Crystallized glass and method for manufacturing the same, chemically strengthened glass, and electronic device

Abstract

The present invention relates to a crystallized glass containing, as a crystal having the largest content by mass, a lithium disilicate crystal in which the proportion of Li ions in Li ion sites is less than 95%.

Description

Technical Field

[0001] This invention relates to a crystalline glass and its manufacturing method, chemically strengthened glass, and electronic devices. Background Technology

[0002] For protective glass for portable devices, which requires strength to withstand drops without easily breaking, chemically strengthened glass is widely used. Chemically strengthened glass is produced by immersing glass in molten salts such as sodium nitrate, causing ion exchange between the alkali ions in the glass and the larger alkali ions in the molten salt, thus forming a compressive stress layer on the surface of the glass.

[0003] Crystalline glass is formed by precipitating crystals within glass, making it harder and less prone to damage compared to amorphous glass, which lacks crystals. Furthermore, chemically strengthened crystalline glass can achieve high strength while preventing breakage, unlike amorphous glass. For example, Patent Document 1 describes a method for chemically strengthening crystalline glass containing specified crystals through ion exchange.

[0004] In electronic devices such as mobile motors, smartphones, portable information terminals, Wi-Fi devices, surface acoustic wave (SAW) devices, radar components, and antenna components, the use of higher signal frequencies is being promoted to achieve greater communication capacity and higher communication speeds. In recent years, 5G (fifth-generation mobile communication system) has been expected to become widespread as a new communication system using even higher frequency bands. In the high-frequency bands used in 5G, protective glass can sometimes obstruct radio wave transmission and reception, requiring protective glass with excellent radio wave transmittance for 5G-enabled electronic devices. In other words, protective glass used in mobile terminals and other electronic devices requires excellent strength and radio wave transmittance.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-33262 Summary of the Invention

[0008] However, while conventional chemically strengthened crystalline glasses can improve strength through chemical strengthening, their properties affecting radio wave transmittance, such as relative permittivity and dielectric loss tangent, tend to become relatively large, resulting in insufficient radio wave transmittance. Therefore, obtaining glass that combines both strength and radio wave transmittance is very difficult. Furthermore, the crystalline glass described in Patent Document 1, although its strength can be improved through chemical strengthening, is not specifically designed for radio wave transmittance, thus also lacking in radio wave transmittance.

[0009] In view of the above-mentioned problems, the object of the present invention is to provide a crystalline glass that achieves excellent strength and excellent radio wave transmittance through chemical strengthening. Furthermore, the object of the present invention is to provide a chemically strengthened glass that excels in both strength and radio wave transmittance.

[0010] To improve electromagnetic transmittance, it is preferable to have a small relative permittivity and a small dielectric loss tangent. Furthermore, the electromagnetic transmittance of a crystalline glass can be affected by the electromagnetic transmittance of the crystals it contains. The inventors conducted in-depth research and found that lithium disilicate crystals have a particularly small relative permittivity, thus exhibiting excellent electromagnetic transmittance. On the other hand, it is also known that the dielectric loss tangent of lithium disilicate crystals can vary depending on the state of the crystal. Specifically, it is known that by reducing the proportion of Li ions in the Li ion sites of the lithium disilicate crystal, the value of the dielectric loss tangent of the lithium disilicate crystal can be reduced. The inventors discovered that this further improves electromagnetic transmittance, thus completing the present invention.

[0011] That is, the present invention relates to the following 1 to 11.

[0012] 1. A crystalline glass, wherein the most abundant crystal by mass is a lithium disilicate crystal.

[0013] In the lithium disilicate crystal, the proportion of Li ions in the Li ion sites is less than 95%.

[0014] 2. The crystalline glass according to claim 1, wherein the transmittance, converted to a thickness of 0.7 mm, is 85% or more in the wavelength range of 400 nm to 1000 nm.

[0015] 3. The crystalline glass according to claim 1 or 2, wherein the haze value, converted to a thickness of 0.7 mm, is less than 5% in the wavelength range of 400 nm to 1000 nm.

[0016] 4. The crystal glass according to claim 1 or 2, wherein the sum of the value obtained by multiplying the loss tangent tanδ at 10 GHz and 20 °C by 100 and the relative permittivity Dk at 10 GHz and 20 °C is 7.5 or less.

[0017] 5. The crystalline glass according to claim 1 or 2, wherein the relative permittivity Dk at 10 GHz and 20 °C is 5.8 or less.

[0018] 6. The crystalline glass according to claim 1 or 2, wherein, expressed as a molar percentage based on oxides, it comprises 55-85% SiO2, 1-5% Al2O3, 0-5.0% B2O3, 0.5-5.0% P2O5, 0-5.0% TiO2, 0-5.0% ZrO2, 15-25% Li2O, 0-5.0% Na2O, 0-5.0% K2O, and a total of 0-5.0% of one or more selected from MgO, CaO, SrO, and BaO.

[0019] 7. The crystalline glass according to claim 6, wherein it contains 0.1 to 5.0% Na₂O, expressed as a molar percentage based on oxides.

[0020] 8. A method for manufacturing crystal glass, which is the method for manufacturing crystal glass described in 1 or 2 above.

[0021] This includes a step of heat treatment of the amorphous glass in at least one stage.

[0022] The temperature of each heat treatment is below 750°C. In each heat treatment, the heating rate to the treatment temperature and the cooling rate from the treatment temperature are both above 0.5°C / minute.

[0023] 9. A chemically strengthened glass, comprising a compressive stress layer on its surface.

[0024] The surface compressive stress value is above 50 MPa, and the chemically strengthened glass is the crystalline glass described in 1 or 2.

[0025] 10. The chemically strengthened glass according to 9, which is plate-shaped, wherein the proportion of alkali metal elements differs between the surface and the center in the thickness direction.

[0026] 11. An electronic device having the crystal glass described in 1 above.

[0027] Invention Effects

[0028] The crystalline glass of the present invention can be chemically strengthened. Furthermore, in the crystalline glass of the present invention, the proportion of Li ions in the Li ion sites of the lithium disilicate crystal is small. Therefore, the crystalline glass of the present invention achieves excellent strength and excellent electromagnetic transmittance through chemical strengthening.

[0029] The chemically strengthened glass of the present invention is a crystalline glass, in which the proportion of Li ions in the Li ion sites of the lithium disilicate crystal is small, thus resulting in excellent strength and electromagnetic transmittance. Detailed Implementation

[0030] In this specification, the symbol “~” indicating a numerical range is used to encompass the values ​​described before and after it as the lower and upper limits. Unless otherwise specified, “~” will have the same meaning in this specification below.

[0031] In this specification, "chemically strengthened glass" refers to glass that has undergone chemical strengthening treatment, and "glass for chemical strengthening" refers to glass that has not undergone chemical strengthening treatment.

[0032] In this specification, "basic composition of chemically strengthened glass" refers to the glass composition of chemically strengthened glass. For chemically strengthened glass, except in cases of extreme ion replacement treatment, the glass composition at a depth of 1 / 2 the thickness t constitutes the basic composition of chemically strengthened glass.

[0033] In this specification, unless otherwise specified, the glass composition is expressed as a molar percentage based on oxides, and the molar percentage is abbreviated as "%".

[0034] Furthermore, in this specification, "substantially not containing" means below the level of impurities contained in raw materials, etc., i.e., not intentionally contained. Specifically, for example, less than 0.1 mol%.

[0035] In this specification, "stress distribution" refers to a curve representing the compressive stress value with the depth from the glass surface as a variable. Additionally, "compressive stress layer depth (DOL)" is the depth at which the compressive stress value (CS) becomes zero. "Internal tensile stress value (CT)" refers to the tensile stress value at a depth of 1 / 2 the thickness t of the glass sheet.

[0036] The stress distribution described in this specification can be measured using a scattered light photoelastic stress meter (e.g., the SLP-1000 manufactured by Orihara Manufacturing Co., Ltd.). Scattered light photoelastic stress meters are affected by surface scattering, sometimes reducing the measurement accuracy near the sample surface. However, in cases where compressive stress is generated solely through ion exchange between lithium ions in the glass and external sodium ions, the compressive stress value, expressed as a function of depth, follows a complementary error function; therefore, the surface stress value can be determined by measuring the internal stress value. In cases where the complementary error function is not followed, the surface portion can be measured using other methods, such as methods employing a surface stress meter.

[0037] In this specification, "amorphous glass" and "crystalline glass" are sometimes referred to collectively as "glass". In this specification, "amorphous glass" refers to glass in which diffraction peaks indicating crystals have not been confirmed by powder X-ray diffraction.

[0038] In this specification, "crystalline glass" refers to glass in which crystals precipitate due to heat treatment of "amorphous glass," meaning glass in which crystals have precipitated. In this specification, "crystalline glass" refers to glass in which diffraction peaks representing crystals are confirmed by X-ray diffraction (XRD). X-ray diffraction measurements can be performed, for example, using CuKα rays to measure the range of 2θ from 10° to 80°.

