Chemically strengthened glass and its manufacturing method

Abstract

The purpose of this invention is to provide a chemically strengthened glass that exhibits excellent chemical strengthening properties while inhibiting coating peeling. The chemically strengthened glass is a chemically strengthened glass containing Li₂O, K₂O, and Na₂O, wherein the K₂O concentration at a depth x [μm] from the surface, expressed as a molar percentage based on oxides, is denoted as K. x [%), Let the content of K2O before chemical fortification be set as K. t / 2 When [%], K x For (K) t / 2 The maximum depth z above +0.1% is 0.5μm to 5μm.

Description

Technical Field

[0001] This invention relates to chemically strengthened glass and its manufacturing method. Background Technology

[0002] Protective glass for portable devices uses chemically strengthened glass. Chemically strengthened glass is, for example, glass that has been brought into contact with a molten salt containing alkali metal ions, causing ion exchange between the alkali metal ions in the glass and the alkali metal ions in the molten salt, thereby forming a compressive stress layer on the glass surface.

[0003] As matrix materials for such chemically strengthened glasses, amorphous glasses or microcrystalline glasses containing Li₂O are particularly superior. This is because, through ion exchange between lithium ions in the matrix material and sodium ions in the strengthening salt, compressive stress easily forms deep within the chemically strengthened glass. Since lithium and sodium ions have relatively small ionic radii, the diffusion coefficient of ion exchange is large. Furthermore, amorphous and microcrystalline glasses containing Li₂O have relatively high fracture toughness values ​​and are less prone to breakage.

[0004] Portable terminals require protective glass that allows for good finger slippage during operation. Therefore, a coating is usually applied to the surface of the protective glass. However, sometimes the resulting coating film is easily peeled off.

[0005] Patent Document 1 discloses a microcrystalline glass with excellent chemical strengthening properties. Patent Document 2 discloses a chemically strengthened glass with excellent strength and a coating for improving finger slippage that is not easily peeled off.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2019 / 022032

[0009] Patent Document 2: International Publication No. 2021 / 010376 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] One reason why Li2O-containing glass is an excellent protective glass is that the Li ions in the glass can undergo ion exchange with either the Na or K ions contained in the molten salt, thus making it easy to control the compressive stress value generated by chemical strengthening to an optimal value.

[0012] However, Patent Document 2 describes a tendency for coatings to peel off more easily when the surface resistivity of chemically strengthened glass is higher. It also describes how the content of alkali metal oxides affects surface resistivity.

[0013] For example, compared to glass containing only one or two alkali metal oxides, such as Li2O, Na2O, and K2O, even if the same amount of alkali metal oxides are present, the surface resistivity of glass containing these three alkali metal oxides increases due to the so-called mixed alkali effect.

[0014] In other words, when glass containing Li₂O is chemically strengthened, the resulting chemically strengthened glass contains all three elements: Li₂O, Na₂O, and K₂O, which makes it prone to coating peeling. On the other hand, when the glass composition and chemical strengthening conditions are adjusted to suppress coating peeling after chemical strengthening, it becomes difficult to obtain sufficient strength through chemical strengthening.

[0015] Therefore, the object of the present invention is to provide a chemically strengthened glass that exhibits excellent chemical strengthening properties and is able to suppress coating peeling.

[0016] means for solving problems

[0017] The inventors of this invention discovered that by adjusting the potassium-containing region to be extremely shallow from the glass surface in chemically strengthened glass containing Li2O, K2O, and Na2O, the increase in surface resistivity caused by the mixed alkali effect can be suppressed, thus completing this invention.

[0018] This invention relates to a chemically strengthened glass, wherein the chemically strengthened glass is of thickness t [μm] and contains Li₂O, K₂O, and Na₂O, wherein the K₂O concentration at a depth x [μm] from the surface, expressed as a molar percentage based on oxides, is denoted as K. x [%), Let the content of K2O before chemical fortification be K t / 2 When [%], K x For (K) t / 2 The maximum depth z above +0.1% is 0.5μm to 5μm.

[0019] In this chemically strengthened glass, the K₂O concentration at a depth x [μm] from the surface, expressed as a molar percentage based on oxides, is denoted as K. x [%), Let the content of K2O before chemical fortification be K t / 2 When [%], K x For (K) t / 2 The Na₂O concentration at the maximum depth z [μm] above +0.1)[%] is set as Na z [%], Let the concentration of Na₂O at a depth of 50 μm from the surface be Na. 50 When [%], |Na is preferred. z -Na 50 |<3[%].

[0020] In this chemically strengthened glass, the Na₂O concentration at a depth of 50 μm from the surface is defined as Na₂O, based on the molar percentage of oxides. 50 [%], Set the Na2O content before chemical fortification as Na t / 2 When [%], Na is preferred. 50 <Na t / 2 +7%

[0021] In this chemically strengthened glass, the concentration of K2O at a depth of 1 μm from the surface is defined as K1 [%], the concentration of Na2O at a depth of 1 μm from the surface is defined as Na1 [%], and the contents of Li2O, Na2O, and K2O before chemical strengthening are defined as Li [%]. t / 2 [%], Na t / 2 [%] and K t / 2 When [%], it is preferred to use (Li) t / 2 +Na t / 2 +K t / 2 )-2(Na1+K1)>0[%].

[0022] In this chemically strengthened glass, the surface compressive stress value CS0 is preferably 450 MPa or higher, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 Preferably, the compressive stress CS is 150 MPa or higher, and is located at a depth of 90 μm from the surface. 90 Preferably, it should be above 30 MPa.

[0023] In this chemically strengthened glass, the surface compressive stress value CS0 is preferably 450 MPa or higher, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 Preferably, the compressive stress CS is y = 124.7 × t + 21.5 [MPa] or higher, and is located at a depth of 90 μm from the surface. 90 The preferred value is y = 99.1 × t - 38.3 [MPa] or higher.

[0024] This invention also relates to a chemically strengthened glass, wherein the K ion penetration depth D is 0.5 μm to 5 μm, and the compressive stress value at the K ion penetration depth D is equal to the compressive stress value CS at a depth of 50 μm measured from the surface. 50 The absolute value of the difference is less than 150 MPa, the compressive stress value at the K ion penetration depth D is less than 350 MPa, the surface compressive stress value CS0 is more than 450 MPa, and the compressive stress value CS at a depth of 50 μm from the surface is... 50The compressive stress value CS at a depth of 90 μm measured from the surface is 150 MPa or more. 90 It is 30 MPa or more.

[0025] This chemically strengthened glass preferably contains glass-ceramics.

[0026] In terms of molar percentage based on oxides, the basic composition of this chemically strengthened glass preferably contains 40% - 75% of SiO2, 1% - 20% of Al2O3, and 5% - 35% of Li2O.

[0027] Preferably, this chemically strengthened glass is a chemically strengthened glass that has undergone ion exchange for two or more steps. Among them, CTave after the initial ion exchange, that is, the first ion exchange, is greater than CTA. CTA is calculated by the following formula (1), and CTave is calculated by the following formula (2).

[0028]

[0029] t: Plate thickness (μm)

[0030] K1c: Fracture toughness value (MPa·m 1 / 2 )

[0031] CTave = ICT / L CT …Formula (2) ICT: Integral value of tensile stress (Pa·m)

[0032] L CT : Length in the plate thickness direction of the tensile stress region (μm)

[0033] The thickness t of this chemically strengthened glass is preferably 300 μm - 1500 μm.

[0034] In this chemically strengthened glass, when the surface slope at the glass surface layer defined by CS0 / D is set as P0, it is preferably -1000 MPa / μm < P0 < -225 MPa / μm. It should be noted that P0 can be calculated by the relational formula of CS0 / D. In the above formula, CS0 is the surface compressive stress value (MPa), and D is the K ion penetration depth (μm).

[0035] In this chemically strengthened glass, when the slope of the stress distribution of the chemically strengthened glass in the region between the depth of 50 μm measured from the surface and the depth of 90 μm measured from the surface is set as P 50-90 (MPa / μm), and the slope of the stress distribution of the chemically strengthened glass in the region between the depth of 90 μm measured from the surface and the depth (DOL) (μm) where the compressive stress value is zero is set as P 90-DOL (MPa / μm), it is preferably |P 50-90 | > |P 90-DOL |, 1.8 < |P50-90 |<6.0 and 1.5<|P 90-DOL |<4.0. It should be noted that P 50-90 Able to be generated by (CS) 50 -CS 90 The relationship ) / 40 is used to calculate P. 90-DOL Able to be generated by CS 90 The formula / (DOL-90) is used to calculate the result.

[0036] In this chemically strengthened glass, the slope of the stress distribution in the region between a depth of 50 μm measured from the surface and a depth of 90 μm measured from the surface is denoted as P. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm from the surface and the depth (DOL) where the compressive stress is zero (μm). 90-DOL Under the condition of (MPa / μm), |P is preferred. 50-90 |<|P 90-DOL |、1.0<|P 50-90 |<3.0 and 1.2<|P 90-DOL |<4.0. It should be noted that P 50-90 Able to be generated by (CS) 50 -CS 90 The relationship ) / 40 is used to calculate P. 90-DOL Able to be generated by CS 90 The formula / (DOL-90) is used to calculate the result.

[0037] This invention also relates to a method for manufacturing a chemically strengthened glass, the chemically strengthened glass having a thickness of t [μm] and containing Li₂O, K₂O, and Na₂O, the method comprising chemically strengthening a glass containing Li₂O, wherein the K₂O concentration at a depth x [μm] from the surface is defined as K, based on the molar percentage of oxides in the chemically strengthened glass. x [%], Let the K2O content of the glass before chemical strengthening be K. t / 2 When [%], so that K x For (K) t / 2 Chemical enhancement is performed at a maximum depth z of 0.5 μm to 5 μm above +0.1%)[%.

[0038] In this method for manufacturing chemically strengthened glass, the Li2O-containing glass preferably comprises microcrystalline glass.

[0039] In this method for manufacturing chemically strengthened glass, the chemical strengthening preferably includes two or more ion exchange steps, wherein the CTave of the initial ion exchange, i.e., the first ion exchange, is greater than the CTA. The CTA is calculated by the following formula (1), and the CTave is calculated by the following formula (2).

[0040]

[0041] t: Plate thickness (μm)

[0042] K1c: Fracture toughness value (MPa·m) 1 / 2 )

[0043] CTave = ICT / L CT …Equation (2) ICT: Integral value of tensile stress (Pa·m)

[0044] L CT Length of the plate along the thickness direction in the tensile stress region (μm)

[0045] Invention Effects

[0046] The chemically strengthened glass of the present invention has the following advantages: it exhibits excellent chemical strengthening properties, and by making the potassium-containing region extremely shallow from the glass surface, it suppresses the increase in surface resistivity caused by the mixed alkali effect, thereby making the coating less prone to peeling. Attached Figure Description

[0047] Figure 1 (a) and (b) represent the results of Na concentration in chemically strengthened glass as determined by EPMA. Figure 1 (c) and (d) represent the results of K concentration in chemically strengthened glass as determined by EPMA. In (a)–(d), the horizontal axis represents the depth (μm) from the glass surface, and the vertical axis represents the concentration (%) as a molar percentage based on oxides.

[0048] Figure 2 This illustrates the stress distribution of a chemically strengthened glass according to one embodiment of the present invention. Detailed Implementation

[0049] Unless otherwise specified, the “~” used in this specification to indicate a range of values ​​means that the values ​​listed before and after it are used as the lower and upper limits.

[0050] In this specification, "amorphous glass" refers to glass in which no diffraction peaks indicating crystals are observed by powder X-ray diffraction as described later. "Microcrystalline glass" is glass in which crystals are precipitated by heat treatment of "amorphous glass," and thus contains crystals. In this specification, "amorphous glass" and "microcrystalline glass" are sometimes collectively referred to as "glass." Additionally, sometimes amorphous glass that becomes microcrystalline glass through heat treatment is referred to as "the matrix glass of microcrystalline glass."

