Anti-falling and anti-scratching lithium aluminum silicate glass and preparation method thereof

Abstract

The invention belongs to the technical field of glass manufacturing, and particularly relates to anti-falling and anti-scratching lithium aluminum silicate glass and a preparation method thereof.The anti-falling and anti-scratching lithium aluminum silicate glass is prepared from, by mass, 250.0%-65.0% of SiO2, 10.0%-20.0% of Al2O3, 2.0%-8.0% of Na2O, 1.0%-5.0% of K2O, 1.0%-5.0% of MgO, 1.0%-5.0% of ZrO2, 2.0%-8.0% of Li2O, 0.1%-2.0% of CaO, 1.0%-5.0% of Y2O3, 0.1%-5.0% of BaO and 0.05%-0.5% of additives; the additive is one or more of Fe2O3, Co2O3, CuO and Cr2O3; the mass ratio of BaO to Y2O3 is 1: (2-4). The problems of long founding time, low ion exchange process efficiency, low hardness, low bending strength and poor high-temperature stability of the existing lithium aluminosilicate glass preparation process are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of glass manufacturing, and particularly relates to a lithium aluminosilicate glass with anti-drop and anti-scratch properties and a preparation method thereof. Background Art

[0002] As an important special glass material, lithium aluminosilicate glass is widely used in the fields of electronic devices, photovoltaic modules, and safety protection due to its excellent mechanical strength, thermal stability, and chemical durability. The composition range of mainstream lithium aluminosilicate glass is roughly as follows in mass percentage: 55%-70% of SiO2, 12%-23% of Al2O3, 13%-16% of Na2O, 0%-5% of K2O, 2%-6% of MgO, 0%-5% of B2O3, and 0-2% of ZrO2.

[0003] However, the regulation range of the components of mainstream lithium aluminosilicate glass is narrow, and it is difficult to balance high hardness, high toughness, and excellent optical properties; increasing the content of Al2O3 leads to a sharp rise in the melting temperature and an exacerbation of the crystallization tendency; the flux (such as B2O3) added to reduce the melting temperature significantly reduces the chemical stability of the glass. The Vickers hardness of existing lithium aluminosilicate glass is generally 6-6.5 GPa, which is difficult to meet the requirements of high-end applications; the flexural strength is usually in the range of 300-400 MPa, and there is still room for improvement; the high-temperature stability is insufficient, and the performance decays significantly in a long-term high-temperature environment. Moreover, the existing preparation process usually requires 8-12 hours for melting, with a long cycle and high energy consumption; the ion exchange process is inefficient, and defects such as stripes and bubbles are likely to appear during the forming process, resulting in a low yield.

[0004] With the rapid development of industries such as consumer electronics and new energy, the performance requirements for lithium aluminosilicate glass are getting higher and higher. The majority of mobile phone terminal users are still not satisfied with simple anti-drop, anti-scratch, and anti-drop ball impact properties, and these traditional performance tests are often not applicable to the daily use environment. After the performance test of the cover glass produced by the traditional chemical strengthening process, the anti-drop and anti-scratch performance results and performance stability are mostly not ideal. In view of the defects of existing lithium aluminosilicate glass, it is urgent to develop a lithium aluminosilicate glass with anti-drop and anti-scratch properties and a preparation method thereof. Summary of the Invention

[0005] Aiming at the above problems, the present invention provides a new type of lithium aluminosilicate glass and a preparation method thereof, which are used to solve the problems of long melting time in the existing lithium aluminosilicate glass preparation process, low efficiency of the ion exchange process, low hardness, low flexural strength, and poor high-temperature stability.

[0006] To achieve the above object, the technical solution adopted by the present invention is: In a first aspect, the present invention provides a drop-resistant and scratch-resistant lithium aluminosilicate glass, which contains the following components, calculated by mass percentage: SiO2 50.0-65.0%, Al2O3 10.0-20.0%, Na2O 2.0-8.0%, K2O 1.0-5.0%, MgO 1.0-5.0%, ZrO2 1.0-5.0%, Li2O 2.0-8.0%, CaO 0.1-2.0%, Y2O3 1.0-5.0%, BaO 0.1-5.0%, and 0.05-0.5% of one or more of Fe2O3, Co2O3, CuO, and Cr2O3. By precisely controlling the BaO and Y2O3 contents, with Y2O3 1.0-5.0% and BaO 0.1-5.0% and a BaO to Y2O3 mass ratio of 1:2-4, the synergistic combination of the two can optimize the melting process and expand functions without sacrificing the core properties of lithium aluminosilicate glass (high strength and high heat resistance), thereby achieving the trinity optimization of "strength-heat resistance-function".

