated in a
furnace to fully vitrify and sinter the glass frit composition and
bond the glass frit composition to the glass substrate. After
heating, the glass substrate has a fired compressive stress
CS.sub.f which is greater than or equal to 0.70*CS.sub.i. Methods
for forming the glass frit on the strengthened glass substrate and
strengthened glass substrates with glass frits will be described in
more detail herein with specific reference to the appended
drawings.
[0018] The term "CTE," as used herein, refers to the average
coefficient of thermal expansion of the specified component (i.e.,
the glass substrate or the glass frit) in a temperature range from
0.degree. C. to 300.degree. C.
[0019] The phrase "softening point," as used herein, refers to the
temperature at which the glass frit composition has a viscosity of
1.times.10.sup.7.6 kp.
[0020] The phrase "glass transition temperature," as used herein,
refers to the temperature at which the glass frit composition
transitions from a liquid to a solid as the liquid is cooled.
[0021] In the embodiments of the glass frit compositions described
herein, the concentration of constituent components (e.g., SnO,
P.sub.2O.sub.5, V.sub.2O.sub.5, and the like) are specified in mole
percent (mol. %) on an oxide basis, unless otherwise specified.
[0022] The phrase "substantially free," as used herein, refers to
the concentration of the identified component being present in a
composition in a trace amount of less than or equal to about 1 mol.
%.
[0023] Glass substrates, such as automotive glazing and cover
glasses for electronic devices, may include a glass frit applied to
one or more surfaces of the glass substrate. The glass frit may be
used to conceal various electrical components that are attached to
the glass substrate or which may otherwise be visible through the
glass substrate. The glass frit is usually applied to the glass
substrate in a paste form and subsequently fired to sinter the
glass frit and to bond the glass frit to the glass substrate.
Coventional glass frits for such applications generally have
relatively high softening points and glass transition temperatures
and, as such, require relatively high firing temperatures
(600.degree. C. to 700.degree. C.).
[0024] It is also desirable to chemically strengthen glass
substrates by ion exchange to improve the mechanical strength and
durability of the glass substrates. However, when the glass frit is
applied to the strengthened glass substrates and the glass
substrates are fired to sinter and bond the glass frit, the
relatively high firing temperatures of conventional glass frits
(i.e., in the range of 600.degree. C. to 700.degree. C.) cause the
compressive stress in the strengthened glass substrates to
diminish, reducing or eliminating any strength benefit obtained
through the ion exchange process.
[0025] The glass substrates with glass frits and methods for
forming the same described herein mitigate the loss of compressive
stress in the glass substrate.
[0026] Referring now to FIGS. 1 and 2, one embodiment of a
strengthened glass substrate 100 with a glass frit 106 is
schematically depicted. The glass substrate generally has a first
surface 104, a second surface 110 opposite the first surface 104,
and a perimeter edge 102. In the embodiment of the glass substrate
100 depicted in FIG. 1, the glass frit 106 is positioned on the
first surface 104 of the glass substrate directly adjacent to the
perimeter edge 102 of the glass substrate 100.
[0027] In the embodiments described herein, the glass substrate 100
may be used as a cover glass for electronic devices, such as tablet
computers, smart phones, automated teller machines or the like.
Alternatively, the glass substrate 100 may be used for automotive
glazing. In this embodiment, glass frit 106 located about the
perimeter of the glass substrate may be used to conceal components
which are attached to one of the surfaces of the glass substrate,
such as electrical leads, wires, antennas, or the like.
[0028] In the embodiments described herein, the glass substrate 100
is formed from ion exchangeable glass. In an exemplary embodiment,
the glass substrate 100 may be formed from glass code 2318 alkali
aluminosilicate glass manufactured by Corning, Inc. which is
commercially available as Gorilla.TM. glass. However, it should be
understood that the glass substrate 100 may be formed from other
types of ion-exchangeable glass including, without limitation,
alkali borosilicate glasses or the like.
[0029] In the embodiments described herein, the glass substrate 100
is ion exchange strengthened such that the glass substrate 100 has
a layer of compressive stress which extends from the surfaces 104,
110 of the glass substrate into the thickness of the glass
substrate 100. This layer of compressive stress extends from each
surface 104, 110 to a depth of layer 108 (DOL). The depth of layer
108 from the first surface 104 is schematically depicted in FIG. 2.
The glass substrate generally has an initial compressive stress
CS.sub.i which is a maximum at the surface of the glass substrate
prior to application and sintering of the glass frit 106. The
compressive stress decreases with increasing distance into the
thickness of the glass substrate 100.
[0030] In some embodiments described herein, the depth of layer DOL
may be greater than or equal to about 30 .mu.m or even greater than
or equal to about 40 .mu.m. In some other embodiments, the depth of
layer may be greater than 50 .mu.m. However, it should be
understood that the glass substrate may have a depth of layer which
is less than 30 .mu.m.
[0031] In some embodiments described herein, the initial
compressive stress CS.sub.i may be greater than or equal to 600 MPa
or even greater than or equal to about 650 MPa. In some other
embodiments, the initial compressive stress CS.sub.i may be greater
than 700 MPa or even greater than 800 MPa. However, it should be
understood that initial compressive stresses of less than 600 MPa
are also contemplated.
