Glass ceramic, toughened glass ceramic and preparation method and application thereof

Abstract

The invention relates to the technical field of ceramic glass, and discloses glass ceramic, tempered glass ceramic and a preparation method and application thereof. The glass ceramic comprises main crystalline phases, namely a netsagnite crystalline phase, a tricaphorite crystalline phase and a lithium cyanite crystalline phase; the lithium cyanite crystal phase accounts for L in the total crystal phase of the glass ceramic, and L is more than 0% and less than or equal to 30%; the average grain size of the lithium cyanite crystal phase is less than or equal to 25nm; the secondary crystal phase is one or more of beta-quartz solid solution, sodium silicate and zirconium oxide; the average grain size of the glass ceramic is 20-55 nm, and the overall crystallinity is 35-70%; in the glass ceramic, in the residual glass phase, the proportion M of Na2O in the residual glass phase in the glass ceramic is greater than or equal to 0.00% and less than or equal to 10.00%; and the ratio of Li2O is greater than or equal to 3.0% and less than or equal to 15.0%. The problems that the overall thermal expansion coefficient is high and the product yield is low due to the fact that the sodium content of existing glass ceramics of a conventional NAS system is too high are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of glass ceramics, and in particular to a glass ceramic, a strengthened glass ceramic, and a preparation method and application thereof. Background Art

[0002] In recent years, glass ceramics (LAS) with lithium as the main crystal form have gradually been widely used as a new type of material for the screen protection covers of consumer electronic products and in-vehicle display devices. They can have excellent mechanical properties while meeting the excellent optical properties required by display devices. However, in the glass ceramics of the LAS system, the content of Li + is very high, resulting in high raw material costs and being inconvenient for wide promotion. For conventional glass ceramics of the NAS system, although Na + replaces Li + , due to the too high sodium content, the overall thermal expansion coefficient is relatively high, and the product yield is low. At the same time, the high content of sodium will affect the strength of the glass network structure and is not conducive to chemical strengthening.

[0003] Therefore, the existing technology still needs to be further improved and enhanced. Summary of the Invention

[0004] In view of the above deficiencies of the existing technology, the purpose of the present invention is to provide a glass ceramic, a strengthened glass ceramic, and a preparation method and application thereof. The aim is to solve the problem that for conventional glass ceramics of the NAS system, due to the too high sodium content, the overall thermal expansion coefficient is relatively high, and the product yield is low.

[0005] The above object of the present invention is achieved by the following technical solution: A glass ceramic includes a first crystal phase and a second crystal phase. Among them, the first crystal phase includes: nepheline crystal phase, carnegieite crystal phase, and eucryptite crystal phase;

[0006] The proportion of the eucryptite crystal phase in the total crystal phase of the glass ceramic is L, 0% < L ≤ 30%; the average grain size of the eucryptite crystal phase ≤ 25 nm;

[0007] The second crystal phase is selected from one or more of β - quartz solid solution, sodium silicate, and zirconia;

[0008] The average grain size of the glass ceramic is 20 nm to 55 nm, and the overall crystallinity is 35% to 70%;

[0009] In the glass ceramic, in the residual glass phase except for the crystals, the proportion of Na2O in the residual glass phase of the glass ceramic is denoted as M, and the value of M is 0.00% ≤ M ≤ 10.00%; the proportion of Li2O in the residual glass phase of the glass ceramic is denoted as N respectively, and the value of N is 3.0% ≤ N ≤ 15.0%.

[0010] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0011] As a preferred technical solution, for the glass-ceramic, in terms of the molar percentage of oxides, the glass-ceramic contains the following percentages of oxides:

[0012] SiO2: 42.00 - 52.00%,

[0013] Al2O3: 16.00 - 21.00%,

[0014] Na2O: 12.00 - 21.00%,

[0015] ZrO2: 1.00 - 3.50%,

[0016] TiO2: 0.00 - 2.00%,

[0017] P2O5: 1.00 - 5.00%,

[0018] CaO: 0.00 - 2.00%,

[0019] Li2O: 8.00 - 16.00%,

[0020] K2O: 0.00 - 2.00%,

[0021] SnO2: 0.20 - 1.00% and B2O3: 0 - 3.00%;

[0022] The components of the glass-ceramic in terms of the molar ratio of each oxide also satisfy one of the following relationships:

[0023] 60% ≤ (SiO2 + Al2O3) ≤ 72%; 0.75 ≤ (Na2O / Li2O) ≤ 2.50; 24.0 ≤ (Na2O + Li2O + K2O) ≤ 28.50.

