Low-expansion transparent glass ceramic, low-expansion chemically-strengthened transparent glass ceramic, and preparation method and application of low-expansion chemically-strengthened transparent glass ceramic

Abstract

The invention discloses low-expansion transparent glass ceramics, low-expansion chemically-strengthened transparent glass ceramics as well as a preparation method and application of the low-expansion chemically-strengthened transparent glass ceramics. The low-expansion transparent glass ceramic is prepared from the following components in percentage by mass: 40 percent to 48 percent of SiO2, 25 percent to 29.5 percent of Al2O3, 17 percent to 21.5 percent of Na2O, 0 to 1 percent of K2O, 1 percent to 4 percent of Li2O, 2 percent to 6.5 percent of B2O3, 3 percent to 6 percent of ZrO2, 0 to 1 percent of TiO2, 0.5 percent to 5 percent of P2O5, 0 to 1.5 percent of MgO, 0.1 percent to 0.5 percent of SnO2, 0.1 percent to 0.5 percent of La2O3 and 0.01 percent to 0.1 percent of Y2O3. The low-expansion transparent microcrystalline glass provided by the invention has excellent mechanical properties and optical properties so as to meet the requirements of consumer electronics and display screen protection cover plates of vehicle-mounted display devices.

Description

Technical Field

[0001] The present application relates to the technical field of microcrystalline glass, and in particular to a low-expansion transparent microcrystalline glass, a low-expansion chemically strengthened transparent microcrystalline glass, and a preparation method and application thereof. Background Art

[0002] Microcrystalline glass is usually made by adding a certain amount of nucleating agent to the base glass, and then keeping it warm at a certain temperature for a period of time, inducing the crystallization of the microcrystalline glass through the nucleating agent, and precipitating the target crystal phase, thereby obtaining the target microcrystalline glass. However, as a protective cover material for consumer electronic products and smart car on-board display devices, it needs to have excellent optical and mechanical properties, which requires adjusting the optical parameters between the controlled crystal phase and the residual glass phase inside the microcrystalline glass to be close to each other, and at the same time requires that parameters such as grain size and crystal crystallinity be controlled within a certain range. The microcrystalline glass currently available on the market is difficult to meet the above requirements. Therefore, there is an urgent need for a microcrystalline glass that has both excellent mechanical and optical properties to meet the various requirements for screen protection glass used in electronic equipment or on-board display devices. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a low-expansion transparent microcrystalline glass, a low-expansion chemically strengthened transparent microcrystalline glass and a preparation method and application thereof, aiming to solve the problem that the existing microcrystalline glass is difficult to simultaneously have a low linear expansion coefficient, excellent optical properties and mechanical properties.

[0004] The technical solution of this application is as follows:

[0005] In a first aspect of the present application, a low expansion transparent glass-ceramic is provided, wherein the low expansion transparent glass-ceramic comprises the following components, in percentage by mass: SiO2: 40%-48%, Al2O3: 25%-29.5%, Na2O: 17%-21.5%, K2O: 0-1%, Li2O: 1%-4%, B2O3: 2%-6.5%, ZrO2: 3%-6%, TiO2: 0-1%, P2O5: 0.5%-5%, MgO: 0-1.5%, SnO2: 0.1%-0.5%, La2O3: 0.1%-0.5%, Y2O3: 0.01%-0.1%; wherein the components of the low expansion transparent glass-ceramic satisfy at least one of the following relationships: 17.5%≤(Na2O+Li2O+K2O)≤22.50%; 2.50%≤(B2O3+La2O3+Y2O3)≤5.8%; 4.50%≤(ZrO2+TiO2+P2O5)≤8.0%; the low expansion transparent microcrystalline glass satisfies 60≤R≤140, R=[-40×n(Al2O3)+52×n(SiO2)+400×n(Na2O)+100×n(ZrO2)+10×n(B2O3)+260×m(LiO2)+60×n(MgO)] / 100, n is the molar fraction corresponding to the corresponding oxide; the linear thermal expansion coefficient α of the low expansion transparent microcrystalline glass at 0-300°C is ≤106×10 -7 / ℃.

[0006] Optionally, the low-expansion transparent glass-ceramics further includes a clarifier, and the clarifier includes at least one of NaCl, Sb2O3, As2O3, nitrate, and sulfate; in the low-expansion transparent glass-ceramics containing the clarifier, the mass percentage of the clarifier is 0.1%-0.8%.

[0007] Optionally, the main crystalline phase of the low expansion transparent glass-ceramics includes one or more of triclinic nepheline, sodium nepheline, β-quartz solid solution or ZrO2; the average grain size of the crystals of the low expansion transparent glass-ceramics is 20-60nm; the crystallinity of the low expansion transparent glass-ceramics is 25%-65%.

[0008] Optionally, when the thickness T of the low expansion transparent glass-ceramics is ≤0.70 mm, the average transmittance of the low expansion transparent glass-ceramics is ≥86% for light with a wavelength of 360-780 nm.