[0032] The glass substrate generally has a coefficient of thermal
expansion CTE.sub.S. In general, the coefficient of thermal
expansion CTE.sub.S of the glass substrate is closely matched to
the coefficient of thermal expansion CTE.sub.F of the glass frit
106, as will be described in more detail herein. In some
embodiments, the coefficient of thermal expansion CTE.sub.S of the
glass substrate is greater than or equal to about
80.times.10.sup.-7/.degree. C. and less than or equal to
95.times.10.sup.-7/.degree. C. However, it should be understood
that the coefficient of thermal expansion CTE.sub.S of the glass
substrate may vary depending on the specific composition of the
glass substrate.
[0033] The glass frit compositions from which the glass frit 106 is
formed generally have sintering temperatures T.sub.s which are less
than or equal to 450.degree. C. In some embodiments, the sintering
temperatures of the glass frit compositions are less than
425.degree. C. or even less than 400.degree. C. These relatively
low sintering temperatures facilitate sintering the glass frit
compositions and bonding the glass frit compositions to
strengthened glass substrates, such as ion exchange strengthened
glass substrates, without a significant reduction in the
compressive stress of the glass substrate due to stress
relaxation.
[0034] Specifically, the glass substrate to which the glass frit
composition is applied may have an initial compressive stress
CS.sub.i following ion exchange. After the glass frit composition
is applied to the glass substrate and heated to the sintering
temperature T.sub.s to facilitate fully vitrifying and sintering
the glass frit composition and bonding the glass frit composition
to the glass substrate, the glass substrate has a fired compressive
stress CS.sub.f which is less than the initial compressive stress
CS.sub.f. In the embodiments described herein, the fired
compressive stress CS.sub.f is generally greater than or equal to
0.70*CS.sub.i (i.e., the fired compressive stress CS.sub.f is
greater than or equal to 70% of the initial compressive stress). In
some of these embodiments, the fired compressive stress may be
greater than or equal to 0.75*CS.sub.i or even 0.80*CS.sub.i. This
minimum reduction in compressive stress is due to the relatively
low firing temperatures needed to sinter the glass frit composition
and bond the glass frit composition to the glass substrate.
[0035] The relatively low firing temperatures of the glass frit
composition are achieved by utilizing glass frit compositions which
generally have relatively low glass transition temperatures T.sub.g
and relatively low softening points. Specifically, the glass frit
compositions described herein generally have glass transition
temperatures T.sub.g which are less than or equal to about
375.degree. C. or even less than or equal to about 350.degree. C.
In some embodiments, the glass transition temperatures T.sub.g of
the glass frit compositions are greater than or equal to about
300.degree. C. and less than or equal to 375.degree. C. In some
embodiments, the glass transition temperatures T.sub.g of the glass
frit compositions are greater than or equal to about 300.degree. C.
and less than or equal to 350.degree. C. In some of these
embodiments, the glass transition temperatures may be greater than
or equal to about 300.degree. C. and less than or equal to
325.degree. C.
[0036] The glass frit compositions described herein also have
relatively low softening points. Specifically, the glass frit
compositions described herein generally have softening points which
are less than or equal to 400.degree. C. In some embodiments, the
softening points of the glass frit compositions are greater than or
equal to about 350.degree. C. and less than or equal to 400.degree.
C. which generally correspond to the glass frit compositions having
sintering temperatures in the range from about 400.degree. C. to
about 450.degree. C. In some of these embodiments, the softening
points of the glass frit compositions may be greater than or equal
to about 350.degree. C. and less than or equal to 375.degree.
C.
[0037] In order to further minimize the reduction of compressive
stress in the strengthened glass substrate 100, the glass frit
compositions have sintered coefficients of thermal expansion
CTE.sub.F which closely match the coefficient of thermal expansion
CTE.sub.S of the glass substrate when the glass frit composition is
sintered and bonded to the glass substrate. Specifically, if the
coefficient of thermal expansion CTE.sub.F of the glass frit is
greater than the coefficient of thermal expansion CTE.sub.S of the
glass substrate, the compressive stress in the surface of the glass
substrate in areas where the glass frit is bonded to the glass
substrate may be diminished or the surface of the glass substrate
may even be in tension in localized areas. Accordingly, in the
embodiments described herein, the sintered coefficient of thermal
expansions CTE.sub.F of the glass frit composition is within
+/-10.times.10.sup.-7/.degree. C. of the coefficient of thermal
expansion CTE.sub.S of the glass substrate or even within
+/-5.times.10.sup.-7/.degree. C. of the coefficient of thermal
expansion CTE.sub.S of the glass substrate. In some of these
embodiments, the sintered coefficient of thermal expansion
CTE.sub.F of the glass frit compositions is within
+/-2.5.times.10.sup.-7/.degree. C. the coefficient of thermal
expansion CTE.sub.S of the glass substrate or even within
+/-0.5.times.10.sup.-7/.degree. C. the coefficient of thermal
expansion CTE.sub.S of the glass substrate.
[0038] In some embodiments, the glass frit composition may be
substantially black in color upon sintering. Glass frit which
sinters black is particularly suitable for use in automotive
glazing applications where a black frit is generally desired.
However, it should be understood that glass frit which sinters
black may be used in other applications, including, without
limitation, for cover panels for electronic devices. Further, while
glass frit compositions which sinter black have been described
herein as being suitable for specific applications, it should be
understood that the glass frit composition may have other fired
colors and that the color of the glass frit may be altered by
adding certain colorants to the glass frit composition and/or to
the glass batch from which the glass frit composition is
formed.
