U.S. patent application number 12/528693 was filed with the patent office on 2010-05-13 for reinforced plate glass and method for manufacturing the same.
Invention is credited to Masahiro Sawada.
Application Number | 20100119846 12/528693 |
Document ID | / |
Family ID | 39738209 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100119846 |
Kind Code |
A1 |
Sawada; Masahiro |
May 13, 2010 |
REINFORCED PLATE GLASS AND METHOD FOR MANUFACTURING THE SAME
Abstract
[Object] To provide a method of manufacturing a reinforced plate
glass by which glass surface strength can be sufficiently
increased, and a stable quality reinforced plate glass is
manufactured at high production efficiency, and to provide a
reinforced plate glass manufactured by the manufacturing method.
[Solving Means] A reinforced plate glass (10) is formed of an
inorganic oxide glass, and is provided with a compression stress
layer by chemical reinforcement on plate surfaces (11, 12) opposed
to each other in a plate thickness direction. Plate end faces (13,
14, 15, 16) have regions where a compression stress is formed and
regions where no compression stress is formed.
Inventors: |
Sawada; Masahiro; (Shiga,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
39738209 |
Appl. No.: |
12/528693 |
Filed: |
March 3, 2008 |
PCT Filed: |
March 3, 2008 |
PCT NO: |
PCT/JP2008/053764 |
371 Date: |
August 26, 2009 |
Current U.S.
Class: |
428/426 ;
65/30.1 |
Current CPC
Class: |
C03B 33/091 20130101;
C03C 21/002 20130101; C03C 3/093 20130101; C03B 33/023 20130101;
C03C 19/00 20130101; Y02P 40/57 20151101; C03C 3/085 20130101; C03B
33/033 20130101; C03B 33/04 20130101; C03C 23/007 20130101; C03B
33/027 20130101; C03B 33/074 20130101; C03C 3/091 20130101; C03C
23/0025 20130101 |
Class at
Publication: |
428/426 ;
65/30.1 |
International
Class: |
B32B 17/06 20060101
B32B017/06; C03C 15/00 20060101 C03C015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 2, 2007 |
JP |
2007-052216 |
Claims
1. A reinforced plate glass made of an inorganic oxide glass,
comprising a compression stress layer formed by chemical
reinforcement on each of plate surfaces opposed to each other in a
plate thickness direction, and a region where a compression stress
is formed and a region where a compression stress is not formed on
a plate end face.
2. The reinforced plate glass according to claim 1, wherein the
region where a compression stress is formed is distributed in
parallel with the plate surface on the plate end face.
3. The reinforced plate glass according to claim 1, wherein a
stress distribution of the compression stress layer in a plate
thickness direction is limited in accordance with a compression
stress function represented by a compression stress value of the
plate surface, a thickness size of the compression stress layer,
and a thickness size of the region where a compression stress is
not formed.
4. The reinforced plate glass according to claim 1, wherein the
compression stress function is a function obtained by dividing a
product of the compression stress value and the thickness size of
the compression stress layer by the thickness size of the region
where a compression stress is not formed, and a value calculated by
the function is 40 MPa or less.
5. The reinforced plate glass according to claim 1, wherein a
compression stress value of at least one of the plate surfaces is
in a range of from 200 to 1,500 MPa.
6. The reinforced plate glass according to claim 1, wherein an
average breaking stress by a four-point bending test according to
JIS R1601 (1995) is 400 MPa or more, and a Weibull coefficient
according to JIS R1625 (1996) is 3 or more.
7. The reinforced plate glass according to claim 1, comprising 50
to 80% of SiO.sub.2, 0 to 15% of B.sub.2O.sub.3, 3 to 25% of
Al.sub.2O.sub.3, 0 to 20% of Li.sub.2O, 0 to 20% of Na.sub.2O, 3 to
25% of Li.sub.2O+Na.sub.2O, 0 to 20% of K.sub.2O, 0 to 10% of
CaO+MgO+ZnO+SrO+BaO, and 0 to 10% of TiO.sub.2+ZrO.sub.2,
represented by percent by mass of an oxide conversion.
8. The reinforced plate glass according to claim 1, wherein the
plate end face is a surface formed by physical processing.
9. The reinforced plate glass according to claim 1, wherein the
physical processing is any one of laser cutting and scribe
cleaving.
10. A method of manufacturing a reinforced plate glass, comprising
a compression reinforcement step of forming a compression stress
layer on a surface of a plate glass by chemical reinforcement and a
dividing step of applying a tensile stress to a plate surface of
the plate glass chemically reinforced by the compression
reinforcement step and dividing the plate glass, to thereby obtain
the reinforced glass according to claim 1.
11. The method of manufacturing a reinforced plate glass according
to claim 10, wherein a stress distribution in a plate thickness
direction of a compression stress layer of the plate surface is
limited in accordance with a compression stress function
represented by a compression stress value of the plate surface, a
thickness size of the compression stress layer, and a thickness
size of a region where a compressive force is not formed, due to
the compression reinforcement step.
12. The method of manufacturing a reinforced plate glass according
to claim 11, wherein the dividing step is conducted by any one of
laser cutting and scribing cleaving.
13. The method of manufacturing a reinforced plate glass according
to claim 12, wherein the scribing cleaving is conducted under a
force applying condition of from 0.5 to 1.5 kgf with respect to the
plate surface.
14. The method of manufacturing a reinforced plate glass according
to claim 12, wherein the scribing cleaving is conducted at a
scribing speed of from 10 to 1,000 mm/s.
15. The method of manufacturing a reinforced plate glass according
to claim 12, wherein the laser cutting is conducted by laser light
radiated by a carbon dioxide laser light source with an output of
from 10 to 100 W.
16. The method of manufacturing a reinforced plate glass according
to claim 11, wherein the laser cutting is conducted by operating
radiation light at a transfer speed of from 5 to 100 mm/s with
respect to a plate glass surface.
17. The reinforced plate glass according to claim 2, wherein a
stress distribution of the compression stress layer in a plate
thickness direction is limited in accordance with a compression
stress function represented by a compression stress value of the
plate surface, a thickness size of the compression stress layer,
and a thickness size of the region where a compression stress is
not formed.
18. The reinforced plate glass according to claim 3, wherein the
compression stress function is a function obtained by dividing a
product of the compression stress value and the thickness size of
the compression stress layer by the thickness size of the region
where a compression stress is not formed, and a value calculated by
the function is 40 MPa or less.
19. The reinforced plate glass according to claim 17, wherein the
compression stress function is a function obtained by dividing a
product of the compression stress value and the thickness size of
the compression stress layer by the thickness size of the region
where a compression stress is not formed, and a value calculated by
the function is 40 MPa or less.
20. The reinforced plate glass according to claim 2, wherein a
compression stress value of at least one of the plate surfaces is
in a range of from 200 to 1,500 MPa.
Description
TECHNICAL FIELD
[0001] The present invention relates to a plate glass used as a
substrate material or a cover glass member to be mounted on an
image display portion or an image input portion of various kinds of
portable information terminals typified by a mobile phone and a PDA
and an electronic appliance typified by a liquid crystal display,
and a method of manufacturing the plate glass.
BACKGROUND ART
[0002] In recent years, as recognized in the progress of a digital
technology involving all the industrial fields and the like, the
information industry has been developed remarkably, and the
prosperity thereof is presenting animated appearance in the same
way as in the textile industry, steel industry, shipbuilding
industry, or the like. Along with this, the technical innovation
regarding various kinds of information-related terminals is
expanding continuously, as in the increase in sales of mobile
appliances such as a mobile phone, a digital camera, and a PDA and
a large-type image display apparatus such as a liquid crystal
television. A transparent substrate for displaying information such
as images and characters or inputting information with a touch
panel display is mounted on such information-related terminals, and
the substrate adopts glass as a material so as to realize high
environment performance and ensure high reliability.
[0003] Various environment performances required for glass used for
the application shouldering the prosperity of the information
industry include various physicochemical performances such as
mechanical strength in conformity with the environment in which
glass is used, chemical resistance such as weather resistance, and
appropriate optical constants such as a transmittance and a
refractive index. Therefore, designing a glass material determines
an ultimate composition for solving all those problems. A secondary
treatment has been conducted with respect to glass so as to solve
the higher problems, which cannot be solved only by designing a
glass material. Examples of the secondary treatment include
physical reinforcement such as the adjustment of a refractive index
and a density, a slow cooling operation (which is also called
annealing) for maintaining strength, air-cooling reinforcement for
reinforcing a glass surface, and chemical reinforcement such as ion
exchange.