[0009] Optionally, when the thickness of the low-expansion transparent glass-ceramics is T≤0.70 mm, in the optical color control LAB value, 0.60≤|B value|≤1.50.

[0010] Optionally, when the thickness T of the low expansion transparent glass-ceramics is ≤0.70 mm, the haze is ≤0.18%.

[0011] Optionally, the low-expansion transparent glass-ceramics can withstand a drop height of ≥160 cm and an impact energy of ≥0.30 J in a drop resistance test under impact conditions of a thickness of T=0.70 mm, 80-grit sandpaper, and a load of 200 g.

[0012] The second aspect of the present application provides a method for preparing the low-expansion transparent microcrystalline glass of the first aspect of the present application, comprising the steps of: mixing compounds corresponding to the components of the low-expansion transparent microcrystalline glass, melting at 1500-1580°C for 4-6h, clarifying and homogenizing at 1350-1450°C, molding, and obtaining a basic glass after annealing; subjecting the basic glass to nucleation heat treatment and crystallization heat treatment to obtain the low-expansion transparent microcrystalline glass; wherein the molding method is one of casting, calendering, float method, and overflow method; the temperature of the nucleation heat treatment is 500-580°C, and the time is 180-480min; the temperature of the crystallization heat treatment is 610-680°C, and the time is 15-180min.

[0013] The third aspect of the present application provides a low-expansion chemically strengthened transparent microcrystalline glass, which is obtained by chemically strengthening the low-expansion transparent microcrystalline glass of the first aspect of the present application; the ion strengthening depth of the low-expansion transparent strengthened microcrystalline glass is 120-170μm, and the surface compressive stress CS≥700Mpa.

[0014] In a fourth aspect of the present application, a method for preparing the low expansion chemically strengthened transparent microcrystalline glass of the third aspect of the present application is provided, comprising the steps of: placing the low expansion transparent microcrystalline glass in a molten salt for chemical strengthening treatment to obtain the low expansion transparent microcrystalline glass; the molten salt comprises sodium nitrate, and at least one of potassium nitrate and lithium nitrate; in the molten salt, Na + ≥200000ppm, 0≤Li + ≤100ppm, 0≤K + ≤60000ppm; the temperature of the chemical strengthening treatment is 380-550°C and the time is 1-48h.

[0015] The fifth aspect of the present application provides an application of the low-expansion transparent microcrystalline glass of the first aspect of the present application and the low-expansion chemically strengthened transparent microcrystalline glass of the third aspect of the present application in the preparation of protective cover plates for consumer electronic devices and vehicle-mounted displays, wherein the consumer electronic devices include at least one of mobile phones, tablet computers, smart wearable devices, displays, and televisions.

[0016] Compared with the prior art, this application has the following advantages:

[0017] The present application adjusts the crystal phase composition, average grain size, and crystal ratio of the microcrystalline glass, and simultaneously adds lanthanide oxides and some rare earth oxides to effectively improve the difference between the refractive index of the crystal phase and the refractive index of the remaining glass phase in the microcrystalline glass, and obtains a lower linear expansion coefficient, so that the microcrystalline glass has both excellent mechanical and optical properties to meet the needs of display screen protection covers for consumer electronic products and vehicle-mounted display devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for describing the embodiments are briefly introduced below.

[0019] Figure 1 This is a graph showing the transmittance of the glass-ceramics in Example 1 of the present application to light in the wavelength range of 360nm to 800nm. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings and embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0021] It should be noted that if there are descriptions involving "first", "second", etc. in the implementation of this application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance and implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in the field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0022] Terminology explanation:

[0023] Basic glass: refers to glass that has not been treated with nucleation, crystallization or strengthening.

[0024] Glass-ceramics: also known as glass ceramics, is a type of solid composite material that contains both glass phase and microcrystalline phase / crystalline phase, prepared by targeted controlled crystallization of substrate glass. The microcrystalline phase here is also called crystalline phase or crystal phase in other literature.

[0025] Chemically strengthened glass-ceramics: It is a solid composite material obtained after chemical strengthening treatment of glass-ceramics. It should be understood that during high-temperature chemical strengthening treatment, alkali metal ions with large ionic radius (such as potassium ions and sodium ions) in the salt bath / molten salt / molten salt will replace alkali metal ions with small ionic radius (such as sodium ions and lithium ions) in the glass-ceramics, thereby generating an exchange ion volume difference and generating compressive stress on the surface of the glass-ceramics.

[0026] Crystallinity: The percentage of the mass of the crystalline phase in the microcrystalline glass to the total mass of the microcrystalline glass.

[0027] Coefficient of thermal expansion: CTE for short, refers to the expansion and contraction of an object due to temperature changes. Its ability to change is expressed by the change in length value caused by unit temperature change under constant pressure (constant P), that is, the thermal expansion coefficient. The coefficient of thermal expansion refers to the ratio of the change in length of a solid substance in a certain direction when the temperature changes by 1°C to its length at 20°C (i.e., standard laboratory environment).