[0007] Furthermore, the lithium aluminosilicate glass has a thickness of 0.2-3.0 mm. SiO2 acts as a network former, constructing a three-dimensional continuous network through [SiO4] tetrahedrons. Its content is positively correlated with the glass transition temperature (Tg) (Tg = 480 + 1.2 × SiO2 mol %). SiO2 is essential for forming the glass skeleton, improving the strength and chemical stability of the glass and enabling it to achieve a lower thermal expansion coefficient. When the SiO2 content is too low, the glass's main network structure is poor, resulting in poor mechanical properties and reduced weather resistance. When the content is too high, the silicon-oxygen skeleton structure is excessively high, resulting in smaller network gaps, which is not conducive to chemical strengthening ion exchange and affects the efficiency of chemical strengthening. Furthermore, excessively high melting temperatures during glass production increase energy consumption and are prone to frequent defects such as bubbles and stones. Therefore, in aluminosilicate glass, the SiO2 content is controlled to be 50%-65%, specifically including but not limited to 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, and 64%. Alumina (Al2O3) is a necessary component to increase the ion exchange capacity of glass, and it can also improve the chemical stability and elastic modulus of glass. When its content is too low, the voids in the network space become smaller, which is not conducive to ion migration and seriously affects the efficiency of chemical strengthening; when its content is too high, the high-temperature viscosity of the glass increases significantly, the melting temperature is too high during the production process, energy consumption increases, and it is also not conducive to controlling defects such as bubbles and stones. Therefore, in aluminosilicate glass, the Al2O3 content is controlled to be 10%-20%, specifically including but not limited to: 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, and 19%. Al2O3 acts as a network intermediate, and the [AlO4] tetrahedron is formed through a charge compensation mechanism (each Al 3+One R is required + ) copolymerizes with the silica network to increase the glass viscosity by 1-2 orders of magnitude at the liquidus temperature; when the ratio is <1, the uncompensated Al 3+ exists in the network interstitial in the form of [AlO6] octahedra, resulting in a 20-30×10 -7 increase in the coefficient of thermal expansion per °C.