[0004] Of the secondary treatments, the chemical reinforcement of a
glass surface has been utilized for a glass product used for
various applications requiring reinforcement. Glass products to be
chemically reinforced cover a fairly broad spectrum, which includes
small things such as a cover glass for a watch such as a wristwatch
to large things such as a window plate glass. Further, a large
number of inventions have been carried out, which overcome weak
points caused when a chemical reinforcement method is conducted.
For example, regarding a problem in that the chemical reinforcement
method generally decreases the chemical durability of a glass
surface, Patent Document 1 discloses a method of soaking a float
plate glass in a potassium nitrate molten salt and further soaking
the glass in a lithium aqueous solution so as to produce a
chemically reinforced glass excellent in chemical durability.
Further, regarding a problem in that a plate glass used for the
application such as a touch panel is warped by chemical
reinforcement, Patent Document 2 discloses an invention which
solves the problem by changing the support position of the plate
glass while being soaked in a vertical direction for chemical
reinforcement with the ratio between the length of a long side and
the length of a short side of the plate glass. Further, regarding a
problem in that, for chemically reinforcing the entire plate glass,
the management of a heat treatment step should be conducted
strictly, particularly for treating a large-size plate glass such
as a display, which makes it difficult to shorten the time for the
step, Patent Document 3 discloses an invention solving the problem
by spraying an atomized reinforcing agent or a powdery reinforcing
agent to a cut portion of a glass plate and irradiating the cut
portion with light for heating. Further, Patent Document 4
discloses an invention in which a partial reinforcement treatment
of a glass plate used for a large display such as a plasma display
can be achieved by laminating a paste containing a potassium salt
and a high-melting point compound on a glass surface.
[0005] Patent Document 1: JP 07-223845 A
[0006] Patent Document 2: JP 2004-189562 A
[0007] Patent Document 3: JP 2006-282492 A
[0008] Patent Document 4: JP 2003-514758 A
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0009] However, only with the inventions which have been carried
out so far, it is difficult to realize a chemically reinforced
plate glass which has a high function and an excellent surface
property, can realize a high production efficiency, is used for the
applications such as various kinds of portable information
terminals. In the case of applying a chemical reinforcement method
such as ion exchange reinforcement, generally, a plate glass is
processed to a product shape size and thereafter is subjected to a
predetermined chemical treatment. However, according to such a
method, the plate glasses with a product size must be supported one
by one without the decrease in quality during the reinforcement
treatment. Therefore, there arises a problem in that a support
method and the like must be devised variously as disclosed in
Patent Document 2, or in that even a site that is not required to
have high strength as a plate glass product is reinforced because
the entire glass is treated in an ordinary reinforcement treatment.
Further, conducting a partial reinforcement treatment of a plate
glass by a spraying treatment or a paste treatment as in Patent
Document 3 or 4, instead of the entire reinforcement of a glass
plate, is excellent in that only a desired portion or site can be
reinforced. However, various precise and minute cares must be taken
in terms of the treatment facility, management technique, and the
like, and hence, there arises a problem that the production of a
reinforced plate glass requires much labor.
[0010] Further, although the surface of a glass article subjected
to chemical reinforcement is supplied with a compression stress, a
tensile stress is applied to a glass bulk inside thereof.
Therefore, it is difficult to appropriately subject the glass
article to the physical processing such as cutting and cleaving
which passes through or separates the glass article, after the
chemical reinforcement. If an attempt is made on the glass article
so as to conduct such processing forcefully, due to the tensile
stress inside the glass article, the glass article may be broken.
Alternatively, the glass article is not cut or cleaved at a desired
position and only a finished article with a low precision is
obtained, resulting in the problem with the production of a large
number of defective products. Further, there is a region where a
large tensile force is applied on the cut surface of the glass
article produced at a low efficiency percentage, and hence, an
alkali metal component such as sodium in glass is likely to be
deposited on the glass surface with time, which causes a problem in
the weather resistance of the glass.
[0011] Further, in the case of subjecting a plate glass to the
reinforcement, a plate glass is previously processed to a final
product size by utilizing a scribe break method using diamond or an
ultrahard alloy wheel chip, a dicer cut method using a diamond
wheel, a laser cut method using a laser, or the like. Then, it is
necessary to remove fine cracks and scratches present on the glass
surface by grinding for removing minute cracks generated on an end
face of the plate glass, polishing, and etching of the glass
surface using various agents such as hydrofluoric acids. However,
such steps increase labor for the production, and hence, there
remains a problem in that a reinforced plate glass cannot be
produced at high efficiency.
[0012] The present invention solves the above-mentioned various
problems, and an object of the present invention is to provide a
method of manufacturing an economically excellent reinforced plate
glass that is capable of reinforcing the strength of a glass
surface sufficiently and producing a reinforced plate glass of
stable quality at high production efficiency, and a reinforced
plate glass having a high size quality and stable surface strength,
obtained by the manufacturing method.
Means for Solving the Problems
[0013] A reinforced plate glass of the present invention is
characterized by being made of an inorganic oxide glass, and
comprising a compression stress layer formed by chemical
reinforcement on each of plate surfaces opposed to each other in a
plate thickness direction, and a region where a compression stress
is formed and a region where a compression stress is not formed on
a plate end face.
[0014] In the present invention, a plate glass whose composition
can be represented by an inorganic oxide conversion is supplied
with energy for increasing a density distribution of particular ion
species regarding the surface of the plate and a bulk in the
vicinity of the surface, whereby the atomic density of the plate
surface and the bulk in the vicinity of the surface is enhanced,
and as a result, a compression stress layer parallel to the plate
surface is formed. Further, the plate end face is provided with a
region where a compression stress is formed and a region where a
compression stress is not formed. Herein, the region where a
compression stress is not formed is more specifically a region with
a compression stress of 0 or a region where a tensile stress
acts.
[0015] On the plate end face, the region where a compression stress
is formed is connected to the plate surface, and the region where a
compression stress is not formed is connected to the region where a
compression stress is formed.
[0016] As a method for the chemical reinforcement of a plate glass,
for example, a low-temperature type ion exchange method, a
high-temperature type ion exchange method, a surface
crystallization method, or a dealkalization method may be adopted
appropriately, if required, and a plurality of methods may be used
together. In terms of the economical viewpoint, the low-temperature
type ion exchange method and the dealkalization method are
preferred, and the low-temperature type ion exchange method is more
preferably adopted.
[0017] The plate end face is preferably a surface formed by
physical processing. Herein, the physical processing refers to the
processing of applying a mechanical stress to the surface of glass,
such as cutting, trimming, and grinding. For example, when a plate
glass on the surface of which a compression stress layer is formed
by chemical reinforcement is divided by cutting, the plate end face
formed of the cut surface has a region where a compression stress
is formed and a region where a compression stress is not formed.
The region where a compression stress is not formed is, in other
words, the surface not subjected to the above chemical
reinforcement.
[0018] Note that as an apparatus used for the cutting, a peripheral
blade cutting apparatus, an internal blade cutting apparatus, a
bandsaw, a wiresaw, a laser cutting apparatus, a scribe cleaving
apparatus, or the like can be adopted.
[0019] As the shape of the plate end face, various shapes can be
adopted depending upon the use and purpose of the plate glass.
Examples of the shape of the plate end face include not only a flat
face orthogonal to the plate surface, but also an inclined surface
inclined with respect to the plate surface, a curved surface, an
uneven surface, a polygonal surface, or a combined shape
thereof.
[0020] Further, any outer appearance shape of the plate surface,
any size thereof, and any plate thickness can be adopted as long as
required strength performance is satisfied. For example, as the
outer appearance shape of the plate surface, not only a rectangle,
but also a circle, an oval, or a polygon such as a triangle, a
pentagon, or a hexagon can be used. Further, in the case of a shape
assuming an angular outer appearance, various shapes may be adopted
for a corner portion of the plate surface. For example, a C-surface
(corner-cutoff, also called corner cut), an R-surface, an inverse
R-surface, hollowing-out, a notch, etc. may be used. The C-surface
is a shape in which a corner is cut linearly. The R-surface is a
shape in which a corner is cut as if it looks curved outside of the
plate glass in a convex shape. The inverse R-surface is a shape in
which a corner is cut as if it looks curved inside of the plate
glass. The hollowing-out is a shape in which a corner is cut in a
substantially U-shape or a semi-circular shape. The notch is a
shape in which a corner is cut in a linear shape, i.e., an L-shape
by a predetermined length on one side from the apex of the corner
and by a predetermined length on the other side from the apex of
the corner. Further, if required, fine chamfering may be performed.
