U.S. patent application number 15/988352 was filed with the patent office on 2018-09-20 for glass sheet.
This patent application is currently assigned to ASAHI GLASS COMPANY, LIMITED. The applicant listed for this patent is ASAHI GLASS COMPANY, LIMITED. Invention is credited to Shusaku AKIBA, Seiki OHARA, Kazunari TOHYAMA, Shuji YAMAZAKI.
Application Number | 20180265398 15/988352 |
Document ID | / |
Family ID | 56150472 |
Filed Date | 2018-09-20 |
United States Patent
Application |
20180265398 |
Kind Code |
A1 |
YAMAZAKI; Shuji ; et
al. |
September 20, 2018 |
GLASS SHEET
Abstract
A glass sheet includes, as represented by mole percentage based
on oxides, from 55.5 to 80% of SiO.sub.2, from 12 to 20% of
Al.sub.2O.sub.3, from 8 to 25% of Na.sub.2O, 2.5% or more of
P.sub.2O.sub.5, and 1% or more of an alkaline earth metal RO (RO is
MgO+CaO+SrO+BaO).
Inventors: |
YAMAZAKI; Shuji; (Tokyo,
JP) ; AKIBA; Shusaku; (Tokyo, JP) ; OHARA;
Seiki; (Tokyo, JP) ; TOHYAMA; Kazunari;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASAHI GLASS COMPANY, LIMITED |
Chiyoda-ku |
|
JP |
|
|
Assignee: |
ASAHI GLASS COMPANY,
LIMITED
Chiyoda-ku
JP
|
Family ID: |
56150472 |
Appl. No.: |
15/988352 |
Filed: |
May 24, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15631554 |
Jun 23, 2017 |
10040716 |
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15988352 |
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PCT/JP2015/085723 |
Dec 21, 2015 |
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15631554 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03C 3/085 20130101;
C03C 2204/00 20130101; C03C 3/097 20130101; C03C 4/18 20130101;
C03C 21/002 20130101 |
International
Class: |
C03C 3/097 20060101
C03C003/097; C03C 21/00 20060101 C03C021/00; C03C 3/085 20060101
C03C003/085; C03C 4/18 20060101 C03C004/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2014 |
JP |
2014-261984 |
Claims
1-7: (canceled)
8. A glass sheet comprising, as represented by mole percentage
based on oxides, from 59 to 72.5% of SiO.sub.2, from 12 to 20% of
Al.sub.2O.sub.3, from 8 to 17% of Na.sub.2O, more than 0% and 4.0%
or less of P.sub.2O.sub.5, from 0 to 3% of MgO, from 0 to 3% of
SrO, from 0 to 3% of BaO, and from 0 to 3% of K.sub.2O, wherein,
when an indentation is formed by using a Vickers indenter, a
pressing load of the Vickers indenter at which an incidence of
cracking is 50% is equal to or more than 300 gf.
9. The glass sheet according to claim 8, wherein a depth at which a
hydrogen amount is 1.05 times a bulk value thereof is equal to or
more than 500 nm from a surface of the glass sheet.
10. The glass sheet according to claim 8, wherein an average value
of a hydrogen amount in a depth of from 500 nm to 1,000 nm from a
surface of the glass sheet is equal to or more than 1.5 times a
bulk value thereof.
11. The glass sheet according to claim 8, wherein a content of SiO2
is 61% or more.
12. The glass sheet according to claim 8, wherein a content of CaO
is 1% or less.
13. The glass sheet according to claim 8, wherein SrO is not
contained.
14. The glass sheet according to claim 8, wherein BaO is not
contained.
15. The glass sheet according to claim 8, further comprising 1% or
more of an alkaline earth metal RO.
16. The glass sheet according to claim 8, wherein a content of MgO
is 1.5% or less.
Description
TECHNICAL FIELD
[0001] An embodiment of the present invention relates to a glass
sheet. In particular, the embodiment relates to a glass sheet for
chemical strengthening, that is, a glass sheet which can be
suitably used in a chemically strengthened glass.
BACKGROUND ART
[0002] In recent years, information equipment including a touch
panel display, as in a tablet PC, a smart phone, an electronic book
reader, or the like has been the mainstream.
[0003] Any glass of a touch sensor glass, a cover glass, and a
glass of OGS (one glass solution) is required to have a thin
thickness and high strength, and a chemically strengthened glass
which is subjected to a chemical strengthening treatment through
ion exchange is used.
[0004] Strengthening characteristics of the chemically strengthened
glass are generally expressed by a surface compressive stress (CS)
and a depth of compressive stress (DOL: depth of layer).
