WO2024088186A1

WO2024088186A1 - Glass-ceramic, glass-ceramic precursor, and preparation method for glass-ceramic

Info

Publication number: WO2024088186A1
Application number: PCT/CN2023/125832
Authority: WO
Inventors: 王志安; 仵小曦; 张旭海; 刘仲军; 彭引平; 薛新建
Original assignee: 彩虹集团（邵阳）特种玻璃有限公司; 彩虹集团有限公司
Priority date: 2022-10-26
Filing date: 2023-10-23
Publication date: 2024-05-02
Also published as: CN115893849A

Abstract

A glass-ceramic, a glass-ceramic precursor, and a preparation method for the glass-ceramic. The glass-ceramic comprises SiO2, Al2O3 and Li2O, the crystalline phases comprise a lithium silicate crystalline phase, a lithium feldspar solid solution and/or petalite crystalline phase, and the glass-ceramic is transparent and colorless; for a glass-ceramic having a thickness of 1 mm, the glass-ceramic has a transmittance of at least 86% within a wavelength range of 450-1000 nm. According to the glass-ceramic, by introducing TiO2, optimizing the material formula composition, and introducing the lithium feldspar solid solution crystalline phase in a crystallization process, the phenomena of warping and sheet glass fragmentation caused by a large expansion coefficient difference between the petalite crystalline phase and the lithium silicate crystalline phase are greatly improved. Moreover, the glass-ceramic has low dielectric loss and high thermal conductivity, and also meets the requirements of 5G communication for glass-ceramics.

Description

A kind of microcrystalline glass, microcrystalline glass precursor and preparation method thereof

Technical Field

The present invention relates to the field of microcrystalline glass, and in particular to microcrystalline glass, a microcrystalline glass precursor and a preparation method thereof.

Background technique

Glass-ceramics, also known as glass ceramics, is a type of polycrystalline solid material containing a large amount of microcrystalline phase and glass phase, which is obtained by controlling the crystallization of a basic glass of a specific composition during heating. Compared with ordinary glass, glass-ceramics has high mechanical properties such as high resistance to crack propagation and falling, high chemical stability and excellent thermal properties.

Based on the above advantages, microcrystalline glass is applied to the field of cover glass for mobile display devices with high strength requirements. However, the previous microcrystalline glass is either translucent or cannot be chemically strengthened, and the intrinsic strength cannot meet the requirements of the cover glass for strength performance. In addition, during the crystallization process, due to the differences in performance such as the expansion coefficient between the crystal phase and the crystal phase, the crystal phase and the glass phase, the stress distribution of the glass is uneven, resulting in warping or cracking. In the subsequent high-temperature chemical strengthening process, due to the difference in expansion coefficient, warping or cracking will also occur. On the other hand, with the development of 5G communications, higher requirements are placed on cover glass, low dielectric loss and high thermal conductivity to reduce the slowdown of high-frequency electromagnetic fields during transmission and the attenuation of signal strength. Although Corning's CN110510881B patent proposes transparent and strong microcrystalline glass for use in display-related fields, it does not propose a solution to the warping and cracking phenomena that occur during crystallization and strengthening due to the differences in expansion coefficients of the various phases of microcrystalline glass.

Summary of the invention

In view of the problems of warping and cracking of microcrystalline glass in the prior art, the present invention provides a microcrystalline glass, a microcrystalline glass precursor and a preparation method thereof, and prepares an ion-exchanged microcrystalline glass with high fracture toughness and transmittance and low haze, as well as a microcrystalline heat treatment process for the preparation, introduces TiO ₂ into the microcrystalline glass, optimizes the material composition and the crystallization process, introduces the lithium feldspar solid solution crystal phase, and greatly improves The phenomenon of warping and glass fragmentation caused by the large difference in expansion coefficient between the petalite crystal phase and the lithium silicate crystal phase was solved. The glass has low dielectric loss and high thermal conductivity, and also meets the requirements of 5G communication for microcrystalline glass.

The present invention is achieved through the following technical solutions:

A microcrystalline glass, comprising, by mass percentage, 65% to 78% _SiO2 ; ₃ % to 10% _Al2O3 ; 6% to 12% Li2O _; 1% to 8% P2O5; 0.5% to 6% ZrO2; 0.6% to 6% MgO; _0.5 % to 5% B2O3 _; 0.3% to 3 _% K2O; 0.1% to 1% Na2O; 0.3% to 3% ZnO _; 0.5% to 8% TiO2; wherein the mass percentage ratio of (SiO2 + Li2O ₎ to Al2O3 _is 6 to ₁₅ , the mass percentage ratio of Al2O3 to Li2O3 is 6 to 15, the mass percentage ratio of (SiO2 + _Li2O ) to Al2O3 is 6 to 15, the mass percentage ratio of (Al2O3 to Li2O3) to ( _Al2O3 ) is 6 to 15, the mass percentage ratio of (Al2O3 to Li2O3) _to ( _Al2O3 ) is 6 to 15, the mass percentage ratio of ( _{Al2O3 to Li2O3) to (Al2O3} _to Li ... _SiO2 + Li2O) to (Al2O3 to _Li2 The mass percentage of O is 0.7 to 1.3, the crystalline phase includes a lithium silicate crystalline phase, a lithium feldspar solid solution and/or a lithium feldspar crystalline phase, and the microcrystalline glass is transparent and colorless; for a microcrystalline glass with a thickness of 1 mm, the microcrystalline glass has a transmittance of at least 86% within a wavelength range of 450 nm to 1000 nm.

Preferably, the lithium silicate crystal phase accounts for 30wt% to 70wt% of the glass-ceramics.

Preferably, the lithium silicate crystal phase is lithium disilicate, lithium metasilicate or a combination thereof.

Preferably, in terms of mass percentage, P ₂ O ₅ +ZrO ₂ <12 wt %.

Preferably, in terms of mass percentage, MgO+ZnO＞0.5%.

Preferably, when the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a blocking rate of more than 27% for blue light of 400 nm to 450 nm.

Preferably, when the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a haze of no more than 0.3%.

Preferably, the glass-ceramics has the following transmission or reflection color coordinates in the CIE L*a*b* colorimetric system: L*≥90, a* is -0.2 to 0.2, and b* is -0.2 to 0.6.

Preferably, at room temperature and a frequency of 2467 MHZ, the dielectric loss tangent of the microcrystalline glass is less than or equal to 0.002.

Preferably, at 25° C., the thermal conductivity of the glass-ceramics is greater than or equal to 2 W/m·K.

Preferably, the crystallinity of the glass-ceramics is greater than 50%.

Preferably, the crystallinity of the glass-ceramics is above 60%.

Preferably, the crystallinity of the glass-ceramics is above 70%.

Preferably, the crystallinity of the glass-ceramics is above 80%.

Preferably, the crystallinity of the glass-ceramics is above 90%.

Preferably, the glass-ceramic further comprises crystal grains, wherein the crystal grains have a longest dimension of 60 nm or less.

Preferably, the glass-ceramics has a fracture toughness of 1 MPa·m ^1/2 or more.

Preferably, the glass-ceramics has a fracture toughness of 1.2 MPa·m ^1/2 or greater.

Preferably, the glass-ceramics has a Vickers hardness of 650 kgf/mm ² or more.

