CN118878204A - Chemically strengthened glass, chemically strengthened glass, electronic device, and method for producing chemically strengthened glass - Google Patents

Abstract

The purpose of the present invention is to provide a glass and a chemically strengthened glass which can suppress abnormal light emission phenomenon of a display when used for a cover glass of a display such as an electronic device. The chemically strengthened glass has a specific composition range, wherein the ratio (R ₂O/Al₂O₃) of the total content of Li ₂O、Na₂ O and K ₂ O to the content of Al ₂O₃ satisfies the formula (A) of 0.8.ltoreq.R ₂O/Al₂O₃.ltoreq.30, the K-DOL defined below is 4.2 μm or more, or K-CSarea is 4000 Pa.m or more, and the surface resistivity is 11[ log Ω/sq ] or more. K-CS ₀ (MPa) is a compressive stress value of the glass surface measured by a glass surface stress meter, K-DOL (μm) is a value of depth of a compressive stress layer generated by potassium ions from the glass surface, and K-CSarea (Pa.m) is a product of K-CS ₀ and K-DOL.

Description

Chemically strengthened glass, chemically strengthened glass, electronic device and method for manufacturing chemically strengthened glass

Technical Field

The present invention relates to chemically strengthened glass, chemically strengthened glass, electronic equipment, and a method for producing chemically strengthened glass.

Background Art

Chemically strengthened glass has been used in cover glasses of mobile terminals, etc. Chemically strengthened glass is obtained by contacting glass with a molten salt composition such as sodium nitrate, causing ion exchange between alkali metal ions contained in the glass and alkali metal ions with a large ion radius contained in the molten salt composition, thereby forming a compressive stress layer on the surface of the glass.

Patent Document 1 discloses that the lower the surface resistivity of the chemically strengthened cover glass, the higher the durability of the antifouling layer formed on the cover glass. There is a correlation between the surface resistivity and the conductivity of the glass surface, and a small surface resistivity indicates that the conductivity of the glass surface is high. That is, increasing the conductivity of the glass surface can improve the durability of the antifouling layer.

Prior art literature

Patent Literature

Patent Document 1: International Publication No. 2021/010376

Summary of the invention

In recent years, the "abnormal light emission phenomenon" in which a part of the organic EL display (OLED) emits light unintentionally and continuously has become a problem in electronic devices such as mobile terminals. The abnormal light emission phenomenon is believed to be related to static electricity generated by rubbing the display for a long time.

Patent Document 1 focuses on the relationship between the surface resistivity of chemically strengthened glass and the adhesion of an antifouling layer formed on the surface thereof, but does not study the abnormal light emission phenomenon at all.

An object of the present invention is to provide chemically strengthened glass and chemically strengthened glass which can suppress abnormal light emission of a display when used as a cover glass of a display of an electronic device or the like.

The inventors of the present invention believed that the abnormal luminescence phenomenon was related to the easy movement of charges due to static electricity, and found that the resistance of glass (hereinafter sometimes referred to as "resistance") was related to the ease of abnormal luminescence phenomenon. More specifically, they found that the greater the resistance of glass, the easier it was to suppress the abnormal luminescence phenomenon, and thus completed the present invention.

That is, the present disclosure relates to the following aspects.

1. A chemically strengthened glass comprising, expressed in molar percentages based on oxides, 50% or more of _SiO2 , 0 to 10% of _B2O3 , 1 to 30% of _Al2O3 , 0 to 10% of _{P2O5 , 0} to ₁₀ % of _Y2O3 , 0 to _{25% of Li2O, 0 to 25% of Na2O, 0 to 25% of K2O , 0 to} 10% of MgO, 0 to 10% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, 0 to 10% of ZnO, 0 to 5% of _ZrO2 , 0 to 5% of _{TiO2 ,} 0 to 5% of SnO2 _, and 0 to 0.5% of _Fe2O3 ,

The ratio of the total content of Li ₂ O, Na ₂ O, and K ₂ O to the content of Al ₂ O ₃ (R ₂ O/Al ₂ O ₃ ) satisfies the following formula (A).

(A)0.8≤(R ₂ O/Al ₂ O ₃ )≤30

2. The chemically strengthened glass according to item 1 above, comprising 7 to 12% of Li ₂ O, 1.5 to 6% of Na ₂ O, and 0 to 1.5% of K ₂ O, expressed in molar percentage based on oxides.

3. A chemically strengthened glass having a K-DOL as defined below of 4.2 μm or more and a surface resistivity of 11 [logΩ/sq] or more.

K-DOL (μm): The depth of the compressive stress layer generated by potassium ions from the glass surface

4. A chemically strengthened glass having a K-CSarea as defined below of 4000 Pa·m or more and a surface resistivity of 11 [logΩ/sq] or more,

K-CSarea (Pa·m): the product of K-CS ₀ and K-DOL,

K-CS ₀ (MPa): compressive stress value of the glass surface measured by a glass surface stress meter, K-DOL (μm): depth value of the compressive stress layer generated by potassium ions from the glass surface.

5. The chemically strengthened glass according to 4 above, wherein the K-CS ₀ is 800 MPa or more.

6. A chemically strengthened glass, wherein the ratio of the K ₂ O concentration at a depth of 3 μm from the glass surface, i.e., K ₂ O@3 μm, to the K ₂ O concentration at the center of the plate thickness, i.e., K ₂ O@center, is 5.3 or more,

The surface resistivity is 11 [logΩ/sq] or more.

7. A chemically strengthened glass, wherein the ratio of the Li ₂ O concentration at a depth of 5 μm from the glass surface (Li ₂ O@5 μm) to the Li ₂ O concentration at the center of the plate thickness (Li ₂ O@center) is 0.85 or less,

The surface resistivity is 11 [logΩ/sq] or more.

8. The chemically strengthened glass according to any one of 3 to 7 above, wherein the value of Y defined below is 9.4 or more.

Y＝0.00018x ₁ +4.319×10 ^-7 x ₂ +8.5

x ₁ ： K-CSarea (Pa·m), the product of K-CS ₀ and K-DOL

x ₂ ：Na-CS area (Pa·m), the product of Na-CS ₀ and Na-DOL

K-CS ₀ (MPa): Compressive stress value of the glass surface measured by a glass surface stress gauge

K-DOL (μm): The depth of the compressive stress layer generated by potassium ions from the glass surface

Na-CS ₀ (MPa): Compressive stress value of glass surface measured by scattered light photoelastic stress meter

Na-DOL (μm): The depth of the compressive stress layer generated by Na ions from the glass surface

9. An electronic device comprising the chemically strengthened glass according to 1 or 2 above, or the chemically strengthened glass according to any one of 3 to 8 above.

10. A method for manufacturing chemically strengthened glass, comprising:

a first ion exchange treatment, wherein the first molten salt composition is brought into contact with the chemically strengthened glass;

a second ion exchange treatment, after the first ion exchange treatment, bringing a second molten salt composition into contact with the chemically strengthened glass;

In the second molten salt composition, the content of KNO ₃ is 94 mass % or more, and the content of lithium ions is less than 300 mass ppm.

11. The method for producing a chemically strengthened glass according to 10 above, wherein the temperature of the second molten salt composition in the second ion exchange treatment is 380° C. to 450° C., and the time for which the second molten salt composition is in contact with the chemically strengthened glass is 60 minutes or more.

12. The method for producing a chemically strengthened glass according to 10 or 11 above, wherein the second molten salt composition contains 0 to 5 mass % of NaNO ₃ .

13. A method for producing chemically strengthened glass, comprising subjecting chemically strengthened glass to ion exchange treatment to obtain chemically strengthened glass,

The K-DOL defined below is 4.2 μm or more, and the surface resistivity is 11 [logΩ/sq] or more.

K-DOL (μm): The depth of the compressive stress layer generated by potassium ions from the glass surface

14. A method for producing chemically strengthened glass, comprising subjecting chemically strengthened glass to ion exchange treatment to obtain chemically strengthened glass,

The K-CSarea defined below is 4000 Pa·m or more, and the surface resistivity is 11 [logΩ/sq] or more.

K-CSarea (Pa·m): product of CS ₀ and K-DOL

CS ₀ (MPa): compressive stress value of glass surface

K-DOL (μm): The depth of the compressive stress layer generated by potassium ions from the glass surface

According to the present invention, a chemically strengthened glass can be provided which can suppress abnormal light emission of a display when used as a cover glass of a display of an electronic device, etc. In addition, a chemically strengthened glass which can easily obtain a high-resistance chemically strengthened glass by chemical strengthening is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating the abnormal light emission phenomenon.

FIG. 2 is a graph showing the relationship between surface resistivity and volume resistivity.

FIG. 3 is a graph showing the relationship between the value of Y and the volume resistivity (measured value).

FIG. 4 is a graph of a K ₂ O profile of a surface layer.

Explanation of symbols

10OLED Display

11 Cover glass

12 Charge

13OLED light emitting element

14Polyimide substrate

15 cathode

16 TFT array

DETAILED DESCRIPTION

In this specification, "to" indicating a numerical range is used to include the numerical values recorded before and after it as the lower limit and upper limit. In addition, in this specification, the composition of glass (the content of each component) is recorded in terms of molar percentage based on oxides unless otherwise specified, and molar % is simply expressed as "%".

In addition, in this specification, "substantially not containing" means that the amount is less than the level of impurities contained in raw materials, etc., that is, it means that the amount is not intentionally added. Specifically, for example, it is less than 0.1%.

In this specification, "amorphous glass" refers to glass in which no diffraction peak indicating crystals is confirmed by X-ray powder diffraction method. "Crystallized glass" is glass obtained by heat-treating "amorphous glass" to precipitate crystals, and contains crystals. In this specification, "amorphous glass" and "crystallized glass" are sometimes referred to as "glass". In addition, amorphous glass that becomes crystallized glass by heat treatment is sometimes referred to as "mother glass of crystallized glass".

Hereinafter, "chemically strengthened glass" refers to glass subjected to a chemical strengthening treatment, and "glass for chemical strengthening" refers to glass before subjected to a chemical strengthening treatment.

＜Stress measurement method＞

In recent years, cover glasses for smartphones and the like have become mainstream, using glass obtained by chemical strengthening in two or more stages, namely, exchanging lithium ions inside the glass with sodium ions (Li-Na exchange) and then further exchanging the sodium ions inside the glass with potassium ions in the surface layer of the glass (Na-K exchange).

In order to obtain such a stress distribution map of the chemically strengthened glass in a non-destructive manner, for example, a scattered light photoelastic stress meter (SLP) or a film stress meter (FSM) may be used in combination.

In the method using a scattered light photoelastic stress meter (SLP), the compressive stress resulting from Li-Na exchange can be measured inside the glass at a distance of several tens of micrometers or more from the glass surface.

On the other hand, in the method using a glass surface stress meter (FSM), the compressive stress from Na-K exchange can be measured in the glass surface layer at a distance of several tens of μm or less from the glass surface (for example, International Publication No. 2018/056121 and International Publication No. 2017/115811).

Therefore, as a stress distribution map of the glass surface layer and the interior in two-step chemically strengthened glass, a stress distribution map obtained by synthesizing information of SLP and FSM may be used.

In the present invention, the stress distribution diagram measured by a scattered light photoelastic stress meter (SLP) is mainly used. It should be noted that the compressive stress CS, tensile stress CT, compressive stress layer depth DOC, etc. referred to in this specification refer to the values in the SLP stress distribution diagram.

