Transparent glass ceramic, preparation method thereof and reinforced transparent glass ceramic

Abstract

The invention relates to the technical field of glass ceramics, and discloses a transparent glass ceramic, a preparation method thereof and a reinforced transparent glass ceramic. The crystal phase of the transparent glass ceramic is one or a composite crystal phase of more of sodium nepheline, triclinic nepheline, eucryptite, beta quartz solid solution and zirconium oxide; the overall crystallinity R of the transparent glass ceramic accounts for 20-70% of the total mass; when R is larger than or equal to 60%, the total crystal phase proportion M of the sodium nepheline and the triclinic nepheline and the crystal phase proportion N of the eucryptite meet the condition that M / N is larger than or equal to 0.75 and smaller than or equal to 4, and the average light transmittance T of the transparent glass ceramic in the visible light wave band of 400-700 nm is larger than or equal to 88%, the haze H is smaller than or equal to 0.18%, and B is smaller than or equal to 1.4. According to the invention, the variety of the crystal phase and the proportion of the overall crystallinity are controlled, so that the transparent glass ceramic has very high transmittance in a visible light wave band, and also has relatively good mechanical properties.

Description

Technical Field

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

[0002] As a new type of material, glass ceramics (NAS) with sodium as the main crystal form are gradually being widely used in protective cover plates for display devices. As a new type of display protection material, transparent glass ceramics need to achieve synergistic optimization of mechanical strength and optical properties at the micro-nano scale. Although the traditional sodium aluminum silicate (NAS) system can improve mechanical properties through crystallization strengthening, it is subject to the following problems:

[0003] The antagonistic relationship between sodium content and structural stability: In order to promote the formation of the main crystal phase of sodium nepheline, the traditional process needs to significantly increase the proportion of sodium oxide, but excessive sodium will destroy the continuity of the glass network structure and cause local charge distribution imbalance. This non-equilibrium state leads to non-uniform nucleation during crystallization, forming grain boundary defects and microcracks, which not only reduces the density of the material, but also may induce stress concentration problems.

[0004] The inverse correlation between the proportion of the crystalline phase and the transmittance: The existing technology obtains better mechanical properties by improving the crystallinity, but too high a crystallinity tends to increase the size of the crystals, resulting in a decrease in the transmittance in the visible light band (400-700nm). Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a transparent glass ceramic and a preparation method thereof, and a reinforced transparent glass ceramic, in order to solve the problem that the mechanical properties and transmittance of the existing transparent glass ceramic cannot be taken into account at the same time.

[0006] The above object of the present invention is achieved by the following technical scheme: a transparent glass ceramic, wherein the crystal phase of the transparent glass ceramic is one or more composite crystal phases of sodium nepheline, triclinic nepheline, eucryptite, β-quartz solid solution, and zirconia; the overall crystallinity R of the transparent glass ceramic accounts for 20%-70% of the total mass;

[0007] When R≥60%, the total crystal phase proportion M of the sodium pyroxene and the triclinic pyroxene and the crystal phase proportion N of the eucryptite satisfy 0.75≤M / N≤4, and the average transmittance T of the transparent glass-ceramic in the visible light band of 400-700nm is ≥88%, the haze H≤0.18%, and |B|≤1.4.

[0008] The following are preferred technical solutions of the present invention, but are not intended to 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.

[0009] As a preferred technical solution, for the transparent glass-ceramic, when R is 55%-60%, 1.5≤M / N≤5 is satisfied, the average light transmittance T of the transparent glass-ceramic in the visible light band of 400-700nm is ≥89%, the haze H≤0.15%, and |B|≤1.3.

[0010] As a preferred technical solution, for the transparent glass-ceramic, when R≤55%, the proportion of the eucryptite crystal phase N<20wt%, and at the same time the content of the β-quartz solid solution is 0-40wt%. The average light transmittance T of the transparent glass-ceramic in the visible light band of 400-700nm is ≥90%, the haze is optimized to H≤0.12%, and |B|≤1.2.

