U.S. patent application number 17/443202 was filed with the patent office on 2021-11-11 for glass ceramics, chemically strengthened glass, and semiconductor substrate.
This patent application is currently assigned to AGC Inc.. The applicant listed for this patent is AGC Inc.. Invention is credited to Yusuke ARAI, Hitomi FURUTA, Akio KOIKE, Qing LI, Kazutaka ONO, Shigeki SAWAMURA.
Application Number | 20210347682 17/443202 |
Document ID | / |
Family ID | 1000005784316 |
Filed Date | 2021-11-11 |
United States Patent
Application |
20210347682 |
Kind Code |
A1 |
LI; Qing ; et al. |
November 11, 2021 |
GLASS CERAMICS, CHEMICALLY STRENGTHENED GLASS, AND SEMICONDUCTOR
SUBSTRATE
Abstract
The present invention relates to a glass ceramic having a
visible-light transmittance of 85% or more in terms of a thickness
of 0.7 mm, and a haze value of 1.0% or less in terms of a thickness
of 0.7 mm, and including, in mass % on an oxide basis: 45-70% of
SiO.sub.2; 1-15% of Al.sub.2O.sub.3; and 10-25% of Li.sub.2O.
Inventors: |
LI; Qing; (Tokyo, JP)
; ARAI; Yusuke; (Tokyo, JP) ; KOIKE; Akio;
(Tokyo, JP) ; ONO; Kazutaka; (Tokyo, JP) ;
FURUTA; Hitomi; (Tokyo, JP) ; SAWAMURA; Shigeki;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AGC Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
AGC Inc.
Tokyo
JP
|
Family ID: |
1000005784316 |
Appl. No.: |
17/443202 |
Filed: |
July 22, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2019/033487 |
Aug 27, 2019 |
|
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|
17443202 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03C 2204/00 20130101;
C03C 4/18 20130101; C03C 21/002 20130101; H01L 23/15 20130101; C03C
10/0027 20130101 |
International
Class: |
C03C 10/00 20060101
C03C010/00; C03C 4/18 20060101 C03C004/18; H01L 23/15 20060101
H01L023/15; C03C 21/00 20060101 C03C021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 8, 2019 |
JP |
2019-021896 |
Claims
1. A glass ceramic having a visible-light transmittance of 85% or
more in terms of a thickness of 0.7 mm, and a haze value of 1.0% or
less in terms of a thickness of 0.7 mm, and comprising, in mass %
on an oxide basis: 45-70% of SiO.sub.2; 1-15% of Al.sub.2O.sub.3;
and 10-25% of Li.sub.2O.
2. The glass ceramic according to claim 1, having a content of
K.sub.2O of 5% or less in mass % on an oxide basis.
3. The glass ceramic according to claim 1, comprising lithium
metasilicate crystals.
4. The glass ceramic according to claim 1, comprising
lithiumphosphate crystals.
5. The glass ceramic according to claim 3, wherein, in a case where
lithium disilicate crystals are contained, the lithium disilicate
crystals have a crystal size of 45 nm or less, the crystal size
being determined using Scherrer equation from a width of an X-ray
diffraction peak of the lithium disilicate crystals.
6. The glass ceramic according to claim 1, having a glass
transition point that differs by 200.degree. C. or less from a
glass transition point of an amorphous glass having the same glass
composition as a glass composition of the glass ceramic.
7. The glass ceramic according to claim 1, wherein the haze value
is 0.4% or less in terms of a thickness of 0.7 mm.
8. A semiconductor-supporting substrate comprising the glass
ceramic according to claim 1.
9. A chemically strengthened glass having a compressive stress
layer in a surface thereof, the chemically strengthened glass being
a glass ceramic that has a visible-light transmittance of 85% or
more in terms of a thickness of 0.7 mm, and a haze value of 0.5% or
less in terms of a thickness of 0.7 mm, has a surface compressive
stress value of 500 MPa or more and a depth of the compressive
stress layer of 80 .mu.m or more, and comprises, in mass % on an
oxide basis: 45-70% of SiO.sub.2; 1-15% of Al.sub.2O.sub.3; and
10-25% of Li.sub.2O.
10. The chemically strengthened glass according to claim 9,
comprising lithium metasilicate crystals.
11. The chemically strengthened glass according to claim 10,
comprising lithiumphosphate crystals.
12. The chemically strengthened glass according to claim 9, having
a compressive stress value of 100 MPa or more at a depth of 50 m
from the surface.
13. The chemically strengthened glass according to claim 9, having
an average thermal expansion coefficient at 50.degree.
C.-350.degree. C. of 90.times.10.sup.-7/.degree.
C.-140.times.10.sup.-7/.degree. C.
14. The chemically strengthened glass according to claim 9, having
a Vickers hardness of 600 or more.
15. A semiconductor-supporting substrate comprising the chemically
strengthened glass according to claim 9.
16. An electronic appliance comprising the chemically strengthened
glass according to claim 9.
Description
TECHNICAL FIELD
[0001] The present invention relates to glass ceramics, chemically
strengthened glass, and a semiconductor-supporting substrate.
BACKGROUND ART
[0002] Chemically strengthened glasses are used as the cover
glasses of portable digital assistances, etc.
[0003] A chemically strengthened glass is obtained, for example, by
bringing a glass into contact with a molten salt which contains
alkali metal ions and causing ion exchange between alkali metal
ions contained in the glass and alkali metal ions contained in the
molten salt to form a compressive stress layer in the glass
surface.
[0004] Glass ceramics are obtained by precipitating crystals in a
glass, and is harder and less apt to receive scratches as compared
with amorphous glasses containing no crystals. Patent Literature 1
presents an example in which glass ceramics were chemically
strengthened by ion exchange treatment. However, glass ceramics are
inferior to amorphous glasses in transparency.
[0005] Patent Literature 2 describes transparent glass ceramics.
However, there are few transparent glass ceramics having high
transparency which renders the glass ceramics suitable for use as
cover glasses. The chemical strengthening properties of glass
ceramics are greatly affected by the glass composition and the
precipitated crystals. The scratch resistance and transparency of
the glass ceramics are also greatly affected by the glass
composition and the precipitated crystals. It is hence necessary to
delicately regulate a glass composition and precipitated crystals,
for obtaining glass ceramics excellent in terms of both chemical
strengthening property and transparency.
[0006] Meanwhile, in the field of semiconductor packaging,
techniques such as wafer-level packaging (WLP) or panel-level
packaging (PLP) are receiving attention (see Patent Literature 2).
These techniques are, for example, a technique in which silicon
chips are placed on a glass substrate and encapsulated by molding
an encapsulating resin.
[0007] In this technique, there are cases where the supporting
substrate is removed during the production. Widely used as the
supporting substrate are glass substrates. Since the glass
substrates are transparent, they can be made removable by
irradiation with laser light. The glass substrates for use as
supporting substrates are required to be less apt to be damaged in
the packaging step, not to scatter fragments upon breakage, and to
match in thermal expansion with the semiconductors.
CITATION LIST
Patent Literature
[0008] Patent Literature 1: JP-T-2016-529201 (The term "JP-T" as
used herein means a published Japanese translation of a PCT patent
application.)
[0009] Patent Literature 2: JP-A-2016-160136
SUMMARY OF INVENTION
Technical Problem
[0010] The present invention provides a glass ceramic excellent in
terms of transparency and chemical strengthening property. The
present invention further provides a chemically strengthened glass
which has a high thermal expansion coefficient, is excellent in
terms of transparency and strength, and is less apt to scatter
fragments upon breakage.
Solution to Problem
[0011] The present invention provides a glass ceramic having a
visible-light transmittance of 85% or more in terms of a thickness
of 0.7 mm, and a haze value of 1.0% or less in terms of a thickness
of 0.7 mm, and
[0012] including, in mass % on an oxide basis:
[0013] 45-70% of SiO.sub.2;
[0014] 1-15% of Al.sub.2O.sub.3; and
[0015] 10-25% of Li.sub.2O.
[0016] The present invention further provides a chemically
strengthened glass having a compressive stress layer in a surface
thereof, the chemically strengthened glass being a glass ceramic
that has a visible-light transmittance of 85% or more in terms of a
thickness of 0.7 mm, and a haze value of 0.5% or less in terms of a
thickness of 0.7 mm,
[0017] has a surface compressive stress value of 500 MPa or more
and a depth of the compressive stress layer of 80 .mu.m or more,
and
[0018] includes, in mass % on an oxide basis:
[0019] 45-70% of SiO.sub.2;
[0020] 1-15% of AlO.sub.3; and
[0021] 10-25% of Li.sub.2O.
[0022] The present invention further provides a
semiconductor-supporting substrate including the glass ceramic or
the chemically strengthened glass.
Advantageous Effects of Invention
[0023] According to the present invention, a glass ceramic
excellent in terms of transparency and chemical strengthening
property is obtained. Furthermore, a chemically strengthened glass
which has a high thermal expansion coefficient, is excellent in
terms of transparency and strength, and is less apt to scatter
fragments upon breakage is obtained.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a diagram illustrating one example of stress
profiles of a chemically strengthened glass.
[0025] FIG. 2 is a diagram illustrating one example of powder X-ray
diffraction patterns of a glass ceramic.
[0026] FIG. 3 is a diagram illustrating one example of powder X-ray
diffraction patterns of another glass ceramic.
[0027] FIG. 4 is a diagram illustrating one example of DSC curves
of an amorphous glass according to the present invention.
[0028] FIG. 5A and FIG. 5B illustrate a supporting glass according
to one embodiment of the present invention which is for laminating
with a semiconductor substrate; FIG. 5A is a cross-sectional view
showing the supporting glass which has not been laminated; and FIG.
5B is a cross-sectional view showing the supporting glass which has
been laminated.
[0029] FIG. 6 is a cross-sectional view of a laminated substrate
according to one embodiment of the present invention.