A scattered light photoelastic stress gauge is a stress measuring device comprising: a polarization phase difference variable member for varying the polarization phase difference of laser light by one or more wavelengths relative to the wavelength of the laser light; an imaging element for capturing scattered light emitted by the laser light after the polarization phase difference is changed incident on a tempered glass a plurality of times at a predetermined time interval to obtain a plurality of images; and a computing unit for measuring periodic brightness changes of the scattered light using the plurality of images, calculating phase changes of the brightness changes, and calculating stress distribution in a depth direction from the surface of the tempered glass based on the phase changes.

As a method for measuring the stress distribution map using a scattered light photoelastic stress meter, the method described in International Publication No. 2018/056121 can be cited. As scattered light photoelastic stress meters, for example, SLP-1000 and SLP-2000 manufactured by Orihara Seisakusho can be cited. If the accompanying software SlpIV_up3 (Ver.2019.01.10.001) is combined with these scattered light photoelastic stress meters, high-precision stress measurement can be performed.

＜K-DOL, K-CS ₀ , K-CSarea＞

"K-DOL" in this specification refers to the depth of the compressive stress layer generated by potassium ions from the Na-K exchange in the glass surface portion of the glass surface below tens of μm from the glass surface. K-DOL is a value that can be approximated by the depth at which the potassium ion concentration is equal to the potassium ion concentration in the central portion of the plate thickness. In addition, it can also be measured as a measurement limit value of the compressive stress layer depth measured by a glass surface stress meter (FSM).

“K-CS ₀ ” refers to the compressive stress value due to potassium ions at a depth of 0 μm measured by FSM.

“K-CSarea” refers to the product of K-CS ₀ and K-DOL.

＜Na-DOL, Na-CS ₀ , Na-CSarea＞

In this specification, "Na-DOL" refers to the depth of the compressive stress layer caused by Na ions from Li-Na exchange in the glass at a depth of several tens of micrometers or more from the glass surface. Na-DOL is the depth at which the compressive stress caused by Na ions is zero.

“Na-CS ₀ ” refers to the compressive stress value due to Na ions at a depth of 0 μm measured by SLP.

“Na-CSarea” refers to the product of Na-CS ₀ and Na-DOL.

＜CTave＞

In this specification, "CTave" (MPa) is calculated by the following formula: CTave is a value corresponding to the average value of the tensile stress, and is a value obtained by integrating the stress value of the tensile stress region and dividing the result by the length of the tensile stress region.

CTave＝ICT/L _CT

ICT: Integrated value of tensile stress (Pa·m)

L _CT : Length of the tensile stress region in the plate thickness direction (μm)

＜CS _x ＞

In this specification, "CS _x " refers to the compressive stress value (MPa) at a depth x (μm) from the glass surface. This value is a value measured by SLP.

<K ₂ O concentration, Na ₂ O concentration>

In this specification, the K ₂ O concentration and the Na ₂ O concentration at the depth x (μm) are concentrations measured in a cross section in the plate thickness direction by EPMA (Electron Probe Micro Analyzer). Specifically, the EPMA measurement is performed, for example, as follows.

First, a glass sample was embedded in epoxy resin, and the first main surface and the second main surface opposite to the first main surface were mechanically polished in the vertical direction to prepare a cross-sectional sample. The polished cross section was subjected to C coating and measured using EPMA (manufactured by JEOL: JXA-8500F). The acceleration voltage was 15 kV, the probe current was 30 nA, and the accumulation time was 1000 msec./point. The line distribution diagram of the X-ray intensity of K ₂ O or Na ₂ O was obtained at 1 μm intervals. For the obtained K ₂ O concentration distribution diagram or Na ₂ O concentration distribution diagram, the average count of the central part of the plate thickness (0.5×t)±25 μm (the plate thickness is t μm) was taken as the parent composition, and the count of the entire plate thickness was converted into mole % according to the ratio and calculated.

＜Li ₂ O concentration＞

In this specification, the Li ₂ O concentration at a depth x (μm) is the concentration of a cross section in the plate thickness direction measured by GD-OES (Glow Discharge Optical Emission Spectroscopy). Specifically, the GD-OES measurement is performed, for example, as follows.

First, the glass sample was cleaned by washing. The measurement was performed using a Marcus type high frequency glow discharge luminescence analyzer (GD-Profiler2 manufactured by HORIBA Manufacturing Co., Ltd.). The discharge conditions were 40 W (constant power mode), Ar pressure 200 Pa, discharge mode pulse sputtering mode (duty cycle 0.25 DS), discharge range Under these conditions, the emission spectrum was obtained relative to the sputtering time. The obtained Li concentration was normalized with the concentration in the unreinforced substrate and then proportionally converted to the Li ₂ O concentration contained in the substrate. The discharge mark depth after the measurement was measured using a surface roughness meter, and the sputtering time was converted into the measured depth in 0.00025 μm increments. The distribution graph was further smoothed with a width of 0.25 μm using the Centered Moving Average method.

＜Chemically strengthened glass＞

Chemical strengthening treatment is a treatment in which the glass is brought into contact with a metal salt (e.g., sodium nitrate, potassium nitrate) by immersing, coating, or spraying in a melt of a metal salt containing metal ions with large ionic radius (typically sodium ions or potassium ions), thereby replacing the metal ions with small ionic radius (typically lithium ions or sodium ions) in the glass with the metal ions with large ionic radius (typically sodium ions or potassium ions relative to lithium ions, and potassium ions relative to sodium ions) in the metal salt.

＜Relationship between abnormal luminescence phenomenon and glass resistance＞

As mentioned above, for electronic devices such as mobile terminals, the "abnormal light emission phenomenon" in which a part of the display emits unintentional and continuous light is becoming a problem. This phenomenon is known to occur particularly in PI-OLED (organic EL display using a polyimide substrate). It is known that the abnormal light emission phenomenon typically occurs after the display of an electronic device is rubbed with a finger for a long time. While it is believed that light emission is easy to occur near the end (peripheral part) of the display and the hole part, it is generally believed that the light emission lasts for a long time (about 1 to 2 days in the long case) rather than a short time.

In addition, the present inventors found that, in order to suppress the abnormal light emission phenomenon, it is effective to increase the resistance of the glass used in the cover glass. Furthermore, the present inventors found that the resistance of the chemically strengthened glass can be increased by a chemical strengthening process, and that by adjusting the glass composition to an appropriate range, it is easy to obtain a chemically strengthened glass with high resistance, thereby completing the present invention.

In this specification, the resistance of the cover glass is evaluated by surface resistivity or volume resistivity. Here, the surface resistivity is the value of the surface resistance of each ^1cm2 of glass. The surface resistivity of a main surface of the glass is related to the ease of movement of charges in the direction parallel to the main surface direction. The higher the surface resistivity, the less likely it is for charges to flow in the direction parallel to the main surface direction. Therefore, the surface resistivity is a value that is almost unrelated to the thickness of the glass. In addition, the volume resistivity is the volume resistance value of each ^1cm3 of glass. The volume resistivity of the glass is related to the ease of movement of charges from one main surface of the glass to the other main surface opposite to it (hereinafter, sometimes referred to as the thickness direction). The higher the volume resistivity, the less likely it is for charges to flow in the thickness direction.

FIG2 shows the relationship between the surface resistivity and volume resistivity of a chemically strengthened glass having the same parent composition and thickness and subjected to chemical strengthening treatment under multiple different conditions. It can be seen from the figure that: first, the chemical strengthening process affects the resistance of the chemically strengthened glass. That is, it can be seen that the resistance of the chemically strengthened glass can be increased by appropriately controlling the conditions of the chemical strengthening process or the characteristics of the chemically strengthened glass obtained therefrom. In addition, the inventors of the present invention have conducted research and found that the following (I) and (II) are conducive to the direction in which the resistance of the chemically strengthened glass increases.

(I) In the vicinity of the glass surface, a plurality of different alkali metal ions are mixed in a nearly equal ratio.

(II) A state in which a larger number of alkali metal ions having a larger size are introduced near the glass surface by chemical strengthening treatment.

In addition, according to Figure 2, there is a positive correlation between the surface resistivity and the volume resistivity. It is believed that when the surface of the chemically strengthened glass is in a state of high resistance, when the charge moves in a direction parallel to the main surface direction, it is not easy for the charge to move near the surface of the main surface, and the charge detours in the deeper part from the main surface. If the surface resistivity is measured in this case, it is believed that when the charge moves from the vicinity of the main surface to the deep part and when it returns from the deep part to the vicinity of the main surface, it passes through the high resistance part twice. In addition, when measuring the volume resistivity, it is also believed that the charge passes through the high resistance part near one main surface and the high resistance part near the other main surface, passing through the high resistance part twice. This shows that there is a linear positive correlation between the surface resistivity and the volume resistivity. Moreover, according to the situation, it can be said that the use of chemically strengthened glass with higher resistance can suppress the movement of charges in two directions, the direction parallel to the main surface of the display and the direction of the thickness, which helps to suppress abnormal luminescence.

The embodiments of the present invention are described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any manner without departing from the gist of the present invention. For example, for the multiple embodiments illustrated in this specification, the preferred modes of each embodiment can be combined with each other, or a part of each embodiment can be replaced with the preferred mode of another embodiment.

The chemically strengthened glass of the present embodiment includes the chemically strengthened glasses of the first and second embodiments described below.

(First embodiment)

The chemically strengthened glass according to the first embodiment of the present invention contains, expressed in terms of molar percentage based on oxides, 50% or more of _SiO2 , 0 to 10 _% of _B2O3 , 1 to 30% of _{Al2O3 ,} 0 to 10% of _P2O5 , 0 to 10% of _{Y2O3 ,} 0 to 25% of _Li2O , 0 to 25% of _Na2O , 0 to 25% of _K2O , 0 to 10% of _MgO , 0 to 10% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, 0 to 10% of ZnO, 0 to 5% of _ZrO2 , 0 to 5% of _TiO2 , 0 to 5% of _SnO2 , and 0 to 0.5% of _{Fe2O3 ;}

The ratio of the total content of Li ₂ O, Na ₂ O, and K ₂ O to the content of Al ₂ O ₃ (R ₂ O/Al ₂ O ₃ ) satisfies the following formula (A).

(A)0.8≤(R ₂ O/Al ₂ O ₃ )≤30

The chemically strengthened glass according to the first embodiment has the above-mentioned composition, so that the glass itself tends to have a high electrical resistance, and chemically strengthened glass having a high electrical resistance can be easily obtained when chemical strengthening is performed.

From the viewpoint of increasing the surface resistivity and volume resistivity and introducing compressive stress required to increase the strength of the glass, the chemically strengthened glass of the first embodiment preferably contains 7 to 12% _Li2O , 1.5 to 6% _Na2O , and 0 to 1.5% _K2O , expressed in molar percentage based on oxides.

Hereinafter, a more preferable composition of the chemically strengthened glass according to the first embodiment will be described in detail. Regarding the glass composition, the preferable lower limit of the content of the non-essential components is 0%.

In the chemically strengthened glass of the present embodiment, SiO ₂ is a component that forms a network structure of the glass and is also a component that improves chemical durability.

The content of _SiO2 is 50% or more, preferably 52% or more, more preferably 56% or more, further preferably 60% or more, particularly preferably 64% or more, and most preferably 68% or more. On the other hand, in order to make the meltability good, the content of _SiO2 is less than 75%, preferably 73% or less, more preferably 72% or less, further preferably 71% or less, particularly preferably 70% or less, and most preferably 69% or less.

