CN116715449A

CN116715449A - Chemically strengthened glass and method for producing same

Info

Publication number: CN116715449A
Application number: CN202310207202.2A
Authority: CN
Inventors: 藤原祐辅; 静井章朗
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2022-03-07
Filing date: 2023-03-06
Publication date: 2023-09-08

Abstract

The present invention relates to chemically strengthened glass and a method for producing chemically strengthened glass. Chemically strengthened glass has a depth (μm) from the surface on the horizontal axis and K in mole percent based on oxide on the vertical axis ₂ K of O concentration (%) ₂ In the O concentration distribution, the slope (%/μm) in the range of 1 μm to 3 μm in depth and the slope (%/μm) in the range of 5 μm to 10 μm in depth are within a specific range. A method of manufacturing chemically strengthened glass, comprising, in order: (1) By usingAt least one ion exchange of the lithium-containing glass with the inorganic salt composition containing potassium; (2) The lithium-containing glass and the LiNO-containing glass are mixed ₃ And NaNO ₃ And NaNO ₃ Relative to LiNO ₃ The inorganic salt composition with the mass ratio in a specific range is subjected to reverse ion exchange under specific conditions; and (3) ion-exchanging the lithium-containing glass at least once with an inorganic salt composition containing potassium.

Description

Chemically strengthened glass and method for producing same

Technical Field

The present invention relates to chemically strengthened glass and a method for producing the same.

Background

Conventionally, for a cover glass for a display of various information terminal apparatuses, excellent strength has been required, and a chemically strengthened glass has been used because of its thinness and strong crack resistance. The chemically strengthened glass is a glass in which a compressive stress layer is formed on a surface portion of the glass by an ion exchange treatment in which the glass is brought into contact with a molten salt composition such as sodium nitrate or potassium nitrate.

In the ion exchange treatment, ion exchange occurs between alkali metal ions contained in the glass and alkali metal ions having different ionic radii contained in the molten salt composition, thereby forming a compressive stress layer at the surface portion of the glass. The strength of chemically strengthened glass depends on the stress distribution represented by compressive stress (hereinafter, also simply referred to as CS) having the depth from the surface of the glass as a variable.

The cover glass of a mobile terminal or the like may be broken by deformation when it falls from a high place or the like. In order to prevent such breakage, that is, breakage due to bending, it is effective to increase the compressive stress of the glass surface. Therefore, recently, high surface compressive stress of 700MPa or more is more often formed.

In addition, when the terminal is dropped from a high place onto asphalt or sand, the cover glass of the mobile terminal may be broken by collision with the protrusion. In order to prevent such breakage, that is, breakage caused by impact, it is effective to increase the depth of the compressive stress layer and form the compressive stress layer to a deeper portion of the glass to improve the strength.

On the other hand, when the compressive stress layer is formed on the surface portion of the glass article, a tensile stress (hereinafter, also simply referred to as CT) corresponding to the total amount of compressive stress on the surface must be generated in the center portion (hereinafter, also simply referred to as center portion) of the glass article in the thickness of the glass article. When the CT value is too large, the glass article is broken and broken vigorously, and the fragments scatter. When the CT value exceeds the threshold (hereinafter, also simply referred to as CT limit), the glass is self-destructed and the breaking number at the time of damage increases explosively. The CT limit is a value inherent to the glass composition.

Therefore, it is required for chemically strengthened glass to increase the compressive stress of the surface, further increase the strength so as to form the compressive stress layer to a deeper portion, and on the other hand, design the total amount of compressive stress of the surface layer so as not to exceed the CT limit.

On the other hand, in the process of producing chemically strengthened glass, glass that does not meet the desired specifications, for example, glass having defects below the standard level or an inappropriate stress distribution may be generated. Conventionally, as a method for reprocessing chemically strengthened glass having the above-described defects or improper stress distribution after ion exchange, a method of forming a compressive stress layer by removing the compressive stress layer of chemically strengthened glass by ion exchange (hereinafter, also simply referred to as counter ion exchange) or polishing or the like and then ion-exchanging again (hereinafter, also simply referred to as re-ion exchange) has been used.

For example, patent document 1 discloses a method for producing chemically strengthened glass, which comprises the following steps in order: step (1): a glass plate preparation step of preparing a glass plate having a compressive stress layer on a surface layer; step (2): a first ion exchange step of contacting the glass plate with an inorganic salt composition to perform at least one group of ion exchange to reduce the compressive stress of the compressive stress layer; and a step (3): and a second ion exchange step of contacting the glass plate with an inorganic salt composition to perform at least one ion exchange to increase the compressive stress of the compressive stress layer of the surface layer.

Patent document 2 discloses a method comprising the steps of: a step of producing a glass article having undergone the ion exchange by subjecting the glass article having undergone the ion exchange to a counter ion exchange in a counter ion exchange bath containing a lithium salt; and a step of re-ion-exchanging the glass article subjected to the counter ion exchange in a re-ion exchange bath, thereby forming a re-ion exchanged glass article.

Patent document 3 discloses a method comprising a step of subjecting an ion-exchanged glass article to a counter ion exchange with a counter ion exchange medium containing a lithium salt and a polyvalent metal salt capable of undergoing non-ion exchange to produce a counter ion-exchanged glass article.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2019-194143

Patent document 2: japanese patent application laid-open No. 2020-506151

Patent document 3: japanese patent application laid-open No. 2021-525208

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a chemically strengthened glass that exhibits excellent strength, and a method for producing the same.

Means for solving the problems

The inventors have found that a lithium-containing glass having a compressive stress layer formed on the surface layer by chemical strengthening including at least ion exchange with K ions is subjected to a counter ion exchange under specific conditions, and then the glass surface is removed and ion-exchanged again, whereby a glass having a specific K can be obtained ₂ The present invention has been accomplished in view of the above problems.

The present invention relates to a chemically strengthened glass, wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents K in mole percent based on oxide ₂ K of O concentration (%) ₂ K in the range of 1 μm to 3 μm in depth in the O concentration distribution ₂ The slope (%/μm) of the O concentration is-1.9 or more, and K is in the range of 5 μm to 10 μm in depth ₂ The slope (%/μm) of the O concentration is-0.001 or less.

The present invention also relates to a method for producing chemically strengthened glass, comprising the following steps (1) to (3) in this order.

(1) At least one ion exchange of the lithium-containing glass with a first inorganic salt composition comprising potassium;

(2) Bringing the lithium-containing glass into contact with a lithium-containing material containing LiNO ₃ And NaNO ₃ And NaNO ₃ Relative to LiNO ₃ The second inorganic salt composition with the mass ratio of 0.25-3.0 is contacted for more than 5 hours at the temperature of more than 425 ℃ to carry out reverse ion exchange;

(3) At least one ion exchange of the lithium-containing glass with a third inorganic salt composition comprising potassium is performed.

The present invention also relates to a chemically strengthened glass, wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents K in mole percent based on oxide ₂ K of O concentration (%) ₂ K in the range of 1 μm to 3 μm in depth in the O concentration distribution ₂ The slope (%/μm) of the O concentration is-1.9 to 0.0, and K is in the range of 5 μm to 10 μm in depth ₂ The slope (%/μm) of the O concentration is-0.001 or less.

Effects of the invention

The chemically strengthened glass of the present invention has a specific K ₂ The O concentration distribution is such that a large amount of K ions are introduced into the surface layer, thereby having excellent surface strength and improving ball drop strength and scratch resistance.

In addition, according to the method for producing chemically strengthened glass of the present invention, a lithium-containing glass having a compressive stress layer formed on the surface layer by chemical strengthening including ion exchange with at least K ions is subjected to reverse ion exchange under specific conditions, and then the glass surface is removed and ion-exchanged again, whereby a glass having a specific K can be obtained ₂ Chemically strengthened glass having an O concentration distribution and exhibiting excellent strength.

Drawings

Fig. 1 (a) and 1 (b) show stress distribution of chemically strengthened glass according to an embodiment of the present invention. Fig. 1 (a) shows stress distribution in the surface layer portion. Fig. 1 (b) shows stress distribution of the deep portion.

FIGS. 2 (a) and 2 (b) show Na of chemically strengthened glass by EPMA ₂ Results of measurement of O concentration (example 1). FIGS. 2 (c) and 2 (d) show K for chemically strengthened glass using EPMA ₂ Results of measurement of O concentration (example 1). In fig. 2 (a) to 2 (d), the horizontal axis represents the depth (μm) from the glass surface, and the vertical axis represents the concentration (%) in terms of mole percent based on oxide.

FIGS. 3 (a) and 3 (b) show Na of chemically strengthened glass by EPMA ₂ Results of measurement of O concentration (example 2). FIGS. 3 (c) and 3 (d) show K for chemically strengthened glass using EPMA ₂ Results of measurement of O concentration (example 2). In fig. 3 (a) to 3 (d), the horizontal axis represents the depth (μm) from the glass surface, and the vertical axis represents the concentration (%) in terms of mole percent based on oxide.

FIGS. 4 (a) and 4 (b) show Na of chemically strengthened glass by EPMA ₂ Results of measurement of O concentration (example 5). FIGS. 4 (c) and 4 (d) show K for chemically strengthened glass using EPMA ₂ Results of measurement of O concentration (example 5). In fig. 4 (a) to 4 (d), the horizontal axis represents the depth (μm) from the glass surface, and the vertical axis represents the concentration (%) in terms of mole percent based on oxide.

Detailed Description

The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified and implemented arbitrarily within a scope not departing from the gist of the present invention.

In the present specification, "to" representing a numerical range is used in a meaning including numerical values described before and after the numerical value as a lower limit value and an upper limit value. In this specification, the composition (content of each component) of the glass will be described in terms of mole percent based on the oxide unless otherwise specified.

Hereinafter, "chemically strengthened glass" refers to glass after being subjected to chemical strengthening treatment, and "chemically strengthened glass" refers to glass before being subjected to chemical strengthening treatment.

In the present specification, unless otherwise specified, the glass composition is expressed in mol% based on oxides, and the mol% is abbreviated as "%".

In the present specification, "substantially free" means that the impurity level contained in the raw material or the like is not higher than that, that is, the impurity is not intentionally contained. Specifically, for example, less than 0.1%.

In the present specification, "K ₂ O concentration distribution "or" Na ₂ O concentration distribution "meansThe horizontal axis represents depth (. Mu.m) from the glass surface and the vertical axis represents K in mole percent based on oxide ₂ O concentration (%) or Na ₂ Distribution represented by O concentration.