[0039] In this specification, the identification of crystals precipitated in a crystallizing glass can be performed by powder X-ray diffraction (PXRD). Furthermore, to obtain a more accurate crystal structure, Rietveld analysis is preferred. Rietveld analysis allows for quantitative analysis of crystalline and amorphous phases, as well as structural analysis of the crystalline phase. The Rietveld method is described in the "Crystal Analysis Handbook" edited by the Editorial Committee of the Japan Crystallographic Society (Kyoritsu Publishing, 1999, pp. 492-499). That is, in this specification, the content and crystallinity of each crystal in the crystallizing glass can be determined, for example, by performing Rietveld analysis on the XRD pattern obtained by powder X-ray diffraction (PXRD).

[0040] In this specification, "transmittance" refers to the parallel transmittance within the wavelength range of 400 nm to 1000 nm. Additionally, "haze value" refers to the value measured using a C light source according to JIS K3761:2000.

[0041] (Crystal Glass)

[0042] (Crystal)

[0043] The crystal glass of this embodiment (hereinafter also referred to as the crystal glass) has a lithium disilicate crystal as the most abundant crystal by mass. In the lithium disilicate crystal, the proportion of Li ions in the Li ion sites is less than 95%.

[0044] This crystalline glass contains lithium disilicate crystals. Examples of lithium disilicate crystals include, for instance, lithium disilicate (Li₂Si₂O₅) and Li₂. 2－x Na x Si2O5, Li2Si 2－3x Al 4x O5, etc.

[0045] By incorporating lithium disilicate-based crystals, the electromagnetic transmittance of this crystalline glass is improved. From the viewpoint of improving electromagnetic transmittance, the content of lithium disilicate-based crystals in this crystalline glass is preferably 20% by mass or more, more preferably 25% by mass or more, further preferably 30% by mass or more, particularly preferably 35% by mass or more, further particularly preferably 40% by mass or more, further preferably 45% by mass or more, further preferably 50% by mass or more, and most preferably 55% by mass or more. On the other hand, from the viewpoint of maintaining transparency, this content is preferably 90% by mass or less, more preferably 85% by mass or less, further more preferably 80% by mass or less, particularly preferably 75% by mass or less, further preferably 70% by mass or less, and most preferably 65% ​​by mass or less. The content of lithium disilicate crystals is preferably 20-90% by mass, more preferably 25-85% by mass, even more preferably 30-80% by mass, even more preferably 35-75% by mass, particularly preferably 40-70% by mass, even more preferably 45-65% by mass, even more preferably 50-65% by mass, and most preferably 55-65% by mass.

[0046] The presence of lithium disilicate crystals in the crystal glass can be confirmed by the presence of peaks at the (002) plane in the XRD pattern, which are located between 2θ = 36° and 37°. Furthermore, the content of lithium disilicate crystals can be determined using the Rietveld analysis method.

[0047] In this crystalline glass, the most abundant crystal by mass is lithium disilicate crystal.

[0048] In lithium disilicate crystals, the proportion of Li ions in Li ion sites is less than 95%. When the proportion of Li ions in Li ion sites is less than a certain amount, it is considered that the Li ion sites without Li ions contain at least one of the following: vacancies and elements other than Li (dissimilar elements). There are no particular limitations on what constitutes a dissimilar element; for example, elements with valences close to Li can be cited, such as Na and Al.

[0049] The proportion of Li ions in the Li ion sites is determined by the Rietveld analysis described above. In this specification, the unit "%" for the proportion of Li ions in the Li ion sites is "atom%".

[0050] From the viewpoint of improving radio wave transmittance, the proportion of Li ions in the Li ion sites is less than 95%, preferably less than 90%, more preferably less than 85%, further preferably 80%, particularly preferably less than 75%, further particularly preferably less than 70%, further preferably less than 65%, and most preferably less than 60%. On the other hand, from the viewpoint of maintaining the crystal structure, the proportion of Li ions in the Li ion sites is preferably 30% or more, more preferably 35% or more, further preferably 40% or more, particularly preferably 45% or more, and further preferably 50% or more. The proportion of Li ions in the Li ion sites is preferably 30% or more and less than 90%, more preferably 35% or more and less than 85%, further preferably 40% or more and less than 80%, even more preferably 45% or more and less than 75%, particularly preferably 50% or more and less than 70%, further particularly preferably 50% or more and less than 65%, and further preferably 50% or more and less than 60%.

[0051] For this crystalline glass, the most abundant crystal by mass is lithium disilicate crystal. In lithium disilicate crystal, the proportion of Li ions in the Li ion sites is less than 95%, resulting in excellent electromagnetic transmittance. The reasons for this are as follows.

[0052] To improve electromagnetic wave transmittance, it is preferable to have a relatively small relative permittivity and dielectric loss tangent. Furthermore, the electromagnetic wave transmittance of a crystalline glass may be affected by the electromagnetic wave transmittance of the crystals it contains.

[0053] The inventors conducted in-depth research and found that lithium disilicate crystals, in particular, have a small relative permittivity, resulting in excellent electromagnetic wave transmittance. Furthermore, it was also discovered that the dielectric loss tangent of lithium disilicate crystals can vary depending on the crystal's state. Specifically, it was found that by reducing the proportion of Li ions in the Li ion sites of the lithium disilicate crystal, the value of the dielectric loss tangent can be reduced.

[0054] The reason for this is believed to be that in the crystal structure of lithium disilicate crystals, the atomic oscillation of Li ion sites is the greatest when an electric field is applied, which becomes the main factor increasing the dielectric loss tangent. That is, by replacing the Li ion sites with vacancies or elements other than Li (dissimilar elements), the oscillation of Li ions can be suppressed as a whole crystal. Therefore, it is speculated that the dielectric loss tangent of lithium disilicate crystals and crystalline glasses containing such crystals is smaller.

[0055] This crystalline glass utilizes lithium disilicate as the most abundant crystal by mass, which facilitates a lower relative permittivity. Furthermore, the low proportion of Li ions at Li ion sites within the lithium disilicate crystal contributes to a smaller dielectric loss tangent. Consequently, this crystalline glass exhibits superior electromagnetic transmittance compared to conventional glass.

[0056] This crystalline glass may contain any crystal other than lithium disilicate crystals (hereinafter also referred to as other crystals). Other crystals may be one type or multiple types. There are no particular limitations on what constitutes other crystals; for example, petalite (LiAlSi4O3) can be included. 10 It includes crystals such as lithium metasilicate (Li2SiO3), lithium nepheline (LiAlSiO4), etc.

[0057] From the viewpoint of improving the transparency of crystal glass, lithium feldspar (LiAlSi4O4) is preferred among other crystals. 10 () series crystals. Crystalline glass containing, for example, lepidolite-based crystals can be confirmed by the presence of peaks attributable to the (002) plane in the XRD pattern between 2θ = 25° and 26°.

[0058] It should be noted that this crystal glass may also be free of other crystals.

[0059] When this crystalline glass contains other crystals, for example from the viewpoint of improving radio wave transmittance, the preferred content, depending on the type of crystal, is preferably 50% by mass or less, more preferably 45% by mass or less, further preferably 40% by mass or less, particularly preferably 35% by mass or less, further preferably 30% by mass or less, and most preferably 25% by mass or less. From the viewpoint of improving transparency, the content of other crystals, depending on the type of crystal, is preferably 0% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and particularly preferably 15% by mass or more. The content of other crystals, depending on the type of crystal, is preferably 0 to 50% by mass, more preferably 5 to 45% by mass, further preferably 10 to 40% by mass, even more preferably 15 to 35% by mass, particularly preferably 15 to 30% by mass, and even more particularly preferably 15 to 25% by mass.

[0060] Furthermore, from the viewpoint of improving radio wave transmittance, the total content of other crystals is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less, even more preferably 30% by mass or less, and most preferably 25% by mass or less. From the viewpoint of improving transparency, the total content of other crystals is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and particularly preferably 15% by mass or more. The total content of other crystals is preferably 0 to 50% by mass, more preferably 5 to 45% by mass, even more preferably 10 to 40% by mass, even more preferably 15 to 35% by mass, particularly preferably 15 to 30% by mass, and even more particularly preferably 15 to 25% by mass.

[0061] From the viewpoint of improving radio wave transmittance, the difference obtained by subtracting the proportion (by mass%) of the second most abundant crystal in the crystalline glass from the proportion (by mass%) of lithium disilicate-based crystals is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, particularly preferably 25% by mass or more, further preferably 30% by mass or more, further preferably 35% by mass or more, and most preferably 40% by mass or more. On the other hand, from the viewpoint of improving transparency, this difference is preferably 60% by mass or less, more preferably 55% by mass or less, and further preferably 50% by mass or less. This difference is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, further preferably 20 to 50% by mass, even more preferably 25 to 50% by mass, particularly preferably 30 to 50% by mass, particularly preferably 35 to 50% by mass, and further preferably 40 to 50% by mass.

[0062] It should be noted that, in the case that this crystallized glass does not contain other crystals, "the percentage of the second most abundant crystal by mass (mass%)" is 0 by mass.

[0063] From the viewpoints of improving radio wave transmittance and increasing strength, the crystallinity of this crystalline glass is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, particularly preferably 65% ​​by mass or more, further preferably 70% by mass or more, further preferably 75% by mass or more, and most preferably 80% by mass or more. From the viewpoint of improving transparency, the crystallinity is preferably 95% by mass or less, more preferably 90% by mass or less. The crystallinity is preferably 50–95% by mass, more preferably 55–95% by mass, further preferably 60–95% by mass, even more preferably 65–95% by mass, particularly preferably 70–95% by mass, further particularly preferably 75–95% by mass, and even more preferably 80–90% by mass.