[0051] In this specification, in the case of powder X-ray diffraction determination, for example using CuKα rays to measure the range of 2θ from 10° to 80°, the precipitated crystals are identified by the Hanawalt method when diffraction peaks appear. Furthermore, the crystal identified by this method is the main crystal from the peak group containing the highest integrated intensity. As the measuring apparatus, for example, the Smart Lab manufactured by Rigaku Corporation of Japan can be used.

[0052] In this specification, the concentrations of K, Na, or Li at a depth of x [μm] are measured in a cross-section along the thickness direction using an EPMA (electron probe microanalyzer). Specifically, the EPMA measurement is performed as follows, for example.

[0053] First, a glass sample was embedded in epoxy resin and mechanically ground along a direction perpendicular to the first principal surface and a second principal surface opposite to the first principal surface, thereby preparing a cross-sectional sample. A C-coating was applied to the ground section, and measurements were performed using an EPMA (manufactured by JEOL Corporation: JXA-8500F). With the accelerating voltage set to 15 kV, the probe current set to 30 nA, and the accumulation time set to 1000 ms / point, the spectral distribution of X-ray intensity for K, Na, or Li was obtained at 1 μm intervals.

[0054] In the following text, "chemically strengthened glass" refers to glass that has undergone chemical strengthening treatment, while "chemically strengthened glass" refers to glass before chemical strengthening treatment.

[0055] Unless otherwise specified, the glass composition in this specification is expressed in mol% based on oxides, and mol% is abbreviated as "%".

[0056] Furthermore, in this specification, "substantially not containing" means below the level of impurities contained in raw materials, etc., i.e., not intentionally added. Specifically, for example, less than 0.1%.

[0057] In this specification, "stress distribution" refers to a graph representing compressive stress values ​​using the depth measured from the glass surface as a variable. In the stress distribution, negative compressive stress represents tensile stress.

[0058] The compressive stress (CS) can be determined by thinning the cross-section of the glass and analyzing the thinned sample using a birefringence imaging system. A birefringence imaging system, specifically a birefringence stress meter, is a device that uses a polarizing microscope and a liquid crystal compensator to measure the magnitude of the delay caused by stress; for example, there is the Abrio-IM birefringence imaging system manufactured by Cri.

[0059] Alternatively, the stress can sometimes be measured using the photoelasticity of scattered light. In this method, light is incident from the surface of the glass, and the polarization of the scattered light is analyzed to determine the stress coefficient (CS). An example of a stress measuring instrument utilizing the photoelasticity of scattered light is the SLP-2000 photoelasticity stress gauge manufactured by Orihara Corporation.

[0060] In this specification, the “K ion penetration depth D” is obtained through the following operation steps (1) to (3).

[0061] (1) First, using the SLP-2000 light-scattering photoelastic stress meter manufactured by Orihara Manufacturing Co., Ltd. as described above, the distribution of compressive stress (CS) of chemically strengthened glass in the depth direction was measured.

[0062] (2) Next, for chemically strengthened glass with the same depth direction distribution as the compressive stress value measured in (1) using SLP-2000, the depth direction distribution is determined by the following method.

[0063] With one side of the glass sealed, it was immersed in an acid solution with a volume fraction of 1% HF to 99% H2O, and etching of arbitrary thickness was performed only on that side. This created a stress difference between the surface and back of the chemically strengthened glass, causing the glass to warp. The amount of warpage was measured using a contact shape measuring instrument (Mitutoyo Surftest). Warpage was measured at at least three points along the etching depth.

[0064] Based on the obtained warpage, the stress was converted using the formula shown in the following literature, thus obtaining the depth-direction distribution of the compressive stress value.

[0065] Reference: G. ...

[0066] (3) The two distributions obtained in operation steps (1) and (2) overlap, and the depth of the intersection point is "K ion invasion depth D".

[0067] In this etching process, warpage resulting from grinding using a rotary polisher (device name: 9B-5P, manufacturer: SPEEDFAM) can be measured using a contact shape measuring instrument (device name: SV-600, manufacturer: Mitutoyo). Especially when microcrystalline glass is used in this chemically strengthened glass, since the aforementioned acid etching process cannot be properly performed, it is preferable to use both a rotary polisher (device name: 9B-5P, manufacturer: SPEEDFAM) and a contact shape measuring instrument (device name: SV-600, manufacturer: Mitutoyo) to measure the amount of warpage.

[0068] In this specification, "compressive stress layer depth (DOL)" refers to the depth at which the compressive stress value is zero. Hereinafter, the surface compressive stress value may sometimes be denoted as CS0, and the compressive stress value at a depth of 50 μm from the surface may be denoted as CS. 50 Additionally, "internal tensile stress (CT)" refers to the tensile stress value at a depth of 1 / 2 the plate thickness t, and is distinguished from "CS" in this specification. t / 2 "Equivalent to".

[0069] In this specification, "transmittance" refers to the average transmittance of light with wavelengths from 380 nm to 780 nm. Additionally, "haze value" is measured using a halogen lamp (C light source) according to JIS K7136:2000.

[0070] In this specification, the “fracture toughness value” is the value obtained according to the IF method specified in JIS R1607:2015.

[0071] In this specification, "surface resistivity" is measured using a non-contact conductivity meter.

[0072] In this specification, the "#180 drop strength" and "#80 drop strength" are determined by the following method.

[0073] A glass sample measuring 120mm × 60mm × 0.6mm was embedded into a structure with its mass and rigidity adjusted to the size of a typical smartphone, thus preparing a simulated smartphone. The simulated smartphone was then dropped freely onto #180 SiC sandpaper with a drop strength of #180, or onto #80 SiC sandpaper with a drop strength of #80. For drop height, if the sample did not break after being dropped from a height of 5cm, the drop height was repeatedly increased by 5cm and dropped again until breakage occurred. The average value of the first breakage of 10 glass samples was measured.

[0074] The durability (10,000 cycles) of AFP in this specification is determined by an eraser abrasion test under the following conditions.

[0075] Rubber abrasion test conditions:

[0076] The chemically strengthened glass surface is cleaned with ultraviolet light, and OPTOOL (registered trademark) DSX (manufactured by Daikin) is sprayed onto the glass surface to form a basically uniform AFP film.

[0077] At 1cm 2 An eraser (manufactured by MIRAE SCIENCE, Minoan) was attached to the pressure head. Under a load of 1 kgf, the surface of the AFP membrane formed on the glass plate was rubbed reciprocally 10,000 times at a stroke width of 20 mm and a speed of 30 mm / s. The AFP membrane surface was then cleaned by wiping it dry with a cloth [manufactured by Ozu Sangyo, DUSPER (registered trademark)]. The water contact angle (°) was then measured at three points on the AFP membrane surface. This operation was repeated three times, and a total of nine average water contact angles (°) were measured. The water contact angle (°) of the AFP membrane surface was measured according to the method of JIS R3257 (1999).

[0078] In this specification, the “4PB strength” (4-point bending strength) is determined by the following method.

[0079] The 4PB strength can be evaluated by using 120mm×60mm strip test pieces and conducting a 4-point bending test under the conditions of a 30mm distance between the outer support points, a 10mm distance between the inner support points, and a crosshead speed of 5.0mm / min. For example, 10 test pieces can be used.

[0080] Chemically strengthened glass

[0081] The chemically strengthened glass of the present invention (hereinafter referred to as the chemically strengthened glass) is typically a plate-shaped glass article, which can be flat or curved. In addition, it can have sections with different thicknesses.

[0082] The thickness (t) of this chemically strengthened glass in the case 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, and 700 μm or less. Furthermore, in order to obtain sufficient strength through chemical strengthening treatment, this thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and even more preferably 500 μm or more.

[0083] <<Implementation Method 1>>

[0084] Embodiment 1 of this chemically strengthened glass is a chemically strengthened glass with a thickness of t [μm]. The K₂O concentration at a depth x [μm] from the surface, expressed as a molar percentage based on oxides, is denoted as K.x [%), Let the content of K2O before chemical fortification be K t / 2 When [%], K x For (K) t / 2 The maximum depth z of +0.1% [%) is 0.5 μm to 5 μm. z is preferably 0.6 μm to 4.5 μm, more preferably 0.7 μm to 4 μm, even more preferably 0.8 μm to 3.5 μm, and particularly preferably 0.85 μm to 3 μm. With a depth z of 0.5 μm to 5 μm, the increase in surface resistivity caused by the alkali mixing effect can be suppressed.

[0085] The composition of the glass before chemical strengthening is the same as that at the center of the glass thickness (the central part of the glass). Specifically, when the thickness of this chemically strengthened glass is t, the contents of Li2O, Na2O, and K2O before chemical strengthening are the same as those at position t / 2.

[0086] In Embodiment 1 of this chemically strengthened glass, the K₂O concentration at a depth x [μm] from the surface is defined as K₂O, based on the molar percentage of oxides. x [%), Let the content of K2O before chemical fortification be K t / 2 When [%], K x For (K) t / 2 The Na₂O concentration at the maximum depth z [μm] above +0.1)[%] is set as Na z [%], The Na₂O concentration at a depth of 50 μm from the surface is set as Na. 50 [%], |Na z -Na 50 |Preferred concentration is less than 3%. |Na z -Na 50 |More preferably, it is 2.5% or less, and even more preferably, it is 2% or less.

[0087] In chemically strengthened glass, the Na concentration typically increases from the center of the glass towards the surface, but through |Na z -Na 50 With sodium concentrations less than 3%, the distribution of sodium concentration in the glass becomes flatter, and compared to conventional chemically strengthened glass, the alkali mixing degree is lower, which more effectively suppresses the increase in surface resistivity. Regarding |Na z -Na 50 There is no particular limit to the lower limit, but it is typically above 0.1%.

[0088] In Embodiment 1 of this chemically strengthened glass, the Na₂O concentration at a depth of 50 μm from the surface is defined as Na, based on the molar percentage of oxides. 50 [%], Set the Na2O content before chemical fortification as Nat / 2 [%], Na 50 Preferred size is less than (Na) t / 2 +7)% Na 50 More preferably (Na) t / 2 (+5.5%) or less, more preferably (Na) t / 2 +4)% or less.

[0089] Through Na 50 Less than (Na) t / 2 +7)%, the alkali mixing degree on the glass surface decreases, which can more effectively suppress the increase in surface resistivity. Regarding Na... 50 There is no particular limitation on the lower limit, but in order to maintain a balance with the suppression of glass fracture caused by compressive stress, it is preferable to (Na) t / 2 +2)% or more.

[0090] In Embodiment 1 of this chemically strengthened glass, the K2O concentration at a depth of 1 μm from the surface is defined as K1% (based on oxide molar percentage), the Na2O concentration at a depth of 1 μm from the surface is defined as Na1% (based on oxide molar percentage), and the contents of Li2O, Na2O, and K2O before chemical strengthening are defined as Li... t / 2 [%], Na t / 2 [%] and K t / 2 When [%], [(Li t / 2 +Na t / 2 +K t / 2 [(Li)-2(Na1+K1)] preferably greater than 0%. t / 2 +Na t / 2 +K t / 2 The content of ]-2(Na1+K1) is more preferably 3% or more, and even more preferably 5% or more.

[0091] Through [(Li t / 2 +Na t / 2 +K t / 2 When [(Li)-2(Na1+K1)] is greater than 0%, the alkali mixing degree on the glass surface decreases, which can more effectively suppress the increase in surface resistivity. t / 2 +Na t / 2 +K t / 2 There is no particular upper limit to the content of [ )-2(Na1+K1)], but it is typically preferred to be below 15%.