[0005] A surface compressive stress layer formed by the chemical
strengthening prevents a fracture occurring by an impact from being
propagated. It is disclosed that phosphoric acid is contained in
the composition thereof, and thus further damage resistance is
obtained without degrading chemical strengthening characteristics
(for example, see Patent Literature 1).
CITATION LIST
Patent Literature
[0006] Patent Literature 1: JP-T-2013-544227 (the term "JP-T" as
used herein means a published Japanese translation of a PCT
application)
[0007] Patent Literature 2: Japanese Patent No. 3164223
SUMMARY OF INVENTION
Technical Problem
[0008] A phosphate-based glass has low weather resistance and
erosion easily occurs on the surface thereof by blurring or
weathering when being used for a long term. Thus, the
phosphate-based glass has poor practical utility (for example, see
Patent Literature 2). When surface modification such as
anti-glaring (AG) is performed on a cover glass, finish is
significantly sensitive to a concentration change of an etching
liquid. Thus, process margin significantly becomes small, and thus
the yield is decreased or the cost is increased.
[0009] An object of the present invention is to provide a glass
sheet which contains a phosphate and has a damage resistance and an
acid resistance.
Solution to Problem
[0010] A glass sheet according to an aspect of the present
invention is characterized by containing, as represented by mole
percentage based on oxides, from 55.5 to 80% of SiO.sub.2, from 12
to 20% of Al.sub.2O.sub.3, from 8 to 25% of Na.sub.2O, 2.5% or more
of P.sub.2O.sub.5, and 1% or more of an alkaline earth metal RO (RO
is MgO+CaO+SrO+BaO).
[0011] It is preferable that a depth of the glass sheet at which a
hydrogen amount is 1.05 times a bulk value thereof is equal to or
more than 500 nm from a surface of the glass sheet. It is
preferable that an average value of a hydrogen amount in a depth of
from 500 nm to 1,000 nm from a surface of the glass sheet is equal
to or more than 1.5 times a bulk value thereof. It is preferable
that the glass sheet contains, as represented by mole percentage
based on oxides, from 57 to 76.5% of SiO.sub.2, from 12 to 18% of
Al.sub.2O.sub.3, from 8 to 25% of Na.sub.2O, from 2.5 to 10% of
P.sub.2O.sub.5, and 1% or more of the alkaline earth metal RO. It
is preferable that the glass sheet further contains 0.1% or more of
F.
[0012] The glass sheet which is capable of being chemically
strengthened is more preferable.
Advantageous Effects of Invention
[0013] In the embodiment of the present invention, it is possible
to provide a glass sheet which contains a phosphate and has a
damage resistance and an acid resistance.
DESCRIPTION OF EMBODIMENTS
[0014] Hereinafter, an embodiment of the present invention will be
described in detail. In this description, "mass reduction" and
"weight reduction" have the same meaning. "To" indicating a
numerical range is used to have the meaning of including numerical
values described before and after "to" as a lower limit value and
an upper limit value.
[0015] A glass sheet in the embodiment of the present invention is
characterized by containing, as represented by mole percentage
based on oxides, from 55.5 to 80% of SiO.sub.2, from 12 to 20% of
Al.sub.2O.sub.3, from 8 to 25% of Na.sub.2O, 2.5% or more of
P.sub.2O.sub.5, and 1% or more of an alkaline earth metal RO (RO is
MgO+CaO+SrO+BaO).
[0016] It is preferable that in the embodiment of the present
invention, the depth of the glass sheet at which the hydrogen
amount is equal to or more than 1.05 times of a bulk value thereof
is equal to or more than 500 nm from the surface thereof. The depth
thereof is more preferably equal to or more than 700 nm and further
preferably equal to or more than 1,000 nm. By introducing more
hydrogen than the bulk value thereof into a region from the surface
to a depth of at least 500 nm, it is possible to further improve
the acid resistance in comparison to a bulk body. Thus, it is
possible to largely increase process margin in an etching treatment
and the like. Here, the bulk value indicates an average value of
the hydrogen amount in a depth of 100 .mu.m or more from the glass
sheet. The bulk body indicates an untreated glass sheet which has
been polished from the surface thereof to 100 .mu.m or more.
[0017] In the glass sheet in the embodiment of the present
invention, it is preferable that the average value of the hydrogen
amount in a depth of from 500 nm to 1,000 nm from the surface
thereof is equal to or more than 1.5 times the bulk value thereof.