[0024] As a preferred technical solution, for the glass-ceramic, the glass-ceramic further contains 0.1 - 0.80% of a fining agent, and the fining agent is selected from one or more of NaCl, Sb2O3, As2O3, nitrates, and sulfates; the sum of the percentages of the components of the transparent glass-ceramic containing the fining agent is 100%.

[0025] A method for preparing the above-mentioned glass-ceramic, which includes:

[0026] Weigh each of the above oxides in terms of molar percentage of oxides, mix them evenly, and melt them at 1500 - 1600 °C for 4 - 6 h to obtain a molten liquid;

[0027] Clarify and homogenize the molten liquid at 1350 - 1450 °C, form it, and obtain the base glass after annealing;

[0028] Perform nucleation heat treatment and crystallization heat treatment on the base glass to obtain the glass - ceramic.

[0029] As a preferred technical solution, in the preparation method of the glass - ceramic, the annealing temperature is 400 - 480 °C, and the annealing holding time is 6 - 168 hours; the nucleation temperature of the nucleation heat treatment is 510 - 590 °C, and the holding time is 60 - 600 min; the crystallization temperature of the crystallization heat treatment is 620 - 700 °C, and the holding time is 10 - 360 min.

[0030] As a preferred technical solution, in the preparation method of the glass - ceramic, the heating rate during the nucleation heat treatment and the crystallization heat treatment is 1 - 10 °C / min.

[0031] A strengthened glass - ceramic, wherein the strengthened glass - ceramic is obtained by chemically strengthening the above - mentioned glass - ceramic.

[0032] As a preferred technical solution, in the strengthened glass - ceramic, the chemical strengthening treatment includes: putting the glass - ceramic into molten salt in a molten state for ion - exchange chemical strengthening to obtain a strengthened glass;

[0033] The molten salt contains sodium ions or any two of sodium ions, lithium ions and potassium ions;

[0034] The temperature of the molten salt is 380 - 560 °C; the ion - exchange time is 1 - 36 h.

[0035] As a preferred technical solution, in the strengthened glass - ceramic, when the thickness of the strengthened glass - ceramic is between 0.50 nm and 1.00 nm, DOL_0≥135 um, CS_50≥145 Mpa; |CT - AV|≥70 Mpa, CT - CV≥100 Mpa, CT - LD≥48000 Mpa / mm, and the impact energy E that a single body can withstand is ≥0.3 joules;

[0036] The transmittance Tr of the strengthened glass - ceramic in the wavelength range of 400 - 1000 nm is ≥89.00%, the haze Haze≤0.15%; and 0.6≤|B|≤1.2 for the color index LAB value.

[0037] A glass-ceramic as described above, or a strengthened glass-ceramic as described above, or a glass-ceramic prepared by the preparation method as described above, is used as a material for preparing a screen protection cover plate of a consumer electronic product or an in-vehicle display device.

[0038] Advantages: Compared with the prior art, the glass-ceramic provided by the present invention has nepheline, carnegieite and eucryptite as the main crystal phases. By controlling the crystal form, size and proportion of the internal nanocrystals in the whole glass-ceramic, especially by controlling: the proportion of eucryptite in the crystal phase and the average grain size of eucryptite. Controlling them within a certain range can obtain a glass-ceramic with high optical properties, meeting the optical property requirements of consumer electronic products and in-vehicle display devices. At the same time, the overall thermal expansion coefficient of the glass-ceramic is reduced, and the product yield is improved. Description of the Drawings

[0039] Figure 1 is the X-ray diffraction pattern of the glass-ceramic of Example 3 of the present invention;

[0040] Figure 2 is the transmittance curve of the glass-ceramics of Example 1 and Comparative Example 1 of the present invention in the range of 400nm to 1000nm. Detailed Embodiments

[0041] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way restrictive of the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] It should be noted that the terms used here are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used here, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in accordance with the actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific values should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0045] For a better understanding of the content of the present invention, some terms in the present invention are explained as follows:

[0046] Base glass: A glass obtained by uniformly mixing compounds containing the oxides, melting and casting at high temperature, or rolling or drawing, and then annealing, without undergoing nucleation crystallization heat treatment and ion exchange strengthening treatment.

[0047] Glass-ceramic: Also known as glass-ceramics, it is a type of solid composite material that contains both a glass phase and a crystal phase (microcrystalline phase, crystalline phase) prepared by subjecting the base glass to controlled crystallization heat treatment with a set target.

[0048] Nucleation: Making the nucleating substances in the base glass grow tiny crystal nuclei through heat treatment.

[0049] Crystallization: Growing a certain crystal on the basis of crystal nuclei through heat treatment of the base glass.