Regarding the size of the plate surface, the outside dimension of
the order of mm to the order of m may be adopted. Regarding the
plate thickness, various plate thicknesses of from 0.05 mm to 10 mm
can be used. In the case where reinforcement needs to be performed
or in the case of forming a thin plate glass to be mounted on a
precision appliance, an electronic appliance, etc., the reductions
in weight, thickness, length, and size are desired. Therefore, from
this point of view, the plate thickness is preferably in a range of
from 0.05 to 2 mm, more preferably in a range of from 0.06 mm to
1.5 mm, still more preferably in a range of from 0.07 mm to 1.4 mm,
and further preferably in a range of from 0.08 to 0.6 mm.
[0021] Further, if the region where a compression stress is formed
on the plate end face is distributed in parallel to the plate
surface, in addition to the above, the reinforced plate glass of
the present invention can realize desired strength of the plate
surface and have highly stable mechanical strength.
[0022] As described above, on the plate end face, the region where
a compression stress is formed is connected to the plate surface,
and the region where a compression stress is not formed is
connected to the region where a compression stress is formed.
Therefore, on the plate end face, the region where a compression
stress is not formed is sandwiched by the regions where a
compression stress is formed from both the plate surface sides.
With such a configuration, the reinforce plate glass can have
stable performance in the strength of the plate end face, as well
as the strength of the plate surface.
[0023] As a material for glass constituting the reinforced plate
glass of the present invention, a glass material suitable for a
chemical reinforcement method to be applied and an application can
be selected appropriately from inorganic oxide glasses. For
example, various kinds of inorganic glass materials such as
borosilicate glass and aluminosilicate glass may be used. Further,
if required, if a chemical reinforcement method to be applied is
limited, crystallized glass, lead glass, or the like can be used.
In the case where the reinforced plate glass is to be mounted on a
precision appliance, an electronic appliance, etc., a glass
material whose weather resistance decreases is not preferred. If a
glass composition range is specifically limited, a general glass
material, other than common soda-lime glass, whose Al.sub.2O.sub.3
content in a glass composition represented by an oxide conversion
is less than 10% in a mass percentage is preferred. When the
content of Al.sub.2O.sub.3 is 10% or more, even if a component that
decreases the weather resistance, such as sodium and potassium, is
contained, the effect of suppressing the decrease in weather
resistance in the region where a compression stress is not formed
on the plate end face becomes remarkably large.
[0024] The inventors of the present invention paid attention to the
following: in the case where it is not necessary to reinforce a
site which is not required to be reinforced chemically or in the
case where a particular surface of a plate glass should not be
subjected to chemical reinforcement due to the problems in terms of
the production, the application, etc. caused by the chemical
reinforcement, if a large plate glass can be cut after being
ion-exchanged previously by adopting physical processing such as
cutting, an unnecessary facility and the number of management items
to be required for the chemical reinforcement are reduced to
enhance the production efficiency remarkably, and the application
range of the chemical reinforcement can be enlarged substantially.
Then, the inventors of the present invention conducted various
studies from the above point of view and found the following: in
the case where particular reinforcement conditions are satisfied, a
plate glass which is chemically reinforced previously can be
processed satisfactorily even during cutting, is not damaged or
broken when a tensile stress is applied to the glass, and further,
after the cutting, the plate glass has sufficiently high strength
performance. Such particular conditions are related to the stress
state of the plate glass and can be realized by appropriately
managing the mutual relationship between main values involving in
some stress states.
[0025] More specifically, according to the reinforced plate glass
of the present invention, in addition to the above, if the stress
distribution in a plate thickness direction of a compression stress
layer is limited in accordance with a compression stress function
represented by a compression stress value of a plate surface, a
thickness size of the compression stress layer, and the thickness
size of the region where a compression stress is not formed, even
in the case where an external force for physical processing is
applied to the chemically reinforced plate glass, minute cracks and
chipped portions which degrade remarkably the strength of glass are
not generated on the physically processed surface of the plate
glass, and thus, the processed reinforced plate glass has a
processed surface of high quality.
[0026] Further, according to the reinforced plate glass of the
present invention, in addition to the above, if the compression
stress function is a function of dividing the product of a
compression stress value and the thickness size of the compression
stress layer by the thickness size of the region where a
compression stress is not formed, and the value calculated by the
function is 40 MPa or less, the surfaces opposed in the plate
thickness direction of the reinforced plate glass are reinforced
sufficiently. Further, even if a physical external force for
forming an end face of a plate glass is applied to the plate glass,
the plate glass is unlikely to be chipped or defects such as cracks
are unlikely to be generated.
[0027] Herein, when the compression stress function is defined as
F, the compression stress value is defined as P, the thickness size
of the compression stress layer is defined as T, and the thickness
size of the region where a compression stress is not formed is
defined as L, they can be represented by the following Equation
1.
F = P T L .ltoreq. 40 MPa [ Equation 1 ] ##EQU00001##
[0028] In order to obtain the compression stress function F
specifically, it is necessary to measure the compression stress
value P, the thickness size of the compression stress layer T, and
the thickness size of the region where a compression stress is not
formed L, respectively. First, the compression stress value P and
the thickness size of the compression stress layer T can be
measured, for example, using a surface stress meter adopting a
refractive index measuring method among a number of measuring
methods of stress. Further, the thickness size of the region where
a compression stress is not formed L can be calculated by Equation
2, because the thickness size of the opposed plate surfaces is the
same when the thickness size of the compression stress layer T and
the thickness size of the plate glass are sufficiently small. In
Equation 2, X represents the plate thickness size of the plate
glass. The plate thickness size X of the plate glass can be
measured using a calibrated measurement appliance such as a
microgauge or a laser measuring apparatus.
L=X-2T [Equation 2]
[0029] More specifically, Equation 1 may be expressed as Equation 3
by substituting Equation 2 into Equation 1.
F = P T X - 2 T .ltoreq. 40 MPa [ Equation 3 ] ##EQU00002##
[0030] Further, in the case where the plate thickness of a plate
glass is large, or in the case where it is necessary to provide
compression stress layers having different thickness sizes on the
plate surfaces intentionally, Equation 4 may be adopted. In
Equation 4, T1 and T2 represent thickness sizes of the compression
stress layers with respect to the respective plate surfaces opposed
to each other.
F = P T X - ( T 1 + T 2 ) .ltoreq. 40 MPa [ Equation 4 ]
##EQU00003##
[0031] The compression stress function F of a reinforced plate
glass can be calculated by a measured value before the plate glass
is subjected to physical processing. In the case of actually
producing a reinforced plate glass under predetermined conditions
following the compression stress function F, reinforcement
conditions to be conducted with respect to the plate glass are
varied depending upon various facilities to be used for
reinforcement. Therefore, it is necessary to set optimum production
conditions such as temperature and time by previously setting the
production conditions by the above-mentioned Equations 1 to 4.
Further, in the case of performing a coating treatment using an
organic resin, an inorganic material, and the like on the plate
surface of the plate glass before the physical processing, it is
necessary to make evaluations considering the influence caused by
the coating treatment.
[0032] In the case where the compression stress function F is 40
MPa or less, the resulting tensile stress acting inside the plate
glass does not exceed an allowable value. Therefore, unintended
extending cracks are not generated during the physical processing,
and hence, stable processing can be realized. When the compression
stress function F exceeds 40 MPa, for example, in the case where
the reinforced plate glass is subjected to cutting as the physical
processing, unintended cracks are likely to be generated in a
direction deviated from the cutting direction. When the tensile
stress is too large, crack fractures move rapidly in the reinforced
plate glass, and the plate glass may exhibit a state in which it is
ruptured momentarily. Even in the case where the compression stress
function F of the reinforced plate glass slightly exceeds 40 MPa,
the occurrence frequency of unintended cracks may become large
rapidly, decreasing the processing yield of the plate glass, which
is not preferred.
[0033] Further, in addition to the above, if the compression stress
of at least one surface of the opposed plate surfaces is in a range
of from 200 to 1,500 MPa, the reinforced plate glass of the present
invention can exhibit sufficient strength performance even in the
case of the use for various kinds of information terminals.
[0034] When the compression stress value of the plate surface of
the plate glass is 200 MPa or more, the plate glass exhibits
sufficient mechanical strength, compared with unreinforced glass.