Preferably, the glass-ceramics has a Vickers hardness of 750 kgf/mm ² or more.

Preferably, the glass-ceramics has a Vickers hardness of 800 kgf/mm ² or more.

Preferably, the glass-ceramic has an elastic modulus of 90 GPa or greater.

Preferably, the glass-ceramic has an elastic modulus of 100 GPa or greater.

Preferably, when the microcrystalline glass is placed in a 10 wt % HF solution at 20° C. for 20 minutes, the weight loss is no more than 12 mg/cm ² .

Preferably, the glass-ceramics is placed in a 5 wt % HCl solution at 95° C. for 24 hours, and its weight loss is no more than 0.06 mg/cm 2 .

Preferably, the glass-ceramics is placed in a 5 wt % NaOH solution at 95° C. for 6 hours, and its weight loss is no more than 0.14 mg/cm 2 .

Preferably, the glass-ceramics has a surface compressive stress of not less than 200 MPa.

Preferably, the glass-ceramics has a surface compressive stress of not less than 300 MPa.

Preferably, the strengthening time is no more than 16 hours, and the glass-ceramics has a compressive stress layer depth of at least 60 microns.

Preferably, the strengthening time is no more than 16 hours, and the glass-ceramics has a compressive stress layer depth of at least 80 microns.

Preferably, the strengthening time is no more than 16 hours, and the glass-ceramics has a compressive stress layer depth of at least 100 microns.

Preferably, the strengthening time is no more than 16 hours, and the glass-ceramics has a compressive stress layer depth of at least 120 microns.

Preferably, the strengthening time is no more than 16 hours, and the glass-ceramics has a compressive stress layer depth of at least 140 microns.

Preferably, the strengthening time is no more than 12 hours.

Preferably, the strengthening time is no more than 8 hours.

Preferably, the glass-ceramic has a central tensile stress of at least 80 MPa.

Preferably, it also comprises central tensile stress, and the microcrystalline glass has a central tensile stress of at least 90 MPa.

Preferably, the composition _, by mass percentage, contains: _SiO2 : 68% to 75%; _Al2O3 : 4% to 7%; _Li2O : 7% to 11%; _P2O5 : 1% to 8%; _ZrO2 : _0.5 % to 6%; MgO: 0 to 6%; _B2O3 : 0 to 5%; _K2O : 0 to ₃ %; _Na2O : 0 to 1%; ZnO: 0 to 3%; _TiO2 : 0.5% to 8%; wherein the mass percentage ratio of ₍ _SiO2 + _Li2O ) to _Al2O3 is 6 to 15, _{and the mass percentage ratio of Al2O3} _to _Li2O is 0.7 to 1.3.

An electronic device includes a cover, wherein the cover includes microcrystalline glass.

A microcrystalline glass, comprising _, by mole percentage, 65% to 78% _SiO2 , 3% to 10% Al2O3 _, 6% to 12% _Li2O , 1% to 8% P2O5, 0.5% to 6% ZrO2 _, 0.5% to 6% MgO _, 0% to 6 _% _B2O3 , ₀ % to 5% K2O, 0% to 3% _Na2O, 0% to 1% ZnO, and 0.5% to 8% _TiO2 . The mass percentage ratio of ( _SiO2 + _Li2O ) to _Al2O3 is 6 to 15, _and the mass percentage ratio _{of Al2O3} _to _Li2O3 is 6 to ₁₅ . The mass percentage of O is 0.7 to 1.3. When the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a transmittance of at least 86% within a wavelength range of 450 nm to 1000 nm. The microcrystalline glass has a fracture toughness greater than 1 MPa·m ^1/2 .

Preferably, the crystal phase of the glass-ceramics includes 30 wt % to 70 wt % of lithium silicate crystal phase, lithium feldspar solid solution and/or petalite.

Preferably, the glass-ceramics has a Vickers hardness of 650 kgf/mm ² or more.

Preferably, the glass-ceramics has a Vickers hardness of 750 kgf/mm ² or more.

Preferably, the glass-ceramics has a Vickers hardness of 800 kgf/mm ² or more.

Preferably, the glass-ceramic has an elastic modulus of 90 GPa or greater.

Preferably, the glass-ceramic has an elastic modulus of 100 GPa or greater.

Preferably, the glass-ceramics is placed in a 10 wt% HF solution at 20°C for 20 minutes, and its weight loss is no greater than 12mg/ ^cm2 .

Preferably, when the glass-ceramics is placed in a 5 wt % HCl solution at 95° C. for 24 hours, the weight loss is no more than 0.06 mg/cm ² .

Preferably, when the glass-ceramics is placed in a 5 wt % NaOH solution at 95° C. for 6 hours, the weight loss is no more than 0.14 mg/cm ² .

Preferably, the glass-ceramic has a central tensile stress of at least 90 MPa.

Preferably, the glass-ceramic is colorless and has the following transmission or reflection color coordinates in the CIE L*a*b* colorimetric system: L*≥90, a* is -0.2 to 0.2, and b* is -0.2 to 0.6.

Preferably, the crystallinity of the glass-ceramics is above 70%.

An electronic product comprises a cover protection member, wherein the cover protection member comprises microcrystalline glass.

A microcrystalline precursor glass composition, comprising, by mass percentage, 65% to 78% _SiO2 ; ₃ % to 10% _Al2O5 _; ₆ % to 12% Li2O; 1% to 8% _P2O5 ; 0.5% to _{6% ZrO2; 0.6% to 6% MgO; 0.5% to 5% B2O3; 0.3} _% _to 3% K2O; 0.1% to 1% Na2O; 0.3 _% to 3% ZnO; and _0.5 % to 8% TiO2. The ratio of the mass percentage of ( _SiO2 + _Li2O ) to _Al2O3 is ₆ to 15, _{and the mass percentage of Al2O3} _to _Li2O3 _is 6 to 15. The mass percentage of O is 0.7-1.3; the temperature range corresponding to the viscosity of the precursor glass composition of 1000P-10000P is 900°C-1200°C, and the preparation of the precursor glass is suitable for calendering, casting and float forming processes.

Preferably, at 20°C to 380°C, the thermal expansion coefficient of the precursor glass composition is 7.0×10 ^{-6 /} °C to 8.5× ^{10 -6} /°C.

Preferably, at 20° C. to 600° C., the thermal expansion coefficient growth rate of the precursor glass composition is no more than 6%.

Preferably, the softening point of the precursor glass composition is 660° C. to 690° C., and 3D hot bending can be performed directly during the crystallization process.