In the present specification, K at depth x (μm) ₂ O concentration or Na ₂ The O concentration was measured by EPMA (electron beam micro analyzer) to determine the concentration of the cross section in the plate thickness direction. The EPMA is measured, for example, as follows.

First, a glass sample is embedded with an epoxy resin, and mechanically polished in a direction perpendicular to a first main surface and a second main surface opposite to the first main surface, thereby producing a cross-section sample. The polished cross section was C-coated and measured by EPMA (JXA-8500F, manufactured by JEOL Co.). The acceleration voltage was set at 15kV, the probe current was set at 30nA, the accumulation time was set at 1000 msec/point, and K was obtained at 1 μm intervals ₂ O or Na ₂ Line distribution of X-ray intensity of O. Regarding the obtained K ₂ O concentration distribution or Na ₂ The O concentration distribution was calculated by scaling the total plate thickness count to mol% with the average count of the plate thickness center portion (0.5×t) + -25 μm (the plate thickness is set to t μm) as the main body composition.

In the present specification, the depth of the potassium ion diffusion layer means, relative to K ₂ Average K of the center portion (0.5×t) + -25 μm of the plate thickness in the O concentration distribution ₂ The O concentration (%) and the variance value σ thereof are measured from the outermost surface side by using K ₂ The depth (μm) at which the O concentration falls within the range of +2σ or less is used as the potassium ion diffusion layer depth.

In the present specification, the term "stress distribution" means a distribution of stress by taking the depth from the glass surface as a variable. In the stress distribution, the tensile stress is expressed as negative compressive stress.

The "Compressive Stress (CS)" can be determined by flaking a cross section of glass and analyzing the flaked sample using a birefringence imaging system. The birefringent imaging system birefringent strain gauge is a device for measuring the magnitude of retardation due to strain using a polarized light microscope, a liquid crystal compensator, or the like, and is manufactured by CRi corporation, for example, as a birefringent imaging system Abrio-IM.

In addition, measurement may be performed by utilizing scattered photoelasticity. In this method, CS can be measured by entering light from the surface of glass and analyzing the polarized light of scattered light thereof. As a stress measuring instrument using scattered light photoelasticity, there is, for example, a scattered light photoelastic stress meter SLP-2000 manufactured by the manufacture of a folding body.

In the present specification, "depth of compressive stress (DOC)" means depth of compressive stress (μm) measured by SLP-2000, and is the depth at which compressive stress is zero. Hereinafter, the surface compressive stress may be referred to as CS ₀ The compressive stress at a depth of 50 μm from the surface was denoted CS ₅₀ . The "internal tensile stress (CT)" means a tensile stress at a depth of 1/2 of the plate thickness t.

In the present specification, "4PB strength" (four-point bending strength) was measured by the following method.

A four-point bending test was conducted using a 50mm by 50mm test piece under conditions that the distance between the outer fulcrums of the support was 30mm, the distance between the inner fulcrums was 10mm, and the crosshead speed was 5.0 mm/min, and the breaking stress (unit: MPa) thus obtained was taken as four-point bending strength. The number of test pieces is set to 10, for example.

< method of measuring stress >)

In recent years, two-step chemically strengthened glass has been mainly used for a protective glass for a smart phone or the like, in which lithium ions and sodium ions (Li-Na exchange) are exchanged inside the glass, and then sodium ions and potassium ions (Na-K exchange) are exchanged inside the glass at a surface layer portion of the glass.

In order to obtain the stress distribution of such a two-step chemically strengthened glass nondestructively, for example, a scattered light photoelastic strain gauge (Scattered Light Photoelastic Stress Meter, hereinafter also simply referred to as SLP), a glass surface strain gauge (Film Stress Measurment, hereinafter also simply referred to as FSM), or the like may be used in combination.

By using a scattered light photoelastic stress meter (SLP), the compressive stress due to Li-Na exchange can be measured in a glass having a thickness of several tens μm or more from the glass surface layer. On the other hand, by using a glass surface stress meter (FSM), the compressive stress due to na—k exchange can be measured in a glass surface layer portion of several tens μm or less from the glass surface (for example, international publication nos. 2018/056121 and 2017/115811). Therefore, as stress distribution of the glass surface layer and the inside of the two-step chemically strengthened glass, stress distribution obtained by synthesizing information of SLP and FSM may be used.

In the present invention, a stress distribution measured by a scattered light photoelastic stress meter (SLP) is mainly used. In the present specification, the terms stress CS, tensile stress CT, and depth of layer of compressive stress DOL refer to values in SLP stress distribution.

The scattered light photoelastic strain gauge is a strain measurement device provided with: a polarized light phase difference variable member that changes a polarized light phase difference of a laser beam by one wavelength or more with respect to a wavelength of the laser beam; an imaging element that acquires a plurality of images by imaging scattered light emitted by making the laser beam, the polarization phase difference of which has been changed, enter the tempered glass at a predetermined time interval; and a calculation unit that measures a periodic luminance change of the scattered light using the plurality of images, calculates a phase change of the luminance change, and calculates a stress distribution in a depth direction from the surface of the tempered glass based on the phase change.

As a method for measuring stress distribution using a scattered light photoelastic stress meter, a method described in international publication No. 2018/056121 is exemplified. Examples of the scattered light photoelastic strain gauge include SLP-1000 and SLP-2000 manufactured by the manufacture of a folding original. When the software slpiv_up3 (ver.2019.01.10.001) is used in combination with these scattered light photoelastic strain gauges, high-precision strain measurement can be performed.

< chemically strengthened glass >)

The chemically strengthened glass of the present embodiment (hereinafter, also referred to as "the present chemically strengthened glass") is characterized in that the horizontal axis represents the depth (μm) from the surface and the vertical axis represents K in terms of mole percent based on the oxide ₂ K of O concentration (%) ₂ In the O concentration distribution, the slope (%/μm) in the range of 1 μm to 3 μm in depth is-1.9 or more, and the slope (%/μm) in the range of 5 μm to 10 μm in depth is-0.001 or less.

In the present specification, K ₂ The slope in the O concentration profile refers to K ₂ K in O concentration profile ₂ Slope of O concentration.

By at K ₂ The gradient (%/μm) in the range of 1 μm to 3 μm in depth is-1.9 or more and the gradient (%/μm) in the range of 5 μm to 10 μm in depth is-0.001 or less in the O concentration distribution, so that the K ion concentration in the surface layer portion can be increased and the strength can be improved. Examples of the strength include: flexural strength, surface hardness, ball drop strength and mar resistance.

By at K ₂ The gradient (%/μm) in the range of 1 μm to 3 μm in depth in the O concentration distribution is-1.9 or more, and the K ion concentration in the surface layer portion can be increased, and the strength can be improved. At K ₂ In the O concentration distribution, the slope (%/μm) in the range of 1 μm to 3 μm in depth is preferably-1.80 or more, more preferably-1.70 or more, still more preferably-1.65 or more, and particularly preferably-1.60 or more.

K ₂ The slope (%/μm) in the range of 1 to 3 μm in depth in the O concentration distribution is preferably-1.000 or less, more preferably-1.10 or less, still more preferably-1.20 or less, and particularly preferably-1.30 or less. By at K ₂ The gradient (%/μm) in the range of 1 to 3 μm in depth in the O concentration distribution is-1.000 or less, and thus excessive stress that does not contribute to the strength can be reduced. K (K) ₂ The slope (%/μm) in the range of 1 to 3 μm in depth in the O concentration distribution has a value of 0.0 or less, and thus the surface layer portion functions.

By at K ₂ The slope (%/μm) of the O concentration distribution in the range of 5 μm to 10 μm in depth is-0.001 or less, and potassium ions in the surface layer of the glass can be diffused into the microcrack region of the surface, and the bending strength due to the surface compressive stress can be improved. K (K) ₂ The slope (%/μm) in the range of 5 μm to 10 μm in depth in the O concentration distribution is preferably-0.010 or less,more preferably-0.020 or less, still more preferably-0.030 or less, particularly preferably-0.040 or less.

K ₂ The slope (%/μm) of the O concentration distribution in the range of 5 μm to 10 μm in depth is preferably-0.200 or more, more preferably-0.180 or more, still more preferably-0.160 or more, and particularly preferably-0.140 or more. At K ₂ In the O concentration distribution, the slope (%/μm) in the range of 5 μm to 10 μm in depth is set to-0.200 or more, so that the potassium ion amount in the surface layer of the glass is not excessive, and the ion exchange inhibition by re-strengthening is suppressed, thereby improving the stress in the deep layer.

The chemically strengthened glass is preferably: the horizontal axis represents depth (. Mu.m) from the surface and the vertical axis represents Na in mole percent based on oxide ₂ Na of O concentration (%) ₂ In the O concentration distribution, the gradient (%/μm) in the range of 10 μm to 50 μm in depth is-0.001 or less, and the gradient (%/μm) in the range of 50 μm to 90 μm in depth is-0.012 or more.

By the method of Na ₂ The gradient (%/μm) in the range of 10 μm to 50 μm in depth in the O concentration distribution is-0.001 or less, and the gradient (%/μm) in the range of 50 μm to 90 μm in depth is-0.012 or more, so that the Na ion concentration in the surface layer portion can be reduced as compared with the conventional chemically strengthened glass, and the occurrence of excessive stress that does not contribute to the strength can be further reduced.

In the present specification, na ₂ The slope in the O concentration profile refers to Na ₂ Na in O concentration distribution ₂ Slope of O concentration.

Na ₂ The slope (%/μm) of the O concentration distribution in the range of 10 μm to 50 μm in depth is preferably-0.001 or less, more preferably-0.002 or less, still more preferably-0.003 or less, and particularly preferably-0.004 or less. By the method of Na ₂ The slope (%/μm) of the O concentration distribution in the range of 10 μm to 50 μm is-0.001 or less, and the Na ion concentration in the surface layer portion can be reduced as compared with the conventional chemically strengthened glass, and the occurrence of excessive stress which does not contribute to the strength can be further reduced.

Na ₂ O concentrationThe slope (%/μm) in the range of 10 μm to 50 μm in depth in the distribution is preferably-0.020 or more, more preferably-0.018 or more, still more preferably-0.016 or more, particularly preferably-0.014 or more. By the method of Na ₂ The slope (%/μm) of the O concentration distribution in the range of 10 μm to 50 μm is-0.020 or more, and the Na ion concentration in the surface layer portion can be reduced as compared with the conventional chemically strengthened glass, and the occurrence of excessive stress not contributing to the strength can be further reduced.

