Low warpage tempered glass ceramics, preparation method and use thereof

Abstract

The present invention provides a strengthened crystallized glass having low warpage, its preparation method and use. The strengthened crystallized glass has a compressive stress layer extending from the surface to the inside of the glass, and the glass surface compressive stress CS is less than 550MPa. The stress distribution of the compressive stress layer is as follows: (a) when the depth of the stress layer is 0 μm≦Dol<30 μm, the stress distribution curve shows a substantially linear distribution, and the absolute value |k1| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 2.45<|k1|<5.05; (b) when the depth of the stress layer is 30 μm≦Dol≦Dol_zero, the stress distribution curve shows a substantially linear distribution, and the absolute value |k2| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 1≦|k2|≦1.5. The strengthened crystallized glass according to the present disclosure employs the above-mentioned stress distribution, and can significantly improve warpage caused by excessive difference in stress gradient after strengthening.

Description

[Technical field]

[0001] The present disclosure is in the field of glass-ceramics, and in particular, relates to strengthened glass-ceramics with low warpage, their preparation methods and uses.

[0002] CROSS REFERENCE TO RELATED APPLICATIONS This disclosure claims priority to a Chinese application bearing application number CN202111110119.0 and entitled "Low warpage tempered crystallized glass, its preparation method and use," filed with the China State Intellectual Property Office on September 18, 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] With the rapid development of smart industry, especially the advent of the 5G era, the role of glass materials in the field of portable electronic devices is becoming increasingly important. As the wavelength of the electromagnetic waves used in 5G communication and even the next 6G communication becomes shorter, the requirements for materials used in communication devices will become higher and higher, and the scope of glass use in communication devices will become wider and wider. Taking mobile phones as an example, it took less than five years for glass to be used in both front and back covers, rather than just in front covers. It is conceivable that mobile phones with all-glass cases will appear within the next five years.

[0004] Glass is inherently a brittle material with poor ductility, so when used as a structural material for mobile phones, the requirement for dimensional accuracy is very high, and after the glass undergoes two processes of three-dimensional hot bending and chemical strengthening, significant shrinkage and warping occurs. Currently, NAS Glass and LAS Glass, which are mainstream in the electronic glass field, adopt a method of making the CS of the surface high and the Dol of the inside large in order to improve the impact resistance of the strengthened glass. The stress distribution is usually as follows:

[0005] (1) The relatively thin K-stress layer on the outermost layer is K + / Na +The distribution range is Dol_K=0-15μm and CS_K=850-900MPa. In the range Dol_15μm-Dol_zero from the outer surface along the thickness direction, the maximum compressive stress value CS_Na max is generally 350MPa-550MPa, and changes sharply at the inflection point. Referring to FIG. 1, as can be seen from the stress curve distribution, the surface layer of the tempered glass is more than twice as high as the CS of the inner layer.

[0006] (2)Na + / K + The gradient |k| of the compressive stress curve formed by the ion exchange of Na is very large, which means that the stress difference between the corresponding stresses of adjacent unit thicknesses within the depth range of the layer is very large. When a large amount of glass is chemically strengthened in the same glass strengthening furnace, the convection speed of the melt varies depending on the position, especially between the outer position and the more central position of the basket due to the distance between the large amount of glass sheets. Therefore, the Na concentration on two opposing surfaces of the same glass sheet is very large. + / K + The CS of the exchange layer has a difference of about 0 to 50 MPa, and the stress difference causes the glass to warp in order to reach a mechanically balanced state. If the glass is a 2.5D or 3D curved surface, the deformation amount becomes even larger, which directly affects the dimensional stability of the product. For example, in the case of 2.5D glass, the warp amount is generally 150 μm to 600 μm after tempering in a CG factory at present, and sometimes reaches 1200 μm, which is far from the industry requirement of less than 200 μm.

[0007] In the prior art, a glass ceramic product with improved stress distribution has been disclosed, which has an inflection point at a certain depth in the stress distribution, and the slope of the compressive stress curve |k| is very large from the surface of the glass to the depth of the inflection point. As shown in FIG. 2, + / Na + The compressive stress formed by the exchange of Na + / Li +The difference between the compressive stress formed by the exchange of the carbide and the compressive stress formed by the exchange of the carbide was relatively large. Therefore, the product is also prone to warping after chemical strengthening. Summary of the Invention

[0008] The present disclosure provides a strengthened crystallized glass with low warpage. The crystallized glass has a compressive stress layer extending from the surface to the inside of the glass, and the glass surface compressive stress CS is less than 550 MPa. The stress distribution of the compressive stress layer is such that (a) when the depth of the stress layer is 0 μm≦Dol<30 μm, the stress distribution curve shows a substantially linear distribution, and the absolute value |k1| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 2.45<|k1|<5.05, and (b) when the depth of the stress layer is 30 μm≦Dol≦Dol_zero, the stress distribution curve shows a substantially linear distribution, and the absolute value |k2| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 1≦|k2|≦1.5.

[0009] Optionally, the glass surface compressive stress, Cs, is less than 350 MPa.

[0010] Optionally, said |k1| satisfies 2.45<|k1|<4.35.

[0011] Optionally, the |k1| satisfies 2.60<|k1|<3.75.

[0012] Optionally, the |k2| satisfies 1.00<|k2|<1.35.

[0013] Optionally, the compressive stress layer has a layer depth Dol_zero of 110 μm to 142 μm, and a stress CS_50 of 60 MPa to 130 MPa when the layer depth is 50 μm.