A method for preparing glass-ceramics comprises the following steps:

S1, preparing a microcrystalline precursor glass composition, wherein the microcrystalline precursor glass composition comprises the following components in percentage by mass: _SiO2 : 65-78%; _Al2O3 : _3-10 %; Li2O: 6-12% _; _P2O5 _: 1-8%; _ZrO2 : 0.5-6%; MgO: 0-6%; B2O3: 0-5%; K2O: 0-3%; _Na2O : _0-1 %; ZnO _: 0-3%; _TiO2 : 0.5-8%; wherein the mass percentage ratio of ₍ _SiO2 + _Li2O ) to _Al2O3 is 6-15, _and the mass percentage ratio of _Al2O3 to _Li2O is _0.7-1.3 ;

S2, performing a microcrystallization heat treatment on the microcrystalline precursor glass composition to form a microcrystalline glass, wherein the crystallinity of the microcrystalline glass is ≥70%, and the crystal phase of the microcrystalline glass is lithium silicate, lithium feldspar solid solution and/or lithium feldspar crystal phase, wherein the microcrystalline glass is transparent, and when the thickness of the microcrystalline glass is 1 mm, the transmittance of the light within the wavelength range of 450 nm to 1000 nm is not less than 86%;

S3, chemically strengthening the microcrystalline glass after the crystallization heat treatment to form a strengthened microcrystalline glass, wherein the strengthened microcrystalline glass has a surface compressive stress of not less than 200 MPa and a compression layer depth of not less than 80 μm.

Preferably, the microcrystallization heat treatment process includes the following sequential steps: first, the microcrystalline precursor glass composition is heated to the nucleation temperature at a certain heating rate, and maintained at the nucleation temperature for a predetermined time to obtain a nucleated microcrystalline precursor composition; then, the nucleated microcrystalline precursor composition is heated to the crystallization temperature, and maintained at the crystallization temperature for a predetermined time to obtain a crystallized microcrystalline precursor glass composition; finally, the crystallized microcrystalline precursor glass composition is cooled to room temperature at a certain cooling rate to obtain microcrystalline glass.

Preferably, the chemical strengthening process is to immerse the microcrystalline glass in a single salt bath, wherein the molten salt or salt melt contains at least one ion having a radius larger than the radius of the alkali metal ions in the glass.

Preferably, the salt bath comprises nitrates or sulfates of potassium and sodium.

Preferably, the chemical strengthening process is to immerse the glass-ceramics in a plurality of salt baths having the same or different compositions, wherein the molten salt or salt melt contains at least one ion having a radius larger than the semi-circular radius of the alkali metal ions in the glass. The salt bath contains nitrates or sulfates of potassium and sodium, the concentration of potassium ions in the latter salt bath being greater than that in the former salt bath.

Compared with the prior art, the present invention has the following beneficial effects:

The microcrystalline glass of the present invention introduces TiO ₂ , optimizes the material composition and crystallization process, and introduces the lithium feldspar solid solution crystal phase, which greatly improves the warping and glass fragmentation caused by the large difference in expansion coefficient between the lithium feldspar crystal phase and the lithium silicate crystal phase. The glass has low dielectric loss and high thermal conductivity, and also meets the requirements of 5G communication for microcrystalline glass.

The microcrystalline glass product of the present invention has lithium disilicate and lithium feldspar solid solution as main crystal phases, which provides the microcrystalline glass product with inherent high mechanical strength and fracture toughness.

Lithium feldspar solid solution and/or petalite crystal phase is the second crystal phase with a small grain size, which makes the microcrystalline glass have high transparency. It can be used as a low thermal expansion phase to improve the thermal shock resistance of microcrystalline glass. Lithium feldspar solid solution compensates for the stress concentration caused by the large difference in expansion coefficients between petalite and lithium silicate phases, reducing the warping and cracking of glass. In addition, lithium feldspar solid solution and/or petalite crystal phase can be chemically strengthened in a salt bath to increase the strength of microcrystalline glass products. Microcrystalline glass has high chemical stability, and its acid and alkali corrosion resistance is 30 times higher than that of the mainstream second-strong lithium aluminum silicon cover glass.

LiAlSi ₄ O ₁₀ is a monoclinic crystal with a small grain size. It is a lithium source with an expansion coefficient of 0.3×10 ^-6 /℃. It is used as a low expansion phase to improve the thermal shock resistance of microcrystalline glass products. MgO or ZnO enters the petalite crystal in the form of a partial solid solution to form a lithium feldspar solid solution Lix(Mg,Zn) _0.5-0.5x AlSi ₄ O ₁₀ , resulting in lattice distortion and peak position shift in XRD test.

The lithium feldspar solid solution crystal phase has a small grain size, which makes the microcrystalline glass have high transparency, and the expansion coefficient is larger than that of petalite, which reduces the difference in expansion coefficient between it and lithium disilicate, and can improve the warping and cracking of the sample after crystallization. In addition, petalite and lithium feldspar solid solution Li _x (Mg, Zn) _0.5-0.5x AlSi ₄ O ₁₀ can be chemically strengthened in a salt bath, in which Na ⁺ (and/or K ⁺ ) replaces Li ⁺ in the lithium feldspar solid solution structure, so that a compressive stress layer is generated on the surface of the microcrystalline glass product, thereby improving the strength of the glass.

The lithium silicate crystal phase can be lithium disilicate or lithium metasilicate. Lithium disilicate Li ₂ Si ₂ O ₅ is an orthorhombic crystal of corrugated sheets based on {Si ₂ O ₅ } tetrahedral arrays. The crystals are usually flat or plate-like and have obvious Dissociation surface. Because the microstructure of irregularly oriented interlocking crystals deflects cracks and passivates crack tips, thus preventing crack propagation and improving the inherent mechanical strength and fracture toughness of microcrystalline glass, but the lithium disilicate crystal phase has a relatively high linear thermal expansion coefficient of about (9.5-10.5)× ^10-6 /K, and lithium _disilicate reduces the thermal stability of microcrystalline glass. Lithium metasilicate _Li2SiO3 has orthorhombic symmetry, and the ( _Si2O6 ) chains are parallel to the c-axis and connected by lithium ions. In dilute _hydrofluoric acid, lithium metasilicate is easily dissolved from the glass. Because the refractive index of lithium metasilicate is quite different from that of the base glass, too much lithium metasilicate will reduce the transparency and strength of microcrystalline glass.

The present invention discloses a microcrystalline precursor glass composition, whose melting temperature is lower than 1400°C, whose viscosity corresponding to the liquidus temperature is greater than 3000P, whose molding viscosity is 1000P-10000P in the temperature range of 900°C-1200°C, and whose viscosity-temperature characteristics are suitable for various molding processes such as calendering, casting, and float process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a differential scanning calorimetry (DSC) curve of a microcrystalline precursor glass composition.

Figure 2 is the transmittance curve of 0.7mm glass-ceramics from 200nm to 1000nm wavelength.

FIG. 3 is a scanning electron microscope (SEM) image of glass-ceramics at a magnification of 100,000 times.

FIG. 4 is an X-ray diffraction pattern (XRD) of the crystal phase of glass-ceramics.

FIG. 5 is a graph showing the mass percentage of Na in a glass-ceramic product after chemical strengthening as a function of sample thickness (EPMA).

FIG. 6 is a front plan view of the consumer electronic product.

Detailed ways

The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

The invention discloses a microcrystalline glass, which comprises _{, by mass percentage, 65% to 78% SiO2, 3} _% _to 10% Al2O3 _, 6% to 12% _Li2O , 1% to 8% P2O5 _, 0.5% to 6% ZrO2, _0.5 % to 6% MgO, 0% to 6% _B2O3 , 0% to 5% _K2O _, 0% to 3% Na2O, 0% to 1% ZnO, and _0.5 % to 8% TiO2. The mass percentage ratio of ( _SiO2 + _Li2O ) to _Al2O3 is 6 to ₁₅ , the mass percentage ratio of _Al2O3 to _Li2O is _0.7 to 1.3, _P2O5 + _ZrO2 is less than _12wt %, _and MgO+ZnO is greater than 0.5%.