On the other hand, when the compression stress value exceeds 1,500
MPa, the value of a tensile stress generated due to the compression
stress generated on the plate surface becomes too large during the
physical processing of the plate end face. As a result, the
physical processing is unlikely to be performed smoothly. For
example, when an attempt is made so as to perform cutting, minute
cracks are generated in a direction different from the cutting
direction. When the tensile stress is much larger, cracks extend
rapidly in an unintended direction according to the tensile stress,
and as a result, glass may be crushed. Further, as the thickness of
the compression stress layer is larger, the tensile stress value
increases, and similarly, the physical processing becomes
difficult. For example, in the case of adopting a scribe cutting
method as the cutting method of a plate glass, when the thickness
of a compression stress layer exceeds 100 .mu.m, cracks extending
from the tip end of a scratch are not formed easily due to the
compressive force during the formation of cut lines (scratches,
scribe lines) with a predetermined depth in the cutting portion of
the plate surface by a wheel chip, and troubles may be caused in
the scribe processing. From the above point of view, the
compression stress value of the plate surface of a plate glass is
preferably 200 to 1,500 MPa, and the thickness of the compression
stress layer is preferably 100 .mu.m or less. Then, the compression
stress value is more preferably in a range of from 500 to 1,100
MPa. The thickness size of the compression stress layer is more
preferably 40 .mu.m or less.
[0035] Further, in addition to the above, if an average breaking
stress is measured to be 400 MPa or more by a four-point bending
test according to JIS R1601 (1995), and a Weibull coefficient
according to JIS R1625 (1996) is 3 or more, sufficiently highly
stable strength can be realized, compared with an unreinforced
plate glass.
[0036] Herein, the Weibull coefficient being 3 or more means the
following: a glass test chip having a surface roughness of 0.20.mu.
Ra or less according to JIS B0601 with a total length of 36 mm or
more is produced in accordance with the Japanese Industrial
Standards defined as "Bending Strength Test Method of Fine
Ceramics" (JIS R1601) in 1995, and an indenter is lowered onto the
test chip under a condition of a crosshead speed of 0.5 mm/min. to
measure a four-point bending strength, whereby an average breaking
stress value of an arithmetic average can be obtained; further, the
measurement result of the strength is placed on a Weibull plot in
accordance with the Japanese Industrial Standards defined as
"Wiebull Statistical Analysis of Strength Data of Fine Ceramics"
(JIS R1625) in 1996, and a Wiebull coefficient obtained from the
gradient thereof is 3 or more. The Wiebull coefficient shows the
stability of measurement results, and a larger Wiebull coefficient
shows a more stable measurement result. It is not preferred that
this value be less than 3, because the reliability on the strength
performance of a reinforced plate glass is low.
[0037] In addition to the above, if the reinforced plate glass of
the present invention contains 50 to 80% of SiO.sub.2, 0 to 15% of
B.sub.2O.sub.3, 3 to 25% of Al.sub.2O.sub.3, 0 to 20% of Li.sub.2O,
0 to 20% of Na.sub.2O, 3 to 25% of Li.sub.2O+Na.sub.2O, 0 to 20% of
K.sub.2O, 0 to 10% of CaO+MgO+ZnO+SrO+BaO, and 0 to 10% of
TiO.sub.2+ZrO.sub.2, the reinforced plate glass can have high
strength by selecting an appropriate chemical reinforcement such as
a low-temperature ion exchange method.
[0038] The reason for limiting the content of each component
constituting the reinforced plate glass of the present invention is
described below.
[0039] A SiO.sub.2 component forms the network of a glass structure
in the atomic arrangement order, and is a main constituent of the
glass structure. As the content of the SiO.sub.2 component in a
glass composition increases, the strength of the glass structure
becomes high, and the chemical durability of the glass tends to
increase. On the other hand, when the content of the SiO.sub.2
component increases, the viscosity of molten glass in a high
temperature region becomes too high, which makes it difficult to
mold glass, and hence, there arises a constraint in the glass
production such as the necessity to use an expensive facility. From
the above point of view, when the content of the SiO.sub.2
component is less than 50% by mass, the chemical durability of the
molded plate glass becomes poor. On the other hand, it is not
preferred that the content of the SiO.sub.2 component exceeds 80%
by mass, because various problems arise in terms of a facility, a
production efficiency, and the like for melting glass
homogeneously. Therefore, the content of the SiO.sub.2 component is
preferably in a range of from 50 to 80% by mass, more preferably in
a range of from 60 to 80% by mass, and still more preferably in a
range of from 60 to 70% by mass.
[0040] A B.sub.2O.sub.3 component is one of the components to be a
network structure of a glass structure similarly to the SiO.sub.2
component, and functions as a flux during melting of glass.
However, when the content of the B.sub.2O.sub.3 component increases
too much, the mobility of an alkali metal element component in
solid glass decreases, for example, in the case of an ion exchange
is conducted, with the result that the ion exchangeability may be
decreased. Therefore, the content of the B.sub.2O.sub.3 component
is preferably 15% by mass as an upper limit value, and more
preferably at most 12% by mass.
[0041] An Al.sub.2O.sub.3 component facilitates the movement of an
alkali metal element component in a glass structure, for example,
in the case where an ion exchange is conducted, and also has a
function of stabilizing the chemical durability of glass.
Therefore, when the content of the Al.sub.2O.sub.3 component in
glass is less than 3% by mass, there may be trouble for the
chemical durability of glass, and the ion exchangeability may be
decreased. On the other hand, when the content of the
Al.sub.2O.sub.3 component in glass exceeds 25% by mass, the
viscosity of molten glass during melting of glass becomes too high.
Therefore, in order to obtain homogeneous plate glass, the upper
limit of the content of the Al.sub.2O.sub.3 component is preferably
set to be 25% by mass. As described above, the content of the
Al.sub.2O.sub.3 component in glass is preferably in a range of from
3 to 25% by mass, and more preferably in a range of from 5 to 23%
by mass. Further, in the case where the reinforced plate glass of
the present invention is a thin plate glass to be mounted on a
precision appliance, an electronic appliance, or the like, in order
to obtain satisfactory weather resistance in a region where a
compression stress of a plate end face is not formed, the content
of the Al.sub.2O.sub.3 component is preferably in a range of from
10 to 25% by mass, more preferably in a range of from 10.1 to 23%
by mass, still more preferably in a range of from 11 to 22.8% by
mass, and most preferably in a range of from 12 to 22.8% by
mass.
[0042] Both a Li.sub.2O component and a Na.sub.2O component have
functions of decreasing the viscosity of molten glass and
increasing the thermal expansion coefficient of glass. For example,
in the case where ion exchange reinforcement is conducted, the ion
exchange with K.sup.+ions with an ion radius larger than that of
ions (Na.sup.+and Li.sup.+) is conducted, whereby the density of a
glass structure is increased and consequently, a compression stress
acts. Therefore, the Li.sub.2O component and the Na.sub.2O
component are indispensable for adopting such a reinforcement
method. Thus, in order to exactly realize such functions in the
glass structure, the total amount of the Li.sub.2O component and
the Na.sub.2O component is preferably 3% by mass or more. However,
it is not preferred that each amount of the Li.sub.2O component and
the Na.sub.2O component be 20% by mass or more as a glass component
because the thermal expansion coefficient of glass becomes too
high, crystal is likely to be precipitated in molten glass, and
defects are likely to be generated due to the devitrification of
molten glass. It is also not preferred that the total amount of the
Li.sub.2O component and the Na.sub.2O component be 25% by mass or
more, because the chemical durability may be decreased. Thus, the
total amount of the Li.sub.2O component and the Na.sub.2O component
is preferably 3 to 25% by mass from the above point of view.
Further, it is more preferred that each of the contents of the
Li.sub.2O component and the Na.sub.2O component be from 0 to 15% by
mass, and the total amount thereof is more preferably from 3 to 15%
by mass.
[0043] A K.sub.2O component does not function so largely as the
Li.sub.2O component and the Na.sub.2O component; however, the
K.sub.2O component decreases the viscosity of molten glass in the
same way as in the Li.sub.2O component and the Na.sub.2O component
and increases the thermal expansion coefficient of glass. The
K.sub.2O component may also suppress the devitrification caused by
the Li.sub.2O component and the Na.sub.2O component. However, it is
not preferred that the K.sub.2O component be contained in a glass
composition in an amount of 20% by mass or more, because crystal
caused by the K.sub.2O component is likely to be precipitated in
molten glass, which may cause defects of glass due to
devitrification. From this point of view, the K.sub.2O component is
preferably in a range of from 0 to 20% by mass and more preferably
in a range of from 0 to 10% by mass in a glass composition.
[0044] A CaO component, a MgO component, a ZnO component, a SrO
component, and a BaO component each have a function of decreasing
the viscosity of molten glass. When the total amount of these
components exceeds 10% by mass, the chemical reinforcement may be
interfered for the following reason. For example, in the case of
ion exchange reinforcement, these components decrease the mobility
of ions in glass. From the above point of view, the total amount of
the CaO component, the MgO component, the ZnO component, the SrO
component, and the BaO component is preferably at most 10% by mass
and more preferably at most 8% by mass.