[0050] Crystal phase: The crystal phase is the microscopic structure of crystallization and is a general term for the parts composed of a large number of crystalline solid phases.

[0051] CT_LD: Tensile stress line density, which is the ratio of the integral of the tensile stress of the strengthened glass-ceramic measured by the SLP-2000 stress meter to the glass thickness. The unit is Mpa / mm. The glass-ceramic is placed in a salt bath for ion exchange to form a compressive stress layer (i.e., the strengthened layer). During the ion exchange process, a tensile stress layer is formed inside the glass. Specifically, during chemical strengthening, ions with a large radius in the salt bath are exchanged with ions with a small radius in the glass, thereby forming a compressive stress layer on the glass surface and a tensile stress layer inside the glass. Compared with the glass-ceramic before strengthening, the occurrence of ion exchange will cause a change in the composition of the compressive stress layer. Since the ion exchange depth is usually less than or equal to the thickness of the compressive stress layer, the composition of the tensile stress layer inside the glass will not change, that is, the composition of the tensile stress layer is the same as that of the glass-ceramic before strengthening. The tensile stress layer has an upper boundary at a certain interval from the upper surface of the strengthened glass-ceramic and a lower boundary at a certain interval from the lower surface of the strengthened glass. The curve plotted with the tensile stress magnitude at a certain point on the line segment that is perpendicular to both the upper boundary and the lower boundary within the tensile stress layer and whose upper and lower endpoints fall on the upper boundary and the lower boundary respectively as the Y-axis and the distance from the corresponding point to the upper boundary as the X-axis is denoted as the tensile stress curve. The ratio of the definite integral of the tensile stress curve described in the specification to the thickness of the strengthened glass-ceramic is denoted as the tensile stress line density, that is, the ratio of the sum of the tensile stresses of the strengthened glass-ceramic measured by the SLP-2000 stress meter to the glass thickness.

[0052] |CT_AV|: Absolute value of the average tensile stress, specifically referring to the absolute value of the average of all tensile stresses in the tensile stress layer, obtained by testing with the SLP-2000 stress meter. The unit is Mpa.

[0053] DOL_0: Depth of the compressive stress layer, or called the depth of the compressive stress layer, which refers to the distance from any surface of the glass-ceramic to the position where the compressive stress close to that surface is zero, obtained by testing with the SLP-2000 stress meter. The unit is um.

[0054] |CT_CV|: Absolute value of the maximum tensile stress at the center or the maximum tensile stress, specifically referring to the maximum value among all tensile stresses in the tensile stress layer, obtained by testing with the SLP-2000 stress meter. The unit is Mpa.

[0055] Surface compressive stress: Surface CS. After the glass-ceramic undergoes chemical strengthening, the alkali metal ions with a smaller radius on the surface are replaced by alkali metal ions with a larger radius. Due to the jamming effect of the alkali metal ions with a larger radius, compressive stress is generated on the glass surface, which is called surface compressive stress. Surface CS is obtained by testing with the SLP-2000 stress meter. The unit is Mpa.

[0056] CS_50: Compressive stress at a depth of 50μm measured from the glass surface. The unit is Mpa.

[0057] Transmittance TR: It is the ratio of the radiant energy that is projected and transmitted through an object to the total radiant energy projected onto the object during the process where the incident luminous flux enters from the illuminated surface or the incident surface of the medium and exits from the other side.

[0058] Refractive index λ: It is the ratio of the speed of light in a vacuum to the speed of light in this medium.

[0059] In the examples and comparative examples of the present invention, the transmittance of the glass-ceramic at a wavelength of 400 - 1000 nm or 550 nm is the average value of the transmittances measured at a wavelength of 400 - 1000 nm or 550 nm for multiple glass samples of the same batch. At least 5 samples are taken from each batch of glass-ceramics for testing.

[0060] Instrumentation and testing methods

[0061] Thickness of the glass: It is determined by testing with a micrometer. Before and after chemical strengthening, the change in the thickness of the glass-ceramic is very small and can be ignored.

[0062] Crystal content test: Use an X-ray diffractometer to test the glass-ceramic sample to obtain an XRD diffraction peak curve. Then import the test result file (RAW format) of the X-ray diffractometer (Shimadzu XRD-6000) into an X-ray diffraction data Rietveld refinement software (such as Gsas, Fullprof, Maud) for fitting and calculation, and the crystal content in the glass-ceramic sample can be obtained. The ratio of the area of the fitted crystal phase peak to the area of all the fitted peaks is the crystal content. The X-ray diffractometer used in the present invention is Shimadzu's XRD-6000. The diffraction angle range for testing is 2θ = 10 - 80°, the scanning speed is 10° / min, the working voltage is 40 KV, and the working current is 30 mA. The method for obtaining the average grain size is as follows: Use an X-ray diffractometer to test the glass-ceramic sample. For the result data obtained from the XRD test, use the Scherrer formula D = Kλ / (βcosθ), where λ is the X-ray wavelength, β is the full width at half maximum of the peak position, and K = 0.89, and the average grain size can be obtained.