[0092] In Embodiment 1 of this chemically strengthened glass, with a plate thickness of t, Na... z -Na t / 2 Preferably, it is 8% or less, more preferably 7% or less, and even more preferably 6% or less. (By Na) z -Na t / 2When the concentration is below 8%, the alkali mixing degree on the glass surface decreases, which can more effectively suppress the increase in surface resistivity. For Na... z -Na t / 2 There is no particular limitation on the lower limit, but it is typically preferred to be 2% or higher.

[0093] In one embodiment of this chemically strengthened glass, the Na ion distribution is as follows: Figure 1 As shown in (a) and (b), the K ion distribution is as follows Figure 1 As shown in (c) and (d). Figure 1 As shown in (a) and (b), through chemical strengthening, the amount of Li ions in the glass exchanged with Na ions in the molten salt is small, and the Na ion distribution along the thickness direction of the plate is flat. Additionally, as... Figure 1 As shown in (c) and (d), due to the small amount of Na ion exchange, chemical strengthening by using a molten salt containing K results in the exchange of Na ions with K ions only occurring in the very shallow surface layer of the glass. The layer in which K ions are present is very thin, resulting in a chemically strengthened glass with reduced alkali mixing.

[0094] The stress distribution in one embodiment of this chemically strengthened glass is as follows: Figure 2 As shown in Example 1. Figure 2 As shown, this chemically strengthened glass has a low alkali mixing degree at the glass surface, and at the same time, the compressive stress at the glass surface is higher than that of conventional chemically strengthened glass, exhibiting excellent strength.

[0095] When the surface compressive stress (CS0) of this chemically strengthened glass is 450 MPa or higher, it is less prone to breakage due to deformation such as bending, and is therefore preferred. CS0 is more preferably 500 MPa or higher, and even more preferably 600 MPa or higher. A higher CS0 results in higher strength, but if CS0 is too high, violent breakage may occur upon fracture. Therefore, CS0 is preferably 1100 MPa or lower, and more preferably 900 MPa or lower.

[0096] The compressive stress (CS) value at a depth of 50 μm from the surface of this chemically strengthened glass. 50 When the pressure is 150 MPa or higher, it easily prevents the chemically strengthened glass from breaking when dropped from a height, such as in portable devices using this chemically strengthened glass as protective glass. Therefore, it is preferred. 50 More preferably, it is 180 MPa or higher, and even more preferably, it is 200 MPa or higher. CS 50 The larger the value, the higher the strength, but in CS... 50 In cases where the size is too large, violent fragmentation may occur upon rupture, therefore CS 50 Preferably, the pressure is 300 MPa or less, and more preferably 270 MPa or less.

[0097] The compressive stress CS of this chemically strengthened glass at a depth of 50 μm from the surface. 50 Divided by (Na 50 -Na t / 2 The obtained value CS 50 / (Na 50 -Na t / 2 Preferably, the pressure is 50 MPa / % or higher, more preferably 55 MPa / % or higher, and even more preferably 60 MPa / % or higher. (Surveyed via CS) 50 / (Na 50 -Na t / 2 With a strength of over 50 MPa, it exhibits excellent strength. CS 50 / (Na 50 -Na t / 2 The larger the value, the more it can increase the strength with less ion exchange without increasing the surface resistivity, but in CS... 50 / (Na 50 -Na t / 2 If the value is too high, it may be susceptible to the deterioration caused by the fortified salt, therefore CS 50 / (Na 50 -Na t / 2 Preferably, the pressure is 400 MPa / % or less, more preferably 300 MPa / % or less. Na 50 Na₂O concentration [%] at a depth of 50 μm from the surface, expressed as a molar percentage based on oxides. t / 2 The content of Na2O before chemical fortification, expressed as a molar percentage based on oxides [%).

[0098] The compressive stress CS of this chemically strengthened glass at a depth of 90 μm from the surface. 90 When the pressure is 30 MPa or higher, this chemically strengthened glass is preferred to prevent breakage when portable devices using this chemically strengthened glass as a protective glass fall onto coarse sand or similar surfaces. CS 90 More preferably, it is 50 MPa or higher, and even more preferably 70 MPa or higher. CS 90 The larger the value, the higher the strength, but in CS... 90 In cases where the size is too large, violent fragmentation may occur upon rupture, therefore CS 90 Preferably, the pressure is 170 MPa or less, and more preferably 150 MPa or less.

[0099] With the plate thickness set as t, the compressive stress CS of this chemically strengthened glass at a depth of t / 2 from the surface is... t / 2 Preferably, it is -120 MPa or higher, more preferably -115 MPa or higher, and even more preferably -110 MPa or higher. (By CS) t / 2is -120 MPa or more, which can prevent explosive rupture when the glass is damaged. In addition, for CS t / 2 there is no particular limitation on the upper limit, but in order to maintain sufficient compressive stress, it is usually preferably -80 MPa or less.

[0100] When the DOL of this chemically strengthened glass is 90 μm or more, even if damage occurs on the surface, it is not easily broken, so it is preferable. The DOL is more preferably 95 μm or more, further preferably 100 μm or more, and particularly preferably 110 μm or more. The larger the DOL, the less likely it is to break even if damage occurs. However, in chemically strengthened glass, since tensile stress is generated inside corresponding to the compressive stress formed near the surface, the DOL cannot be extremely increased. In the case of a thickness of t, the DOL is preferably t / 4 or less, more preferably t / 5 or less. In order to shorten the time required for chemical strengthening, the DOL is preferably 200 μm or less, more preferably 180 μm or less.

[0101] Since the stress value is reduced due to the deterioration of the strengthening salt, the CS 50 [[ID=1 (repeated)]] t / 2 and CS 90 are each preferably 70% or more of the initial strengthening value. That is, it is preferable that: the surface compressive stress value CS0 is 450 MPa or more, and the compressive stress value CS 50 at a depth of 50 μm from the surface is y = 124.7×t + 21.5 [MPa] or more, and the compressive stress value CS<000015!>at a depth of 90 μm from the surface is y = 99.1×t - 38.3 [MPa] or more.

[0102] When the surface layer slope P at the glass surface layer defined by the formula CS0 / D is -1000 MPa / μm < P0 < -225 MPa / μm, the result of the 4PB strength (MPa) test of this chemically strengthened glass is greater than 550 MPa, so it is preferable. In the above formula, CS0 is the surface compressive stress value (MPa), and D is the K ion penetration depth (μm).

[0103] In addition, when the slope of the stress distribution of the chemically strengthened glass in the region between a depth of 50 μm from the surface and a depth of 90 μm from the surface is set to P 50-90 (MPa / μm), and the slope of the stress distribution of the chemically strengthened glass in the region between a depth of 90 μm from the surface and the depth (DOL) (μm) where the compressive stress value is zero is set to P 90-DOL (MPa / μm), it is preferable that |P 50-90 | > |P 90-DOL |, 1.8 < |P 50-90 | < 6.0 and 1.5 < |P 90-DOL|<4.0. As a more preferred approach, we can list: |P 50-90 |>|P 90-DOL |、1.8<|P 50-90 |<6.0 and 1.5<|P 90-DOL |<4.0, #180 drop strength of 100cm or more.

[0104] P 50-90 and P 90-DOL The results are obtained using the following formulas.

[0105] P 50-90 =(CS 50 -CS 90 ) / 40

[0106] P 90-DOL =CS 90 / (DOL-90)

[0107] Furthermore, the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 50 μm measured from the surface and a depth of 90 μm measured from the surface is denoted as P. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm from the surface and a depth (DOL) (μm) where the compressive stress is zero. 90-DOL Under the condition of (MPa / μm), |P is preferred. 50-90 |<|P 90-DOL |、1.0<|P 50-90 |<3.0 and 1.2<|P 90-DOL |<4.0. As a more preferred approach, |P is preferred. 50-90 |<|P 90-DOL |、1.0<|P 50-90 |<3.0 and 1.2<|P 90-DOL |<4.0, #80 drop strength is over 40cm.

[0108] In this embodiment 1, the preferred range for the thickness t of the chemically strengthened glass is 300 μm to 1500 μm.

[0109] <<Implementation Method 2>>

[0110] Embodiment 2 of this chemically strengthened glass is a chemically strengthened glass in which the K ion penetration depth D is 0.5 μm to 5 μm, and the compressive stress value at depth D is equal to the compressive stress value CS at a depth of 50 μm measured from the surface. 50The absolute value of the difference is less than 150 MPa, the compressive stress value at the K ion penetration depth D is less than 350 MPa, the surface compressive stress value CS0 is greater than 450 MPa, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is above 150 MPa at a depth of 90 μm from the surface. 90 It is above 30MPa.

[0111] In Embodiment 2 of this chemically strengthened glass, by having a K ion penetration depth D of 0.5 μm to 5 μm, the alkali mixing degree of the glass surface is reduced, thereby suppressing the increase in surface resistivity. D is preferably 0.7 μm to 4 μm, and more preferably 0.8 to 3 μm.

[0112] In Embodiment 2 of this chemically strengthened glass, the compressive stress value at the K ion penetration depth D and the compressive stress value CS at a depth of 50 μm measured from the surface are compared. 50 The absolute value of the difference is less than 150 MPa, which can suppress cracking caused by deformation such as flexure. The compressive stress value at the K ion penetration depth D and the compressive stress value CS at a depth of 50 μm measured from the surface are... 50 The absolute value of the difference is preferably 130 MPa or less, more preferably 110 MPa or less. The compressive stress value at depth D and the compressive stress value CS at a depth of 50 μm measured from the surface are compared. 50 There is no particular restriction on the lower limit of the absolute value of the difference.

[0113] In Embodiment 2 of this chemically strengthened glass, the compressive stress value at the K ion penetration depth D is 350 MPa or less, which sufficiently improves the CS. 50 or CS 90 Without excessively increasing the CT (coulombic stress). The compressive stress value at the K ion penetration depth D is preferably 330 MPa or less, more preferably 300 MPa or less. There is no particular limitation on the lower limit of the compressive stress value at the K ion penetration depth D, but from the viewpoint of suppressing cracks near the surface, it is preferably 100 MPa or more.

[0114] <<Surface Resistance>>

[0115] The surface resistivity logρ of this chemically strengthened glass is preferably 12 Ω·cm or less, more preferably 11.5 Ω·cm or less, and even more preferably 11 Ω·cm or less. With a surface resistivity logρ of 12 Ω·cm or less, peeling of the coating film can be suppressed. There is no particular limitation on the lower limit of the surface resistivity logρ, which is typically 8 Ω·cm or more.

[0116] <<Drop Strength>>

[0117] The #180 drop strength of this chemically strengthened glass is preferably 100 cm or more, more preferably 140 cm or more, and further preferably 180 cm or more. By having the #180 drop strength of 100 cm or more, it is possible to suppress the breakage of the chemically strengthened glass when a portable terminal or the like having this chemically strengthened glass as a protective glass falls from a height onto sand or the like. There is no particular limitation on the upper limit of the #180 drop strength, and typically it is 300 cm or less.

[0118] The #80 drop strength of this chemically strengthened glass is preferably 40 cm or more, more preferably 50 cm or more, and further preferably 60 cm or more. By having the #80 drop strength of 40 cm or more, it is possible to suppress the breakage of the chemically strengthened glass when a portable terminal or the like having this chemically strengthened glass as a protective glass falls from a height onto coarse sand or the like. There is no particular limitation on the upper limit of the #80 drop strength, and typically it is 150 cm or less.

[0119] In this Embodiment 2, the preferred range of the plate thickness t of this chemically strengthened glass is 300 μm to 1500 μm.

[0120] <<AFP Durability>>

[0121] The AFP durability (10,000 times) of this chemically strengthened glass is preferably 100 degrees or more, more preferably 105 degrees or more, and further preferably 110 degrees or more. By having the AFP durability (10,000 times) of 100 degrees or more, it is possible to suppress the peeling of the coating film. There is no particular limitation on the upper limit of the AFP durability (10,000 times), and typically it is 125 degrees or less.