[0045] A TiO.sub.2 component and a ZrO.sub.2 component have a
function of promoting the chemical reinforcement, and in addition,
they improve the weather resistance of glass. When the TiO.sub.2
component and the ZrO.sub.2 component are contained in glass in a
large amount, the function of enhancing the devitrification
tendency of glass becomes remarkable. Therefore, the total amount
of the TiO.sub.2 component and the ZrO.sub.2 component is more
preferably 2% or more, and is preferably at most 10% by mass, more
preferably at most 6% by mass, and most preferably at most 5% by
mass.
[0046] In addition to the above, in the reinforced plate glass of
the present invention, various kinds of components can be added to
a glass composition, if required, in such a range as not to largely
influence the performance including the strength performance, the
chemical durability required in terms of an application, the
viscosity during melting of glass, the devitrification resistance,
and the like. Specific examples of the constituent components that
can be used for the reinforced plate glass of the present invention
include P.sub.2O.sub.5, Fe.sub.2O.sub.3, SnO.sub.2,
Sb.sub.2O.sub.3, As.sub.2O.sub.3, SO.sub.2, Cl.sub.2, F.sub.2, PbO,
La.sub.2O.sub.3, WO.sub.3, Nb.sub.2O.sub.5, Y.sub.2O.sub.3,
MoO.sub.3, rare-earth oxides, and lanthanoide oxides, which may be
contained in the glass composition as long as the content thereof
is 3% or less in percent % by mass representation.
[0047] Further, in addition to the above, other components can be
contained in the glass composition in an amount of up to 0.1% in
percent % by mass representation. Examples of the other components
include various kinds of trace amount of components such as OH,
H.sub.2, SO.sub.3, CO.sub.2, CO, H.sub.2O, He, Ne, Ar, and
N.sub.2.
[0048] Further, the reinforced plate glass of the present invention
may contain a trace amount of noble metal elements as long as they
do not largely influence the performance of the reinforced plate
glass. For example, the reinforced plate glass may contain platinum
elements such as Pt, Rh, and Os up to the order of ppm.
[0049] In addition to the above, if the physical processing is any
of laser cutting and scribe cleaving, the production efficiency of
the reinforced plate glass of the present invention can be
enhanced; therefore, a reinforced plate glass of excellent quality
can be supplied in a large amount to customers.
[0050] In addition to the above, the reinforced plate glass of the
present invention may be provided with various kinds of functional
coating films on the plate surface. Examples of the functional
coating film include a thin film and a coating for ensuring the
function as a protective film with respect to an external force
applied to the surface of glass and optical performance, and a
functional coat such as a conductive film required in a touch
panel. Of those, an indium tin oxide (ITO) film, a reflection
prevention film, and the like formed by sputtering can be used
particularly.
[0051] A method of manufacturing a reinforced plate glass of the
present invention comprises a compression reinforcement step of
forming a compression stress layer on a surface of a plate glass by
chemical reinforcement and a dividing step of applying a tensile
stress to a plate surface of the plate glass chemically reinforced
by the compression reinforcement step and dividing the plate glass,
thereby obtaining the reinforced glass.
[0052] The compression reinforcement step is the step of enhancing
the structure density of the plate surface of a plate glass and a
bulk in the vicinity thereof. For example, in the case where ion
exchange reinforcement is conducted, the compression reinforcement
step represents the processing step of conducting various
enforcements such as the step of soaking a plate glass in a heated
molten salt to conduct ion exchange, the step of conducting a heat
treatment while keeping a heat-resistant medium such as a ceramics
non-woven fabric impregnated with a paste or a drug in contact with
the plate glass, and the step of spraying a drug onto only one
surface of the opposed plate surfaces of the plate glass and
heating the plate glass while holding it horizontally with the
sprayed surface directed upward.
[0053] Further, the dividing step is the step of dividing one
reinforced plate glass into at least two plate glasses, and a
specific operation to be conducted with respect to the reinforced
plate glass for dividing is not limited. Examples of a cutting
method of dividing the reinforced plate glass include a method of
cutting by one operation such as a scribe break method and a method
requiring at least two operations in which a scribe line is formed
with a scribe or the like and thereafter, an bending operation is
conducted. In addition, various kinds of methods such as a
peripheral cutting method, an internal cutting method, a bandsaw
method, a wiresaw method, a laser cutting method, a trimming
method, and a blast processing method may be adopted
appropriately.
[0054] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, more specifically,
the compression reinforcement step includes a reinforcement
condition setting step which is conducted for the purpose of
previously determining the compression stress function F before the
compression reinforcement and an appropriate stress applying step
of conducting compression reinforcement under the condition of
satisfying the appropriate compression stress function F.
[0055] The reinforcement condition setting step is conducted for
the purpose of setting a processing temperature condition and a
processing temperature time so as to set appropriate processing
conditions, considering various factors such as the processing
ability of an actual processing facility, human labor, or various
conditions occurring during the process. In this step, a previously
prepared glass sample chip is used, and whether or not the
reinforcement conditions thereof satisfy the compression stress
function F and a product to be obtained realizes sufficiently high
strength are confirmed, whereby the reinforcement conditions are
set. Then, chemical reinforcement is conducted during the
appropriate stress applying step in accordance with the various
conditions determined in the reinforcement condition setting step,
whereby a plate glass having desired stable strength can be
produced.
[0056] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, it is preferred that the stress distribution in a plate
thickness direction of the compression stress layer of the plate
surface be limited during the compression reinforcement step in
accordance with the compression stress function represented by the
compression stress value of a plate surface, the thickness size of
a compression stress layer, and the thickness size of a region
where a compression stress is not formed, because the possibility
that a plate glass is broken by the inside tensile stress present
in the plate glass decreases, and hence, stable processing can be
conducted, which enhances the production efficiency. Further, it is
preferred that the compression stress function be a function
obtained by dividing the product of a compression stress value and
a thickness size of a compression stress layer by the thickness
size of a region where a compression stress is not formed, and the
value calculated by the function is 40 MPa or less.
[0057] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, if the diving step is conducted by any of laser cutting and
scribe cleaving, the processing loss as a material for a plate
glass can be reduced, and the processing techniques accumulated so
far can be utilized, and hence, the dividing step can be conducted
under stable conditions.
[0058] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, the cutting in the dividing step may not include a breaking
step.
[0059] Herein, "breaking" does not refer to cutting of a plate
glass only by initial processing with a laser or a wheel chip, but
refers to dividing of a plate glass by applying a stress so that a
tensile stress can be concentrated on a scratch or a crack line
formed in glass after the initial processing. According to such a
processing method, the number of steps increases accordingly;
however, in the present invention, such a breaking step is omitted
to decrease the number of steps, whereby the problem of the
contamination of glass due to glass powder generated during
breaking and the problem of lacking or chipping occurring in a
plate glass can be avoided.
[0060] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, if the scribe cleaving is conducted under the condition of
an application of from 0.5 to 1.5 kgf on the plate surface,
appropriate cutting can be conducted without providing an overload
on the reinforced plate glass, and hence, conditions preferable for
various plate glass thicknesses can be adopted.
[0061] When the force application condition by a wheel chip or the
like during scribe cleaving is smaller than 0.5 kgf, the function
against a compressive force of the reinforced plate surface is not
exhibited, and median cracks perpendicular to the plate surface do
not extend into a glass bulk. On the other hand, it is not
preferred that the force application condition by a wheel chip or
the like during scribe cleaving exceed 1.5 kgf, because the
overload conditions caused by such force application condition lead
to a number of lateral cracks parallel to the reinforced plate
glass and microcracks following the lateral cracks in addition to
median cracks generated along with scribing, and the glass end face
after cleaving does not become a clear surface state. From the
above point of view, the force application condition with a wheel
chip or the like during scribe cleaving is preferably from 0.8 to
1.1 kgf and more preferably from 1.0 to 1.1 kgf.
[0062] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, if the scribe cleaving is conducted at a cleaving speed of
from 10 to 1,000 mm/s, the reinforced plate glass can be produced
at a high processing speed, and hence, reinforced plate glasses of
excellent quality can be supplied to the market in a large
amount.
[0063] Herein, the cleaving speed refers to a head speed of an
indenter such as a wheel chip for scribing.
[0064] It is not preferred that the cleaving speed for scribe
cleaving be lower than 10 mm/s, because the productivity is
decreased, and in addition, median cracks generated by scribing do
not proceed normally due to the tensile stress inside the
reinforced plate glass. Further, when the cleaving speed for scribe
cleaving is higher than 1,000 mm/s, the force applied from the
wheel chip is not propagated sufficiently, and therefore, the
growth of cracks is prevented by the compressive force of the
reinforced plate glass surface, and median cracks extending in a
direction perpendicular to the plate glass surface cannot extend to
a sufficient depth. From the above point of view, the cleaving
speed for scribe cleaving is more preferably from 10 to 500 mm/s,
still more preferably from 10 to 300 mm/s, still more preferably
from 10 to 100 mm/s, still more preferably from 20 to 80 mm/s, and
most preferably from 40 to 80 mm/s.