[0039] In one exemplary embodiment, the glass frit is formed from a
Sb--V-phosphate glass frit composition which includes
V.sub.2O.sub.5, P.sub.2O.sub.5 and Sb.sub.2O.sub.3. In this
exemplary embodiment, V.sub.2O.sub.5 is used to control the glass
transition temperature of the glass frit composition. Specifically,
increasing the concentration of V.sub.2O.sub.5 in the glass frit
composition generally reduces the glass transition temperature of
the glass frit composition. When the concentration of
V.sub.2O.sub.5 in the glass frit composition is less than about 40
mol. %, the glass transition temperature of the glass frit
composition is too high to achieve the desired relatively low
sintering temperature of 450.degree. C. However, if the
concentration of V.sub.2O.sub.5 in the glass frit composition is
too high, the aqueous durability of the glass frit composition is
diminished. Accordingly, in the embodiments of the Sb--V-phosphate
glass frit compositions described herein, V.sub.2O.sub.5 is present
in the glass frit composition in a concentration greater than or
equal to about 40 mol. % and less than or equal to about 60 mol. %.
In some embodiments, the concentration of V.sub.2O.sub.5 may be
greater than or equal to about 50 mol. % and less than or equal to
about 60 mol. %.
[0040] Additions of P.sub.2O.sub.5 in the Sb--V-phosphate glass
frit composition acts as a glass former and stabilizes the frit.
When the concentration of P.sub.2O.sub.5 is the glass frit is less
than about 15 mol. %, the glass frit composition crystallizes at
low temperatures which is undesired. When the concentration of
P.sub.2O.sub.5 is greater than about 30 mol. %, the glass
transition temperature and the softening point of the glass frit
become too high to achieve the desired relatively low sintering
temperature of 450.degree. C. Accordingly, in the embodiments of
the Sb--V-phosphate glass frit compositions described herein,
P.sub.2O.sub.5 is present in the glass frit composition in a
concentration greater than equal to about 15 mol. % and less than
or equal to about 30 mol. %. In some embodiments, the concentration
of P.sub.2O.sub.5 may be greater than or equal to about 25 mol. %
and less than or equal to about 30 mol. %. In some other
embodiments, the concentration of P.sub.2O.sub.5 may be greater
than or equal to about 23 mol. % and less than or equal to about 25
mol. %.
[0041] Additions of Sb.sub.2O.sub.3 in the Sb--V-phosphate glass
frit compositions improve the aqueous durability of the glass frit
composition. When the concentration of Sb.sub.2O.sub.3 in the glass
frit is less than about 10 mol. %, the aqueous durability of the
glass frit composition is diminished. When the concentration of
Sb.sub.2O.sub.3 is greater than about 35 mol. %, the glass
transition temperature of the glass frit become too high to achieve
the desired relatively low sintering temperature of 450.degree. C.
Accordingly, in the embodiments of the Sb--V-phosphate glass frit
compositions described herein, Sb.sub.2O.sub.3 is present in the
glass frit composition in a concentration greater than or equal to
about 10 mol. % and less than or equal to about 35 mol. %. In some
embodiments, the concentration of Sb.sub.2O.sub.3 may be greater
than or equal to about 10 mol. % and less than or equal to about 20
mol. %. In this embodiment, the glass frit composition exhibits
good viscous flow and acceptable aqueous durability. In some other
embodiments, the concentration of Sb.sub.2O.sub.3 may be greater
than or equal to about 20 mol. % and less than or equal to about 35
mol. %. In some other embodiments, the concentration of
Sb.sub.2O.sub.3 may be greater than or equal to about 23 mol. % and
less than or equal to about 25 mol. %. In these embodiments, the
frit composition exhibits excellent aqueous durability and
acceptable viscous flow characteristics.
[0042] The exemplary Sb--V-phosphate glass frit compositions may
optionally include additional constituent components such as
Al.sub.2O.sub.3, Fe.sub.2O.sub.3, and TiO.sub.2. For example,
Al.sub.2O.sub.3 may be included in a concentration greater than or
equal to about 0 mol. % and less than or equal to 2.0 mol. %. The
presence of Al.sub.2O.sub.3 generally improves the aqueous
durability of the glass frit composition. However, if the
concentration of Al.sub.2O.sub.3 exceeds 2.0 mol. %, the aluminum
in the glass frit composition may precipitate out which is
undesirable.
[0043] TiO.sub.2 may be included in the glass composition to
improve the viscous flow of the glass frit composition. However,
when the concentration of TiO.sub.2 exceeds about 2 mol. % the
aqueous durability of the glass frit composition may be decreased.
Accordingly, in the exemplary Sb--V-phosphate glass frit
compositions, the concentration of TiO.sub.2, when included, may be
greater than or equal to about 0 mol. % and less than or equal to
about 2 mol. %.
[0044] Fe.sub.2O.sub.3 may be included in the glass composition to
stabilize the oxidation state of the vanadium constituent
components. In the embodiments in the exemplary Sb--V-phosphate
glass frit compositions, the concentration of Fe.sub.2O.sub.3, when
included, may be greater than or equal to about 0 mol. % and less
than or equal to about 5 mol. % or even greater than or equal to
about 0 mol. % and less than or equal to about 2.5 mol. %.