[0030] FIG. 7 is a drawing showing one example of TEM images of a
glass ceramic.
DESCRIPTION OF EMBODIMENTS
[0031] In this description, "-" indicating a numerical range is
used in the sense of including the numerical values set forth
before and after the "-" as a lower limit value and an upper limit
value unless otherwise indicated.
[0032] In this description, "amorphous glass" and "glass ceramic"
are collectively referred to as "glass". In this description, the
term "amorphous glass" means a glass in which no diffraction peak
indicating crystals is observed by a powder X-ray diffraction
method. A "glass ceramic" is a glass obtained by heating an
"amorphous glass" to precipitate crystals therein, and contains the
crystals.
[0033] In an examination by powder X-ray diffractometry, a sample
is examined using CuK.alpha. ray in the 20 range of
10.degree.-80.degree.; in cases when diffraction peaks have
appeared, the precipitated crystals are identified by, for example,
a Hanawalt method.
[0034] Hereinafter, the term "chemically strengthened glass" means
a glass having undergone a chemical strengthening treatment, and
the term "glass for chemical strengthening" means a glass before
being subjected to a chemical strengthening treatment.
[0035] The "base composition of a chemically strengthened glass" is
the glass composition of the glass for chemical strengthening.
Except for the case where an immoderate ion exchange treatment has
been performed, the glass composition of any portion of the
chemically strengthened glass which lies deeper than a depth of
compressive stress layer DOL is the base composition of the
chemically strengthened glass.
[0036] In this description, glass composition is expressed in mass
% on an oxide basis unless otherwise indicated, and "mass %" is
simply written as "%".
[0037] In this description, the expression "substantially contain
no" means that the content is not higher than a level of impurities
contained in raw materials or the like, i.e., the substance has not
been intentionally added. Specifically, the content is, for
example, less than 0.10%.
[0038] In this description, the term "stress profile" means a
profile showing compressive stress values using the depth from a
glass surface as a variable. An example is shown in FIG. 1. In the
stress profile, tensile stress is expressed as negative compressive
stress.
[0039] "Compressive stress value (CS)" can be determined by forming
a thin section of the glass and analyzing the thin-section sample
by a birefringence imaging system. The birefringence imaging system
birefringence stress meter is a device for measuring the magnitude
of any retardation caused by stress by using a polarization
microscope, a liquid-crystal compensator, etc. An example thereof
is birefringence imaging system Abrio-IM, manufactured by CRi,
Inc.
[0040] There are cases where CS values can be determined by
utilizing scattered-light photoelasticity. In this method, light is
caused to enter the glass through a surface thereof and the
resultant scattered light is analyzed for polarization, thereby
determining the CS. Examples of stress meters in which
scattered-light photoelasticity is utilized include scattered-light
photoelastic stress meters SLP-1000 and SLP-2000, manufactured by
Orihara Manufacturing Co., Ltd.
[0041] In this description, "depth of compressive stress layer
(DOL)" is a depth at which the compressive stress value becomes
zero. Hereinafter, surface compressive stress value is sometimes
denoted by CS.sub.0 and compressive stress value at a depth of 50 m
is sometimes denoted by CS.sub.50. The term "internal tensile
stress (CT)" means a tensile stress value at a depth corresponding
to 1/2 of a sheet thickness t.
[0042] In this description, the term "light transmittance" means an
average light transmittance of light having wavelengths ranging
from 380 nm to 780 nm. The term "haze value" is measured using a C
illuminant in accordance with JIS K3761:2000.
[0043] In this description, the color of glass ceramic is a color
determined from a transmission spectrum of a 0.7-mm-thick sample of
the glass ceramic sheet under C illuminant. The color is expressed
using either tristimulus values X, Y, and Z according to the XYZ
color system defined by JIS Z8701:1999 and the appendix thereof or
a main wavelength Md and an excitation purity Pe which are
calculated from those values.
[0044] In this description, the term "Vickers hardness" means the
Vickers hardness (HV0.1) defined in JIS R1610:2003.
[0045] "Fracture toughness value" can be measured using a DCDC
method (Acta metall. mater., Vol. 43, pp. 3453-3458, 1995).
[0046] In this description, the term "semiconductor" means not only
a semiconductor wafer of silicon, etc., or a semiconductor chip,
but also sometimes a composite structure including a chip, a wiring
layer, and a mold resin.
<Glass Ceramic>
[0047] From the standpoint of enabling a remarkable improvement in
strength by chemical strengthening, a thickness (t) of the present
glass ceramic is preferably 3 mm or less, and is more preferably 2
mm or less, 1.6 mm or less, 1.1 mm or less, 0.9 mm or less, 0.8 mm
or less, and 0.7 mm or less stepwisely. From the standpoint of
obtaining sufficient strength through a chemical strengthening
treatment, the thickness (t) is preferably 0.3 mm or more, more
preferably 0.4 mm or more, still more preferably 0.5 mm or
more.
[0048] Since the present glass ceramic has a light transmittance of
85% or more when having a thickness of 0.7 mm, use of the present
glass ceramic as the cover glasses of portable displays renders
images on the display screens easy to see. The light transmittance
is preferably 88% or more, more preferably 90% or more. The higher
the light transmittance, the more preferred. Usually, however, the
light transmittance is 91% or less. The transmittance of 90% is
comparable to that of ordinary amorphous glasses.
[0049] The haze value, in the case where the thickness is 0.7 mm,
is 1.0% or less, and is preferably 0.4% or less, more preferably
0.3% or less, still more preferably 0.2% or less, especially
preferably 0.15% or less. The smaller the haze value, the more
preferred. However, if the degree of crystallinity or the
crystal-particle size is reduced in order to reduce a haze value,
this results in a decrease in mechanical strength. From the
standpoint of attaining high mechanical strength, the haze value in
the case of a thickness of 0.7 mm is preferably 0.02% or more, more
preferably 0.03% or more.
[0050] The present glass ceramic has a Y value according to the XYZ
color system of preferably 87 or more, more preferably 88 or more,
still more preferably 89 or more, especially preferably 90 or more.
For use as cover glasses for portable displays, it is preferable
that the coloration of the glass itself is as little as possible,
from the standpoint of heightening the displayed-color
reproducibility in the case of using the glass ceramic on the
display screen side or from the standpoint of maintaining design
attractiveness in the case of using the glass ceramic on the
housing side. The present glass ceramic hence has an excitation
purity Pe of preferably 1.0 or less, more preferably 0.75 or less,
still more preferably 0.5 or less, especially preferably 0.35 or
less, most preferably 0.25 or less.
[0051] In the case where the present glass ceramic or a
strengthened glass obtained by strengthening the glass ceramic is
for use as a cover glass of a portable display, it is preferable
that this glass gives a texture and a sense of high quality
different from plastics. From this standpoint, the present glass
ceramic has a main wavelength .lamda.d of preferably 580 nm or less
and a refractive index of preferably 1.52 or more, more preferably
1.55 or more, still more preferably 1.57 or more.
[0052] The present glass ceramic is preferably a glass ceramic
containing lithium metasilicate crystals. Lithium metasilicate
crystals are expressed by Li.sub.2SiO.sub.3 and are crystals
generally giving a powder X-ray diffraction spectrum having
diffraction peaks at Bragg angles (2.theta.) of about
26.98.degree., 18.88.degree., and 33.05.degree.. FIG. 2 shows an
example of X-ray diffraction spectra of the present glass ceramic,
in which lithium metasilicate crystals are observed.
[0053] It is also preferable that the present glass ceramic is a
glass ceramic containing lithiumphosphate crystals.
Lithiumphosphate crystals are expressed by Li.sub.3PO.sub.4 and are
crystals giving a powder X-ray diffraction spectrum having
diffraction peaks at Bragg angles (2.degree.) of about
22.33.degree., 23.18.degree., and 33.93.degree.. FIG. 3 shows an
example of powder X-ray diffraction spectra of the present glass
ceramic, in which lithium metasilicate crystals and
lithiumphosphate crystals are clearly observed. A comparison
between FIG. 2 and FIG. 3 indicates that the glass ceramic of FIG.
2 also contains lithiumphosphate crystals. The precipitation of
lithiumphosphate crystals tends to enhance the chemical
durability.
[0054] The present glass ceramic may contain both lithium
metasilicate crystals and lithiumphosphate crystals.
[0055] The present glass ceramic is obtained by heating and
crystallizing an amorphous glass which will be described later.
[0056] The glass ceramic containing lithium metasilicate crystals
has a higher fracture toughness value than usual amorphous glasses
and is less apt to suffer an intense fracture even when high
compressive stress is provided by chemical strengthening. There are
cases where, in an amorphous glass in which lithium metasilicate
crystals can be precipitated, the precipitation of lithium
disilicate occurs depending on heat-treatment conditions, etc.
Lithium disilicate is expressed by Li.sub.2Si.sub.2O.sub.5 and is
crystals generally giving a powder X-ray diffraction spectrum
having diffraction peaks at Bragg angles (2.theta.) of about
24.89.degree., 23.85.degree., and 24.40.degree..
[0057] In the case where the glass ceramic contains lithium
disilicate crystals, it is preferable that the lithium disilicate
crystals have a particle size (referred to also as crystal size) of
45 nm or less, the particle size being determined using a Scherrer
equation from the widths of X-ray diffraction peaks. This is
because transparency is apt to be obtained with such lithium
disilicate crystals. The particle size thereof is more preferably
40 nm or less.
[0058] However, in cases when lithium metasilicate crystals and
lithium disilicate crystals are simultaneously contained in a glass
ceramic, this glass ceramic is prone to have reduced transparency.
It is hence preferable that the present glass ceramic does not
contain lithium disilicate. The expression "does not contain
lithium disilicate" means that the glass ceramic gives an X-ray
diffraction spectrum in which no diffraction peak of lithium
disilicate crystals is detected.