[0065] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, if the cutting edge angle of a wheel chip is in a range of
from 90.degree. to 150.degree., the transfer of the cutting edge of
the wheel chip becomes smooth with respect to the reinforced plate
surface.
[0066] In the case where the cutting edge angle of the wheel chip
is less than 90.degree., the tip end of the wheel chip causes a
strong stress only locally on the glass surface, and as a result,
the insertion speed of the wheel chip into glass becomes higher
than the propagation speed of median cracks extending in a
direction perpendicular to the plate surface, and hence, a cut
cross-section involved in the normal extension of cracks may not be
formed. On the other hand, it is not preferred that the cutting
edge angle of the wheel chip exceed 150.degree., because it becomes
difficult to apply a sufficient tensile stress to the plate surface
having a compression stress. From the above point of view, the
cutting edge angle of the wheel chip is preferably in a range of
from 100.degree. to 145.degree., more preferably in a range of from
100.degree. to 140.degree., and further preferably in a range of
from 115.degree. to 130.degree..
[0067] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, it is preferred that the laser cutting can be conducted by
laser light radiated from a carbon dioxide laser light source with
an output of from 10 to 100 W, because unnecessary load will not be
applied to the end face of the cut plate glass to cause minute
cracks due to the appropriate range of the output conditions.
[0068] It is not preferred that the output range of a CO.sub.2
laser be lower than 10 W, because median cracks with a sufficient
depth cannot be formed on the plate surface, which may cause
trouble to a cutting operation. On the other hand, it is not
preferred that the output range of the CO.sub.2 laser exceed 100 W,
because the overload state causes the glass end face to be softened
and deformed easily. From the above point of view, the output range
of the CO.sub.2 laser is preferably in a range of from 10 to 40
W.
[0069] Further, according to the method of manufacturing a
reinforced plate glass of the present invention, in addition to the
above, if the laser cutting can be conducted by operating radiation
light at a transfer speed of from 5 to 100 mm/s with respect to the
plate surface, plate glasses under various reinforcement conditions
can be cut smoothly.
[0070] It is not preferred that the moving speed of laser light on
the reinforced plate glass surface be lower than 5 mm/s, because
the plate surface is overheated, and a softening phenomenon and the
like of glass are recognized. On the other hand, when the moving
speed of laser light on the plate surface exceeds 100 mm/s, damages
sufficient for resisting a compression stress cannot be given to
the reinforced plate surface, which makes the cutting difficult.
From the above point of view, the moving speed of laser light on
the plate surface is more preferably in a range of from 5 mm/s to
25 mm/s.
EFFECTS OF THE INVENTION
[0071] As described above, according to the present invention, a
high production efficiency can be realized in the production of a
reinforced plate glass, and a reinforced plate glass of high outer
appearance quality can be provided, in which the strength of plate
glass surfaces opposed to each other in a plate thickness direction
can be increased, and surface defects such as chipping are not
present on an end face.
BEST MODE FOR CARRYING OUT THE INVENTION
[0072] Hereinafter, a reinforced plate glass of the present
invention and a method of manufacturing the reinforced plate glass
are described by way of examples.
Example 1
[0073] FIG. 1 is a perspective explanatory view of a reinforced
plate glass of the present invention. The plate glass has a
composition of 65.4% of SiO.sub.2, 22.0% of Al.sub.2O.sub.3, 4.2%
of Li.sub.2O, 0.5% of Na.sub.2O, 4.7% of Li.sub.2O+Na.sub.2O, 0.3%
of K.sub.2O, 1.5% of BaO, 2.0% of TiO.sub.2, 2.2% of ZrO.sub.2,
1.4% of P.sub.2O.sub.5, and 0.5% of As.sub.2O.sub.3 in percent % by
mass of an oxide conversion.
[0074] A reinforced plate glass 10 is used for a transparent
display panel to be mounted on a precision appliance, an electronic
appliance, and the like such as a touch panel, a mobile telephone,
and a mobile information terminal appliance. Therefore, it is
necessary to reinforce only plate surfaces 11, 12 opposed to each
other in a plate thickness direction, and further, a production
efficiency needs to be enhanced. Therefore, the reinforced plate
glass 10 is produced by soaking a parent plate glass having a large
outer size of 500 mm (vertical size).times.500 mm (horizontal
size).times.2 mm (plate thickness size) molded and ground by a
roll-out method in a potassium nitrate molten salt with a
temperature state managed as the compression reinforcement step,
thereby conducting low-temperature ion exchange, washing off the
potassium nitrate after the processing, followed by drying, and
cleaving the glass at a cleaving speed of 50 mm/s under the
application load condition of 1.05 kgf of a wheel chip, using a
scribe apparatus having a ultra-steel wheel chip with a cutting
edge angle of 125.degree. as the dividing processing step.
[0075] In this example, corners of plate surfaces 11, 12 (borders
between plate surfaces 11, 12 and plate end faces 12, 13, 14, and
15) are not particularly processed, but if required, may be
subjected to a C-surface cut or an R-surface cut.
[0076] In the reinforced plate glass 10, the plate surfaces 11, 12
are each reinforced when the reinforced plate glass 10 is soaked in
a potassium nitrate bath and potassium ions in the bath diffuse to
a glass bulk in the vicinity of the surface. On the other hand, the
four plate end faces 13, 14, 15, and 16 of the reinforced plate
glass 10 are processed surfaces formed by scribing, and hence, a
part of the regions is not reinforced. More specifically, the plate
end faces 13, 14, 15, and 16 include regions where a compression
stress is formed and regions where a compression stress is not
formed. Further, in the plate end faces 13, 14, 15, and 16, the
regions where a compression stress is formed are each distributed
in parallel with the plate surfaces 11 and 12. The scribing is
performed under appropriate conditions, whereby the plate surfaces
11 and 12 can be cut smoothly even if they are reinforced. Further,
in the reinforced plate glass 10, ion exchange is conducted in a
condition so that processing can be performed without causing
unintended defects such as cracks on the plate surfaces 11, 12, and
the stress distribution in a plate thickness direction is
optimum.
[0077] Under the ion exchange processing conditions of the
reinforced plate glass 10, the conditions such as the processing
index and the capacity of a potassium nitrate molten salt, and the
temperature management method are considered as the reinforcement
condition setting step, the processing conditions set by making
evaluations for setting a processing condition temperature and a
processing time, i.e., the appropriate processing conditions of
500.degree. C. and 2 hours are set, and the parent plate glass
molded and ground by the roll-out method as described above is
reinforced in the appropriate stress applying step, using the
setting conditions. In the setting of the processing conditions,
the compression stress function F obtains a value of 20.0 MPa,
defining the product of 870 MPa and 11 .mu.m as a numerator and
defining the value obtained by subtracting a value, which is
obtained by multiplying 11 .mu.m by 2, from 0.5 mm (i.e., 500
.mu.m), and is previously set to be 40 MPa or less.
[0078] FIG. 2 exemplifies a stress distribution formed by
reinforcement, regarding plate surfaces S opposed to each other in
a plate thickness direction. As is apparent from FIG. 2, an optimum
compression stress C is formed on the plate surfaces S and in the
vicinity thereof by reinforcement, and on the other hand, a tensile
stress T acts in the vicinity of the center of a glass bulk B that
is an inner region.
[0079] FIG. 3 shows a stress distribution of a plate end face of a
plate glass formed by scribing. On the plate end face 13,
compression stress regions J are formed so as to be in parallel
with the borders between the plate surfaces 11, 12, opposed to each
other in a plate thickness direction, and the plate end face 13,
and a region U where a compression stress is not formed is present
so as to be sandwiched by the compression stress regions J.
[0080] More specifically, the ion exchange conditions are as
follows: in the case of producing the reinforced plate glass of the
present invention, by previously setting the conditions matched
with a facility for reinforcement, the compression stress
distribution in a plate thickness direction is limited in
accordance with a compression stress function F represented by a
compression stress value P, a thickness size T of a compression
stress layer, and a thickness size L of a region where a
compression stress is not formed. More specifically, the
compression stress function F is represented by the function
obtained by dividing the product of the compression stress value P
and the thickness size T of a compression stress layer by the
thickness size L of a region where a compression stress is not
formed, and the value calculated by the function is set to be 40
MPa or less.
[0081] Therefore, in order to obtain the compression stress value P
of the plate surface of 870 MPa and the thickness size T of a
compression stress layer of 11 .mu.m, the temperature of potassium
nitrate molten salt is previously managed to be 500.degree. C. as
an ion exchange condition and the time required for reinforcing a
plate glass is set to be 2 hours in the reinforced plate glass 10.