[0122] <<Uses>>

[0123] This chemically strengthened glass is useful as a protective glass used in electronic devices such as mobile devices such as mobile phones and smartphones. In addition, it is also useful for protective glasses of electronic devices such as televisions, personal computers, and touch panels that are not for the purpose of portability, elevator wall surfaces, and wall surfaces (full-screen displays) of buildings such as houses and buildings. Further, it is useful as building materials such as window glass, table tops, interior decorations of automobiles or airplanes, etc. or their protective glasses, and also in casings having a curved shape.

[0124] The ion distribution and stress characteristics of this chemically strengthened glass can be adjusted by the basic composition of this chemically strengthened glass and the conditions of the chemical strengthening treatment. From the viewpoint of improving the stress characteristics of this chemically strengthened glass, this chemically strengthened glass is preferably a glass-ceramic. The basic composition and glass-ceramic of this chemically strengthened glass will be described below.

[0125] <<Basic Composition of this Chemically Strengthened Glass>>

[0126] The basic composition of this chemically strengthened glass preferably contains SiO2, Li2O, and Al2O3. Based on the mole percent of oxides, the basic composition of this chemically strengthened glass preferably contains:

[0127] 40%–75% SiO2,

[0128] 5%–35% Li2O,

[0129] 1% to 20% Al2O3.

[0130] Furthermore, based on oxides as a mole percent, the basic composition of this chemically strengthened glass more preferably contains:

[0131] 40%–70% SiO2,

[0132] 5%–35% Li2O,

[0133] 1% to 20% Al2O3.

[0134] Furthermore, based on oxides as a mole percent, the basic composition of this chemically strengthened glass is further preferably composed of:

[0135] 50%–70% SiO2,

[0136] 10%–30% Li₂O,

[0137] 1%–15% Al2O3,

[0138] 0%–5% P2O5,

[0139] 0%–8% ZrO2,

[0140] 0%–10% MgO,

[0141] 0%–5% Y2O3,

[0142] 0%–10% B2O3

[0143] 0%–5% Na2O,

[0144] 0%–5% K2O,

[0145] 0% to 2% SnO2.

[0146] Specifically, the glass types (i) to (iii) below are preferred.

[0147] (i) Glass containing 61.0% SiO2, 21.0% Li2O, 5.0% Al2O3, 2.0% Na2O, 2.0% P2O5, 3.0% ZrO2, 5.0% MgO and 1.0% Y2O3.

[0148] (ii) Glass containing 51.2% SiO2, 34.1% Li2O, 5.0% Al2O3, 1.8% Na2O, 2.3% P2O5, 4.5% ZrO2 and 1.0% Y2O3.

[0149] (iii) A glass containing 54.0% SiO2, 30.9% Li2O, 5.4% Al2O3, 1.7% Na2O, 1.2% K2O, 1.9% P2O5, 3.9% ZrO2 and 0.7% Y2O3.

[0150] In addition, it may contain impurities such as Sb2O3 and HfO2 as trace components.

[0151] Here, "the basic composition of chemically strengthened glass" refers to the composition of the glass-ceramic before chemical strengthening. This composition will be described later. Except in cases of extreme ion exchange treatment, the composition of this chemically strengthened glass is generally similar to that of the glass-ceramic before strengthening; typically, the composition of the glass-ceramic before strengthening is equivalent to the composition at the center of the thickness of the chemically strengthened glass. In particular, except in cases of extreme ion exchange treatment, the composition of the deepest part from the glass surface is the same as that of the glass-ceramic before strengthening.

[0152] Microcrystalline Glass

[0153] From the viewpoint of improving strength, this chemically strengthened glass preferably includes microcrystalline glass (hereinafter referred to as this microcrystalline glass). Compared with amorphous glass, microcrystalline glass has superior strength, so even when the alkali mixing degree of the glass surface is lower than that of conventional chemically strengthened glass, it is easy to form a preferred stress distribution, and it is easy to balance the strength and surface properties of the glass.

[0154] Examples of crystals that can be incorporated into glass-ceramics include lithium phosphate crystals, lithium metasilicate crystals, and β-spodumene crystals. From the viewpoint of increasing strength, lithium phosphate crystals and lithium metasilicate crystals are preferred. Furthermore, the crystals contained in the glass-ceramics can be solid solution crystals. By containing these crystals, strength is increased, light transmittance is increased, and haze is reduced.

[0155] Li3PO4 and Li4SiO4 crystals have similar crystal structures, making them sometimes difficult to distinguish using powder X-ray diffraction (PXRD). Specifically, PXRD measurements show diffraction peaks around 2θ = 16.9°, 22.3°, 23.1°, and 33.9°. Due to factors such as small crystal amounts and oriented crystals, it is sometimes impossible to identify low-intensity peaks or peaks on specific crystal planes. Furthermore, in cases where both crystals are in solid solution, the 2θ peak position may shift by approximately 1°.

[0156] When measuring X-ray diffraction in the range of 2θ = 10° to 80°, the strongest diffraction peak of this microcrystalline glass preferably appears at 22.3° ± 0.2° or 23.1 ± 0.2°.

[0157] To improve mechanical strength, the crystallinity of this microcrystalline glass is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, and particularly preferably 20% or more. To improve transparency, the crystallinity is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. A low crystallinity is also advantageous in terms of ease of bending and shaping by heating.

[0158] To improve strength, the average particle size of the precipitated crystals in this glass-ceramic is preferably 5 nm or more, particularly preferably 10 nm or more. To improve transparency, the average particle size is preferably 80 nm or less, more preferably 60 nm or less, further preferably 50 nm or less, particularly preferably 40 nm or less, and most preferably 30 nm or less. The average particle size of the precipitated crystals can be determined from transmission electron microscopy (TEM) images.

[0159] When the glass-ceramic is in plate form, its thickness (t) is preferably 3000 μm or less, more preferably 2000 μm or less, 1600 μm or less, 1100 μm or less, 900 μm or less, 800 μm or less, and 700 μm or less. Furthermore, in order to obtain sufficient strength through chemical strengthening treatment, this thickness (t) is preferably 300 μm or more, more preferably 400 μm or more, and even more preferably 500 μm or more.

[0160] With a thickness of 700 μm, this microcrystalline glass has a light transmittance of 85% or more, thus making the display screen easily visible when used as protective glass for mobile phone displays. The light transmittance is preferably 88% or more, more preferably 90% or more. Higher light transmittance is preferred, but it is typically below 91%. With a thickness of 700 μm, 90% light transmittance is equivalent to that of ordinary amorphous glass.

[0161] It should be noted that if the actual thickness is not 700μm, the transmittance at 700μm can be calculated based on the measured value using the Lambert-Beer law. Alternatively, if the plate thickness t is greater than 700μm, the thickness can be adjusted to 700μm through grinding, etching, or other methods before measurement.

[0162] Furthermore, when the thickness is 700 μm, the haze value is 0.5% or less, preferably 0.4% or less, more preferably 0.3% or less, even more preferably 0.2% or less, and particularly preferably 0.15% or less. A lower haze value is preferred, but it is typically 0.01% or more. With a thickness of 700 μm, a haze value of 0.02% is equivalent to that of ordinary amorphous glass.

[0163] It should be noted that when the total visible light transmittance (total visible light transmittance) of a microcrystalline glass with a thickness of t [μm] is 100×T [%) and the haze value is 100×H [%), it can be expressed as T=(1-R) ​​by referring to the Lambert-Beer law and using the constant α. 2 ×exp(-αt). Using the constant α, we get dH / dt∝exp(-αt)×(1-H).

[0164] That is, it is assumed that the haze value increases proportionally to the internal linear transmittance with increasing plate thickness. Therefore, the haze value H at 700 μm is... 0.7 It can be obtained from the following formula.

[0165]

[0166] In addition, when the plate thickness t is greater than 700 μm, the plate thickness can be adjusted to 700 μm by grinding, etching, etc., before measurement.

[0167] This microcrystalline glass exhibits high fracture toughness, and even with large compressive stresses induced by chemical strengthening, it is not prone to severe fracture. The preferred fracture toughness of this microcrystalline glass is 0.81 MPa·m. 1 / 2 The above is more preferably 0.84 MPa·m 1 / 2 The above is further preferably 0.87 MPa·m 1 / 2 When the above conditions are met, glass with high impact resistance can be obtained. There is no particular upper limit to the fracture toughness value of this microcrystalline glass, typically 1.5 MPa·m. 1 / 2 the following.

[0168] To suppress warping during chemical strengthening treatment, the Young's modulus of this glass-ceramic is preferably 80 GPa or higher, more preferably 85 GPa or higher, even more preferably 90 GPa or higher, and particularly preferably 95 GPa or higher. This glass-ceramic is sometimes used after grinding. For ease of grinding, the Young's modulus is preferably 130 GPa or lower, more preferably 120 GPa or lower, and even more preferably 110 GPa or lower.

[0169] This microcrystalline glass is obtained by heating and crystallizing an amorphous glass, which will be described later.

[0170] <<Composition of Glass-Crystals>>

[0171] This glass-ceramic preferably contains SiO2, Li2O, and Al2O3. Based on the mole percent of oxides, this glass-ceramic preferably contains:

[0172] 40%–75% SiO2,

[0173] 5%–35% Li2O,

[0174] 1% to 20% Al2O3.

[0175] Furthermore, based on oxides as a mole percent, this glass-ceramic more preferably contains:

[0176] 40%–70% SiO2,

[0177] 5%–35% Li2O,

[0178] 1% to 20% Al2O3.

[0179] Furthermore, based on oxides as a mole percent, this glass-ceramic preferably contains:

[0180] 50%–70% SiO2,

[0181] 10%–30% Li₂O,

[0182] 1%–15% Al2O3,

[0183] 0%–5% P2O5,

[0184] 0%–8% ZrO2,

[0185] 0%–10% MgO,

[0186] 0%–5% Y2O3,

[0187] 0%–10% B2O3

[0188] 0%–5% Na2O,

[0189] 0%–5% K2O,

[0190] 0% to 2% SnO2.

[0191] Specifically, the glass types (i) to (iii) below are preferred.

[0192] (i) Glass containing 61.0% SiO2, 21.0% Li2O, 5.0% Al2O3, 2.0% Na2O, 2.0% P2O5, 3.0% ZrO2, 5.0% MgO and 1.0% Y2O3.

[0193] (ii) Glass containing 51.2% SiO2, 34.1% Li2O, 5.0% Al2O3, 1.8% Na2O, 2.3% P2O5, 4.5% ZrO2 and 1.0% Y2O3.

[0194] (iii) A glass containing 54.0% SiO2, 30.9% Li2O, 5.4% Al2O3, 1.7% Na2O, 1.2% K2O, 1.9% P2O5, 3.9% ZrO2 and 0.7% Y2O3.

[0195] In addition, it may contain impurities such as Sb2O3 and HfO2 as trace components.

[0196] The total amount of SiO2, Al2O3, P2O5, and B2O3 in this glass-ceramic, based on oxide mol%, is preferably 60% to 80%. SiO2, Al2O3, P2O5, and B2O3 are the network-forming components of the glass (hereinafter also simply referred to as NWF). A higher total amount of these NWFs increases the strength of the glass. This increases the fracture toughness of the glass-ceramic; therefore, the total amount of NWF is preferably 60% or more, more preferably 63% or more, and particularly preferably 65% ​​or more. However, glass with excessive NWF is difficult to manufacture due to higher melting temperatures, therefore the total amount of NWF is preferably 85% or less, more preferably 80% or less, and even more preferably 75% or less.

[0197] The ratio of the total amount of Li2O, Na2O and K2O in this microcrystalline glass to the total amount of NWF, namely SiO2, Al2O3, P2O5 and B2O3, is preferably 0.20 to 0.60.