[0064] In this crystalline glass, from the viewpoint of improving radio wave transmittance, the proportion of the amorphous phase is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, and most preferably 20% by mass or less. From the viewpoint of improving transparency, the proportion of the amorphous phase is preferably 5% by mass or more, more preferably 10% by mass or more. The proportion of the amorphous phase is preferably 5 to 50% by mass, more preferably 5 to 45% by mass, even more preferably 5 to 40% by mass, even more preferably 5 to 35% by mass, particularly preferably 5 to 30% by mass, even more particularly preferably 5 to 25% by mass, and even more preferably 10 to 20% by mass. Here, in this specification, the amorphous phase refers to the value obtained by subtracting the sum (by mass%) of the proportion of crystallization obtained by Rietveld analysis from 100% by mass.

[0065] In this crystalline glass, the average particle size of the precipitated crystals is preferably 5 to 80 nm. From the viewpoint of improving transparency, an average particle size of 80 nm or less is preferred, more preferably 70 nm or less, further preferably 60 nm or less, even more preferably 50 nm or less, particularly preferably 40 nm or less, and most preferably 30 nm or less. To improve strength, the average particle size of the precipitated crystals is preferably 5 nm or more, more preferably 6 nm or more, further preferably 7 nm or more, particularly preferably 8 nm or more, further preferably 9 nm or more, and most preferably 10 nm or more. The average particle size of the precipitated crystals can be determined from transmission electron microscopy (TEM) images. The average particle size of the precipitated crystals can be inferred from scanning electron microscopy (SEM) images.

[0066] (Composition of crystal glass)

[0067] The glass composition of this crystalline glass is the same as that of the amorphous glass before crystallization in the manufacturing method described later. Therefore, the preferred configurations of the glass composition of this crystalline glass and the glass composition of the amorphous glass are the same. Here, the composition of the crystalline glass in this specification refers to the composition formed by combining the compositions of the crystalline phase and the amorphous phase of the crystalline glass. Furthermore, the glass composition of the crystalline glass is determined by heat-treating the crystalline glass at a temperature above its melting point and analyzing the vitrified glass. As an analytical method, fluorescence X-ray analysis can be cited.

[0068] The glass composition of this crystallizing glass is not particularly limited, but an example of a preferred embodiment is shown below. In the glass composition of this crystallizing glass, the lower limit of the preferred content of non-essential components is 0%.

[0069] The preferred crystalline glass is a lithium aluminum silicate glass containing SiO2, Al2O3, and Li2O. Since lithium aluminum silicate glass contains lithium ions, which are the smallest alkali ions, chemically strengthened glasses with a preferred stress distribution can be easily obtained through chemical strengthening treatment involving ion exchange using various molten salts.

[0070] Furthermore, from the viewpoint of including different elements in the Li ion sites of lithium disilicate crystals and reducing the proportion of Li ions, it is preferable to include elements such as Na and Al, whose valence numbers are close to those of Li, in the glass composition.

[0071] The glass composition of this crystallized glass will be further described in detail below.

[0072] SiO2 is a component constituting lithium disilicate crystals and is an essential component. SiO2 forms the network of the glass and also contributes to improving chemical durability. The SiO2 content is preferably 55-85%. From the viewpoint of precipitating lithium disilicate crystals and improving chemical durability, the SiO2 content is preferably 55% or more, more preferably 57.5% or more, further preferably 60% or more, even more preferably 62.5% or more, particularly preferably 65% ​​or more, even more preferably 66% or more, further preferably 67% or more, even more preferably 68% or more, especially preferably 69% or more, and most preferably 70% or more. To improve meltability during glass manufacturing, the SiO2 content is preferably 85% or less, more preferably 82.5% or less, further preferably 80% or less, even more preferably 79% or less, particularly preferably 78% or less, especially preferably 77% or less, further preferably 76% or less, even more preferably 75% or less, and most preferably 74% or less.

[0073] From the viewpoint of improving ion exchange performance during chemical strengthening and increasing surface compressive stress after strengthening, Al2O3 is an effective component. Al2O3 is also a component that improves chemical durability. Furthermore, Al is an element that can exist as a heteroelement in the Li ion sites of lithium disilicate crystals. The content of Al2O3 is preferably 1-5%. To improve chemical durability and chemical strengthening properties, the content of Al2O3 is preferably 1% or more, more preferably 1.5% or more, further preferably 2% or more, particularly preferably 2.5% or more, further preferably 3% or more, further preferably 3.5% or more, and most preferably 4% or more. From the viewpoint of suppressing excessive precipitation of other crystals, the content of Al2O3 is preferably 5% or less, more preferably 4.9% or less, further preferably 4.8% or less, particularly preferably 4.7% or less, and even more preferably 4.6% or less.

[0074] Li₂O is a component of lithium disilicate crystals and is an essential component. Li₂O contributes to surface compressive stress through ion exchange and also improves the melt permeability of the glass. By incorporating Li₂O into the crystalline glass, and through ion exchange of Li ions on the glass surface to Na ions, and then further ion exchange of Na ions to K ions, a stress distribution with high surface compressive stress and a high compressive stress layer is obtained. The Li₂O content is preferably 15-25%. From the viewpoint of precipitating lithium disilicate crystals and improving strength through chemical strengthening, the Li₂O content is preferably 15% or more, more preferably 16% or more, further preferably 17% or more, particularly preferably 18% or more, further preferably 19% or more, and most preferably 20% or more. On the other hand, for glass stability, the Li₂O content is preferably 25% or less, more preferably 24.5% or less, further preferably 24% or less, particularly preferably 23.5% or less, further preferably 23% or less, and most preferably 22.5% or less.

[0075] Neither Na₂O nor K₂O are essential components, but they are components that improve the meltability of the glass and its ion exchange performance. To achieve these effects, this crystalline glass may contain at least one of Na₂O and K₂O.

[0076] Na₂O is a component that forms a surface compressive stress layer during chemical strengthening treatment using potassium salts, and it is also a component that can improve the meltability of glass. Furthermore, Na is an element that can exist as a heteroelement in the Li ion sites of lithium disilicate crystals. The Na₂O content is preferably 0 to 5.0%, more preferably 0.1 to 5.0%. When the crystalline glass contains Na₂O, the content is preferably 0.1% or more, more preferably 0.25% or more, further preferably 0.5% or more, particularly preferably 0.75% or more, further preferably 1.0% or more, and most preferably 1.25% or more. On the other hand, if the Na₂O content is too high, it may be difficult to increase the compressive stress in the deeper portions of the surface due to chemical strengthening. From this viewpoint, the Na₂O content is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less.

[0077] K₂O is a component that improves the meltability of glass and also enhances its ion exchange performance. The K₂O content is preferably 0 to 5.0%. From the viewpoint of achieving this effect, the K₂O content in this crystalline glass is preferably 0% or more, more preferably 0.1% or more. From the viewpoint of suppressing the reduction of chemical strengthening properties and chemical durability, the K₂O content is preferably 5.0% or less, more preferably 4.5% or less, further preferably 3.5% or less, even more preferably 3.0% or less, particularly preferably 2.5% or less, further particularly preferably 2.0% or less, further preferably 1.5% or less, further preferably 1.0% or less, and most preferably 0.5% or less.

[0078] The combined content of Na₂O and K₂O is preferably 0-10%. When the crystalline glass contains at least one of Na₂O and K₂O, from the viewpoint of improving the glass's meltability and ion exchange performance, the combined content of Na₂O and K₂O is preferably 0.2% or more, more preferably 0.25% or more, further preferably 0.5% or more, even more preferably 0.75% or more, particularly preferably 1.0% or more, further preferably 1.25% or more, and most preferably 1.5% or more. From the viewpoint of suppressing the reduction of chemical strengthening properties and chemical durability, the combined content of Na₂O and K₂O is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, particularly preferably 5% or less, further preferably 4% or less, and most preferably 3% or less.

[0079] MgO, CaO, SrO, and BaO are not essential components, but they are components that can improve the stability of the glass and enhance its chemical strengthening properties. This crystalline glass may contain one or more of MgO, CaO, SrO, and BaO. The total content of one or more of MgO, CaO, SrO, and BaO is preferably 0 to 5.0%. When these components are present, the total content of one or more of MgO, CaO, SrO, and BaO is preferably 0% or more, more preferably 0.25% or more, further preferably 0.5% or more, particularly preferably 1.0% or more, further particularly preferably 1.25% or more, further preferably 1.5% or more, further preferably 1.75% or more, and most preferably 2.0% or more. From the viewpoint of applying sufficient compressive stress during chemical strengthening and improving radio wave transmittance, the total content of these components is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less.

[0080] To reduce viscosity during melting, this crystalline glass may contain MgO. The MgO content is preferably 0 to 5.0%. When the crystalline glass contains MgO, the MgO content is preferably 0% or more, more preferably 0.25% or more, further preferably 0.5% or more, particularly preferably 1.0% or more, further particularly preferably 1.25% or more, further preferably 1.5% or more, further preferably 1.75% or more, and most preferably 2.0% or more. From the viewpoint of suppressing the reduction of chemical strengthening properties, the MgO content is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less.