[0045] The exemplary Sb--V-phosphate glass frit compositions
described herein generally have glass transition temperatures in
the range from about 300.degree. C. to about 350.degree. C. These
glass frit compositions have a sintering temperature from about
400.degree. C. to about 425.degree. C. Accordingly, the exemplary
Sb--V-phosphate glass frit compositions may be fully vitrified,
sintered and bonded to glass substrates at temperatures less than
450.degree. C. Moreover, the Sb--V-phosphate glass frit
compositions generally have a sintered coefficient of thermal
expansion CTE.sub.F in the range from about
70.times.10.sup.-7/.degree. C. to about 80.times.10.sup.-7/.degree.
C. and a softening point in the range from about 350.degree. C. to
about 400.degree. C.
[0046] In one exemplary embodiment of the Sb--V-phosphate glass
frit composition, the glass frit composition includes from about 40
mol. % to about 60 mol. % V.sub.2O.sub.5; from about 15 mol. % to
about 30 mol. % P.sub.2O.sub.5; from about 20 mol. % to about 35
mol. % Sb.sub.2O.sub.3; from about 0 mol. % to about 2 mol. %
Al.sub.2O.sub.3; from about 0 mol. % to about 5 mol. %
Fe.sub.2O.sub.3; and from about 0 mol. % to about 2 mol. %
TiO.sub.2.
[0047] In another exemplary embodiment of the Sb--V-phosphate glass
frit composition, the glass frit composition includes from about 50
mol. % to about 60 mol. % V.sub.2O.sub.5; from about 25 mol. % to
about 30 mol. % P.sub.2O.sub.5; from about 10 mol. % to about 20
mol. % Sb.sub.2O.sub.3; from about 0 mol. % to about 2 mol. %
Al.sub.2O.sub.3; from about 0 mol. % to about 2.5 mol. %
Fe.sub.2O.sub.3; and from about 0 mol. % to about 2 mol. %
TiO.sub.2.
[0048] In another exemplary embodiment, the glass frit is formed
from a V-phosphate glass frit composition which includes
V.sub.2O.sub.5 and P.sub.2O.sub.5 but is free of antimony and
compounds containing antimony. In this exemplary embodiment,
V.sub.2O.sub.5 is used to control the glass transition temperature
of the glass frit composition. Specifically, increasing the
concentration of V.sub.2O.sub.5 in the glass frit composition
generally reduces the glass transition temperature of the glass
frit composition. When the concentration of V.sub.2O.sub.5 in the
glass frit composition is less than about 30 mol. %, the glass frit
composition exhibits poor viscous flow. However, if the
concentration of V.sub.2O.sub.5 in the glass frit composition is
greater than about 50 mol. %, the aqueous durability of the glass
frit composition is diminished. Accordingly, in the embodiments of
the V-phosphate glass frit compositions described herein,
V.sub.2O.sub.5 is present in the glass frit composition in a
concentration greater than or equal to about 30 mol. % and less
than or equal to about 50 mol. %. In some embodiments, the
concentration of V.sub.2O.sub.5 may be greater than or equal to
about 35 mol. % and less than or equal to about 45 mol. %.
[0049] Additions of P.sub.2O.sub.5 in the V-phosphate glass frit
composition acts as a glass former and stabilizes the frit. When
the concentration of P.sub.2O.sub.5 is the glass frit is less than
about 10 mol. %, the glass frit composition crystallizes at low
temperatures which is undesired. When the concentration of
P.sub.2O.sub.5 is greater than about 30 mol. %, the glass
transition temperature and the softening point of the glass frit
become too high to achieve the desired relatively low sintering
temperature of 450.degree. C. Accordingly, in the embodiments of
the V-phosphate glass frit compositions described herein,
P.sub.2O.sub.5 is present in the glass frit composition in a
concentration greater than equal to about 10 mol. % and less than
or equal to about 30 mol. %. In some embodiments, the concentration
of P.sub.2O.sub.5 may be greater than or equal to about 15 mol. %
and less than or equal to about 25 mol. %.
[0050] The V-phosphate glass frit compositions may also include
additional constituent components such as Fe.sub.2O.sub.3,
TiO.sub.2, and ZnO. TiO.sub.2 may be included in the glass
composition to improve the viscous flow of the glass frit
composition. However, when the concentration of TiO.sub.2 exceeds
about 30 mol. % the aqueous durability of the glass frit
composition may be decreased. When the concentration of TiO.sub.2
is less than about 10 mol. %, the viscous flow of the glass frit
composition is poor. Accordingly, in the exemplary V-phosphate
glass frit compositions, the concentration of TiO.sub.2 is greater
than or equal to about 10 mol. % and less than or equal to about 30
mol. %. In some embodiments, the concentration of TiO.sub.2 is
greater than or equal to about 12 mol. % and less than or equal to
about 25 mol. %.
[0051] Fe.sub.2O.sub.3 may be included in the glass frit
composition to stabilize the oxidation state of the vanadium
constituent components. When the concentration of Fe.sub.2O.sub.3
is greater than about 30 mol. %, the glass transition temperature
of the glass frit is too high. However, when the concentration of
Fe.sub.2O.sub.3 is less than about 10 mol. %, the aqueous
durability of the glass frit composition is low. Accordingly, in
the embodiments in the exemplary V-phosphate glass frit
compositions, the concentration of Fe.sub.2O.sub.3 may be greater
than or equal to about 10 mol. % and less than or equal to about 30
mol. % or even greater than or equal to about 12 mol. % and less
than or equal to about 25 mol. %.