The average value thereof is more preferably equal to or more than
2 times, further preferably equal to or more than 2.5 times, and
particularly preferably equal to or more than 3 times. With the
average value of the hydrogen amount in a depth of from 500 nm to
1,000 nm from the surface thereof is equal to or more than 1.5
times the bulk value, it is possible to further improve the acid
resistance in comparison to the bulk body. In order to prevent
degradation of strengthening characteristics and a stress
relaxation, an upper limit thereof is preferably equal to or less
than 10 times.
[0018] The reason why the acid resistance is improved by thus
introducing hydrogen into the surface is not understood in detail.
However, the present inventors consider that the reason is as
follows. That is, it is considered that a hydrogen ion introduced
into the surface and an oxonium ion or a water molecule in an
aqueous solution is repelled each other in electric charge and thus
it is possible to improve the acid resistance.
[0019] As a method of increasing the hydrogen amount in the surface
thereof, for example, the following is exemplified. That is, in a
process of forming a glass to have a predetermined shape, a
retention time at the vicinity of a formation temperature is
lengthened or diffusion of water into the air is suppressed by
increasing atmospheric pressure, and so on.
[0020] When a glass including a volatile component such as
phosphoric acid or boric acid is produced, in order to eliminate a
treatment of sediment by volatilization or composition
irregularity, a method in which the glass is produced for a short
period of time so as to have viscosity as high as possible in a
range allowed to be handed, thereby suppressing volatilization.
[0021] On the other hand, when a hydrogen introduction treatment is
performed into the surface of the glass in a production process
according to the embodiment of the present invention, it is
desirable that the hydrogen introduction treatment is performed at
a temperature at which viscosity in a glass forming tank in which
the surface of a glass substrate is formed is 10,000 poises to
500,000 poise.
[0022] In a case where the viscosity is more than 500,000 poises,
it takes a long period of time to introduce hydrogen, and
production efficiency is decreased. In a case where the viscosity
is less than 10,000 poises, it takes a short period of time to
introduce hydrogen. However, the bulk value is also increased by
introducing the large hydrogen amount, and thus physical properties
thereof are significantly changed. Excessive introduction of
hydrogen into a bulk may degrade tempering characteristics, for
example.
[0023] As another introduction method, a method in which thermal
treatment is performed on a glass sheet at a temperature of Tg
(glass transition point) or higher or a method in which acid
treatment or alkali treatment is performed on the glass sheet is
exemplified.
[0024] It is preferable that the glass sheet according to the
embodiment of the present invention contains, as represented by
mole percentage based on oxides, from 57 to 76.5% of SiO.sub.2,
from 12 to 18% of Al.sub.2O.sub.3, from 8 to 25% of Na.sub.2O, from
2.5 to 10% of P.sub.2O.sub.5, and 1% or more of the alkaline earth
metal RO.
[0025] It is preferable that the glass sheet according to the
embodiment of the present invention contains, as represented by
mole percentage based on oxides, from 55.5 to 80% of SiO.sub.2,
from 12 to 20% of Al.sub.2O, from 8 to 25% of Na.sub.2O, 2.5% or
more of P.sub.2O.sub.5, 0.1% or more of F, and 1% or more of the
alkaline earth metal RO.
[0026] In the glass sheet according to the embodiment of the
present invention, the reason of limiting a glass composition to
the above range will be described below. In the description, a
simple description of "%" means "mol %" as long as particular
statements are not made.
[0027] SiO.sub.2 is an essential component that constitutes a
network of glass. SiO.sub.2 is also an essential component that
reduces an occurrence of cracking when a flaw (an indentation) is
formed on the glass surface, or reduces a breakage rate when an
indentation is imparted after chemical strengthening. With the
content of SiO.sub.2 which is equal to or more than 55.5%, it is
possible to avoid degradation of stability, acid resistance,
weather resistance, or chipping resistance as a glass. The content
of SiO.sub.2 is preferably equal to or more than 57% and more
preferably equal to or more than 59%. With the content of SiO.sub.2
which is equal to or less than 80%, it is possible to avoid
degradation of the melting property due to an increase of the
viscosity of the glass. The content of SiO.sub.2 is preferably
equal to or less than 76.5% and more preferably equal to or less
than 72.5%.
[0028] Al.sub.2O.sub.3 is a component effective to improve ion
exchange performance and chipping resistance or a component that
increases the surface compressive stress, and is an essential
component. With the content of Al.sub.2O.sub.3 which is equal to or
more than 12%, a desired surface compressive stress value or
compressive stress layer thickness is obtained by ion exchange.