[0011] As a preferred technical solution, for the transparent glass-ceramic, the average grain size of the crystal phase of the transparent glass-ceramic is 15-60nm;

[0012] Preferably 20-50nm;

[0013] More preferably 20-40nm.

[0014] As a preferred technical solution, for the transparent glass-ceramic, the grain size distribution of the transparent ceramic glass satisfies that the proportion of the area with a grain size ≤55nm is ≥70%, and the ratio of the largest grain to the average grain size in the area with a grain size >55nm is ≤3.

[0015] As a preferred technical solution, for the transparent glass-ceramic, in terms of the molar percentage of oxides, the glass-ceramic contains the following percentages of oxides:

[0016] SiO2: 42.00-50.00%, 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: 5.00-16.00%, K2O: 0.00-2.00%, MgO: 0.00-3.00%, B2O3: 0-3.00% and clarifying agent: 0.1-1mol% of clarifying agent; wherein, 60%≤(SiO2+Al2O3)≤70%; 0.75≤(Na2O / Li2O)≤4; 24.0≤(Na2O+Li2O+K2O)≤28.50;

[0017] The clarifying agent is selected from one or more of SnO2, NaCl, Sb2O3, As2O3, nitrates, sulfates; the sum of the percentages of the components of the transparent glass-ceramic containing the clarifying agent is 100%.。

[0018] As a preferred technical solution, for the transparent glass-ceramic, the depth of the compressive stress layer DOL_0 of the transparent glass-ceramic is 100-165 μm, and the surface compressive stress CS is greater than 400 MPa.

[0019] Second, a preparation method of the above-mentioned transparent glass-ceramic, which includes:

[0020] Weigh the oxides constituting the transparent glass-ceramic according to the formula ratio, mix them and melt them at 1500-1580 °C to obtain a molten liquid;

[0021] Clarify and homogenize the molten liquid at 1350-1500 °C, shape it, and obtain the base glass after annealing;

[0022] Perform nucleation heat treatment and crystallization heat treatment on the base glass to obtain the transparent glass-ceramic;

[0023] The nucleation temperature of the nucleation heat treatment is 510-590 °C, the holding time is 60-600 min, the crystallization temperature of the crystallization heat treatment is 600-700 °C, the holding time is 10-360 min, and when performing the nucleation heat treatment and the crystallization heat treatment, the heating rate is 1-10 °C / min to raise the temperature to the nucleation and crystallization temperatures and hold the temperature.

[0024] Third, a strengthened transparent glass-ceramic, which is obtained by subjecting the above-mentioned transparent glass-ceramic to ion-exchange chemical strengthening treatment;

[0025] The temperature used for the ion-exchange chemical strengthening treatment is 380-560 °C; the molten salt used contains one or two of sodium ions, lithium ions and potassium ions.

[0026] Fourth, the above-mentioned transparent glass-ceramic or the transparent glass-ceramic prepared by using the above-mentioned preparation method is used as a material for preparing a cover plate of a display device.

[0027] Beneficial effects: Compared with the limitations in the traditional glass-ceramic technology where the type of crystal phase is single and the matching of crystallinity and grain size is insufficient, resulting in difficulties in synergistically improving the light transmittance and mechanical properties, the present invention realizes the synergistic improvement of optical and mechanical properties through the precise design of the crystal phase composite system and the coordinated regulation of multi-level crystallinity-grain size. Description of the Drawings

[0028] Figure 1 It is the transmittance diagram of Embodiment 1, 2, 4 and Comparative Example 1 of the present invention.

[0029] Figure 2 It is the XRD diagram of Embodiment 1 of the present invention Detailed implementation manners

[0030] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] 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 accompanying 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 of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary implementation manners of the present invention. As used herein, unless otherwise clearly specified in the context, 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 their combinations.