[0014] Optionally, the composition (wt%) of the crystallized glass is 58.1-78.8% SiO2, 5.4-24.1% Al2O3, 0-15% MgO+ZnO, 0-3.3% B2O3, 0-1.9% P2O5, 0-3.5% ZrO2, 1.6-13.7% Li2O, 0.5-4.5% Na2O, 3.1% or less K2O, 8% or less Y2O3, the remainder being unavoidable impurities, Na2O / R2O being 0.6 or less, R2O / Al2O3 being 5.25 or less, and R2O being the sum of alkali metal oxides.

[0015] Optionally, the crystalline phase of the glass-ceramics comprises one or more of lithium disilicate, petalite, β-quartz solid solution, and spinel, and has a crystallinity of 70-98%.

[0016] Optionally, the crystallinity of the crystallized glass is 80-95%.

[0017] Optionally, the crystallinity of the crystallized glass is 87-95%.

[0018] Optionally, the strengthened crystallized glass has a warpage of 180 μm or less.

[0019] Optionally, the strengthened crystallized glass has a warpage of 150 μm or less.

[0020] Optionally, the strengthened crystallized glass has a warpage of 120 μm or less.

[0021] The present disclosure further provides a method for preparing the above-mentioned strengthened crystallized glass, which includes step 1 of subjecting a base glass to a crystallization treatment to obtain a base crystallized glass, and step 2 of subjecting the base crystallized glass obtained by the crystallization treatment to ion exchange.

[0022] Optionally, the ion exchange in step 2 includes two ion exchanges, where the first ion exchange is performed by immersing the basic crystallized glass in a first molten salt bath, the first ion exchange being performed at a temperature of 430°C to 450°C, and the first ion exchange being performed for 6 hours to 11 hours; and the second ion exchange is performed by immersing the basic crystallized glass after the first ion exchange in a second molten salt bath, the second molten salt bath being composed of at least two types of molten salts, KNO3 and LiNO3, the second ion exchange being performed at a temperature of 420°C to 440°C, and the second ion exchange being performed for 60 minutes or less.

[0023] Optionally, in the second molten salt bath, the content of KNO3 is 90 wt% or more and the content of LiNO3 is 0. <LiNO3≦0.15wt%である。

[0024] Optionally, the crystallization treatment in step 1 includes a step of placing the base glass in a box-type crystallization furnace and performing a three-stage heat treatment, in which in the first stage, the temperature is increased to 520°C to 580°C and kept at that temperature for 200 to 300 minutes, in the second stage, the temperature is increased to 600°C to 640°C and kept at that temperature for 100 to 150 minutes, in the third stage, the temperature is increased to 645°C to 740°C and kept at that temperature for 180 to 270 minutes, and then cooled to obtain a base crystallized glass.

[0025] The present disclosure further provides a use of the above-mentioned reinforced crystallized glass, which is used as a mobile phone cover, a tablet cover, a watch cover, or an automobile display cover. [Brief description of the drawings]

[0026] In order to more clearly describe the technical solutions of the embodiments of the present disclosure, the following briefly describes the prior art and the drawings used in the embodiments of the present disclosure. The drawings described are only for illustrating some embodiments of the present disclosure, and are not intended to limit the scope. Those skilled in the art can obtain other related drawings based on these drawings without using inventive abilities. [Figure 1] 1 is a graph showing a mainstream stress distribution curve according to the prior art. [Diagram 2] 1 is a graph showing a stress distribution curve according to a prior art. [Diagram 3] 2 is a graph showing a stress curve of the crystallized glass according to Example 1. [Figure 4] 1 is an XRD pattern of the crystallized glass prepared in Example 1. [Diagram 5] 1 is an XRD pattern of the crystallized glass prepared in Example 7. [Figure 6] 1 is a graph showing a stress curve of the crystallized glass prepared in Example 15. [Figure 7] 1 is an XRD pattern of the crystallized glass according to Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure are described below clearly and completely. In the embodiments, the specific conditions are not specified, but the conventional conditions or the conditions recommended by the manufacturer can be used. For reagents or equipment whose manufacturers are not specified, conventional products available on the market can be used.

[0028] The present disclosure aims to solve the problem of warping during tempering. Currently, all conventional methods for solving warping are of the "first leave the problem unresolved, then take measures" type, for example, one-sided polishing to repair the deformation, which can repair the deformation to a certain extent, but the strength of the tempered glass is partially lost by polishing. The present disclosure can fundamentally solve the problem of warping after tempering from the perspective of the internal structure and composition of glass.

[0029] In order to overcome the above-mentioned shortcomings of the prior art, the present disclosure aims to provide a tempered crystallized glass with low warpage, its preparation method and use, which has a low CS on the surface of the prepared crystallized glass, a compressive stress layer extending from the surface to the inside, a small and relatively uniform difference in compressive stress gradient, and can significantly improve the warpage caused by the excessive difference in stress gradient after tempering. The CT integral of the tempered glass according to the present disclosure is comparable to that of general tempered glass, and, as a result of adding the effect of increasing strength due to crystallization, the overall drop resistance is superior to that of general tempered glass.

[0030] The following describes low-warpage tempered crystallized glass, its preparation method and use according to embodiments of the present disclosure.

[0031] The low warpage tempered crystallized glass according to some embodiments of the present disclosure has a warpage of 180 μm or less, optionally 150 μm or less, optionally 120 μm or less. In some embodiments, the crystallized glass has a compressive stress layer extending from the surface to the inside of the glass, and the glass surface compressive stress CS is less than 550 MPa. Optionally, the compressive stress CS is 100 MPa to 540 MPa, 130 MPa to 500 MPa, 150 MPa to 400 MPa, or 200 MPa to 300 MPa, such as 500 MPa, 450 MPa, 400 MPa, 350 MPa, 320 MPa, 300 MPa, 280 MPa, 250 MPa, 180 MPa, or 140 MPa, or any value within the range or a range defined by any value. Optionally, the glass surface compressive stress CS is less than 350 MPa, and optionally CS is less than 200 MPa, and the compressive stress layer has the following stress distribution:

[0032] (a) When the depth of the stress layer is 0 μm≦Dol<30 μm, the stress distribution curve exhibits an approximately linear distribution, and the absolute value |k1| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 2.45<|k1|<5.05, or may be any value within that range or a range defined by any value. Optionally, |k1| satisfies 2.45<|k1|<4.35, optionally, |k1| satisfies 2.60<|k1|<3.75, and optionally, |k1| satisfies 2.60<|k1|<3.2.