[0081] CaO is a component that improves the meltability of glass. This crystalline glass may contain CaO. The CaO content is preferably 0 to 5.0%. When this crystalline glass contains CaO, the CaO content is preferably 0% or more, more preferably 0.25% or more, further preferably 0.5% or more, particularly preferably 1.0% or more, further particularly preferably 1.25% or more, further preferably 1.5% or more, further preferably 1.75% or more, and most preferably 2.0% or more. From the viewpoint of suppressing the reduction of chemical strengthening properties, the CaO content is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less.

[0082] ZnO is not an essential component, but it is a component that can improve the meltability of the glass. This crystalline glass may contain ZnO. The ZnO content is preferably 0 to 5.0%. When this crystalline glass contains ZnO, the ZnO content is preferably 0% or more, more preferably 0.25% or more, further preferably 0.5% or more, particularly preferably 1.0% or more, further particularly preferably 1.25% or more, further preferably 1.5% or more, further preferably 1.75% or more, and most preferably 2.0% or more. From the viewpoint of improving durability, the ZnO content is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less.

[0083] The total content of ZnO, SrO, and BaO, [ZnO] + [SrO] + [BaO], is preferably 0 to 5.0%. ZnO, SrO, and BaO tend to deteriorate chemical fortification properties; therefore, to facilitate chemical fortification, [ZnO] + [SrO] + [BaO] is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, particularly preferably 3.5% or less, even more preferably 3.0% or less, and most preferably 2.5% or less. On the other hand, the total content of these components is preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.5% or more, particularly preferably 0.7% or more, even more particularly preferably 1.0% or more, and even more preferably 1.2% or more.

[0084] P2O5 is the component that forms the nucleus of lithium disilicate crystals. From the viewpoint of precipitating lithium disilicate crystals, the content of P2O5 is preferably 0.5% to 5.0%. The content of P2O5 is preferably 0.5% or more, more preferably 0.6% or more, further preferably 0.7% or more, particularly preferably 0.8% or more, further particularly preferably 0.9% or more, further preferably 1.0% or more, further preferably 1.1% or more, and most preferably 1.2% or more. From the viewpoint of improving acid resistance, the content of P2O5 is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further particularly preferably 3.0% or less, further preferably 2.5% or less, further preferably 2.0% or less, and most preferably 1.5% or less.

[0085] TiO2 is a component that can suppress the effects of sunlight on glass, but it can also serve as a nucleus for other crystals. The TiO2 content is preferably 0-5.0%. From the viewpoint of suppressing excessive precipitation of other crystals, the TiO2 content is preferably 5.0% or less, more preferably 4.5% or less, particularly preferably 4.0% or less, further preferably 3.5% or less, even more preferably 3.0% or less, and most preferably 2.5% or less. This crystalline glass may substantially not contain TiO2. When this crystalline glass contains TiO2, the TiO2 content is preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.5% or more, particularly preferably 0.7% or more, even more preferably 1.0% or more, and most preferably 1.2% or more.

[0086] ZrO2 is a component that can increase the surface compressive stress of chemically strengthened glass, but it can also serve as a nucleus for other crystals such as lithium feldspar crystals. The ZrO2 content is preferably 0 to 5.0%. From the viewpoint of suppressing excessive precipitation of other crystals, the ZrO2 content is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, even more preferably 3.5% or less, most preferably 3.0% or less, particularly preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.8% or less, even more preferably 1.6% or less, especially preferably 1.4% or less, and most preferably 1.2% or less. This crystalline glass may substantially not contain ZrO2. From the viewpoint of reducing crystal size, the ZrO2 content in the crystal glass is preferably 0% or more, more preferably 0.1% or more, even more preferably 0.2% or more, even more preferably 0.3% or more, particularly preferably 0.4% or more, even more preferably 0.5% or more, even more preferably 0.6% or more, even more preferably 0.7% or more, especially preferably 1.0% or more, and most preferably 1.1% or more.

[0087] When the crystalline glass contains at least one of TiO2 and ZrO2, the ratio of the total content of TiO2 and ZrO2 to the content of P2O5 (TiO2+ZrO2) / P2O5 is preferably 0 to 2.5. From the viewpoint of suppressing excessive precipitation of other crystals, (TiO2+ZrO2) / P2O5 is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.8 or less, particularly preferably 1.6 or less, even more preferably 1.4 or less, and most preferably 1.2 or less. From the viewpoint of reducing crystal size, (TiO2+ZrO2) / P2O5 is preferably 0 or more, more preferably 0.1 or more, even more preferably 0.2 or more, particularly preferably 0.3 or more, even more preferably 0.4 or more, even more preferably 0.5 or more, and most preferably 0.6 or more.

[0088] B2O3 is not an essential component, but it is a component that can reduce the brittleness of the glass, improve its crack resistance, and improve its radio wave transmittance. This crystalline glass may contain B2O3. The content of B2O3 is preferably 0 to 5.0%. When this crystalline glass contains B2O3, the content is preferably 0.2% or more, more preferably 0.4% or more, further preferably 0.6% or more, particularly preferably 0.8% or more, further preferably 1.0% or more, and most preferably 1.2% or more. From the viewpoint of improving acid resistance, the content of B2O3 is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less.

[0089] Nb₂O₅, Ta₂O₅, Gd₂O₃, and CeO₂ are components that suppress the effects of sunlight on glass and improve its melt properties. This crystalline glass may contain at least one of these components. The total content of these components is preferably 0 to 3%. When this crystalline glass contains these components, the total content is preferably 0.03% or more, more preferably 0.1% or more, further preferably 0.3% or more, particularly preferably 0.5% or more, further preferably 0.8% or more, and most preferably 1% or more. On the other hand, if these contents are too high, it is difficult to increase the compressive stress value during chemical strengthening treatment. According to this viewpoint, the total content of these components is preferably 3% or less, more preferably 2.5% or less, further preferably 2% or less, particularly preferably 1.5% or less, further preferably 1% or less, and most preferably 0.5% or less.

[0090] Fe2O3 is a component that can improve the meltability of glass by absorbing heat rays. The Fe2O3 content is preferably 0 to 0.3% by weight (based on oxides). When producing glass in large quantities using a large melting furnace, this crystalline glass preferably contains Fe2O3. In this case, the Fe2O3 content is preferably 0.002% or more, more preferably 0.003% or more, further preferably 0.005% or more, particularly preferably 0.007% or more, further preferably 0.008% or more, and most preferably 0.01% or more (based on oxides). On the other hand, excessive Fe2O3 can cause coloration; therefore, from the viewpoint of improving the transparency of the glass, this content is preferably 0.3% or less (based on oxides), more preferably 0.04% or less, further preferably 0.03% or less, particularly preferably 0.025% or less, further preferably 0.02% or less, and most preferably 0.015% or less.

[0091] It should be noted that, in this description, all iron oxides in the glass are assumed to be Fe2O3. In reality, Fe(III) in its oxidized state and Fe(II) in its reduced state usually coexist. Fe(III) produces a yellow color, while Fe(II) produces a blue color. The balance between the two results in a green color in the glass.

[0092] Furthermore, the crystal glass may contain coloring components within a range that does not impede the effects of the present invention. Examples of preferred coloring components include Co3O4, MnO2, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, CeO2, Er2O3, and Nd2O3.

[0093] The content of the coloring components, expressed as a molar percentage based on oxides, is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, particularly preferably 2% or less, and even more preferably 1% or less. Ideally, these components should be substantially absent if it is desired to improve the transmittance of the glass.

[0094] As a clarifying agent during glass melting, it may appropriately contain SO3, chlorides, fluorides, etc. It is preferable that it does not contain As2O3. If it does contain Sb2O3, its content is preferably 0.3% or less, more preferably 0.1% or less, and most preferably does not contain Sb2O3.

[0095] There are no specific examples of preferred glass compositions for this crystalline glass; for example, the following can be cited.

[0096] Expressed as a molar percentage based on oxides, it contains 55-85% SiO2, 1-5% Al2O3, 0-5.0% B2O3, 0.5-5.0% P2O5, 0-5.0% TiO2, 0-5.0% ZrO2, 15-25% Li2O, 0-5.0% Na2O, and 0-5.0% K2O, and contains a total of 0-5.0% of one or more selected from MgO, CaO, SrO, and BaO.

[0097] Furthermore, from the viewpoint of further improving chemical strengthening properties and making it easier for dissimilar elements to exist in the Li ion sites of lithium disilicate crystals, the following glass composition is more preferred.

[0098] Expressed as molar percentages based on oxides, it contains SiO2 55–85%, Al2O3 1–5%, B2O3 0–5.0%, P2O5 0.5–5.0%, TiO2 0–5.0%, ZrO2 0–5.0%, Li2O 15–25%, Na2O 0.1–5.0%, and K2O 0–5.0%.

[0099] It contains a total of 0 to 5.0% of one or more selected from MgO, CaO, SrO and BaO.

[0100] (physical properties)

[0101] The relative permittivity Dk of this crystalline glass at 20°C and 10GHz is preferably 5.8 or less, more preferably 5.7 or less, even more preferably 5.6 or less, particularly preferably 5.5 or less, even more particularly preferably 5.4 or less, even more preferably 5.3 or less, and most preferably 5.2 or less. By making the relative permittivity Dk small, the loss of electromagnetic waves caused by reflection at the glass surface can be suppressed, thus easily achieving good electromagnetic wave transmittance. There is no particular limitation on the lower limit of the relative permittivity Dk, but it is typically 4.0 or more. For example, the relative permittivity Dk can be 4.0 to 5.8.