[0059] The present glass ceramic has a degree of crystallinity of
preferably 5% or more, more preferably 10% or more, still more
preferably 15% or more, especially preferably 20% or more, from the
standpoint of heightening the mechanical strength. From the
standpoint of heightening the transparency, the degree of
crystallinity thereof is preferably 70% or less, more preferably
60% or less, especially preferably 50% or less. The glass ceramic
having a low degree of crystallinity is superior in that this glass
is easy to be subjected to bending formation, etc. by heating. The
term "degree of crystallinity" as used herein, for example, a
degree of crystallinity of a glass ceramic in which lithium
metasilicate crystals and lithiumphosphate crystals have been
precipitated means a degree of crystallinity for both the lithium
metasilicate crystals and the lithiumphosphate crystals.
[0060] The degree of crystallinity can be calculated from X-ray
diffraction intensity by a Rietveld method. The Rietveld method is
described in "Handbook of Crystal Analysis" edited by the "Handbook
of Crystal Analysis" Editing Committee of the Crystallographic
Society of Japan (published by Kyoritsu Shuppan Co., Ltd., 1999,
pp. 492-499).
[0061] The average particle size of the precipitated crystals in
the present glass ceramic is preferably 80 nm or less, more
preferably 60 nm or less, still more preferably 50 nm or less,
especially preferably 40 nm or less, most preferably 30 nm or less.
The average particle size of precipitated crystals is determined
from images obtained with a transmission electron microscope (TEM).
The average particle size of precipitated crystals can be estimated
from images obtained with a scanning electron microscope (SEM).
[0062] The present glass ceramic has an average thermal expansion
coefficient at 50-350.degree. C. of preferably 90.times.10.sup.-7/C
or more, more preferably 100.times.10.sup.-7/.degree. C. or more,
still more preferably 110.times.10.sup.-7/.degree. C. or more,
especially preferably 120.times.10.sup.-7/.degree. C. or more, most
preferably 130.times.10.sup.-7/.degree. C. or more.
[0063] In case where the thermal expansion coefficient is too high,
there is a possibility that this glass might crack due to a
difference in thermal expansion during chemical strengthening. The
average thermal expansion coefficient is hence preferably
160.times.10.sup.-7/.degree. C. or less, more preferably
150.times.10.sup.-7/.degree. C. or less, still more preferably
140.times.10.sup.-7/.degree. C. or less.
[0064] The glass ceramic having such a thermal expansion
coefficient is suitable for use as a supporting substrate for
semiconductor packages including resin components in large
proportions.
[0065] The present glass ceramic has a high hardness since it
contains crystals. Because of this, the glass ceramic is less apt
to receive scratches and has excellent wear resistance. The Vickers
hardness thereof is preferably 600 or more, more preferably 700 or
more, still more preferably 730 or more, especially preferably 750
or more, most preferably 780 or more, from the standpoint of
enhancing the wear resistance.
[0066] Too high hardness result in poor workability. The Vickers
hardness of the present glass ceramic is hence preferably 1,100 or
less, more preferably 1,050 or less, still more preferably 1,000 or
less.
[0067] The present glass ceramic has a Young's modulus of
preferably 85 GPa or more, more preferably 90 GPa or more, still
more preferably 95 GPa or more, especially preferably 100 GPa or
more, from the standpoint of inhibiting strengthening warpage
during chemical strengthening. There are cases where the present
glass ceramic is polished before being used. From the standpoint of
facilitating polishing, the Young's modulus thereof is preferably
130 GPa or less, more preferably 125 GPa or less, still more
preferably 120 GPa or less.
[0068] The present glass ceramic has a fracture toughness value of
0.8 MPam.sup.1/2 or more, more preferably 0.85 MPam.sup.1/2 or
more, still more preferably 0.9 MPam.sup.1/2 or more. This is
because the glass ceramic having such a fracture toughness value,
after having been chemically strengthened, is less apt to scatter
fragments upon breakage.
[0069] The present glass ceramic preferably has a relative
permittivity P of 8.0 or less at a frequency of 10 GHz. This is
because the glass ceramic having such a relative permittivity
brings about satisfactory communication efficiency when used in
radio communication appliances for high-frequency communication.
The relative permittivity F of the present glass ceramic at a
frequency of 10 GHz is more preferably 7.6 or less, still more
preferably 7.3 or less. The F thereof is usually 3.7 or more.
[0070] The present glass ceramic has a lower dielectric loss
tangent tan .delta. at a frequency of 10 GHz than the glass which
has not undergone crystallization; the present glass ceramic is
hence preferred. The reduced dielectric loss tangent is owing to
the fact that crystals having a lower tan .delta. than the glass
have precipitated in the glass and this precipitation has reduced
the tan .delta. of the glass as a whole. The tan .delta. thereof is
preferably 0.014 or less because the present glass ceramic having
such a value of tan .delta. brings about satisfactory communication
efficiency when used in radio communication appliances for
high-frequency communication. The dielectric loss tangent tan
.delta. of the present glass ceramic at a frequency of 10 GHz is
more preferably 0.012 or less, still more preferably 0.010 or less,
yet still more preferably 0.008 or less. The tan .delta. thereof is
usually 0.002 or more.
[0071] The present glass ceramic has the same glass composition as
the amorphous glass which has not undergone crystallization yet,
and thus the glass composition thereof will be explained later in
the section "Amorphous Glass".
<Chemically Strengthened Glass>
[0072] The chemically strengthened glass (hereinafter sometimes
referred to as "the present strengthened glass") obtained by
chemically strengthening the present glass ceramic preferably has a
surface compressive stress value CS.sub.0 of 600 MPa or more. This
is because the present strengthened glass having such a surface
compressive stress value is less apt to crack when deformed by
deflection, etc. The surface compressive stress value of the
present strengthened glass is more preferably 800 MPa or more.
[0073] The present strengthened glass has a depth of compressive
stress layer DOL of preferably 80 .mu.m or more. This is because
the strengthened glass is less apt to crack even when a surface
thereof receives scratches. The DOL thereof is preferably 100 m or
more.
[0074] The larger the compressive stress value CS.sub.50 at a depth
of compressive stress layer of 50 .mu.m, the higher the strength in
the drop-onto-sandpaper test shown below, i.e., drop strength. The
CS.sub.50 thereof is preferably 80 MPa or more, more preferably 100
MPa or more, still more preferably 120 MPa or more, especially
preferably 140 MPa or more.
(Drop-onto-Sandpaper Test)
[0075] A glass sheet (120 mm.times.60 mm.times.0.7 mm) to be
evaluated is taken as a cover glass for a smartphone and attached
to a housing as an imitation of the smartphone, and this assembly
is dropped onto the surface of flat SiC #180 sandpaper. The total
mass of the glass sheet and the housing is adjusted to about 140
g.
[0076] The test is initiated with a height of 30 cm, and in cases
when the chemically strengthened glass sheet has not cracked, this
assembly is then dropped from a height increased by 10 cm. The
dropping is thus repeated and the height [unit: cm] which has
resulted in cracking is recorded. This test as one set is repeated
to conduct 10 sets, and an average of the heights which have
resulted in cracking is taken as "drop height".
[0077] The present strengthened glass preferably has a drop height
in the drop-onto-sandpaper test of 80 cm or more.
[0078] It is preferable that the present strengthened glass has an
internal tensile stress (CT) of 110 MPa or less, because this
chemically strengthened glass having such a CT is inhibited from
scattering fragments upon breakage. The CT thereof is more
preferably 100 MPa or less, still more preferably 90 MPa or less.
Meanwhile, a reduction in CT tends to reduce the surface
compressive stress, making it difficult to obtain sufficient
strength. Consequently, the CT thereof is preferably 50 MPa or
more, more preferably 55 MPa or more, still more preferably 60 MPa
or more.
[0079] The present strengthened glass has a four-point bending
strength of preferably 500 MPa or more, more preferably 550 MPa or
more, still more preferably 600 MPa or more. The four-point bending
strength is measured using a test piece of 40 mm.times.5
mm.times.0.8 mm under the conditions of a lower span of 30 mm, an
upper span of 10 mm, and a cross head speed of 0.5 mm/min. An
average value for 10 test pieces is taken as the four-point bending
strength.
[0080] A higher Vickers hardness of the present strengthened glass
tends to become higher than the unstrengthened glass, through the
chemical strengthening treatment. This is thought to be because the
ion exchange between small ions in crystals and large ions in the
molten salt has produced compressive stress in the crystals.
[0081] The Vickers hardness of the present strengthened glass is
preferably 720 or more, more preferably 740 or more, still more
preferably 780 or more. The Vickers hardness of the present
strengthened glass is usually 950 or less.
[0082] In general, the glass transition points of glass ceramics
are higher than the glass transition points of amorphous glasses
having the same glass composition. From the standpoint of
inhibiting stress relaxation from occurring during chemical
strengthening treatments, the glass transition point of the glass
ceramic is preferably 500.degree. C. or more, more preferably
530.degree. C. or more, still more preferably 550.degree. C. or
more, especially preferably 570.degree. C. or more. From the
standpoint of subjecting the glass ceramic to, for example, bending
with heating, the glass transition point of the glass ceramic is
preferably 850.degree. C. or less, more preferably 800.degree. C.
or less, still more preferably 750.degree. C. or less, especially
preferably 700.degree. C. or less.
[0083] The difference .DELTA.Tg between the glass transition point
of the present glass ceramic and the glass transition point of an
amorphous glass having the same glass composition is preferably
200.degree. C. or less, more preferably 195.degree. C. or less,
still more preferably 190.degree. C. or less. Glass ceramics having
a small .DELTA.Tg are easy to process by, for example, bending with
heating.
[0084] The present strengthened glass has the same visible-light
transmittance, haze value, and high-frequency characteristics as
the present glass ceramic. Explanations thereon are hence
omitted.