B ₂ O ₃ is a component that improves the chipping resistance of the chemically strengthened glass or chemically strengthened glass and improves the meltability, and may be contained. In order to improve the meltability, the content of B ₂ O ₃ when contained is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. On the other hand, if the content of B ₂ O ₃ is too high, striae are generated during melting or phase separation is easily caused, and the quality of the chemically strengthened glass is easily reduced, so it is preferably 10% or less. The content of B ₂ O ₃ is more preferably 8% or less, further preferably 6% or less, and particularly preferably 4% or less.

Al ₂ O ₃ is a component that increases the surface compressive stress generated by chemical strengthening and is essential.

The content of _Al2O3 is 1% or more, _and the following are 3% or more, 5% or more, 7% or more, 9% or more, preferably 11% or more, more preferably 12% or more, further preferably 13% or more, particularly preferably 14% or more, and most preferably 15% or more. On the other hand, in order to prevent the devitrification temperature of the _glass from becoming too high, the content of _Al2O3 is 30% or less, preferably 27% or less, more preferably 24% or less, further preferably 21% or less, particularly preferably 19% or less, and most preferably 18% or less.

_P2O5 is not essential, but may be contained as a component to increase the compressive stress layer generated by chemical strengthening. _{In addition, P2O5 is a component that can promote the diffusion of potassium ions during chemical strengthening treatment, so from the perspective of obtaining chemically strengthened glass with high resistance, P2O5 is preferably contained. P2O5 is also a component that can} promote crystallization in crystallized glass.

When P ₂ O ₅ is contained, the content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more.

On the other hand, if _{the P2O5 content} is too high, phase separation is likely to occur during melting and the acid resistance is significantly reduced. Therefore, _{the P2O5} content is 10% or less, preferably 8% or less, more preferably 6% or less, further preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less.

_Y2O3 is not essential, but is _a component having an effect of making it difficult for fragments to scatter when the chemically strengthened glass is broken, and may be contained.

When Y ₂ O ₃ is contained, the content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more.

On the other hand, in order to suppress devitrification during melting, the content of _Y2O3 is 10% or less, preferably 8% or less, more preferably 6% or less, further preferably 4% _or less, particularly preferably 3.5% or less, and most preferably 3% or less.

Li ₂ O, Na ₂ O, and K ₂ O are components having the following effects: an effect of increasing the surface resistivity and volume resistivity; and an effect of adjusting the ion exchange characteristics of the glass in order to appropriately introduce into the glass the compressive stress required for increasing the strength of the glass. From the viewpoint of increasing the surface resistivity and volume resistivity and from the viewpoint of introducing the compressive stress by chemical strengthening treatment, in the glass of the present embodiment, the total content of Li ₂ O, Na ₂ O, and K ₂ O exceeds 0%, preferably 10% or more, more preferably 11% or more, further preferably 12% or more, particularly preferably 14% or more, and most preferably 16% or more. From the viewpoint of reducing the devitrification characteristics during glass molding, the total content of Li ₂ O, Na ₂ O, and K ₂ O is preferably 35% or less, more preferably 30% or less, further preferably 25% or less, particularly preferably 20% or less, and most preferably 19% or less.

In the glass of the present embodiment, the ratio of the total content of Li ₂ O, Na ₂ O, and K ₂ O to the content of Al ₂ O ₃ (R ₂ O/Al ₂ O ₃ ) satisfies the following formula (A).

(A)0.8≤(R ₂ O/Al ₂ O ₃ )≤30

(R ₂ O/Al ₂ O ₃ ) satisfies the above formula (A) which means that the content of Al ₂ O ₃ is greater or less than the content of the alkali metal oxide. This can achieve the effect of improving the surface resistivity and volume resistivity.

When (R ₂ O/Al ₂ O ₃ ) satisfies the above formula (A), (R ₂ O/Al ₂ O ₃ ) is 0.8 or more, preferably 0.84 or more, more preferably 0.88 or more, further preferably 0.92 or more, particularly preferably 0.96 or more, and most preferably 1.0 or more. On the other hand, (R ₂ O/Al ₂ O ₃ ) is 30 or less, preferably 25 or less, 20 or less, 10 or less, 5 or less, and 2 or less, more preferably 1.8 or less, further preferably 1.5 or less, and further preferably 1.0 or less.

Li ₂ O is a component that generates compressive stress by ion exchange.

_Li2O is not essential, but when contained, the content is preferably 3% or more, more preferably 5% or more, further preferably 7% or more, further preferably 8% or more, particularly preferably 9% or more, and most preferably 10% or more. On the other hand, in order to stabilize the glass, the content of _Li2O is 25% or less, preferably 22% or less, more preferably 20% or less, further preferably 18% or less, particularly preferably 16% or less, further particularly preferably 14% or less, and most preferably 12% or less.

Na ₂ O is a component that improves the solubility of glass.

Na ₂ O is not essential, but when contained, the content is preferably 1% or more, more preferably 1.5% or more, further preferably 2% or more, further preferably 3% or more, particularly preferably 4% or more, and most preferably 5% or more. If Na ₂ O is too much, the chemical strengthening characteristics are reduced, so the content of Na ₂ O is preferably 25% or less, more preferably 20% or less, further preferably 15% or less, particularly preferably 12% or less, further particularly preferably 10% or less, and most preferably 6% or less.

K ₂ O is not essential, but is a component that lowers the melting temperature of glass like Na ₂ O, and may be contained.

When K ₂ O is contained, the content is preferably 0.1% or more, more preferably 0.5% or more, further preferably 1% or more, particularly preferably 1.5% or more, and most preferably 2% or more. If K ₂ O is too much, chemical strengthening characteristics are reduced or chemical durability is reduced, so the content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, particularly preferably 5% or less, further particularly preferably 4% or less, and most preferably 1.5% or less.

In order to improve the meltability of glass raw materials, the total content of _Na2O and _K2O , _Na2O + _K2O , is preferably 2% or more, more preferably 3% or more, further preferably 4% or more, particularly preferably 5% or more, and most preferably 6% or more. _Na2O + _K2O is preferably 20% or less, more preferably 15% or less, further preferably 12% or less, particularly preferably 10% or less, and most preferably 8% or less.

BaO, SrO, MgO, CaO and ZnO are all components that improve the meltability of glass and can be contained. When any one or more of BaO, SrO, MgO, CaO and ZnO are contained, their total content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. On the other hand, from the viewpoint of maintaining the ion exchange rate at a certain level or more, their total content is preferably 10% or less, more preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

MgO is not essential, but is a component that stabilizes glass and also a component that improves mechanical strength and chemical resistance. Therefore, when the Al ₂ O ₃ content is low, it is preferably contained.

The content of MgO is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

On the other hand, if MgO is excessively added, the viscosity of the glass decreases, and devitrification or phase separation is likely to occur. The MgO content is 10% or less, preferably 9% or less, more preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

CaO is not essential, but may be contained as a component to improve the solubility of glass.

The CaO content is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

On the other hand, if the content of CaO is excessive, it is difficult to increase the compressive stress value during chemical strengthening treatment. The content of CaO is 10% or less, preferably 9% or less, more preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

SrO is not essential, but may be contained as a component to improve the solubility of glass.

The SrO content is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

On the other hand, if the SrO content is excessive, it is difficult to increase the compressive stress value during chemical strengthening treatment. The SrO content is 10% or less, preferably 9% or less, more preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

BaO is not essential, but may be contained as a component to improve the solubility of glass.

The BaO content is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

On the other hand, if the content of BaO is excessive, it is difficult to increase the compressive stress value during chemical strengthening treatment. The content of BaO is 10% or less, preferably 9% or less, more preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

ZnO is not essential, but may be contained as a component to improve the solubility of glass.

The content of ZnO is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

On the other hand, if the ZnO content is excessive, it is difficult to increase the compressive stress value during chemical strengthening treatment. The ZnO content is 10% or less, preferably 9% or less, more preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

ZrO ₂ is not essential, but is a component that improves mechanical strength and chemical durability, and is preferably contained in order to significantly improve CS.

The content of ZrO ₂ is preferably 0.2% or more, more preferably 0.5% or more, further preferably 1% or more, particularly preferably 2% or more, and most preferably 2.5% or more.

On the other hand, in order to suppress devitrification during melting, the ZrO ₂ content is preferably 5% or less, preferably 4.7% or less, more preferably 4.4% or less, further preferably 4% or less, particularly preferably 3.7% or less, and most preferably 3.5% or less.

_TiO2 is not essential, but is a component that suppresses the solarization of the glass and is a component that promotes crystallization when obtaining crystallized glass, and can be contained. The content of TiO2 _when contained is preferably 0.1% or more, more preferably 0.5% or more, further preferably 1% or more, particularly preferably 1.5% or more, and most preferably 2% or more. On the other hand, in order to suppress devitrification during melting, the content of _TiO2 is preferably 5% or less, preferably 4.7% or less, more preferably 4.4% or less, further preferably 4% or less, particularly preferably 3.7% or less, and most preferably 3.5% or less.

_SnO2 is not essential, but it has the function of serving as a clarifier during glass manufacturing and has the function of promoting the generation of crystal nuclei when obtaining crystallized glass, so it may be contained. When _SnO2 is contained, the content is preferably 0.02% or more, more preferably 0.05% or more, further preferably 0.08% or more, particularly preferably 0.1% or more, and most preferably 0.12% or more. On the other hand, in order to suppress devitrification during melting, the content of _SnO2 is preferably 5% or less, preferably 3% or less, more preferably 2% or less, further preferably 1% or less, particularly preferably 0.5% or less, and most preferably 0.3% or less.

La ₂ O ₃ , Nb ₂ O ₅ , and Ta ₂ O ₅ are all components that make it difficult for fragments to fly when the chemically strengthened glass is broken, and they may be contained in order to increase the refractive index. When they are contained, the total content of La ₂ O ₃ , Nb ₂ O ₅ , and Ta ₂ O ₅ (hereinafter referred to as La ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. In order to make the glass less likely to devitrify during melting, La ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less.

In addition, CeO ₂ may be contained. CeO ₂ may suppress coloring by oxidizing the glass. When CeO ₂ is contained, the content is preferably 0.03% or more, more preferably 0.05% or more, and further preferably 0.07% or more. In order to improve transparency, the content of CeO ₂ is preferably 1.5% or less, and more preferably 1.0% or less.

When chemically strengthened glass is colored for use, a coloring component may be added within a range that does not inhibit the realization of desired chemical strengthening characteristics. Examples of _the coloring component include _Co3O4 , _MnO2 , _{Fe2O3 , NiO} , CuO _{, Cr2O3 , V2O5 , Bi2O3} , _SeO2 , _Er2O3 , _{and Nd2O3} .

When Fe ₂ O ₃ is contained, its content is 0.5% or less. The content of the coloring components is preferably in the range of 1% or less in total. When it is desired to further increase the visible light transmittance of the glass, it is preferred that these components are not substantially contained.

_HfO2 , _Nb2O5 , and _Ti2O3 may be added to improve the weather resistance to ultraviolet light. When added for the purpose of improving the weather resistance to ultraviolet light, the total content of _HfO2 , _{Nb2O5 ,} and _Ti2O3 is preferably ₁ % or less, _more preferably 0.5% or less, and even more preferably 0.1% or less in order to suppress the influence on other _properties .

In addition, as a clarifier during glass melting, SO ₃ , chlorides, and fluorides may be appropriately contained. If the total content of the components that function as clarifiers is excessively added, it will affect the strengthening characteristics and crystallization behavior. Therefore, it is preferably 2% or less, more preferably 1% or less, and further preferably 0.5% or less, expressed in mass % based on oxides. There is no particular lower limit, but typically, the total is preferably 0.05% or more, expressed in mass % based on oxides.