[0028] Color control LAB value: used to characterize the yellow-blue value of microcrystalline glass materials. The optical B value in the color control LAB value in this application is the transmitted light B value, and a positive optical B value indicates that the material is blue.

[0029] In order to obtain low-expansion transparent microcrystalline glass materials with the required properties, it is often necessary to add some alkali metal oxides, alkaline earth metal oxides, rare earth elements, etc. to the basic glass system, which makes the composition of the basic glass more complex, resulting in the base glass precipitating not a single crystal but multiple crystals during the crystallization process.

[0030] However, the inventors have found through research that only by controlling one or two of the crystal form, average grain size and crystal ratio, it is not possible to ensure that the microcrystalline glass that meets the optical performance (including transmittance, haze and b value) and mechanical strength performance requirements required for the cover glass material of the display device is obtained, especially when the refractive index of the crystal phase of the microcrystalline glass is significantly different from the refractive index of the glass phase, it will seriously affect the optical performance of the microcrystalline glass. At the same time, low expansion chemically strengthened transparent microcrystalline glass (NAS system) has the characteristics of a large linear thermal expansion coefficient. An excessively large expansion coefficient will lead to a decrease in the processing yield during the cover glass processing process and increase costs.

[0031] Based on this, the embodiment of the present application provides a low expansion transparent glass-ceramics, which includes the following components in percentage by mass:

[0032] SiO2: 40%-48%, Al2O3: 25%-29.5%, Na2O: 17%-21.5%, K2O: 0-1%, Li2O: 1%-4%, B2O3: 2%-6.5%, ZrO2: 3% -6%, TiO2: 0-1%, P2O5: 0.5%-5%, MgO: 0-1.5%, SnO2: 0.1%-0.5%, La2O3: 0.1%-0.5%, Y2O3: 0.01%-0.1%.

[0033] Among them, SiO2 is one of the main components of the network oxide of base glass and microcrystalline glass, one of the important components that constitute Si-O tetrahedron in the main body and form a network structure, and is also one of the components of sodium nepheline crystals. The mass percentage of SiO2 in the low expansion transparent microcrystalline glass in the embodiment of the present application is 40%-48%, which can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, and any value in the range composed of any two of the above values.

[0034] Al2O3 is an intermediate oxide in the formation of glass and one of the elements involved in the sodium nepheline crystal. It can significantly improve the thermal stability of the base glass and the microcrystalline glass. At the same time, since [AlO4] is larger in volume than [SiO4], it can provide a larger space for ion exchange. Therefore, alumina can promote the ion exchange. The mass percentage of Al2O3 in the low-expansion transparent microcrystalline glass of the embodiment of the present application is 25%-29.5%, which can be 25.0%, 26%, 27%, 28%, 29%, 29.5%, and any value in the range of any two of the above values.

[0035] Further, the components of the low expansion transparent glass-ceramics satisfy at least one of the following relationships:

[0036] 17.5%≤(Na2O+Li2O+K2O)≤22.50%;

[0037] 2.50%≤(B2O3+La2O3+Y2O3)≤5.8%;

[0038] 4.50%≤(ZrO2+TiO2+P2O5)≤8.0%.

[0039] Among them, the total mass percentage of the three alkali metal oxides Na2O+Li2O+K2O is 17.5%-22.5%. This ratio can not only ensure the controlled crystal precipitation, but also ensure the chemical strengthening of the microcrystalline glass, and can also promote glass melting and reduce energy loss. The three have different functions:

[0040] Na2O is an important participating element in sodium nephrite crystals, and is also an important participating element in ion exchange chemical strengthening of microcrystalline glass to obtain strengthened microcrystalline glass. It can also be used as a flux when the base glass is melted at high temperature, which can significantly reduce the melting temperature of the base glass. However, when the Na2O content is too high, the chemical stability of the microcrystalline glass is significantly reduced. Therefore, the mass percentage of Na2O in the low expansion transparent microcrystalline glass in the embodiment of the present application is 17%-21.5%, which can be 17%, 18%, 19%, 20%, 21%, 21.5%, and any value in the range composed of any two of the above values. At this time, the melting temperature can be kept within an appropriate range, and good ion exchange properties can be guaranteed. At the same time, there is enough Na element to participate in the formation of sodium nephrite crystals.

[0041] K2O can reduce the high-temperature viscosity of the base glass, significantly improve the formability and fluidity of the base glass at high temperatures, and significantly reduce the incidence of cracks. Among them, a small amount of K2O can slow down the crystallization behavior that occurs when the microcrystalline glass is formed. The mass percentage of K2O in the low-expansion transparent microcrystalline glass of the embodiment of the present application is 0-1%, which can be 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, and any value in the range composed of any two of the above values.

[0042] Li2O is an oxide with high alkali metal activity and is an external oxide of the glass network. As one of the additives to reduce the high temperature viscosity of the base glass, it can significantly improve the high temperature fluidity of the base glass. + In the low-expansion transparent glass-ceramics of the embodiment of the present application, ion exchange chemical strengthening reaction can be involved to further enhance the mechanical properties of the glass-ceramics. The mass percentage of Li2O in the low-expansion transparent glass-ceramics of the embodiment of the present application is 1%-4%, which can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, and any value in the range composed of any two of the above values.