[0033] Unless otherwise specifically stated, the relative arrangements, numerical expressions and 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 according to 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, the technologies, methods and devices should be regarded as part of the authorized specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like 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.

[0034] A transparent glass-ceramic provided by the present invention, in terms of the molar percentage of oxides, contains the following percentages of oxides: SiO2: 42.00 - 50.00%, 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: 5.00 - 16.00%, K2O: 0.00 - 2.00%, MgO: 0.00 - 3.00%, B2O3: 0 - 3.00% and a clarifying agent: 0.1 - 1 mol% of a clarifying agent; wherein, 60% ≤ (SiO2 + Al2O3) ≤ 70%; 0.75 ≤ (Na2O / Li2O) ≤ 4; 24.0 ≤ (Na2O + Li2O + K2O) ≤ 28.50; the clarifying agent is selected from one or more of SnO2, NaCl, Sb2O3, As2O3, nitrates, sulfates; the sum of the percentages of the components of the transparent glass-ceramic containing the clarifying agent is 100%. And the crystal phase of the transparent glass-ceramic is one or more composite crystal phases of nepheline, carnegieite, eucryptite, β-quartz solid solution, zirconia; the overall crystallinity R of the transparent glass-ceramic accounts for 20% - 70% of the total mass; when R ≥ 60%, the total proportion M of the crystal phases of nepheline and carnegieite and the proportion N of the crystal phase of eucryptite satisfy 0.75 ≤ M / N ≤ 4, and the average light transmittance T of the transparent glass-ceramic in the visible light band of 400 - 700 nm is ≥ 88%, the haze H ≤ 0.18%, and |B| ≤ 1.4.

[0035] Further, when R is 55% - 60%, 1.5 ≤ M / N ≤ 5 is satisfied, the average light transmittance T of the transparent glass-ceramic in the visible light band of 400 - 700 nm is ≥ 89%, the haze H ≤ 0.15%, and |B| ≤ 1.3. When R ≤ 55%, the proportion N of the eucryptite crystal phase is < 20 wt%, and at the same time, the content of β-quartz solid solution is 0 - 40 wt%, the average light transmittance T of the transparent glass-ceramic in the visible light band of 400 - 700 nm is ≥ 90%, the haze is optimized to H ≤ 0.12%, and |B| ≤ 1.2. By controlling the eucryptite crystal phase and the content of β-quartz solid solution, the light transmittance of the transparent glass-ceramic in the visible light band can be effectively improved, and the haze can be reduced.

[0036] In the present invention, the components of Na2O and Li2O are controlled within a certain range, so that the proportion of Na2O and Li2O participating in ion exchange chemical strengthening in the residual glass phase of the glass-ceramic can be controlled within a certain range. This is greatly beneficial to the chemical strengthening ion exchange of the glass-ceramic, can significantly improve the mechanical properties of the chemically strengthened glass-ceramic, and at the same time control the average grain size, crystallinity and proportion of some crystal forms in the glass-ceramic, thereby ensuring the excellent optical properties of the glass-ceramic and fully meeting the mechanical and optical property requirements of the cover plate materials for consumer electronic devices and in-vehicle display devices.

[0037] In this embodiment, SiO2 and Al2O3 are the main network-forming oxides and intermediate oxides of the base glass and the glass-ceramic. Keeping the total molar proportion of the two within a certain range can effectively ensure a relatively large network structure inside the glass-ceramic. In the present invention, the total molar proportion of (SiO2 + Al2O3) is 58.0% - 71.0%, 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% and any one component within the range formed by any two of the above values.

[0038] Their specific contents and functions are different, among which:

[0039] As one of the main components of the network-forming oxide of the base glass and the glass-ceramic, SiO2 is one of the important components that form the Si-O tetrahedron in the main body and build the network structure. Based on the raw materials involved in the embodiments of the present invention, the molar proportion fraction of SiO2 is 42.0 - 50.0%, preferably 42.0 - 48.0%, and can take values such as 42.0%, 43.0%, 44.0%, 45.0%, 46.0%, 47.0%, 48.0%, 49.0%, 50.0% and any one component within the range formed by any two of the above values.