[0102] The dielectric loss tangent tanδ of this crystalline glass at 20°C and 10GHz is preferably 0.01 or less, more preferably 0.009 or less, even more preferably 0.008 or less, particularly preferably 0.007 or less, even more preferably 0.006 or less, and most preferably 0.0055 or less. By making the dielectric loss tangent tanδ small, the loss of electromagnetic waves passing through the interior of the glass can be suppressed, thus easily improving electromagnetic wave transmittance. There is no particular limitation on the lower limit of the dielectric loss tangent, but it is typically 0.0005 or more. The dielectric loss tangent tanδ can be, for example, 0.0005 to 0.01.

[0103] The sum of the value obtained by multiplying the dielectric loss tangent tanδ of the crystal glass at 20°C and 10GHz by 100 (tanδ×100) and the relative permittivity Dk at 20°C and 10GHz is preferably 7.5 or less, more preferably 7.25 or less, further preferably 7.0 or less, even more preferably 6.75 or less, particularly preferably 6.5 or less, further particularly preferably 6.25 or less, further preferably 6.0 or less, further preferably 5.9 or less, and most preferably 5.8 or less. This sum is an adjustment made by adjusting the relative permittivity Dk and the dielectric loss tangent tanδ in such a way that their respective contributions are equal. Since both the relative permittivity Dk and the dielectric loss tangent tanδ are small, the electromagnetic wave transmittance is improved. Therefore, the smaller this sum is, the better the electromagnetic wave transmittance can be judged. There is no particular limitation on the lower limit of this sum, which is typically 4.5 or more. This sum can be, for example, 4.5 to 7.5.

[0104] It should be noted that by making the relative permittivity and dielectric loss tangent values ​​at 20°C and 10GHz close to those at higher frequencies, the frequency dependence (dielectric dispersion) is reduced, and the frequency characteristics of the dielectric properties are less prone to change. Even when the frequency of use is different, only a small design change is required, so it is preferred.

[0105] In this crystalline glass, the most abundant crystal by mass is the lithium disilicate crystal. In the lithium disilicate crystal, the proportion of Li ions in the Li ion sites is relatively small, resulting in a small relative permittivity Dk and dielectric loss tangent tanδ at 20℃ and 10GHz, and excellent electromagnetic wave transmittance.

[0106] It should be noted that, typically within the frequency range of 10GHz to 40GHz, the relative permittivity and dielectric loss tangent of glass exhibit little frequency dependence. Therefore, this glass, which has excellent dielectric properties at 10GHz, also exhibits excellent radio wave transmittance in the 28GHz and 35GHz frequency bands used in 5G.

[0107] The relative permittivity and dielectric loss tangent can be determined using a network analyzer via the split column dielectric resonator method (SPDR method).

[0108] This crystalline glass, especially when used as a protective glass, preferably exhibits high transparency. By achieving a parallel transmittance of 85% or more (converted to a thickness of 0.7 mm) in the wavelength range of 400 nm to 1000 nm, this crystalline glass facilitates easy viewing of the display image when used as a protective glass for portable displays. The parallel transmittance is more preferably 85.5% or more, further preferably 86% or more, even more preferably 86.5% or more, particularly preferably 87% or more, further preferably 87.5% or more, most preferably 88% or more, further preferably 88.5% or more, further preferably 89% or more, especially preferably 89.5% or more, very preferably 90% or more, and most preferably 90.5% or more. Higher parallel transmittance is preferable; typically, it is preferably 98% or less, more preferably 96% or less, further preferably 95% or less, particularly preferably 94% or less, further preferably 93.5% or less, more preferably 93% or less, and most preferably 92.5% or less. Converted to a parallel light transmittance of 0.7mm thickness, it can be, for example, 85-98%.

[0109] It should be noted that if the parallel transmittance of a crystal glass with a thickness of 0.75 mm or more is 85% or more, then the parallel transmittance calculated for a thickness of 0.7 mm is also considered to be 85% or more. Furthermore, for crystal glasses with a thickness t greater than 0.7 mm, the thickness can be adjusted to 0.7 mm through grinding, etching, etc., and the parallel transmittance can be measured in practice.

[0110] This crystalline glass preferably has high transparency. Even when the thickness of this crystalline glass is not 0.7 mm, and even with a large thickness, by ensuring that the parallel transmittance is preferably 85% or more in the wavelength range of 400 nm to 1000 nm, the image on the display is easily visible when used as protective glass for portable displays. For example, when the thickness is preferably 0.7 mm or more, more preferably 0.8 mm or more, further preferably 0.9 mm or more, even more preferably 1.0 mm or more, particularly preferably 1.2 mm or more, further preferably 1.5 mm or more, and most preferably 2.0 mm or more, the parallel transmittance is preferably 85% or more. Furthermore, chemically strengthened glass is typically used with a thickness of 2.0 mm or less.

[0111] Furthermore, the haze value converted to a thickness of 0.7 mm is preferably less than 5% in the wavelength range of 400 nm to 1000 nm, more preferably less than 4%, further preferably less than 3%, even more preferably less than 2%, particularly preferably less than 1%, further particularly preferably less than 0.9%, most preferably less than 0.8%, further preferably less than 0.7%, further preferably less than 0.6%, especially preferably less than 0.5%, very preferably less than 0.4%, and most preferably less than 0.3%. A lower haze value is preferred, as reducing the haze value, crystallinity, or crystal grains can easily lead to a decrease in mechanical strength. To improve mechanical strength, the haze value converted to a thickness of 0.7 mm is preferably 0.05% or more, more preferably 0.1% or more, further preferably 0.15% or more, particularly preferably 0.2% or more, and even more preferably 0.25% or more. For example, the haze value converted to a thickness of 0.7 mm can be 0.05% or more and less than 5%. The haze value was measured according to JIS K7136 (2000).

[0112] It should be noted that the haze value of a crystal glass with a plate thickness of t [mm] can be calculated using the following steps.

[0113] First, given a crystal glass with a thickness of t [mm], a total visible light transmittance of 100 × T [%), and a single-sided surface reflectance of 100 × R [%), by invoking the Lambert-Beer law, and using the constant α, we have T = (1 - R). 2 The relationship between ×exp(-αt).

[0114] Therefore, let R, T, and t represent α. If we set t = 0.7 mm, then R does not change with the plate thickness. Therefore, the total visible light transmittance T converted to 0.7 mm is... 0.7 It can be calculated as T 0.7 =100×T 0.7 / t / (1-R)^(1.4 / t-2)[%]. Where “X^Y” represents “X”. Y Furthermore, surface reflectivity can be calculated based on refractive index or measured in practice.

[0115] Furthermore, given a crystal glass with a thickness of t [mm] and a total visible light transmittance of 100 × T [%) and a haze value of 100 × H [%), by invoking the Lambert-Beer law and using the aforementioned constant α,

[0116] dH / dt∝exp(-αt)×(1-H).

[0117] This means that the haze value is assumed to increase proportionally with the internal linear transmittance as the plate thickness increases. Therefore, the haze value H at 0.7 mm is... 0.7 It can be obtained through the following formula. Where "X^Y" represents "X". Y ".

[0118] H 0.7 =100×[1-(1-H)^{((1-R) 2 -T 0.7 ) / ((1-R) 2 -T)}][%]

[0119] In addition, for glass with a thickness t greater than 0.7 mm, the thickness can be adjusted to 0.7 mm through grinding, etching, etc., and the haze value can be measured.

[0120] Crystalline glass contains crystals, thus exhibiting high hardness. Therefore, it is not easily damaged and possesses excellent wear resistance. The Vickers hardness is preferably 600–1100. To further increase wear resistance, the Vickers hardness is preferably 600 or higher, more preferably 650 or higher, even more preferably 700 or higher, particularly preferably 730 or higher, even more preferably 750 or higher, and most preferably 780 or higher.

[0121] If the hardness is too high, it tends to be difficult to process. Therefore, the Vickers hardness of the crystal glass is preferably below 1100, more preferably below 1080, further preferably below 1060, particularly preferably below 1050, even more preferably below 1030, and most preferably below 1000.

[0122] The Young's modulus of the crystal glass is preferably 85–130 GPa. To suppress warping caused by chemical strengthening, the Young's modulus is preferably 85 GPa or higher, more preferably 90 GPa or higher, even more preferably 93 GPa or higher, particularly preferably 95 GPa or higher, even more preferably 97 GPa or higher, and most preferably 100 GPa or higher. Crystal glass is sometimes used after grinding. For ease of grinding, the Young's modulus is preferably 130 GPa or lower, more preferably 127 GPa or lower, even more preferably 125 GPa or lower, particularly preferably 123 GPa or lower, and even more preferably 120 GPa or lower.

[0123] The preferred fracture toughness value of crystal glass is 0.8 MPa·m. 1 / 2 The above, more preferably 0.83 MPa·m 1 / 2 The above is further preferably 0.85 MPa·m 1 / 2 The above, particularly preferred, is 0.87 MPa·m 1 / 2 The above is further preferably 0.9 MPa·m 1 / 2 When chemically strengthened, the fragments are less likely to scatter during fracture, making it a preferred option. There is no specific upper limit to the fracture toughness value; a typical value is 1.5 MPa·m. 1 / 2 The fracture toughness value can be, for example, 0.8–1.5 MPa·m. 1 / 2 .