In the reinforced plate glass, the reinforced plate glass is not
broken during the processing such as scribing, can be processed
easily, and can be subjected to processing without the breaking
step. Therefore, the problem of contamination of glass with glass
powder generated during breaking and the lacking generated in the
plate glass, i.e., the problem of chipping can be avoided.
[0082] Further, the plate end face of the reinforced plate glass 10
have no defects that remarkably decrease the glass strength such as
microcracks and have a high strength.
Example 2
[0083] Next, the performance and the like of the reinforced plate
glass of the present invention is described.
[0084] Table 1 shows collectively the reinforcement conditions for
obtaining a glass composition and a reinforced plate glass
corresponding to the example of the present invention, the
conditions for processing glass, strength measurement results of
glass, and the like, and the detail thereof is described
specifically.
TABLE-US-00001 TABLE 1 Example Sample No. 1 2 3 4 5 6 7 8 SiO.sub.2
65.4 65.4 65.4 61.6 68.3 65.4 60.5 60.5 B.sub.2O.sub.3 -- -- -- --
10.9 -- 1.8 1.8 Al.sub.2O.sub.3 22.0 22.0 22.0 13.2 5.2 22.0 12.0
12.0 Li.sub.2O 4.2 4.2 4.2 1.9 -- 4.2 -- -- Na.sub.2O 0.5 0.5 0.5
8.0 11.3 0.5 13.8 13.8 K.sub.2O 0.3 0.3 0.3 5.3 -- 0.3 4.0 4.0 CaO
-- -- -- -- 3.2 -- 1.7 1.7 ZnO -- -- -- 7.4 0.9 -- 2.0 2.0 BaO 1.5
1.5 1.5 -- -- 1.5 -- -- TiO.sub.2 2.0 2.0 2.0 2.1 -- 2.0 -- --
ZrO.sub.2 2.2 2.2 2.2 -- -- 2.2 4.0 4.0 P.sub.2O.sub.5 1.4 1.4 1.4
-- -- 1.4 -- -- AS.sub.2O.sub.3 0.5 0.5 0.5 -- -- 0.5 -- --
Sb.sub.2O.sub.3 -- -- -- 0.5 0.2 -- 0.2 0.2 Plate thickness X (mm)
0.5 0.5 0.5 0.5 0.5 0.5 0.7 0.5 Reinforce- Processing 500 475 475
400 490 500 410 410 ment temperature (.degree. C.) conditions
Processing time 2 4 2 4 8 2 4 3 (Hr) Reinforce- Compression 870 760
930 950 610 870 1,050 1,100 ment stress value P results (Mpa)
Thickness size T 11 13 9 9 16 11 23 15 of compression stress layer
(.mu.m) Compression stress function 20.0 20.8 17.4 17.7 20.9 20.0
37.0 35.0 F (Mpa) End face Processing method Scribe Scribe Scribe
Scribe Scribe Laser Scribe Scribe processing Application load 1.05
1.05 1.05 0.95 1 -- 1.1 1.1 conditions (kgf) Cutting edge angle 125
125 125 115 125 -- 115 115 (.degree.) Processing speed 50 75 75 75
50 -- 50 50 (mm/s) Cutting property Satisfactory Satisfactory
Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory
Satisfactory Strength Average breaking 1,040 870 1,130 1,170 690
1,210 1,200 1,250 evalu- stress value (MPa) ations Weibull
coefficient 5.4 6 5.1 5 6.5 7 7.5 7.8
[0085] In Table 1, Sample Nos. 1 to 8 were prepared as the
reinforced plate glasses of the present invention, and in Table 1,
the value of a glass composition represented by percent by mass of
an oxide conversion, the plate thickness of a used plate glass, the
conditions for chemical reinforcement, the reinforcement results,
the value of a compression stress function F, the evaluation of
strength, and the end face processing condition are shown in this
order from the above.
[0086] Each glass sample in Table 1 is described regarding its use.
Sample Nos. 1 to 5 are preferred as a thin plate glass with a
relatively large area such as a touch panel, and Sample Nos. 1 to 4
and Nos. 6 to 8 are materials preferred particularly as a
transparent display panel to be mounted on a precision appliance
and an electronic appliance such as a mobile phone and a mobile
information terminal appliance.
[0087] These samples were prepared using an actual production
facility experimentally. Glass materials were blended and mixed
previously so as to obtain each composition. The mixture was melted
homogeneously in a glass melting furnace, molded by a roll-out
method, and adjusted to a predetermined thickness by grinding,
whereby a parent plate glass was obtained. Then, the parent plate
glass thus produced was soaked in a molten salt tank in which a
potassium nitrate molten salt was built up, changing the processing
temperature condition and the processing time, whereby
predetermined reinforcement was conducted.
[0088] Regarding the investigation of the reinforcement state of
the plate glass thus reinforced, the compression stress value P and
the thickness size T of a compression stress layer were both
measured using a surface stress meter FSM-6000 manufactured by
Orihara Manufacturing Co., Ltd.
[0089] The compression stress function F was calculated based on
the evaluations of the compression stress value P and the thickness
size T of a compression stress layer. As a result, the calculated
values of Sample Nos. 1 to 8 were in a range of from 17.4 MPa to
37.0 MPa, all of which were 40 MPa or less. Thus, it was found that
there was no problem.
[0090] Then, scribe cleaving was selected for those which were
displayed as "SCRIBE" in Table 1 and laser cutting was selected for
those which were displayed as "LASER" in Table 1, and the parent
plate glass was processed in such a manner that a new glass surface
was formed on a plate end face of a reinforced plate glass so as to
have a size suitable for a strength test by any method.
[0091] Note that, regarding the scribe cleaving, the application
load, cutting edge angle, and processing speed were evaluated,
setting particular conditions, as shown in items of the end face
processing conditions in Table 1, using a cleaving apparatus having
an ultrahard wheel chip.
[0092] Further, regarding the laser cutting, cutting was conducted
under the conditions of an output of 30 W and a transfer speed of
20 mm/s of laser light on a glass surface, using a cutting
apparatus with a carbon dioxide gas laser as a light source.
[0093] Regarding the above-mentioned processing of a plate end
face, as shown in items of the end face processing conditions, it
was found that Sample Nos. 1 to 8 were in a state having
satisfactory cutting property. Further, when the plate end face of
the plate glass after cutting was observed with a microscope at a
magnification of 100 times, remarkable cracks and lacks, i.e.,
chipping were not observed at all.
[0094] Further, regarding the evaluation of strength, a test chip
with a width of 4 mm and a length of 40 mm was used, which was
produced by processing a plate glass end face by the
above-mentioned processing method, using an autograph testing
machine manufactured by Shimadzu Corporation in accordance with
"Bending test method of fine ceramics" JIS R1601 (1995) . The
strength test was conducted by a four-point bending test at a
pressure jig width of 10 mm, a support jig width of 30 mm, and a
crosshead speed of 0.5 mm/min under the conditions that a pressure
jig was in contact with a scribe cleaving surface or a laser
cutting surface of the sample. The arithmetic average of the
obtained results was calculated to obtain an average breaking
stress value. Further, a Weibull coefficient was obtained from a
gradient of a Weibull plot in accordance with "Weibull statistical
analysis method of strength data of fine ceramics" JIS R1625 (1996)
.
[0095] As a result of the above strength evaluations, in Sample
Nos. 1 to 8 that are examples, the average breaking stress value
was in a range of from 690 MPa to 1,250 MPa, all of which were 400
MPa or more. Further, the Weibull coefficient was from 5.0 to 7.8,
and it was found that the Weibull coefficient was 3 or more.
[0096] Sample Nos. 7 and 8 having the typical and best glass
composition of the present invention is described further.
[0097] The glass compositions of Sample Nos. 7 and 8 have a
composition of 60.5% of SiO.sub.2, 1.8% of B.sub.2O.sub.3, 12.0% of
Al.sub.2O.sub.3, 13.8% of Na.sub.2O, 4.0% of K.sub.2O, 1.7% of CaO,
2.0% of ZnO, 4.0% of ZrO.sub.2, and 0.2% of Sb.sub.2O.sub.3,
represented by percent by mass of an oxide conversion, and the
content of an Al.sub.2O.sub.3 component was 10% or more. Therefore,
Sample Nos. 7 and 8 have a glass composition of the reinforced
plate glass of the present invention exhibiting high performance
even in suppressing the decrease in weather resistance in a region
of a plate end face where a compression stress is not formed. These
plate glasses were subjected to scribing under the same conditions
except that Sample No. 7 had a plate thickness of 0.7 mm and Sample
No. 8 had a plate thickness of 0.5 mm. The compression stress
function F of Sample No. 7 was 37.0 MPa and that of Sample No. 8
was 35.0 MPa, both of which satisfied the requirement of 40 MPa or
less of the present invention. Therefore, a sharp and refined
processed surface along a planned line of scribe was obtained by
scribing, and surface defects such as lacks and cracks were not
recognized. Thus, processing of high quality was performed.