[0052] ZnO may be added to the glass composition to improve the
viscous flow of the glass frit composition. However, when the
concentration of ZnO in the glass frit composition is greater than
about 10 mol. %, the aqueous durability of the glass frit
composition is low. In the exemplary V-phosphate glass frit
compositions described herein, the concentration of ZnO may be
greater than or equal to about 0 mol. % and less than or equal to
about 10 mol. %. In some embodiments, the concentration of ZnO is
greater than or equal to 3 mol. % and less than or equal to 7 mol.
%.
[0053] The exemplary V-phosphate glass frit compositions described
herein generally have glass transition temperatures in the range
from about 350.degree. C. to about 375.degree. C. These glass frit
compositions have a sintering temperature from about 425.degree. C.
to about 450.degree. C. Accordingly, the exemplary V-phosphate
glass frit compositions may be fully vitrified, sintered and bonded
to glass substrates at temperatures less than 450.degree. C.
Moreover, the V-phosphate glass frit compositions generally have a
sintered coefficient of thermal expansion CTE.sub.F in the range
from about 50.times.10.sup.-7/.degree. C. to about
70.times.10.sup.-7/.degree. C. and a softening point in the range
from about 350.degree. C. to about 400.degree. C.
[0054] In one exemplary embodiment of the V-phosphate glass frit
composition, the glass frit composition includes from about 30 mol.
% to about 50 mol. % V.sub.2O.sub.5; from about 10 mol. % to about
30 mol. % P.sub.2O.sub.5; from about 0 mol. % to about 10 mol. %
ZnO; from about 10 mol. % to about 30 mol. % Fe.sub.2O.sub.3; and
from about 10 mol. % to about 30 mol. % TiO.sub.2. The V-phosphate
glass frit composition is substantially free from antimony and
compounds containing antimony.
[0055] In another exemplary embodiment of the V-phosphate glass
frit composition, the glass frit composition includes about 40 mol.
% V.sub.2O.sub.5; about 20 mol. % P.sub.2O.sub.5; about 5 mol. %
ZnO; about 17.5 mol. % Fe.sub.2O.sub.3; and about 17.5 mol. %
TiO.sub.2. The V-phosphate glass frit composition is substantially
free from antimony and compounds containing antimony.
[0056] In another exemplary embodiment, the glass frit may be
formed from a Sn--Zn-phophate glass frit composition which includes
SnO, P.sub.2O.sub.5, ZnO and B.sub.2O.sub.3. In this exemplary
embodiment, SnO is used to control the glass transition temperature
of the glass frit composition. Specifically, increasing the
concentration of SnO in the glass frit composition generally
reduces the glass transition temperature of the glass frit
composition. When the concentration of SnO in the glass frit
composition is less than about 50 mol. %, the glass transition
temperature of the glass frit composition is too high to achieve
the desired relatively low sintering temperature of 450.degree. C.
However, if the concentration of SnO in the glass frit composition
is greater than about 75 mol. %, the CTE of the glass frit
composition is too high. Accordingly, in the embodiments of the
Sn--Zn-phosphate glass frit compositions described herein, SnO is
present in the glass frit composition in a concentration greater
than or equal to about 50 mol. % and less than or equal to about 75
mol. %. In some embodiments, the concentration of SnO may be
greater than or equal to about 50 mol. % and less than or equal to
about 65 mol. %.
[0057] Additions of P.sub.2O.sub.5 in the Sn--Zn-phosphate glass
frit composition act as a glass former and stabilize the frit. When
the concentration of P.sub.2O.sub.5 is the glass frit is less than
about 28 mol. %, the glass frit composition crystallizes at low
temperatures which is undesired. When the concentration of
P.sub.2O.sub.5 is greater than about 35 mol. %, the glass
transition temperature and the softening point of the glass frit
become too high to achieve the desired relatively low sintering
temperature of 450.degree. C. Accordingly, in the embodiments of
the Sn--Zn-phosphate glass frit compositions described herein,
P.sub.2O.sub.5 is present in the glass frit composition in a
concentration greater than or equal to about 28 mol. % and less
than or equal to about 35 mol. %. In some embodiments, the
concentration of P.sub.2O.sub.5 may be greater than or equal to
about 30 mol. % and less than or equal to about 33 mol. %.
[0058] Additions of ZnO in the Sn--Zn-phosphate glass frit
composition aid in improving the aqueous durability of the glass
frit composition. When the concentration of ZnO in the glass frit
composition is greater than about 10 mol. %, the glass transition
temperature and softening point of the glass frit become too high
to achieve the desired relatively low sintering temperature of
450.degree. C. However, when the concentration of ZnO in the glass
frit composition is less than about 2 mol. %, the aqueous
durability of the glass composition is diminished. Accordingly, in
the embodiments of the Sn--Zn-phosphate glass frit compositions
described herein, ZnO is present in the glass frit composition in a
concentration greater than or equal to about 2 mol. % and less than
or equal to about 10 mol. %. In some embodiments, the concentration
of ZnO may be greater than or equal to about 3 mol. % and less than
or equal to about 7 mol. %.