When SO ₃ is used as a clarifier, if the content of SO ₃ is too small, no effect can be seen. Therefore, it is preferably 0.01% or more, more preferably 0.05% or more, and further preferably 0.1% or more, expressed as mass % based on oxides. In addition, when SO ₃ is used as a clarifier, the content of SO ₃ is preferably 1% or less, more preferably 0.8% or less, and further preferably 0.6% or less, expressed as mass % based on oxides.

When Cl is used as a clarifier, if the Cl content is excessively added, it will affect physical properties such as strengthening characteristics, so it is preferably 1% or less, more preferably 0.8% or less, and further preferably 0.6% or less, expressed as mass % based on oxides. In addition, if the Cl content is too small when Cl is used as a clarifier, no effect is observed, so it is preferably 0.05% or more, more preferably 0.1% or more, and further preferably 0.2% or more, expressed as mass % based on oxides.

It is preferred that As ₂ O ₃ is not contained. When As ₂ O ₃ is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably not contained.

The glass for chemical strengthening according to the first embodiment may be amorphous glass or crystallized glass.

(Second embodiment)

The parent composition of the chemically strengthened glass according to the second embodiment of the present invention preferably contains 40 to 70% of SiO ₂ , 10 to 35% of Li ₂ O, and 1 to 15% of Al ₂ O ₃ , expressed in mol % based on oxides.

As one aspect of the chemically strengthened glass of the second embodiment, it is preferred that, expressed in mol % based on oxides, it contains 40 to 70% _SiO2 , 10 to 35% _Li2O , ₁ to 15% _{Al2O3 ,} 0.5 to 5% _P2O5 , 0.5 to 5% _ZrO2 , 0 to 10% _{B2O3 ,} 0 to 3% _Na2O , 0 to 1% _K2O , and 0 to 4% _SnO2 .

In this specification, the crystallized glass having the above composition is also referred to as "the present crystallized glass x".

As another aspect of the chemically strengthened glass of the second embodiment, it is preferred that, expressed in mol % based on oxides, it contains 50 to 70% of _SiO2 , 15 to 30% of _Li2O , ₁ to 10% of _Al2O3 , 0.5 to 5% of _{P2O5 ,} 0.5 to 8% of _ZrO2 , 0.1 to 10% of MgO, 0 to 5% of _Y2O3 , 0 to 10% of _B2O3 , 0 to 3% of _Na2O , 0 to ₁ % of _K2O , _and 0 to 2% of _SnO2 .

In this specification, the crystallized glass having the above composition is also referred to as "the present crystallized glass y".

In this specification, the crystallized glass of this embodiment including the crystallized glass x and the crystallized glass y is also collectively referred to as the crystallized glass. In the crystallized glass, the total amount of SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ and B ₂ O ₃ is preferably 60 to 80% in terms of mole % based on oxides. SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ and B ₂ O ₃ are network-forming components of the glass (hereinafter, also referred to as NWF). By increasing the total amount of these NWFs, the strength of the glass becomes higher. The fracture toughness value of the crystallized glass is thereby increased, so the total amount of NWF is preferably 60% or more, more preferably 63% or more, and particularly preferably 65% or more. However, the melting temperature of the glass with too much NWF becomes higher, making the manufacturing difficult, so it is preferably 85% or less, more preferably 80% or less, and more preferably 75% or less.

In the present crystallized glass, _the ratio of the _total amount of _Li2O , _Na2O and _K2O to the total amount of NWF, namely, _SiO2 , _Al2O3 , _{P2O5 and B2O3} is preferably 0.20 to 0.60.

Li ₂ O, Na ₂ O and K ₂ O are network modifying components, and reducing the ratio relative to NWF increases the gaps in the network and improves impact resistance. Therefore, the ratio of the total amount of Li ₂ O, Na ₂ O and K ₂ O relative to NWF is preferably 0.60 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less. On the other hand, these components are components required for chemical strengthening, so in order to improve the chemical strengthening characteristics, the ratio of the total amount of Li ₂ O, Na ₂ O and K ₂ O relative to NWF is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.30 or more.

Hereinafter, the glass composition will be described.

In the present amorphous glass, SiO ₂ is a component that forms a network structure of the glass. In addition, as a component to improve chemical durability, the content of SiO ₂ is preferably 45% or more. The content of SiO ₂ is more preferably 48% or more, further preferably 50% or more, particularly preferably 52% or more, and extremely preferably 54% or more. On the other hand, in order to make the meltability good, the content of SiO ₂ is preferably 70% or less, more preferably 68% or less, further preferably 66% or less, and particularly preferably 64% or less.

_Al2O3 is _a component that increases the surface compressive stress generated by chemical strengthening and is essential. The content of _Al2O3 is preferably 1 _% or more, more preferably 2% or more, further preferably 3% or more, 5% or more, 5.5% or more, 6% or more in the following order, particularly preferably 6.5% or more, and most preferably 7% or more. On the other hand, in order not to make the devitrification temperature of the glass too high, the content of _{Al2O3 is} preferably 15% or less, more preferably 12% or less, further preferably 10% or less, particularly preferably 9% or less, and most preferably 8% or less.

_Li2O is a component that forms surface compressive stress by ion exchange, and is essential because it is a constituent component of the main crystal. The content of _Li2O is preferably 10% or more, more preferably 14% or more, more preferably 15% or more, further preferably 18% or more, particularly preferably 20% or more, and most preferably 22% or more. On the other hand, in order to stabilize the glass, the content of _Li2O is preferably 35% or less, more preferably 32% or less, further preferably 30% or less, particularly preferably 28% or less, and most preferably 26% or less.

_Na2O is a component that improves the meltability of glass. _Na2O is not essential, but when contained, it is preferably 0.5% or more, more preferably 1% or more, and particularly preferably 2% or more. If _Na2O is too much, crystals such as _{Li3PO4 ,} which are main crystals, are not easily precipitated, or the chemical strengthening characteristics are reduced, so the content of _Na2O is preferably 10% or less, more preferably 9% or less, further preferably 8% or less, and particularly preferably 7% or less.

_K2O , like _Na2O , is a component that lowers the melting temperature of glass and may be contained. When _K2O is contained, the content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. If _K2O is too much, chemical strengthening characteristics are reduced or chemical durability is reduced, so it is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, particularly preferably 2% or less, and most preferably 1% or less.

In order to improve the solubility of glass raw materials, the total content of Na ₂ O and K ₂ O (Na ₂ O+K ₂ O) is preferably 1% or more, more preferably 2% or more.

Furthermore, if the ratio of _K2O content to the total content of _Li2O , _Na2O and _K2O (hereinafter referred to as _{R2O ) is 0.2 or less, chemical strengthening characteristics can be improved and chemical durability can be improved, which is preferred. K2O / R2O is} more preferably 0.15 or less, and even more preferably 0.10 or less.

In addition, R ₂ O is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. In addition, R ₂ O is preferably 29% or less, and more preferably 26% or less.

_P2O5 is a constituent of _{Li3PO4 crystals} and is essential. In order to promote crystallization, the content _{of P2O5} is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and extremely preferably 2.5% or more. On the other hand, if the content _{of P2O5} is too high, phase separation is likely to occur during melting, and the acid resistance is significantly reduced. Therefore, the content of _P2O5 is preferably 5 _% or less, more preferably 4.8% or less, further preferably 4.5% or less, and particularly preferably 4.2% _or less.

_ZrO2 is a component that improves mechanical strength and chemical durability, and is preferably contained in order to significantly improve CS. The content of _ZrO2 is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. On the other hand, in order to suppress devitrification during melting, _ZrO2 is preferably 8% or less, more preferably 7.5% or less, further preferably 7% or less, and particularly preferably 6% or less. If the content of _ZrO2 is too much, the viscosity decreases due to the increase in the devitrification temperature. In order to suppress the deterioration of moldability due to the decrease in viscosity, when the molding viscosity is low, the content of _ZrO2 is preferably 5% or less, more preferably 4.5% or less, and further preferably 3.5% or less.

In order to improve chemical durability, _ZrO2 / _R2O is preferably 0.02 or more, more preferably 0.03 or more, further preferably 0.04 or more, particularly preferably 0.1 or more, and most preferably 0.15 or more. In order to improve transparency after crystallization, _ZrO2 / _R2O is preferably 0.6 or less, more preferably 0.5 or less, further preferably 0.4 or less, and particularly preferably 0.3 or less.

MgO is a component that stabilizes the glass and also a component that improves mechanical strength and chemical resistance. It is preferably contained when the Al ₂ O ₃ content is low. The MgO content is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, and particularly preferably 4% or more. On the other hand, if MgO is excessively added, the viscosity of the glass decreases and devitrification or phase separation is likely to occur. Therefore, the MgO content is preferably 10% or less, more preferably 9% or less, further preferably 8% or less, and particularly preferably 7% or less.

TiO ₂ is a component that promotes crystallization and can be contained. TiO ₂ is not essential, but when contained, it is preferably 0.2% or more, more preferably 0.5% or more. On the other hand, in order to suppress devitrification during melting, the content of TiO ₂ is preferably 4% or less, more preferably 2% or less, and further preferably 1% or less.

SnO ₂ has the function of promoting the formation of crystal nuclei and can be contained. SnO ₂ is not essential, but when contained, it is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, in order to suppress devitrification during melting, the content of SnO ₂ is preferably 6% or less, more preferably 5% or less, further preferably 4% or less, and particularly preferably 3% or less.

_Y2O3 is a component that has the effect of making it difficult for fragments to scatter when the chemically strengthened glass is broken, and may be contained. The content of _Y2O3 is preferably 1% or more, more preferably 1.5% or more, further preferably 2% or more, particularly preferably 2.5% _or more, and extremely preferably 3% _or more. On the other hand, in _order to suppress devitrification during melting, the content of _Y2O3 is preferably 5% or less, more preferably 4% or less.

B ₂ O ₃ is a component that improves the chipping resistance of the chemically strengthened glass or the chemically strengthened glass and improves the meltability, and may be contained. In order to improve the meltability, the content of B ₂ O ₃ when contained is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. On the other hand, if the content of B ₂ O ₃ is too high, striae are generated during melting, or phase separation is easily caused, which easily reduces the quality of the chemically strengthened glass, so it is preferably 5% or less. The content of B ₂ O ₃ is more preferably 4% or less, further preferably 3% or less, and particularly preferably 2% or less.

BaO, SrO, MgO, CaO and ZnO are all components that improve the solubility of glass and can be contained. When these components are contained, the total content of BaO, SrO, MgO, CaO and ZnO (hereinafter referred to as BaO+SrO+MgO+CaO+ZnO) is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, since the ion exchange rate is reduced, BaO+SrO+MgO+CaO+ZnO is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, and particularly preferably 4% or less.

Among them, BaO, SrO, and ZnO can be contained in order to increase the refractive index of the residual glass and make it close to the precipitated crystal phase, thereby increasing the light transmittance of the crystallized glass and reducing the haze value. At this time, the total content of BaO, SrO and ZnO (hereinafter referred to as BaO+SrO+ZnO) is preferably 0.3% or more, more preferably 0.5% or more, further preferably 0.7% or more, and particularly preferably 1% or more. On the other hand, these components sometimes reduce the ion exchange rate. In order to make the chemical strengthening characteristics good, BaO+SrO+ZnO is preferably 2.5% or less, more preferably 2% or less, further preferably 1.7% or less, and particularly preferably 1.5% or less.