With the content of Al.sub.2O.sub.3 which is equal to or less than
20%, it is possible to prevent an increase of the viscosity of the
glass and to perform uniform melting, or it is possible to avoid
degradation of the acid resistance. The content of Al.sub.2O.sub.3
is preferably equal to or less than 18%, more preferably equal to
or less than 16%, and further preferably equal to or less than
15%.
[0029] P.sub.2O.sub.5 is a component that improves the damage
resistance without hindering the ion exchange performance, and is
essential. With the content of P.sub.2O.sub.5 which is equal to or
more than 2.5%, it is possible to obtain a glass which has high
crack extension initiation load (CIL). The content of
P.sub.2O.sub.5 is preferably equal to or more than 3%, and more
preferably equal to or more than 5%. It is possible to obtain a
glass which is particularly excellent in the acid resistance, by
setting the content of P.sub.2O.sub.5 to be equal to or less than
10%
[0030] Na.sub.2O is a component that forms a surface compressive
stress layer by ion exchange and improves the melting property of
the glass, and is essential. With the content of Na.sub.2O which is
equal to or more than 8%, it is possible to form a desired surface
compressive stress layer by ion exchange. The content of Na.sub.2O
is preferably equal to or more than 10%, more preferably equal to
or more than 12%, and further preferably equal to or more than 14%.
With the content of Na.sub.2O which is equal to or less than 25%,
it is possible to avoid degradation of the weather resistance or
the acid resistance or to avoid the occurrence of cracking from the
indentation. The content of Na.sub.2O is preferably equal to or
less than 20% and more preferably equal to or less than 18%.
[0031] K.sub.2O is not essential but increases an ion exchange
rate. K.sub.2O may be contained in a range of 5% or less. With the
content of K.sub.2O which is equal to or less than 5%, it is
possible to avoid the occurrence of cracking from the indentation
or to avoid an increase of a change in the surface compressive
stress due to the concentration of NaNO.sub.3 in a potassium
nitrate molten salt. The content of K.sub.2O is preferably equal to
or less than 3% and more preferably equal to or less than 1%. In
the case where it is desired to reduce the change of the surface
compressive stress due to the concentration of NaNO.sub.3 in the
potassium nitrate molten salt, it is preferable that K.sub.2O is
not contained.
[0032] The alkaline earth metal oxide (alkaline earth metal RO) of
MgO, CaO, SrO, and BaO are components effective for improving the
weather resistance and lowers the viscosity of the glass, thereby
rendering the glass easy to be melted. The content of
MgO+CaO+SrO+BaO is preferably equal to or more than 1% and more
preferably equal to or more than 1.5%. From a point that it is
possible to suppress an occurrence of devitrification and a
decrease of an ion exchange rate, as an upper limit thereof, it is
preferably equal to or less than 15%. As the upper limit thereof,
it is more preferably equal to or less than 10% and further
preferably equal to or less than 7%.
[0033] The preferable content of each component is as follows.
[0034] MgO is a component that increases the surface compressive
stress and improves the melting property. Therefore, MgO may be
contained in a range of 15% or less. With the content of MgO which
is equal to or less than 15%, it is possible to avoid
devitrification of the glass or the decrease of the ion exchange
rate. The content of MgO is preferably equal to or less than 10%,
more preferably equal to or less than 8%, and further preferably
equal to or less than 5%.
[0035] CaO may be contained in a range of 5% or less in order to
improve the melting property at a high temperature or to prevent
the occurrence of devitrification. With the content of CaO which is
equal to or less than 5%, it is possible to avoid reduction of the
ion exchange rate or degradation of resistance against the
occurrence of cracking. The content of CaO is preferably equal to
or less than 3%, and more preferably equal to or less than 1%.
[0036] SrO may be contained if necessary, but SrO has a large
effect of reducing the ion exchange rate in comparison to MgO or
CaO. Therefore, it is preferable that the content thereof is equal
to or less than 3% even when contained. Typically, SrO is not
contained.
[0037] BaO has the largest effect of reducing the ion exchange rate
among alkaline earth metal oxides. Therefore, it is preferable that
BaO is not contained, or even when contained, the content thereof
is equal to or less than 3%. Typically, BaO is not contained.
[0038] ZrO.sub.2 is a component that improves hardness, suppresses
stress relaxation by increasing a softening point, or improves the
acid resistance. ZrO.sub.2 may be contained in a range of 8% or
less. With ZrO.sub.2 which is equal to or less than 8%, it is
possible to avoid the occurrence of cracking from an indentation or
the increase of a devitrification temperature. The content of
ZrO.sub.2 is preferably equal to or less than 5%, more preferably
equal to or less than 3%, and further preferably equal to or less
than 2%.