[0198] Li₂O, Na₂O, and K₂O are network modification components. Reducing their ratio relative to NWF increases the gaps in the network, thereby improving impact resistance. Therefore, the total amount of Li₂O, Na₂O, and K₂O relative to NWF is preferably 0.60 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less. On the other hand, since these are essential components for chemical strengthening, in order to improve chemical strengthening properties, the total amount of Li₂O, Na₂O, and K₂O relative to NWF is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.30 or more.

[0199] The composition of this microcrystalline glass will be described below.

[0200] In this glass-ceramic, SiO2 is a component that forms the network structure of the glass. Furthermore, SiO2 is a component that improves chemical durability, and its content is preferably 40% or more. More preferably, the SiO2 content is 48% or more, even more preferably 50% or more, particularly preferably 52% or more, and extremely preferably 54% or more. On the other hand, to improve melt flowability, the SiO2 content is preferably 75% or less, more preferably 70% or less, even more preferably 68% or less, even more preferably 66% or less, and particularly preferably 64% or less.

[0201] Li₂O is a component that forms surface compressive stress through ion exchange and is an essential component of the main crystal. The content of Li₂O is preferably 5% or more, more preferably 8% or more, more preferably 11% or more, even more preferably 15% or more, particularly preferably 20% or more, and most preferably 22% or more. On the other hand, for the purpose of glass stability, the content of Li₂O is preferably 35% or less, more preferably 32% or less, even more preferably 30% or less, particularly preferably 28% or less, and most preferably 26% or less.

[0202] Al2O3 is an essential component that increases surface compressive stress through chemical strengthening. The content of Al2O3 is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, 5% or more, 5.5% or more, 6% or more, particularly preferably 6.5% or more, and most preferably 7% or more. On the other hand, to prevent the devitrification temperature of the glass from becoming too high, the content of Al2O3 is preferably 20% or less, more preferably 15% or less, further preferably 12% or less, particularly preferably 10% or less, and most preferably 9% or less.

[0203] P2O5 is a constituent component of Li3PO4 crystals and is essential for the precipitation of these crystals. In this case, to promote crystallization, the content of P2O5 is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, particularly preferably 2% or more, and extremely preferably 2.5% or more. On the other hand, if the P2O5 content is too high, phase separation is easy during melting, and the acid resistance decreases significantly. Therefore, the P2O5 content is preferably 5% or less, more preferably 4.8% or less, even more preferably 4.5% or less, and particularly preferably 4.2% or less.

[0204] ZrO2 is a component that improves mechanical strength and chemical durability. To significantly improve CS (chemical stability), it is preferable to contain ZrO2. The ZrO2 content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. On the other hand, to suppress devitrification during melting, ZrO2 is preferably 8% or less, more preferably 7.5% or less, and particularly preferably 6% or less. Excessive ZrO2 content leads to a decrease in viscosity due to an increase in devitrification temperature. To suppress this viscosity decrease and resulting in poor moldability, when the molding viscosity is low, the ZrO2 content is preferably 5% or less, more preferably 4.5% or less, and further preferably 3.5% or less.

[0205] MgO is a component that stabilizes glass and also improves its mechanical strength and chemical resistance. Therefore, it is preferable to contain MgO when the Al2O3 content is relatively low. The MgO content is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, and particularly preferably 4% or more. On the other hand, when excessive MgO is added, the viscosity of the glass decreases, which can easily cause devitrification or phase separation. Therefore, the MgO content is preferably 10% or less, more preferably 9% or less, further preferably 8% or less, and particularly preferably 7% or less.

[0206] Y₂O₃ is a component that prevents chemically strengthened glass from scattering when it breaks, and may contain Y₂O₃. The content of Y₂O₃ is preferably 1% or more, more preferably 1.5% or more, further preferably 2% or more, particularly preferably 2.5% or more, and extremely preferably 3% or more. On the other hand, in order to suppress devitrification during melting, the content of Y₂O₃ is preferably 5% or less, more preferably 4% or less.

[0207] B2O3 is a component that improves the resistance to edge chipping and the melt flow properties of chemically strengthened glass, and may contain B2O3. To improve melt flow properties, the content of B2O3 is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more. On the other hand, if the content of B2O3 is too high, it can cause ripples or phase separation during melting, which can easily reduce the quality of the chemically strengthened glass. Therefore, the content of B2O3 is preferably 10% or less. The content of B2O3 is more preferably 8% or less, even more preferably 6% or less, and particularly preferably 4% or less.

[0208] Na₂O is a component that improves the melting properties of glass. While not essential, when Na₂O is present, its content is preferably 0.5% or more, more preferably 1% or more, and particularly preferably 2% or more. Excessive Na₂O can hinder the precipitation of crystals such as Li₃PO₄, which serve as the main crystals, or reduce chemical strengthening properties. Therefore, the Na₂O content is preferably 5% or less, more preferably 4.5% or less, further preferably 4% or less, and particularly preferably 3.5% or less.

[0209] Like Na2O, K2O is a component that lowers the melting temperature of glass and can be present. When K2O is present, its content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. Excessive K2O reduces chemical strengthening properties or chemical durability; therefore, the K2O content is preferably 5% or less, more preferably 4% or less, further preferably 3.5% or less, particularly preferably 3% or less, and most preferably 2.5% or less.

[0210] To improve the meltability of the glass raw material, the total content of Na2O and K2O (Na2O+K2O) is preferably 1% or more, and more preferably 2% or more.

[0211] Furthermore, when the K2O content relative to the total content of Li2O, Na2O, and K2O (hereinafter referred to as R2O) is 0.2 or less, the chemical strengthening properties and chemical durability can be improved, and therefore this is preferred. The K2O / R2O ratio is more preferably 0.15 or less, and even more preferably 0.10 or less.

[0212] It should be noted that the R2O content is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. Furthermore, the R2O content is preferably 29% or less, more preferably 26% or less.

[0213] Furthermore, to improve chemical durability, the ZrO2 / R2O ratio is preferably 0.02 or higher, more preferably 0.03 or higher, even more preferably 0.04 or higher, particularly preferably 0.1 or higher, and most preferably 0.15 or higher. To improve transparency after crystallization, the ZrO2 / R2O ratio is preferably 0.6 or lower, more preferably 0.5 or lower, even more preferably 0.4 or lower, and particularly preferably 0.3 or lower.

[0214] SnO2 plays a role in promoting crystal nucleation and may be present in the material. SnO2 is not essential, but when present, its content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, to suppress devitrification during melting, the SnO2 content is preferably 5% or less, more preferably 4% or less, further preferably 3.5% or less, and particularly preferably 3% or less.

[0215] TiO2 is a component that promotes crystallization and may be present. TiO2 is not essential, but when TiO2 is present, its content is preferably 0.2% or more, more preferably 0.5% or more. On the other hand, in order to suppress devitrification during melting, the content of TiO2 is preferably 4% or less, more preferably 2% or less, and even more preferably 1% or less.

[0216] BaO, SrO, MgO, CaO, and ZnO are all components that improve the melt flowability of glass, and these components may be included. When these components are included, the total content of BaO, SrO, MgO, CaO, and ZnO (hereinafter referred to as BaO+SrO+MgO+CaO+ZnO) is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, since the ion exchange rate decreases, BaO+SrO+MgO+CaO+ZnO is preferably 8% or less, more preferably 6% or less, even more preferably 5% or less, and particularly preferably 4% or less.

[0217] BaO, SrO, and ZnO increase the refractive index of the residual glass, making it closer to the precipitated crystalline phase, thereby improving the light transmittance of the glass-ceramic and reducing the haze value. Therefore, BaO, SrO, and ZnO can be included. In this case, the total content of BaO, SrO, and ZnO (hereinafter referred to as BaO+SrO+ZnO) is preferably 0.3% or more, more preferably 0.5% or more, even more preferably 0.7% or more, and particularly preferably 1% or more. On the other hand, these components sometimes reduce the ion exchange rate. To improve the chemical strengthening properties, BaO+SrO+ZnO is preferably 2.5% or less, more preferably 2% or less, even more preferably 1.7% or less, and particularly preferably 1.5% or less.

[0218] La₂O₃, Nb₂O₅, and Ta₂O₅ are all components that prevent chemically strengthened glass from scattering when it breaks. These components can be included to increase the refractive index. When these components are included, the total content of La₂O₃, Nb₂O₅, and Ta₂O₅ (hereinafter referred to as La₂O₃+Nb₂O₅+Ta₂O₅) is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. Furthermore, to prevent the glass from devitrifying during melting, La₂O₃+Nb₂O₅+Ta₂O₅ is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less.

[0219] Additionally, CeO2 may be present. CeO2 sometimes suppresses coloration by oxidizing the glass. When CeO2 is present, its content is preferably 0.03% or more, more preferably 0.05% or more, and even more preferably 0.07% or more. To improve transparency, the CeO2 content is preferably 1.5% or less, more preferably 1.0% or less.

[0220] When using this chemically strengthened glass with coloring, coloring components can be added within a range that does not hinder the achievement of the desired chemical strengthening properties. Examples of coloring components include: Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, Er2O3, and Nd2O3.

[0221] The total content of coloring components is preferably below 1%. If it is desired to further improve the visible light transmittance of the glass, it is preferable that these components are substantially absent.

[0222] In addition, SO3, chlorides, and fluorides may be appropriately contained as clarifying agents during glass melting. It is preferable that As2O3 is not contained. When Sb2O3 is present, the Sb2O3 content is preferably 0.3% or less, more preferably 0.1% or less, and most preferably Sb2O3 is not contained.

[0223] <Manufacturing Methods of Chemically Strengthened Glass>

[0224] The chemically strengthened glass of the present invention is manufactured by chemically strengthening the aforementioned microcrystalline glass. This microcrystalline glass is manufactured by crystallizing an amorphous glass of the same composition through heat treatment.

[0225] (Manufacturing of amorphous glass)

[0226] Amorphous glass can be manufactured, for example, by the following methods. It should be noted that the manufacturing methods described below are examples of manufacturing sheet-shaped chemically strengthened glass.

[0227] Glass raw materials are prepared in a manner that yields glass with an optimal composition and then heated and melted in a glass melting furnace. The molten glass is then homogenized by bubbling, stirring, and adding clarifying agents, and formed into glass sheets of a specified thickness using a known forming method, followed by slow cooling. Alternatively, the molten glass can be formed into sheets by shaping it into blocks, slow cooling, and then cutting.

[0228] (Crystallization treatment)

[0229] The amorphous glass obtained through the above steps is heated to obtain microcrystalline glass.

[0230] The heat treatment can be a two-step process, starting from room temperature and raising it to a first treatment temperature, holding it for a certain time, followed by holding it at a second treatment temperature higher than the first treatment temperature for a certain time. Alternatively, it can be a one-step heat treatment, holding it at a specific treatment temperature and then cooling it to room temperature.

[0231] In the two-step heating process, the first processing temperature is preferably within a temperature range that increases the nucleation rate for the glass composition, and the second processing temperature is preferably within a temperature range that increases the crystal growth rate for the glass composition. Furthermore, regarding the holding time at the first processing temperature, a longer holding time is preferred to generate a sufficient number of crystal nuclei. By generating a large number of crystal nuclei, the size of each crystal becomes smaller, thereby obtaining a highly transparent microcrystalline glass.

[0232] In a two-step process, for example, the process involves holding the sample at a first treatment temperature of 450°C to 700°C for 1 to 6 hours, followed by holding it at a second treatment temperature of 600°C to 800°C for 1 to 6 hours. In a one-step process, for example, the process involves holding the sample at 500°C to 800°C for 1 to 6 hours.