Na ₂ The slope (%/μm) in the range of 50 μm to 90 μm in depth in the O concentration distribution is preferably-0.012 or more, more preferably-0.011 or more, still more preferably-0.010 or more, and particularly preferably-0.009 or more. By the method of Na ₂ The slope (%/μm) of the O concentration distribution in the range of 50 μm to 90 μm is-0.012 or more, and the Na ion concentration in the deep layer can be increased, and a stress contributing to the drop strength can be generated.

Na ₂ The slope (%/μm) of the O concentration distribution in the range of 50 μm to 90 μm is preferably-0.002 or less, more preferably-0.003 or less, still more preferably-0.004 or less, and particularly preferably-0.005 or less. By the method of Na ₂ The slope (%/μm) of the O concentration distribution in the range of 50 μm to 90 μm is-0.002 or less, and the Na ion concentration in the deep portion can be increased, and a stress contributing to the drop strength can be generated.

The chemically strengthened glass of the present embodiment is preferably a glass having a composition of K ₂ The absolute value of the value obtained by dividing the slope (%/μm) in the range of 5 μm to 10 μm by the slope (%/μm) in the range of 1 μm to 3 μm in the O concentration distribution is 0.005 to 0.10. By the absolute value being within the above range, potassium ions in the surface layer of the glass can be diffused into the microcrack region of the surface. The absolute value is more preferably 0.010 or more, still more preferably 0.015 or more, and particularly preferably 0.020 or more. The absolute value is more preferably 0.095 or less, still more preferably 0.090 or less, still more preferably 0.085 or less, and particularly preferably 0.080 or less.

The chemically strengthened glass of the present embodiment is preferably made of Na ₂ In the O concentration distributionThe absolute value of the value obtained by dividing the slope (%/μm) in the range of 50 μm to 90 μm by the slope (%/μm) in the range of 10 μm to 50 μm is 0.50 to 4.0. The absolute value is more preferably 0.60 or more, still more preferably 0.70 or more, still more preferably 0.80 or more, and particularly preferably 0.90 or more. The absolute value is more preferably 3.9 or less, still more preferably 3.8 or less, still more preferably 3.7 or less, and particularly preferably 3.6 or less.

The chemically strengthened glass of the present embodiment is preferably a glass having a composition of K ₂ K in the range of 15 μm to 25 μm in depth in the O concentration distribution ₂ O concentration (%) and K in the center portion ₂ The absolute value of the difference in O concentration (%) is 0.20% or less, more preferably 0.16% or less, still more preferably 0.12% or less, and particularly preferably 0.10% or less. Through K in the range of 15 μm to 25 μm in depth ₂ O concentration and K of the center portion ₂ The absolute value of the difference in O concentration is 0.20% or less, whereby the tensile stress balanced with the compressive stress can be reduced, and the development of damage due to the tensile stress can be suppressed. Here, K is in the range of 15 μm to 25 μm in depth ₂ The O concentration is K in the range of 15 μm to 25 μm in depth ₂ And (3) averaging the O concentration. The lower limit of the absolute value of the difference is usually preferably 0.001% or more, more preferably 0.005% or more.

The chemically strengthened glass of the present embodiment preferably has a diffusion layer depth of potassium ions of 5 μm or more, more preferably 7 μm or more. In addition, it is usually preferably 20 μm or less, more preferably 18 μm or less, and still more preferably 16 μm or less. The diffusion layer depth of potassium ions is 5 μm or more, whereby the K ion concentration in the surface layer portion can be increased, and the strength can be improved.

Fig. 1 (a) and 1 (b) show stress distribution of an embodiment of the present chemically strengthened glass. Fig. 1 (a) shows stress distribution in the surface layer portion. Fig. 1 (b) shows stress distribution of the deep portion. In fig. 1 (a) and 1 (b), a solid line represents an example, and a broken line represents a comparative example. As shown in fig. 1 (a), the K ion-dependent compressive stress of the surface layer portion of the present chemically strengthened glass was higher than that of the comparative example, and as shown in fig. 1 (b), the compressive stress of the deep layer portion of the present chemically strengthened glass was equal to that of the DOC, and thus the present chemically strengthened glass exhibited excellent strength. The stress distribution of the surface layer portion was the depth of layer (μm) of compressive stress measured by FSM, and the stress distribution of the deep layer portion was the depth of layer (μm) of compressive stress measured by SLP-2000.

The surface Compressive Stress (CS) of the chemically strengthened glass ₀ ) When 500MPa or more, it is not likely to crack due to deformation such as deflection, and is preferable. CS (circuit switching) ₀ More preferably 600MPa or more, and still more preferably 700MPa or more. CS (circuit switching) ₀ The larger the strength is, the higher the CS is ₀ If too large, severe crushing may occur in the event of breakage, and thus CS ₀ Preferably 1200MPa or less, more preferably 1000MPa or less.

The chemically strengthened glass has a Compressive Stress (CS) at a depth of 50 μm from the surface ₅₀ ) When the pressure is 50MPa or more, breakage of the chemically strengthened glass can be easily prevented when a mobile terminal or the like having the chemically strengthened glass as a cover glass is dropped from a high place, and is preferable. CS (circuit switching) ₅₀ More preferably 60MPa or more, and still more preferably 70MPa or more. CS (circuit switching) ₅₀ The larger the strength is, the higher the CS is ₅₀ If too large, severe crushing may occur in the event of breakage, and thus CS ₅₀ Preferably 180MPa or less, more preferably 160MPa or less.

Compressive stress CS at depth of 90 μm from surface of the chemically strengthened glass ₉₀ When the pressure is 30MPa or more, breakage of the chemically strengthened glass can be prevented when the chemically strengthened glass is dropped from a high place to a rough sand or the like in a mobile terminal or the like having the chemically strengthened glass as a cover glass, and is preferable. CS (circuit switching) ₉₀ More preferably 40MPa or more, and still more preferably 50MPa or more. CS (circuit switching) ₉₀ The larger the strength is, the higher the CS is ₉₀ If too large, severe crushing may occur in the event of breakage, and thus CS ₉₀ Preferably 170MPa or less, more preferably 150MPa or less.

When the DOC of the chemically strengthened glass is 80 μm or more, the DOC is preferably not broken easily even if damage occurs on the surface. The DOC is more preferably 90 μm or more, still more preferably 100 μm or more, and particularly preferably 110 μm or more. The larger the DOC, the more difficult it is to break even if damage occurs, but in chemically strengthened glass, a tensile stress is generated inside in accordance with a compressive stress formed in the vicinity of the surface, and therefore DOC cannot be extremely increased. In the case of the thickness t, DOC is preferably t/4 or less, more preferably t/5 or less. In order to shorten the time required for chemical strengthening, DOC is preferably 160 μm or less, more preferably 150 μm or less.

The CS, DOC of the chemically strengthened glass can be appropriately adjusted by adjusting the conditions of chemical strengthening, the composition, thickness, etc. of the glass.

The chemically strengthened glass exhibits excellent strength by introducing a large amount of K ions into the surface layer of the glass. The four-point bending strength of the chemically strengthened glass is preferably 480MPa or more, more preferably 500MPa or more, still more preferably 520MPa or more, and most preferably 540MPa or more. The four-point bending strength is 480MPa or more, whereby the strength reliability can be improved.

The chemically strengthened glass is typically a plate-shaped glass article, and may be either a flat plate or a curved surface. In addition, there may be portions of different thickness.

The thickness (t) of the chemically strengthened glass in the form of a plate 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, 700 μm or less in steps. In order to obtain sufficient strength by the chemical strengthening treatment, the thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and still more preferably 500 μm or more.

Use of

The chemically strengthened glass is also useful as a cover glass for electronic devices such as mobile devices including mobile phones and smart phones. It is also useful for a protective glass for electronic devices such as televisions, personal computers, touch panels, etc., an elevator wall surface, and a wall surface (full screen display) of a building such as a house or a building, etc., which are not intended for portability. Further, the present invention is useful as a building material such as a window glass, a cover glass for an interior such as a desk top, an automobile, an airplane, or the like, or a case having a curved shape.

Composition < >

In the present specification, the "basic composition of chemically strengthened glass" refers to a glass composition of chemically strengthened glass, and the glass composition of a portion of chemically strengthened glass deeper than the depth of the compressive stress layer is substantially the same as the basic composition of chemically strengthened glass, except for the case of performing an extreme ion exchange treatment.

The basic composition of the chemically strengthened glass of the present embodiment preferably contains, in mole% based on oxides:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ And (d) sum

5 to 18 percent of Li ₂ O。

The basic composition of the chemically strengthened glass of the present embodiment more preferably contains, in mole% based on oxides:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ 、

5 to 18 percent of Li ₂ O、

0 to 15 percent of Na ₂ O、

0 to 5 percent of K ₂ O、

0 to 20 percent of MgO,

0 to 20 percent of CaO,

0 to 20 percent of SrO,

0 to 20 percent of BaO,

0 to 10 percent of ZnO,

0 to 1 percent of TiO ₂ 、

ZrO 0-8% ₂ And (d) sum

0 to 5% of Y ₂ O ₃ 。

Hereinafter, the basic composition of a preferred glass will be described.

In the chemically strengthened glass of the present embodiment, siO ₂ Is a component forming a network structure of glass. In addition, siO ₂ Is a component for improving chemical durability. SiO (SiO) ₂ The content of (C) is preferably 52% or more, more preferably The content is selected to be 56% or more, more preferably 60% or more, and particularly preferably 64% or more. On the other hand, in order to improve the meltability, siO ₂ The content of (2) is preferably 75% or less, more preferably 73% or less, still more preferably 71% or less, particularly preferably 69% or less.

Al ₂ O ₃ Is a component that increases the surface compressive stress caused by chemical strengthening, and is indispensable. Al (Al) ₂ O ₃ The content of (2) is preferably 8% or more, more preferably 10% or more, still more preferably 11% or more, particularly preferably 12% or more. On the other hand, in order to prevent the devitrification temperature of the glass from becoming too high, al ₂ O ₃ The content of (c) is preferably 20% or less, more preferably 18% or less, further preferably 17% or less, 16% or less, and most preferably 15% or less in this order.