[0059] Additions of B.sub.2O.sub.3 in the Sn--Zn-phosphate glass
frit composition form boron-phosphate groups which improve the
aqueous durability of the glass composition. When the concentration
of B.sub.2O.sub.3 in the glass frit composition is less than about
1 mol. % no improvement in the aqueous durability is realized. When
the concentration of B.sub.2O.sub.3 is greater than about 5 mol. %,
the glass transition temperature and softening point of the glass
frit become too high to achieve the desired relatively low
sintering temperature of 450.degree. C. Accordingly, in the
embodiments of the Sn--Zn-phosphate glass frit compositions
described herein, B.sub.2O.sub.3 is present in the glass frit
composition in a concentration greater than equal to about 1 mol. %
and less than or equal to about 5 mol. %. In some embodiments, the
concentration of B.sub.2O.sub.3 may be greater than or equal to
about 2 mol. % and less than or equal to about 4.5 mol. %.
[0060] The exemplary Sn--Zn-phosphate glass frit compositions
described herein generally have glass transition temperatures in
the range from about 300.degree. C. to about 350.degree. C. These
glass frit compositions have a sintering temperature from about
425.degree. C. to about 450.degree. C. Accordingly, the exemplary
Sn--Zn-phosphate glass frit compositions may be fully vitrified,
sintered and bonded to a glass substrate at temperatures less than
450.degree. C. Moreover, the Sn--Zn-phosphate glass frit
compositions generally have a sintered coefficient of thermal
expansion CTE.sub.F in the range from about
90.times.10.sup.-7/.degree. C. to about
110.times.10.sup.-7/.degree. C. and a softening point from about
375.degree. C. to about 425.degree. C.
[0061] In one exemplary embodiment of the Sn--Zn-phosphate glass
frit composition described herein, the glass frit composition
includes from about 50 mol. % to about 75 mol. % SnO; from about 28
mol. % to about 35 mol. % P.sub.2O.sub.5; from about 2 mol. % to
about 10 mol. % ZnO; and from about 1 mol. % to about 5 mol. %
B.sub.2O.sub.3.
[0062] In the embodiments of the glass frit compositions described
herein, the glass frit compositions are substantially free from
lead.
[0063] Referring again to FIGS. 1 and 2, the glass frit is applied
to the glass substrate by first mixing a batch of the glass frit
constituent components and firing the batch under conditions
sufficient to render the batch into glass. Thereafter, the glass
formed from the glass frit composition is pulverized into powdered
glass. The powdered glass is then mixed with rheological aids, such
as Texanol.TM. ester alcohol or similar rheological aids, to form a
plasticized frit composition in the form of a paste.
[0064] The paste is deposited on at least a portion of one or more
surfaces of a glass substrate which has an initial compressive
stress CS.sub.i, as described above. For example, in the embodiment
of the glass substrate depicted in FIG. 1, the paste is deposited
as a bead directly adjacent to the perimeter edge 102 of the glass
substrate 100. While FIG. 1 depicts the paste as being deposited on
the perimeter edge of the glass substrate, it should be understood
that the paste may be applied to various locations on the surfaces
of the glass substrate or even on the edges of the glass substrate.
Various techniques may be used to apply the paste to the glass
substrate including, without limitation, screen printing, extruding
the paste through an applicator, or similar deposition
techniques.
[0065] Thereafter, the glass substrate 100 and the deposited glass
frit composition are heated in a furnace to sinter and fully
vitrify the glass frit composition and bond the glass frit
composition to the glass substrate. As noted hereinabove, the glass
substrates are generally heated to a maximum temperature which is
less than or equal to about 450.degree. C. in order to minimize
relaxation of the initial compressive stress CS.sub.i in the glass
substrate such that after heating, the glass substrate has a fired
compressive stress CS.sub.f which is greater than or equal to
0.70*CS.sub.i.
[0066] The glass substrate 100 with the applied glass frit
composition may be heated in stages. For example, in one
embodiment, the glass substrate 100 with the applied glass frit
composition may be initially positioned in a first furnace which is
heated to a first temperature T1 which is less than the sintering
temperature T.sub.s of the glass frit composition. The glass
substrate with the glass frit composition is held at this first
temperature T1 for a first holding time HT1 to facilitate the
burnout of any organic rheological aids in the glass frit
composition. This first temperature T1 may be in a temperature
range from about 300.degree. C. to about 350.degree. C. The first
holding time HT1 may be in the range from about 10 minutes to about
120 minutes.
[0067] Thereafter, the glass substrate with the applied glass frit
composition is positioned in a second furnace at a second
temperature T2 to sinter the glass frit and bond the glass frit to
the glass substrate. The second temperature T2 is greater than the
first temperature T1 and less than or equal to 450.degree. C. to
mitigate relaxation of the compressive stress in the glass
substrate. This second temperature generally corresponds to the
sintering temperature T.sub.s of the glass frit. In the embodiments
described herein the second temperature T2 is generally in the
range from about 400.degree. C. to about 450.degree. C. The glass
substrate is held at the second temperature T2 for a second holding
time HT2 such that the glass frit is fully sintered and bonded to
the glass substrate. In the embodiments described herein, the
second holding time HT2 is generally from about 5 minutes to about
30 minutes.