[0043] B2O3+La2O3+Y2O3 are important lanthanide metal oxides and rare earth oxides that improve the optical properties of the low expansion transparent glass-ceramics of the present application. The total mass percentage of the three is 2.5%-5.8%, and each of the three has different functions:

[0044] B2O3, as a network exosome oxide of glass, is generally filled in the voids of the silicon-oxygen tetrahedral framework. Its cation coordination rarely changes, and some properties of its oxide can be considered constant. B2O3 helps to provide a base glass with a low melting temperature. In addition, adding B2O3 to the base glass can also improve the damage resistance of the microcrystalline glass and reduce the thermal expansion coefficient of the glass, but too much B2O3 will destroy the stability of the base glass. The mass percentage of B2O3 in the low expansion transparent microcrystalline glass of the embodiment of the present application is 2-6.5%, which can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, and any value in the range composed of any two of the above values.

[0045] La2O3, as a lanthanide metal oxide, is an important component of optical glass and can effectively improve the refractive index and dispersion of glass. The mass percentage of La2O3 in the low-expansion transparent microcrystalline glass in the embodiment of the present application is 0.1-0.5%, which can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and any value in the range composed of any two of the above values.

[0046] Y2O3 is also a rare metal oxide, which is a network external oxide and affects the thermal expansion coefficient of glass. 3+ Outside the network, due to its high electric field strength, it accumulates the surrounding silicon-oxygen tetrahedrons, hindering the expansion of the glass skeleton caused by thermal vibration, so the thermal expansion coefficient also decreases. The mass percentage of Y2O3 in the low-expansion transparent microcrystalline glass of the embodiment of the present application is 0.01-0.10%, which can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, and any value in the range composed of any two of the above values.

[0047] ZrO2+TiO2+P2O5 are used as nucleating agents, and the total mass percentage of the three is 4.5%-8%, which can be 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, and any value in the range composed of any two of the above values. TiO2, ZrO2 and P2O5 can be used as nucleating agents alone or in combination of two or three, which can improve the crystallization ability of microcrystalline glass and produce a large number of uniform and fine crystals in a shorter time of microcrystallization treatment. Specifically, the mass percentage of ZrO2 in the low expansion transparent microcrystalline glass of the embodiment of the present application is 3%-6%, which can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, and any value in the range composed of any two of the above values. The mass percentage of TiO2 in the low expansion transparent glass-ceramics of the embodiment of the present application is 0-1%, and can be 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, and any value in the range of any two of the above values. The mass percentage of P2O5 in the low expansion transparent glass-ceramics of the embodiment of the present application is 0.5%-5%, and can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and any value in the range of any two of the above values.

[0048] As a component of some basic glasses, MgO can improve the crystallization ability of the crystal in a certain amount, and MgO has the effect of reducing the difficulty of melting and improving the hardness of the glass. The mass percentage of MgO in the low expansion transparent microcrystalline glass of the embodiment of the present application is 0-1.5%, which can be 0, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.3%, 1.4%, 1.5%, and any value in the range of any two of the above values.

[0049] SnO2 is a commonly used clarifier that can clarify and homogenize the base glass, making the distribution of the components in the base glass more uniform. The mass percentage of SnO2 in the low expansion transparent glass-ceramics of the present application embodiment is 0.1%-0.5%, which can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and any value in the range of any two of the above values.

[0050] At the same time, the low-expansion transparent microcrystalline glass in the embodiment of the present application satisfies 60≤R≤140, R=[-40×n(Al2O3)+52×n(SiO2)+400×n(Na2O)+100×n(ZrO2)+10×nB2O3+260×nLiO2+60×n(MgO) / 100, n is the molar fraction corresponding to the corresponding oxide.

[0051] R value is a method to judge the trend of thermal expansion change, which can be calculated by adding the thermal expansion coefficients of the main oxides. Too high R value will increase the expansion coefficient of the base glass, which is prone to breakage during the molding process. Too low R value will change the overall glass composition, resulting in failure to obtain the expected target crystal phase during subsequent heat treatment.

[0052] The linear thermal expansion coefficient of the low expansion transparent glass-ceramics in the embodiment of the present application at 0-300°C is α≤106×10 -7 / ℃.

[0053] In some embodiments, the low expansion transparent glass-ceramics further comprises 0.1%-0.8% of a clarifier, measured by mass percentage, wherein the clarifier comprises at least one of NaCl, Sb2O3, As2O3, nitrates and sulfates; the sum of the mass percentages of the components of the low expansion transparent glass-ceramics containing the clarifier is 100%.