Li ₂ O is a component that forms surface compressive stress by ion exchange. Li (Li) ₂ The content of O is preferably 5% or more, more preferably 7% or more, further preferably 9% or more in steps below, and particularly preferably 11% or more. On the other hand, in order to stabilize the glass, li ₂ The content of O is preferably 18% or less, more preferably 17% or less, further preferably 16% or less, and most preferably 15% or less.

MgO is a component for stabilizing glass and also a component for improving mechanical strength and chemical resistance, and therefore, in Al ₂ O ₃ When the content is small, mgO is preferably contained. The MgO content is preferably 1% or more, more preferably 2% or more, still more preferably 3% or more, and particularly preferably 4% or more. On the other hand, when MgO is excessively added, the viscosity of the glass decreases, and devitrification or phase separation is likely to occur. The MgO content is preferably 20% or less, more preferably 19% or less, further preferably 18% or less, and particularly preferably 17% or less.

CaO, srO, baO and ZnO are both components for improving the meltability of the glass, and may be contained.

CaO is a component for improving the meltability of the glass, is a component for improving the breakage of the chemically strengthened glass, and may be contained. When CaO is contained, the content of CaO is preferably 0.5% or more, more preferably 1% or more, still more preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. On the other hand, if the CaO content exceeds 20%, the ion exchange performance is significantly reduced, and therefore the CaO content is preferably 20% or less. The CaO content is more preferably 16% or less, and further preferably 12% or less, 10% or less, and 8% or less in steps as follows.

SrO is a component for improving the meltability of glass, is a component for improving the breakage of chemically strengthened glass, and may be contained. When SrO is contained, the content of SrO is preferably 0.5% or more, more preferably 1% or more, still more preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. On the other hand, when the content of SrO exceeds 20%, the ion exchange performance is significantly reduced, and therefore the content of SrO is preferably 20% or less. The content of SrO is more preferably 16% or less, and further preferably 12% or less, 10% or less, and 8% or less in steps as follows.

BaO is a component for improving the meltability of glass, is a component for improving the breakage of chemically strengthened glass, and may be contained. When BaO is contained, 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 5% or more. On the other hand, when the content of BaO exceeds 20%, the ion exchange performance is significantly reduced, and therefore the content of BaO is preferably 20% or less. The content of BaO is more preferably 16% or less, and further preferably 12% or less, 10% or less, and 8% or less in steps as follows.

ZnO is a component for improving the meltability of glass, and may be contained. When ZnO is contained, the content of ZnO is preferably 0.25% or more, more preferably 0.5% or more. On the other hand, when the content of ZnO exceeds 10%, the weather resistance of the glass is significantly reduced. The ZnO content is preferably 10% or less, more preferably 8% or less, 6% or less, 4% or less, 2% or less, 1% or less in steps as follows.

Na ₂ O is a component that improves the meltability of the glass. Na (Na) ₂ O is not essential, but contains Na ₂ Na in the case of O ₂ The content of O is preferably 1% or more, more preferablyPreferably 2% or more, and particularly preferably 4% or more. Na (Na) ₂ When O is excessive, the chemical strengthening property is lowered, and therefore Na ₂ The content of O is preferably 15% or less, more preferably 12% or less, particularly preferably 10% or less, and most preferably 8% or less.

K ₂ O and Na ₂ O is also a component for lowering the melting temperature of the glass, and may contain K ₂ O. In the presence of K ₂ In the case of O K ₂ The content of O is preferably 0.5% or more, more preferably 0.8% or more, further preferably 1% or more, still more preferably 1.2% or more, and particularly preferably 1.5% or more. K (K) ₂ When O is too much, the chemical strengthening property is reduced or the chemical durability is reduced, and therefore, it is preferably 5% or less, more preferably 4.8% or less, further preferably 4.6% or less, particularly preferably 4.2% or less, and most preferably 4.0% or less.

To improve the meltability of the glass raw material, na ₂ O and K ₂ Total content of O Na ₂ O+K ₂ O is preferably 3% or more, more preferably 5% or more. In addition, K ₂ O content relative to Li ₂ O、Na ₂ O and K ₂ Total of O content (hereinafter, R ₂ Ratio K of O) ₂ O/R ₂ When O is 0.2 or less, chemical strengthening properties can be improved, and chemical durability can be improved, so that it is preferable. K (K) ₂ O/R ₂ O is more preferably 0.15 or less, and still more preferably 0.10 or less. R is as follows ₂ The O content is preferably 10% or more, more preferably 12% or more, and even more preferably 15% or more. In addition, R ₂ O is preferably 20% or less, more preferably 18% or less.

ZrO ₂ Is a component for improving mechanical strength and chemical durability, and preferably contains ZrO for significantly improving CS ₂ 。ZrO ₂ The content of (2) is preferably 0.5% or more, more preferably 0.7% or more, still more preferably 1.0% or more, particularly preferably 1.2% or more, and most preferably 1.5% or more. On the other hand, in order to suppress devitrification at the time of melting, zrO ₂ Preferably 8% or less, more preferably 7.5% or less, still more preferably 7% or less, particularly preferably 6% or less。ZrO ₂ When the content of (b) is too large, the viscosity decreases due to an increase in the devitrification temperature. In order to suppress deterioration of formability due to reduction of viscosity, zrO in the case where the forming viscosity is low ₂ The content of (2) is preferably 5% or less, more preferably 4.5% or less, and still more preferably 3.5% or less.

ZrO for improving chemical durability ₂ /R ₂ O is preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.04 or more, particularly preferably 0.08 or more, and most preferably 0.1 or more. ZrO (ZrO) ₂ /R ₂ O is preferably 0.2 or less, more preferably 0.18 or less, further preferably 0.16 or less, and particularly preferably 0.14 or less.

TiO ₂ Is not essential, but contains TiO ₂ In the case of TiO ₂ The content of (2) is preferably 0.05% or more, more preferably 0.1% or more. On the other hand, in order to suppress devitrification at the time of melting, tiO ₂ The content of (2) is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.3% or less.

SnO ₂ Not essential, but in the presence of SnO ₂ Is SnO of (C) ₂ The content of (2) is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, snO is used to suppress devitrification during melting ₂ The content of (2) is preferably 4% or less, more preferably 3.5% or less, still more preferably 3% or less, and particularly preferably 2.5% or less.

Y ₂ O ₃ Is a component having an effect of making fragments less likely to scatter when the chemically strengthened glass is broken, and may contain Y ₂ O ₃ 。Y ₂ O ₃ The content of (2) is preferably 0.3% or more, more preferably 0.5% or more, still more preferably 0.7% or more, and particularly preferably 1.0% or more. On the other hand, in order to suppress devitrification at the time of melting, Y ₂ O ₃ The content of (2) is preferably 5% or less, more preferably 4% or less.

B ₂ O ₃ To improve the edge defect resistance of chemically strengthened glass or chemically strengthened glass and to improve the toughness of the glassThe meltable component may contain B ₂ O ₃ . In the presence of B ₂ O ₃ In the case of (B), in order to improve the meltability ₂ O ₃ The content of (2) is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more. On the other hand, B ₂ O ₃ If the content of (B) is too large, striae tend to occur during melting or phase separation tends to occur, and the quality of the chemically strengthened glass tends to be low, so that B ₂ O ₃ The content of (2) is preferably 10% or less. B (B) ₂ O ₃ The content of (2) is more preferably 8% or less, still more preferably 6% or less, and particularly preferably 4% or less.

La ₂ O ₃ 、Nb ₂ O ₅ And Ta ₂ O ₅ All of the components are components that cause fragments to be less likely to scatter when the chemically strengthened glass is broken, and these components may be contained in order to increase the refractive index. In the case of containing them, la ₂ O ₃ 、Nb ₂ O ₅ And Ta ₂ O ₅ The sum of the contents (hereinafter, la ₂ O ₃ +Nb ₂ O ₅ +Ta ₂ O ₅ ) Preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. In addition, in order to make the glass not easily devitrified at the time of melting, la ₂ O ₃ +Nb ₂ O ₅ +Ta ₂ O ₅ Preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less.

In addition, ceO may be contained ₂ 。CeO ₂ Coloring is sometimes inhibited by oxidizing the glass. In the presence of CeO ₂ In the case of CeO ₂ The content of (2) is preferably 0.03% or more, more preferably 0.05% or more, and still more preferably 0.07% or more. CeO for improving transparency ₂ The content of (2) is preferably 1.5% or less, more preferably 1.0% or less.

When the chemically strengthened glass is used for coloring, a coloring component may be added in a range that does not inhibit the achievement of desired chemical strengthening characteristics. Examples of the coloring component include: co (Co) ₃ O ₄ 、MnO ₂ 、Fe ₂ O ₃ 、NiO、CuO、Cr ₂ O ₃ 、V ₂ O ₅ 、Bi ₂ O ₃ 、SeO ₂ 、Er ₂ O ₃ 、Nd ₂ O ₃ 。

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

To improve the weatherability to ultraviolet irradiation, hfO may be added ₂ 、Nb ₂ O ₅ 、Ti ₂ O ₃ . In the case of addition for the purpose of improving weather resistance to ultraviolet light irradiation, hfO is added for the purpose of suppressing influence on other characteristics ₂ 、Nb ₂ O ₅ And Ti is ₂ O ₃ The total content of (2) is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.1% or less.

In addition, SO may be contained appropriately as a fining agent or the like at the time of glass melting ₃ Chloride, fluoride. Since the total content of the components functioning as the clarifying agent affects the strengthening property when excessively added, the content is preferably 2% or less, more preferably 1% or less, and even more preferably 0.5% or less, based on the mass% of the oxide. The lower limit is not particularly limited, and is typically preferably 0.05% or more in total in terms of mass% based on oxides.

Regarding the use of SO ₃ SO when used as clarifying agent ₃ When the content of (2) is too small, no effect is observed, and thus SO is expressed in mass% based on oxide ₃ The content of (2) is preferably 0.01% or more, more preferably 0.05% or more, and still more preferably 0.1% or more. In addition, SO is used in mass% based on oxide ₃ SO in the case of clarifying agents ₃ The content of (2) is preferably 1% or less, more preferably 0.8% or less, and still more preferably 0.6% or less.