[0033] (b) When the depth of the stress layer is 30 μm≦Dol≦Dol_zero, the stress distribution curve exhibits a substantially linear distribution, and the absolute value |k2| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 1≦|k2|≦1.5, or may be any value within that range or a range defined by any value. Optionally, |k2| satisfies 1.00<|k2|<1.35, and optionally, |k2| satisfies 1.00<|k2|≦1.33.

[0034] In some embodiments, the depth of layer Dol_zero of the compressive stress layer is 110 μm to 142 μm. Optionally, Dol_zero is 115 μm to 140 μm, 120 μm to 135 μm, or 125 μm to 130 μm, such as 120 μm, 125 μm, 128 μm, 130 μm, 135 μm, 138 μm, or 140 μm, or any value therein or a range defined by any value. In some embodiments, the stress CS_30 is 65 MPa to 455 MPa when the depth of layer is 30 μm. Optionally, CS_30 is 80MPa to 420MPa, 100MPa to 380MPa, 150MPa to 320MPa, or 200MPa to 250MPa, such as 70MPa, 75MPa, 80MPa, 85MPa, 90MPa, 95MPa, 100MPa, 105MPa, 110MPa, 115MPa, 120MPa, 125MPa, 130MPa, 135MPa, 140MPa, 150MPa, 155MPa, 160MPa, 170MPa, 180MPa, 185MPa, 190MPa, 200MPa, 220MPa, 240MPa, 250MPa, 270MPa, 300MPa, 350MPa, 370MPa, 420MPa, or 440MPa, or any value within that range or a range defined by any value. Optionally, CS_30 is 100MPa to 300MPa. In some embodiments, the stress CS_50 is between 60 MPa and 130 MPa at a layer depth of 50 μm. Optionally, CS_50 is between 70 MPa and 120 MPa, or between 80 MPa and 110 MPa, or between 90 MPa and 100 MPa, such as 65 MPa, 70 MPa, 75 MPa, 80 MPa, 85 MPa, 90 MPa, 95 MPa, 100 MPa, 105 MPa, 110 MPa, 115 MPa, 120 MPa, or 125 MPa, or any value therein or a range defined by any value. Optionally, CS_50 is between 80 MPa and 110 MPa.

[0035] The strengthened crystallized glass according to the present disclosure has a compressive stress layer extending from the surface to the interior of the glass, has low surface compressive stress, has no significant stress inflection points, and has a layer depth Dol_zero of 110 μm to 142 μm. By controlling the surface compressive stress, the depth of the stress layer, and the slope of the stress curve for the two layer depth segments of 0 to 30 μm and 30 μm to Dol_zero, warping deformation of the glass caused by a relatively large stress difference between the surface and the interior can be suppressed.

[0036] In some embodiments, the composition (wt%) of the crystallized glass is 58.1 to 78.8% SiO2 (e.g., 60 to 75%, 62 to 70%, or 64 to 68%, e.g., 58.4%, 59%, 59.5%, 59.8%, 60%, 60.3%, 60.5%, 61%, 61.4%, 62%, 62.5%, 62.6%, 63%, 63.5%, 64%, 64.5%, 65%, 65.5%, 66%, 67.4%, 68%, 68.5%, 69%, 69.5%, 70%, 70.5%, 70.8%, 71%, 71.5%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, 107%, 108%, 109%, 109, 109, 108, 109, 109, 101, 102, 103, 104, 105, 106, 107, 108, 109 ... 5%, 75.5%, 76%, 77% or 78%, or any value within that range or a range defined by any value), and Al2O3 is 5.4-24.1% (e.g., 6-24%, 8-20% or 10-18%, e.g., 5.5%, 5.8%, 6%, 6.5%, 7%, 8%, 8.5%, 9%, 10%, 11%, 11.5%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22% or 23%, or any value within that range or a range defined by any value). MgO+ZnO is 0-15% (e.g. 1-14%, 4-12% or 6-10%, e.g. 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13% or 14%, or any value within that range or a range defined by any value), and B2O3 is 0-3.3% (e.g. 0.1-3.0%, 0.5-2.5% or 1.0-2.0%, e.g. 0.5%, 0.8%, 1%, 1.5%, 1.8%, 2%, 2.5%, 2.7% or 3.1%, etc. or may be any value within that range or a range defined by any value), P2O5 is 0-1.9% (e.g., 0.1-1.8%, 0.4-1.5% or 0.8-1.2%, such as 0.3%, 0.5%, 0.6%, 0.8%, 1.1%, 1.2%, 1.5% or 1.7%), and ZrO2 is 0-3.5% (e.g., 0.1-3.0%, 0.5-2.5% or 1.0-2.0%, such as 0.8%, 1%, 1.8%, 2.0%, 2.3%, 2.5%, 2.7%, 2.9%, 3.2%, or 3.4%, or any value therein or range defined by any value), Li2O is 1.6-13.7% (e.g., 2-13%, 4-10%, or 6-8%, e.g., 1.8%, 2%, 2.4%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or 13%, or any value therein or range defined by any value), Na2O is 1.6-4.5% (e.g., 2.0-4.0%) , 2.5-3.5% or 2.8-3.2%, e.g., 2%, 2.5%, 3%, 3.5%, 4% or 4.4%, or any value within that range or a range defined by any value), K2O is 3.1% or less (e.g., 0.1-3.0%, 0.4-2.8%, or 1.0-2.5%, e.g., 0.5%, 1%, 1.5%, 2%, 2.5% or 2.8%, or any value within that range or a range defined by any value), Y2O3 is 0-8 %, (e.g., 0.5-7.5%, 2.5-6.5%, or 3.5-5.5%, e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 7.5%, or any value within that range or a range defined by any value), with the balance being unavoidable impurities, and Na2O / R2O being 0.6 or less (e.g., 0.05-0.58, 0.15-0.55, or 0.25-0.45, e.g., 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or 0.55 or any value within that range or a range defined by any value), R2O / Al2O3 is 5.25 or less (e.g., 0.05-5.2, 0.1-5.0, 0.5-4.5, 1.0-4.0 or 2.0-3.0, e.g., 0.05, 0.1, 0.5, 0.8, 1.2, 1.3, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, or any value within that range or a range defined by any value), and R2O is the sum of alkali metal oxides.