[0040] Al2O3 is an intermediate oxide for glass formation and also the main component of crystal forms such as nepheline, carnegieite, and eucryptite. 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 fraction of Al2O3 is 16.0 - 21.0%, preferably 16.0 - 19.0%. For example, it can take values of 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.

[0041] The three alkali metal oxides of Na2O + Li2O + K2O are network modifier oxides of the base glass. Controlling the total molar fraction of the three within a certain range 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 fraction of (Na2O + Li2O + K2O) is 24.0% - 28.50%, and it 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.

[0042] The functions and components among Na2O + Li2O + K2O are not all the same. Among them

[0043] Na2O is one of the main components of crystal forms such as nepheline and carnegieite, 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, which 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 fraction 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 network modifier oxides in the glass-ceramics are within a reasonable range, and the glass-ceramics have good ion exchange characteristics. In the present invention, the molar fraction range of Na2O is 12.0 - 21.0%, preferably 12.0 - 19.0%, 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 one or two of the above values.

[0044] 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 mass content of K2O exceeds 2.0 mol%, crystal phases such as potassium feldspar will be generated, which will harm its mechanical strength and optical properties. The molar ratio content range 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.

[0045] Li2O is an oxide with relatively high alkali metal activity and is an external glass network oxide. 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 petalite, 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 petalite in the glass-ceramics described in the present invention can be effectively controlled. The molar ratio content range of Li2O involved in the embodiments of the present invention is 5.0-16.0%, preferably 7.0-15.0 wt%. Specifically in the present invention, it can be 5.0%, 6.0 t%, 7.0 wt%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0 t%, 14.0 wt%, 15.0%, 16.0% and any value within the range composed of any two of the above values.

[0046] 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 lower viscosity; if the concentration of P2O5 is too high, it will be difficult to control and easy to devitrify when cooling during the formation of the base glass. In the embodiments of the present invention, the molar proportion content range of P2O5 is 1.00-5.00%, and the preferred range is: 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.

[0047] 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.

[0048] TiO2 is one of the nucleating agents for crystal nucleation and growth in glass ceramics, which can effectively promote the nucleation growth of the base glass during the nucleation and crystallization process, 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.

[0049] 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%. In the present invention, 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.

[0050] B2O3, as a network modifier oxide of the glass, generally fills the voids in the silicon-oxygen tetrahedron framework. 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%. In the present invention, 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.

[0051] In the content of the base glass composition involved in the present invention, there is also a clarifying agent with a mass ratio of 0.10 - 1.0%, which can effectively homogenize and clarify the base glass composition and simultaneously eliminate the bubbles inside the glass. The clarifying agent is selected from one or more of SnO2, NaCl, Sb2O3, As2O3, nitrates, and sulfates; the mass proportion of the clarifying agent component can be 0.10wt%, 0.20wt%, 0.30wt%, 0.40wt%, 0.50wt%, 0.60wt%, 0.70wt%, 0.80wt%, 0.90wt%, 1.0wt%, and any value within the range composed of any two of the above values.

[0052] In the glass ceramics and chemically strengthened glass ceramics involved in the present invention, the total content of the three crystal phases of nepheline, natrolite, and eucryptite accounts for more than 20wt% and less than 70wt% of the strengthened glass ceramics, preferably greater than or equal to 30wt% and less than or equal to 70wt%; more preferably greater than or equal to 40wt% and less than or equal to 70wt%. And there may be secondary crystal phases, such as zirconia, β - quartz solid solution, etc.