[0054] In some embodiments, the main crystalline phase of the low expansion transparent glass-ceramics includes one or more of triclinic nepheline, sodium nepheline, β-quartz solid solution or ZrO2. The average grain size of the crystals of the low expansion transparent glass-ceramics is 20-60nm, which can be 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, and any value in the range of any two of the above values. The crystallinity of the low expansion transparent glass-ceramics is 25%-65%, which can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, and any value in the range of any two of the above values.

[0055] In some embodiments, when the low expansion transparent glass-ceramics has a thickness T≤0.70 mm, the average transmittance for light with a wavelength of 360-780 nm is ≥86%. Preferably, the average transmittance is ≥89%.

[0056] In some embodiments, when the low expansion transparent glass-ceramics has a thickness T≤0.70 mm, in the optical color control LAB value, 0.60≤|B value|≤1.50. Preferably, 0.60≤|B value|≤1.20.

[0057] In some embodiments, when the thickness T of the low expansion transparent glass-ceramics is ≤0.70 mm, the haze is ≤0.18%, preferably ≤0.15%.

[0058] In some embodiments, when the low expansion transparent glass-ceramics has a thickness of T=0.70 mm, in a drop test under the impact conditions of 80-grit sandpaper and a 200 g weight, it can withstand a height of ≥160 cm and an impact energy of ≥0.30 J.

[0059] A second aspect of the embodiment of the present application provides a method for preparing the low expansion transparent glass-ceramics as described above, comprising the steps of:

[0060] S1: Evenly mix the compounds corresponding to the percentage of the oxide components of the glass-ceramics, melt them at 1500-1580°C for 4-6h, and then clarify and homogenize them at 1350-1450°C, shape them, and obtain the basic glass after sufficient annealing.

[0061] Wherein, the molding method is any one of casting, calendering, float method and overflow method. The melting temperature can be 1500°C, 1510°C, 1520°C, 1530°C, 1540°C, 1550°C, 1560°C, 1570°C, 1580°C, and any value in the range composed of any two of the above values. The melting time can be 4h, 4.5h, 5h, 5.5h, 6h, and any value in the range composed of any two of the above values. The clarification and homogenization temperature can be 1350°C, 1370°C, 1400°C, 1430°C, 1450°C, and any value in the range composed of any two of the above values.

[0062] S2: The base glass obtained in S1 is subjected to nucleation heat treatment and crystallization heat treatment to obtain low expansion transparent microcrystalline glass.

[0063] Wherein, the temperature of the nucleation heat treatment is 500-580°C, which can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, and any value in the range formed by any two of the above values. The nucleation time is 180-480min, which can be 180min, 200min, 240min, 280min, 300min, 320min, 350min, 400min, 430min, 450min, 480min, and any value in the range formed by any two of the above values. The temperature of the crystallization heat treatment is 610-680°C, which can be 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, and any value in the range formed by any two of the above values. The time of the crystallization heat treatment is 15-180 min, and can be 15 min, 50 min, 75 min, 100 min, 120 min, 150 min, 160 min, 170 min, 180 min, and any value in the range formed by any two of the above values.

[0064] The present application also provides a low expansion chemically strengthened transparent microcrystalline glass, which is obtained by subjecting the low expansion transparent microcrystalline glass as described above to chemical strengthening treatment, wherein the ion strengthening depth DOL of the low expansion transparent strengthened microcrystalline glass is 120-170 μm, and the surface compressive stress CS is ≥700 MPa.

[0065] The embodiment of the present application also provides a method for preparing the low-expansion chemically strengthened transparent microcrystalline glass as described above, comprising the steps of placing the low-expansion transparent microcrystalline glass in a molten salt for salt bath (chemical strengthening treatment) to obtain the low-expansion transparent microcrystalline glass.

[0066] The molten salt includes sodium nitrate, potassium nitrate and lithium nitrate. + ≥200000ppm, 0≤Li + ≤100ppm, 0≤K + ≤60000ppm. The temperature of the chemical strengthening treatment is 380-550°C, and can be 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 550°C, and any value in the range consisting of any two of the above values. The time of the chemical strengthening treatment is 1-48h, and can be 1h, 2h, 4h, 8h, 10h, 12h, 16h, 18h, 24h, 36h, 48h, and any value in the range consisting of any two of the above values. Preferably, the chemical strengthening treatment time is 1-12h.

[0067] Through ion exchange, a compressive stress layer with a certain depth is formed on the surface of the microcrystalline glass, and at the same time, a tensile stress layer that can achieve force balance with the compressive stress layer is formed inside the microcrystalline glass. It should be understood that after the chemical strengthening ion exchange process, the composition of the stress layer formed by the microcrystalline glass may be slightly different from that of the microcrystalline glass that has not undergone ion exchange. This is because during ion exchange, the small-radius alkali metal ions (such as Li + Or Na + ) will be affected by the large radius alkali metal ions (such as Na + or K + ) are replaced by, such as Li in glass-ceramics + and Na in the salt bath molten salt + Exchange, by Na + Replaced by, and / or, Na in glass + K in the molten salt for strengthening + Exchange, K + However, in some embodiments, the composition of the glass-ceramics at the center of the depth of the glass article or near the center of the depth still has the composition of the newly formed glass-ceramics. That is, the composition of the tensile stress layer in the chemically strengthened glass-ceramics that has not undergone ion exchange still has the composition of the glass-ceramics.