[0233] The microcrystalline glass obtained from the above steps is ground and polished as needed to form a microcrystalline glass sheet. If the microcrystalline glass sheet is cut into a specified shape and size or chamfered, it is preferable to perform the cutting or chamfering before chemical strengthening treatment, as this will result in a compressive stress layer forming on the end face during the subsequent chemical strengthening treatment.

[0234] (Chemical enhancement treatment)

[0235] Chemical strengthening is a process in which glass is brought into contact with a metal salt (e.g., potassium nitrate) by means of immersion in a molten metal salt containing metal ions with large ionic radii (typically Na or Li ions), thereby replacing the metal ions with small ionic radii (typically Na or Li ions) in the glass with metal ions with large ionic radii (typically Na or K ions relative to Li ions, and K ions relative to Na ions).

[0236] To accelerate the chemical strengthening process, "Li-Na exchange," which involves exchanging Li ions with Na ions in the glass, is preferred. Furthermore, to generate large compressive stress through ion exchange, "Na-K exchange," which involves exchanging Na ions with K ions in the glass, is preferred.

[0237] Examples of molten salts used for chemical fortification treatment include nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts can be used alone or in combination.

[0238] The processing conditions for chemical strengthening can be selected by considering factors such as glass composition and the type of molten salt, including time and temperature. For example, it can be listed that the microcrystalline glass is preferably subjected to chemical strengthening treatment at 450°C or below, preferably for less than 1 hour. Specifically, it can be listed that immersion in a molten salt containing 0.3% by mass of Li and 99.7% by mass of Na (e.g., a mixed salt of lithium nitrate and sodium nitrate) at 450°C is preferably carried out for about 0.5 hours.

[0239] Chemical strengthening treatment can be carried out through two or more steps of ion exchange. Specifically, the two-step ion exchange is performed as follows: First, the glass-ceramic is preferably immersed in a metal salt containing Na ions (e.g., sodium nitrate) at a temperature of about 350°C to about 500°C for about 0.1 hours to about 10 hours. This results in ion exchange between Li ions in the glass-ceramic and Na ions in the metal salt, forming a relatively deep compressive stress layer.

[0240] When a compressive stress layer is formed on the surface portion of a glass article through chemical strengthening, a tensile stress corresponding to the total amount of compressive stress on the surface is inevitably generated in the central portion of the glass article. When the value of this tensile stress becomes too large, the glass article breaks violently when fractured, and the fragments scatter. When CT exceeds its threshold value (hereinafter sometimes simply referred to as the CT limit), the number of fractures at the time of damage increases explosively. In the case of performing ion exchange in two or more steps, the maximum tensile stress value of the stress distribution formed inside the glass through the initial ion exchange (first ion exchange) is preferably greater than the CT limit. By having the maximum tensile stress value after the first ion exchange be greater than the CT limit and introducing sufficient compressive stress through the first ion exchange, in the subsequent second ion exchange process, even after the stress value on the glass surface layer decreases, CS 50 and CS 90 can be maintained at a high level.

[0241] The CT limit is obtained by the following formula (1). CTA is equivalent to the CT limit and is a value determined by the composition of the glass for chemical strengthening. In addition, CTave is a value equivalent to the average value of the tensile stress, and CTave is obtained by the following formula (2). If CTave < CTA, it is below the CT limit, and an explosive increase in the number of fractures at the time of damage can be suppressed.

[0242]

[0243] t: Plate thickness (μm)

[0244] K1c: Fracture toughness value (MPa·m 1 / 2 )

[0245] CTave = ICT / L CT …Formula (2) ICT: Integral value of tensile stress (Pa·m)

[0246] L CT : Length in the plate thickness direction of the tensile stress region (μm)

[0247] Next, it is impregnated in a K-ion-containing metal salt (for example, potassium nitrate) preferably at about 350°C to about 500°C for preferably about 0.1 hour to about 10 hours. Thereby, a large compressive stress is generated in a portion within, for example, about 10 μm in depth of the compressive stress layer formed in the previous treatment. According to such a two-step treatment, a stress distribution with a large surface compressive stress value can be easily obtained.

[0248] As described above, the following matters are disclosed in this specification.

[0249] 1. A chemically strengthened glass, the chemically strengthened glass being a chemically strengthened glass with a thickness of t [μm] and containing Li2O, K2O, and Na2O, wherein,

[0250] The K₂O concentration at a depth of x [μm] from the surface, expressed as a molar percentage based on oxides, is denoted as K. x [%), Let the content of K2O before chemical fortification be K t / 2 When [%], K x For (K) t / 2 The maximum depth z above +0.1% is 0.5μm to 5μm.

[0251] 2. The chemically strengthened glass according to 1 above, wherein the K₂O concentration at a depth x [μm] from the surface, expressed as a molar percentage based on oxides, is denoted as K. x [%], The content of K2O before chemical fortification is set as K t / 2 When [%], K x For (K) t / 2 The Na₂O concentration at the maximum depth z [μm] above +0.1)[%] is set as Na z [%], Let the concentration of Na₂O at a depth of 50 μm from the surface be Na. 50 [%]hour,

[0252] |Na z -Na 50 |<3[%].

[0253] 3. The chemically strengthened glass according to 1 above, wherein the Na₂O concentration at a depth of 50 μm from the surface, expressed as a molar percentage based on oxides, is defined as Na₂O. 50 [%], Set the Na2O content before chemical fortification as Na t / 2 [%]hour,

[0254] Na 50 <Na t / 2 +7%

[0255] 4. The chemically strengthened glass according to any one of 1 to 3 above, wherein, based on the molar percentage of oxides, the K2O concentration at a depth of 1 μm from the surface is defined as K1 [%), the Na2O concentration at a depth of 1 μm from the surface is defined as Na1 [%), and the contents of Li2O, Na2O, and K2O before chemical strengthening are respectively defined as Li t / 2 [%], Na t / 2 [%] and K t / 2 [%]hour,

[0256] (Li t / 2 +Na t / 2 +K t / 2 )-2(Na1+K1)>0[%].

[0257] 5. The chemically strengthened glass according to any one of claims 1 to 4 above, wherein the surface compressive stress value CS0 of the chemically strengthened glass is 450 MPa or more, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is above 150 MPa and extends to a depth of 90 μm from the surface. 90 It is above 30MPa.

[0258] 6. The chemically strengthened glass according to any one of claims 1 to 4, wherein the surface compressive stress value CS0 of the chemically strengthened glass is 450 MPa or more, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is greater than or equal to y = 124.7 × t + 21.5 [MPa] and located at a depth of 90 μm from the surface. 90 The value is y = 99.1 × t - 38.3 [MPa] or higher.

[0259] 7. A chemically strengthened glass, wherein the penetration depth D of K ions is 0.5 μm to 5 μm.

[0260] The compressive stress value at the K ion penetration depth D is compared with the compressive stress value CS at a depth of 50 μm measured from the surface. 50 The absolute value of the difference is less than 150 MPa.

[0261] The compressive stress at the K ion penetration depth D is below 350 MPa.

[0262] The surface compressive stress value CS0 is above 450 MPa, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is above 150 MPa at a depth of 90 μm from the surface. 90 It is above 30MPa.

[0263] 8. The chemically strengthened glass according to any one of claims 1 to 7, wherein the chemically strengthened glass comprises a microcrystalline glass.

[0264] 9. The chemically strengthened glass according to any one of 1 to 8 above, wherein the basic composition contains 40% to 75% SiO2, 1% to 20% Al2O3, and 5% to 35% Li2O, based on the molar percentage of oxides.

[0265] 10. The chemically strengthened glass according to any one of 1 to 9 above, wherein the chemically strengthened glass has undergone two or more ion exchanges, wherein the initial ion exchange, i.e., the CTave after the first ion exchange, is greater than the CTA.

[0266] CTA is obtained by equation (1), and CTave is obtained by equation (2).

[0267]

[0268] t: Plate thickness (μm)

[0269] K1c: Fracture toughness value (MPa·m) 1 / 2 )

[0270] CTave = ICT / L CT …Equation (2) ICT: Integral value of tensile stress (Pa·m)

[0271] L CT : The length (μm) of the plate in the thickness direction of the tensile stress region.

[0272] 11. The chemically strengthened glass according to any one of claims 1 to 10 above, wherein the thickness t of the chemically strengthened glass is 300 μm to 1500 μm.

[0273] 12. The chemically strengthened glass according to any one of 1 to 11 above, wherein, when the surface slope at the glass surface defined by formula CS0 / D is set as P0, -1000 MPa / μm <P0<-225MPa / μm,

[0274] In the formula, CS0 is the surface compressive stress value (MPa), and D is the K ion penetration depth (μm).

[0275] 13. The chemically strengthened glass according to any one of claims 1 to 12, wherein the slope of the stress distribution of the chemically strengthened glass in the region between a depth of 50 μm measured from the surface and a depth of 90 μm measured from the surface is denoted as P. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm from the surface and a depth (DOL) (μm) where the compressive stress is zero. 90-DOL At (MPa / μm)

[0276] |P 50-90 |>|P 90-DOL |、1.8<|P 50-90 |<6.0 and 1.5<|P 90-DOL |<4.0,

[0277] The P 50-90 and the P 90-DOL It can be obtained by the following formula.

[0278] P 50-90 =(CS 50 -CS90 ) / 40

[0279] P 90-DOL =CS 90 / (DOL-90).

[0280] 14. The chemically strengthened glass according to any one of claims 1 to 13, wherein the slope of the stress distribution of the chemically strengthened glass in the region between a depth of 50 μm measured from the surface and a depth of 90 μm measured from the surface is denoted as P. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm from the surface and a depth (DOL) (μm) where the compressive stress is zero. 90-DOL At (MPa / μm)

[0281] |P 50-90 |<|P 90-DOL |、1.0<|P 50-90 |<3.0 and 1.2<|P 90-DOL |<4.0,

[0282] The P 50-90 and the P 90-DOL It can be obtained by the following formula.

[0283] P 50-90 =(CS 50 -CS 90 ) / 40

[0284] P 90-DOL =CS 90 / (DOL-90).

[0285] 15. A method for manufacturing chemically strengthened glass, wherein the chemically strengthened glass has a thickness of t [μm] and contains Li₂O, K₂O, and Na₂O, the method comprising chemically strengthening a glass containing Li₂O, wherein,

[0286] The K₂O concentration at a depth x [μm] from the surface is defined as K₂O, based on the molar percentage of the oxides in the chemically strengthened glass. x [%], Let the K2O content of the glass before chemical strengthening be K. t / 2 [%]hour,

[0287] So that K x For (K) t / 2 Chemical enhancement is performed with a maximum depth z of 0.5 μm to 5 μm above +0.1%)[%.

[0288] 16. The method for manufacturing chemically strengthened glass according to 15 above, wherein the Li2O-containing glass comprises microcrystalline glass.

[0289] 17. The method for manufacturing chemically strengthened glass according to 16 above, wherein the chemical strengthening includes two or more ion exchange steps, and the initial ion exchange, i.e., the CTave after the first ion exchange, is greater than the CTA.

[0290] CTA is obtained by equation (1), and CTave is obtained by equation (2).

[0291]

[0292] t: Plate thickness (μm)

[0293] K1c: Fracture toughness value (MPa·m) 1 / 2 )

[0294] CTave = ICT / L CT …Equation (2) ICT: Integral value of tensile stress (Pa·m)

[0295] L CT : The length (μm) of the plate in the thickness direction of the tensile stress region.

[0296] Example

[0297] The present invention will be described below through examples, but the present invention is not limited thereto.

[0298] <The Production and Evaluation of Amorphous Glass>

[0299] The glass raw materials were prepared in a manner that yielded the glass composition listed in Table 1 as a mole percent based on oxides, and weighed to obtain 800 g of glass. Next, the mixed glass raw materials were placed in a platinum crucible and melted in an electric furnace at 1600 °C for about 5 hours, followed by degassing and homogenization.