[0085] The present strengthened glass as a whole has approximately
the same composition as the glass ceramic which has not been
strengthened, except for the case where the strengthened glass has
undergone an immoderate ion exchange treatment. In particular, the
portion lying most deeply from the glass surfaces has the same
composition as the glass ceramic which has not been strengthened,
except for the case where the strengthened glass has undergone an
immoderate ion exchange treatment.
<Amorphous Glass>
[0086] The amorphous glass according to the present invention
preferably includes, in mass % on an oxide basis, 45-70% of
SiO.sub.2, 1-15% of Al.sub.2O.sub.3, 10-25% of Li.sub.2O, 0-12% of
P.sub.2O.sub.5, 0-15% of ZrO.sub.2, 0-10% of Na.sub.2O, 0-5% of
K.sub.2O, and 0-6% of Y.sub.2O.sub.3.
[0087] This glass composition is explained below.
[0088] In the present amorphous glass, SiO.sub.2 is a component
forming a network structure of the glass. In addition, SiO.sub.2 is
a component enhancing the chemical durability and is a constituent
component of lithium metasilicate as precipitated crystals. The
content of SiO.sub.2 is preferably 45% or more. The content of
SiO.sub.2 is more preferably 48% or more, still more preferably 50%
or more, especially preferably 52% or more, extremely preferably
54% or more. Meanwhile, from the standpoint of enhancing
meltability, the content of SiO.sub.2 is preferably 70% or less,
more preferably 68% or less, still more preferably 66% or less,
especially preferably 64% or less.
[0089] Al.sub.2O.sub.3 is a component increasing the surface
compressive stress to be generated by chemical strengthening, and
is essential. The content of Al.sub.2O.sub.3 is preferably 1% or
more. The content of Al.sub.2O.sub.3 is more preferably 2% or more,
still more preferably 4% or more, especially preferably 6% or more,
extremely preferably 8% or more. Meanwhile, from the standpoint of
preventing the glass from having too high a devitrification
temperature, the content of Al.sub.2O.sub.3 is preferably 15% or
less, more preferably 12% or less, still more preferably 10% or
less, especially preferably 8% or less, most preferably 6% or
less.
[0090] Li.sub.2O is a component forming surface compressive stress
through ion exchange, is a constituent component of lithium
metasilicate crystals, and is essential. The content of Li.sub.2O
is preferably 10% or more, more preferably 14% or more, still more
preferably 16% or more, especially preferably 18% or more.
Meanwhile, from the standpoint of stabilizing the glass, the
content of Li.sub.2O is preferably 25% or less, more preferably 22%
or less, still more preferably 20% or less.
[0091] Na.sub.2O is a component improving the meltability of the
glass. Although Na.sub.2O is not essential, the content thereof is
preferably 0.5% or more, more preferably 1% or more, especially
preferably 2% or more. In case where the content of Na.sub.2O is
too high, lithium metasilicate crystals are less apt to be
precipitated or the glass has a reduced chemical strengthening
property. The content of Na.sub.2O hence is preferably 10% or less,
more preferably 9% or less, still more preferably 8% or less,
especially preferably 7% or less.
[0092] K.sub.2O is a component lowering the melting temperature of
the glass like Na.sub.2O, and may be contained. In cases when
K.sub.2O is contained, the content thereof is preferably 0.5% or
more, more preferably 1% or more, still more preferably 1.5% or
more, especially preferably 2% or more. Too high K.sub.2O contents
result in a decrease in chemical strengthening property or a
decrease in chemical durability. The content of K.sub.2O hence is
preferably 5% or less, more preferably 4% or less, still more
preferably 3% or less, especially preferably 2% or less.
[0093] The total content of Na.sub.2O and K.sub.2O, i.e.,
Na.sub.2O+K.sub.2O, is preferably 1% or more, more preferably 2% or
more.
[0094] In cases when the sum of Li.sub.2O, Na.sub.2O, and K.sub.2O,
i.e., Li.sub.2O+Na.sub.2O+K.sub.2O, is expressed by R.sub.2O, it is
preferable that K.sub.2O/R.sub.2O is 0.2 or less. This is because
such value of the ratio can enhance the chemical strengthening
properties and heighten the chemical durability. That ratio is more
preferably 0.15 or less, still more preferably 0.10 or less.
[0095] R.sub.2O is 10% or more, preferably 15% or more, more
preferably 20% or more. Meanwhile, R.sub.2O is 29% or less,
preferably 26% or less.
[0096] P.sub.2O.sub.5, although not essential, has the effect of
promoting phase separation in the glass to accelerate
crystallization and may be contained. In cases when P.sub.2O.sub.5
is contained, the content thereof is preferably 0.5% or more, more
preferably 2% or more, still more preferably 4% or more, especially
preferably 5% or more, extremely preferably 6% or more. Meanwhile,
too high P.sub.2O.sub.5 contents not only make the glass prone to
undergo phase separation during melting but also result in a
considerable decrease in acid resistance. The content of
P.sub.2O.sub.5 is preferably 12% or less, more preferably 10% or
less, still more preferably 8% or less, especially preferably 7% or
less.
[0097] ZrO.sub.2 is a component capable of constituting crystal
nuclei in a crystallization treatment and may be contained. The
content of ZrO.sub.2 is preferably 1% or more, more preferably 2%
or more, still more preferably 4% or more, especially preferably 6%
or more, most preferably 7% or more. Meanwhile, from the standpoint
of inhibiting devitrification during melting, the content of
ZrO.sub.2 is preferably 15% or less, more preferably 14% or less,
still more preferably 12% or less, especially preferably 11% or
less.
[0098] In cases when the sum of Li.sub.2O, Na.sub.2O, and K.sub.2O,
i.e., Li.sub.2O+Na.sub.2O+K.sub.2O, is expressed by R.sub.2O, then
ZrO.sub.2/R.sub.2O is preferably 0.10 or more, more preferably 0.30
or more, from the standpoint of enhancing the chemical durability.
From the standpoint of heightening the transparency after
crystallization, ZrO.sub.2/R.sub.2O is preferably 0.80 or less,
more preferably 0.60 or less.
[0099] TiO.sub.2 is a component capable of constituting crystal
nuclei in a crystallization treatment and may be contained.
Although TiO.sub.2 is not essential, the content thereof, in cases
when TiO.sub.2 is contained, is preferably 0.5% or more, more
preferably 1% or more, still more preferably 2% or more, especially
preferably 3% or more, most preferably 4% or more. Meanwhile, from
the standpoint of inhibiting devitrification during melting, the
content of TiO.sub.2 is preferably 10% or less, more preferably 8%
or less, still more preferably 6% or less.
[0100] SnO.sub.2 serves to accelerate the formation of crystal
nuclei and may be contained. Although SnO.sub.2 is not essential,
the content thereof, in cases when SnO.sub.2 is contained, is
preferably 0.5% or more, more preferably 1% or more, still more
preferably 1.5% or more, especially preferably 2% or more.
Meanwhile, from the standpoint of inhibiting devitrification during
melting, the content of SnO.sub.2 is preferably 6% or less, more
preferably 5% or less, still more preferably 4% or less, especially
preferably 3% or less.
[0101] Y.sub.2O.sub.3 is a component which renders the chemically
strengthened glass less apt to scatter fragments upon breakage, and
may be contained. The content of Y.sub.2O.sub.3 is preferably 1% or
more, more preferably 1.5% or more, still more preferably 2% or
more, especially preferably 2.5% or more, extremely preferably 3%
or more. Meanwhile, from the standpoint of inhibiting
devitrification during melting, the content of Y.sub.2O.sub.3 is
preferably 5% or less, more preferably 4% or less.
[0102] B.sub.2O.sub.3, although not essential, is a component which
improves the chipping resistance of the glass for chemical
strengthening or the chemically strengthened glass and improves the
meltability, and may be contained. The content of B.sub.2O.sub.3,
in cases when it is contained, is preferably 0.5% or more, more
preferably 1% or more, still more preferably 2% or more, from the
standpoint of improving the meltability. Meanwhile, in case where
the content of B.sub.2O.sub.3 exceeds 5%, striae during melting or
phase separation tends to occur to lower the quality of the glass
for chemical strengthening. The content thereof is hence preferably
5% or less. The content of B.sub.2O.sub.3 is more preferably 4% or
less, still more preferably 3% or less, especially preferably 2% or
less.
[0103] BaO, SrO, MgO, CaO, and ZnO are components improving the
meltability of the glass and may be contained. In cases when these
components are contained, the sum of BaO, SrO, MgO, CaO, and ZnO,
i.e., BaO+SrO+MgO+CaO+ZnO, is preferably 0.5% or more, more
preferably 1% or more, still more preferably 1.5% or more,
especially preferably 2% or more. Meanwhile, the content of
BaO+SrO+MgO+CaO+ZnO is preferably 8% or less, more preferably 6% or
less, still more preferably 5% or less, especially preferably 4% or
less, as ion exchange rate decreases.
[0104] Of those components, BaO, SrO, and ZnO may be contained in
order to heighten the refractive index of the residual glass to a
value close to that of a precipitated-crystal phase and thereby
improve a light transmittance of a glass ceramic and reduce a haze
value. In this case, the total content of BaO+SrO+ZnO is preferably
0.3% or more, more preferably 0.5% or more, still more preferably
0.7% or more, especially preferably 1% or more. Meanwhile, there
are cases where these components reduce the ion exchange rate. From
the standpoint of imparting satisfactory chemical strengthening
properties, BaO+SrO+ZnO is preferably 2.5% or less, more preferably
2% or less, still more preferably 1.7% or less, especially
preferably 1.5% or less.
[0105] La.sub.2O.sub.3, Nb.sub.2O.sub.5, and Ta.sub.2O.sub.5 are
all components which render the chemically strengthened glass less
apt to scatter fragments upon breakage, and may be contained in
order to heighten the refractive index.