[0053] Natrolite is a cubic crystal, and nepheline is metastable and can be regarded as half of the network Si in SiO2 4+ being replaced by Al 3+ , Na + . At the same time, due to the large ionic radius and electric charge field strength of Na + , at high temperature, the higher content of Na + preferentially combines with Al + , Si 3+ , and O 4+ to form natrolite crystals. However, due to certain heat treatment conditions, Li 2- will inevitably also participate in the formation of a small amount of eucryptite crystal form, but the formation of too much eucryptite in the main crystal phase will affect the overall optical properties of the glass ceramics. Therefore, most of the Li + remains in the glass phase of the natrolite glass ceramics of the present invention, which can replace the Li + in the glass ceramics with Na + in the molten salt, further enhancing the mechanical properties of the glass ceramics; +

[0054] In some embodiments, in the strengthened glass ceramics of the present invention, the total content of the three crystal phases of nepheline, natrolite, and eucryptite is 20wt% - 70wt%. That is, the crystallinity is 20% - 70%, and the preferred crystallinity is 40% - 70%.

[0055] In some embodiments, in the strengthened glass-ceramics of the present invention, the crystallinity is 20.00%, 25.00%, 30.00%, 35.00%, 40.00%, 45.00%, 50.00%, 55.00%, 60.00%, 65.00%, 70.00%, and any value within the range formed by any two of the above values.

[0056] In some embodiments, since it is possible that nepheline may unavoidably appear, but the proportion of nepheline in the entire crystal phase needs to be controlled between 0% and 10%, which can be 1.0%, 2.00%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, 9.0%, 10%, and any value within the range formed by any two of the above values. The average grain size of the crystal phase of the transparent glass-ceramics is 15 - 60 nm, preferably 20 - 50 nm, and more preferably 20 - 40 nm.

[0057] In some embodiments, in the glass-ceramics of the present invention, the average size of the average grains is between 15 nm and 60 nm, preferably 25 nm - 50 nm, and more preferably 30 nm - 40 nm. In some embodiments, the average size of the grains can be 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm. And any value within the range formed by any two of the above values.

[0058] The strengthened glass-ceramics related to the present invention is a glass-ceramics obtained after chemical strengthening with obvious surface compressive stress and tensile stress layers, and it has the following stress characteristics:

[0059] When the glass thickness is between 0.50 mm and 1.00 mm: DOL_0 ≥ 100 um, CS ≥ 400 Mpa.

[0060] In some embodiments, when chemically strengthening the glass-ceramics of the present invention, the molten salt used is a nitrate containing one or a mixture of two ions of Na + , Li + , K + .

[0061] Term Explanation:

[0062] Base glass: A glass that is obtained by uniformly mixing compounds containing the said oxides, melting at high temperature by casting or rolling or drawing, and annealing, and has not been subjected to nucleation crystallization heat treatment and ion exchange strengthening treatment.

[0063] Glass-ceramics, also known as glass ceramics, are a type of solid composite material that contains both a glass phase and a crystal phase (microcrystalline phase, crystalline phase) prepared by subjecting a base glass to controlled crystallization heat treatment with a set goal.

[0064] Nucleation: The base glass is heat-treated to grow tiny crystal nuclei from the nucleating substances in the glass.

[0065] Crystallization: The base glass is heat-treated to grow a certain crystal on the basis of the crystal nuclei.

[0066] Crystal phase: The crystal phase is the microscopic structure of crystallization, which is a general term for the parts composed of a large number of crystalline solid phases.

[0067] DOL_0: The depth of the compressive stress layer, or the depth of the compressive stress layer, refers to the distance from any surface of the glass-ceramics to the position where the compressive stress close to the surface is zero, which is obtained by testing with an SLP-2000 stress meter. The unit is um.

[0068] Surface compressive stress: Surface CS. After the glass-ceramics are chemically strengthened, 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 an SLP-2000 stress meter, and the unit is MPa.

[0069] Transmittance TR: During the process of the incident light flux from the irradiated surface or the incident surface of the medium to the other side and leaving, the ratio of the radiant energy that is projected and transmitted through the object to the total radiant energy projected onto the object.