[0300] The molten glass obtained was poured into a mold and held at the glass transition temperature for 1 hour, then cooled to room temperature at a rate of 0.5 °C / min to obtain a glass block. A portion of the obtained block was used to evaluate the glass transition temperature, specific gravity, Young's modulus, and fracture toughness of the amorphous glass, and the evaluation results are shown in Table 1.

[0301] In the table, R2O represents the total content of Li2O, Na2O, and K2O, and NWF represents the total content of SiO2, Al2O3, P2O5, and B2O3.

[0302] (Specific gravity ρ)

[0303] Specific gravity ρ was determined using the Archimedes method.

[0304] (Glass transition temperature Tg)

[0305] The glass was crushed using an agate mortar and pestle. Approximately 80 mg of the powder was placed in a platinum bath. The heating rate was set to 10 °C / min, and the temperature was increased from room temperature to 1100 °C. At the same time, the DSC curve was measured using a differential scanning calorimeter (manufactured by Bruker; DSC3300SA), and the glass transition temperature Tg was determined.

[0306] Alternatively, based on JIS R1618:2002, a thermal expansion meter (manufactured by Bruker AXS; TD5000SA) is used, with the heating rate set to 10°C / min, to obtain the thermal expansion curve, and the glass transition temperature Tg [unit: °C] is determined from the obtained thermal expansion curve.

[0307] (Haze value)

[0308] The haze value under a halogen lamp C light source was measured using a haze meter (manufactured by Suga Testing Equipment Co., Ltd.; HZ-V3) [unit: %).

[0309] (Young's modulus E)

[0310] Young's modulus E was determined using an ultrasonic method.

[0311] (fracture toughness value Kc)

[0312] The fracture toughness value Kc was determined by the IF method according to JIS R1607:2015.

[0313] [CTA value]

[0314] The CTA value is obtained by the following formula (1).

[0315]

[0316] t: Plate thickness (μm)

[0317] K1c: Fracture toughness value (MPa·m) 1 / 2 )

[0318] Table 1

[0319] G1 G2 <![CDATA[SiO2]]> 61.0 51.2 <![CDATA[Al2O3]]> 5.0 5.0 <![CDATA[P2O5]]> 2.0 2.3 <![CDATA[Li2O]]> 21.0 34.1 <![CDATA[Na2O]]> 2.0 1.8 MgO 5.0 0.0 <![CDATA[ZrO2]]> 3.0 4.5 <![CDATA[Y2O3]]> 1.0 1.0 <![CDATA[R2O]]> 23.0 35.9 NWF 68.0 58.5 <![CDATA[ρ(g / cm 3 )]]> 2.56 2.57 Tg (°C) 513 494 Haze (%) 0.02 0.02 E(GPa) 90 97 <![CDATA[Kc(MPa·m 1 / 2 )]]> 0.98 0.86

[0320] <Evaluation of Crystallization Treatment and Microcrystalline Glass>

[0321] The obtained glass block was processed into 50mm×50mm×1.5mm pieces and then heat-treated under the conditions recorded in Table 2 to obtain glass-ceramic. In the crystallization conditions column of the table, the top row represents the nucleation treatment conditions and the bottom row represents the crystal growth treatment conditions. For example, if the top row is recorded as 550℃ for 2 hours and the bottom row as 730℃ for 2 hours, it means that the glass is held at 550℃ for 2 hours and then held at 730℃ for 2 hours.

[0322] The obtained glass-ceramic was processed by mirror polishing to obtain a glass-ceramic plate with a thickness t of 700 μm. Additionally, rod-shaped samples were prepared for determining the coefficient of thermal expansion. A portion of the remaining glass-ceramic was pulverized for analysis of precipitated crystals. The evaluation results of the glass-ceramic are shown in Table 2.

[0323] (X-ray diffraction: Precipitated crystals)

[0324] Powder X-ray diffraction was measured under the following conditions to identify the precipitated crystals.

[0325] Measurement device: Smart Lab manufactured by Rigaku Corporation, Japan

[0326] Using X-rays: CuKα rays

[0327] Measurement range: 2θ = 10°~80°

[0328] Speed: 1° / minute

[0329] Step size: 0.01°

[0330] The detected main crystals are shown in the crystal column of Table 2. Li3PO4 and Li4SiO4 are difficult to distinguish by powder X-ray diffraction, so both are recorded.

[0331] (Haze value)

[0332] The haze value under a halogen lamp C light source was measured using a haze meter (manufactured by Suga Testing Equipment Co., Ltd.; HZ-V3) [unit: %].

[0333] Table 2

[0334]

[0335] <Evaluation of Chemical Strengthening Treatments and Strengthened Glass>

[0336] Under the conditions shown in Table 3, microcrystalline glass CG1 and CG2 were chemically strengthened, and were designated as Examples 1 to 7, respectively. Examples 1 to 4, 6, and 7 in Table 3 are exemplary cases, and Example 5 is a comparative example. In Table 3, "%" represents "mass %".

[0337] The evaluation results of chemically strengthened glass are shown in Table 4. Blank columns (slashed lines) indicate no evaluation. Additionally, the stress distributions of Examples 1 and 5 are shown in... Figure 2 In Table 4, the plate thickness of Examples 1-7 was 700 mm, and the plate thickness of Examples 8 and 9 was 550 mm. Examples 1-4 and 6-9 are examples, and Example 5 is a comparative example. It should be noted that Examples 8 and 9 were chemically strengthened under the same conditions as Examples 6 and 7 recorded in Table 3.

[0338] (EPMA)

[0339] The measurements using EPMA were performed as follows. First, a glass sample was embedded in epoxy resin and mechanically ground along a direction perpendicular to the first principal surface and a second principal surface opposite to the first principal surface, thereby preparing a cross-sectional sample. A C-coating was applied to the ground cross-section, and measurements were performed using an EPMA (manufactured by JEOL: JXA-8500F). The accelerating voltage was set to 15 kV, the probe current to 30 nA, and the accumulation time to 1000 ms / point, and the spectral distribution of X-ray intensities for K, Na, or Li was obtained at 1 μm intervals.

[0340] (K ion penetration depth)

[0341] The K ion penetration depth D is determined by the following steps (1) to (3).

[0342] (1) The distribution of compressive stress (CS) in the depth direction of chemically strengthened glass was determined using a SLP-2000 photoelastic stress meter manufactured by Orihara Corporation.

[0343] (2) Next, for chemically strengthened glass, the same as the distribution of compressive stress values ​​in the depth direction as measured by SLP-2000 in (1), the distribution in the depth direction is measured by the following method.

[0344] With one side of the glass sealed, it was immersed in an acid solution with a volume fraction of 1% HF to 99% H2O, and etching of arbitrary thickness was performed only on that side. This created a stress difference between the surface and back of the chemically strengthened glass, causing the glass to warp. The amount of warpage was measured using a contact shape measuring instrument (Mitutoyo, Surftest). Warpage was measured at at least three points within the etch depth.

[0345] Based on the obtained warpage, the stress was converted using the formula shown in the following literature, thus obtaining the depth-direction distribution of the compressive stress value.

[0346] Reference: G. ...

[0347] (3) The depth of the point where the two distributions obtained in operation steps (1) and (2) overlap and intersect is taken as the “K ion invasion depth D”.

[0348] In Examples 6, 7, 8, and 9, the warpage resulting from grinding using a rotary grinder (device name: 9B-5P, manufacturer: SPEEDFAM) was measured using a contact shape measuring instrument (device name: SV-600, manufacturer: Mitutoyo).

[0349] (Stress distribution)

[0350] Stress distribution was measured using a scattered light photoelastic stress meter SLP-2000 manufactured by Orihara Corporation.

[0351] (Surface resistivity)

[0352] Surface resistivity was measured using a non-contact conductivity meter (manufactured by DELCOM).

[0353] (Drop test)

[0354] The drop test was conducted as follows: A glass sample measuring 120mm × 60mm × 0.6mm was embedded into a structure with its mass and rigidity adjusted to the size of a commonly used smartphone, thus creating a simulated smartphone. The simulated smartphone was then dropped freely onto #180 SiC sandpaper with a drop strength of #180, or onto #80 SiC sandpaper with a drop strength of #80. For drop height, if the sample did not break after being dropped from a height of 5cm, the drop height was repeatedly increased by 5cm and dropped again until breakage occurred. The average value of the first breakage of 10 glass samples was measured.

[0355] The durability (10,000 cycles) of AFP in this specification is determined by an eraser abrasion test under the following conditions.

[0356] Rubber abrasion test conditions:

[0357] The chemically strengthened glass surface is cleaned with ultraviolet light, and OPTOOL (registered trademark) DSX (manufactured by Daikin) is sprayed onto the glass surface to form a basically uniform AFP film.

[0358] At 1cm 2An eraser (manufactured by MIRAE SCIENCE, Minoan) was attached to the pressure head. Under a load of 1 kgf, the surface of the AFP membrane formed on the glass plate was rubbed reciprocally 10,000 times at a stroke width of 20 mm and a speed of 30 mm / s. The AFP membrane surface was then cleaned by wiping it dry with a cloth [manufactured by Ozu Corporation, DUSPER (registered trademark)]. The water contact angle (°) was then measured at three points on the AFP membrane surface. This operation was repeated three times, and the average water contact angle (°) was measured at a total of nine points. The water contact angle (°) of the AFP membrane surface was measured according to the method of JIS R3257 (1999).

[0359] (4PB strength)

[0360] Chemically strengthened glass was processed into strips measuring 120mm × 60mm. A four-point bending test was conducted under the conditions of a 30mm distance between external support points, a 10mm distance between internal support points, and a crosshead speed of 5.0mm / min to determine the four-point bending strength. Ten test pieces were used. It should be noted that after processing into strips, the chemically strengthened glass underwent automatic chamfering (C-chamfering) using a 1000-grit abrasive stone (manufactured by Tokyo Diamond Tools Manufacturing Co., Ltd.), and the end faces were mirror-finished using a 0.1mm diameter nylon brush and SHOROX NZ abrasive grains (manufactured by Showa Denko Co., Ltd.). The resulting 120mm × 60mm × 0.7mm thick chemically strengthened glass was then measured. The results of evaluating the measured 4PB strength using the following indicators are shown.

[0361] A: The strength of 4PB is above 779MPa.

[0362] B: The strength of 4PB is above 600MPa and less than 779MPa.

[0363] C: 4PB strength is less than 600MPa.

[0364]

[0365]

[0366] As shown in Table 4 and Figure 2 As shown, compared to Example 5 as a comparative example, Examples 1-4 and 6-9 as embodiments exhibit superior chemical strengthening properties and high AFP durability, effectively suppressing coating peeling. Furthermore, in Examples 1-4, compressive stress was introduced after the first ion exchange until it exceeded the CT limit, thus reducing the stress value of the glass surface layer during the second ion exchange process.

[0367] For Examples 1, 6 and 7, the results of the measured 4PB strength are shown in Table 5.

[0368] Table 5

[0369] Example 1 Example 6 Example 7 microcrystalline glass CG1 CG1 CG1 4PB strength (MPa) 589 836 779 4PB strength C A A

[0370] As shown in Table 5, compared with the chemically strengthened glass of Example 1, the 4PB strength (MPa) of the chemically strengthened glasses of Examples 6 and 7 showed higher values. From the viewpoint of chemically strengthened glass that requires higher bending strength, the 4PB strength (MPa) of Examples 6 and 7 is greater than 550 MPa, and thus is preferable. It can be seen that the conditions of CS0 shown in Table 4 contribute to achieving such excellent 4PB strength.

[0371] In addition, in Table 6, for the chemically strengthened glasses of Examples 1 to 9, the following measurement results are shown: the surface slope P0 at the glass surface layer, the slope |P 50-90 | of the stress distribution of the chemically strengthened glass in the region between the depth of 50 μm from the surface and the depth of 90 μm from the surface, and the slope |P 90-DOL | of the stress distribution of the chemically strengthened glass in the region between the depth of 90 μm from the surface and the depth (DOL) (μm) where the compressive stress value is zero. The blank column (diagonal line) indicates not evaluated.