[0037] Without being bound by theory, SiO2 is the main component that constitutes the network structure of crystallized glass and forms the crystal phase, and exhibits a silicon-oxygen tetrahedral structure in glass, and has good chemical stability, thermal stability and mechanical strength. In the present disclosure, the amount of SiO2 added is 58.1-78.8%, optionally 60-69%, or optionally 61-67%.

[0038] Without being bound by theory, Al2O3 can constitute the network structure of the glass according to the present disclosure, can greatly improve the chemical stability and elastic modulus of the glass, and can reduce the tendency of the glass to devitrify. When Al is present in the glass as an [AlO4] structure, it exists as part of the network structure and can form a network structure together with [SiO4] to make the glass structure more dense. Since the molar volume of [AlO4] is larger than the molar volume of [SiO4], ions can move more easily in the glass during ion exchange, which is more favorable for ion exchange. When Al is present in the glass as an [AlO6] structure, it is liberated outside the network structure and can enrich the network structure in the form of a network filler, thereby increasing the density and Vickers hardness of the glass network structure and strengthening the network structure. In the present disclosure, the amount of Al2O3 added is 5.4 to 24.1%, optionally 5.6 to 18%, and optionally 5.6 to 7.8%.

[0039] Without being bound by theory, MgO and ZnO, as optional components, have the effect of lowering the difficulty of glass melting and improving the thermal stability of glass, and can also be used as a crystal nucleating agent by taking advantage of their tendency to phase separate. In the present disclosure, the amount of MgO+ZnO added is 0-15%, and optionally, the total amount of MgO and ZnO added is 14% or less, the amount of MgO added is optionally 8.5% or less, and the amount of ZnO added is optionally 10.5% or less.

[0040] Without being bound by theory, B2O3, as a network-forming oxide, has the effect of improving the melting characteristics of glass, and an appropriate amount of B2O3 also has the effect of improving the strength and chemical durability of crystallized glass. In the present disclosure, the amount of B2O3 added is 0 to 3.3%, and optionally 1.5 to 3%.

[0041] Without being bound by theory, P2O5 is added as a crystal nucleating agent in the present disclosure in an amount of 1.9% or less, optionally 1.5% or less, or not added at all.

[0042] Without being bound by theory, ZrO2 has the effect of improving the stability of the glass and also has the effect of refining crystal grains during crystallization to control the size of the crystal grains. In the present disclosure, the amount added is 3.5% or less, and optionally 2.5% or less.

[0043] Without being bound by theory, alkali metal oxides such as Li2O, Na2O, and K2O are used as network modifiers, and have the effect of supplying oxygen, significantly lowering the melting temperature of glass, and adjusting the temperature dependency of glass viscosity. Li2O and Na2O are the main components of ion exchange, and the amount of addition thereof affects the depth of the ion exchange layer, the surface stress, and the stress distribution of the compressive stress layer of the crystallized glass product to some extent. Li2O also has the effect of promoting the formation of crystals, and is an essential component of the crystal phase. In the present disclosure, the amount of Li2O added is 1.6 to 13.7%, optionally 2.5 to 12.5%, and optionally 5.8 to 12.0%. The amount of Na2O added is 0.5 to 4.5%, optionally 1.6 to 4.1%, and optionally 1.7 to 3.0%. The amount of K2O added is 3.1% or less, optionally 1.7% or less, optionally 1.5% or less, or not added.

[0044] Without being bound by theory, Y2O3 has the effect of strengthening the network structure strength of the crystallized glass and increasing the Young's modulus. By adding a certain amount of Y2O3, it is possible to make the stress distribution uniform, suppress the occurrence of warping, and ensure the drop strength and deformation stability of the product. In the present disclosure, the amount of Y2O3 added is 0-8%, optionally 0.5-4%, optionally 2-4%.

[0045] By controlling the ratio of Na2O / R2O and the ratio of R2O / Al2O3, the stress distribution in the compressive stress layer can be effectively uniformed and the warpage of the glass can be suppressed. In the present disclosure, Na2O / R2O is 0.6 or less, optionally 0.35 or less, optionally 0.25 or less. R2O / Al2O3 is 5.25 or less, and if it is larger than this value, on the one hand, the glass network channel structure is small due to the Al content being too low, and the ion transport efficiency inside the network channel is greatly reduced, and on the other hand, it affects the control of the type of crystal phase, which is detrimental to the dimensional stability and optical performance of the glass. Optionally, R2O / Al2O3 is 2.8 or less, optionally R2O / Al2O3 is 2 or less, optionally R2O / Al2O3 is 1.2 or less, and optionally R2O / Al2O3 is 0.8 or less.