[0063] Transmittance test: According to the standard of "GB / T 7962.12-2010 Test methods for colourless optical glass - Part 12: Spectral transmittance", use professional test instruments to test the transmittance of the glass-ceramic. The test instruments used in the present invention are Konica Minolta spectrophotometer CM 3600A and Shimadzu UV-visible spectrophotometer UV-2600 from Japan.

[0064] A glass-ceramic provided by the present invention comprises a major part of nepheline crystal phase (NaAlSiO4), microcline crystal phase and eucryptite crystal phase (LiAlSiO4); and a minor part of β-quartz solid solution, sodium silicate and zirconia. Among them, the proportion of the eucryptite crystal phase in the total crystal phase of the glass-ceramic is 0-30%, and the average grain size ≤ 25 nm; the average grain size of the glass-ceramic is 20 nm-55 nm, and the overall crystallinity is 35%-70%; in the residual glass phase other than crystals, the proportion of Na2O in the residual glass phase of the glass-ceramic is denoted as M, and the value of M is 0.00% ≤ M ≤ 10.00%; the proportion of Li2O in the residual glass phase of the glass-ceramic is denoted as N respectively, and the value of N is 3.0% ≤ N ≤ 15.0%.

[0065] In one implementation of the present invention, the crystallinity of the glass is 35.00%, 40.00%, 45.00%, 50.00%, 55.00%, 60.00%, 65.00%, 70.00% and any value within the range composed of any two of the above values, as long as the glass-ceramic with the required performance of the present invention can be obtained.

[0066] In one implementation of the present invention, the proportion of Na2O in the residual glass phase of the glass-ceramic is controlled to be between 0.50% and 10.00%, and it can be 0.50%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0% and any value within the range composed of any two of the above values, as long as the glass-ceramic with the required performance of the invention can be obtained.

[0067] The proportion of Li2O in the residual glass phase of the glass-ceramic is controlled to be between 5.0% and 13.50%, and it can be 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0%, 13.50%, and any value within the range composed of any two of the above values, as long as the glass-ceramic with the required performance of the invention can be obtained.

[0068] In the present invention, the proportion of eucryptite in the crystal phase and the average grain size of eucryptite are controlled within the above ranges, and a glass-ceramic with high optical performance can be obtained, meeting the optical performance requirements of consumer electronic products and in-vehicle display devices.

[0069] In an implementation of the present invention, the glass-ceramic contains the following oxides, in mole percentages: SiO2: 42.00 - 52.00%, Al2O3: 16.00 - 21.00%, Na2O: 12.00 - 21.00%, ZrO2: 1.00 - 3.50%, TiO2: 0.00 - 2.00%, P2O5: 1.00 - 5.00%, CaO: 0.00 - 2.00%, Li2O: 8.00 - 16.00%, K2O: 0.00 - 2.00%, SnO2: 0.20 - 1.00% and B2O3: 0 - 3.00%; and 60% ≤ (SiO2 + Al2O3) ≤ 72% or 0.75 ≤ (Na2O / Li2O) ≤ 2.50 or 24.0 ≤ (Na2O + Li2O + K2O) ≤ 28.50.

[0070] SiO2 and Al2O3 are the main network-forming oxides and intermediate oxides of the base glass and the glass-ceramic. Keeping the total molar percentage of the two within a reasonable range can effectively ensure a relatively large network structure inside the glass-ceramic. In the present invention, the total molar percentage of (SiO2 + Al2O3) is 60.0% - 72.0%, preferably 60.0% - 70.0%, and can be 60.0%, 61.0%, 62.0%, 63.0%, 64.0%, 65.0%, 66.0%, 67.0%, 68.0%, 69.0%, 70.0%, 71.0%, 72.0%, as well as any component within the range formed by any two of the above values.

[0071] The specific contents and functions of the two are different, among which:

[0072] As one of the main components of the network-forming oxides of the base glass and the glass-ceramic, SiO2 is an important component that forms the Si-O tetrahedrons in the main body and constructs the network structure. Based on the raw materials involved in the embodiments of the present invention, the molar percentage of SiO2 is 42.0 - 52.0%, preferably 42.0 - 50.0%, and can take values such as 42.0%, 43.0%, 44.0%, 45.0%, 46.0%, 47.0%, 48.0%, 49.0%, 50.0%, 51.0%, 52.0%, as well as any component within the range formed by any two of the above values.