[0372]

[0373] As shown in Table 6, it was confirmed that compared with Example 5 of the comparative example, the P0 values of Examples 1 to 4 and 6 to 9 as the examples are in the range of -1000 MPa / μm < P0 < -225 MPa / μm, and the 4PB strength is in the range greater than 550 MPa.

[0374] In addition, it was confirmed that the value of |P 50-90 | (MPa / μm) is |P 50-90 | > |P 90-DOL |, and the #180 drop strength of Examples 1, 4, 6, and 8 where 1.8 < |P 50-90 | < 6.0 and 1.5 < |P 90-DOL | <4.0 is 100 cm or more.

[0375] In addition, it was confirmed that |P 50-90 | < |P 90-DOL |, and the #80 drop strength of Examples 2, 3, 7, and 9 where 1.0 < |P 50-90 | < 3.0 and 1.2 < |P 90-DOL | < 4.0 is 40 cm or more.

[0376] Although the present invention has been described in detail and with reference to specific embodiments, various changes and modifications can be made without departing from the spirit and scope of the invention, which will be apparent to those skilled in the art. It should be noted that this application is based on Japanese patent applications filed on April 7, 2021 (Japanese Patent Application No. 2021-065434) and December 20, 2021 (Japanese Patent Application No. 2021-206353), the entire contents of which are incorporated herein by reference. Furthermore, all references cited herein are incorporated herein by reference in their entirety.

Claims

1. A chemically strengthened glass, wherein the chemically strengthened glass has a thickness of t μm and contains Li₂O, K₂O and Na₂O, wherein, Let K be the K₂O concentration at a depth of x μm from the surface, expressed as a molar percentage based on oxides. x The content of K₂O before chemical fortification, expressed as a molar percentage based on oxides, is set as K. t / 2 hour, K x For (K) t / 2 The maximum depth z above +0.1) is 0.5μm to 5μm, (K t / 2 +0.1) is in moles. The chemically strengthened glass contains 20% to 35% Li₂O in its basic composition, based on the molar percentage of oxides.

2. The chemically strengthened glass according to claim 1, wherein, Let K be the K₂O concentration at a depth of x μm from the surface, expressed as a molar percentage based on oxides. x The content of K₂O before chemical fortification, expressed as a molar percentage based on oxides, is set as K. t / 2 At that time, K x For (K) t / 2 The Na₂O concentration at a maximum depth of z μm (+0.1) above the maximum depth is defined as the Na₂O concentration as a molar percentage based on oxides. z Let the concentration of Na₂O at a depth of 50 μm from the surface, expressed as a molar percentage based on oxides, be denoted as Na. 50 hour, |Na z -Na 50 |<3 moles%.

3. The chemically strengthened glass according to claim 1, wherein, Let the concentration of Na₂O at a depth of 50 μm from the surface, expressed as a molar percentage based on oxides, be denoted as Na. 50 The content of Na₂O before chemical fortification, expressed as a molar percentage based on oxides, is set as Na. t / 2 hour, Na 50 <Na t / 2 +7 moles%.

4. The chemically strengthened glass according to claim 1, wherein, Let K1 be the K2O concentration at a depth of 1 μm from the surface, expressed as a molar percentage based on oxides; let Na1 be the Na2O concentration at a depth of 1 μm from the surface, expressed as a molar percentage based on oxides; and let Li1 be the content of Li2O, Na2O, and K2O before chemical strengthening, expressed as a molar percentage based on oxides. t / 2 Na t / 2 and K t / 2 hour, (Li t / 2 +Na t / 2 +K t / 2 )-2(Na1+K1)>0 moles%.

5. The chemically strengthened glass according to claim 1, wherein, The surface compressive stress value CS0 of the chemically strengthened glass is above 450 MPa, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is above 150 MPa and extends to a depth of 90 μm from the surface. 90 It is above 30MPa.

6. The chemically strengthened glass according to claim 1, wherein, The surface compressive stress value CS0 of the chemically strengthened glass is above 450 MPa, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is greater than or equal to y = 124.7 × t + 21.5 MPa and located at a depth of 90 μm from the surface. 90 The value is above y = 99.1 × t - 38.3 MPa.

7. The chemically strengthened glass according to any one of claims 1 to 6, wherein, The chemically strengthened glass comprises microcrystalline glass.

8. The chemically strengthened glass according to any one of claims 1 to 6, wherein, Based on the molar percentage of oxides, the basic composition contains 40%–75% SiO2, 1%–20% Al2O3, and 20%–35% Li2O.

9. The chemically strengthened glass according to any one of claims 1 to 6, wherein the chemically strengthened glass is a chemically strengthened glass that has undergone two or more steps of ion exchange, wherein... The initial ion exchange, i.e., the CTave after the first ion exchange, is greater than the CTA. CTA is obtained by equation (1), and CTave is obtained by equation (2). t: Plate thickness, in μm K1c: Fracture toughness value, in MPa m 1 / 2 CTave=ICT / L CT …Formula (2) ICT: Integral value of tensile stress, in Pa. m L CT : The length of the plate in the thickness direction of the tensile stress region, in μm.

10. The chemically strengthened glass according to any one of claims 1 to 6, wherein, The thickness t of the chemically strengthened glass is 300 μm to 1500 μm.

11. The chemically strengthened glass according to any one of claims 1 to 6, wherein, When the surface slope at the glass surface, as defined by equation CS0 / D, is set to P0, -1000MPa / μm <P0<-225MPa / μm, In the formula, CS0 is the surface compressive stress value in MPa, and D is the K ion penetration depth in μm.

12. The chemically strengthened glass according to any one of claims 1 to 6, wherein, Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 50 μm and a depth of 90 μm measured from the surface. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm measured from the surface and a depth DOL where the compressive stress is zero. 90-DOL In this case, the unit of DOL is μm, P 50-90 The unit is MPa / μm, P 90-DOL The unit is MPa / μm. |P 50-90 |>|P 90-DOL |、1.8<|P 50-90 |<6.0 and 1.5<|P 90-DOL |<4.0, The P 50-90 and the P 90-DOL It can be obtained by the following formula. P 50-90 =(CS 50 -CS 90 ) / 40 P 90-DOL =CS 90 / (DOL-90).

13. The chemically strengthened glass according to any one of claims 1 to 6, wherein, Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 50 μm and a depth of 90 μm measured from the surface. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm measured from the surface and a depth DOL where the compressive stress is zero. 90-DOL In this case, the unit of DOL is μm, P 50-90 The unit is MPa / μm, P 90-DOL The unit is MPa / μm. |P 50-90 |<|P 90-DOL |、1.0<|P 50-90 |<3.0 and 1.2<|P 90-DOL |<4.0, The P 50-90 and the P 90-DOL It can be obtained by the following formula. P 50-90 =(CS 50 -CS 90 ) / 40 P 90-DOL =CS 90 / (DOL-90).

14. A chemically strengthened glass, wherein, The penetration depth D of K ions is 0.5 μm to 5 μm. The compressive stress value at the K ion penetration depth D is compared with the compressive stress value CS at a depth of 50 μm measured from the surface. 50 The absolute value of the difference is less than 150 MPa. The compressive stress at the K ion penetration depth D is below 350 MPa. The surface compressive stress value CS0 is above 450 MPa, and the compressive stress value CS at a depth of 50 μm from the surface is... 50 The compressive stress CS is above 150 MPa at a depth of 90 μm from the surface. 90 Above 30MPa The chemically strengthened glass contains 20% to 35% Li₂O in its basic composition, based on the molar percentage of oxides.

15. The chemically strengthened glass according to claim 14, wherein, The chemically strengthened glass comprises microcrystalline glass.

16. The chemically strengthened glass according to claim 14, wherein, Based on the molar percentage of oxides, the basic composition contains 40%–75% SiO2, 1%–20% Al2O3, and 20%–35% Li2O.

17. The chemically strengthened glass according to claim 14, wherein the chemically strengthened glass is a chemically strengthened glass that has undergone two or more ion exchange steps, wherein... The initial ion exchange, i.e., the CTave after the first ion exchange, is greater than the CTA. CTA is obtained by equation (1), and CTave is obtained by equation (2). t: Plate thickness, in μm K1c: Fracture toughness value, in MPa m 1 / 2 CTave=ICT / L CT …Formula (2) ICT: Integral value of tensile stress, in Pa. m L CT : The length of the plate in the thickness direction of the tensile stress region, in μm.

18. The chemically strengthened glass according to claim 14, wherein, The thickness t of the chemically strengthened glass is 300 μm to 1500 μm.

19. The chemically strengthened glass according to claim 14, wherein, When the surface slope at the glass surface, as defined by equation CS0 / D, is set to P0, -1000MPa / μm <P0<-225MPa / μm, In the formula, CS0 is the surface compressive stress value in MPa, and D is the K ion penetration depth in μm.

20. The chemically strengthened glass according to claim 14, wherein, Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 50 μm and a depth of 90 μm measured from the surface. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm measured from the surface and a depth DOL where the compressive stress is zero. 90-DOL In this case, the unit of DOL is μm, P 50-90 The unit is MPa / μm, P 90-DOL The unit is MPa / μm. |P 50-90 |>|P 90-DOL |、1.8<|P 50-90 |<6.0 and 1.5<|P 90-DOL |<4.0, The P 50-90 and the P 90-DOL It can be obtained by the following formula. P 50-90 =(CS 50 -CS 90 ) / 40 P 90-DOL =CS 90 / (DOL-90).

21. The chemically strengthened glass according to claim 14, wherein, Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 50 μm and a depth of 90 μm measured from the surface. 50-90 Let P be the slope of the stress distribution in the chemically strengthened glass in the region between a depth of 90 μm measured from the surface and a depth DOL where the compressive stress is zero. 90-DOL In this case, the unit of DOL is μm, P 50-90 The unit is MPa / μm, P 90-DOL The unit is MPa / μm. |P 50-90 |<|P 90-DOL |、1.0<|P 50-90 |<3.0 and 1.2<|P 90-DOL |<4.0, The P 50-90 and the P 90-DOL It can be obtained by the following formula. P 50-90 =(CS 50 -CS 90 ) / 40 P 90-DOL =CS 90 / (DOL-90).

22. A method for manufacturing chemically strengthened glass, wherein the chemically strengthened glass has a thickness of t μm and contains Li₂O, K₂O, and Na₂O, the method comprising chemically strengthening a glass containing Li₂O, wherein, The Li₂O-containing glass contains 20% to 35% Li₂O, based on the molar percentage of oxides. Let K be the K₂O concentration at a depth x μm from the surface of the chemically strengthened glass, expressed as a molar percentage based on oxides. x The K₂O content of the glass before chemical strengthening, expressed as a molar percentage based on oxides, is defined as K. t / 2 hour, So that K x For (K) t / 2 Chemical enhancement is performed at a maximum depth z of 0.5 μm to 5 μm (+0.1) or higher. t / 2 The unit of +0.1) is moles.

23. The method for manufacturing chemically strengthened glass according to claim 22, wherein, The Li2O-containing glass comprises microcrystalline glass.

24. The method for manufacturing chemically strengthened glass according to claim 23, wherein, The chemical fortification involves two or more ion exchange steps, with the initial ion exchange, i.e., the first ion exchange, having a CTave greater than the CTA. CTA is obtained by equation (1), and CTave is obtained by equation (2). t: Plate thickness, in μm K1c: Fracture toughness value, in MPa m 1 / 2 CTave=ICT / L CT …Formula (2) ICT: Integral value of tensile stress, in Pa. m L CT : The length of the plate in the thickness direction of the tensile stress region, in μm.

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