_SiO2 is a basic component of the microcrystalline precursor glass composition of the present invention, used to stabilize the network structure of the glass, and is one of the components that form lithium silicate, lithium feldspar solid solution and/or lithium feldspar crystal phase. If its concentration is too low, it will affect the content and grain size of the formed crystal phase, thereby affecting the optical properties; the concentration should be high enough to form a lithium feldspar solid solution phase, but the glass melting temperature is high and it is not easy to form. Therefore, the content of _SiO2 is 68wt%, preferably 70wt%, and more preferably 72wt%.

Al ₂ O ₃ is a component that forms a glass network structure. The aluminum oxide polyhedrons and silicon oxide tetrahedrons formed by the Al 2 O 3 interpenetrate into a network structure. Increasing the content can reduce the crystallization tendency of the glass, improve thermal stability, chemical stability, mechanical strength and hardness, and increase the depth of the ion exchange layer and surface stress of the microcrystalline glass. However, if the content is too high, the fraction of lithium silicate will be reduced, and the degree of interlocking structure may not be achieved, and the viscosity of the melt will be increased. Reducing the Al ₂ O ₃ will make the lithium disilicate crystal phase have a higher mass proportion, resulting in a higher mass proportion of lithium disilicate than that of petalite and/or petalite solid solution. Its interlocking structure improves the strength of the glass, improves the fracture toughness, improves the drop resistance, and increases the margin of basic glass preparation and crystallization. Therefore, in order to make lithium silicate have a higher mass proportion, the range of Al ₂ O ₃ is 3wt% to 10wt%.

Li ₂ O is an essential component of the crystal phase composition and also an essential component of chemical strengthening. If its content is insufficient, the crystallization effect and strengthening performance will be affected; if its content is too high, the chemical stability of the glass will be reduced and the optical properties of the microcrystalline glass will be reduced. Therefore, the range of Li ₂ O is 6wt% to 12wt%.

The experiment found that the ratio of SiO ₂ , Al 2 O ₃ and Li ₂ O has a certain influence on the crystallization of the sample. The ratio of (SiO ₂ +Li ₂ O)/Al ₂ O ₃ will affect the haze and grain size of the microcrystalline glass. Therefore, the value range of (SiO ₂ +Li ₂ O)/Al ₂ O ₃ is 6 to 15, which can obtain smaller grains and improve the mechanical strength of the microcrystalline glass. The appropriate Al ₂ O ₃ /Li ₂ O ratio is conducive to the precipitation of lithium disilicate crystal phase, so the value range of Al ₂ O ₃ /Li ₂ O is 0.7 to 1.3.

The microcrystalline precursor glass composition contains P ₂ O ₅ _, _which can form crystal nuclei during the glass crystallization process, promote the formation of crystals, and improve the crystallinity of the microcrystalline glass. If the concentration is too low, the precursor glass will not crystallize; if the concentration is too high, phase separation may occur when the precursor glass is cooled during the formation process, and it will be difficult to control devitrification. Therefore, the addition range of P ₂ O ₅ is 1wt% to 8wt%.

ZrO ₂ can partially enter petalite in the form of solid solution. ZrO ₂ can reduce P ₂ O ₅ in glass forming. During crystallization, the crystallization temperature is increased to ensure the integrity of the crystal phase in the glass-ceramics and reduce the haze of the glass-ceramics. At high temperatures, _ZrO2 can significantly reduce the liquidus viscosity, reduce the grain size of the lithium feldspar solid solution, _and help form transparent glass-ceramics. Too high a content of _P2O5 + _ZrO2 will reduce the uniformity and transparency of the glass _{-ceramics; too low a content will reduce the crystallization rate and make it difficult to obtain high strength. Appropriate P2O5+ZrO2 can easily obtain a finer crystal phase. Therefore, the content of P2O5} ₊ _ZrO2 _is _less _than 4wt%.

ZnO can enter petalite in the form of partial solid solution. ZnO can reduce the difficulty of glass melting and promote low-temperature crystallization of glass, but when the concentration is too high, the crystallinity and transmittance of the sample will decrease and the haze will increase.

MgO reduces the difficulty of glass melting, but it can easily reduce the crystallinity and optical properties of microcrystalline glass.

B 2 O ₃ improves the network structure of glass-ceramics and adjusts the chemical strengthening properties of glass-ceramics, but excessive B ₂ O 3 makes it easy for the glass to crystallize during molding.

TiO ₂ helps to lower the melting temperature of glass, improve chemical stability, reduce thermal expansion coefficient, and inhibit crystallization of precursor glass. The introduction of TiO ₂ helps to form lithium feldspar solid solution Lix(Mg,Zn)0.5～0.5xAlSi ₄ O ₁₀ , which is beneficial to improve the preparation of basic precursor glass.

_SnO2 acts as a clarifier to improve the defoaming ability of glass-ceramics.

The glass-ceramics of the present invention can also be generally described as lithium-containing silicate glass or glass-ceramics, comprising SiO ₂ , Al ₂ O ₃ and Li ₂ O. In addition to SiO ₂ , Al ₂ O ₃ and Li ₂ O, the glass and glass-ceramics of the present invention also include alkaline salt K ₂ O, as well as P ₂ O ₅ , ZrO ₂ and various other components.

The crystal phase of glass-ceramics includes lithium silicate crystal phase, lithium feldspar solid solution and/or lithium feldspar crystal phase, which provide high strength and transparency for glass-ceramics products. The lithium silicate crystal phase accounts for 30wt% to 70wt% of the glass-ceramics, and the lithium silicate crystal phase is lithium pyrosilicate, lithium metasilicate or a combination of the two. The crystal phase type, crystal phase ratio and crystallinity of the sample are tested by X-ray diffraction (XRD), and calculated by JADE combined with Rietveld full spectrum fitting refinement. The glass-ceramics also contains grains, and the grains have a longest dimension of less than 100nm, preferably a longest dimension of 60nm or less.

Microcrystalline glass products have high transmittance and low haze, and excellent optical properties. The grain size, crystal phase type and mass ratio in microcrystalline glass products will affect the haze and transmittance of the products. The smaller the grain, the higher the transmittance; the smaller the haze, the higher the transmittance. The haze, transmittance and Lab color coordinates are calculated using the CS-700 colorimetric system. Color haze meter test. Glass-ceramics is transparent and colorless. Glass-ceramics has the following transmission or reflection color coordinates in the CIE L*a*b* colorimetric system: L*≥90, a* is -0.2 to 0.2, and b* is -0.2 to 0.6.

For a 1mm thick glass-ceramic, within the wavelength range of 450nm to 1000nm, the glass-ceramic has a transmittance of at least 86%, preferably above 90%. When the thickness of the glass-ceramic is 1mm, for blue light of 400nm to 450nm, the glass-ceramic has a barrier rate of more than 27%, and has a haze of no more than 0.3%, preferably less than 0.2%, and more preferably less than 0.15%. At room temperature and a frequency of 2467MHZ, the dielectric loss tangent of the glass-ceramic is less than or equal to 0.002. At 25°C, the thermal conductivity of the glass-ceramic is greater than or equal to 2W/m·K.