[0068] The embodiments of the present application also provide an application of the low-expansion transparent microcrystalline glass as described above and the low-expansion chemically strengthened transparent microcrystalline glass as described above in the preparation of protective cover plates for consumer electronic devices and vehicle-mounted displays.

[0069] The consumer electronic device includes at least one of a mobile phone, a tablet computer, a smart wearable device, a display, and a television. The electronic device or the vehicle-mounted display device may include a housing and an electronic component partially located in the housing, the housing includes a front surface, a rear surface, and a side surface, and the electronic component includes a display device, which is located at the front surface of the housing or adjacent to the front surface.

[0070] Specifically, low expansion transparent glass-ceramics and low expansion chemically strengthened transparent glass-ceramics can be applied to the front surface or / and rear surface or / and side surface of the housing. Preferably, the electronic device or vehicle-mounted display device may also include a covering product covering the front surface of the housing or located on the display device.

[0071] The following is further described by means of specific examples.

[0072] Examples 1-9

[0073] Weigh the raw materials according to the mass percentage of each component in Table 1 and mix them evenly; place the mixed raw materials in an alumina crucible, melt them at a temperature of 1500-1580°C, and keep them warm for 3-8 hours to prepare a molten liquid; homogenize and shape the molten liquid, and then anneal it at a temperature of 300-500°C for 4-6 hours to obtain a basic glass; put the basic glass into a muffle furnace, keep it warm at a temperature of 500-580°C for 3-8 hours, perform a nucleation heat treatment, and then keep it warm at a temperature of 610-680°C for 0.25-3 hours, perform a crystallization heat treatment, and obtain a low expansion chemically strengthened transparent microcrystalline glass.

[0074] The low expansion chemically strengthened transparent microcrystalline glass is cut into glass sheets with a thickness of 0.7-1.0 mm, and then ground and polished to obtain glass sheets with a thickness of 0.5-0.8 mm; the glass sheets are placed in molten salt at a temperature of 380-550°C and treated for 1-48 hours to perform chemical strengthening to obtain low expansion chemically strengthened transparent microcrystalline glass.

[0075] Table 1 Composition of low expansion transparent glass-ceramics

[0076]

[0077]

[0078] Table 2 Melting temperature and heat treatment parameters of low expansion transparent glass-ceramics

[0079]

[0080] Table 3 Chemical strengthening parameters

[0081]

[0082]

[0083] Test Example 1

[0084] Test method:

[0085] (1) Optical performance test. A microcrystalline glass polished sheet with a length, width and thickness of 50 mm × 50 mm × 0.70 mm was cleaned in an ultrasonic cleaning machine. The cleaning conditions are as follows: the cleaning time is 5 min, the cleaning agent used is deionized water, the cleaning temperature is 50°C, and the cleaning frequency is 40 KHz. After cleaning, the test is carried out with reference to the test method of the national standard GB / T 7962.122010 "Test Method for Colorless Optical Glass Part 12: Spectral Transmittance", and the transmittance and optical B value of the microcrystalline glass polished sheet are tested using a haze meter. The haze meter used in this application is a Japanese Konica Minolta spectrophotometer CM3600A, the light receiving optical system is transmission, the spectral mode is a diffraction grating, the wavelength range is 360740 nm, the wavelength spacing is 10 nm, the illumination light source is a pulsed xenon lamp X4, the ambient temperature of the instrument is 24°C, and the air humidity is 40%. For example, the transmittance of the low expansion transparent glass-ceramics prepared in Example 1 in the wavelength range of 360nm to 800nm ​​was tested, and the results were as follows: Figure 1 shown.

[0086] (2) Test of grain size and its distribution. A microcrystalline glass polished sheet with a length, width and thickness of 10 mm × 10 mm × 0.70 mm was selected as the test sample. The selected microcrystalline glass polished sheet was soaked in a 5wt% hydrofluoric acid solution at 20°C for 40 seconds, and then the microcrystalline glass polished sheet was taken out, ultrasonically cleaned and dried. After being soaked and corroded in the hydrofluoric acid solution, the glass phase on the surface of the microcrystalline glass polished sheet will be removed, and the grains will be clearly visible. After that, gold is sprayed on the surface of the dried microcrystalline glass polished sheet, and a JEOL cold field emission scanning electron microscope (SEM) with model JSM7500F is used to obtain the surface morphology of the microcrystalline glass polished sheet with clear grain boundaries. The magnification of the photograph after shooting is 100KX. The "hydrofluoric acid solution" here refers to a diluted hydrofluoric acid solution.