[0039] F is a component that improves chemical durability. With the
content of F which is equal to or more than 0.1%, it is possible to
improve the acid resistance. SnF.sub.2, ZnF.sub.2, AlF.sub.3,
MgF.sub.2, SrF.sub.2, or CaF.sub.2 can be used as a fluorine raw
material. Since it is possible to prevent the occurrence of
volatilization or devitrification and to stably produce the glass,
an upper limit thereof is preferably equal to or less than 5%.
[0040] In addition, a chloride, a fluoride, or the like may be
suitably contained as a refining agent for glass melting. Although
the glass sheet in the present invention originally contains the
above-described components, other components may be contained in a
range without impairing the object of the present invention. In the
case of containing such components, the total content of the
components thereof is preferably equal to or less than 5% and more
preferably equal to or less than 3%. The total content thereof is
typically equal to or less than 1%.
[0041] In the glass sheet according to the embodiment of the
present invention, when an indentation is formed by using a Vickers
indenter, a pressing load of the Vickers indenter at which the
incidence of cracking is 50% is preferably equal to or more than
300 gf, more preferably equal to or more than 400 gf, and further
preferably equal to or more than 500 gf. If the pressing load of
the Vickers indenter is less than 300 gf, a flaw easily occurs in
the production process or transportation before the chemical
strengthening treatment and therefore there is a probability that
desired strength is not obtained even if the chemical strengthening
treatment is performed.
[0042] The glass sheet according to the embodiment of the present
invention generally has a sheet shape, but may be a flat sheet or a
glass sheet subjected to bending. The glass according to the
embodiment is a glass sheet which is formed to have a flat sheet
shape by known glass forming methods such as a float method, a
fusion method, and a slot down draw method.
[0043] The glass sheet according to the embodiment of the present
invention has dimensions which is allowed to be formed by existing
forming methods. That is, if a glass is formed by a float method, a
continuous ribbon-like glass having a width by float forming is
obtained. Finally, the glass is cut to have a size suitable for a
use purpose.
[0044] That is, the glass sheet according to the present invention
has a size of a display of a tablet PC, a smart phone, or the like
or has a size of a window glass of a building or a house. The glass
in the embodiment is generally cut to have a rectangular shape, but
there is no problem when cut to have other shapes such as a
circular shape or a polygonal shape. Example of the glass also
include a glass subjected to hole making.
[0045] <Chemical Strengthening Treatment>
[0046] It is preferable that the glass sheet according to the
present invention is a glass sheet which can be subjected to the
chemical strengthening treatment, that is, a glass sheet for
chemical strengthening. The chemical strengthening treatment can be
performed by well-known methods in the related art. It is
preferable that shape processing according to the use, for example,
mechanical machining such as cutting, edge processing, and hole
making is performed before the chemical strengthening
treatment.
[0047] According to the chemical strengthening treatment, a glass
substrate is brought into contact with a melt of an alkali metal
salt (for example, a potassium nitrate salt) containing an alkali
metal ion having a large ion radius (typically, K ion) by immersion
or the like, thereby substituting a metal ion having a small ion
radius (typically, Na ion) in the glass substrate with the metal
ion having a large ion radius.
[0048] The chemical strengthening treatment can be performed, for
example, by immersing the glass sheet in a molten salt of potassium
nitrate at 300 to 550.degree. C. for 5 minutes to 20 hours.
Regarding ion exchange conditions, optimum conditions may be
selected, considering the viscosity characteristics of glass, the
use, the sheet thickness, the tensile stress in the inside of glass
and the like.
[0049] Examples of the molten salt for performing the ion exchange
treatment include, for example, an alkali nitrate such as potassium
nitrate, potassium sulfate and potassium chloride, the alkali
sulfate and an alkali chloride salt. The molten salt may be singly
used or may be used in combination of plural kinds thereof. A salt
including sodium may be mixed in order to adjust the chemical
strengthening characteristics.
[0050] In the embodiment of the present invention, a treatment
condition of the chemical strengthening treatment is not
particularly limited and the best condition may be selected in
consideration of characteristics of the glass, the molten salt, and
the like.
[0051] The depth of a surface compressive stress layer of the
chemically strengthened glass and the surface compressive stress
value may be measured by using a surface stress meter (for example,
FSM-6000 manufactured by Orihara Industrial Co., Ltd.) and the
like.