Since the Cl content when Cl is used as the clarifier affects physical properties such as strengthening properties when excessively added, the Cl content is preferably 1% or less, more preferably 0.8% or less, and even more preferably 0.6% or less, based on the mass% of the oxide. In addition, when Cl is used as the clarifier, since no effect is observed when the Cl content is too small, the Cl content is preferably 0.05% or more, more preferably 0.1% or more, and even more preferably 0.2% or more, in terms of mass% based on the oxide.

SnO is used in mass% based on oxide ₂ SnO as fining agent ₂ The content of (2) is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.3% or less. In addition, regarding the use of SnO ₂ SnO as fining agent ₂ When the content of (2) is too small, no effect is observed, and thus SnO is present in mass% based on the oxide ₂ The content of (2) is preferably 0.02% or more, more preferably 0.05% or more, and still more preferably 0.1% or more.

Preferably does not contain P ₂ O ₅ . Containing P ₂ O ₅ P in case of (2) ₂ O ₅ The content of (2) is preferably 2.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, and most preferably contains no P ₂ O ₅ 。

Preferably without As ₂ O ₃ . Containing As ₂ O ₃ As in the case of (2) ₂ O ₃ The content of (2) is preferably 0.3% or less, more preferably 0.1% or less, and most preferably no As is contained ₂ O ₃ 。

Method for producing chemically strengthened glass

A method for producing chemically strengthened glass according to an embodiment of the present invention (hereinafter, also simply referred to as the present production method) will be described below.

The manufacturing method is characterized by comprising the following steps (1) - (3) in order.

(1) An ion exchange step of ion-exchanging the lithium-containing glass at least once with a first inorganic salt composition containing potassium; (2) The lithium-containing glass and the LiNO-containing glass are mixed ₃ And NaNO ₃ And NaNO ₃ Relative to LiNO ₃ Mass ratio NaNO of (2) ₃ /LiNO ₃ A second inorganic material of 0.25 to 3.0A reverse ion exchange step of contacting the salt composition at 425 ℃ or higher for 5 hours or longer; (3) And a secondary ion exchange step of subjecting the lithium-containing glass to at least one ion exchange with a third inorganic salt composition containing potassium.

Hereinafter, each step will be described.

Process (1)

The step (1) is a step of bringing the lithium-containing glass into contact with the first inorganic salt composition containing potassium to perform ion exchange at least once or more. The lithium-containing glass may be of the following composition: lithium-containing composition that can be molded and reinforced by a chemical reinforcing treatment. Examples of the glass include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.

The preferred composition of the lithium-containing glass is the same as the composition described in the expression "< composition > for the chemically strengthened glass. That is, the basic composition preferably contains, in mole% based on oxides: 52% -75% of SiO ₂ 8% -20% of Al ₂ O ₃ 5-18% Li ₂ O. The glass having the above preferred basic composition has a property that potassium is hardly diffused in the glass by ion exchange, but according to the present production method, a large amount of potassium ions are introduced into the surface layer of the glass, and the surface strength can be improved.

The chemical strengthening treatment for forming a compressive stress layer on the surface layer of glass is a treatment for bringing the glass into contact with a first inorganic salt composition to replace metal ions in the glass with metal ions having a larger ionic radius than the metal ions in the first inorganic salt composition.

Examples of the method of bringing the glass into contact with the first inorganic salt composition include a method of applying a paste-like inorganic salt composition to the glass, a method of spraying an aqueous solution of the inorganic salt composition onto the glass, and a method of immersing the glass sheet in a salt bath of molten salt of the inorganic salt composition heated to a melting point or higher. Among them, a method of immersing glass in molten salt of the inorganic salt composition is preferable from the viewpoint of improving productivity.

The chemical strengthening treatment by the method of immersing the glass in the molten salt of the first inorganic salt composition can be carried out, for example, by the following operation steps. First, the glass is preheated to 100 ℃ or higher, and the molten salt is adjusted to a temperature at which chemical strengthening is performed. Then, the preheated glass is immersed in the molten salt for a predetermined time, and then the glass is lifted from the molten salt and cooled.

The salt contained in the first inorganic salt composition used in the ion exchange in the step (1) is not particularly limited, and examples thereof include: sodium nitrate, sodium carbonate, sodium chloride, sodium borate, sodium sulfate, potassium nitrate, potassium carbonate, potassium chloride, potassium borate, potassium sulfate, lithium nitrate, lithium carbonate, lithium chloride, lithium borate, and lithium sulfate may be added singly or in combination. As the first inorganic salt composition containing potassium, for example, an inorganic salt composition containing sodium nitrate or potassium nitrate is preferably cited.

The contact temperature between the lithium-containing glass and the first inorganic salt composition in the step (1) is not particularly limited, but is preferably 310 ℃ or higher, more preferably 330 ℃ or higher, and even more preferably 350 ℃ or higher, from the viewpoint of increasing the ion exchange rate and improving the productivity. In addition, from the viewpoint of reducing volatilization of salt, the contact temperature is preferably 530 ℃ or lower, more preferably 500 ℃ or lower, and further preferably 480 ℃ or lower.

The contact time between the lithium-containing glass and the first inorganic salt composition in the step (1) is not particularly limited, but is preferably 30 minutes or longer, more preferably 45 minutes or longer, and even more preferably 1 hour or longer, from the viewpoint of reducing the variation in the ion exchange level due to the time variation. In addition, from the viewpoint of improving productivity, it is preferably 20 hours or less.

The ion exchange in the step (1) may be carried out at least once by contacting the first inorganic salt composition containing potassium, and may be carried out in one step or two or more steps.

Examples of the ion exchange in the step (1) at two or more steps include the following ion exchange.

As the first step of ion exchange, it is preferable to subject the glass plate to ion exchange with a solution containing NaNO in an amount of 20% by mass or more ₃ In the glass, the Li ions in the glass are ion-exchanged with Na ions in the inorganic salt composition, and then, as the ion exchange in the second step, the glass plate is preferably ion-exchanged with KNO containing 80 mass% or more ₃ To allow Na ions in the glass to ion-exchange with K ions in the inorganic salt composition.

NaNO in the inorganic salt composition at the time of the first ion exchange ₃ The content of (2) is preferably 30% by mass or more, more preferably 40% by mass or more. In addition, KNO in the inorganic salt composition at the time of the second step ion exchange ₃ The content of (2) is more preferably 85 mass% or more, and still more preferably 90 mass% or more.

In the step (1), the Compressive Stress (CS) of the outermost surface of the compressive stress layer formed on the surface layer of the lithium-containing glass is not particularly limited, and is usually preferably 600MPa or more, more preferably 650MPa or more, and still more preferably 700MPa or more.

Process (2)

The step (2) is a reverse ion exchange step as follows: by mixing lithium-containing glass with LiNO ₃ And NaNO ₃ And (2) contacting the second inorganic salt composition with ions in the lithium-containing glass, and performing ion exchange with ions having an ionic radius smaller than that of the ions, thereby reducing the compressive stress of the compressive stress layer formed in the step (1). More specifically, for example, K ions in the glass are exchanged with Na ions in the second inorganic salt composition and Na ions in the glass are exchanged with Li ions in the second inorganic salt composition.

The second inorganic salt composition used in the step (2) contains LiNO ₃ And NaNO ₃ ，NaNO ₃ Relative to LiNO ₃ Mass ratio NaNO of (2) ₃ /LiNO ₃ Is 0.25 to 3.0 inclusive. By making the mass ratio NaNO ₃ /LiNO ₃ The Na ion concentration of the glass surface layer can be sufficiently reduced to 0.25 to 3.0 inclusive, and the reverse ion exchange efficiency can be improved. From improving the effect of counter ion exchangeFrom the viewpoint of the rate, the mass ratio NaNO ₃ /LiNO ₃ More preferably 0.40 or more, still more preferably 0.55 or more, and particularly preferably 0.75 or more. In addition, the mass ratio NaNO ₃ /LiNO ₃ More preferably 2.5 or less, still more preferably 1.8 or less, and particularly preferably 1.3 or less.

LiNO contained in the second inorganic salt composition used in step (2) ₃ The content of (c) is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 40% by mass or more. In addition, the LiNO contained in the second inorganic salt composition ₃ The content of (c) is preferably 75% by mass or less, more preferably 70% by mass or less, and still more preferably 65% by mass or less.

In the second inorganic salt composition, in addition to LiNO ₃ And NaNO ₃ In addition, other inorganic salts may be added. Examples of the other inorganic salts include: sodium carbonate, sodium chloride, sodium borate, sodium sulfate, potassium nitrate, potassium carbonate, potassium chloride, potassium borate, potassium sulfate, lithium carbonate, lithium chloride, lithium borate, lithium sulfate.

Wherein, even if LiNO is not increased ₃ From the viewpoint that the content of (2) can also improve the reverse ion exchange efficiency, KNO may be preferably exemplified ₃ . The second inorganic salt composition contains KNO ₃ In the case of (2) KNO in the second inorganic salt composition ₃ The content of (c) is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. In addition, KNO in the second inorganic salt composition ₃ The content of (c) is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 40% by mass or less.

The contact temperature between the lithium-containing glass and the second inorganic salt composition in the step (2) is 425 ℃ or higher, preferably 435 ℃ or higher, and more preferably 445 ℃ or higher. When the contact temperature is 425 ℃ or higher, the counter ion exchange efficiency can be improved to sufficiently separate ions from the glass, and the re-ion exchange efficiency in the step (3) can be improved to improve the strength. In addition, the expansion of the glass caused by the steps (1) and (2) can be suppressed. In addition, from the viewpoint of reducing volatilization of salt, the contact temperature is preferably 500 ℃ or lower, more preferably 485 ℃ or lower, and further preferably 470 ℃ or lower.

The contact time between the lithium-containing glass and the second inorganic salt composition in the step (2) is preferably 4 hours or more, more preferably 6 hours or more, and even more preferably 8 hours or more, from the viewpoints of improving the reverse ion exchange efficiency by reducing the variation in the ion exchange level due to the time variation and suppressing the expansion of the glass caused by the steps (1) and (2). Further, from the viewpoint of improving productivity, it is preferably 72 hours or less, more preferably 48 hours or less, and still more preferably 24 hours or less.

The lower the compressive stress of the compressive stress layer reduced by the step (2), the more preferable, and most preferable, the complete removal of the compressive stress layer. For example, the Compressive Stress (CS) of the compressive stress layer after the first ion exchange step is preferably 10MPa or less, more preferably 7MPa or less, still more preferably 4MPa or less, and most preferably 0MPa at a depth of 50 μm from the surface. The compressive stress on the glass surface after the step (2) may be 100MPa or less, preferably 50MPa or less, more preferably 20MPa or less, and still more preferably 10MPa or less.