[0070] In the examples and comparative examples of the present invention, the transmittance of the glass-ceramics 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 of glass-ceramics are taken for testing in each batch.

[0071] Instrumentation and testing methods

[0072] Thickness of the glass: Determined by testing with a micrometer. Before and after chemical strengthening, the thickness change of the glass-ceramics is very small and can be ignored.

[0073] Crystal content test: Use an X-ray diffractometer to test the glass-ceramic sample to obtain the XRD diffraction peak curve. Then import the test result file (RAW format) of the X-ray diffractometer (Shimadzu XRD-6000) into the 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 the test is 2θ = 10-80°, the scanning speed is 10 0 / min, the working voltage is 40 KV, and the working current is 30 mA.

[0074] Method for obtaining the average grain size: 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.

[0075] Transmittance test: According to the standard of "GB / T 7962.12-2010 Test Methods for Colorless Optical Glass - Part 12: Spectral Transmittance", use a professional test instrument to test the transmittance of the glass-ceramic. The test instrument used in the present invention is the Konica Minolta spectrophotometer CM-3600D made in Japan.

[0076] Haze: The haze of glass refers to the percentage of the transmitted light intensity deviated from the incident light by more than 2.5° angle in the total transmitted light intensity, which is an important parameter for the optical transparency of transparent or semi-transparent materials. The greater the haze, the more the film gloss, transparency, especially the imaging degree decreases. The test instrument used in the present invention is the spectrophotometer CM-3600D.

[0077] LAB value: LAB is a color model based on physiological characteristics, where L represents brightness, A includes colors from dark green to gray to bright pink, and B includes colors from bright blue to gray to yellow. The B value in LAB can represent the deviation of an object between yellow and blue. The test instrument used in the present invention is the spectrophotometer CM-3600D.

[0078] Test of surface compressive stress (surface CS), DOL_0: Use the stress meter SLP-2000 of Luceo (Orihara) in Japan for testing. The light source wavelength is 518 nm, SOC = 25.5 (nm / cm) / MPa, refractive index = 1.54, exposure time: 300 μsec.

[0079] When testing the test surfaces CS and DOL_0, it is necessary to drop the special refractive liquid on the stress meter, then wipe the strengthened glass ceramic product clean, place it on the test path, and test its value. The refractive index of the refractive liquid used in SLP-2000 is 1.51.

[0080] Test by differential scanning calorimetry (DSC): After grinding the sample into powder, pass it through a 200-mesh sieve; the test conditions are: room temperature to 1000 °C, heating rate of 10 °C / min; the test instrument is Mettler Toledo TGA / DSC 3+ Thermogravimetric and synchronous thermal analyzer

[0081] The following will specifically illustrate the strengthened glass ceramic and its preparation method of the present invention through specific embodiments. Taking Embodiment 1 as an example, its specific preparation process is as follows:

[0082] Embodiment 1:

[0083] S1, configure the glass ceramic precursor mixture;

[0084] Weigh various raw material powders according to the substrate glass composition ratio shown in Table 1, and mix them with a mixer for 30 minutes;

[0085] S2, high-temperature melting of the base glass;

[0086] Pour the mixture obtained in S1 into a platinum crucible, the melting temperature is 1560 °C, keep it warm for 5 hours, fully melt and clarify at 1450 °C, then pour it into a forming mold for forming. After cooling to 700 °C, put it into an annealing furnace at 450 °C for annealing for 8 hours, and then cool it to room temperature with the furnace (cool to room temperature at a rate of about 5 °C / min), and the substrate glass sample brick can be obtained;

[0087] S3: Heat treatment process;

[0088] According to the DSC curve of the base glass, formulate a heat treatment process for nucleation and crystallization treatment. Heat the base glass to the nucleation temperature (510 °C) at a certain heating rate and keep it warm at the nucleation temperature for 4 h to obtain the nucleated base glass; then heat it to the crystallization temperature of 673 °C at a certain rate and keep it warm at the crystallization temperature of 673 °C for 25 min to obtain the crystallized glass; among them, the heating rate is preferably 2 °C / min.