In some embodiments, the crystallinity of the glass-ceramics is greater than 50%, preferably greater than 60%, preferably greater than 70%, preferably greater than 80%, and more preferably greater than 90%.

Glass-ceramics have excellent strengthenability, and chemical strengthening can give glass-ceramics additional mechanical strength. Glass-ceramics have a fracture toughness of 1 MPa·m ^1/2 or greater, more preferably 1.2 MPa·m ^1/2 or greater. Fracture toughness is measured using methods known in the art, such as Vickers hardness indentation method, according to GB/T 37900-2019, "Ultra-thin glass hardness and fracture toughness test method small load Vickers indentation method".

The microcrystalline glass has high scratch resistance, and the Vickers hardness uses GB/T 37900-2019, "Ultra-thin glass hardness and fracture toughness test method small load Vickers indentation method". In one or more embodiments, the non-chemically strengthened microcrystalline glass has a Vickers hardness of 650kgf/ ^mm2 or greater, preferably the microcrystalline glass has a Vickers hardness of 750kgf/ ^mm2 or greater, and more preferably the microcrystalline glass has a Vickers hardness of 800kgf/ ^mm2 or greater.

The elastic modulus is measured using a method known in the art, according to GB/T 37788-2019, "Test method for elastic modulus of ultra-thin glass". In some embodiments, the microcrystalline glass has an elastic modulus of 90 GPa or greater, and the microcrystalline glass has an elastic modulus of 100 GPa or greater.

The microcrystalline glass has a surface compressive stress of not less than 200 MPa, and more preferably, the microcrystalline glass has a surface compressive stress of not less than 300 MPa.

The strengthening time is not more than 16 hours, and the microcrystalline glass has a compressive stress layer depth of at least 60 microns, preferably The microcrystalline glass has a compressive stress layer depth of at least 80 microns, preferably the microcrystalline glass has a compressive stress layer depth of at least 100 microns, preferably the microcrystalline glass has a compressive stress layer depth of at least 120 microns, and more preferably the microcrystalline glass has a compressive stress layer depth of at least 140 microns.

The glass-ceramic has a central tensile stress of at least 80 MPa, and preferably the glass-ceramic has a central tensile stress of at least 90 MPa.

The microcrystalline glass of the present invention has excellent chemical durability. The chemical durability test is carried out by the weight loss method known in the art, according to GB/T 31644-2016, "Test method for chemical durability of flat panel display substrate glass". During the test, the glass sample is cut into a certain size, polished to a mirror surface on six sides, and immersed in a chemical reagent of a certain concentration. By comparing the difference in weight of the sample before and after chemical erosion, the change in the mass per unit area of the sample (unit: mg/cm ² ) is calculated to evaluate the chemical durability of the sample. In one or more embodiments, the microcrystalline glass is immersed in a 5wt% HCl solution at 95°C for 24 hours, and its weight loss per unit area is approximately 0.06mg/ ^cm2 or less, 0.05mg/ ^cm2 or less, 0.04mg/ ^cm2 or less, 0.03mg/ ^cm2 or less; immersed in a 10wt% HF solution at 20°C for 20 minutes, and its weight loss per unit area is approximately 11.8mg/ ^cm2 or less, approximately 11.0mg/ ^cm2 or less, approximately 10.8mg/ ^cm2 or less, approximately 10.0mg/ ^cm2 or less; immersed in a 5wt% NaOH solution at 95°C for 6 hours, and its weight loss per unit area is approximately 0.14/ ^cm2 or less, 0.12/ ^cm2 or less, 0.10/ ^cm2 or less, 0.08/ ^cm2 or less.

In some embodiments, the expansion coefficient of the microcrystalline glass changes very little over a large temperature range. In the temperature range of room temperature to 380°C, the expansion coefficient is about 7.6× ^10-6 /°C or greater, about 7.8× ^10-6 /°C or greater, about 7.9× ^10-6 /°C or greater, about 8×10-6 ^/ °C or greater, and about 8.1× ^10-6 /°C or greater; in the temperature range of room temperature to 600°C, the expansion coefficient is about 7.6× ^10-6 /°C or greater, about 7.8× ^10-6 /°C or greater, about 7.9× ^10-6 /°C or greater, about 8× ^10-6 /°C or greater, and about 8.1× ^10-6 /°C or greater.

A microcrystalline precursor glass composition, comprising, by mass percentage, 65% to 78% _SiO2 , ₃ % to 10% _Al2O5 _, 6% to 12% Li2O, 1% to ₈ % P2O5 _, 0.5% to 6% ZrO2, and MgO _. 0～6％; B ₂ O ₃ : 0～5％; K ₂ O: 0～3％; Na ₂ O: 0～1％; ZnO: 0～3％; TiO ₂ : 0.5％～8％; wherein the mass percentage ratio of (SiO ₂ +Li ₂ O) to Al ₂ O ₃ is 6～15, and the mass percentage ratio of Al ₂ O ₃ to Li ₂ O is 0.7～1.3; the temperature range corresponding to the viscosity of 1000P～10000P of the precursor glass composition is 900℃～1200℃, and the preparation of the precursor glass is suitable for calendering method, casting method and float forming process.

In some embodiments, the glass described in the present invention can be made into sheets through various processes. By adjusting the liquidus viscosity, the glass composition described in the present invention has a liquidus viscosity-temperature characteristic of 2000P-4000P and is suitable for various molding processes such as calendering, casting, and float.

At 20°C to 380°C, the thermal expansion coefficient of the precursor glass composition is 7.0×10 ^{-6 /} °C to 8.5×10 ^-6 /°C. At 20°C to 600°C, the thermal expansion coefficient growth rate of the precursor glass composition is no more than 6%. The softening point of the precursor glass composition is 660°C to 690°C, and 3D hot bending can be performed directly during the crystallization process.

A method for preparing glass-ceramics comprises the following steps:

S1, preparing a microcrystalline precursor glass composition, wherein the microcrystalline precursor glass composition comprises the following components in percentage by mass: _SiO2 : 65% to 78%; _Al2O3 : ₃ % to 10%; _Li2O : 6% to 12%; _P2O5 : 1% to 8%; _ZrO2 _: 0.5% to 6%; MgO: 0 to 6% _; _B2O3 : 0 to 5%; _K2O : 0 to 3%; _Na2O : 0 to 1%; ZnO: 0 to 3%; _TiO2 : 0.5% to 8%; wherein the mass percentage ratio of ( _SiO2 + _Li2O ₎ to _Al2O3 is 6 _to 15, and the mass percentage ratio of _Al2O3 to _Li2O is 0.7 to 1.3;

The microcrystallization heat treatment process includes the following sequential steps: first, the microcrystalline precursor glass composition is heated to the nucleation temperature at a certain heating rate, and maintained at the nucleation temperature for a predetermined time to obtain a nucleated microcrystalline precursor composition; then, the nucleated microcrystalline precursor composition is heated to the crystallization temperature, and maintained at the crystallization temperature for a predetermined time to obtain a crystallized microcrystalline precursor glass composition; finally, the crystallized microcrystalline precursor glass composition is cooled to room temperature at a certain cooling rate to obtain microcrystalline glass.