[0124] (shape)

[0125] The shape of this crystalline glass is not particularly limited, but it is preferably plate-shaped. When the crystalline glass is plate-shaped (glass plate), its plate thickness (t) is preferably 0.1 to 2 mm. From the viewpoint of improving the effect of chemical strengthening, the plate thickness (t) is preferably 2 mm or less, preferably 1.5 mm or less, more preferably 1 mm or less, further preferably 0.9 mm or less, even more preferably 0.8 mm or less, particularly preferably 0.7 mm or less, and most preferably 0.6 mm or less. Furthermore, from the viewpoint of obtaining a sufficient increase in strength due to chemical strengthening treatment, the plate thickness is preferably 0.1 mm or more, more preferably 0.2 mm or more, further preferably 0.3 mm or more, even more preferably 0.35 mm or more, particularly preferably 0.4 mm or more, and even more particularly preferably 0.5 mm or more.

[0126] The shape of this crystalline glass can be other than a plate shape, depending on the product and application. Furthermore, the glass plate can also have edging with varying thicknesses around its perimeter. The shape of the glass plate is not limited to these features; for example, the two main surfaces may not be parallel. Additionally, one or all or part of one or both main surfaces may be curved. More specifically, the glass plate can be, for example, a flat, warp-free plate, or a curved glass plate with a curved surface.

[0127] (Chemically strengthened glass)

[0128] The chemically strengthened glass of the present invention (hereinafter also referred to as "this chemically strengthened glass") is obtained by chemically strengthening the above-described crystalline glass. That is, the basic composition of this chemically strengthened glass is the same as the glass composition of the described crystalline glass, and the preferred composition range is also the same. In the case where the chemically strengthened glass is, for example, in a plate shape, the content ratio of alkali metal elements differs between the surface and the center in the thickness direction. On the other hand, except in cases where extreme ion replacement treatment has been performed, the glass composition of the deepest part of the chemically strengthened glass from the surface is the same as the basic composition of the chemically strengthened glass. In the case where the chemically strengthened glass is in a plate shape, the deepest part from the glass surface refers to, for example, a depth of 1 / 2 of the plate thickness t.

[0129] This chemically strengthened glass is, for example, a chemically strengthened glass having a compressive stress layer on its surface, and is a chemically strengthened glass having a surface compressive stress value CS of 50 MPa or more and being the aforementioned crystalline glass.

[0130] By chemically strengthening this crystalline glass, its strength can be improved. Furthermore, it is believed that the crystals contained in this chemically strengthened glass, their content, and the proportion of Li ions in the Li ion sites of the lithium disilicate crystals are the same as those in the crystalline glass, except in cases of extreme ion exchange treatment. That is, for the same reasons as the crystalline glass, this chemically strengthened glass exhibits excellent electromagnetic transmittance. In addition, this chemically strengthened glass excels in both strength and electromagnetic transmittance.

[0131] The surface compressive stress (CS) of this chemically strengthened glass is preferably 50–400 MPa. CS is preferably 50 MPa or higher, more preferably 60 MPa or higher, even more preferably 70 MPa or higher, even more preferably 80 MPa or higher, particularly preferably 90 MPa or higher, even more preferably 100 MPa or higher, even more preferably 110 MPa or higher, even more preferably 130 MPa or higher, and most preferably 150 MPa or higher.

[0132] A higher surface compressive stress value (CS) results in higher strength. However, excessively high CS can generate large tensile stresses within the chemically strengthened glass, potentially leading to failure. Therefore, the surface compressive stress value (CS) is preferably below 400 MPa, more preferably below 350 MPa, even more preferably below 300 MPa, particularly preferably below 250 MPa, even more preferably below 225 MPa, and most preferably below 200 MPa.

[0133] In the stress distribution of this chemically strengthened glass, the compressive stress value CS at a depth of 50 μm measured from the surface is... 50 Preferably, the pressure is 5–100 MPa. CS 50 Preferably, it is 5 MPa or higher, more preferably 10 MPa or higher, particularly preferably 15 MPa or higher, further preferably 20 MPa or higher, and most preferably 25 MPa or higher. By making CS... 50 Larger diameters make chemically strengthened glass less prone to breakage when damaged by falls or other impacts. From the perspective of preventing violent breakage, CS... 50 Preferably, the pressure is 100 MPa or less, more preferably 90 MPa or less, even more preferably 80 MPa or less, particularly preferably 70 MPa or less, even more preferably 60 MPa or less, even more preferably 50 MPa or less, and most preferably 40 MPa or less.

[0134] The internal tensile stress (CT) value of this chemically strengthened glass is preferably 5 to 100 MPa. CT is preferably below 100 MPa, more preferably below 75 MPa, further preferably below 50 MPa, particularly preferably below 40 MPa, further preferably below 30 MPa, and most preferably below 20 MPa. Because the CT is low, breakage is less likely. The internal tensile stress (CT) value is preferably 5 MPa or higher, more preferably 10 MPa or higher, particularly preferably 15 MPa or higher, and further preferably 17.5 MPa or higher. Because the CT is above these values, the compressive stress near the surface increases, resulting in higher strength.

[0135] The compressive stress layer depth (DOL) of this chemically strengthened glass relative to its thickness (t) is preferably 0.04t to 0.22t. When the DOL is too large relative to the thickness (t) (mm), it leads to an increase in the compressive stress layer (CT). Therefore, it is preferably 0.22t or less, more preferably 0.21t or less, even more preferably 0.20t or less, particularly preferably 0.19t or less, even more preferably 0.18t or less, even more preferably 0.16t or less, even more preferably 0.14t or less, and most preferably 0.12t or less. Furthermore, from the viewpoint of improving strength, the DOL is preferably 0.04t or more, more preferably 0.05t or more, particularly preferably 0.06t or more, even more preferably 0.07t or more, even more preferably 0.08t or more, and most preferably 0.09t or more. Specifically, for example, when the plate thickness (t) is 0.7mm, the DOL is preferably 63μm or less, more preferably 56μm or less, and even more preferably 49μm or less. Furthermore, the DOL is preferably 28 μm or more, more preferably 35 μm or more, and particularly preferably 42 μm or more. It should be noted that the preferred thickness (t) and preferred shape of this chemically strengthened glass are the same as the preferred thickness (t) and preferred shape of the crystalline glass described above.

[0136] <Manufacturing methods for crystallized glass and chemically strengthened glass>

[0137] This chemically strengthened glass can be manufactured by chemically strengthening the aforementioned crystalline glass. Alternatively, this crystalline glass can be manufactured by crystallizing amorphous glass through heat treatment.

[0138] (Manufacturing of amorphous glass)

[0139] Amorphous glass can be manufactured, for example, by the following methods. It should be noted that the manufacturing methods described below are examples of those used in the manufacture of sheet-like crystalline glass and chemically strengthened glass.

[0140] Glass raw materials are prepared to obtain glass with a preferred composition, and then heated and melted in a glass melting furnace. The molten glass is then homogenized by bubbling, stirring, and adding a clarifying agent, 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, slowly cooling it, and then cutting it.

[0141] Here, the preferred glass composition of the amorphous glass is the same as the preferred glass composition of the crystalline glass described above.

[0142] (Crystallization treatment)

[0143] Crystalline glass is obtained by heating the amorphous glass obtained from the above steps.

[0144] The method of heat treatment is not particularly limited, as long as it includes at least one stage of heat treatment on the amorphous glass. The following methods are preferred, for example, for heat treatment.

[0145] The heat treatment can also be carried out in two stages: first, heating from room temperature to a first treatment temperature T1 and holding it for a certain time (holding time t1), and then holding it at a second treatment temperature T2, which is higher than the first treatment temperature, for a certain time (holding time t2). Alternatively, it can be carried out in one stage: holding it at a specific treatment temperature and then cooling it to room temperature.

[0146] In the case of using a two-stage heating process, the first processing temperature T1 is preferably in the temperature range where the rate of crystal nucleation in the glass composition increases, and the second processing temperature T2 is preferably in the temperature range where the rate of crystal growth in the glass composition increases. Furthermore, the holding time t1 at the first processing temperature T1 is preferably a relatively long time to produce a sufficient number of crystal nuclei. By generating a large number of crystal nuclei, the size of each crystal becomes smaller, making it easier to obtain a crystalline glass with high transparency.

[0147] When using a two-stage heating process, the first treatment temperature T1 is preferably 450°C to 700°C, and the holding time t1 is preferably 1 hour to 6 hours. The second treatment temperature is preferably 600°C to 800°C, and the holding time t2 is preferably 1 hour to 6 hours. When using a single-stage process, it is preferably held at 500°C to 800°C for 1 hour to 6 hours.

[0148] Furthermore, there is no particular limitation on the method for making the proportion of Li ions in the Li ion sites of lithium disilicate crystals small, but a method that satisfies at least one of the following first and second conditions is preferred.

[0149] As a primary condition, it is preferable to perform the heat treatment at a relatively low temperature. Specifically, in one or more stages of heat treatment, it is preferable that the temperature of each stage is below 750°C, more preferably below 740°C, further preferably below 730°C, and particularly preferably below 720°C. It should be noted that the preferred lower limit of the heat treatment temperature is the same as described above.