[0106] The total content of La.sub.2O.sub.3, Nb.sub.2O.sub.5, and
Ta.sub.2O.sub.5, i.e.,
La.sub.2O.sub.3+Nb.sub.2O.sub.5+Ta.sub.2O.sub.5, is preferably 0.5%
or more, more preferably 1% or more, still more preferably 1.5% or
more, especially preferably 2% or more. From the standpoint of
rendering the glass less apt to devitrify during melting,
La.sub.2O.sub.3+Nb.sub.2O.sub.5+Ta.sub.2O.sub.5 is preferably 4% or
less, more preferably 3% or less, still more preferably 2% or less,
especially preferably 1% or less.
[0107] CeO.sub.2 may be contained. CeO.sub.2 has the effect of
oxidizing the glass and sometimes inhibits coloration. The content
of CeO.sub.2, in cases when it is contained, is preferably 0.03% or
more, more preferably 0.05% or more, still more preferably 0.07% or
more. In the case of using CeO.sub.2 as an oxidizing agent, the
content of CeO.sub.2 is preferably 1.5% or less, more preferably
1.0% or less, from the standpoint of heightening the
transparency.
[0108] In the case where the strengthened glass is to be used as a
colored glass, a coloring component may be added so long as the
addition thereof does not inhibit the attainment of the desired
chemical strengthening properties. Suitable examples of the
coloring components include Co.sub.3O.sub.4, MnO.sub.2,
Fe.sub.2O.sub.3, NiO, CuO, Cr.sub.2O.sub.3, V.sub.2O.sub.5,
Bi.sub.2O.sub.3, SeO.sub.2, Er.sub.2O.sub.3, and
Nd.sub.2O.sub.3.
[0109] The content of such coloring components is preferably 1% or
less in total. In the case where the glass is desired to have a
higher visible-light transmittance, it is preferable that those
components are not substantially contained.
[0110] SO.sub.3, a chloride, a fluoride, etc. may be suitably
contained as a refining agent for use in glass melting. It is
preferable that As.sub.2O.sub.3 is not contained. In cases when
Sb.sub.2O.sub.3 is contained, the content thereof is preferably
0.3% or less, more preferably 0.1% or less. It is most preferable
that no Sb.sub.2O.sub.3 is contained.
[0111] The present amorphous glass has a glass transition point Tg
of preferably 390.degree. C. or more, more preferably 410.degree.
C. or more, still more preferably 420.degree. C. or more. In cases
when the glass transition point Tg thereof is high, stress
relaxation is less apt to occur during chemical strengthening and,
hence, high strength is apt to be obtained. Meanwhile, too high a
Tg renders glass forming, etc. difficult. Consequently, the Tg
thereof is preferably 650.degree. C. or less, more preferably
600.degree. C. or less.
[0112] The present amorphous glass has a thermal expansion
coefficient of preferably 90.times.10.sup.7/.degree. C. or more,
more preferably 100.times.10.sup.7/.degree. C. or more, still more
preferably 110.times.10.sup.7/.degree. C. or more. Meanwhile, too
high thermal expansion coefficients make the glass prone to crack
during forming. Consequently, the thermal expansion coefficient
thereof is preferably 150.times.10.sup.-7/.degree. C. or less, more
preferably 140.times.10.sup.-7/.degree. C. or less. In case where
there is a large difference in thermal expansion coefficient
between the amorphous glass and lithium metasilicate crystals,
cracking due to the difference in thermal expansion coefficient is
prone to occur during crystallization.
[0113] In cases when the present amorphous glass is pulverized and
examined with a differential scanning calorimeter, the glass gives
a DSC curve in which the difference (Tc-Tg) between a glass
transition point (Tg.sub.DSC) determined from the DSC curve and the
temperature (Tc) corresponding to a crystallization peak appearing
in the lowest-temperature range in the DSC curve is preferably
80.degree. C. or more, more preferably 85.degree. C. or more, still
more preferably 90.degree. C. or more, especially preferably
95.degree. C. or more. In cases when (Tc-Tg) is large, it is easy
to process the glass ceramic by bending with reheating, etc.
(Tc-Tg) is preferably 150.degree. C. or less, more preferably
140.degree. C. or less.
[0114] FIG. 4 shows one example of DSC curves of an amorphous glass
according to the present invention. There are cases where the
Tg.sub.DSC shown in FIG. 4 does not coincide with a glass
transition point (Tg) determined from a thermal expansion curve. In
addition, since the glass is examined after having been pulverized,
a large measurement error is prone to occur. However, for
evaluating a relationship with crystallization peak temperature, it
is appropriate to use the Tg.sub.DSC determined by the same DSC
examination rather than the Tg determined from a thermal expansion
curve.
[0115] The present amorphous glass has a Young's modulus of
preferably 75 GPa or more, more preferably 80 GPa or more, still
more preferably 85 GPa or more.
[0116] The Vickers hardness thereof is preferably 500 or more, more
preferably 550 or more.
<Production Method of Chemically Strengthened Glass>
[0117] The chemically strengthened glass of the present invention
is produced by heat-treating the amorphous glass to obtain a glass
ceramic and then subjecting the obtained glass ceramic to a
chemical strengthening treatment.
(Production of Amorphous Glass)
[0118] The amorphous glass can be produced, for example, by the
following method. Note that the following production method is an
example of producing a sheet-shaped chemically strengthened
glass.
[0119] Glass raw materials are mixed so as to obtain a glass having
a preferred composition, and the mixture is heated and melted in a
glass melting furnace. Thereafter, the molten glass is homogenized
by bubbling, stirring, addition of a refining agent, etc.,
subsequently formed into a glass sheet with a given thickness by a
known forming method, and annealed. Alternatively, use may be made
of a method in which the molten glass is formed into a block and
the block is annealed and then cut into a sheet form.
[0120] Examples of methods for forming a sheet-shaped glass include
a float process, a press process, a fusion process, and a downdraw
process. Particularly in the case of producing a large-sized glass
sheet, a float process is preferred. In addition, continuous
forming methods other than the float process, such as a fusion
process and a downdraw process are also preferred.
(Crystallization Treatment)
[0121] A glass ceramic is obtained by heat-treating the amorphous
glass obtained by the procedure above.
[0122] The heat treatment is preferably a two-step heat treatment
in which the amorphous glass is heated from room temperature to a
first treatment temperature, held at this temperature for a certain
time period, and then held for a certain time period at a second
treatment temperature which is higher than the first treatment
temperature.
[0123] In the case of performing the two-step heat treatment, the
first treatment temperature is preferably in a temperature range
where the glass composition has a high crystal nucleation rate and
the second treatment temperature is preferably in a temperature
range where the glass composition has a high crystal growth rate.
It is preferable that the period of holding at the first treatment
temperature is long enough to produce a sufficient number of
crystal nuclei. The production of a large number of crystal nuclei
results in crystals having small size to yield a glass ceramic
having high transparency.
[0124] The first treatment temperature is, for example,
450-700.degree. C. and the second treatment temperature is, for
example, 600-800.degree. C. The glass is held at the first
treatment temperature for 1 to 6 hours and then held at the second
treatment temperature for 1 to 6 hours.
[0125] The glass ceramic obtained by the procedure above is ground
and polished as necessary to form a glass ceramic sheet. In the
case where the glass ceramic sheet is to be cut into a given shape
and size or to be chamfered, it is preferred to perform the cutting
or chamfering before giving a chemical strengthening treatment to
the glass ceramic sheet, as a compressive stress layer is formed
also in the edge faces by the later chemical strengthening
treatment.
(Chemical Strengthening Treatment)
[0126] The chemical strengthening treatment is a treatment in which
a glass is brought into contact with a metal salt by, for example,
a method of immersing the glass in a melt of the metal salt (e.g.,
potassium nitrate) containing metal ions having a large ionic
radius (typically, Na ions or K ions), thereby replacing metal ions
having a small ionic radius (typically, Na ions or Li ions)
contained in the glass with metal ions having a large ionic radius
(typically, Na ions or K ions for replacing Li ions; K ions for
replacing Na ions).
[0127] From the standpoint of heightening the rate of chemical
strengthening treatment, it is preferred to use "Li--Na exchange"
in which Li ions in the glass are replaced with Na ions. From the
standpoint of forming higher compressive stress by ion exchange, it
is preferred to use "Na--K exchange" in which Na ions in the glass
are replaced with K ions.
[0128] Examples of the molten salt for performing the chemical
strengthening treatment include nitrates, sulfates, carbonates, and
chlorides. Among these, examples of the nitrates include lithium
nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and
silver nitrate. Examples of the sulfates include lithium sulfate,
sodium sulfate, potassium sulfate, cesium sulfate, and silver
sulfate. Examples of the carbonates include lithium carbonate,
sodium carbonate, and potassium carbonate. Examples of the
chlorides include lithium chloride, sodium chloride, potassium
chloride, cesium chloride, and silver chloride. One of these molten
salts may be used alone, or two or more thereof may be used in
combination.
[0129] As for the treatment conditions for the chemical
strengthening treatment, time, temperature or the like may be
appropriately selected while taking account of the glass
composition, the kind of molten salt, etc.
[0130] The present strengthened glass is preferably obtained, for
example, by the following two-step chemical strengthening
treatment.
[0131] First, the present glass ceramic is immersed for about
0.1-10 hours in an Na-ion-containing metal salt (e.g., sodium
nitrate) having a temperature of about 350-500.degree. C. This
causes ion exchange between Li ions contained in the glass ceramic
and Na ions contained in the metal salt, and thus a compressive
stress layer having a surface compressive stress value of, for
example, 200 MPa or more and a maximum depth of compressive stress
layer of, for example, 80 .mu.m or more can be formed.