[0068] Thereafter, the glass substrate with the sintered glass frit
may be removed to a third furnace having an initial temperature
less than T2 and greater than room temperature, such as, for
example, about 380.degree. C., and cooled to room temperature at a
predetermined ramp rate. Alternatively, the glass substrate with
the sintered glass frit may be cooled at ambient temperatures.
[0069] While the aforementioned heating schedule has been described
as being performed in discrete furnaces, it should be understood
that the heating schedule may be performed using a conveyor furnace
in which the glass substrate with the applied glass frit
composition is conveyed through discrete zones of the furnace on a
conveyor system and each zone of the furnace is set at the desired
temperature.
[0070] In another embodiment, the glass substrate with the applied
glass frit composition may be heated in stages in a single furnace.
For example, the glass substrate with the applied glass frit may be
positioned in a furnace and heated from room temperature to a first
temperature T1 at a first ramp rate R1. The first temperature T1 is
less than the sintering temperature T.sub.s of the glass frit
composition. In the embodiments described herein, the first
temperature T1 may be in a temperature range from about 300.degree.
C. to about 350.degree. C. The first ramp rate R1 may be from about
2.degree. C./minute to about 10.degree. C./minute. The glass
substrate and the applied glass frit may be held at the first
temperature T1 for a first holding time HT1 to facilitate the
burnout of any organic rheological aids in the glass frit
composition. The first holding time HT1 may be in the range from
about 10 minutes to about 120 minutes.
[0071] Thereafter, the glass substrate with the applied glass frit
may be heated from the first temperature T1 to a second temperature
T2 at a second ramp rate R2. The second temperature T2 is greater
than the first temperature T1 and less than or equal to 450.degree.
C. to mitigate relaxation of the compressive stress in the glass
substrate. This second temperature generally corresponds to the
sintering temperature T.sub.s of the glass frit. In the embodiments
described herein the second temperature T2 is generally in the
range from about 400.degree. C. to about 450.degree. C. The second
ramp rate R2 may be from about 2.degree. C./minute to about
20.degree. C./minute. The glass substrate and the applied glass
frit may be held at the second temperature T2 for a second holding
time HT2 such that the glass frit is fully sintered and bonded to
the glass substrate. In the embodiments described herein, the
second holding time HT2 is generally from about 10 minutes to about
30 minutes.
[0072] Thereafter, the glass substrate with the sintered glass frit
may be cooled to room temperature at a predetermined ramp rate or,
alternatively, at ambient temperatures.
EXAMPLES
[0073] Embodiments of the strengthened glass substrates with glass
frits and methods for forming the same will be further clarified
with the following examples.
Example 1
[0074] Five exemplary Sb--V-phosphate glass frit compositions
(samples A-E) were prepared with differing concentrations of
Sb.sub.2O.sub.3 and V.sub.2O.sub.5 to assess the impact of
substituting V.sub.2O.sub.5 for Sb.sub.2O.sub.3 on the glass
transition temperature of the glass frit composition. The
composition of each sample is listed below in Table 1. Each sample
was fired at 400.degree. C. and the glass transition temperature
was measured by differential scanning calorimetry. The measured
glass transition temperature of each sample is reported in Table 1
and the results are plotted in FIG. 3 as a function of the
concentration of V.sub.2O.sub.5. As shown in FIG. 3, the glass
transition temperature of the glass frit compositions generally
decreased as V.sub.2O.sub.5 was substituted for Sb.sub.2O.sub.3 in
the glass frit compositions.
TABLE-US-00001 TABLE 1 (Mol %) A B C D E Sb.sub.2O.sub.3 23.5 13.5
11.0 8.5 3.0 V.sub.2O.sub.5 47.5 57.5 60.0 62.5 67.5 P.sub.2O.sub.5
27.0 27.0 27.0 27.0 27.0 TiO.sub.2 1.0 1.0 1.0 1.0 1.0
Al.sub.2O.sub.3 1.0 1.0 1.0 1.0 1.0 Fe.sub.2O.sub.3 2.5 2.5 2.5 2.5
2.5 T.sub.g 351.degree. 331.degree. 327.degree. 317.degree.
294.degree.
Example 2
[0075] A glass frit composition was applied to the surface of four
sample glass substrates. The glass substrates were formed from
Corning glass code 2318 ion exchangeable glass. The four glass
substrates had an average initial compressive stress CS.sub.i of
754 MPa and a depth of layer of 39 microns. The glass frit
composition included 60 mol. % SnO, 32 mol. % P.sub.2O.sub.5, 6
mol. % ZnO, and 2 mol. % B.sub.2O.sub.3. The glass substrate and
applied glass frit composition were positioned in a furnace at
325.degree. C. and held for 20 minutes to facilitate binder
burnout. Thereafter, the glass substrates were moved to a
425.degree. C. furnace and held for 20 minutes to sinter the glass
frit composition. The glass substrates were then removed to a room
temperature furnace for cooling.
[0076] After cooling, the frit had a grey, matte to semi-gloss
appearance. The fired compressive stress CS.sub.f and depth of
layer DOL were measured. The fours glass substrates had an average
fired compressive stress of 608 MPa and a DOL of 42 microns. Based
on these measurements, the glass substrates had a 19.4% reduction
in compressive stress after firing. Accordingly, the fired
compressive stress CS.sub.f was greater than 80% of the initial
compressive stress CS.sub.i.