[0073] Al2O3 is an intermediate oxide for glass formation and is also the main component of crystal forms such as nepheline (NaAlSiO4), carnegieite, and eucryptite (LiALSiO4). It can significantly improve the thermal stability of the base glass and glass-ceramics. 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 progress of ion exchange. Excessive Al2O3 will increase the viscosity of the glass and is not conducive to melting. Based on the raw materials involved in the embodiments of the present invention, the molar percentage of Al2O3 is 16.0 - 21.0%, preferably 16.0 - 20.0%. For example, it can take values such as 16.0%, 17.0%, 18.0%, 19.0%, 20.0%, 21.0% and any value within the composition range formed by any two of the above numbers.

[0074] The three alkali metal oxides of Na2O + Li2O + K2O are external network oxides of the base glass. When the total molar percentage of the three is controlled within a certain range, it can effectively ensure the degree of broken bridging oxygen bonds inside the base glass and break the original network structure of the base glass. When heat-treating the base glass, it can promote the crystallization of the base glass. In the present invention, the total molar percentage of (Na2O + Li2O + K2O) is 24.0% - 28.50%, which can be 24.0%, 25.0%, 26.0%, 27.0%, 28.0%, 28.50% and any component within the range formed by any two of the above values.

[0075] The functions and components among Na2O + Li2O + K2O are not the same. Among them,

[0076] Na2O is one of the main components of crystal forms such as nepheline (NaAlSiO4), carnegieite, and sodium silicate (Na2SiO4), and is also an important element in the subsequent chemical strengthening process. At the same time, Na2O is a flux during the high-temperature melting of the base glass and can significantly reduce the melting temperature of the base glass. However, when the content of Na2O is higher than 21 mol%, the chemical stability of the glass-ceramics is significantly reduced. Therefore, the ideal molar percentage of Na2O is 12.0% - 21.0%. At this time, not only can the melting temperature be maintained within a suitable range, but also the Na2O in the residual glass phase in the glass-ceramics can be controlled within a reasonable range, so that the external network oxides of the glass-ceramics can be kept within a reasonable range and the glass-ceramics can have good ion exchange characteristics. In the present invention, the molar percentage range of Na2O is 12.0 - 21.0%, preferably 12.0 - 20.0%, and specifically can be 12.0%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, 20.0%, 21.0% and any value within the range formed by any two of the above values.

[0077] 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 at the same time significantly reduce the crack incidence rate. Among them, adding a small amount of K2O can not only slow down the crystallization behavior that occurs during the forming of the glass-ceramics, but also promote the formation of nepheline, carnegieite or sodium silicate crystals during the crystallization process. When the molar content of K2O exceeds 2.0%, crystal phases such as potassium feldspar will be generated, which will harm its mechanical strength and optical properties. The range of the molar ratio content of K2O in the base glass involved in the embodiments of the present invention is 0.00 - 2.00%, preferably 0.0 - 1.50%. Specifically in the present invention, it can be 0.00%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0% and any value within the range composed of any two of the above values.

[0078] Li2O is an oxide with relatively 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. At the same time, Li + In the glass-ceramics provided by the present invention, it is not only a constituent element of spodumene (LiAlSiO4), but also can participate in the ion exchange chemical strengthening reaction to further enhance the mechanical properties of the glass-ceramics. By strictly controlling its content, the proportion of spodumene in the glass-ceramics described in the present invention can be effectively controlled. The range of the molar ratio content of Li2O involved in the embodiments of the present invention is 12.0 - 16.0%, preferably 12.0 - 15.0%. Specifically in the present invention, it can be 12.0%, 13.0%, 14.0%, 15.0%, 16.0% and any value within the range composed of any two of the above values.

[0079] P2O5 can be used as a nucleating agent in the base glass and glass-ceramics, which can promote the phase separation and overall crystallization ability of the base glass. If the concentration of P2O5 is too low, the base glass is not easy to crystallize, and crystals are only formed from the surface inward at a higher temperature and low viscosity; if the concentration of P2O5 is too high, it will be difficult to control devitrification when cooling during the formation of the base glass. In the embodiments of the present invention, the molar ratio content range of P2O5 is 1.00 - 5.00%, and the preferred range is:

[0080] 1.00% - 4.00%. Specifically, it can be 1.00%, 1.50%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 5.0% and any value within the range composed of any two of the above values.