[0046] In some embodiments, the crystalline glass includes one or more of lithium disilicate, petalite, β-quartz solid solution, and spinel, and has a crystallinity of 70% to 98%, such as 85% to 96%, 88% to 95%, or 90% to 93%, such as 70%, 74%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any value therein or range defined by any value. In theory, the higher the crystallinity, the less likely warpage due to strengthening stress will occur. The reason is that under conditions of less than 500°C, the crystals do not participate in ion exchange, and the deformation is mainly due to the imbalance of stress on the two main surfaces after the residual glass phase is strengthened, which means that the glass must balance the forces (pressure P = F / S) by changing the area, i.e., it deforms. The higher the crystallinity, the less the residual glass phase, and since it is mainly the glass phase that can participate in chemical ion exchange, the less the glass phase, the more limited the toughening effect by chemical strengthening. For this reason, a balance must be achieved between strength and dimensional stability, that is, a balance is achieved in terms of the ratio of the crystal phase to the glass phase. It is most preferable that the glass phase is 5% to 10%. The crystallinity is optionally 80% to 95%, and optionally 90% to 95%. Regarding the selection of the crystal phase, since there is a transition from the lithium silicate crystal phase to the lithium disilicate crystal phase during the crystallization process, it is necessary to control the proportion of the residual lithium silicate crystal phase in the finished product and make the proportion of the residual lithium silicate crystal phase 5% or less; if there is an excess of the lithium silicate crystal phase, it will greatly reduce the optical properties of the product, causing the product to have a bluish tinge.

[0047] Some embodiments of the present disclosure further provide a method for preparing a strengthened glass-ceramic. The preparation of a base glass is carried out by melting and forming the base glass in a manner well known in the art. The formed base glass is crystallized and strengthened according to the following steps:

[0048] Step 1: The base glass is subjected to a crystallization process to obtain a base crystallized glass.

[0049] Step 2: Ion exchange is performed on the basic glass-ceramics obtained by the crystallization treatment.

[0050] In some embodiments, the crystallization treatment in step 1 includes the following steps: The base glass is placed in a box-type crystallization furnace and subjected to a three-stage heat treatment. In the first stage, the temperature is raised to 520°C to 580°C (e.g., 530°C, 540°C, 550°C, 560°C, or 570°C, etc.) and kept at that temperature for 200 min to 300 min (e.g., 220 min to 280 min, 230 min to 260 min, or 240 min to 250 min, e.g., 210 min, 220 min, 230 min, 240 min, 250 min, 260 min, 270 min, 280 min, or 290 min, etc., or any value within that range or a range defined by any value). In the second stage, the temperature is raised to 600 to 640°C (for example, 605°C to 635°C, 610°C to 630°C, or 615°C to 625°C, for example, 600°C, 610°C, 620°C, 630°C, 635°C, 650°C, or 660°C, or any value within that range or a range defined by any value), and the temperature is maintained for 100 min to 150 min (for example, 105 min to 145 min, 110 min to 140 min, or 120 min to 130 min, for example, 110 min, 115 min, 120 min, 125 min, 130 min, 135 min, 140 min, or 145 min, or any value within that range or a range defined by any value). In the third stage, the temperature is raised to 645°C to 740°C (for example, 645°C, 650°C, 660°C, 690°C, 740°C, etc., or any value within that range or a range defined by any value), and the temperature is maintained for 180min to 270min (for example, 190min to 260min, 200min to 250min, or 210min to 240min, for example, 190min, 200min, 210min, 220min, 230min, 240min, 250min, or 260min, etc., or any value within that range or a range defined by any value).Then, the mixture is cooled to obtain a basic crystallized glass.

[0051] Without being bound by theory, the present disclosure discloses that the above three-stage heat treatment process can effectively control the crystallization degree of glass, ensure the strength of the crystallized glass, and suppress warpage caused by strengthening stress. On the other hand, by setting the crystallization time of the high-temperature stage of 645°C or more to 180 minutes or more, the glass crystal phase can be effectively controlled, the proportion of residual lithium silicate crystal phase in the glass product can be reduced, and discoloration of the product can be prevented.

[0052] In some embodiments, the ion exchange in step 2 comprises two ion exchanges.

[0053] First ion exchange: The basic crystallized glass is immersed in a first molten salt bath to perform a first ion exchange. The first molten salt bath contains at least 75 wt% NaNO3 (e.g., 75 wt% to 100 wt%, 80 wt% to 95 wt%, or 85 wt% to 90 wt%, e.g., 77 wt%, 80 wt%, 82 wt%, 85 wt%, 88 wt%, 90 wt%, 95 wt%, 97 wt%, or 100 wt%, or any value within that range or a range defined by any value), and the temperature of the first ion exchange is 430°C to 450°C (e.g., 434°C to 448°C, 438°C to 445°C, or 440°C to 445°C). 2°C, for example, 432°C, 435°C, 440°C, 442°C, 445°C, or 448°C, or any value within that range or a range defined by any value), and the time for the first ion exchange is 6 to 11 hours (for example, 6.5h to 10.5h, 7.5h to 9.5h, or 8.0h to 9.0h, for example, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, or 10.5h, or any value within that range or a range defined by any value).