Example 3
[0077] A glass frit composition was applied to the surface of four
sample glass substrates. The glass substrates were formed from
Corning glass code 2318 ion exchangeable glass. The four glass
substrates had an average initial compressive stress CS.sub.i of
757 MPa and a depth of layer of 39 microns. The glass frit
composition included 60 mol. % SnO, 32 mol. % P.sub.2O.sub.5, 6
mol. % ZnO, and 2 mol. % B.sub.2O.sub.3. The glass substrate and
glass frit composition were positioned in a furnace and heated to
250.degree. C. at a ramp rate of 40.degree. C./min and held for 30
minutes to facilitate binder burnout. Thereafter, the temperature
of the furnace was increased to 450.degree. C. at a ramp rate of
25.degree. C./min and held for 20 minutes to sinter the glass frit
composition. The glass substrates were then moved to a room
temperature furnace for cooling.
[0078] After cooling, the frit had a grey, glossy appearance. The
fired compressive stress CS.sub.f and depth of layer DOL were
measured. The four glass substrates had an average fired
compressive stress CS.sub.f of 542 MPa and a DOL of 45 microns.
Based on these measurements, the glass substrates had a 28.4%
reduction in compressive stress after firing. Accordingly, the
fired compressive stress CS.sub.f was greater than 70% of the
initial compressive stress CS.sub.i.
Example 4
[0079] A glass frit composition was applied to the surface of 28
sample glass substrates. The glass substrates were formed from
Corning glass code 2318 ion exchangeable glass. The glass
substrates had an average initial compressive stress CS.sub.i of
647 MPa and a depth of layer of 39 microns. The glass frit
composition included 47.5 mol. % V.sub.2O.sub.5, 23.5 mol. %
P.sub.2O.sub.5, 27 mol. % Sb.sub.2O.sub.3, 1 mol. %
Al.sub.2O.sub.3, 1 mol. % TiO.sub.2, and 2.5 mol. %
Fe.sub.2O.sub.3. The glass substrates and applied glass frit
compositions were positioned in a furnace at 325.degree. C. and
held for 20 minutes to facilitate binder burnout. Thereafter, the
glass substrates were moved to a 400.degree. C. furnace and held
for 10 minutes to sinter the glass frit composition. The glass
substrates were then removed to a furnace heated to 380.degree. C.
and cooled to room temperature.
[0080] After cooling, the glass frit had a glossy black appearance.
The fired compressive stress CS.sub.f and depth of layer DOL were
measured. The 28 glass substrates had an average fired compressive
stress of 571 MPa and a DOL of 41 microns. Based on these
measurements, the glass substrates had an 11.7% reduction in
compressive stress after firing. Accordingly, the fired compressive
stress CS.sub.f was greater than 88% of the initial compressive
stress CS.sub.i.
Example 5
[0081] A glass frit composition was applied to the surface of 22
sample glass substrates. The glass substrates were formed from
Corning glass code 2318 ion exchangeable glass. The glass
substrates had an average initial compressive stress CS.sub.i of
733 MPa and a depth of layer of 40 microns. The glass frit
composition included 47.5 mol. % V.sub.2O.sub.5, 23.5 mol. %
P.sub.2O.sub.5, 27 mol. % Sb.sub.2O.sub.3, 1 mol. %
Al.sub.2O.sub.3, 1 mol. % TiO.sub.2, and 2.5 mol. %
Fe.sub.2O.sub.3. The glass substrates and applied glass frit
composition were positioned in a furnace and heated to 325.degree.
C. at a ramp rate of 5.degree. C./min and held for 20 minutes to
facilitate binder burnout. Thereafter, the temperature of the
furnace was increased to a 400.degree. C. at a ramp rate of
5.degree. C./min and held for 15 minutes to sinter the glass frit
composition. The glass substrates were then cooled to room
temperature at a rate of 5.degree. C./min.
[0082] After cooling, the glass frit had a glossy black appearance.
The fired compressive stress CS.sub.f and depth of layer DOL were
measured. The 22 glass substrates had an average fired compressive
stress of 612 MPa and a DOL of 42 microns. Based on these
measurements, the glass substrates had a 15.3% reduction in
compressive stress after firing. Accordingly, the fired compressive
stress CS.sub.f was greater than 84% of the initial compressive
stress CS.sub.i.
[0083] Based on the foregoing, it should now be understood that the
methods described herein may be used to produce strengthened glass
substrates with applied glass frits without a significant decrease
in the compressive stress imparted to the glass substrate by ion
exchange. It should also be understood that this benefit is
facilitated by applying glass frit compositions having relatively
low glass transition temperatures and relatively low softening
points to the strengthened glass substrate. Glass frit compositions
with these characteristics may be fully sintered at relatively low
temperatures thereby mitigating the loss of compressive stress due
to stress relaxation.
[0084] The strengthened glass articles with applied glass frits
described herein may be used in a variety of different applications
including, without limitation, cover panels for electronic devices,
automotive glazing, and the like.
[0085] It will be apparent to those skilled in the art that various
modifications and variations can be made to the embodiments
described herein without departing from the spirit and scope of the
claimed subject matter. Thus it is intended that the specification
cover the modifications and variations of the various embodiments
described herein provided such modification and variations come
within the scope of the appended claims and their equivalents.
* * * * *