[0081] ZrO2 is an intermediate oxide for glass formation, which can improve the chemical stability of glass, increase the hardness of glass, as well as the scratch and drop resistance of glass. At the same time, due to its high cation charge and strong field strength, ZrO2 has a large agglomeration effect on the glass structure and is commonly used as a nucleating agent in glass ceramics. However, excessive ZrO2 will greatly increase the viscosity of the glass and affect the forming ability of the glass. In the embodiments of the present invention, the molar proportion content range of ZrO2 is 1.0 - 3.50%, preferably 1.0 - 3.0%, specifically it can be 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, and any value within the range composed of any two of the above values.

[0082] TiO2 is one of the nucleating agents for crystal nucleation and growth in glass ceramics, which can effectively promote the growth of crystal nuclei during the nucleation and crystallization treatment of the base glass, and at the same time improve the stability of the glass; the introduction of TiO2 effectively promotes the precipitation of crystal nuclei during the nucleation process. At the same time, the introduction of TiO2 easily causes phase separation of the base glass, resulting in crystallization and affecting the formation of the glass. In the present invention, the content range of TiO2 is 0.00 - 2.00%, preferably 0.00 - 1.00%, specifically it can be 0.00%, 0.50%, 1.0%, 1.50%, 2.0%, and any value within the range composed of any two of the above values.

[0083] CaO, as a network modifier oxide for glass formation, helps to reduce the viscosity of the glass, inhibits glass crystallization during glass forming, and at the same time can improve the low-temperature fusibility of the glass. However, excessive CaO will reduce the devitrification resistance of the glass. By adding an appropriate amount of CaO, the effect of reducing the glass viscosity without affecting the crystallization performance of the glass can be achieved. For the raw materials involved in the embodiments of the present invention, the content range of CaO is 0.00 - 2.00%, preferably 0.00 - 1.00%, specifically it can be 0.00%, 0.5%, 1.0%, 1.5%, 2.0%, and any value within the range composed of any two of the above values.

[0084] B2O3, as a network modifier oxide of the glass, generally fills the voids in the silicon-oxygen tetrahedron framework, and its cation coordination rarely changes, and some properties of its oxide can be considered constant values. 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 glass ceramic. For the raw materials involved in the embodiments of the present invention, the content range of B2O3 is 0.00 - 3.00%, preferably 1.00 - 3.00%, specifically it can be 0.00%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and any value within the range composed of any two of the above values.

[0085] In an implementation of the present invention, the glass-ceramic composition further contains a clarifying agent with a molar ratio of 0.10 - 0.80%, which can effectively homogenize and clarify the base glass composition and eliminate the bubbles inside the glass. The clarifying agent is selected from one or more of NaCl, Sb2O3, As2O3, nitrates, and sulfates; the molar proportion of the clarifying agent component can be 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60%, 0.70%, 0.80%, and any value within the range composed of any two of the above values.

[0086] Based on the same inventive concept, the present invention also provides a method for preparing a glass-ceramic, including operation process flows such as the preparation of the base glass, the preparation of the glass-ceramic, and the preparation of the strengthened glass-ceramic.

[0087] Specifically as follows:

[0088] Preparation of the base glass: Ingredients corresponding to the oxides are proportioned and uniformly mixed according to the formula and melted in a platinum crucible at 1500 - 1600 °C for 4 hours, then poured into a forming mold for forming. After cooling to 900 °C, it is placed in an annealing furnace at 400 - 480 °C, preferably 450 - 580 °C, for annealing for 6 - 168 hours, preferably annealing for 6 - 120 hours, and then cooled to room temperature with the furnace, and the base glass can be obtained. The clarifying agent can be any one or more substances selected from NaCl, Sb2O3, As2O3, nitrates, sulfates, etc.

[0089] Preparation of the glass-ceramic: The base glass is subjected to the following nucleation treatment and crystallization treatment in sequence to obtain a transparent glass-ceramic tile. When performing the nucleation treatment, it is heated to the nucleation temperature at a heating rate of 1 - 10 °C / min, preferably 10 °C / min. The nucleation temperature is 510 - 590 °C, and the nucleation treatment time is 60 - 600 min. When performing the crystallization treatment, it is heated to the crystallization temperature at a heating rate of 1 - 10 °C / min, preferably 10 °C / min. The crystallization temperature is 620 - 700 °C, and the crystallization treatment time is 10 - 360 min. Here, the nucleation treatment time refers to the holding time after the crystallization furnace is heated to the set nucleation temperature at the set heating rate. Here, the crystallization treatment time refers to the holding time after the crystallization furnace is heated to the set crystallization temperature at the set heating rate.