[0098] Further, the average breaking stress values of Sample Nos. 7
and 8 were 1,200 MPa and 1,250 MPa, respectively, which were
sufficiently high, and exhibited a high Weibull coefficient of 7.5
and 7.8. Thus, the most preferred result was obtained in the
present invention.
[0099] Accordingly, it was found that each of Sample Nos. 1 to 8
has sufficient performance as the reinforced plate glass of the
present invention and has high strength.
COMPARATIVE EXAMPLES
[0100] Then, Sample Nos. 101 to 105 shown in Table 2 as the
comparative examples of the present invention are described
below.
TABLE-US-00002 TABLE 2 Comparative Example Sample No. 101 102 103
104 105 SiO.sub.2 65.4 65.4 65.4 68.3 65.4 B.sub.2O.sub.3 -- -- --
10.9 -- Al.sub.2O.sub.3 22.0 22.0 22.0 5.2 22.0 Li.sub.2O 4.2 4.2
4.2 -- 4.2 Na.sub.2O 0.5 0.5 0.5 11.3 0.5 K.sub.2O 0.3 0.3 0.3 --
0.3 CaO -- -- -- 3.2 -- ZnO -- -- -- 0.9 -- BaO 1.5 1.5 1.5 -- 1.5
TiO.sub.2 2.0 2.0 2.0 -- 2.0 ZrO.sub.2 2.2 2.2 2.2 -- 2.2
P.sub.2O.sub.5 1.4 1.4 1.4 -- 1.4 As.sub.2O.sub.3 0.5 0.5 0.5 --
0.5 Sb.sub.2O.sub.3 -- -- -- 0.2 -- Plate thickness X (mm) 0.5 0.5
0.5 0.4 0.5 Reinforce- Processing -- 500 500 520 500 ment
temperature (.degree. C.) conditions Processing time -- 2 24 24 24
(Hr) Reinforce- Compression -- 870 690 404 690 ment stress value P
results (Mpa) Thickness size T -- 11 36 39 36 of compression stress
layer (.mu.m) Compression stress function -- 20.0 57.0 49.0 57.0 F
(Mpa) End face Processing method -- -- Scribe Scribe Laser
processing Application load -- -- 1.05 1.1 -- conditions (kgf)
Cutting edge angle -- -- 125 115 -- (.degree.) Processing speed --
-- 50 50 -- (mm/s) Cutting property -- -- Impossible Impossible
Impossible Strength Average breaking 330 800 -- -- -- evalu- stress
value (MPa) ations Weibull coefficient 2.6 4.5 -- -- --
[0101] Regarding the comparative examples, each sample was prepared
in the same procedure as that of the examples. Sample No. 101 was
prepared as a sample which was not reinforced. Further, Sample Nos.
101 and 102 were produced by scribe cutting, and the scribing
conditions follow the conditions in the case of cutting a
reinforced plate glass. Sample No. 101 was not reinforced after
scribe cutting, and Sample No. 102 was reinforced after scribe
cutting.
[0102] As a result of the evaluation of the comparative examples,
Sample No. 101 had the same composition as that of Sample No. 1 of
the example. However, Sample No. 101 had a low Weibull coefficient,
i.e., 2.6, although having an average breaking stress value of 330
MPa. Thus, Sample No. 101 did not satisfy the requirements of the
present invention.
[0103] Sample No. 102 had an average breaking stress value of 800
MPa and a Weibull coefficient of 4.5. The average breaking stress
value and the Weibull coefficient of Sample No. 102 were both
inferior to those of Example 1, in spite of the fact that Sample
No. 102 had the same composition as that of Example 1. The detailed
reasons for such results are not known. The inventors of the
present invention predicted as follows: unlike the present
invention, the above test chip is reinforced after processing, that
is, the test chip has a stress distribution state that does not
satisfy the requirements of the present invention, and hence,
defects on a glass surface, such as chipping caused during
processing or reinforcement, have an influence on the results.
Further, the production fee is expensive under the production
conditions of Sample No. 102, which clearly decreases production
efficiency.
[0104] Sample No. 103 had the same composition as that of Sample
No. 1, and the evaluation of a cutting property was conducted by
scribe cutting under the same condition as that of Sample No. 1
that was the example after ion exchange reinforcement under the
conditions of 500.degree. C. and 24 hours as shown in Table 2. The
compression stress function F was a high value, i.e., 57.0 MPa
which was more than 40 MPa. As a result, when an attempt was made
so as to conduct scribing, cracks were propagated to a portion
other than a portion to be cut, and a plate glass was partially
broken, and hence, Sample No. 103 had a quality insufficient for
obtaining good quality goods.
[0105] Sample No. 104 had the same composition as that of Sample
No. 5, and the evaluation of a cutting property was conducted by
scribe cutting under the same condition as that of Sample No. 1
that was the example after ion exchange reinforcement under the
conditions of 410.degree. C. and 24 hours as shown in Table 2.
Regarding Sample No. 104, the compression stress function F was
49.0 MPa which was also more than 40 MPa. Therefore, a number of
lacking defects and the like occurred during scribing, and in some
cases, Sample No. 104 had a quality in which the same breakage of a
plate glass as that of Sample No. 103 was recognized. Further,
Sample No. 104 contained an Al.sub.2O.sub.3 component in an amount
of less than 10%. Therefore, when an environment evaluation or the
like of glass was conducted in a thermo-hygrostat tank, trouble was
caused to the weather resistance in a region of a plate end face
where a compression stress was not formed, and a precipitate was
likely to be generated on the surface.
[0106] Sample No. 105 had the same composition as that of Sample
No. 1, and the evaluation of a cutting property was conducted by
laser cutting under the same condition as that of the example after
ion exchange reinforcement under the conditions of 500.degree. C.
and 24 hours as shown in Table 2. The plate glass was broken in the
same way as in scribing, and thus, Sample No. 105 had a quality
that desired processing could not be conducted.
[0107] Sample Nos. 103 to 105 were each produced under the
condition that the compression stress function was more than 40
MPa. Therefore, in each of Sample Nos. 103 to 105, a satisfactory
cutting property was not obtained, the ratio of good quality was
decreased, and an economically excellent reinforced plate glass was
not obtained.
[0108] As described above, it was found from the examples and the
comparative examples that the reinforced plate glass of the present
invention can realize a production efficiency with a high
economical efficiency, and has sufficiently excellent strength.
Example 3
[0109] Further, FIG. 4 is a perspective explanatory view
illustrating a reinforced plate glass as an example of the present
invention in a different aspect from that of Example 1.
[0110] The reinforced plate glass 20 shown in FIG. 4 is different
from the previous Example 1 in that ion exchange reinforcement is
conducted during the processing of a reinforced plate glass. More
specifically, a plate glass that is preliminarily formed into a
strap shape is subjected to an ion exchange treatment, and only two
plate end faces of the strap-shaped plate glass are cut by physical
processing. Thus, in FIG. 4, among the plate end faces 23, 24, 25,
and 26 of the reinforced plate glass, the plate end faces 23 and 25
are not subjected to ion exchange reinforcement, and the other
plate end faces 24 and 26 are subjected to ion exchange
reinforcement. In this respect, in the case of the previous Example
1, none of the plate end faces 13, 14, 15, and 16 are subjected to
ion exchange reinforcement. It is possible to arbitrarily determine
an end face which is to be subjected to ion exchange in terms of
the use, production efficiency, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0111] FIG. 1 is a perspective view of a reinforced plate glass of
the present invention;
[0112] FIG. 2 is an explanatory view illustrating a reinforced
state of the reinforced plate glass of the present invention;
[0113] FIG. 3 is an explanatory view illustrating a stress
distribution on the surface of an end face subjected to physical
processing (scribing) of the reinforced plate glass of the present
invention; and
[0114] FIG. 4 is a perspective view of another reinforced plate
glass of the present invention.
DESCRIPTION OF THE SYMBOLS
[0115] 10,20 reinforced plate glass [0116] 11, 12, 21, 22 plate
surface [0117] 13, 14, 15, 16, 23, 24, 25, 26 plate end face [0118]
J region where compression stress is formed [0119] U region where
compression stress is not formed [0120] S plate surface [0121] B
glass bulk [0122] T tensile stress [0123] C compression stress
* * * * *