La ₂ O ₃ , Nb ₂ O ₅ and Ta ₂ O ₅ are all components that make it difficult for fragments to fly when the chemically strengthened glass is broken, and can be contained in order to increase the refractive index. When these components are contained, the total content of La ₂ O ₃ , Nb ₂ O ₅ and Ta ₂ O ₅ (hereinafter referred to as La ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. In order to make the glass less likely to devitrify during melting, La ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less.

In addition, CeO ₂ may be contained. CeO ₂ may suppress coloring by oxidizing the glass. When CeO ₂ is contained, the content is preferably 0.03% or more, more preferably 0.05% or more, and further preferably 0.07% or more. In order to improve transparency, the content of CeO ₂ is preferably 1.5% or less, and more preferably 1.0% or less.

When the tempered glass is colored, a coloring component may be added within a range that does not inhibit the desired chemical strengthening characteristics. Examples of _the coloring component include _Co3O4 , _MnO2 , _Fe2O3 , _NiO , _{CuO , Cr2O3 , V2O5 , Bi2O3} , _SeO2 , _Er2O3 , _{and Nd2O3} .

The total content of the coloring components is preferably in the range of 1% or less. When it is desired to further increase the visible light transmittance of the glass, it is preferred that these components are substantially not contained.

In addition, SO ₃ , chlorides, and fluorides may be appropriately contained as a clarifier during glass melting, etc. Preferably, As ₂ O ₃ is not contained. When As ₂ O ₃ is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably, it is not contained.

The chemically strengthened glass according to the second embodiment is preferably crystallized glass.

Here, when the chemically strengthened glass of the first embodiment and the second embodiment is a crystallized glass, the composition obtained by summing the composition of the crystal phase and the glass phase of the crystallized glass is preferably within the above range. The composition of the crystallized glass is obtained as follows: the crystallized glass is heat treated at a temperature above the melting point, vitrified, and the obtained substance is analyzed. As a method for analyzing the glass composition, X-ray fluorescence analysis can be cited.

When the chemically strengthened glass of the first embodiment and the second embodiment is a crystallized glass, the type of crystal is not particularly limited, and for example, it preferably contains one or more crystals selected from lithium silicate crystals, lithium aluminum silicate crystals, and lithium phosphate crystals. As lithium silicate crystals, lithium metasilicate crystals and lithium disilicate crystals are preferred. As lithium phosphate crystals, lithium orthophosphate crystals are preferred. As lithium aluminum silicate crystals, β-spodumene crystals and petalite crystals are preferred.

When the chemically strengthened glass of the first embodiment and the second embodiment is a crystallized glass, the crystallization rate of the crystallized glass is not particularly limited. In order to improve the mechanical strength, it is preferably 10% or more, more preferably 15% or more, further preferably 20% or more, and particularly preferably 25% or more. In addition, in order to improve the transparency, it is preferably 70% or less, more preferably 60% or less, and particularly preferably 50% or less. A small crystallization rate is also excellent in terms of easy bending and molding by heating. The crystallization rate can be calculated by the Rietveld method from the X-ray diffraction intensity. The Rietveld method is recorded in the "Crystallization Analysis Handbook" Editorial Committee of the Japanese Crystallography Society, "Crystallization Analysis Handbook" (Kyoritsu Publishing 1999 Annual, p492~499).

The chemically strengthened glass of the present embodiment includes the chemically strengthened glasses of the third to sixth embodiments described below.

(Third embodiment)

In the chemically strengthened glass according to the third embodiment of the present invention, K-DOL as defined below is 4.2 μm or more, and the surface resistivity is 11 [logΩ/sq] or more.

K-DOL (μm): The depth of the compressive stress layer generated by potassium ions from the glass surface

As described above, it is believed that chemically strengthened glass having a compressive stress layer generated by potassium ions of relatively large size is likely to have high resistance. Here, a larger K-DOL means that the depth of the compressive stress layer generated by potassium ions is relatively large. That is, with the chemically strengthened glass of the third embodiment, a high-resistance compressive stress layer generated by potassium ions is formed deeply, so that chemically strengthened glass having a large surface resistivity can be obtained.

In the chemically strengthened glass of the third embodiment, K-DOL is 4.2 μm or more, preferably 5.0 μm or more, more preferably 6.0 μm or more, further preferably 8.0 μm or more, particularly preferably 10.0 μm or more, and most preferably 12.0 μm or more. On the other hand, from the viewpoint of maintaining high deep stress caused by Na ions, K-DOL is preferably 30 μm or less, more preferably 25 μm or less, further preferably 20 μm or less, particularly preferably 18 μm or less, and most preferably 15 μm or less.

In the chemically strengthened glass according to the third embodiment, the surface resistivity is 11 [logΩ/sq] or more, preferably 11.5 [logΩ/sq] or more, and more preferably 12 [logΩ/sq] or more.

(Fourth embodiment)

In the chemically strengthened glass according to the fourth embodiment of the present invention, K-CSarea defined below is 4000 Pa·m or more, and the surface resistivity is 11 [logΩ/sq] or more.

K-CSarea (Pa·m): product of K-CS ₀ and K-DOL

K-CS ₀ (MPa): Compressive stress value of the glass surface measured by a glass surface stress meter K-DOL (μm): Depth of the compressive stress layer generated by potassium ions from the glass surface

As described above, it is considered that chemically strengthened glass having a compressive stress layer generated by potassium ions of larger size is likely to have high resistance. Here, a larger K-CSarea means that the total amount of compressive stress generated by potassium ions is larger. That is, with the chemically strengthened glass of the fourth embodiment, since the total amount of compressive stress generated by potassium ions is large, a chemically strengthened glass with a large surface resistivity can be obtained.

In the chemically strengthened glass of the fourth embodiment, K-CSarea is preferably 4000 Pa·m or more, and the following are preferably 4100 Pa·m or more, 4700 Pa·m or more, 5000 Pa·m or more, more preferably 6000 Pa·m or more, and most preferably 10000 Pa·m or more. On the other hand, from the viewpoint of maintaining the deep stress generated by Na ions at a high level, K-CSarea is preferably 50000 Pa·m or less, more preferably 40000 Pa·m or less, further preferably 30000·Pa·m or less, particularly preferably 20000 Pa·m or less, and most preferably 18000 Pa·m or less.

In the chemically strengthened glass according to the fourth embodiment, the surface resistivity is 11 [logΩ/sq] or more, preferably 11.5 [logΩ/sq] or more, and more preferably 12 [logΩ/sq] or more.

(Fifth embodiment)

In the chemically strengthened glass of the fifth embodiment of the present invention, the ratio of K ₂ O concentration at a depth of 3 μm from the glass surface, i.e., K ₂ O@3 μm, to K ₂ O concentration at the center of the plate thickness, i.e., K ₂ O@center, is 5.3 or more, and the surface resistivity is 11 [logΩ/sq] or more.

The ratio of _K2O @3μm to _K2O @center being 5.3 or more means that the total amount of potassium ions is large in the range up to a depth of 3μm. That is, according to the chemically strengthened glass of the fifth embodiment, a high-resistance compressive stress layer caused by potassium ions is sufficiently formed, and chemically strengthened glass having a large surface resistivity can be obtained.

In the chemically strengthened glass of the fifth embodiment, the ratio of K ₂ O @ 3 μm to K ₂ O @ center is 5.3 or more, preferably 5.5 or more, more preferably 6.0 or more, and even more preferably 6.5 or more. On the other hand, from the viewpoint of maintaining high deep stress due to Na ions, the value is preferably 20 or less, more preferably 18 or less, even more preferably 15 or less, particularly preferably 12 or less, and most preferably 11 or less.

In the chemically strengthened glass of the fifth embodiment, the surface resistivity is 11 [logΩ/sq] or more, preferably 11.5 [logΩ/sq] or more, and more preferably 12 [logΩ/sq] or more. The upper limit of the surface resistivity is not particularly limited.

(Sixth embodiment)

In the chemically strengthened glass according to the sixth embodiment of the present invention, the ratio of the Li ₂ O concentration at a depth of 5 μm from the glass surface to the Li ₂ O concentration at the center of the plate thickness is 0.85 or less, and the surface resistivity is 11 [logΩ/sq] or more.

The ratio of the Li ₂ O concentration at a depth of 5 μm from the glass surface, i.e., Li ₂ O@5 μm, to the Li ₂ O concentration at the center of the plate thickness, i.e., Li ₂ O@center, being 0.85 or less means that the total amount of lithium ions in the range up to a depth of 5 μm is small. Lithium ions are relatively small in size among alkali metal ions. Therefore, when lithium ions exist in the surface layer of chemically strengthened glass, if other alkali metal ions exist in the surroundings, although it is possible to bring about high resistance due to the mixed alkali effect, it is difficult to obtain the effect brought about by the size of the replaced alkali metal ions, and it is believed that it will work in the direction of reducing resistance. In contrast, the chemically strengthened glass using the sixth embodiment has a small amount of lithium ions contained in the surface layer, and the effect brought about by the size of the replaced alkali metal ions can be fully obtained. As a result, a chemically strengthened glass with a large surface resistivity formed with a high-resistance compressive stress layer can be obtained.

In the chemically strengthened glass of the sixth embodiment, the ratio of Li ₂ O @ 5 μm to Li ₂ O @ center is 0.85 or less, preferably 0.84 or less, more preferably 0.82 or less, further preferably 0.80 or less, and most preferably 0.77 or less. On the other hand, from the viewpoint of improving the property of introducing Na ions deeply into the glass by ion exchange, the value is preferably 0 or more, more preferably 0.1 or more, further preferably 0.2 or more, particularly preferably 0.3 or more, and most preferably 0.4 or more.

In the chemically strengthened glass of the sixth embodiment, the surface resistivity is 11 [logΩ/sq] or more, preferably 11.5 [logΩ/sq] or more, and more preferably 12 [logΩ/sq] or more. The upper limit of the surface resistivity is not particularly limited.

In the chemically strengthened glass of the present embodiment, the value of Y defined below is preferably 9.4 or more.

Y＝0.000208x ₁ +4.3×10 ^-7 x ₂ +8.8

x ₁ ： K-CSarea (Pa·m), the product of K-CS ₀ and K-DOL

x ₂ ：Na-CS area (Pa·m), the product of Na-CS ₀ and Na-DOL

K-CS ₀ (MPa): Compressive stress value of the glass surface measured by a glass surface stress gauge

K-DOL (μm): The depth of the compressive stress layer generated by potassium ions from the glass surface. Na-CS ₀ (MPa): The compressive stress value of the glass surface measured by a scattered light photoelastic stress meter.

Na-DOL (μm): The depth of the compressive stress layer generated by Na ions from the glass surface

FIG3 is a graph showing the relationship between the value of Y and the measured value of volume resistivity of the chemically strengthened glass in the embodiment of the present invention. As shown in FIG3 , the present inventors found that the value of Y is sufficiently correlated with the volume resistivity of the chemically strengthened glass, and there is a tendency that the volume resistivity of the chemically strengthened glass increases as the value of Y increases. That is, in the present embodiment, a chemically strengthened glass with a large volume resistivity can be obtained by increasing the value of Y. Furthermore, it is known that increasing K-CSarea (x ₁ ) and increasing Na-CSarea (x ₂ ) are effective in increasing the value of Y, and increasing x ₁ is particularly effective.

The value of Y is preferably 9.4 or more, preferably 9.6 or more, more preferably 9.8 or more, further preferably 10 or more, further preferably 10.3 or more, particularly preferably 10.6 or more, and most preferably 10.9 or more. The upper limit of the value of Y is not particularly limited.

x ₁ represents the product of K- _CS0 and K-DOL, K-CSarea (Pa·m). K-CSarea is preferably 4000Pa·m or more, and the following are more preferably 4100Pa·m or more, 4700Pa·m or more, 5000Pa·m or more, further preferably 6000Pa·m or more, and particularly preferably 10000Pa·m or more. On the other hand, from the viewpoint of maintaining the deep stress generated by Na ions at a high level, K-CSarea is preferably 50000Pa·m or less, more preferably 40000Pa·m or less, further preferably 30000Pa·m or less, particularly preferably 20000Pa·m or less, and most preferably 18000Pa·m or less.