[0052] The glass sheet in the embodiment of the present invention
is subjected to the chemical strengthening treatment, and thus it
is possible to obtain a chemically strengthened glass. Examples of
a product using the chemically strengthened glass include a cover
glass of, for example, a display device such as a digital camera, a
mobile phone, and a mobile information terminal (PDA), and a glass
substrate of a display.
[0053] The use of the glass sheet in the embodiment of the present
invention is not particularly limited. In the case where the
chemical strengthening is performed, the glass sheet has high
mechanical strength, and therefore a glass sheet subjected to
chemical strengthening is suitably used in a place where impact due
to falling or contact with another material is anticipated.
[0054] Specifically, for example, there are uses for protection of
machines or machinery, such as a cover glass for a display part of
a mobile phone (including a multifunctional information terminal
such as a smart phone), a PHS, a PDA, a tablet type terminal, a
notebook type personal computer, a game machine, a portable music
or video player, an E-book, an electronic terminal, a clock, a
camera, a GPS, or the like, a cover glass of a monitor for
operating a touch panel of the above devices, a cover glass of a
cooking device such as a microwave or an oven toaster; a top sheet
of an electromagnetic cooker or the like, or a cover glass of
instruments such as a meter and a gauge, and a glass sheet for a
reading unit of a copier, a scanner, or the like.
[0055] In addition, for example, there are uses such as a window
glass of a vehicle, a ship, an aircraft, and the like, a cover
glass of a household or industrial lighting device or a cover glass
of a signal, a guide lamp, and an electric bulletin board, and a
showcase and a bulletproof glass. There are uses of cover glasses
for protection of solar cells and condensing glass materials for
increasing the power generation efficiency of solar cells.
[0056] For example, there are uses such as a glass for various
mirrors, further, a base of an information storage medium such as a
HDD, and a substrate of an information storage medium such as a CD,
a DVD, and a Blu-lay disk.
[0057] For example, there are uses such as a water tank, a
tableware such as a dish or a cup, various cooking tools such as a
bottle or a chopping board, a cupboard, a shelf and a wall of a
refrigerator, and a building material such as a roof or a
partition.
[0058] In addition to such uses, the chemically strengthened glass
produced by performing the chemical strengthening treatment on the
glass sheet in the embodiment of the present invention is also
suitably used as a glass material for a display embedded in various
image display devices of liquid crystal, plasma, organic EL, and
the like.
Examples
[0059] Examples of the present invention will be specifically
described below. However, the present invention is not limited
thereto.
[0060] [Producing Glass Sheet]
[0061] Glass raw materials having been commonly used such as an
oxide, a hydroxide, a carbonate or a nitrate were appropriately
selected so as to obtain the composition which is shown in columns
from SiO.sub.2 to F in Examples 1 to 7 and Comparative Examples 1
and 2 in Table 1 and Table 2, and is represented by a mole
percentage, and weighed to be 900 g as a glass. Then, the mixed raw
material was put into a platinum crucible, introduced into a
resistance heating type electric furnace at 1,650.degree. C. and
melted for 4 hours, followed by refining and homogenization.
[0062] The molten glass obtained was cast into a mold material and
held at a temperature of Tg+30.degree. C. for 1 hour. Then, it was
cooled to room temperature at a rate of 0.5.degree. C./min to
obtain glass blocks. This block was cut and polished, and finally,
both surfaces thereof were finished to mirror surfaces to obtain a
sheet glass having a size of 20 mm.times.20 mm and a sheet
thickness of 1 mm
[0063] Regarding Examples 6 and 7, heat treatment was performed on
the obtained glass at a predetermined temperature and for a
predetermined time in Table 2, and thus the hydrogen introduction
treatment into the outermost surface was performed.
[0064] 50% CIL (gf), an acid resistance (unit: mg/cm.sup.2), and an
acid resistance improvement rate (%) of the glass and "bulk value,
500 to 1,000 nm depth average value, surface/bulk coefficient" of
the hydrogen amount are shown in Tables 1 and 2.
[0065] [Measurement of Physical Properties]
[0066] (1) 50% CIL
[0067] A CIL (crack initiation load) value was determined through
the following method. In a Vickers hardness tester, a Vickers
indenter was pressed for 15 seconds at a room temperature in the
atmosphere, and then the Vickers indenter was removed. After 15
seconds, the vicinity of an indentation was observed. In the
observation, how many cracks occur at the corner of the indentation
was examined. The measurement was performed for pressing loads of
the Vickers indenter of 100 gf, 200 gf, 300 gf, 500 gf, 1 kgf, and
2 kgf. An average value of the number of the occurring cracks was
calculated for each of the loads, and the pressing load of the
Vickers indenter, at which the incidence of cracking was 50% was
set to be 50% CIL.