[0087] (3) Stress test. Using the stress meter SLP2000 of Japan Orihara, the test was carried out in accordance with the test method of the national standard GBT 18144 2008 "Glass Stress Test Method", and the compressive stress layer depth DOL_0 and the compressive stress at a depth of 50μm (denoted as C5_50) of the chemically strengthened microcrystalline glass were tested. When the stress test was carried out in this application, a chemically strengthened microcrystalline glass sample with a length, width and thickness of 50mm×50mm×0.7mm was tested. During the test, the light source wavelength was selected to be 518nm, SOC=25.0(nm / cm) / MPa, refractive index=1.54, and exposure time: 300usec. When testing the surface CS_50 and DOL_0, it is necessary to drip a conductive liquid on the stress meter, then wipe the chemically strengthened microcrystalline glass sample clean, place it on the test path, and test its value. SLP2000 uses a conductive liquid with a refractive index of 1.51.

[0088] (4) Photoelastic coefficient (SOC) test. Photoelasticity mainly refers to the phenomenon of anisotropy and birefringence of transparent materials after being subjected to force. By measuring the photoelastic coefficient and birefringence, the value of the residual stress (MPa) inside the material can be obtained.

[0089] (5) Drop resistance test. Average sandpaper drop resistance height h: refers to the ratio of the sum of the sandpaper drop resistance heights of each sample of the same microcrystalline glass samples to the number of microcrystalline glass samples, which is used to characterize the drop resistance performance of microcrystalline glass. At least 10 identical microcrystalline glass samples are tested each time, and the average sandpaper drop resistance height is calculated, where n is the number of microcrystalline glass samples tested in each batch, and h is the average sandpaper drop resistance height. i The sandpaper drop resistance height of a single sample test.

[0090] Among them, the test method for the sandpaper drop height of a single sample is as follows: Step 1: Paste 80-grit sandpaper on the lower surface of a 200g model machine, and place the model machine on a green figure LT SKDLCD drop machine. Step 2: Place a microcrystalline glass sample to be tested with a length, width and thickness of 50mm×50mm×0.7mm directly below the model machine, so that the microcrystalline glass sample faces the sandpaper. Make the model machine fall at a certain drop height to impact the microcrystalline glass sample directly below the model machine. If the microcrystalline glass sample does not break, the drop height of the model machine is increased according to a certain rule. For example, the drop height starts from 40cm, and the microcrystalline glass sample is dropped and impacted once. If it does not break, increase the height by 10cm each time and drop again until the microcrystalline glass sample breaks. Step 3: The last drop height when the glass sample is broken is recorded as the sandpaper drop height. For example, if the drop height when it is broken is 100cm, the sandpaper drop height of the sample is 90cm.

[0091] (6) Crystal phase test. The microcrystalline glass sheet is ground into glass fine powder with a grinding machine. The maximum size of the fine powder particles is less than 75μm. Then, an X-ray diffractometer (Rigaku Smartlab X) is used to test it under the conditions of a diffraction angle range of 2θ=10°80°, a scanning speed of 10° / min, a working voltage of 40kV, and a working current of 30mA to obtain an XRD diffraction peak curve. The XRD diffraction data is then analyzed using the professional processing software Jade to analyze the crystal phase contained in the microcrystalline glass. At the same time, the glass diffraction peak curve is fitted to obtain the total crystal phase content in the microcrystalline glass. Specifically, the method for obtaining the crystal phase content is as follows: import the X-ray diffractometer test result file (RAW format) into the X-ray diffraction data Rietveld refinement software Jade, perform fitting and calculation, and the total crystal phase content in the microcrystalline glass can be obtained. The ratio of the fitted crystal phase peak area to the total fitted peak area is the total crystal phase content, also known as crystallinity.

[0092] In the above test method, after the microcrystalline glass bricks in the embodiments and comparative examples are shaped, cut and polished, microcrystalline glass samples (microcrystalline glass polished sheets) of desired sizes can be obtained and then tested, such as microcrystalline glass polished sheets with a length, width and thickness of 50mm×50mm×0.7mm, 10mm×10mm×1.0mm and 50mm×50mm×0.64mm.

[0093] (7) Thickness test: In this application, a micrometer is used to test the thickness of the transparent glass-ceramics.

[0094] (8) 0-300℃ linear thermal expansion coefficient test. Linear expansion coefficient (α 0℃-300℃ ) The data of 0°C-300°C are tested according to the national standard "GB / T7962.16-2010". In this application, the linear expansion coefficient is sometimes referred to as the expansion coefficient.