_x2 represents the product Na-CSarea (Pa·m) of Na- _CS0 and Na-DOL. From the viewpoint of improving drop strength, when the thickness of the glass is t (mm), Na-CSarea is preferably (10000×t+1000)Pa·m or more, more preferably (10000×t+6000)Pa·m or more, further preferably (10000×t+16000)Pa·m or more, particularly preferably (10000×t+26000)Pa·m or more, and most preferably (10000×t+31000)Pa·m or more. On the other hand, from the viewpoint of suppressing the stress possessed by the glass to the tensile stress of the CT limit, Na-CSarea is preferably less than (140000×t+2000)Pa·m, more preferably less than (140000×t-8000)Pa·m, further preferably less than (140000×t-18000)Pa·m, particularly preferably less than (140000×t-28000)Pa·m, and most preferably less than (140000×t-30000)Pa·m.

If a compressive stress layer is formed on the surface of a glass article, a tensile stress (hereinafter also referred to as CT) corresponding to the total amount of the compressive stress on the surface will inevitably be generated in the center of the glass article. If the tensile stress value is too large, the glass article will break violently and fragments will fly when it is broken. If CT exceeds this threshold value (hereinafter also referred to as CT limit), the number of broken pieces when damaged increases sharply.

Therefore, chemically strengthened glass increases the compressive stress on the surface and forms a compressive stress layer to a deeper portion, while on the other hand, the total amount of compressive stress on the surface is designed so as not to exceed the CT limit (for example, U.S. Patent No. 9487434, U.S. Patent Application Publication No. 2017/355640, U.S. Patent No. 9593042, or Japanese Patent Application Publication No. 2019-513663).

(Chemically strengthened glass)

As more preferable aspects of the chemically strengthened glass according to each of the above-mentioned embodiments, the following aspects can be mentioned.

From the viewpoint of improving the flexural strength, K-CS ₀ (MPa) is preferably 800 MPa or more, more preferably 850 MPa or more, further preferably 900 MPa or more, particularly preferably 950 MPa or more, and most preferably 1000 MPa or more.

From the viewpoint of improving drop strength, when the thickness of the glass is t (mm), Na-DOL (μm) is preferably (50×t-15) μm or more, more preferably (50×t+25) μm or more, further preferably (50×t+45) μm or more, particularly preferably (50×t+65) μm or more, and most preferably (50×t+85) μm or more. On the other hand, from the viewpoint of suppressing the stress possessed by the glass to a tensile stress below the CT limit, Na-DOL is preferably (100×t+95) μm or less, more preferably (100×t+90) μm or less, further preferably (100×t+88) μm or less, particularly preferably (100×t+86) μm or less, and most preferably (100×t+84) μm or less.

From the viewpoint of improving drop strength, Na-CS ₀ (MPa) is preferably 150 MPa or more, more preferably 200 MPa or more, further preferably 250 MPa or more, particularly preferably 280 MPa or more, and most preferably 300 MPa or more. On the other hand, from the viewpoint of suppressing the stress possessed by the glass to the tensile stress below the CT limit, Na-CS ₀ is preferably 650 MPa or less, more preferably 600 MPa or less, further preferably 580 MPa or less, particularly preferably 550 MPa or less, and most preferably 520 MPa or less.

From the viewpoint of improving bending strength, the compressive stress value CS ₁ (MPa) at a depth of 1 μm from the glass surface is preferably 700 MPa or more, more preferably 750 MPa or more, further preferably 800 MPa or more, particularly preferably 850 MPa or more, and most preferably 900 MPa or more.

From the viewpoint of improving bending strength, the compressive stress value CS ₂ (MPa) at a depth of 2 μm from the glass surface is preferably 550 MPa or more, more preferably 600 MPa or more, further preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 750 MPa or more.

From the viewpoint of improving drop strength, when the thickness of the glass is t (mm), the compressive stress value CS ₅₀ (MPa) at a depth of 50 μm from the glass surface is preferably (140×t) MPa or more, more preferably (140×t+20) MPa or more, further preferably (140×t+30) MPa or more, particularly preferably (140×t+40) MPa or more, and most preferably (140×t+50) MPa or more.

From the viewpoint of improving drop strength, when the thickness of the glass is t (mm), the compressive stress value CS ₉₀ (MPa) at a depth of 90 μm from the glass surface is preferably (40×t) MPa or more, more preferably (40×t+5) MPa or more, further preferably (40×t+10) MPa or more, particularly preferably (40×t+20) MPa or more, and most preferably (40×t+30) MPa or more.

CTave (MPa) is a value equivalent to the average value of tensile stress obtained by the above method. From the viewpoint of improving drop strength, when the thickness of the glass is t (mm), CTave is preferably (-50×t+88)MPa or more, more preferably (-50×t+90)MPa or more, further preferably (-50×t+91)MPa or more, and most preferably (-50×t+92)MPa or more. On the other hand, from the viewpoint of suppressing the stress possessed by the glass to a tensile stress below the CT limit, CTave is preferably smaller than the value of CTA obtained according to formula (1).

t: Plate thickness (mm)

K1c: Fracture toughness value (MPa·m ^1/2 )

The value obtained by subtracting the CTave value from the CTA is preferably 1 MPa or more, more preferably 2 MPa or more, and most preferably 3 MPa or more.

ICT (Pa·m) represents the integral value of tensile stress. From the viewpoint of improving drop strength, when the thickness of the glass is t (mm), ICT is preferably (32235×t+1000)Pa·m or more, more preferably (32235×t+2000)Pa·m or more, further preferably 32235×t+3000)Pa·m or more, particularly preferably 32235×t+4000)Pa·m or more, and most preferably (32235×t+5000Pa·m or more. On the other hand, From the perspective of suppressing the stress of the glass to a tensile stress below the CT limit, ICT is preferably less than (32235×t+27000)Pa·m, preferably less than (32235×t+25000)Pa·m, further preferably less than (32235×t+23000)Pa·m, particularly preferably less than (32235×t+20000)Pa·m, and most preferably less than (32235×t+15000)Pa·m.

(Chemically strengthened glass and chemically strengthened glass)

The chemically strengthened glass and the chemically strengthened glass according to the above-mentioned respective embodiments will be described.

The shape of the chemically strengthened glass or chemically strengthened glass is not particularly limited, and is typically in the form of a plate, and may be in the form of a flat plate or a curved surface. In addition, the glass may have portions with different thicknesses.

When the chemically strengthened glass or chemically strengthened glass is in the form of a plate, its thickness (t) is preferably 3000 μm or less, more preferably 2000 μm or less, 1600 μm or less, 1500 μm or less, 1100 μm or less, 900 μm or less, 800 μm or less, or 700 μm or less in stages. In addition, in order to obtain sufficient strength by chemical strengthening treatment, the thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and further preferably 500 μm or more.

The chemically strengthened glass of the embodiment of the present invention is easily obtained by chemical strengthening treatment. Chemically strengthened glass with high resistance is suitable for obtaining chemically strengthened glass that can suppress abnormal luminescence. In addition, the chemically strengthened glass of the embodiment of the present invention can suppress abnormal luminescence by having high resistance, so it is particularly useful as a cover glass used in electronic devices such as mobile phones, smart phones and other mobile devices. Furthermore, it is also useful in the cover glass of electronic devices such as televisions, personal computers, touch panels, etc. that are not for the purpose of carrying, the wall surface of elevators, the wall surface of buildings such as houses or buildings (full-screen display). In addition, it is also useful as building materials such as window glass, desktops, interiors of cars or airplanes, etc., or their cover glass, and it is also useful in housings with curved shapes. That is, the present invention relates to an electronic device having a chemically strengthened glass of an embodiment of the present invention or a chemically strengthened glass of an embodiment of the present invention.

(Chemically strengthened glass and method for producing chemically strengthened glass)

The chemically strengthened glass and the method for producing the chemically strengthened glass according to the present embodiment will be described.

For example, when manufacturing a plate-shaped chemically strengthened glass, the glass raw materials are appropriately prepared in such a way as to obtain the glass of the above composition, and are heated and melted in a glass melting furnace. Thereafter, the glass is homogenized by bubbling, stirring, adding a clarifier, etc., and formed into a glass plate of a specified thickness, and slowly cooled to obtain a chemically strengthened glass. Alternatively, the chemically strengthened glass can be formed into a plate by forming it into a block and then cutting it after slowly cooling. When the chemically strengthened glass is a crystallized glass, it may further include a heat treatment step for crystallization.

As a method for forming into a plate, for example, a float process, a press process, a fusion process and a down-draw process can be cited. In particular, when a large glass plate is manufactured, the float process is preferred. In addition, continuous forming methods other than the float process, such as a fusion process and a down-draw process, are also preferred.

Chemically strengthened glass is obtained by subjecting chemically strengthened glass to ion exchange treatment. For example, as the manufacturing method of the glass of the third embodiment to the sixth embodiment described above, it is preferred that: the chemically strengthened glass is manufactured using the chemically strengthened glass of the first embodiment or the second embodiment; or the chemically strengthened glass is manufactured by chemically strengthening through the preferred chemical strengthening process described below, and it is more preferred that the composition of the glass of the first embodiment or the second embodiment is used as the mother composition and the chemically strengthened glass is manufactured by chemically strengthening through the preferred chemical strengthening process described below.

In the present embodiment, it is preferred to perform two-stage ion exchange treatment. However, there is no obstacle at all to obtain the chemically strengthened glass of each of the above-mentioned embodiments by performing one-stage ion exchange treatment or three or more-stage ion exchange treatment.

When the two-stage ion exchange treatment is performed, the first alkali metal ions in the chemically strengthened glass are exchanged with the second alkali metal ions in the first molten salt composition by the first ion exchange treatment. In addition, in the second ion exchange treatment, the second alkali metal ions in the chemically strengthened glass are exchanged with the third alkali metal ions in the second molten salt composition.

In this specification, "molten salt composition" refers to a composition containing a molten salt. As the molten salt contained in the molten salt composition, for example, nitrates, sulfates, carbonates, chlorides, etc. can be mentioned. As nitrates, for example, lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, rubidium nitrate, silver nitrate, etc. can be mentioned. As sulfates, for example, lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, rubidium sulfate, silver sulfate, etc. can be mentioned. As chlorides, for example, lithium chloride, sodium chloride, potassium chloride, cesium chloride, rubidium chloride, silver chloride, etc. can be mentioned. These molten salts can be used alone or in combination.

The molten salt composition preferably contains nitrate as a matrix, and more preferably contains sodium nitrate or potassium nitrate as a main component. Here, "main component" means that the content in the molten salt composition is 80% by mass or more.

The method for producing chemically strengthened glass according to the present embodiment is, for example, a method for producing chemically strengthened glass comprising a first ion exchange treatment of bringing a first molten salt composition into contact with a chemically strengthened glass; and a second ion exchange treatment of bringing a second molten salt composition into contact with the chemically strengthened glass after the first ion exchange treatment, wherein the second molten salt composition contains 94% by mass or more of potassium nitrate (KNO ₃ ) and less than 300 ppm by mass of lithium ions.