[0150] By setting the heat treatment temperature to a lower level, Li ions are made less likely to move easily within the glass and thus less likely to exist at Li ion sites. This reduces the proportion of Li ions at Li ion sites.

[0151] As a second condition, it is preferable to have a relatively high heating rate and cooling rate. That is, in one or more stages of heat treatment, the heating rate to each treatment temperature is preferably 0.5 to 100°C / min. The heating rate is preferably 0.5°C / min or more, more preferably 1°C / min or more, further preferably 2°C / min or more, particularly preferably 3°C / min or more, further preferably 4°C / min or more, and most preferably 5°C / min or more. On the other hand, from the viewpoint of suppressing glass breakage, the heating rate is preferably 100°C / min or less, more preferably 75°C / min or less, further preferably 50°C / min or less, and particularly preferably 25°C / min or less. When the heat treatment consists of multiple stages, it is preferable that at least a portion of the heating rate is within the above range, and more preferably that all of the heating rates are within the above range. The preferred method for the cooling rate from each treatment temperature is the same as the preferred method for the heating rate.

[0152] By making the heating and cooling rates relatively high, Li ions are less likely to move within the glass during heating or cooling, and are less likely to exist in Li ion sites. This reduces the proportion of Li ions in the Li ion sites.

[0153] Alternatively, the molten glass can be homogenized and formed into a glass plate of a specified thickness, or the molten glass can be formed into a block and then continuously crystallized.

[0154] When heat-treating sheet-shaped glass, suitable firing plates include, for example, silicon carbide plates, silicon nitride plates, SiN plates, alumina plates, mullite cordierite plates, mullite plates, and crystal glass plates. Furthermore, to reduce temperature unevenness during heat treatment, materials with high thermal conductivity are preferred. The thermal conductivity of the firing plate is preferably 2 W / (m·K) or higher, more preferably 20 W / (m·K) or higher, and even more preferably 40 W / (m·K) or higher.

[0155] To prevent the glass from sticking to the firing plate, a release agent can be used. Examples of release agents include alumina cloth and glass cloth. Other examples include powdered boron nitride, alumina, and minerals. The powdered release agent can be mixed with a solvent and applied by spraying or the like. When using particulate particles, the average particle size is preferably 80 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less.

[0156] To improve work efficiency, glass can be laminated during heat treatment. When laminating, it is preferable to use a release agent between the glass panes. Alternatively, a firing plate can be placed between the glass panes.

[0157] The crystalline glass obtained through the above steps is ground and polished as needed to form a crystalline glass plate. If the crystalline glass plate is cut into a specified shape and size, or if it is chamfered, cutting or chamfering is performed before chemical strengthening treatment, a compressive stress layer will also be formed on the end face after the subsequent chemical strengthening treatment, which is therefore preferred.

[0158] (Chemical enhancement treatment)

[0159] Chemical strengthening treatment involves immersing the glass in a molten metal salt (such as potassium nitrate) containing metal ions with large ionic radii, thereby bringing the glass into contact with the metal salt and displacing the smaller metal ions with the larger ones. Typically, the smaller metal ions are Na or Li ions. The larger metal ions are typically Na or K ions; more specifically, Na or K ions relative to Li ions, and K ions relative to Na ions.

[0160] 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.

[0161] 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.

[0162] 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 is preferable to perform chemical strengthening treatment on the crystalline glass at a temperature preferably below 450°C for a period of preferably less than 1 hour. Specifically, an example is immersion in a molten salt (e.g., a mixture of lithium nitrate and sodium nitrate) preferably containing 0.3% by mass of Li and 99.7% by mass of Na at a temperature preferably 450°C for approximately 0.5 hours.

[0163] Chemical strengthening treatment can be achieved, for example, through a two-stage ion exchange process. First, the crystalline glass is immersed in a Na-containing metal salt (e.g., sodium nitrate) at a temperature preferably around 350–500°C for approximately 0.1–10 hours. This results in ion exchange between Li ions in the crystalline glass and Na ions in the metal salt, forming a deeper compressive stress layer.

[0164] Next, the sample is immersed in a metal salt containing K ions (e.g., potassium nitrate) at a temperature preferably around 350–500°C for approximately 0.1–10 hours. This results in high compressive stress in portions of the compressive stress layer formed in the previous treatment, for example, up to a depth of approximately 10 μm. Based on this two-stage treatment, a stress distribution with high surface compressive stress values ​​is readily obtained.

[0165] (use)

[0166] This invention relates to an electronic device incorporating the aforementioned crystalline glass or chemically strengthened glass. Both the crystalline glass and the chemically strengthened glass offer a balance of high strength and electromagnetic transmittance, making them useful as protective glass and circuit boards for use in electronic devices. The crystalline glass and the chemically strengthened glass are particularly useful as protective glass for mobile devices such as mobile phones, smartphones, portable information terminals (PDAs), and tablet computers. Furthermore, the crystalline glass and the chemically strengthened glass are useful as protective glass for display devices such as televisions (TVs), personal computers (PCs), and touch panels that are not intended for portability; as building materials such as elevator walls, walls of houses or buildings (full-screen displays), and window glass; as desktops; and as interior decoration for automobiles and aircraft. They are also useful in applications such as housings with non-plate-like curved shapes achieved through bending and molding.

[0167] Example

[0168] The following examples illustrate the present invention in detail, but the present invention is not limited thereto.

[0169] The glass raw materials were prepared to the composition shown in Table 1 as a molar percentage based on oxides, and weighed to obtain 400g of glass. Next, the mixed raw materials were placed in a platinum crucible and put into an electric furnace at 1500℃~1700℃, and melted for about 3 hours to remove bubbles and homogenize.

[0170] The molten glass obtained is poured into a metal mold and held at a temperature approximately 50°C higher than the glass transition temperature for 1 hour. Then, it is cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The obtained glass block is cut, ground, and finally mirror-polished on both sides to obtain a glass plate (amorphous glass 1 to amorphous glass 9) with a thickness of 2 mm.

[0171] The obtained amorphous glasses were subjected to heat treatment. Specifically, the amorphous glasses 1 to 9 were first heated to a first processing temperature T1 at the heating rate described in Table 2. Then, a first-stage heat treatment was performed by holding them at the first processing temperature T1 for a holding time t1. Through the first-stage heat treatment, crystal nuclei were formed throughout the entire volume of the starting glass. After the first-stage heat treatment, the precursor (the amorphous glass after the first-stage heat treatment) was heated to a second processing temperature T2 at the heating rate described in Table 2. And, a second-stage heat treatment was performed by holding it at the second processing temperature T2 for a holding time t2. Through the second-stage heat treatment, crystals grew, and the crystallinity increased. Then, the glass was cooled to room temperature at the cooling rate described in Table 2.

[0172] The amorphous glasses shown in Table 1 were heat-treated under the conditions shown in Table 2 to obtain the crystalline glasses of Examples 1 to 9. Furthermore, the physical properties described in Table 2 were obtained from the obtained crystalline glasses. The crystalline glasses of Examples 1 to 7 are exemplary examples, and the crystalline glasses of Examples 8 and 9 are comparative examples.

[0173] The methods for determining each property are shown below.

[0174] (Determination of haze value and parallel transmittance)

[0175] The obtained amorphous and crystalline glass were processed into cuboids with a length of 30.0 mm, a width of 30.0 mm, and a thickness of 0.7 mm. The 30.0 mm × 30.0 mm surface was polished to a mirror finish. The haze was measured using a Suga HZ-V3 haze meter manufactured by Suga Testing Machine Co., Ltd.

[0176] (Measurement of the electromagnetic transmittance of crystal glass)

[0177] The crystal glass was processed into a cuboid with a length of 30.0 mm, a width of 30.0 mm, and a thickness of 0.5 mm. The 30.0 mm × 30.0 mm facet was polished to a mirror finish. Using a network analyzer, the relative permittivity Dk and dielectric loss tangent tanδ at 20 °C and 10 GHz were determined by the split column dielectric resonator method (SPDR).

[0178] (Chemical fortification properties)

[0179] In addition, each crystal glass was chemically strengthened by immersing it in 100% sodium nitrate salt at 450°C for 1 hour. The surface compressive stress value CS and compressive stress depth DOL after chemical strengthening were measured using a scattered light photoelastic stress meter SLP-1000 manufactured by Orihara Corporation.

[0180] (PXRD determination of crystal glass)

[0181] The obtained crystal glass was subjected to PXRD analysis according to the following steps to identify the seed crystals.

[0182] (Sample preparation conditions for PXRD determination)

[0183] The crystallized glass plate used in the SPDR method was crushed using an agate mortar and pestle to obtain powder for PXRD determination.

[0184] (PXRD determination conditions)

[0185] Powder X-ray diffraction was measured under the following conditions to identify the precipitated crystals.

[0186] Seed crystals were identified using diffraction peak patterns from the ICSD Inorganic Crystal Structure Database and the ICDD Powder Diffraction Database.

[0187] Measurement device: Rigaku Corporation SmartLab

[0188] Determination method: Centralized method

[0189] Tube voltage: 45kV

[0190] Tube current: 200mA

[0191] Using X-rays: CuKα rays

[0192] Measurement range: 2θ = 10°~80°

[0193] Speed: 10° / minute

[0194] Step size: 0.02°

[0195] (Rietveld determination of sample preparation conditions)

[0196] After the crystalline glass powder used in the PXRD determination is passed through a 500 μm sieve, ZnO is added as a standard substance at 10% by mass of the total sample.