[0054] Second ion exchange: The base crystallized glass that has undergone the first ion exchange is immersed in a second molten salt bath for the second ion exchange. The second molten salt bath contains at least two kinds of molten salts, KNO3 and LiNO3. The temperature of the second ion exchange is 420°C to 440°C (for example, 424°C to 438°C, 426°C to 435°C, or 428°C to 432°C, for example, 424°C, 426°C, 428°C, 430°C, 432°C, 435°C, or 438°C, etc., or it can be any value within the range or a range defined by any value), and the time of the second ion exchange is 60 minutes or less (for example, 1 to 60 minutes, 5 to 50 minutes, or 10 to 40 minutes, for example, 3 minutes, 5 minutes, 8 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, or 45 minutes, etc., or it can be any value within the range or a range defined by any value).

[0055] In some embodiments, in the second molten salt bath, the content of KNO3 is 90 wt% or more (for example, 90 wt% to 99.99 wt%, 92 wt% to 98 wt%, or 98 wt% to 99.98 wt%, for example, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.2 wt%, 99.5 wt%, 99.7 wt%, 99.8 wt%, 99.9 wt%, 99.92 wt%, 99.95 wt%, 99.98 wt%, or 99.99 wt%, etc., or it can be any value within the range or a range defined by any value), and the content of LiNO3 is 0 < LiNO3 ≤ 0.15 wt% (for example, 0.01 wt% to 0.15 wt%, 0.04 wt% to 0.12 wt%, or 0.06 wt% to 0.10 wt%, for example, 0.02 wt%, 0.04 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.12 wt%, 0.13 wt%, or 0.14 wt%, etc., or it can be any value within the range or a range defined by any value).

[0056] Although not bound by theory, after treating the base glass by a crystallization process, the present disclosure obtained a strengthened crystallization glass having the required stress distribution characteristics by two ion exchanges. In the first ion exchange (IOX1), the first molten salt bath contains at least 75% NaNO3, the exchange temperature is 430 - 450 °C, and a long exchange time of 6 - 11 h is adopted. In this way, the maximum tensile stress line density (CT_LD, = Σ0 CT_CV CT / Dol_zero) is formed in the first ion exchange, and the maximization of glass strength can be realized. Optionally, the first molten salt bath does not contain potassium salt, or even if it contains potassium salt, its content is 25 wt% or less. Due to the potassium salt contained in the molten salt bath, a large amount of K + adheres to the surface of the glass in IOX1, and since the radius of K + is much larger than that of Na + , Li + , it greatly hinders the exchange between Na and Li and high strength cannot be achieved. In the second ion exchange (IOX2), the second molten salt bath has a KNO3 content of 90 wt% or more and also contains a small amount of LiNO3 (0 < LiNO3 ≤ 0.15 wt%). Li + has a small radius and high reaction activity, so the exchange rate with Na + on the glass surface is at least three times or more the rate of K + / Na + exchange. Therefore, the small amount of Li + present in the IOX2 salt bath can significantly suppress the balanced progress of the exchange reaction between K + in the salt bath and Na + on the glass surface, thereby preventing the enrichment of K + on the glass surface and the K + in the thickness direction of the glassThe concentration of molten salt is reduced, the difference in surface compressive stress between the inner and outer layers of the glass is reduced, and the change in slope of the resulting stress curve is smoother and more natural, with no significant point of abrupt change in slope (inflection point). The ion exchange time is short, 60 minutes or less. By controlling the molten salt and the exchange time as described above, it is possible to effectively prevent excessive compressive stress on the surface of the strengthened crystallized glass and excessive stress difference within the unit thickness distance range, and suppress the warping of the glass caused thereby. In addition, the difference in the compressive stress gradient of the obtained strengthened crystallized glass is small and relatively uniform. Compared with the conventional mainstream NAS Glass and LAS Glass, the strengthened crystallized glass according to the present disclosure has the following characteristics: when the depth of the stress layer is 0 μm≦Dol<30 μm, the absolute value |k1| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 2.45<|k1|<5.05; when the depth of the stress layer is 30 μm≦Dol≦Dol_zero, the absolute value |k2| of the slope of the stress curve between any two points on the curve that are 20 μm apart satisfies 1≦|k2|≦1.5; when the depth of the stress layer is 0 to 30 μm, the slope is relatively small, the area of ​​the approximate "trapezoid" formed by the stress curve, the Y axis representing stress, and the X axis representing depth is larger, the corresponding CT integral is not inferior to that of general strengthened glass, and the drop resistance is superior to that of general strengthened glass overall.

[0057] The performance indexes of the crystallized glass products according to the embodiments, examples, and comparative examples of the present disclosure were measured by the following methods. Measurements were performed using an SLP2000 type stress meter (light source: 518 nm) manufactured by Orihara Manufacturing Co., Ltd., Japan. The type of crystal phase and the degree of crystallinity were measured by powdering the sample and using XRD (model number: Shimadzu XRD-6100). Some terms in the present disclosure are interpreted as follows.

[0058] CS: surface compressive stress, unit: MPa.

[0059] CS_30: CS value corresponding to the point where Dol = 30 μm on the stress curve.

[0060] CS_50: CS value corresponding to the point where Dol = 50 μm on the stress curve.

[0061] Dol_zero: The CS value corresponding to the point where CS = 0 MPa on the stress curve, which is usually the maximum Dol value that can be measured by FSM6000LE or SLP2000.

[0062] Slope K: The slope of the line consisting of any two specified points on the stress curve.

[0063] Warpage: The glass sheet is placed horizontally on a standard marble platform (with a flatness of less than 0.01 mm), and the maximum height difference between any point on the same plane and the center point on the glass sheet.

[0064] Sandpaper drop height B20 value: the drop height value when 20% of samples fail in a drop test of a sample set consisting of several samples. B20 value is a commonly used reference value for portable electronic terminal manufacturers to evaluate the reliability of device products. Some embodiments of the present disclosure further provide the use of reinforced crystallized glass. The reinforced crystallized glass can be used as a mobile phone cover, a tablet cover, a watch cover, and an automobile display cover.