In the above production method, it is preferred that the temperature of the second molten salt composition in the second ion exchange treatment is 380° C. to 450° C., and the time for which the second molten salt composition is in contact with the chemically strengthened glass is 60 minutes or longer.

In the above production method, the second molten salt composition preferably contains 0 to 5 mass % of sodium nitrate (NaNO ₃ ).

The method for manufacturing chemically strengthened glass of the present embodiment may be, for example, a method for manufacturing chemically strengthened glass, which comprises subjecting a glass for chemical strengthening to ion exchange treatment to obtain chemically strengthened glass, and the obtained chemically strengthened glass has a K-DOL of 4.2 μm or more and a surface resistivity of 11 [logΩ/sq] or more.

The method for manufacturing chemically strengthened glass of the present embodiment may also be, for example, a method for manufacturing chemically strengthened glass, which comprises performing ion exchange treatment on a glass for chemical strengthening to obtain chemically strengthened glass, and the obtained chemically strengthened glass has a K-CSarea of 4000 Pa·m or more and a surface resistivity of 11 [logΩ/sq] or more.

Hereinafter, the first ion exchange treatment and the second ion exchange treatment will be described in detail.

＜＜First ion exchange treatment＞＞

In one embodiment, in the first ion exchange treatment, the chemically strengthened glass containing the first alkali metal ions is preferably brought into contact with the first molten salt composition containing the second alkali metal ions having an ion radius larger than the first alkali metal ions to perform ion exchange. In this embodiment, the second alkali metal ions are introduced into the chemically strengthened glass by the first ion exchange treatment.

The composition of the first molten salt composition used in the first ion exchange treatment is not particularly limited as long as the effect of the present invention is not impaired. As an embodiment, it preferably contains a second alkali metal ion having an ionic radius larger than that of the first alkali metal ion contained in the chemically strengthened glass. The first molten salt composition preferably further contains a third alkali metal ion having an ionic radius larger than that of the second alkali metal ion.

In one embodiment, when the first alkali metal ion is a lithium ion, the second alkali metal ion is preferably a sodium ion, and the third alkali metal ion is preferably a potassium ion.

Examples of the molten salt containing sodium ions used in the first ionic molten salt composition include sodium nitrate, sodium sulfate, and sodium chloride. Among these, sodium nitrate is preferred.

As one embodiment, when the first molten salt composition contains sodium nitrate, its content is preferably 20 mass % to 100 mass %. Here, the lower limit of the content is more preferably 25 mass % or more, and more preferably 30 mass % or more. In addition, the upper limit of the content is more preferably 80 mass % or less, and more preferably 60 mass % or less.

Examples of the molten salt containing potassium ions used in the first molten salt composition include potassium nitrate, potassium sulfate, and potassium chloride. Among these, potassium nitrate is preferred.

As one embodiment, when the first molten salt composition contains potassium nitrate, its content is preferably 20 mass % to 80 mass %. Here, the lower limit of the content is more preferably 30 mass % or more, more preferably 40 mass % or more, and most preferably 50 mass % or more. In addition, the upper limit of the content is more preferably 70 mass % or less, and more preferably 60 mass % or less.

In the first ion exchange treatment, the chemically strengthened glass is preferably brought into contact with a first molten salt composition preferably at a temperature of 380° C. or higher. If the temperature of the first molten salt composition is 380° C. or higher, ion exchange is easily performed. It is more preferably 400° C. or higher, further preferably 410° C. or higher, and particularly preferably 420° C. or higher. In addition, from the viewpoint of the danger caused by evaporation and the composition change of the molten salt composition, the temperature of the first molten salt composition is usually 450° C. or lower.

In the first ion exchange treatment, if the time for contacting the chemically strengthened glass with the first molten salt composition is 0.5 hours or more, the surface compressive stress becomes large, so it is preferred. The contact time is more preferably 1 hour or more. If the contact time is too long, not only the productivity decreases, but also the compressive stress is sometimes reduced due to the relaxation phenomenon. Therefore, the contact time is usually 8 hours or less.

The first ion exchange treatment may be a one-step treatment, or may be a treatment performed in two or more steps under two or more different conditions (multi-step strengthening).

＜＜Second ion exchange treatment＞＞

The second ion exchange treatment is a step of bringing a second molten salt composition having a component ratio different from that of the first molten salt composition into contact with the chemically strengthened glass to perform ion exchange after the first ion exchange treatment.

In the present production method, in the second ion exchange treatment, the second molten salt composition preferably contains a third alkali metal ion having a larger ion radius than the second alkali metal ion. In the second molten salt composition, the content of the first alkali metal ion is preferably small.

In one embodiment, when the second alkali metal ion is a sodium ion, the third alkali metal ion is preferably a potassium ion, and the first alkali metal ion is preferably a lithium ion.

Examples of the molten salt containing potassium ions used in the second molten salt composition include potassium nitrate, potassium sulfate, and potassium chloride. Among these, potassium nitrate is preferred.

As an embodiment, when the second molten salt composition contains potassium nitrate (KNO ₃ ), its content is preferably 94% by mass or more. Here, the lower limit of the content is more preferably 96% by mass or more, and more preferably 98% by mass or more. In addition, the upper limit of the content can be 100% by mass, preferably 99.5% by mass or less, and more preferably 99% by mass or less. When the second molten salt composition contains potassium nitrate, since its content is relatively large, it is easy to obtain the high resistance effect brought about by the size of the alkali metal ions replaced in the chemically strengthened glass, which is suitable for obtaining the chemically strengthened glass of this embodiment.

The second molten salt composition sometimes contains at least one of lithium ions and sodium ions. As the molten salt containing lithium ions used in the second molten salt composition, for example, lithium nitrate, lithium sulfate, and lithium chloride can be cited, and lithium nitrate is preferred among these. As the composition containing sodium ions used in the second molten salt composition, for example, sodium nitrate, sodium sulfate, and sodium chloride can be cited, and sodium nitrate is preferred among these.

In the second molten salt composition, the content of lithium ions is preferably less than 300 mass ppm, more preferably 200 mass ppm, 100 mass ppm, 80 mass ppm or less in the following order, and further preferably 60 mass ppm or less. Thus, it is possible to suppress the entry of lithium ions into the surface layer of the chemically strengthened glass and make the resistance lower. The content of lithium ions may be 0 mass ppm, but from the perspective of mass productivity of chemically strengthened glass, it may be 40 mass ppm or more. When the second molten salt composition contains lithium nitrate (LiNO ₃ ), it is preferred that the content of lithium ions in the second molten salt composition be within the above-mentioned preferred range.

When the second molten salt composition contains sodium nitrate (NaNO ₃ ), the content is preferably 0.5 mass % or more, more preferably 1 mass % or more, and further preferably 1.5 mass % or more. In addition, from the viewpoint of maintaining high surface stress, it is preferably 5 mass % or less, more preferably 4 mass % or less, and further preferably 3 mass % or less.

In the second ion exchange treatment, the chemically strengthened glass is preferably brought into contact with a second molten salt composition at a temperature of 450°C or less. By making the temperature of the second molten salt composition 450°C or less, the change of the molten salt composition can be suppressed. The temperature of the second molten salt composition is more preferably 440°C or less, further preferably 430°C or less, and particularly preferably 420°C or less. In addition, from the viewpoint of accelerating ion exchange, the temperature of the second molten salt composition is preferably 380°C or more, more preferably 390°C or more, and further preferably 400°C or more.

In the second ion exchange treatment, from the viewpoint of stable ion exchange, the time (treatment time) for contacting the chemically strengthened glass with the second molten salt composition is preferably 60 minutes or more, more preferably 90 minutes or more, and further preferably 120 minutes or more. On the other hand, from the viewpoint of decreased productivity when the contact time is too long, the contact time in the second ion exchange treatment is preferably 300 minutes or less, more preferably 240 minutes or less, and further preferably 180 minutes or less.

Example

Hereinafter, the present invention will be described using examples, but the present invention is not limited thereto.

＜Production of amorphous glass and crystallized glass＞

Glass raw materials were prepared to give the following composition expressed in terms of molar percentage based on oxides, and weighed to give 400 g of glass. The mixed raw materials were then placed in a platinum crucible and placed in an electric furnace at 1500 to 1700°C for melting for about 3 hours, followed by degassing and homogenization. The K1c of glass material A was 0.8 (MPa·m ^1/2 ).

Glass material A: _SiO2 66%, _{Al2O3 11} %, _{Y2O3 0.5} %, _ZrO2 1.3%, _Li2O 11%, _Na2O 5.5%, _K2O 1.5%, MgO 3%, other components 0.3%. The ratio of the total content of _Li2O , _Na2O and _K2O to _the content of _Al2O3 in glass material A ( _R2O / _{Al2O3 )} is 1.6.

Glass material B: _SiO2 65%, _{Al2O3 16} %, _{P2O5 1.2} %, _Li2O 7.5%, _Na2O 5%, _K2O 0.5%, MgO 0.5%, CaO 1.3%, _{B2O3 3} %. In glass material B, the ratio of the total content of _Li2O , _Na2O and _K2O to _the content of _Al2O3 ( _R2O / _{Al2O3 )} is 0.8.

Glass material C: _SiO2 70%, _{Al2O3 11.5} %, _P2O5 0.3%, _Li2O 9%, _Na2O 2.5%, _{K2O 0.2} %, MgO 0.8%, CaO 2.6%, ZrO2 0.1%, _{B2O3 3} %. In glass material C, the ratio of the total content of _Li2O , _Na2O and _K2O to _the content of _Al2O3 ( _R2O / _{Al2O3 )} is 1.0 _.

The obtained molten glass was cast into a metal mold, kept at a temperature about 50°C higher than the glass transition temperature for 1 hour, and then cooled to room temperature at a rate of 0.5°C/min to obtain a glass block. The obtained molten glass was cast into a mold, kept at a temperature near the glass transition temperature (714°C) for about 1 hour, and then cooled to room temperature at a rate of 0.5°C/min to obtain a glass block.

The obtained glass block was cut and ground, and finally both surfaces were mirror-polished to obtain a glass plate (chemically strengthened glass) having a size of 120 mm×60 mm and a thickness of 0.70 mm.

＜Chemical strengthening treatment and evaluation of chemically strengthened glass＞

The glass plate obtained above was immersed in a molten salt composition under the conditions shown in Tables 1 and 2, and the first ion exchange treatment and the second ion exchange treatment were performed to obtain chemically strengthened glasses of Examples 1 to 16. Examples 1, 2, 5, 6, 13 to 15, 17 and 18 are examples, and Examples 3, 4, 7 to 12 and 16 are comparative examples. The obtained chemically strengthened glasses were evaluated by the following method.

[Stress measurement using a scattered light photoelastic stress meter]

The stress of the chemically strengthened glass was measured using a scattered light photoelastic stress meter (SLP-2000 manufactured by Orihara Seisakusho Co., Ltd.) according to the method described in International Publication No. 2018/056121. In addition, the stress distribution diagram was calculated using the accompanying software [SlpV (Ver. 2019.11.07.001)] of the scattered light photoelastic stress meter (SLP-2000 manufactured by Orihara Seisakusho Co., Ltd.).

The function used to obtain the stress distribution diagram is σ(x) = [a ₁ × erfc(a ₂ × x) + a ₃ × erfc(a ₄ × x) + a ₅ ]. _{a i} ( _i = 1 to 5) is a fitting parameter, and erfc is a complementary error function. The complementary error function is defined by the following formula.

In the evaluation of this specification, the fitting parameters are optimized by minimizing the residual sum of squares between the obtained raw data and the above function. The measurement processing condition is single, the edge method is selected in the surface specification, 6.0μm is selected in the internal surface end specification, automatic is selected in the internal left and right end specification, automatic is selected in the internal deep end specification (sample film thickness center), and the extension specification of the phase curve to the sample thickness center is selected as the fitting curve.