In one or more embodiments, the method for preparing microcrystalline glass includes heat treating a microcrystalline precursor glass at one or more pre-selected temperatures for one or more selected times to precipitate one or more crystalline phases of the glass. In some embodiments, the crystallization heat treatment process may include but is not limited to the following steps: ① heating the microcrystalline precursor glass to the nucleation temperature at a heating rate of 0.1-20°C/min; ② keeping the microcrystalline precursor glass at the nucleation temperature for about 10min-360min to form a nucleated crystallizable glass; ③ heating the nucleated crystallizable glass to the crystallization temperature at a heating rate of 0.1-20°C/min; ④ keeping the nucleated crystallizable glass at the crystallization temperature for about 10min-360min to form the microcrystalline glass of the present invention; ⑤ cooling the formed microcrystalline glass to room temperature. In some embodiments, the glass nucleation temperature may be 520-620°C, and the crystallization temperature may be 700-800°C.

S3, chemically strengthening the crystallized glass-ceramics to form strengthened glass-ceramics, wherein the strengthened glass-ceramics has a surface compressive stress of not less than 200 MPa and a compression layer depth of not less than 80 μm. The chemical strengthening process is to immerse the glass-ceramics in a single salt bath, wherein the molten salt or salt melt contains at least one ion having a radius greater than the radius of the alkali metal ion in the glass. The salt bath contains nitrates or sulfates of potassium and sodium.

The chemical strengthening process is to immerse the microcrystalline glass in multiple salt baths with the same or different compositions, wherein the molten salt or salt melt contains at least one ion with a radius larger than the radius of the alkali metal ions in the glass; the salt bath contains nitrates or sulfates of potassium and sodium, and the potassium ion concentration in the latter salt bath is greater than that in the former salt bath.

All glass-ceramics of the present invention can be ion-exchanged by methods known in the art. During the ion exchange process, smaller metal ions in the glass are replaced by larger metal ions in a salt bath. Replacing smaller ions with larger ions forms compressive stress in the glass-ceramics. In some embodiments, the metal ions are monovalent alkali metal ions (e.g., Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , etc.), and the ion exchange is performed by immersing the glass-ceramics in a molten salt bath containing at least one larger metal ion, which is used to replace the smaller metal ions in the glass-ceramics. One or more ion exchange processes used to strengthen the glass-ceramics may include, but are not limited to: immersing it in a single salt bath, or immersing it in multiple salt baths of the same or different compositions, with a wash and/or annealing step between immersions.

In one or more embodiments, the glass-ceramics can be prepared by immersing the glass-ceramics in a molten Na2O3 solution at about 420°C to 520°C. The ion exchange is carried out in a salt bath of salt for 8 to 16 hours. In this embodiment, Na ⁺ ions replace part of the Li ⁺ ions in the microcrystalline glass, thereby forming a compressive stress layer on the surface and showing high strength.

In some embodiments, the glass-ceramics may be ion-exchanged by being immersed in a salt bath of molten K ⁺ salt at about 420° C. to 520° C. for 8 h to 16 h, thereby forming a compressive stress layer on the surface.

In some or more embodiments, chemical strengthening of the glass-ceramics is performed in at least two alkali metal salt melts of different compositions.

In some embodiments, the microcrystalline glass can be ion exchanged to obtain a compressive stress layer of about 60 μm or greater, about 80 μm or greater, about 100 μm or greater, about 120 μm or greater, about 140 μm or greater, about 150 μm or greater, about 160 μm or greater.

The formation of such a surface compressive stress layer provides better crack growth resistance for relatively non-ion exchanged materials. The surface compressive layer has a high concentration of ions exchanged into the glass-ceramic article compared to the concentration of ions exchanged into the glass-ceramic body (excluding the surface compressive region).

In some embodiments, the glass-ceramics may have a surface compressive stress of about 150MPa to 250MPa, 150MPa to 300MPa, 150MPa to 350MPa, 200MPa to 250MPa, 200MPa to 300MPa, 200MPa to 350MPa, 250MPa to 300MPa, 250MPa to 350MPa, 250MPa to 300MPa, 250MPa to 350MPa, 250MPa to 400MPa, 300MPa to 350MPa. Compressive stress (CS) and depth of compressive stress layer (DOL) are measured using methods known in the art. Compressive stress (CS) and depth of compressive stress layer (DOL) can be measured by Japanese Orihara FSM-6000LEUV and SLP-2000.

Example

To further clearly illustrate and describe the technical solutions of the present invention, the following non-limiting examples are provided. The present invention has made many efforts to ensure the accuracy of the numerical values, but some errors and deviations must be considered.

Example glass and glass-ceramic compositions and properties for obtaining transparent glass-ceramics are shown in Table 1 and are measured according to conventional techniques in the glass field. Precursor glasses having compositions 1-8 listed in Table 1 are formed. Differential scanning calorimetry (DSC) is performed on the precursor glass composition 4, and DSC (mW/mg) is plotted against temperature °C to indicate the crystallization temperature. The precursor glass is then subjected to a microcrystallization heat treatment.

The liquidus temperature test refers to the standard ASTM C829-81. The method includes placing crushed glass in a platinum boat, placing the boat in a furnace with a gradient temperature zone, heating the boat at a set appropriate temperature for 24 hours, and detecting the highest temperature at which crystals appear inside the glass by using a microscope.

As can be seen from Table 1, the relevant property parameters of composition 4 are measured: the transmittance for light of 450nm-1000nm, as shown in Figure 2, in the visible light wavelength, the transmittance of the microcrystalline glass is greater than 86%, the Vickers hardness is about 820kgf/mm ² , and the fracture toughness, the value of which is 1.21MPa·m ^1/2 . According to the scale in Figure 3, it can be measured that the grain size of lithium feldspar solid solution and lithium disilicate is 30-50nm. After strengthening, electron probe microanalysis (EPMA) is performed, as shown in Figure 5, and an exchange layer depth of more than 200 microns is obtained. As shown in Figure 4, the main crystalline phases are lithium feldspar solid solution and lithium disilicate.

This specification also discloses an electronic device, referring to FIG. 6 , comprising a cover comprising glass-ceramics.