[0065] The surface CS of the strengthened crystallized glass according to the present disclosure is low, the compressive stress layer extends from the surface to a certain depth, the difference in the compressive stress gradient is small and relatively uniform, and the warpage caused by the excessive difference in the stress gradient after strengthening can be significantly improved. The warpage of the prepared crystallized glass is 0.2 mm or less. And the crystallized glass according to the present disclosure has a CT integral comparable to that of general strengthened glass, and as a result of adding the effect of strength increase by crystallization, the overall drop resistance is superior to that of general strengthened glass. The sandpaper drop height B20 value of the prepared crystallized glass satisfies B20≧1.3 m. The strengthened crystallized glass according to the present disclosure has excellent warpage resistance and can be widely applied in the field of 3C electronic products.

[0066] Working Example

[0067] In order to more clearly interpret and explain the technical solution of the present disclosure, the following non-limiting examples are provided. Although the examples of the present disclosure ensure the accuracy of the numerical values ​​as much as possible, there are some errors and deviations. The composition itself is shown in weight percent based on the oxide and is calculated as 100%, and the thickness of each sample in each example is 0.65 mm.

[0068] The performance indexes of the crystallized glass products according to the following Examples and Comparative Examples were measured by the methods according to the specific embodiments described above.

[0069] [Table 1] JPEG0007598479000002.jpg228166JPEG0007598479000003.jpg183166

[0070] [Table 2] JPEG0007598479000005.jpg204166JPEG0007598479000006.jpg226166JPEG0007598479000007.jpg108166

[0071] Note: The sandpaper drop method used a load of 176 g, and the sandpaper was 180 mesh SiC sandpaper. A fixed-direction drop test was performed from a height of 40 cm. The sample was dropped once from one height, and the height was increased by 10 cm at a time. The height at which the sample broke was recorded.

[0072] Performance results explanation

[0073] Figure 3 is a graph showing the stress curve of the crystallized glass prepared by Example 1. As can be seen from the figure, the crystallized glass has a low CS on the surface, the compressive stress extends from the surface to the inside, and the difference in the compressive stress gradient is small and relatively uniform. Figure 4 is the XRD pattern of the crystallized glass prepared by Example 1, and the main crystal is spinel. Regarding the performance results, the prepared glass has good warpage resistance (warpage amount ≦ 0.1mm) and excellent drop resistance (B20 is 1.5m).

[0074] 5 is an XRD pattern of the crystallized glass prepared according to Example 7. As can be seen from the figure, the main crystals are β-quartz solid solution and lithium disilicate.

[0075] Figure 6 is the graph showing the stress curve of the crystallized glass prepared by Example 15. As can be seen from the figure, the crystallized glass has low surface CS, small difference in compressive stress gradient and relatively uniform. Regarding performance results, the prepared glass has good warpage resistance (warpage amount ≦ 0.13mm) and relatively good drop resistance (B20 is 1.3m).

[0076] As can be seen from comparing Examples 1 to 16 with Comparative Examples 1 to 4, the glasses according to Examples 1 to 16 have low surface CS, and each stress curve has an approximately linear distribution. In the stress curves of the two-segment layer depths of 0 to 30 μm and 30 to Dol_zero, the slope |k1| satisfies 2.4≦|k1|≦5.05, the slope |k2| satisfies 1.0≦|k2|≦1.5, the difference in the compressive stress gradient is small and relatively uniform, and the data on the effect of the prepared crystallized glass shows that the warpage meets the application needs of 0.2 mm or less, and the sandpaper drop height B20 value meets B20≧1.3 m. As can be seen from Comparative Examples 1 to 4, the stress distribution characteristic of Comparative Example 1 is that the slope |k2| is relatively large (1.7 to 3.0) in the stress curve at a layer depth of 30 to Dol_zero, and the data on the effect of the prepared crystallized glass shows that the warpage is 0.15 mm or less, which is relatively excellent in this respect, but the performance is relatively poor in the sandpaper drop height B20 value. The stress distribution characteristic of Comparative Example 2 is that the slope |k1| is very large (12.8 to 19.0) in the stress curve at a layer depth of 0 to 30 μm, and the data on the effect of the prepared crystallized glass shows that the warpage is 0.18 to 0.45 mm, and the sandpaper drop height B20 is 0.93 m, which is quite poor in performance. The stress distribution characteristic of the comparative example 3 is that in the stress curve with a stress layer depth Dol_zero of 157 μm, the slope |k1| is relatively large (5.2 to 6.8), and |k2| is relatively small (0.6 to 1.1). Accordingly, the data on the effect of the prepared crystallized glass shows that the drop resistance is relatively poor (B20 was 0.92 m) and the warpage resistance is relatively poor (warpage amount was 0.3 to 0.6 mm). The stress distribution characteristic of the comparative example 4 is that the stress layer depth Dol_zero is relatively large (162 μm), and accordingly, the data on the effect of the prepared crystallized glass shows that the warpage resistance is relatively poor (0.22 to 0.38 μm) and the drop resistance is relatively poor (B20 was 0.88 m).

[0077] In addition, as can be seen by comparing Example 11 and Example 14, when the preparation process (including the crystallization process and the ion exchange process) is the same, it is advantageous to obtain glass with low warpage by making the ratio of R2O / Al2O3 relatively small in the composition of the crystallized glass, and it is possible to obtain glass with better performance (i.e., lower warpage).

[0078] As can be seen by comparing Example 12 and Example 13, when the glass composition and crystallization process are the same, in the ion exchange process, when the salt bath of IOX1 does not contain potassium salt, it is advantageous to obtain a high-strength glass, and a glass with better performance (i.e., higher strength) can be obtained.