The expansion ratio of the length of the lithium-containing glass subjected to the counter ion exchange in the step (2) in the longitudinal direction is preferably 0.4% or less, more preferably 0.3% or less, still more preferably 0.2% or less, and most preferably 0.1% or less, relative to the lithium-containing glass before the ion exchange in the step (1). By setting the expansion ratio to 0.4% or less, warpage of the glass or the like accompanying an increase in expansion ratio can be suppressed. The lower limit of the expansion ratio is not particularly limited, and the closer to 0% is preferable, but is usually-0.05% or more.

Process (A)

The present production method may include the following step (a) between the counter ion exchange step of step (2) and the re-ion exchange step of step (3). (A) And removing 0.5-15 [ mu ] m of the surface of the lithium-containing glass on one surface or both surfaces.

In the removal of the lithium-containing glass surface in the step (A), the surface concentration is 0.5 μm or more, preferably 0.7 μm or more, more preferably 0.9 μm or more, and even more preferably 1.3 μm or more per one surface. The removal amount in the step (A) is 15 μm or less, preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less per one surface. By setting the removal amount in the step (a) within the above range, the minute flaws (defects) on the glass surface can be removed, and the cloudiness due to the reverse ion exchange can be sufficiently removed.

The amount of removal of the surface of the lithium-containing glass in the step (A) may be uneven in both surfaces, and for example, if the difference between the polishing amounts of both surfaces is preferably in the range of 3.0 μm or less, warpage can be reduced, and the difference between the polishing amounts of both surfaces is more preferably 2.0 μm or less, further preferably 1.0 μm or less, and particularly preferably 0.5 μm or less.

As means for removing the surface of the lithium-containing glass, polishing or etching of the glass surface can be cited. In the step (a), the same amount is preferably removed from the two glass plate main surfaces opposite in the plate thickness direction from the viewpoint of preventing warpage of the glass, but the conditions for removing the step (a) are not particularly limited and may be performed under conditions that give a desired surface roughness.

As the polishing means, for example, abrasive grains such as cerium oxide and colloidal silica can be used. The average particle diameter of the abrasive grains is preferably 0.02 μm to 2.0 μm, and the specific gravity of the slurry is preferably 1.03 to 1.13 as the concentration of the abrasive grains. The polishing pressure is preferably 6kPa to 20kPa, and the rotational speed of the platen of the polishing apparatus is preferably 20m to 100m per minute at the outermost peripheral speed. As an example, the method can be carried out by the following general method: cerium oxide having an average particle diameter of about 1.2 μm is dispersed in water to prepare a slurry having a specific gravity of 1.07, and the surface of the glass plate is polished with a polishing amount of 0.5 μm or more per one surface under a polishing pressure of 9.8kPa using a polishing pad having a nonwoven fabric or suede. In the polishing step, a Shore A hardness of 25 DEG to 65 DEG and 100g/cm can be used ² A polishing pad having a sinking amount of 0.05mm or more and a nonwoven fabric or suede surface. Among them, a polishing pad using a nonwoven fabric is preferable in terms of cost.

As the removal of the glass surface by etching, for example, etching with a reagent containing hydrofluoric acid is cited.

Process (3)

The step (3) is a re-ion exchange step as follows: the lithium-containing glass having reduced compressive stress in the step (2) is contacted with an inorganic salt composition, and ion-exchange is performed at least once or more with a third inorganic salt composition containing potassium, so that the compressive stress of a compressive stress layer formed on the surface layer of the glass sheet is increased.

Specifically, in the step (3), ions in the glass are ion-exchanged with ions having an ion radius larger than that of the ions, thereby increasing the compressive stress of the compressive stress layer. More specifically, for example, na ions in the glass are exchanged with K ions in the third inorganic salt composition and Li ions in the glass are exchanged with Na ions in the third inorganic salt composition.

Examples of the salt contained in the third inorganic salt composition used in the ion exchange in the step (3) include: sodium nitrate, sodium carbonate, sodium chloride, sodium borate, sodium sulfate, potassium nitrate, potassium carbonate, potassium chloride, potassium borate, and potassium sulfate may be added singly or in combination.

The type of salt and the content thereof contained in the third inorganic salt composition used in the ion exchange in the step (3) can be appropriately set so as to obtain a desired compressive stress and depth of layer of the compressive stress.

For example, as a method for ion-exchanging Na ions in glass with K ions in the third inorganic salt composition, a KNO containing preferably 20 mass% or more, more preferably 30 mass% or more, still more preferably 40 mass% or more is preferably used as the third inorganic salt composition ₃ Is a third inorganic salt composition of (a).

The ion exchange in the step (3) may be carried out at least once by contacting with the third inorganic salt composition containing potassium, and may be carried out in one step or two or more steps.

Examples of the ion exchange in the step (3) at two or more steps include the following ion exchange.

NaNO in the inorganic salt composition at the time of the first ion exchange ₃ The content of (2) is more preferably 30% by mass or more, and still more preferably 40% by mass or more. In addition, KNO in the inorganic salt composition during the ion exchange in the second step ₃ The content of (2) is more preferably 85 mass% or more, and still more preferably 90 mass% or more.

The contact temperature between the lithium-containing glass and the third inorganic salt composition in the ion exchange in the step (3) is not particularly limited, but is preferably 310 ℃ or higher, more preferably 330 ℃ or higher, and even more preferably 350 ℃ or higher, from the viewpoint of increasing the ion exchange rate and improving the productivity. In addition, from the viewpoint of reducing volatilization of salt, the contact temperature is preferably 530 ℃ or lower, more preferably 500 ℃ or lower, and further preferably 480 ℃ or lower.

The contact time between the lithium-containing glass and the third inorganic salt composition in the ion exchange in the step (3) is not particularly limited, but is preferably 30 minutes or longer, more preferably 45 minutes or longer, and even more preferably 1 hour or longer, from the viewpoint of reducing the variation in the ion exchange level due to the time variation. In addition, from the viewpoint of improving productivity, it is preferably 20 hours or less.

When the ion exchange in the step (1) and the ion exchange in the step (3) each include two-step ion exchange, the time of the first-step ion exchange included in the ion exchange in the step (3) is preferably longer than the time of the first-step ion exchange included in the ion exchange in the step (1). In this way, na ions excessively released from the glass surface in the step (2) can be sufficiently introduced into the glass surface layer.

In the present manufacturing method, it is preferable that a step of cleaning glass is further included between the steps. Industrial water, ion-exchanged water, and the like can be used for the washing. The conditions for cleaning are different depending on the cleaning liquid, and in the case of using ion-exchanged water, it is preferable in that the attached salt can be completely removed when the cleaning is performed at a temperature of 0 to 100 ℃. In the cleaning step, various methods such as a method of immersing the glass in a water tank containing ion-exchanged water or the like, a method of exposing the glass surface to running water, and a method of spraying a cleaning liquid onto the glass surface by spraying can be used.

The Compressive Stress (CS) of the compressive stress layer of the chemically strengthened glass produced by the present production method is not particularly limited, but is preferably 50MPa or more, more preferably 60MPa or more, and still more preferably 70MPa or more, at a depth of 50 μm from the surface. The surface compressive stress of the chemically strengthened glass produced by the present production method is not particularly limited, and may be 500MPa or more, preferably 600MPa or more, more preferably 700MPa or more, and still more preferably 800MPa or more.

Examples

The present invention will be described below by way of examples, but the present invention is not limited thereto.

< production of chemically strengthened glass >

The glass raw materials were prepared so as to have the following composition shown in terms of mole percent based on oxides, and the glass raw materials were weighed so as to be 400g in terms of glass. Then, the mixed raw materials are put into a platinum crucible, put into an electric furnace at 1500-1700 ℃ and melted for about 3 hours, and defoamed and homogenized.

Glass material a: siO (SiO) ₂ 69.2％、Al ₂ O ₃ 12.4％、MgO 0.1％、CaO 0.1％、ZrO ₂ 0.3％、Y ₂ O ₃ 1.3％、Li ₂ O 10.6％、Na ₂ O 4.7％、K ₂ O 1.2％

The obtained molten glass was poured into a metal mold, held at a temperature higher than the glass transition temperature by about 50 ℃ for 1 hour, and then cooled to room temperature at a rate of 0.5 ℃/minute, whereby a glass gob was obtained. From the obtained glass block, a glass plate of 50mm×50mm×0.7mm was produced.

Step (1): ion exchange process

Using the glass plate obtained above, the glass plate was immersed in an inorganic salt composition under the conditions shown in table 1, and ion exchange treatment was performed. In table 1, the cases described as "first step" and "second step" were carried out after the first ion exchange treatment. Between each ion exchange, the surface of the glass plate is washed and dried.

Step (2): reverse ion exchange process

After the ion exchange step, the glass plate was immersed in the inorganic salt composition under the conditions shown in table 1, and ion exchange treatment was performed to perform counter ion exchange. Then, the surface of the glass plate is cleaned and dried.

Step (A): removal step

As the polishing slurry, cerium oxide having an average particle diameter (d 50) of 1.2 μm was dispersed in water to prepare a slurry having a specific gravity of 1.07. Next, using the obtained slurry, a Shore A hardness of 58℃and a Shore A hardness of 100g/cm were used ² The nonwoven fabric polishing pad having a sinking amount of 0.11mm was polished at the same time at a polishing pressure of 9.8kPa on both sides of the glass panel by 5 μm.

Step (3): ion exchange step again

After the removal step, the glass plate was immersed in the inorganic salt composition under the conditions shown in table 1, and ion-exchanged, followed by ion exchange treatment. Then, the surface of the glass plate is cleaned and dried.

< evaluation >

The various evaluations in this example were performed by the following methods.

(EPMA)

K of glass ₂ O concentration or Na ₂ The O concentration was determined by EPMA as follows. First, epoxy is usedThe glass sample was mechanically polished in a direction perpendicular to the first main surface and the second main surface opposite to the first main surface, thereby producing a cross-section sample. The polished cross section was C-coated and measured by EPMA (JXA-8500F, manufactured by JEOL Co.).