[0132] Next, the glass is immersed for about 0.1-10 hours in a
K-ion-containing metal salt (e.g., potassium nitrate) having a
temperature of about 350-500.degree. C. This produces high
compressive stress in the compressive stress layer formed in the
previous treatment, in a portion, for example, within a depth of
about 10 .mu.m. According to such a two-step treatment, a favorable
stress profile with a surface compressive stress value of 500 MPa
or more is apt to be obtained.
[0133] Meanwhile, in a case where the surface compressive stress
value exceeds 1,000 MPa, it is difficult to obtain a large DOL
while maintaining a low CT. The surface compressive stress value is
preferably 900 MPa or less, more preferably 700 MPa or less, still
more preferably 600 MPa or less.
[0134] A method may be used in which the glass is first immersed in
the Na-ion-containing metal salt, subsequently held in the air at
350-500.degree. C. for 1-5 hours, and then immersed in the
K-ion-containing metal salt. The holding temperature is preferably
425-475.degree. C., more preferably 440-460.degree. C.
[0135] By holding the glass in the air at such a high temperature,
the Na ions which have been introduced into the glass from the
metal salt by the first treatment are thermally diffused in the
glass to form a more favorable stress profile and thereby heighten
the drop strength to asphalt.
[0136] Use may also be made of a method in which the glass is
immersed in the Na-ion-containing metal salt and is then immersed
for 0.1-20 hours in a metal salt containing both Na ions and Li
ions (e.g., a mixed salt of sodium nitrate and lithium nitrate)
having a temperature of 350-500.degree. C., instead of being held
in the air.
[0137] By immersing the glass in the metal salt containing Na ions
and Li ions, ion exchange is caused between Na ions contained in
the glass and Li ions contained in the metal salt to form a more
favorable stress profile and thereby heighten the drop strength to
asphalt.
[0138] From the standpoint of enhancing the drop strength to
asphalt, the compressive stress value CS50 at a depth of 50 m is
preferably 100 MPa or more, more preferably 140 MPa or more, still
more preferably 160 MPa or more.
[0139] In the case of performing such a two-step or three-step
strengthening treatment, the total treatment time is preferably 10
hours or less, more preferably 5 hours or less, still more
preferably 3 hours or less, from the standpoint of production
efficiency. Meanwhile, from the standpoint of obtaining a desired
stress profile, the total treatment time needs to be 0.5 hours or
more and is more preferably 1 hour or more.
[0140] The present strengthened glass is useful not only as the
semiconductor-supporting substrate which will be described later
but also as a cover glass for use in electronic appliances
including mobile devices such as cell phones and smartphones. The
present strengthened glass is useful also as the cover glasses of
electronic appliances not intended to be portable, such as
televisions, personal computers, and touch panels, and as wall
surfaces of elevators or wall surfaces of houses, buildings, and
the like (entire-wall displays). Furthermore, the present
strengthened glass is useful as building materials such as window
glasses, table tops, interior materials for motor vehicles,
airplanes, etc., and cover glasses for these, and as housings
having a curved surface shape, etc.
[0141] Since the present strengthened glass has satisfactory
high-frequency characteristics, it is suitable for use as the cover
glasses of appliances for high-frequency communication.
<Semiconductor-Supporting Substrate>
[0142] The semiconductor-supporting substrate (hereinafter also
referred to as "supporting glass") of the present invention is
explained. The semiconductor-supporting substrate of the present
invention includes the glass ceramic of the present invention. From
the standpoint of attaining higher strength, it is more preferable
that the semiconductor-supporting substrate includes the
strengthened glass of the present invention.
[0143] Since the present glass ceramic or the present strengthened
glass has a high thermal expansion coefficient, these are suitable
as a supporting substrate for fan-out packaging. In fan-out
packaging, packages having various average thermal expansion
coefficients are formed depending on proportions of a semiconductor
chip and a resin component. However, there are nowadays cases where
molding resins are required to have higher flowability to diminish
filling failures and, hence, packages having a large resin
component proportion and a high average thermal expansion
coefficient are frequently used.
[0144] FIG. 5A and FIG. 5B are examples of cross-sectional views of
a supporting glass for laminating to semiconductor substrates. The
supporting glass G1 shown in FIG. 5A is laminated to a
semiconductor substrate 10 at a temperature of, for example,
200-400.degree. C. through a release layer 20 (which may function
as a bonding layer), thereby obtaining the laminated substrate 30
shown in FIG. 5B. As the semiconductor substrate 10, use is made,
for example, of a full-size semiconductor wafer, a semiconductor
chip, a substrate including a semiconductor chip molded with a
resin, or a wafer on which elements have been formed. The release
layer 20 is, for example, a resin withstanding temperatures of
200-400.degree. C.
[0145] The present supporting substrate is used in applications
where it is laminated to a semiconductor substrate. For example,
the present supporting substrate is used as a supporting glass for
fan-out wafer-level packaging, a supporting glass for image
sensors, such as MEMSs, CMOSs, and CISs, in which a reduction in
element size by wafer-level packaging is effective, a supporting
glass having through-holes (glass interposer; GIP), and a support
glass for semiconductor back grinding. The present supporting glass
is especially suitable as a supporting glass for fan-out
wafer-level and panel-level packaging.
[0146] FIG. 6 shows one example of cross-sectional views of a
laminated substrate in which the present supporting glass is used
as a supporting substrate for fan-out wafer-level packaging.
[0147] In fan-out wafer-level packaging, semiconductor substrates
40 are laminated to a supporting glass G2 at a temperature of, for
example, 200-400.degree. C., through a release layer 50 of resin or
the like (which may function as a bonding layer). Furthermore, the
semiconductor substrates 40 are embedded with a resin 60, thereby
obtaining a laminated substrate 70. Thereafter, the release layer
50 is irradiated with a laser such as ultraviolet light through the
supporting glass G2, thereby removing the supporting glass G2 from
the semiconductor substrates 40 embedded in the resin 60. The
supporting glass G2 is reusable. The semiconductor substrates 40
embedded in the resin 60 are wired with copper wires, etc. Wiring
with copper wires or the like may be given beforehand to the
surface of the release layer. A substrate including semiconductor
chips embedded in a resin 60 may be used as a semiconductor
substrate.
[0148] The present supporting substrate has a high light
transmittance and, hence, a laser of high-energy visible light or a
laser of ultraviolet light can be effectively utilized as the laser
for use in the removal.
Examples
[0149] The present invention is described below by referring to
Examples, but the present invention is not limited thereto.
<Preparation and Evaluation of Amorphous Glasses>
[0150] Glass raw materials were mixed so as to result in each of
the glass compositions shown in mass % on an oxide basis in Tables
1 and 2, and weighed so as to yield 800 g of a glass. Subsequently,
the mixed glass raw materials were put in a platinum crucible and
this crucible was introduced into an electric furnace at
1,600.degree. C., in which the mixture was melted, degassed, and
homogenized for about 5 hours.
[0151] The obtained molten glass was cast into a mold, held for 1
hour at a temperature of the glass transition point, and then
cooled to room temperature at a rate of 0.5.degree. C./min to
obtain a glass block. Some of the obtained block was used to
evaluate the amorphous glass for glass transition point, thermal
expansion coefficient, specific gravity, Young's modulus,
refractive index, and Vickers hardness. The results thereof are
shown in Tables 1 and 2. In the tables, each blank indicates that
the property was not evaluated.
[0152] G1 to G22 and G26 to G33 are examples of amorphous glasses
according to the present invention, and G23 to G25 and G34 are
comparative examples. G34 had suffered phase separation during the
melting operation and was unable to be evaluated.
(Glass Transition Point, Thermal Expansion Coefficient)
[0153] In accordance with JIS R1618:2002, a thermal expansion curve
was obtained using a thermal dilatometer (TD5000SA, manufactured by
Bruker AXS GmbH) under the conditions of a heating rate of
10.degree. C./min, and a glass transition point Tg [unit: .degree.
C.] and a thermal expansion coefficient were determined from the
obtained thermal expansion curve.
(Specific Gravity)
[0154] The specific gravity was measured by the Archimedes
method.
(Young's Modulus)
[0155] The Young's modulus was measured by an ultrasonic
method.
(Vickers Hardness)
[0156] The Vickers hardness was measured by pressing an indenter
under a load of 100 gf for 15 seconds using a Shimadzu
micro-Vickers hardness tester (HTMV-2, manufactured by Shimadzu
Corporation).
(DSC Examination)
[0157] A glass was pulverized using an agate mortar, and about 80
mg of the powder was put in a platinum cell and examined for DSC
with a differential scanning calorimeter (DSC3300SA, manufactured
by Bruker GmbH) while being heated from room temperature to
1,100.degree. C. at a heating rate of 10.degree. C./min. A glass
transition point Tg.sub.DSC, a temperature Tc corresponding to a
first crystallization peak, and the difference Tc-Tg between these
temperatures were determined. FIG. 4 shows the results of the
examination of G13.
(High-Frequency Characteristics)
[0158] The obtained glass block was processed into a sheet shape
having a thickness of 0.5 mm and examined with a network analyzer
for relative permittivity c and dielectric loss tangent tan .delta.
at 10 GHz by a split-post dielectric resonance method (SPDR
method). The results thereof are shown in Table 1. After the
crystallization treatment which will be described later, the glass
was examined in the same manner; the results of the examination
made after the crystallization treatment are shown in Table 3.