[0079] As can be seen by comparing Examples 11-13, 15 with Comparative Examples 1, 3-4, when the glass composition is the same, the temperature of the third stage of the crystallization process in Examples 11-13, 15 is within the temperature range of the present disclosure, so that the presence of lithium silicate in the crystallized glass crystallized phase can be avoided, and the excellent optical properties of the product can be further guaranteed. The temperature of the third stage of the crystallization process in Comparative Examples 1, 3-4 is too low, so that lithium silicate is present in the crystallized glass crystallized phase, which significantly deteriorates the optical properties of the product. Figure 7 is the XRD pattern of the crystallized glass according to Comparative Example 1. As can be seen from the figure, the crystals include lithium silicate, lithium disilicate, and petalite.

[0080] The above are merely embodiments of the present disclosure, and do not limit the scope of the present disclosure. Any equivalent replacement of the structure or equivalent replacement of the process made by using the specification and drawings of the present disclosure, or direct or indirect use in other related fields, also falls within the protection scope of the present disclosure.

Claims

1. The glass has a compressive stress layer extending from the surface to the inside of the glass, and the glass surface compressive stress CS is less than 550 MPa, and the stress distribution of the compressive stress layer is (a) When the depth of the stress layer is 0 μm≦Dol<30 μm, the absolute value |k1| of the slope of the stress curve between any two points on the stress distribution curve that are 20 μm apart satisfies 2.45<|k1|<5.05; (b) When the depth of the stress layer is 30 μm≦Dol≦Dol_zero, the absolute value |k2| of the slope of the stress curve between any two points on the stress distribution curve that are 20 μm apart satisfies 1≦|k2|≦1.

5. The strengthened crystallized glass is characterized by the above-mentioned.

2. The glass surface compressive stress CS is less than 350 MPa.

2. The strengthened glass-ceramics according to claim 1.

3. The |k1| satisfies 2.45<|k1|<4.35, Optionally, |k1| satisfies 2.60<|k1|<3.

75.

2. The strengthened glass-ceramics according to claim 1.

4. The |k2| satisfies 1.00<|k2|<1.

35.

2. The strengthened glass-ceramics according to claim 1.

5. The layer depth Dol_zero of the compressive stress layer is 110 μm to 142 μm, and when the layer depth is 50 μm, the stress CS_50 is 60 MPa to 130 MPa.

2. The strengthened glass-ceramics according to claim 1.

6. The composition (wt%) of the crystallized glass is SiO ２ is 58.1 to 78.8%, and Al ２ O ３ is 5.4 to 24.1%, MgO + ZnO is 0 to 15%, and B ２ O ３ is 0 to 3.3%, and P ２ O ５ is 0 to 1.9%, and ZrO ２ is 0 to 3.5%, and Li ２ O is 1.6 to 13.7%, Na ２ O is 1.6 to 4.5%, and K ２ O is 3.1% or less, and Y ２ O ３ is 8% or less, the balance being unavoidable impurities, ２ O / R ２ O is 0.6 or less, and R ２ O / Al ２ O ３ is 5.25 or less, and R ２ O is the sum of alkali metal oxides 2. The strengthened glass-ceramics according to claim 1.

7. The crystal phase of the crystallized glass includes one or more of lithium disilicate, petalite, β-quartz solid solution, and spinel, and has a crystallinity of 70 to 98%.

7. The strengthened glass-ceramics according to claim 6.

8. The crystallinity of the crystallized glass is 80 to 95%.

8. The strengthened glass-ceramics according to claim 7.

9. The crystallinity of the crystallized glass is 87 to 95%.

8. The strengthened glass-ceramics according to claim 7.

10. The strengthened crystallized glass has a warpage of 180 μm or less, optionally has a warpage of 150 μm or less, and optionally has a warpage of 120 μm or less.

2. The strengthened glass-ceramics according to claim 1.

11. Step 1, which performs a crystallization process on a base glass to obtain a base crystallized glass; Step 2 of subjecting the basic crystallized glass obtained by the crystallization treatment to ion exchange.

11. A method for preparing the strengthened glass-ceramics according to claim 1.

12. The ion exchange in step 2 includes two ion exchanges, First ion exchange: The basic glass-ceramics is immersed in a first molten salt bath to carry out the first ion exchange, and the first molten salt bath contains at least 75 wt % NaNO ３ The temperature of the first ion exchange is 430 to 450° C., and the time of the first ion exchange is 6 to 11 h; Second ion exchange: The basic glass-ceramics that has been subjected to the first ion exchange is immersed in a second molten salt bath to perform a second ion exchange, and the second molten salt bath contains at least KNO ３ and LiNO ３ The temperature of the second ion exchange is 420°C to 440°C, and the time of the second ion exchange is 60 minutes or less.

12. The method according to claim 11 .

13. In the second molten salt bath, ３ The content of LiNO is 90 wt % or more. ３ The content of LiNO is 0< ３ ≦0.15wt% 13. The method according to claim 12 .

14. The crystallization process in step 1 includes a step of placing the base glass in a box-type crystallization furnace and performing a three-stage heat treatment. In the first stage, the temperature is increased to 520°C to 580°C and kept at that temperature for 200 to 300 minutes. In the second stage, the temperature is increased to 600°C to 640°C and kept at that temperature for 100 to 150 minutes. In the third stage, the temperature is increased to 645°C to 740°C and kept at that temperature for 180 to 270 minutes, and then cooled to obtain a base crystallized glass.

12. The method according to claim 11 .

15. Use of the strengthened crystallized glass according to any one of claims 1 to 10 as a mobile phone cover, a tablet cover, a wristwatch cover, or an automobile display cover.

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