The acceleration voltage was set at 15kV, the probe current was set at 30nA, the accumulation time was set at 1000 msec/point, and K was obtained at 1 μm intervals ₂ O or Na ₂ Line distribution of X-ray intensity of O. Regarding the obtained K ₂ O concentration distribution and Na ₂ The O concentration distribution was calculated by scaling the total plate thickness count to mol% with the average count of the plate thickness center portion (0.5×t) + -25 μm (plate thickness is t μm) as the main body composition, and the slope (%/μm) in each region shown in Table 2 was obtained.

(stress distribution)

The stress of the chemically strengthened glass was measured by the method described in International publication No. 2018/056121 using a scattered light photoelastic stress meter (SLP-2000 manufactured by the manufacturing of a folding original). Further, stress distribution was calculated using an attached soft [ SlpV (Ver.2019.11.07.001) ] of a scattered light photoelastic stress meter (SLP-2000 manufactured by the manufacture of a folder).

The function used to obtain the stress distribution 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, erfc is a complementary error function. The complementary error function is defined by the following equation.

In the evaluation in the present specification, the fitting parameters are optimized by minimizing the sum of squares of residuals of the resulting raw data and the above-described functions. The measurement process conditions were set to be single, and regarding the measurement region process adjustment items, a fitting curve was specified/selected by the surface specification/selection edge method, 6.0 μm was specified/selected at the inner surface end, automatic was specified/selected at the inner left and right ends, automatic was specified/selected at the inner deep end (sample film thickness center), and extension of the phase curve to the sample thickness center was specified/selected.

The stress of the surface layer portion of the glass having a thickness of several tens μm or less from the surface of the glass was measured by the method described in International publication Nos. 2018/056121 and 2017/115811 using a glass surface stress meter (FSM 6000-UV manufactured by the manufacturing of a folding origin).

Further, the concentration distribution (sodium ion and potassium ion) of alkali metal ions in the cross section direction was measured simultaneously by SEM-EDX (EPMA), and it was confirmed that there was no contradiction between the obtained stress distribution.

In addition, based on the obtained stress distribution, the compressive stress CS is calculated by the above method ₀ 、DOL、CS ₅₀ 、CS ₉₀ Values for CTave, CT-Max, DOC.

(depth of Potassium ion diffusion layer)

Regarding the depth of the potassium ion diffusion layer, the depth of the diffusion layer is set to be equal to K obtained by EPMA ₂ Average K of the center portion (0.5×t) + -25 μm of the plate thickness in the O concentration distribution ₂ The O concentration (%) and the variance value σ thereof are measured from the outermost surface side by using K ₂ The depth (μm) at which the O concentration falls within the range of +2σ or less is used as the potassium ion diffusion layer depth.

(expansion ratio)

The rate of change in the length of the glass sheet in the longitudinal direction after the ion exchange step of step (3) relative to the length of the glass sheet in the longitudinal direction before the ion exchange step (1) was obtained and used as the expansion rate. The length of the glass plate was measured using a digital vernier caliper manufactured by Mitutoyo corporation.

(4 PB Strength)

The glass for chemical strengthening was cut into 50mm×50mm, and a 50mm×50mm×0.7mm thick glass obtained by automatic chamfering (C chamfering) using a 1000-size grindstone (manufactured by tokyo diamond tool) was processed in the order of steps (1), (2), (a) and (3), and then subjected to a four-point bending test under conditions of a distance between outer fulcrums of 30mm, a distance between inner fulcrums of 10mm and a crosshead speed of 5.0 mm/min, to determine four-point bending strength. The number of test pieces was 10.

The results of evaluating the chemically strengthened glass are shown in table 2. In tables 1 and 2, examples 1 to 4 are examples, and example 5 is a comparative example. The stress distributions of examples 1 and 5 are shown in fig. 1. K of examples 1, 2 and 5 ₂ O concentration or Na ₂ The O concentration distribution is shown in fig. 2 to 4, respectively.

In table 2, the respective reference numerals are as follows. "n.d." means not evaluated.

t [ mu ] m: plate thickness

CS ₀ [MPa]: compressive stress of glass surface

DOL (also known as DOL-tail) μm: depth of layer of compressive stress determined using FSM (Curve fitting)

CS ₅₀ [MPa]: compressive stress at a depth of 50 μm from the glass surface

CS ₉₀ [MPa]: compressive stress at a depth of 90 μm from the glass surface

CTave [ MPa ]: average value of tensile stress

CT-Max (MPa): maximum tensile stress

DOC [ mu ] m: compressive stress depth determined using SLP-2000

mK1-3[ mol%/μm]：K ₂ Slope in the range of 1 μm to 3 μm in depth in O concentration distribution

mK5-10[ mol%/μm]：K ₂ Slope in the range of 5 μm to 10 μm in depth in O concentration distribution

mNa10-50[ mol%/μm]：Na ₂ Slope in the range of 10 μm to 50 μm in depth in O concentration distribution

mNa50-90[ mol%/μm]：Na ₂ Slope in the range of 50 μm to 90 μm in depth in O concentration distribution

mK5-10/mK 1-3: by K ₂ Absolute value of a value obtained by dividing a slope of 5 μm to 10 μm in depth by a slope of 1 μm to 3 μm in depth in the O concentration distribution

mNa50-90/mNa10-50|: with Na ₂ The slope in the range of 50 μm to 90 μm in depth in the O concentration profile divided by the slope in the range of 10 μm to 50 μm in depthAbsolute value of value obtained by slope in range

Depth 15-25 μm and K of central part ₂ Absolute value of difference in O concentration [%]: k in a range of 15 μm to 25 μm in depth ₂ O concentration (%) and K in the center portion ₂ Absolute value of difference in O concentration (%)

4PB intensity: average value of four-point bending strength measurement results for 10 test pieces

TABLE 2

As shown in table 2, example 1 as an example shows excellent 4PB strength compared to example 5 as a comparative example. As shown in table 2 and fig. 1 (a), examples 1 and 2 as examples have a large amount of K ions introduced into the surface layer, and have high stress in the surface layer portion, and exhibit excellent strength, as compared with example 5 as a comparative example. In example 3, a large amount of K ions was introduced into the surface layer, and the surface compressive stress CS was higher than that of the comparative example ₀ High and excellent strength. In example 4, which is a comparative example, a large amount of K ions were introduced into the surface layer, and the compressive stress depth DOC was deep, and the strength was excellent.

CS of example 1 as an example compared with example 3 as an example ₅₀ And DOC is higher. From the results, it is found that the CS can be improved by the first ion exchange time in the step (3) being longer than the first ion exchange time in the step (1) ₅₀ And DOC, further improving the drop strength.

In addition, the glass of example 3 has a lower expansion ratio than example 4. From the results, it was found that NaNO in the step (2) ₃ /LiNO ₃ If the ratio (a) is small, the expansion ratio up to the step (2) can be reduced, and therefore the expansion ratio after the step (3) can also be reduced.

Further, a glass (glass material B) having a composition different from that of the glass (glass material a) used in the above example was prepared, and a glass for chemical strengthening was produced using the glass. The glass raw material was prepared so as to have a composition shown below as a mole percentage based on oxide, and the glass raw material was weighed so as to be 400g in terms of glass. Then, the mixed raw materials are put into a platinum crucible, put into an electric furnace at 1500-1700 ℃ and melted for about 3 hours, and defoamed and homogenized.

Glass material B: siO (SiO) ₂ 66.2％、Al ₂ O ₃ 11.2％、MgO 3.1％、CaO 0.2％、ZrO ₂ 1.3％、Y ₂ O ₃ 0.5％、Li ₂ O 10.4％、Na ₂ O 5.6％、K ₂ O 1.5％

The obtained molten glass was poured into a metal mold, held at a temperature higher than the glass transition temperature by about 50 ℃ for 1 hour, and then cooled to room temperature at a rate of 0.5 ℃/minute, whereby a glass gob was obtained. From the obtained glass block, a glass plate of 50mm×50mm×0.6mm was produced.

The following applies to step (1): ion exchange step, step (2): a reverse ion exchange step (a): removing step, step (3): in the ion exchange step, chemically strengthened glass was produced under the conditions shown in table 3.

Various evaluations of chemically strengthened glass in which glass of glass material B was chemically strengthened were performed by the same method as that for chemically strengthened glass in which glass of glass material a was chemically strengthened.

The results of chemically strengthened glass for glass of glass material B are shown in table 4. In tables 3 and 4, examples 6 to 9 are examples, and example 10 is a comparative example.

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TABLE 4 Table 4

As shown in Table 4, in examples 6 to 9, the slope mK1-3[ mol%/μm ] in the range of 1 μm to 3 μm was-1.9 or more, and the slope mK5-10[ mol%/μm ] in the range of 5 μm to 10 μm was-0.001 or less, as in examples 1 to 4.

The following verification was performed for examples 6 to 9 as examples.

It can be seen that:

similarly to examples 1 to 4, examples 6 to 9, which are examples, have absolute values |mK5-10/mK1-3| of values obtained by dividing a slope (%/μm) in a range of 5 μm to 10 μm by a slope (%/μm) in a range of 1 μm to 3 μm, and the absolute values are not less than 0.005 and not more than 0.10.

Similarly to examples 1 to 4, examples 6 to 9, which are examples, have absolute values | mNa50 to 90/mNa10 to 50| of 0.50 to 4.0, which are obtained by dividing the slope (%/μm) in the range of 50 μm to 90 μm by the slope (%/μm) in the range of 10 μm to 50 μm.

Like examples 1 to 4, examples 6 to 9 were used as examples, and K was in the range of 15 μm to 25 μm in depth ₂ O concentration (%) and K in the center of the plate thickness ₂ The absolute value of the difference between the O concentrations (%) is 0.20% or less.

The diffusion layer depth of potassium ions in examples 6 to 9 was 5 μm or more as in examples 1 to 4.

The slopes mK1-3[ mol%/μm ] in the range of 1 μm to 3 μm in examples 6 to 9 as examples showed larger values and the slopes mK5-10[ mol%/μm ] in the range of 5 μm to 10 μm in depth showed smaller values than those of example 5 as comparative example in which the reverse ion exchange step was not performed.

In examples 6 to 9, which are comparative examples, a large amount of K ions were introduced in the range of 15 μm to 25 μm in depth, and high stress was exhibited in the surface layer portion, and excellent strength was exhibited, compared with example 10, which was a comparative example, in which no ion exchange step was performed.

As described above, the following matters are disclosed in the present specification.