[0068] (2) Acid Resistance Test
[0069] The acid resistance was calculated in a manner that the
obtained sheet glass was immersed in 0.1 mol/l of hydrochloric acid
warmed to 50.degree. C. for 3 hours, the amount of the reduced mass
before and after the immersion was measured, and the measured value
was divided by the surface area of the sheet glass.
[0070] (3) Improvement Rate (%)
[0071] The improvement rate of the acid resistance before and after
the heat treatment was determined as follows. "100-(mass reduction
after the heat treatment)/(mass reduction before the heat
treatment)*100" (%)
[0072] (4) Measurement of a Hydrogen Concentration Profile
[0073] A hydrogen concentration profile of the glass is a profile
measured under the following analysis condition. Secondary ion mass
spectrometry (SIMS) was used for the measurement of hydrogen
concentration profile of a glass substrate. A glass substrate to be
measured is simultaneously fed into a SIMS device and measuring is
sequentially performed to obtain a depth direction profile of the
intensities of .sup.1H.sup.- and .sup.30Si.sup.-. Then, the
.sup.-1H.sup.- profile is divided by the .sup.30Si profile to
obtain a depth direction profile of a .sup.1H.sup.-/.sup.30Si.sup.-
intensity ratio. From the depth direction profile of the
.sup.1H.sup.-/.sup.30Si.sup.- intensity ratio, an average
.sup.1H.sup.-/.sup.30Si.sup.- intensity ratio in a region of depth
from 500 nm to 1,000 nm is calculated. Here, there is a probability
that an influence of surface alteration or contamination due to
being left is reflected to the outermost surface. Therefore, the
hydrogen amount at a depth of 500 nm or more from the surface is
compared. A SIMS measurement condition is as follows.
[0074] [Measurement Condition of SIMS]
[0075] Device: ADEPT10100 manufactured by ULVAC-PHI, Inc.
[0076] Primary ion species: Cs.sup.+
[0077] Primary ion acceleration voltage: 5 kV
[0078] Primary ion current value: 200 nA
[0079] Primary ion incident angle: 60.degree. relative to a normal
line of a sample plane
[0080] Primary ion raster size: 300.times.300 .mu.m.sup.2
[0081] Secondary ion polarity: negative
[0082] Secondary ion detection region: 60.times.60 .mu.m.sup.2 (4%
of the raster size of the primary ion)
[0083] Use of neutralizing gun: yes
[0084] Method of converting a horizontal axis from a sputtering
time to a depth: The depth of an analysis crater is measured with a
stylus type surface profile analyzer (Dektak150 manufactured by
Veeco Inc.) and a primary ion sputtering rate is determined. Using
the sputtering rate, the horizontal axis is converted from the
sputtering time to the depth.
[0085] Field Axis Potential in .sup.1H.sup.- detection: The optimum
value may change in every device. An operator should carefully
define the value so that the back ground is fully cut off.
[0086] The bulk value described in Table 2 is an average value of
hydrogen concentration in a depth of from 500 nm to 1,000 nm from
the surface in an untreated glass sheet which has been polished to
a depth of 200 .mu.m from the surface thereof. Similarly, the 500
to 1000 nm depth average value is an average value of hydrogen
concentration in a depth of from 500 nm to 1,000 nm from the
surface in a glass sheet which has been subjected to the each
treatment. The surface/bulk coefficient is a value which shows how
many times the hydrogen amount in the 500 to 1000 nm depth average
value is compared to the bulk value thereof. The hydrogen
introduction depth is a depth at which the hydrogen amount is 1.05
times the bulk value thereof.
TABLE-US-00001 TABLE 1 Comparative Comparative (mol %) Ex. 1 Ex. 2
Ex. 3 Ex. 4 Ex. 5 Ex. 1 Ex. 2 SiO.sub.2 60.0 61.0 63.0 68.0 59.7
68.0 55.0 Al.sub.2O.sub.3 13.0 15.0 12.0 12.0 18.5 10.0 17.0
P.sub.2O.sub.5 6.0 4.0 7.0 3.0 2.8 5.0 Na.sub.2O 17.0 16.0 14.0
16.0 17.0 14.0 18.0 MgO 4.0 3.0 1.0 1.0 1.5 8.0 5.0 CaO 3.0 0.5 F
1.0 Total 100 100 100 100 100 100 100 RO 4.0 3.0 4.0 1.0 8.0 50%
not- 781 553 1.130 1.048 250 strengthened CIL (gf) Acid resistance
0.034 0.018 0.106 0.072 1.394 1.684 (mass reduction
(mg/cm.sup.2))
TABLE-US-00002 TABLE 2 Compar- ative (mol %) Ex. 5 Ex. 6 Ex. 7 Ex.