[0197] (Rietveld resolution conditions)

[0198] Powder X-ray diffraction was measured under the following conditions, and the results were used for Rietveld analysis.

[0199] Measurement device: Rigaku Corporation SmartLab

[0200] Determination method: Centralized method

[0201] Tube voltage: 45kV

[0202] Tube current: 200mA

[0203] Using X-rays: CuKα rays

[0204] Measurement range: 2θ = 10°~90°

[0205] Speed: 5° / minute

[0206] Step size: 0.01°

[0207] For the powder X-ray diffraction patterns obtained under the described conditions, the Rietveld analytical procedure, RietanFP, was used for analysis. The analysis of each sample was converged so that the Rwp, which indicates the quality of the analysis, was 10 or less. The Rietveld method is described in the "Crystal Analysis Handbook" edited by the Editorial Committee of the "Crystal Analysis Handbook" of the Japan Crystallographic Society (Kyoritsu Publishing, 1999, pp. 492-499).

[0208] (Calculation of the precipitation ratio of each crystal and the proportion of Li ions in Li ion sites)

[0209] The precipitation ratio (content ratio) of each crystal is calculated by subtracting the weight ratio of the crystalline phase obtained from the total amount of the sample determined by Rietveld analysis and the remaining glass phase obtained by subtracting the content of the crystalline phase from the total amount of the measured sample, and then subtracting the added 10% by mass of ZnO, with the total remaining phase being 100% by mass. Furthermore, the total precipitation ratio of each crystal represents the crystallinity of the crystalline glass.

[0210] In addition, the proportion of Li ions in the Li ion sites in the lithium disilicate crystal was calculated using the Li atomic occupancy obtained by Rietveld analysis.

[0211]

[0212]

[0213] In the table, blank columns indicate that the physical properties of the item were not measured. The precipitated crystal ratios in the table are expressed as a mass percentage relative to the total amount of crystallized glass, calculated using Rietveld analysis. Additionally, "Li ion proportion in Li ion sites" indicates the proportion of Li ions in the Li ion sites within the lithium disilicate crystal.

[0214] In the table, CS and DOL represent the surface compressive stress value CS and compressive stress depth DOL of the chemically strengthened glass for each crystal glass subjected to the above-mentioned chemical strengthening.

[0215] In the crystalline glasses of Examples 1-7, which are examples of embodiments, the proportion of Li ions in the Li ion sites of the lithium disilicate crystal is less than 95%. As a result, the combined value of the relative permittivity Dk and the dielectric loss tangent tanδ multiplied by 100 in the crystallized samples of Examples 1-7 at 20°C and 10GHz is 7.5 or less, which is a very good value, confirming good radio wave transmittance. In addition, for the crystalline glasses of Examples 1-7, a compressive stress of 50 MPa or more was applied to the surface layer by chemical strengthening. That is, the chemical strengthening characteristics of the crystalline glasses of Examples 1-7 are also excellent, and higher strength can be imparted through chemical strengthening.

[0216] On the other hand, in the comparative examples, the lithium disilicate-based crystals of the crystalline glasses in Examples 8 and 9, the proportion of Li ions in the Li ion sites was 100.0%. As a result, the combined value of the relative permittivity Dk and the dielectric loss tangent tanδ multiplied by 100 in the crystallized samples of the crystalline glasses in Examples 8 and 9 at 20°C and 10GHz exceeded 7.5, which is a very large value, resulting in poor radio wave transmittance.

[0217] As explained above, the following matters are disclosed in this specification.

[0218] 1. A crystalline glass, wherein the most abundant crystal by mass is a lithium disilicate crystal.

[0219] In the lithium disilicate crystal, the proportion of Li ions in the Li ion sites is less than 95%.

[0220] 2. The crystalline glass according to claim 1, wherein the transmittance, converted to a thickness of 0.7 mm, is 85% or more in the wavelength range of 400 nm to 1000 nm.

[0221] 3. The crystalline glass according to 1 or 2, wherein the haze value converted to a thickness of 0.7 mm is less than 5% in the wavelength range of 400 nm to 1000 nm.

[0222] 4. The crystal glass according to any one of 1 to 3, wherein the sum of the value of the dielectric loss tangent tanδ at 10 GHz and 20 °C multiplied by 100 and the relative permittivity Dk at 10 GHz and 20 °C is 7.5 or less.

[0223] 5. The crystalline glass according to any one of 1 to 4, wherein the relative permittivity Dk at 10 GHz and 20 °C is 5.8 or less.

[0224] 6. The crystalline glass according to any one of claims 1 to 5, wherein, expressed as a molar percentage based on oxides, it comprises 55-85% SiO2, 1-5% Al2O3, 0-5.0% B2O3, 0.5-5.0% P2O5, 0-5.0% TiO2, 0-5.0% ZrO2, 15-25% Li2O, 0-5.0% Na2O, 0-5.0% K2O, and a total of one or more selected from MgO, CaO, SrO, and BaO.

[0225] 7. The crystalline glass according to claim 6, wherein it contains 0.1 to 5.0% Na₂O, expressed as a molar percentage based on oxides.

[0226] 8. A method for manufacturing a crystalline glass according to any one of claims 1 to 7, wherein the method includes a step of performing at least one stage of heat treatment on the amorphous glass, wherein the temperature of the heat treatment is below 750°C, and in each of the heat treatments, the heating rate to the treatment temperature and the cooling rate from the treatment temperature are both 0.5°C / min or more.

[0227] 9. A chemically strengthened glass having a compressive stress layer on its surface, wherein the surface compressive stress value is 50 MPa or more, wherein the chemically strengthened glass is any one of the crystal glass described in any of 1 to 7 above.

[0228] 10. The chemically strengthened glass according to claim 9 is plate-shaped, wherein the proportion of alkali metal elements differs between the surface and the center in the thickness direction.

[0229] 11. An electronic device having the crystalline glass described in any one of 1 to 7 or the chemically strengthened glass described in 9 or 10 above.

[0230] The present invention has been described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0231] This application is based on Japanese Patent Application No. 2021-143384, filed on September 2, 2021, the contents of which are incorporated herein by reference.

[0232] Industrial availability

[0233] This crystalline glass and chemically strengthened glass combine the high strength and high radio wave transmittance resulting from chemical strengthening, making them useful as protective glass and circuit boards for electronic devices. They are particularly useful as protective glass for mobile devices such as mobile phones, smartphones, portable information terminals (PDAs), and tablets. Furthermore, they are useful as protective glass for display devices such as televisions (TVs), personal computers (PCs), and touch panels that are not intended for portability; as building materials such as elevator walls, walls of houses or buildings (full-screen displays), and window glass; as desktops; and as interior decoration for automobiles and aircraft. They are also useful in applications such as housings with non-plate-like curved shapes achieved through bending and molding.

Claims

1. A crystalline glass, wherein the most abundant crystal by mass is a lithium disilicate crystal. The content of lithium disilicate crystals in the crystalline glass is more than 50% by mass. In the lithium disilicate crystal, the proportion of Li ions in the Li ion sites is less than 95%. Expressed as a molar percentage based on oxides, it contains 55–85% SiO2, 1–5% Al2O3, 0–5.0% B2O3, 0.5–5.0% P2O5, 0–5.0% TiO2, 0–5.0% ZrO2, 15–25% Li2O, 0–1.5% Na2O, 0–5.0% K2O, and a total of 0–5.0% of one or more selected from MgO, CaO, SrO, and BaO.

2. The crystal glass according to claim 1, wherein, Converted to a thickness of 0.7mm, the light transmittance is over 85% in the wavelength range of 400nm to 1000nm.

3. The crystal glass according to claim 1 or 2, wherein, The haze value, converted to a thickness of 0.7 mm, is less than 5% in the wavelength range of 400 nm to 1000 nm.

4. The crystal glass according to claim 1 or 2, wherein, The sum of the dielectric loss tangent tanδ at 10 GHz and 20 °C multiplied by 100 and the relative permittivity Dk at 10 GHz and 20 °C is less than 7.

5.

5. The crystal glass according to claim 1 or 2, wherein, The relative permittivity Dk at 10 GHz and 20 °C is below 5.

8.

6. The crystal glass according to claim 1 or 2, wherein, The dielectric constant Dk at 10 GHz and 20 °C is below 5.

7.

7. The crystal glass according to claim 1, wherein, Expressed as a molar percentage based on oxides, it contains 0.1–1.5% Na₂O.

8. A method for manufacturing crystal glass, which is the method for manufacturing crystal glass according to claim 1 or 2. This includes at least one stage of heat treatment on the amorphous glass. The temperature for all heat treatments is below 750℃. In each of the aforementioned heating treatments, the heating rate to the treatment temperature and the cooling rate from the treatment temperature are both 0.5°C / min or higher.

9. A chemically strengthened glass having a compressive stress layer on its surface, wherein the surface compressive stress value is 50 MPa or higher, wherein the chemically strengthened glass is the crystalline glass as described in claim 1 or 2.

10. The chemically strengthened glass according to claim 9, wherein it is plate-shaped and the proportion of alkali metal elements differs between the surface and the center in the thickness direction.

11. An electronic device having the crystalline glass of claim 1.

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