TABLE-US-00001 TABLE 1 G1 G2 G3 G4 G5 G6 G7 G8 SiO.sub.2 59.5 59.9
57.7 55.8 54.9 55.3 55.2 53.8 Al.sub.2O.sub.3 2.0 2.0 2.0 2.0 2.0
2.0 5.5 7.2 Li.sub.2O 18.4 18.5 18.5 18.3 18.3 18.4 18.2 18.1
Na.sub.2O 2.0 3.4 5.6 4.0 5.6 7.3 4.4 4.4 K.sub.2O 2.0 0.0 0.0 4.1
3.4 0.9 0.8 0.8 MgO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 CaO 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 P.sub.2O.sub.5 5.9 6.0 6.0 5.9 5.9 6.0 5.9 5.8
ZrO.sub.2 10.1 10.1 10.1 10.0 10.0 10.1 10.0 9.9 Y.sub.2O.sub.3 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 TiO.sub.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 B.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SrO 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 SnO.sub.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Specific gravity 2.52 2.53 2.53 2.54 2.54 2.54 2.55 2.55 Tg
(.degree. C.) 453 456 443 439 430 428 450 460 Thermal expansion 125
127 131 137 141 144 131 127 coefficient (.times.10.sup.-7/.degree.
C.) Tc (.degree. C.) 589 586 576 563 564 Tg.sub.DSC (.degree. C.)
470 469 452 460 467 Tc-Tg (.degree. C.) 119 117 124 103 97 Young's
modulus (GPa) 87 88 89 89 90 89 90 91 Vickers hardness 604 599 559
550 561 551 540 568 Fracture toughness value 0.77 Relative
permittivity 8.6 Dielectric loss tangent 0.017 G9 G10 G11 G12 G13
G14 G15 G16 SiO.sub.2 56.6 54.0 55.2 52.6 51.2 57.0 62.3 51.1
Al.sub.2O.sub.3 5.4 5.3 7.2 7.0 8.7 2.0 2.1 5.9 Li.sub.2O 18.1 17.6
18.0 17.5 17.4 18.1 18.7 22.0 Na.sub.2O 2.0 2.0 2.0 1.9 1.9 2.0 2.1
1.5 K.sub.2O 2.0 1.9 2.0 1.9 1.9 2.0 2.1 1.5 MgO 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 CaO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 P.sub.2O.sub.5
5.9 5.7 5.8 5.7 5.6 5.8 6.1 5.9 ZrO.sub.2 9.9 9.6 9.9 9.6 9.5 13.1
6.8 10.1 Y.sub.2O.sub.3 0.0 3.9 0.0 3.9 3.9 0.0 0.0 2.0 TiO.sub.2
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 B.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 SrO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SnO.sub.2 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 Specific gravity 2.53 2.59 2.54 2.59 2.60
2.57 2.47 Tg (.degree. C.) 469 470 467 468 471 465 448 Thermal
expansion 122 123 122 120 124 122 128 coefficient
(.times.10-.sup.7/.degree. C.) Tc (.degree. C.) 593 592 592 571 571
Tg.sub.DSC (.degree. C.) 489 483 482 459 468 Tc-Tg (.degree. C.)
104 109 110 112 103 Young's modulus (GPa) 87 90 91 91 92 91 87
Vickers hardness 541 537 543 631 621 627 555 Fracture toughness
value 0.75 Relative permittivity Dielectric loss tangent
TABLE-US-00002 TABLE 2 G17 G18 G19 G20 G21 G22 G23 G24 G25 G26 G27
G28 G29 G30 G31 G32 G33 G34 SiO.sub.2 64.0 54.5 61.5 62.9 52.0 54.9
62.9 65.4 54.0 52.8 50.3 50.7 50.8 53.5 51.0 52.8 54.4 49.9
Al.sub.2O.sub.3 5.9 2.0 2.0 2.0 1.9 2.0 22.4 22.4 18.0 8.7 8.5 12.0
12.1 8.7 8.5 8.8 8.9 2.0 Li.sub.2O 10.0 18.4 18.4 13.0 17.5 16.9
4.3 4.3 0.0 17.5 17.0 17.2 17.3 17.4 17.0 17.6 17.8 28.0 Na.sub.2O
2.0 2.0 0.1 2.0 1.9 5.0 2.0 2.0 13.0 1.9 1.9 1.9 2.6 0.5 0.5 1.9
2.0 2.0 K.sub.2O 2.0 2.0 2.0 2.0 1.9 5.6 0.0 0.0 2.3 0.0 0.0 1.9
0.8 0.8 0.8 1.9 2.0 2.0 MgO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.6 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 CaO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 P.sub.2O.sub.5 5.9 5.9 5.9
5.9 5.7 5.8 3.0 1.5 0.0 5.7 5.5 5.6 5.6 5.6 5.5 5.7 5.7 5.9
ZrO.sub.2 10.1 10.1 10.1 10.1 19.0 9.8 2.3 2.3 0.0 9.6 9.3 3.2 3.2
9.6 9.3 7.4 5.4 10.1 Y.sub.2O.sub.3 0.0 5.0 0.0 2.0 0.0 0.0 0.0 0.0
0.0 3.9 7.5 7.6 7.6 3.9 7.5 3.9 3.9 0.0 TiO.sub.2 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
B.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 SrO 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 SnO.sub.2 0.0 0.0 0.0 0.0 0.0 0.0 2.1
2.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Specific 2.50 2.61 2.51
2.57 2.55 2.59 2.54 gravity Tg (.degree. C.) 510 459 463 471 423
714 739 472.0 488.0 461.0 478 470 450 Thermal 91 128 121 117 139 50
50 117 119 123 121 123 124 expansion coefficient
(.times.10.sup.-7/.degree. C.) Tc (.degree. C.) 740 627 593 627 946
925 730 609 663 593 609 614 677 592 574 Tg.sub.DSC (.degree. C.)
535 473 481 501 711 704 650 494 502 481 484 501 510 485 473 Tc-Tg
(.degree. C.) 205 154 112 126 235 221 80 116 161 112 125 113 167
107 101 Young's 85 91 87 94 88 83 83 94 95 91 92 94 93 93 90
modulus (GPa) Vickers 631 555 590 615 708 573 575 567 577 570 566
570 558 hardness Fracture 0.80 0.71 toughness value
<Crystallization Treatment and Evaluation of Glass
Ceramics>
[0159] The obtained glass blocks were each processed into 50
mm.times.50 mm.times.1.5 mm, and this processed glass was
heat-treated under each of the sets of conditions shown in Tables 3
and 4 to obtain a glass ceramic. The section "Crystallization
conditions" in each table indicates nucleation treatment conditions
in the upper portion and crystal growth treatment conditions in the
lower portion. For example, in cases when a set of conditions
consists of "550.degree. C.-2 h" in the upper portion and
"730.degree. C.-2 h" in the lower portion, this means that the
glass was held at 550.degree. C. for 2 hours and then held at
730.degree. C. for 2 hours. GC1 to GC17, GC19, and GC23 to GC35 are
Working Examples, and GC18 and GC20 to GC22 are Comparative
Examples.
[0160] The obtained glass ceramics were each processed and
mirror-polished to obtain a glass ceramic sheet having a thickness
t of 0.7 mm. Rod-shaped samples for examining thermal expansion
coefficient were also prepared. Some of each remaining glass
ceramic was pulverized and subjected to analysis of precipitated
crystals. The results of the evaluation of the glass ceramics are
shown in Tables 3 to 5. The blanks indicate that the glasses were
not evaluated.
(Visible-Light Transmittance, Y Value, Main Wavelength .lamda.d,
Excitation Purity Pe)
[0161] Each glass ceramic sheet was examined for transmittance
within the wavelength range of 380-780 nm using a configuration
including a spectrophotometer (LAMBDA950, manufactured by
PerkinElmer, Inc.) equipped with an integrating-sphere unit (150-mm
InGaAs Int. Sphere) as a detector. An arithmetic average of
measured transmittance values was obtained as an average
transmittance [unit: %], which was taken as the visible-light
transmittance.
[0162] Moreover, tristimulus values X, Y, and Z for object in the
XYZ color system were calculated from the measured transmittance
values to determine an object color under illuminant C. The main
wavelength .lamda.d and the excitation purity Pe were determined
therefrom.
(Haze Value)
[0163] Using a hazemeter (HZ-V3, manufactured by Suga Test
Instruments Co., Ltd.), a haze value [unit: %] was measured under
an illuminant C.
(X-Ray Diffractometry: Precipitated Crystals and Degree of
Crystallinity)
[0164] Each glass ceramic was examined by powder X-ray
diffractometry under the following conditions to identify the
precipitated crystals. Furthermore, the degree of crystallinity was
calculated from the obtained diffraction intensities by a Rietveld
method. Measurement apparatus: SmartLab, manufactured by Rigaku
Corp.
[0165] X ray used: CuK.alpha. ray
[0166] Measurement range: 20=10.degree.-80.degree.
[0167] Speed: 10.degree./min
[0168] Step: 0.02.degree.
[0169] The detected crystals are shown in the section of kinds of
crystals in Tables 3 and 4. In the tables, LS indicates lithium
metasilicate, LD indicates lithium disilicate, PSP indicates
.beta.-spodumene, LP indicates lithiumphosphate, and spinel
indicates spinel. Each degree of crystallinity is the sum of the
degrees of crystallinity determined for the respective kinds of
crystals shown in Tables 3 to 5 by the Rietveld method.
(Crystal Size)
[0170] Glass ceramic GC1 was pulverized with an agate mortar and
then sprinkled on a collodion film which had been hydrophilized. An
extremely thin portion of the glass was examined with a
transmission electron microscope (JEM-2010F, manufactured by JEOL
Ltd.) to determine an average particle diameter (unit: nm) of the
precipitated crystals. A TEM image is shown in FIG. 7.
(Glass Transition Point, Thermal Expansion Coefficient, Specific
Gravity, Young's Modulus, Vickers Hardness)
[0171] The properties were determined in the same manners as for
the glasses of before crystallization. Furthermore, the difference
in Tg between before and after the crystallization was
determined.
(Refractive Index)
[0172] Each glass ceramic was mirror-polished to 15 mm.times.15
mm.times.0.7 mm and examined for refractive index by a V-block
method using precision refractometer KPR-2000 (manufactured by
Shimadzu Device Corp.).