[0089] S4: Shaping and slicing;

[0090] After the glass ceramic sample brick is shaped, sliced, CNC processed, surface ground, and polished, glass ceramic sample pieces of the desired size are obtained, such as glass pieces the size of a mobile phone cover with length, width and thickness of 50 mm × 50 mm × 0.7 mm, 160 mm × 80 mm × 0.7 mm, etc.;

[0091] S5: Chemical strengthening;

[0092] Weigh 100% NaNO3 and put it into a crucible. Melt it into a liquid state in a strengthening furnace at a temperature of 450 °C. After preheating the obtained polished wafer, immerse it into the molten salt bath and strengthen it at 450 °C for 12 hours for a first strengthening treatment. Then weigh 100% KNO3, put it into a crucible, and melt it into a liquid state in a strengthening furnace at a temperature of 395 °C. After preheating the obtained polished wafer, immerse it into the molten salt bath and strengthen it at 395 °C for 2 hours for a second strengthening treatment. Take out the glass after the second strengthening, wash it, and obtain the chemically strengthened glass-ceramic cover glass wafer. The properties of the obtained glass-ceramic wafer are summarized in Table 3.

[0093] Example 2

[0094] Prepare according to the composition ratio corresponding to Example 2 in Table 1. The preparation method of the substrate glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to the description of Example 2 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The properties of the obtained glass-ceramic wafer are summarized in Table 3.

[0095] Example 3

[0096] Prepare according to the composition ratio corresponding to Example 3 in Table 1. The preparation method of the substrate glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to the description of Example 3 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The properties of the obtained glass-ceramic wafer are summarized in Table 3.

[0097] Example 4

[0098] Prepare according to the composition ratio corresponding to Example 4 in Table 1. The preparation method of the substrate glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to the description of Example 4 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The properties of the obtained glass-ceramic wafer are summarized in Table 3.

[0099] Example 5

[0100] Prepare according to the composition ratio corresponding to Example 5 in Table 1. The preparation method of the substrate glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to the description of Example 5 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The properties of the obtained glass-ceramic wafer are summarized in Table 3.

[0101] Example 6

[0102] Prepare according to the composition ratio corresponding to Example 6 in Table 1. The preparation method of the substrate glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to the description of Example 6 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The properties of the obtained glass-ceramic wafer are summarized in Table 3.

[0103] Example 7

[0104] Prepare according to the components corresponding to Example 7 in Table 1. The preparation method of the base glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to those in Example 7 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The performance of the obtained glass-ceramic sheets is summarized in Table 3.

[0105] Comparative Example 1

[0106] Prepare according to the components corresponding to Comparative Example 1 in Table 1. The preparation method of the base glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to those in Comparative Example 1 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The performance of the obtained glass-ceramic sheets is summarized in Table 3.

[0107] Comparative Example 2

[0108] Prepare according to the components corresponding to Comparative Example 2 in Table 1. The preparation method of the base glass is the same as that in Example 1, and the melting and chemical strengthening process parameters correspond to those in Comparative Example 2 in Table 2. Those not specifically mentioned in the table are the same as those in Example 1. The performance of the obtained glass-ceramic sheets is summarized in Table 3.