1. A chemically strengthened glass wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents K in mole percent based on oxide ₂ K of O concentration (%) ₂ K in the range of 1 μm to 3 μm in depth in the O concentration distribution ₂ The slope (%/μm) of the O concentration is-1.9 or more, and K is in the range of 5 μm to 10 μm in depth ₂ The slope (%/μm) of the O concentration is-0.001 or less.

2. The chemically strengthened glass according to the above 1, wherein the horizontal axis represents depth (. Mu.m) from the surface and the vertical axis represents Na in mole percent based on oxide ₂ Na of O concentration (%) ₂ In the O concentration distribution, na is in a range of 10 μm to 50 μm in depth ₂ The slope (%/μm) of the O concentration is-0.001 or less, and Na is in the range of 50 μm to 90 μm in depth ₂ The slope (%/μm) of the O concentration is-0.012 or more.

3. The chemically strengthened glass as defined in 1 or 2 wherein, in said K ₂ In the O concentration distribution, K having a depth of 5 μm to 10 μm is used ₂ Slope of O concentration (%/μm) divided by K in the range of 1 μm to 3 μm in depth ₂ The absolute value of the value obtained by the slope (%/μm) of the O concentration is 0.005 to 0.10.

4. The chemically strengthened glass according to any one of the above 1 to 3, wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents Na in mole percent based on oxide ₂ Na of the chemically strengthened glass of O concentration (%) ₂ In the distribution of the concentration of O,

with Na having a depth ranging from 50 μm to 90 μm ₂ Slope of O concentration (%/μm) divided by Na in the range of 10 μm to 50 μm in depth ₂ The absolute value of the value obtained by the slope (%/μm) of the O concentration is 0.50 to 4.0.

5. The chemically strengthened glass according to any one of the above 1 to 4, wherein, in the above K ₂ In the O concentration distribution, the depth is 15 muK in the range of m to 25 μm in depth ₂ O concentration (%) and K in the center of the plate thickness ₂ The absolute value of the difference between the O concentrations (%) is 0.20% or less.

6. The chemically strengthened glass according to any one of 1 to 5, wherein a diffusion layer depth of potassium ions is 5 μm or more.

7. The chemically strengthened glass according to any one of the above 1 to 6, wherein the chemically strengthened glass is a lithium-containing glass.

8. The chemically strengthened glass according to any one of the above 1 to 7, wherein the chemically strengthened glass has a basic composition comprising, in mole percent based on oxides:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ And (d) sum

5 to 18 percent of Li ₂ O。

9. The chemically strengthened glass according to any one of the above 1 to 8, wherein the chemically strengthened glass has a basic composition comprising, in mole percent based on oxides:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ 、

5 to 18 percent of Li ₂ O、

0 to 15 percent of Na ₂ O、

0 to 5 percent of K ₂ O、

0 to 20 percent of MgO,

0 to 20 percent of CaO,

0 to 20 percent of SrO,

0 to 20 percent of BaO,

0 to 10 percent of ZnO,

0 to 1 percent of TiO ₂ 、

ZrO 0-8% ₂ And (d) sum

0 to 5% of Y ₂ O ₃ 。

10. A method for producing chemically strengthened glass, comprising the following steps (1) to (3) in this order:

11. The method for producing a chemically strengthened glass according to claim 10, wherein the lithium-containing glass comprises, in mole percent based on oxides:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ And (d) sum

5 to 18 percent of Li ₂ O。

12. The method for producing a chemically strengthened glass according to claim 10 or 11, wherein the lithium-containing glass comprises, in mole percent based on oxide:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ 、

5 to 18 percent of Li ₂ O、

0 to 15 percent of Na ₂ O、

0 to 5 percent of K ₂ O、

0 to 20 percent of MgO,

0 to 20 percent of CaO,

0 to 20 percent of SrO,

0 to 20 percent of BaO,

0 to 10 percent of ZnO,

0 to 1 percent of TiO ₂ 、

ZrO 0-8% ₂ And (d) sum

0 to 5% of Y ₂ O ₃ 。

13. The method for producing a chemically strengthened glass according to any one of the above 10 to 12, wherein,

the ion exchange in (1) and the ion exchange in (3) each comprise a two-step ion exchange, and the time of the first-step ion exchange included in the ion exchange in (3) is longer than the time of the first-step ion exchange included in the ion exchange in (1).

14. The method for producing a chemically strengthened glass according to any one of the above 10 to 13, wherein the following (A) is contained between the above (2) and the above (3):

(A) And removing 0.5-15 [ mu ] m of the surface of the lithium-containing glass on one surface or both surfaces of the glass.

15. The method for producing a chemically strengthened glass according to claim 14, wherein in (A), the surface of the lithium-containing glass is polished in a range where the difference between the polishing amounts of both surfaces is 3.0 μm or less.

16. A chemically strengthened glass wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents K in mole percent based on oxide ₂ K of O concentration (%) ₂ In the distribution of the concentration of O,

k is in a range of 1 μm to 3 μm in depth ₂ The slope (%/μm) of the O concentration is-1.9 to 0.0, and K is in the range of 5 μm to 10 μm in depth ₂ The slope (%/μm) of the O concentration is-0.001 or less.

17. The chemically strengthened glass according to item 16, wherein K is in a range of 1 μm to 3 μm in depth ₂ The slope (%/μm) of the O concentration is-1.9 or more and-1.000 or less.

18. The chemically strengthened glass according to item 16, wherein K is in a range of 5 μm to 10 μm in depth ₂ The slope (%/μm) of the O concentration is-0.200 or more and-0.001 or less.

While the application has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. The present application is based on Japanese patent application (Japanese patent application No. 2022-034686) filed on 3 month 7 of 2022 and Japanese patent application (Japanese patent application No. 2022-166402) filed on 10 month 17 of 2022, the contents of which are incorporated herein by reference.

Claims

1. A chemically strengthened glass wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents K in mole percent based on oxide ₂ K of O concentration (%) ₂ In the distribution of the concentration of O,

k is in a range of 1 μm to 3 μm in depth ₂ The slope (%/μm) of the O concentration is-1.9 or more, and K is in the range of 5 μm to 10 μm in depth ₂ The slope (%/μm) of the O concentration is-0.001 or less.

2. The chemically strengthened glass according to claim 1, wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents Na in mole percent based on oxide ₂ Na of O concentration (%) ₂ In the distribution of the concentration of O,

na in a depth range of 10 μm to 50 μm ₂ The slope (%/μm) of the O concentration is-0.001 or less, and Na is in the range of 50 μm to 90 μm in depth ₂ The slope (%/μm) of the O concentration is-0.012 or more.

3. The chemically strengthened glass of claim 1 wherein, at the K ₂ In the O concentration distribution, K having a depth of 5 μm to 10 μm is used ₂ Slope of O concentration (%/μm) divided by K in the range of 1 μm to 3 μm in depth ₂ The absolute value of the value obtained by the slope (%/μm) of the O concentration is 0.005 to 0.10.

4. The chemically strengthened glass according to claim 1, wherein the horizontal axis represents depth (μm) from the surface and the vertical axis represents Na in mole percent based on oxide ₂ Na of the chemically strengthened glass of O concentration (%) ₂ In the distribution of the concentration of O,

5. The chemically strengthened glass of claim 1 wherein, at the K ₂ K in the range of 15 μm to 25 μm in depth in the O concentration distribution ₂ O concentration (%) and K in the center of the plate thickness ₂ The absolute value of the difference between the O concentrations (%) is 0.20% or less.

6. The chemically strengthened glass according to claim 1, wherein the diffusion layer depth of potassium ions is 5 μm or more.

7. The chemically strengthened glass of any one of claims 1 to 6, wherein the chemically strengthened glass is a lithium-containing glass.

8. The chemically strengthened glass of any one of claims 1 to 6, wherein the chemically strengthened glass has a base composition comprising, in mole percent on an oxide basis:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ And (d) sum

5 to 18 percent of Li ₂ O。

9. The chemically strengthened glass of any one of claims 1 to 6, wherein the chemically strengthened glass has a base composition comprising, in mole percent on an oxide basis:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ 、

5 to 18 percent of Li ₂ O、

0 to 15 percent of Na ₂ O、

0 to 5 percent of K ₂ O、

0 to 20 percent of MgO,

0 to 20 percent of CaO,

0 to 20 percent of SrO,

0 to 20 percent of BaO,

0 to 10 percent of ZnO,

0 to 1 percent of TiO ₂ 、

ZrO 0-8% ₂ And (d) sum

0 to 5% of Y ₂ O ₃ 。

11. The method for producing a chemically strengthened glass according to claim 10, wherein the lithium-containing glass contains, in terms of mole percent based on oxide:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ And (d) sum

5 to 18 percent of Li ₂ O。

12. The method for producing a chemically strengthened glass according to claim 11, wherein the lithium-containing glass contains, in terms of mole percent based on oxide:

52% -75% of SiO ₂ 、

8% -20% of Al ₂ O ₃ 、

5 to 18 percent of Li ₂ O、

0 to 15 percent of Na ₂ O、

0 to 5 percent of K ₂ O、

0 to 20 percent of MgO,

0 to 20 percent of CaO,

0 to 20 percent of SrO,

0 to 20 percent of BaO,

0 to 10 percent of ZnO,

0 to 1 percent of TiO ₂ 、

ZrO 0-8% ₂ And (d) sum

0 to 5% of Y ₂ O ₃ 。

13. The method for producing a chemically strengthened glass according to any one of claims 10 to 12, wherein,

14. The method for producing a chemically strengthened glass according to any one of claims 10 to 12, wherein the following (a) is contained between the (2) and the (3):

15. The method for producing a chemically strengthened glass according to claim 14, wherein,

in the above (A), the surface of the lithium-containing glass is polished in a range where the difference between the polishing amounts of both surfaces is 3.0 μm or less.

k is in a range of 1 μm to 3 μm in depth ₂ The slope (%/μm) of the O concentration is-1.9 to 0.0, and K is 5 μm to 10 μm in depth ₂ The slope (%/μm) in the range of O concentration is-0.001 or less.

17. The chemically strengthened glass of claim 16 wherein the depth is in the range of 1 μm to 3 μm in K ₂ The slope (%/μm) of the O concentration is-1.9 or more and-1.000 or less.

18. The chemically strengthened glass of claim 16 wherein the depth is in the range of 5 μm to 10 μm in K ₂ The slope (%/μm) of the O concentration is-0.200 or more and-0.001 or less.