TABLE-US-00003 TABLE 3 GC1 GC2 GC3 GC4 GC5 GC6 GC7 GC8 GC9 GC10
GC11 Glass G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 composition Tg
(.degree. C.) 453 456 443 439 430 428 450 460 469 470 467 before
crystallization Heat 550-2 550-2 550-2 550-2 550-2 550-2 550-2
550-2 550-2 550-2 550-2 treatment 730-2 710-2 710-2 710-2 710-2
670-2 730-2 710-2 730-2 710-2 690-2 conditions (.degree. C.-hr)
Light 90.1 90.6 90.5 90.1 89.8 89.5 91.1 90.3 90.7 90.5 90.6
transmittance (%) Y value 90.3 90.8 90.7 90.3 90 89.7 91.3 90.4
90.8 90.7 90.8 Main 573 573 572 572 573 574 571 574 571 574 572
wavelength .lamda.d (nm) Excitation 0.31 0.44 0.32 0.36 0.16 0.46
0.4 purity Pe Haze (%) 0.08 0.08 0.09 0.07 0.11 0.11 0.07 0.08 0.07
0.08 0.08 Main LS LS LS LS LS LS LS crystals LP LS LP LS LP LS LP
LS LP LP LP Crystal 20-40 20-40 20-40 20-40 20-40 20-40 20-40 20-40
20-40 20-40 20-40 size (nm) Degree of 40 40 40 40 40 40 40 40 40 40
40 crystallinity or or or or or or or or or or or (%) less less
less less less less less less less less less Specific gravity 2.59
2.59 2.61 2.62 2.63 2.61 2.59 2.66 2.59 Tg (.degree. C.) 627 587
595 585 601 578 624 624 586 585 567 after crystallization .DELTA.Tg
(.degree. C.) 174 131 152 146 171 150 174 164 117 115 100 Thermal
134 125 133 139 140 142 126 131 134 125 125 expansion coefficient
(.times.10.sup.-7/.degree. C.) Young's 104 104 106 105 110 104 102
104 102 modulus (GPa) Vickers 801 753 649 739 668 723 686 hardness
Fracture 0.93 toughness value Refractive 1.5757 1.5764 1.5794
1.5799 1.5816 1.5825 1.5784 1.5759 1.5847 1.5763 index Relative
7.23 permittivity Dielectric loss 0.007 tangent
TABLE-US-00004 TABLE 4 GC12 GC13 GC14 GC15 GC16 GC17 GC18 GC19 GC20
GC21 GC22 Glass G12 G13 G14 G15 G1 G1 G1 G22 G23 G24 G25
composition Tg (.degree. C.) 468 471 465 448 453 453 453 423 714
739 650 before crystallization Heat 550-2 550-2 550-2 550-2 550-2
550-2 550-2 550-2 750-4 750-4 650-2 treatment 710-2 730-2 750-2
710-2 650-2 750-2 780-2 710-2 900-4 920-4 730-2 conditions
(.degree. C.-hr) Visible- 90.6 90.4 89.1 90.6 90.9 89.3 90.4 89.9
88.0 88.2 light transmittance ( %) Y value 90.8 90.5 89.2 90.7 91.0
89.4 90.0 87.9 87.8 Main 570 573 574 576 576 573 576 578 582
wavelength .lamda.d (nm) Excitation 0.20 0.20 0.3 0.34 0.35 0.38
0.68 1.20 1.24 purity Pe Haze (%) 0.10 0.09 0.10 0.08 0.03 0.20
11.90 0.10 0.23 0.50 0.09 Main LS LS LS LS LS LS LS LS .beta. SP
.beta. SP spinel crystals LP LP LP LD LP Crystal 20-40 20-40 20-40
20-40 20-40 20-40 30-80 20-40 120 120 7 size (nm) Degree of 40 40
40 40 40 40 40 73 71 crystallinity or or or or or or or (%) less
less less less less less less Tg (.degree. C.) after 611 610 601
638 612 872 902 crystallization .DELTA.Tg (.degree. C.) 143 139 136
190 159 Thermal 122 123 131 128 12 12 expansion coefficient
(.times.10-7/.degree. C.) Specific 2.66 2.66 2.64 2.54 2.58 2.59
2.63 2.48 2.48 gravity Young's 105 105 109 103 101 105 107 105 87
90 81 modulus (GPa) Vickers 818 823 696 723 788 786 730 783 732
hardness Fracture 0.91 0.83 0.72 toughness value Refractive 1.5854
1.5769 1.5859 1.5639 1.5768 1.5232 1.5244 index Relative 6.36
permittivity Dielectric 0.014 loss tangent
TABLE-US-00005 TABLE 5 GC23 GC24 GC25 GC26 GC27 GC28 GC29 GC30 GC31
GC32 GC33 GC34 GC35 Glass G26 G27 G28 G29 G30 G31 G32 G33 G16 G17
G18 G19 G20 composition Tg (.degree. C.) 472 488 464 467 469 473
470 451 510 459 463 before crystallization Heat 550-2 550-2 550-2
550-2 550-2 550-2 550-2 550-2 550-2 550-2 550-2 550-2 550-2
treatment 710-2 690-2 730-2 710-2 690-2 710-2 730-2 730-2 710-2
750-2 730-2 710-2 730-2 conditions (.degree. C.-hr) Visible- 90.1
88.8 90.0 89.9 light transmittance (%) Y value Main wavelength
.lamda.d (nm) Excitation purity Pe Haze (%) 0.09 0.32 0.14 0.23
0.11 0.10 0.11 0.15 0.20 0.30 0.30 0.07 0.30 Main LS LS LS LS LS LS
LS LS LS LS LS LS crystals LP LP LP LP LP LP LP LP LP LP Crystal
20-40 20-40 20-40 20-40 20-40 20-40 20-40 20-40 20-40 20-40 20-40
20-40 20-40 size (nm) Degree of 40 40 40 40 40 40 40 40 40 40 40 40
40 crystallinity or or or or or or or or or or or or or (%) less
less less less less less less less less less less less less Tg
(.degree. C.) 615 616 602 619 605 598 after crystallization
.DELTA.Tg (.degree. C.) 143 128 138 152 135 147 Thermal 120 121 121
124 127 129 expansion coefficient (.times.10-7/.degree. C.)
Specific 2.71 2.64 2.60 2.52 2.68 2.57 gravity Young's 103 104 103
105 103 104 104 104 91 108 101 modulus (GPa) Vickers 747 721 764
610 755 730 722 hardness Fracture toughness value Refractive 1.5852
1.5936 1.5784 1.5713 index
[0173] GC18, in which lithium disilicate crystals had precipitated
besides lithium metasilicate crystals, contained crystals having
large particle diameters and had a large haze value and a poor
appearance. GC20 and GC21, in which .beta.-spodumene had
precipitated, had glass transition points after crystallization
higher than 800.degree. C. and had poor bending processability.
<Chemical Strengthening Treatment and Evaluation of Strengthened
Glasses>
[0174] GC1 to GC16, GC19, GC22, and G1 which had not been
crystallized were each subjected to a two-step chemical
strengthening treatment consisting of 3-hours immersion in
450.degree. C. sodium nitrate and subsequent 1-hour immersion in
450.degree. C. potassium nitrate. Thus, strengthened glasses SG1 to
SG19 were obtained. SG1 to SG16 are Working Examples, and SG17 to
SG19 are Comparative Examples.
(Stress Profile)
[0175] Stress values were measured using surface stress meter
FSM-6000, manufactured by Orihara Manufacturing Co., Ltd., and
measuring device SLP-2000 utilizing scattered-light
photoelasticity, manufactured by Orihara Manufacturing Co., Ltd.,
and thereby a compressive stress value CS.sub.0 [unit: MPa] on the
glass surface, a compressive stress value CS.sub.50 [unit: MPa] at
a depth of 50 .mu.m, and a depth DOL [unit: .mu.m] at which the
compressive stress value became zero were read out. The results
thereof are shown in Tables 6 and 7.
[0176] A stress profile of SG13 is shown in FIG. 1.
TABLE-US-00006 TABLE 6 SG1 SG2 SG3 SG4 SG5 SG6 SG7 SG8 SG9 Glass
for GC1 GC2 GC3 GC4 GC5 GC6 GC7 GC8 GC9 strength- ening DOL 130 135
140 130 (.mu.m) CS.sub.0 625 720 750 490 515 629 800 900 700 (MPa)
CS5.sub.0 195 155 150 (MPa)
TABLE-US-00007 TABLE 7 SG10 SG11 SG12 SG13 SG14 SG15 SG16 SG17 SG18
SG19 Glass for strengthening GC10 GC11 GC12 GC13 GC14 GC15 GC16 G1
GC19 GC22 DOL (.mu.m) 124 140 122 126 125 120 50 CS.sub.0 (MPa) 760
720 490 710 300 395 1000 CS.sub.50 (MPa) 230 209 214 222 179 0
[0177] SG17, which was obtained by chemically strengthening the
glass which has not been subjected to crystallization, had a small
value of CS.sub.0 because stress relaxation occurred during the
strengthening treatment. SG18, which was obtained by chemically
strengthening glass ceramic GC19 having a high K.sub.2O content,
also had a small value of CS.sub.0. SG19, which was obtained by
chemically strengthening glass ceramic GC22, which was a
Comparative Example containing no Li.sub.2O, had a small value of
DOL and was less apt to have sufficient strength. It can be seen
that the present glass ceramic can obtain high strength through a
chemical strengthening treatment.
[0178] While the present invention has been described in detail and
with reference to specific embodiments thereof, it will be apparent
to one skilled in the art that various changes and modifications
can be made therein without departing from the spirit and scope
thereof. This application is based on a Japanese patent application
filed on Feb. 8, 2019 (Application No. 2019-021896), the entire
contents thereof being incorporated herein by reference. All the
references cited here are incorporated herein as a whole.
* * * * *