[0090] Sample cold processing: The obtained glass-ceramic tiles are subjected to cold processing, which includes slicing. Before slicing, the glass-ceramic tiles can be shaped. After slicing, CNC processing, grinding, and polishing can be carried out in sequence, or at least one of CNC processing, grinding, and polishing can be selected for glass sheet modification treatment after slicing to obtain glass-ceramic samples of the desired size, such as polished sheets with dimensions of 50mm×50mm×0.7mm, 160mm×80mm×0.7mm, etc.

[0091] Chemical strengthening: The above-obtained glass-ceramic samples (i.e., polished sheets) are chemically strengthened in a pure sodium salt or lithium-sodium-potassium mixed salt bath at 380 - 560°C for 1 - 36 hours. The sodium ions in the salt bath are provided by any one or more of sodium nitrate, sodium sulfate, and sodium carbonate, the potassium ions are provided by any one of potassium nitrate, potassium sulfate, and potassium carbonate, and the lithium ions are provided by one or more of lithium nitrate, lithium sulfate, and lithium carbonate. In the present invention, a mixed salt composed of lithium nitrate, sodium nitrate, and potassium nitrate is preferably used for chemical strengthening treatment.

[0092] In some embodiments, the composition of the strengthening salt bath in the present invention is 0.1 - 100 wt% NaNO3 and 0 - 99.9 wt% KNO3, and LiNO3 with a content of 0 - 10 wt% is added relative to the total weight of the salt bath.

[0093] The following specifically illustrates the strengthened glass-ceramics and preparation methods of the present invention through specific examples. Taking Example 1 as an example, the specific preparation process is as follows:

[0094] Weigh various raw material powders according to the substrate glass composition ratio shown in Table 1, mix them with a mixer for 30 minutes, melt them in a platinum crucible at 1600°C for 4 hours, then pour them into a molding die for molding. After cooling to 900°C, put them into a 450°C annealing furnace for annealing for 8 hours, and then cool them to room temperature with the furnace (cooling to room temperature at a rate of about 5°C / min), thus obtaining substrate glass sample bricks; the preparation methods of the substrate glass in other examples are the same as that in Example 3. Among them, the formulation ingredient ratios of the substrate glass in Examples 1 - 5 and Comparative Examples 1 - 2 respectively correspond to the ingredient letters in Table 1, which are specifically described in Tables 2 and 3.

[0095] The base glass is placed in an annealing furnace for nucleation and crystallization treatment. The heating rate throughout the process is set at 10 °C / min, rising from room temperature to 545 °C. It is held at 545 °C for 4 hours for nucleation treatment; then heated to 675 °C and held at 675 °C for 90 min for crystallization treatment; afterwards, it is cooled to room temperature with the furnace to obtain glass-ceramic sample bricks. After the glass-ceramic sample bricks are shaped, sliced, CNC machined, flat ground, and polished, glass-ceramic sample pieces of the desired size are obtained, such as polished pieces with dimensions of 50 mm × 50 mm × 0.7 mm, 160 mm × 80 mm × 0.7 mm, etc. Weigh 700 g of NaNO3, 300 g of KNO3, and 0.3 g of LiNO3 (70 wt% NaNO3 + 30 wt% KNO3 + 0.03 wt% LiNO3, where 0.03% wt LiNO3 refers to the mass ratio of the additional LiNO3 added relative to the total mass of the mixed salt composed of NaNO3 and KNO3.) and place them in a crucible. Melt them into a liquid state in a strengthening furnace at a temperature of 480 °C. Place the obtained polished pieces into the molten salt bath and strengthen them at 480 °C for 7 hours for a single strengthening treatment to obtain strengthened glass-ceramic pieces. Perform performance tests on the obtained strengthened glass-ceramic pieces, and the results are shown in Table 3.

[0096] Table 2 shows the heat treatment and strengthening treatment of the glasses in Comparative Examples 1-5 and Examples 1-2 respectively. The heat treatment includes nucleation treatment and crystallization treatment. The specific conditions of the strengthening treatment include the mass ratio of the salt bath, the salt bath temperature, and the salt bath time. After different strengthening treatments are carried out on different strengthened glass-ceramic samples, various stress tests are performed, and the specific stress test data are summarized in Table 3.