[0095] The low expansion transparent glass-ceramics and low expansion chemically strengthened transparent glass-ceramics prepared in Examples 1-9 were tested using the above test method. The test results are shown in Tables 4-6:

[0096] Table 4. Phase composition, crystal size and crystallization degree of low expansion chemically strengthened transparent glass-ceramics

[0097]

[0098]

[0099] Table 5. Performance index of low expansion chemically strengthened transparent microcrystalline glass

[0100]

[0101] Table 6. Drop resistance test of low expansion chemically strengthened transparent microcrystalline glass

[0102]

[0103]

[0104] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A low expansion transparent glass-ceramic, characterized in that: The low expansion transparent glass-ceramics comprises the following components in percentage by mass: SiO2: 40%-48%, Al2O3: 25%-29.5%, Na2O: 17%-21.5%, K2O: 0-1%, Li2O: 1%-4%, B2O3: 2%-6.5%, ZrO2: 3% -6%, TiO2: 0-1%, P2O5: 0.5%-5%, MgO: 0-1.5%, SnO2: 0.1%-0.5%, La2O3: 0.1%-0.5%, Y2O3: 0.01%-0.1%; Wherein, the components of the low expansion transparent glass-ceramics satisfy at least one of the following relationships: 17.5%≤(Na2O+Li2O+K2O)≤22.50%; 2.50%≤(B2O3+La2O3+Y2O3)≤5.8%; 4.50%≤(ZrO2+TiO2+P2O5)≤8.0%; The low expansion transparent glass-ceramics satisfies 60≤R≤140, R = [-40 × n (Al2O3) + 52 × n (SiO2) + 400 × n (Na2O) + 100 × n ZrO2 + 10 × n B2O3 + 260 × n LiO2 + 60 × n (MgO) / 100, n is the molar fraction of the corresponding oxide; The linear thermal expansion coefficient of the low expansion transparent glass-ceramics at 0-300°C is α≤106×10 -7 / ℃.

2. The low expansion transparent glass-ceramics according to claim 1, characterized in that: The low expansion transparent glass-ceramics further comprises a clarifier, wherein the clarifier comprises at least one of NaCl, Sb2O3, As2O3, nitrate and sulfate; In the low expansion transparent glass-ceramics containing a clarifier, the mass percentage of the clarifier is 0.1%-0.8%.

3. The low expansion transparent glass-ceramics according to claim 1, characterized in that: The main crystalline phase of the low expansion transparent glass-ceramics includes one or more of triclinic nepheline, sodium nepheline, β-quartz solid solution or ZrO2; The average grain size of the low expansion transparent glass-ceramics is 20-60 nm; The low expansion transparent glass-ceramics has a crystallinity of 25%-65%.

4. The low expansion transparent glass-ceramics according to claim 1, characterized in that: When the thickness T of the low expansion transparent microcrystalline glass is less than or equal to 0.70 mm, the average transmittance of the low expansion transparent microcrystalline glass for light with a wavelength of 360-780 nm is greater than or equal to 86%.

5. The low expansion transparent glass-ceramics according to claim 1, characterized in that: When the thickness of the low expansion transparent glass-ceramics is T≤0.70 mm, in the optical color control LAB value, 0.60≤|B value|≤1.

50.

6. The low expansion transparent glass-ceramics according to claim 1, characterized in that: When the thickness T of the low expansion transparent glass-ceramics is ≤0.70 mm, the haze is ≤0.18%.

7. The low expansion transparent glass-ceramics according to claim 1, characterized in that: In a drop resistance test under the impact conditions of thickness T=0.70mm, 80-grit sandpaper, and a counterweight of 200g, the low-expansion transparent microcrystalline glass can withstand a height of ≥160cm and an impact energy of ≥0.30J.

8. A method for preparing the low expansion transparent glass-ceramics according to any one of claims 1 to 7, characterized in that: Includes steps: The compounds corresponding to the components of the low expansion transparent glass-ceramics are mixed, melted at 1500-1580° C. for 4-6 hours, clarified and homogenized at 1350-1450° C., formed, and annealed to obtain the basic glass; The base glass is subjected to nucleation heat treatment and crystallization heat treatment to obtain the low expansion transparent microcrystalline glass; Wherein, the molding method is one of casting, calendering, float method and overflow method; The temperature of the nucleation heat treatment is 500-580° C., and the time is 180-480 min; the temperature of the crystallization heat treatment is 610-680° C., and the time is 15-180 min.

9. A low expansion chemically strengthened transparent microcrystalline glass, characterized in that: Made by chemically strengthening the low expansion transparent glass-ceramics according to any one of claims 1 to 7; The ion strengthening depth of the low expansion transparent strengthened glass-ceramics is 120-170 μm, and the surface compressive stress CS is ≥700 MPa.

10. A method for preparing the low expansion chemically strengthened transparent glass-ceramics according to claim 9, characterized in that: The method comprises the following steps: placing the low expansion transparent glass-ceramics in molten salt for chemical strengthening treatment to obtain the low expansion transparent glass-ceramics; The molten salt includes sodium nitrate, and at least one of potassium nitrate and lithium nitrate; In the molten salt, Na + ≥200000ppm, 0≤Li + ≤100ppm, 0≤K + ≤60000ppm; The temperature of the chemical strengthening treatment is 380-550° C. and the time is 1-48 hours.

11. Use of the low-expansion transparent glass-ceramics described in any one of claims 1 to 7 and the low-expansion chemically strengthened transparent glass-ceramics described in claim 9 in the preparation of protective cover plates for consumer electronic devices and vehicle-mounted displays, wherein the consumer electronic devices include at least one of mobile phones, tablet computers, smart wearable devices, displays, and televisions.

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