2 SiO.sub.2 59.7 55.0 59.7 55.0 Al.sub.2O.sub.3 18.5 17.0 18.5 17.0
P.sub.2O.sub.5 2.8 5.0 2.8 5.0 Na.sub.2O 17.0 18.0 17.0 18.0 MgO
1.5 5.0 1.5 5.0 CaO 0.5 0.5 F Total 100 100 100 100 Heat treatment
-- 800 800 -- temperature (.degree. C.) Heat treatment time (h) --
48 48 -- Bulk value 0.0205 -- -- 0.0242 500 to 1,000 nm depth
0.0205 0.0802 0.0731 0.0242 average value Surface/bulk coefficient
1.00 3.31 3.57 1.00 Acid resistance (mass 1.39 1.52 1.12 1.68
reduction (mg/cm.sup.2)) Improvement rate (%) -- 10 20 --
[0087] The following considerations were obtained from results
shown in Table 1 and Table 2.
[0088] In Examples 1 to 4, an aluminosilicate glass contains 2.5%
or more of P.sub.2O.sub.5 as represented by mole percentage based
on oxides, and thus 50% CIL is equal to or more than 500 gf.
[0089] On the other hand, in Comparative Example 1, P.sub.2O.sub.5
is not contained. In this case, 50% CIL shows a low value of 250
gf.
[0090] That is, it is understood that when an aluminosilicate glass
contained 2.5% or more of P.sub.2O.sub.5 as represented by mole
percentage based on oxides, a glass having high damage resistance
and having 50% CIL of 500 gf or more was obtained.
[0091] In Examples 1 to 5, from 55.5% to 80% of SiO.sub.2 and from
12% to 20% of Al.sub.2O.sub.3 are contained in an aluminosilicate
glass as represented by a mole percentage based on oxide, and thus
mass reduction is equal to or less than 1.5 mg/cm.sup.2. Further
among these, it was understood that by setting each of contents of
SiO.sub.2 to be from 57% to 76.5% and Al.sub.2O.sub.3 to be from
12% to 18% as in Examples 1 to 4, mass reduction was equal to or
less than 0.15 mg/cm.sup.2. Further, as in Example 2, 0.1% or more
of F is contained in an aluminosilicate glass as represented by
mole percentage based on oxides, and thus mass reduction is equal
to or less than 0.03 mg/cm.sup.2, and further it is possible to
suppress the occurrence of mass reduction.
[0092] In Comparative Example 2, SiO.sub.2 is equal to or less than
55.5%. Thus, mass reduction is equal to or more than 1.6
mg/cm.sup.2.
[0093] That is, it was understood that from 57% to 76.5% of
SiO.sub.2 and from 12% to 18% of Al.sub.2O.sub.3 were contained in
an aluminosilicate glass where the percentages are represented by a
mole percentage based on oxide, and thus a glass having high acid
resistance in which mass reduction was equal to or less than 0.15
mg/cm.sup.2 was obtained. It was understood that 0.1% or more of F
was contained, and thus the acid resistance was further
improved.
[0094] In Examples 6 and 7, the average value of the hydrogen
amount in a region of a depth of from 500 nm to 1,000 nm from the
surface is three times or more the bulk value thereof. In the
glasses, the acid resistance is improved by 10% or more. In
particular, in Example 7 where the change of the hydrogen amount is
larger, an effect of improving the acid resistance is high. The
hydrogen introduction depth in Examples 6 and 7 was equal to or
more than 1,000 nm.
[0095] The present invention is described in detail with reference
to the specific embodiment. However, various changes and
modifications may be made without departing from the gist and the
scope of the present invention, and this is obvious for those
skilled in the art. This application is based upon and claims the
benefit of priority from Japanese Patent Application No.
2014-261984 filed on Dec. 25, 2014. The contents of those
applications are incorporated herein by reference in their
entireties.
INDUSTRIAL APPLICABILITY
[0096] The glass sheet in the embodiment of the present invention
can be used for a substrate of a thin solar cell, a cover glass of
a display device, a window glass, or the like. The glass sheet can
be suitably used for a cover glass of a mobile device or the like
by performing chemical strengthening.
* * * * *