The stress in the glass surface layer at a distance of several tens of μm or less from the glass surface was measured using a glass surface stress meter (FSM6000-UV manufactured by Orihara Manufacturing Co., Ltd.) according to the method described in International Publication No. 2018/056121 and International Publication No. 2017/115811.

Furthermore, the concentration distribution of alkali metal ions (sodium ions, potassium ions, and lithium ions) in the cross-sectional direction was simultaneously measured using EPMA (Electron Probe Micro Analyzer), and it was confirmed that the concentration distribution was consistent with the obtained stress distribution diagram.

In addition, the values of K-CS ₀ , K-DOL, K-CSarea, Na-CS ₀ , Na-DOL, Na-CSarea, CS ₁ , CS ₂ , CS ₅₀ , CS ₉₀ , CTmax, CTave, and ICT were obtained from the above measurement results and the obtained stress distribution diagram. The results are shown in Tables 1 and 2.

<Measurement of resistivity>

The surface resistivity and volume resistivity of the chemically strengthened glass of each example were measured by the following method.

(Glass sample preparation and film forming process)

The glass sample used was a 120mm×60mm×0.7mm glass sample. Film formation was performed according to the following steps before the surface resistivity was measured. A sputtering device was used to form a film on a 120×60×0.7mm glass sample. A platinum target was used as the target for film formation, and argon was introduced to form a 30nm platinum film on the glass surface. During film formation, 60mm patterning was performed based on JISR3256:1998.

(Surface resistivity)

The surface resistivity is measured by the following method.

An ultra-micro ammeter was used as the measuring device.

The surface resistivity was measured by a three-terminal method based on JIS C2141:1992 and JIS R3256:1998.

The applied voltage was 100 V, and the value was measured 180 seconds after the voltage was applied. The discharge time was 3 seconds.

(Volume resistivity)

The volume resistivity is measured by the following method.

An ultra-micro ammeter was used as the measuring device.

As the glass sample, a glass sample of 120×60×0.7 mm was used.

The measurement was based on JIS C2141: 1992 and JIS R3256: 1998 and was measured by a three-terminal method.

The applied voltage was 100 V, and the value was measured 180 seconds after the voltage was applied. The discharge time was 3 seconds.

The results are shown in Tables 1 and 2. In addition, Fig. 2 is a graph showing the relationship between the surface resistivity and the volume resistivity of the chemically strengthened glass of each example. Fig. 3 is a graph showing the relationship between the measured value of the volume resistivity of the chemically strengthened glass of each example and the value of Y. The value of Y is defined by the following formula.

Y＝-0.5984x ₁ +0.00018x ₂ +4.319×10 ^-7 x ₃ +8.5

x ₁ : LiNO ₃ concentration (mass %) in the molten salt used in the final ion exchange treatment during the chemical strengthening treatment

x ₂ ： K-CSarea (Pa·m), the product of K-CS ₀ and K-DOL

x ₃ ：Na-CS area (Pa·m), the product of Na-CS ₀ and Na-DOL

<K ₂ O concentration, Li ₂ O concentration>

The K ₂ O concentration at depth x (μm) and the Li ₂ O concentration at depth x (μm) were measured by the above method. K ₂ O@3μm, K ₂ O@center, Li ₂ O@5μm, and Li ₂ O@center were determined from the results. The results are shown in Tables 1 and 2.

Fig. 4 shows the _K2O distribution of the surface layers of Examples 1, 2, 4 and 5. As shown in Fig. 4, the concentration of potassium ions at 3 μm in the surface layer varies for each sample, and as shown in Tables 1 and 2, it can be confirmed that the potassium ions at 3 μm in the surface layer have a correlation with the surface resistivity or volume resistivity.

The explanation of each expression in Tables 1 and 2 is shown below.

K-CS ₀ : Compressive stress value due to potassium ions at a depth of 0 μm measured by FSM (MPa)

K-DOL: The depth of the compressive stress layer generated by potassium ions from the glass surface (μm)

K-CS area: CS ₀ ×K-DOL(Pa·m)

Na-CS ₀ : Compressive stress value due to Na ions at a depth of 0 μm measured by SLP (MPa)

Na-DOL: The depth of the compressive stress layer generated by sodium ions from the glass surface (μm)

Na-CS area: Na-CS ₀ ×Na-DOL (Pa·m)

CS _x : compressive stress value at a depth of X μm (MPa)

CTave＝ICT/L _CT (MPa)

ICT: Integrated value of tensile stress (Pa·m)

L _CT : Length of the tensile stress region in the plate thickness direction (μm)

CTmax: Maximum tensile stress

K ₂ O@3μm: K ₂ O concentration at a depth of 3μm from the surface (mol%)

K ₂ O@center: K ₂ O concentration at the center of the plate thickness (mol%)

Li ₂ O@3μm: Li ₂ O concentration at a depth of 3μm from the surface (mol%)

Li ₂ O@center: Li ₂ O concentration at the center of the plate thickness (mol%)

[Table 1]

[Table 2]

As shown in Tables 1 and 2, Examples 1, 2, 5, 6, 13 to 15, 17, and 18, in which K-DOL was 4.2 μm or more, had a surface resistivity greater than that of the comparative examples, being 11 [logΩ/sq] or more.

Examples 1, 2, 5, 6, 13 to 15, 17, and 18 in which K-CSarea was 4000 Pa·m or more had a surface resistivity greater than that of the comparative example, being 11 [logΩ/sq] or more.

Examples 1, 2, 5, 17 and 18, in which the ratio of K ₂ O concentration at a depth of 3 μm from the glass surface, K ₂ O@3 μm, to K ₂ O concentration at the center of the plate thickness, K ₂ O@center, was 5.5 or more, had a surface resistivity greater than that of the comparative example, being 11 [logΩ/sq] or more.

Examples 1, 5, 17 and 18, in which the ratio of Li ₂ O concentration at a depth of 5 μm from the glass surface, i.e., Li ₂ O@5 μm, to Li ₂ O concentration at the center of the plate thickness, i.e., Li ₂ O@center, was 0.85 or less, had a surface resistivity greater than that of the comparative example, i.e., 11 [logΩ/sq] or more.

While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the present invention.

This application is based on Japanese Patent Application No. 2023-075767 filed on May 1, 2023 and Japanese Patent Application No. 2024-071340 filed on April 25, 2024, the contents of which are incorporated into this specification as reference.

Claims (14)

1. A chemically strengthened glass contains, in terms of mole percent based on oxides, at least 50% of SiO ₂, 0 to 10% of B ₂O₃, 1 to 30% of Al ₂O₃, 0 to 10% of P ₂O₅, 0 to 10% of Y ₂O₃, 0 to 25% of Li ₂ O, 0 to 25% of Na ₂ O, 0 to 25% of K ₂ O, 0 to 10% of MgO, 0 to 10% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, 0 to 10% of ZnO, 0 to 5% of ZrO ₂, 0 to 5% of TiO ₂, 0 to 5% of SnO ₂, 0 to 0.5% of Fe ₂O₃,

R ₂O/Al₂O₃, which is the ratio of the total content of Li ₂O、Na₂ O and K ₂ O to the content of Al ₂O₃, satisfies the following formula (A),

(A)0.8≤(R₂O/Al₂O₃)≤30。

2. The chemically strengthened glass according to claim 1, wherein the glass contains, in terms of mole percent based on oxides, 7 to 12% of Li ₂ O, 1.5 to 6% of Na ₂ O, and 0 to 1.5% of K ₂ O.

3. A chemically strengthened glass having a K-DOL of 4.2 μm or more and a surface resistivity of 11log Ω/sq or more,

K-DOL is the value of the depth of the compressive stress layer from the glass surface in μm generated by potassium ions.

4. A chemically strengthened glass, wherein K-CSarea defined below is 4000 Pa.m or more and has a surface resistivity of 11log Ω/sq or more,

K-CSarea is the product of K-CS ₀ and K-DOL in Pa.m

K-CS ₀ is the compressive stress value of the glass surface measured by a glass surface stress meter, and the unit is MPa,

K-DOL is the value of the depth of the compressive stress layer from the glass surface in μm generated by potassium ions.

5. The chemically strengthened glass of claim 4, wherein the K-CS ₀ is 800MPa or greater.

6. A chemically strengthened glass having a ratio of a K ₂ O concentration of K ₂ O@3 mu m at a depth of 3 mu m from the surface of the glass to a K ₂ O concentration of K ₂ O@center at the center of the thickness of the glass of 5.3 or more,

The surface resistivity is 11log ohm/sq or more.

7. A chemically strengthened glass having a ratio of Li ₂ O concentration (Li ₂ O@5 μm) at a depth of 5 μm from the surface of the glass to Li ₂ O concentration (Li ₂ O@center) at the center of the plate thickness of 0.85 or less,

The surface resistivity is 11log ohm/sq or more.

8. A chemically strengthened glass according to claim 3, wherein Y defined below has a value of 9.4 or more,

Y＝0.00018x₁+4.319×10^-7x₂+8.5

X ₁ is the product of K-CS ₀ and K-DOL, K-CSarea, in Pa.m,

X ₂ is the product of Na-CS ₀ and Na-DOL, na-CSarea, in Pa.m,

K-CS ₀ is the compressive stress value of the glass surface measured by a glass surface stress meter, and the unit is MPa,

K-DOL is the value of the depth of the compressive stress layer from the glass surface, in μm,

Na-CS ₀ is the compressive stress value of the glass surface measured by a scattered light photoelastic stress meter, and the unit is MPa,

Na-DOL is the value of the depth of the compressive stress layer from the glass surface, in μm, generated by Na ions.

9. An electronic device comprising the chemically strengthened glass according to claim 1 or 2 or the chemically strengthened glass according to any one of claims 3 to 8.

10. A method of making chemically strengthened glass comprising:

ion exchange treatment 1, contacting the glass for chemical strengthening with the molten salt composition 1,

Ion exchange treatment 2, after the ion exchange treatment 1, bringing the molten salt composition 2 into contact with the glass for chemical strengthening,

In the molten salt composition of No. 2, KNO ₃ is 94% by mass or more and lithium ions are less than 300 ppm by mass.

11. The method for producing chemically strengthened glass according to claim 10, wherein the temperature of the 2 nd molten salt composition in the 2 nd ion exchange treatment is 380 ℃ to 450 ℃, and the time for bringing the 2 nd molten salt composition into contact with the glass for chemical strengthening is 60 minutes or longer.

12. The method for producing chemically strengthened glass according to claim 10 or 11, wherein the 2 nd molten salt composition contains 0 to 5 mass% NaNO ₃.

13. A method for producing chemically strengthened glass, comprising subjecting chemically strengthened glass to ion exchange treatment to obtain chemically strengthened glass,

K-DOL defined below is 4.2 μm or more and the surface resistivity is 11log Ω/sq or more,

K-DOL is the value of the depth of the compressive stress layer from the glass surface in μm generated by potassium ions.

14. A method for producing chemically strengthened glass, comprising subjecting chemically strengthened glass to ion exchange treatment to obtain chemically strengthened glass,

K-CSarea defined below is 4000 Pa.m or more, and the surface resistivity is 11log Ω/sq or more,

K-CSarea is the product of CS ₀ and K-DOL in Pa.m

CS ₀ is the compressive stress value of the glass surface, in MPa,

K-DOL is the value of the depth of the compressive stress layer from the glass surface in μm generated by potassium ions.