The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

A microcrystalline glass, characterized in that the composition, by mass percentage, contains: SiO2 : 65% to 78%; Al2O3 : 3 % to 10%; Li2O : 6% to 12%; P2O5 : 1% to 8%; ZrO2 : 0.5 % to 6% ; MgO: 0 to 6%; B2O3 : 0 to 5%; K2O : 0 to 3%; Na2O: 0 to 1%; ZnO: 0 to 3%; TiO2 : 0.5 % to 8%; wherein the mass percentage ratio of ( SiO2 + Li2O ) to Al2O3 is 6 to 15, the mass percentage ratio of Al2O3 to Li2O3 is 6 to 15, and the mass percentage ratio of ( SiO2 + Li2O ) to Al2O3 is 6 to 15. The mass percentage of O is 0.7 to 1.3, the crystalline phase includes a lithium silicate crystalline phase, a lithium feldspar solid solution and/or a lithium feldspar crystalline phase, and the microcrystalline glass is transparent and colorless; for a microcrystalline glass with a thickness of 1 mm, the microcrystalline glass has a transmittance of at least 86% within a wavelength range of 450 nm to 1000 nm.
The glass-ceramics according to claim 1 is characterized in that the lithium silicate crystal phase accounts for 30wt% to 70wt% of the glass-ceramics.
The microcrystalline glass according to claim 1 is characterized in that the lithium silicate crystal phase is lithium disilicate, lithium metasilicate or a combination of the two.
The glass-ceramics according to claim 1, characterized in that, in terms of mass percentage, P 2 O 5 +ZrO 2 <12 wt %.
The glass-ceramics according to claim 1 is characterized in that, in terms of mass percentage, MgO+ZnO＞0.5%.
The microcrystalline glass according to claim 1 is characterized in that, when the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a blocking rate of more than 27% for blue light of 400 nm to 450 nm.
The microcrystalline glass according to claim 1, characterized in that when the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a haze of no more than 0.3%.
The microcrystalline glass according to claim 1 is characterized in that the microcrystalline glass has the following transmission or reflection color coordinates in the CIE L*a*b* colorimetric system: L*≥90, a* is -0.2 to 0.2, and b* is -0.2 to 0.6.
The microcrystalline glass according to claim 1 is characterized in that, at room temperature and a frequency of 2467 MHz, the dielectric loss tangent of the microcrystalline glass is less than or equal to 0.002.
The microcrystalline glass according to claim 1 is characterized in that, at 25°C, the thermal conductivity of the microcrystalline glass is greater than or equal to 2 W/m·K.
The microcrystalline glass according to claim 1, characterized in that the crystallinity of the microcrystalline glass is above 50.
The microcrystalline glass according to claim 11 is characterized in that the crystallinity of the microcrystalline glass is greater than 60%.
The microcrystalline glass according to claim 12 is characterized in that the crystallinity of the microcrystalline glass is greater than 70%.
The microcrystalline glass according to claim 13 is characterized in that the crystallinity of the microcrystalline glass is greater than 80%.
The microcrystalline glass according to claim 14 is characterized in that the crystallinity of the microcrystalline glass is greater than 90%.
The microcrystalline glass according to claim 1 is characterized in that the microcrystalline glass further comprises crystal grains having a longest dimension of 60 nm or less.
The microcrystalline glass according to claim 1 is characterized in that the microcrystalline glass has a fracture toughness of 1 MPa·m 1/2 or greater.
The glass-ceramic according to claim 17, characterized in that the glass-ceramic has a fracture toughness of 1.2 MPa·m 1/2 or greater.
The glass-ceramics according to claim 1, characterized in that the glass-ceramics has a Vickers hardness of 650 kgf/ mm2 or more.
The glass-ceramics according to claim 19, characterized in that the glass-ceramics has a Vickers hardness of 750 kgf/ mm2 or more.
The microcrystalline glass according to claim 20, characterized in that the microcrystalline glass has a Vickers hardness of 800 kgf/ mm2 or more.
The microcrystalline glass according to claim 1 is characterized in that the microcrystalline glass has an elastic modulus of 90 GPa or greater.
The microcrystalline glass according to claim 22 is characterized in that the microcrystalline glass has an elastic modulus of 100 GPa or greater.
The microcrystalline glass according to claim 1, characterized in that the microcrystalline glass is placed at 20°C, After 20 minutes in 10wt% HF solution, the weight loss is no more than 12mg/ cm2 .
The glass-ceramics according to claim 1 is characterized in that when the glass-ceramics is placed in a 95°C, 5wt% HCl solution for 24 hours, its weight loss is no more than 0.06mg/cm2.
The microcrystalline glass according to claim 1 is characterized in that when the microcrystalline glass is placed in a 95°C, 5wt% NaOH solution for 6 hours, its weight loss is no more than 0.14mg/cm2.
The microcrystalline glass according to claim 1 is characterized in that the microcrystalline glass has a surface compressive stress of not less than 200 MPa.
The microcrystalline glass according to claim 27 is characterized in that the microcrystalline glass has a surface compressive stress of not less than 300 MPa.
The microcrystalline glass according to claim 28 is characterized in that the strengthening time is no more than 16 hours and the microcrystalline glass has a compressive stress layer depth of at least 60 microns.
The microcrystalline glass according to claim 29 is characterized in that the strengthening time is no more than 16 hours and the microcrystalline glass has a compressive stress layer depth of at least 80 microns.
The microcrystalline glass according to claim 30 is characterized in that the strengthening time is no more than 16 hours and the microcrystalline glass has a compressive stress layer depth of at least 100 microns.
The microcrystalline glass according to claim 31 is characterized in that the strengthening time is no more than 16 hours and the microcrystalline glass has a compressive stress layer depth of at least 120 microns.
The microcrystalline glass according to claim 32 is characterized in that the strengthening time is no more than 16 hours and the microcrystalline glass has a compressive stress layer depth of at least 140 microns.
The microcrystalline glass according to claim 33 is characterized in that the strengthening time is no more than 12 hours.
The microcrystalline glass according to claim 34 is characterized in that the strengthening time is no more than 8 hours.
The glass-ceramic according to claim 1, characterized in that the glass-ceramic has a central tensile stress of at least 80 MPa.
The microcrystalline glass according to claim 36 is characterized in that the microcrystalline glass has a central tensile stress of at least 90 MPa.
The glass-ceramic according to claim 1 is characterized in that the composition is calculated by mass percentage: It contains: SiO2 : 68% to 75%; Al2O3 : 4% to 7%; Li2O : 7% to 11%; P2O5 : 1% to 8%; ZrO2 : 0.5 % to 6%; MgO: 0 to 6% ; B2O3 : 0 to 5%; K2O : 0 to 3%; Na2O : 0 to 1%; ZnO: 0 to 3%; TiO2 : 0.5% to 8%; the mass percentage ratio of ( SiO2 + Li2O ) to Al2O3 is 6 to 15, and the mass percentage ratio of Al2O3 to Li2O is 0.7 to 1.3.
An electronic device comprises a cover, wherein the cover comprises the microcrystalline glass according to any one of claims 1 to 38.
A microcrystalline glass, characterized in that, in terms of molar percentage, it contains: in terms of mass percentage, it contains: SiO2 : 65% to 78%; Al2O3 : 3 % to 10%; Li2O : 6% to 12%; P2O5 : 1 % to 8%; ZrO2 : 0.5% to 6%; MgO : 0 to 6%; B2O3 : 0 to 5%; K2O : 0 to 3%; Na2O : 0 to 1%; ZnO: 0 to 3%; TiO2 : 0.5% to 8%; wherein the mass percentage ratio of ( SiO2 + Li2O ) to Al2O3 is 6 to 15, and the mass percentage ratio of Al2O3 to Li2O3 is 6 to 15 . The mass percentage of O is 0.7 to 1.3. When the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a transmittance of at least 86% within a wavelength range of 450 nm to 1000 nm. The microcrystalline glass has a fracture toughness greater than 1 MPa·m 1/2 .
The microcrystalline glass described in claim 40 is characterized in that the crystalline phase of the microcrystalline glass includes 30wt% to 70wt% of lithium silicate crystal phase, lithium feldspar solid solution and/or lithium feldspar.
The microcrystalline glass according to claim 40, characterized in that the microcrystalline glass has a Vickers hardness of 650 kgf/ mm2 or more.
The microcrystalline glass according to claim 42, characterized in that the microcrystalline glass has a Vickers hardness of 750 kgf/ mm2 or greater.
The microcrystalline glass according to claim 43, characterized in that the microcrystalline glass has a Vickers hardness of 800 kgf/ mm2 or more.
The microcrystalline glass according to claim 40 is characterized in that the microcrystalline glass has an elastic modulus of 90 GPa or greater.
The microcrystalline glass according to claim 45 is characterized in that the microcrystalline glass has an elastic modulus of 100 GPa or greater.
The glass-ceramic according to claim 40, characterized in that the glass-ceramic is placed at 20°C, After 20 minutes in 10wt% HF solution, the weight loss is no more than 12mg/ cm2 .
The glass-ceramics according to claim 40, characterized in that when the glass-ceramics is placed in a 5 wt % HCl solution at 95° C. for 24 hours, the weight loss is not greater than 0.06 mg/cm 2 .
The glass-ceramics according to claim 40, characterized in that when the glass-ceramics is placed in a 95°C, 5wt% NaOH solution for 6 hours, its weight loss is not greater than 0.14 mg/ cm2 .
The microcrystalline glass according to claim 40 is characterized in that the microcrystalline glass has a surface compressive stress of not less than 200 MPa.
The microcrystalline glass according to claim 40 is characterized in that the strengthening time is no more than 16 hours and the microcrystalline glass has a compressive stress layer depth of at least 80 microns.
The microcrystalline glass according to claim 40 is characterized in that the microcrystalline glass has a central tensile stress of at least 90 MPa.
The microcrystalline glass according to claim 40 is characterized in that when the thickness of the microcrystalline glass is 1 mm, the microcrystalline glass has a haze of no more than 0.3%.
The microcrystalline glass according to claim 40 is characterized in that the microcrystalline glass is colorless and has the following transmission or reflection color coordinates in the CIE L*a*b* colorimetric system: L*≥90, a* is -0.2 to 0.2, and b* is -0.2 to 0.6.
The microcrystalline glass according to claim 40 is characterized in that the crystallinity of the microcrystalline glass is greater than 70%.
The microcrystalline glass according to claim 40 is characterized in that the microcrystalline glass also contains grains, and the grains have a longest dimension of 60nm or less.
The microcrystalline glass according to claim 40 is characterized in that, at room temperature and a frequency of 2467 MHZ, the dielectric loss tangent of the microcrystalline glass is less than or equal to 0.002.
The microcrystalline glass according to claim 40 is characterized in that, at 25°C, the thermal conductivity of the microcrystalline glass is greater than or equal to 2 W/m·K.
An electronic product comprises a covering protective member, wherein the covering protective member comprises the microcrystalline glass as described in any one of claims 40 to 58.
A microcrystalline precursor glass composition, characterized in that the composition, by mass percentage, contains: SiO2 : 65% to 78%; Al2O5 : 3 % to 10%; Li2O : 6% to 12%; P2O5 : 1 % to 8%; ZrO2 : 0.5% to 6%; MgO: 0 to 6%; B2O3: 0 to 5%; K2O : 0 to 3%; Na2O : 0 to 1%; ZnO: 0 to 3%; TiO2 : 0.5% to 8%; wherein the mass percentage ratio of ( SiO2 + Li2O ) to Al2O3 is 6 to 15, and the mass percentage ratio of Al2O3 to Li2O3 is 6 to 15 . The mass percentage of O is 0.7-1.3; the temperature range corresponding to the viscosity of the precursor glass composition of 1000P-10000P is 900°C-1200°C, and the preparation of the precursor glass is suitable for calendering, casting and float forming processes.
The precursor glass composition according to claim 60, characterized in that the thermal expansion coefficient of the precursor glass composition is 7.0×10 -6 / °C to 8.5× 10 -6 /°C at 20°C to 380°C.
The precursor glass composition according to claim 61 is characterized in that the thermal expansion coefficient growth rate of the precursor glass composition is not greater than 6% at 20°C to 600°C.
The precursor glass composition according to claim 61 is characterized in that the softening point of the precursor glass composition is 660°C to 690°C, and 3D hot bending can be performed directly during the crystallization process.
A method for preparing a glass-ceramic as claimed in any one of claims 1 to 39 or 40 to 58, characterized in that it comprises the following steps:

S1, preparing a microcrystalline precursor glass composition, wherein the microcrystalline precursor glass composition comprises the following components in percentage by mass: SiO2 : 65-78%; Al2O3 : 3-10 %; Li2O: 6-12% ; P2O5 : 1-8%; ZrO2 : 0.5-6%; MgO: 0-6%; B2O3: 0-5%; K2O: 0-3%; Na2O : 0-1 %; ZnO : 0-3%; TiO2 : 0.5-8%; wherein the mass percentage ratio of ( SiO2 + Li2O ) to Al2O3 is 6-15, and the mass percentage ratio of Al2O3 to Li2O is 0.7-1.3 ;

S2, performing a microcrystallization heat treatment on the microcrystalline precursor glass composition to form a microcrystalline glass, wherein the crystallinity of the microcrystalline glass is ≥70%, and the crystal phase of the microcrystalline glass is lithium silicate, lithium feldspar solid solution and/or lithium feldspar crystal phase, wherein the microcrystalline glass is transparent, and when the thickness of the microcrystalline glass is 1 mm, the transmittance of the light within the wavelength range of 450 nm to 1000 nm is not less than 86%;

S3, chemically strengthening the microcrystalline glass after the crystallization heat treatment to form a strengthened microcrystalline glass, wherein the strengthened microcrystalline glass has a surface compressive stress of not less than 200 MPa and a compression layer depth of not less than 80 μm.
The method for preparing microcrystalline glass according to claim 64 is characterized in that the microcrystalization heat treatment process includes the following sequential steps: first, the microcrystalline precursor glass composition is heated to the nucleation temperature at a certain heating rate, and maintained at the nucleation temperature for a predetermined time to obtain a nucleated microcrystalline precursor composition; then, the nucleated microcrystalline precursor composition is heated to the crystallization temperature, and maintained at the crystallization temperature for a predetermined time to obtain a crystallized microcrystalline precursor glass composition; finally, the crystallized microcrystalline precursor glass composition is cooled to room temperature at a certain cooling rate to obtain microcrystalline glass.
The method for preparing microcrystalline glass according to claim 64 is characterized in that the chemical strengthening process is to immerse the microcrystalline glass in a single salt bath, wherein the molten salt or salt melt contains at least one ion having a radius larger than the radius of the alkali metal ion in the glass.
According to the method for preparing microcrystalline glass as described in claim 66, the salt bath contains nitrates or sulfates of potassium and sodium.
The method for preparing microcrystalline glass according to claim 64 is characterized in that the chemical strengthening process is to immerse the microcrystalline glass in multiple salt baths with the same or different compositions, wherein the molten salt or salt melt contains at least one ion with a radius larger than the radius of the alkali metal ions in the glass; the salt bath contains nitrates or sulfates of potassium and sodium, and the potassium ion concentration in the latter salt bath is greater than the potassium ion concentration in the former salt bath.