[0109] Table 1: Formulation Composition Table of Glass-Ceramics

[0110]

[0111]

[0112] Table 2: Melting and Chemical Strengthening Process Table of Glass-Ceramic Samples

[0113]

[0114]

[0115] Table 3: Performance Table of Glass-Ceramic Samples

[0116]

[0117] 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 transparent glass ceramic, characterized in that, The crystal phase of the transparent glass-ceramic is one or more composite crystal phases of nepheline, carnegieite, eucryptite, β-quartz solid solution, and zirconia; the overall crystallinity R of the transparent glass-ceramic accounts for 20%-70% of the total mass; When R≥60%, the total proportion M of the crystal phases of nepheline and carnegieite and the proportion N of the crystal phase of eucryptite satisfy 0.75≤M / N≤4, and the average light transmittance T of the transparent glass-ceramic in the visible light band of 400-700nm is ≥88%, the haze H≤0.18%, and |B|≤1.

4.

2. The transparent glass ceramic according to claim 1, wherein When R is 55%-60%, 1.5≤M / N≤5 is satisfied, and the average light transmittance T of the transparent glass-ceramic in the visible light band of 400-700nm is ≥89%, the haze H≤0.15%, and |B|≤1.

3.

3. The transparent glass ceramic according to claim 1, characterized in that, When R≤55%, the proportion N of the eucryptite crystal phase is <20wt%, and at the same time the content of β-quartz solid solution is 0-40wt%. The average light transmittance T of the transparent glass-ceramic in the visible light band of 400-700nm is ≥90%, the haze is optimized to H≤0.12%, and |B|≤1.

2.

4. The transparent glass ceramic according to claim 1, wherein The average grain size of the crystal phase of the transparent glass-ceramic is 15-60nm; Preferably 20-50nm; More preferably 20-40nm.

5. The transparent glass ceramic according to claim 4, wherein The grain size distribution of the transparent glass-ceramic satisfies that the proportion of the area with a grain size ≤55nm is ≥70%, and the ratio of the largest grain to the average grain size in the area with a grain size >55nm is ≤3.

6. The transparent glass ceramic according to any one of claims 1-5, characterized in that, In terms of the molar percentage of oxides, the glass-ceramic contains the following percentages of oxides: SiO2: 42.00-50.00%, 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: 5.00-16.00%, K2O: 0.00-2.00%, MgO: 0.00-3.00%, B2O3: 0-3.00% and a clarifying agent: 0.1-1mol% of a clarifying agent; among them, 60%≤(SiO2+Al2O3)≤70%; 0.75≤(Na2O / Li2O)≤4; 24.0≤(Na2O+Li2O+K2O)≤28.50; The clarifying agent is selected from one or more of SnO2, NaCl, Sb2O3, As2O3, nitrates, and sulfates; the sum of the percentages of the components of the transparent glass-ceramic containing the clarifying agent is 100%.

7. The transparent glass ceramic according to claim 6, characterized in that, The depth of the compressive stress layer DOL of the transparent glass-ceramic is 100-165μm, and the surface compressive stress CS is greater than 400MPa.

8. A method for preparing the transparent glass ceramic according to claim 1, characterized in that, Including: Weigh the oxides constituting the transparent glass-ceramic according to the formula ratio, mix them and melt them at 1500-1580°C to obtain a molten liquid; Clarify and homogenize the molten liquid at 1350-1500°C, form it, and obtain a base glass after annealing; The base glass is subjected to nucleation heat treatment and crystallization heat treatment to obtain the transparent glass-ceramic; 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 600-700 °C, and the holding time is 10-360 min. When performing the nucleation heat treatment and the crystallization heat treatment, the temperature is increased to the nucleation and crystallization temperatures at a heating rate of 1-10 °C / min and held.

9. A strengthened transparent glass ceramic, characterized in that, The strengthened transparent glass-ceramic is obtained by ion-exchange chemical strengthening treatment of the transparent glass-ceramic according to any one of claims 1-7; The temperature used for the ion-exchange chemical strengthening treatment is 380-560 °C; the molten salt used contains one or two of sodium ions, lithium ions and potassium ions.

10. A transparent glass-ceramic according to any one of claims 1-7 or a transparent glass-ceramic prepared by the preparation method according to claim 8, which is used as a material for preparing a cover plate of a display device.

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