[0097] Table 1: Formulation and crystal phase composition table of glass ceramics

[0098]

[0099]

[0100] Table 2: Preparation and strengthening process table of glass-ceramic samples

[0101]

[0102] Table 3: Performance table of glass-ceramic samples

[0103]

[0104] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A glass ceramic comprising a first crystal phase and a second crystal phase, characterized in that: The first crystal phase comprises: a sodium nepheline crystal phase, a triclinic nepheline crystal phase and a eucryptite crystal phase; The proportion of the eucryptite crystal phase to the total crystal phase of the glass ceramic is L, 0%<L≤30%; the average grain size of the eucryptite crystal phase is ≤25nm; The second crystalline phase is selected from one or more of β-quartz solid solution, sodium silicate and zirconium oxide; The average grain size of the glass ceramic is between 20nm and 55nm, and the overall crystallinity is between 35% and 70%; In the glass-ceramics, in the residual glass phase excluding the crystals, the proportion of Na2O in the residual glass phase in the glass-ceramics is recorded as M, and the value of M is 0.00%≤M≤10.00%; the proportion of Li2O in the residual glass phase in the glass-ceramics is recorded as N, and the value of N is 3.0%≤N≤15.0%.

2. The glass ceramic according to claim 1, characterized in that The glass ceramic contains the following percentages of oxides in terms of molar percentage of oxides: SiO2: 42.00~52.00%, Al2O3: 16.00~21.00%, Na2O: 12.00~21.00%, ZrO2: 1.00~3.50%, TiO2: 0.00~2.00%, P2O5: 1.00~5.00%, CaO: 0.00~2.00%, Li2O: 8.00~16.00%, K2O: 0.00~2.00%, SnO2: 0.20-1.00% and B2O3: 0-3.00%; The oxide components of the glass ceramic also satisfy one of the following relationships in terms of molar ratio: 60%≤(SiO2+Al2O3)≤72%; 0.75≤(Na2O / Li2O)≤2.50; 24.0≤(Na2O+Li2O+K2O)≤28.

50.

3. The glass ceramic according to claim 2, characterized in that: The glass ceramic further comprises 0.1-0.80% of a clarifier, wherein the clarifier is selected from one or more of NaCl, Sb2O3, As2O3, nitrates, and sulfates; the sum of the percentages of the components of the transparent glass ceramic containing the clarifier is 100%.

4. A method for preparing the glass ceramic according to claim 1, characterized in that: include: Calculated by mole percentage of oxides, weigh SiO2: 42.00-52.00%, Al2O3: 16.00-21.00%, Na2O: 12.00-21.00%, ZrO2: 1.00-3.50%, TiO2: 0.00-2.00%, P2O5: 1.00-5.00%, CaO: 0.00-2.00%, Li2O: 8.00-16.00%, K2O: 0.00-2.00%, SnO2: 0.20-1.00% and B2O3: 0-3.00%; The weighed oxides are mixed and melted at 1500-1600°C for 4-6 hours to obtain a molten liquid; The molten liquid is clarified and homogenized at 1350-1450° C., formed, and annealed to obtain a basic glass; The base glass is subjected to nucleation heat treatment and crystallization heat treatment to obtain the glass ceramic.

5. The method for preparing glass ceramics according to claim 4, characterized in that: The annealing temperature is 400-480°C, and the annealing holding time is 6-168 hours; the nucleation temperature of the nucleation heat treatment is 510-590°C, and the holding time is 60-600 minutes; the crystallization temperature of the crystallization heat treatment is 620-700°C, and the holding time is 10-360 minutes.

6. The method for preparing glass ceramics according to claim 5, characterized in that: The heating rate during the nucleation heat treatment and the crystallization heat treatment is 1-10° C. / min.

7. A reinforced glass ceramic, characterized in that: The reinforced glass ceramic is obtained by subjecting the glass ceramic described in any one of claims 1 to 3 to chemical strengthening treatment.

8. The reinforced glass ceramic according to claim 7, characterized in that: The chemical strengthening treatment comprises: placing the glass ceramic in a molten salt to perform ion exchange chemical strengthening to obtain a strengthened glass ceramic; The molten salt contains sodium ions or any two of sodium ions, lithium ions and potassium ions; The temperature of the molten salt is 380-560° C.; and the ion exchange time is 1-36 hours.

9. The reinforced glass ceramic according to claim 8, characterized in that: When the thickness of the reinforced glass ceramic is between 0.50nm and 1.00nm, DOL_0≥135um, CS_50≥145Mpa; |CT-AV|≥70Mpa, CT-CV≥100Mpa, CT-LD≥48000Mpa / mm, and the impact energy E of the monomer is ≥0.3 joule; The reinforced glass ceramic has a transmittance Tr of 89.00% or more within a wavelength range of 400-1000 nm, a haze of 0.15% or less, and a color index LAB value of 0.6 or less |B| or less than 1.

2.

10. A glass ceramic as described in any one of claims 1 to 3, or a reinforced glass ceramic as described in claim 7, or a glass ceramic prepared by the preparation method as described in any one of claims 4 to 6, used as a material for preparing screen protection covers of consumer electronic products and vehicle-mounted display devices.

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