[0008] Furthermore, when Na2O + K2O + Li2O is in the range of 8% - 14% and the mass ratio of K2O, Na2O, and Li2O is 1:2 - 3:1.5 - 2.5, the ion exchange rate can be optimized within this range. The key components of ion exchange, Li2O and Na2O, form a synergistic effect. Li + (diffusion coefficient D = 10 -14 m² / s) is responsible for deep diffusion to build a stress gradient, and Na + (D = 10 -16 m² / s) dominates the formation of surface compressive stress. Lithium oxide (Li2O) is an ideal flux and an essential component for ion exchange. Due to the polarization characteristics of Li + , it can effectively reduce the high-temperature viscosity at high temperatures. Since the present invention uses a mixed molten salt of NaNO3 and KNO3 in the strengthening process, through the ion exchange of Li + in the glass with Na + in the molten salt, the depth of the compressive stress layer can be increased within a short time, making the glass have more excellent mechanical impact resistance. Therefore, in aluminosilicate glass, the Li2O content is controlled at 2% - 8%. Sodium oxide (Na2O) is another main flux and an essential component for ion exchange. It can significantly reduce the melting temperature of aluminosilicate glass and is also an essential component for ion exchange. If the content is too low, not only will the melting performance of the glass deteriorate, but also the stress value of the K-Na ion exchange layer will be too small, resulting in poor microhardness, easy crack formation, and a decrease in drop resistance; if the content is too high, the glass network structure will deteriorate, and the stability of mechanical and thermal properties will decrease, and the chemical durability will deteriorate. Therefore, in aluminosilicate glass, the Na2O content is controlled at 2% - 8%. Potassium oxide (K2O) can improve the melting performance of the glass. If the content is too high, the glass network structure will deteriorate significantly, and the stability of thermal properties will decrease. Therefore, in aluminosilicate glass, the K2O content is controlled at 1% - 5%. Zirconium oxide (ZrO2) can improve the chemical stability and ion exchange performance of the glass, increase the surface hardness of the glass, and can increase the pressure required for the glass to form cracks, making the glass more scratch and drop resistant. Only a small amount of ZrO2 is required to meet the requirements, so it is an essential component. However, too much ZrO2 will significantly increase the melting temperature of the glass and will also bring defects such as stones, which has an adverse impact on production. Therefore, when the ZrO2 addition amount is controlled at 0.5 - 2%, Zr 4+Suppress phase separation through the field strength effect, increasing the microhardness by 10 - 15%; when the content > 3%, the high-temperature viscosity of the melt increases, resulting in an increase in the clarification temperature by 50 - 80 °C. Ba 2+ As an alkaline earth metal ion, it can provide free oxygen (O 2- ), combine with the aluminum-oxygen tetrahedron ([AlO4] 5- ), neutralize the charge imbalance, and stabilize the glass network structure. Ba 2+ The relatively large ionic radius (1.35 Å) can hinder the orderly arrangement of the aluminosilicate network, reducing the risk of crystallization, especially significant when the Al2O3 content is high (> 20%). BaO can significantly reduce the melt viscosity. At 1500 °C, for every 1% increase in BaO, the viscosity decreases by about 10%, improving the melting performance of high-aluminum glass (Al2O3 content 25 - 30%). For high-aluminum glass containing 3% BaO, the melting temperature can be reduced by 50 - 80 °C. The addition of BaO can reduce the thermal expansion coefficient of the glass. Adding 2% BaO can reduce the CTE from 5.2×10 -6 / °C to 4.8×10 -6 / °C (in the range of 25 - 300 °C). Y 3+ (ionic radius 0.90 Å), as a high-field-strength cation, preferentially occupies the interstitial positions in the aluminosilicate network, forming strong bonds with the [AlO4]⁻ tetrahedron (the Y - O bond energy is about 600 kJ / mol), stabilizing the glass network structure. Y2O3 can significantly increase the crystallization activation energy of the glass, inhibiting the precipitation of crystal phases such as mullite (3Al2O3·2SiO2) in high-aluminum glass (Al2O3 content 25 - 30%). Adding 1% Y2O3 can increase the crystallization peak temperature from 980 °C to 1050 °C (DSC test). Y2O3 induces the formation of microcrystalline phases (such as YAG: Y3Al5O 12 ), enhancing toughness through the crack deflection mechanism: adding 2% Y2O3 can increase the fracture toughness (K1C) from 1.2 MPa·m 1 / 2 to 1.8 MPa·m 1 / 2 . Y2O3 reduces the melt viscosity (η) at high temperatures (> 1400 °C), improving the formability of high-aluminum glass: at 1550 °C, the viscosity of the glass containing 1% Y2O3 decreases from 10 3 Pa·s to 8×10 2 Pa·s. Magnesium oxide (MgO) can reduce the viscosity of the glass at high temperatures, promoting the melting and clarification of the glass. At low temperatures, it can enhance the stability of the glass network space, has a good repairing effect on the voids of the glass silicon-oxygen - aluminum-oxygen network structure, can reduce the thermal expansion coefficient of the glass to a certain extent, and can also increase the low-temperature viscosity of the glass and improve the glass strain point, which is an essential component. However, it has a certain hindering effect on ion exchange. When the content is too high, Mg 2+Seriously hinder the ion exchange ability of the glass, resulting in a significant reduction in the depth of the compressive stress layer of K-Na exchange. The effect of CaO is similar to that of MgO, and it can enhance the stability of the glass network space at low temperatures, but it also has an obvious hindering effect on ion exchange. Therefore, neither of them is an essential component. Alkaline earth metal oxides (MgO, CaO) stabilize the glass strain point at 520-550 °C through the "mixed alkaline earth effect", while expanding the temperature difference between the softening point and the annealing point to 150-200 °C, significantly improving the hot bending forming performance.

[0009] Furthermore, the novel lithium aluminosilicate glass contains the following components in mass percentages: SiO2 60.0-64.0%, Al2O3 18.0-20.0%, Na2O 4.0-6.0%, K2O 1.0-2.5%, MgO 1.0-2.0%, ZrO2 1.0-3.0%, Li2O 3.0-5.0%, CaO 0.1-1.0%, Y2O3 1.0-2.0%, BaO 0.1-1.0%, and one or more of Fe2O3, Co2O3, CuO, Cr2O3 0.05-0.5%.

[0010] In a second aspect, the present invention provides a method for preparing the lithium aluminosilicate glass described in the first aspect of the present invention, adopting a float process, specifically including the following steps: (1) Weigh the raw materials according to the formula ratio, and fully stir and mix the raw materials to obtain a batch mixture; (2) Perform high-temperature melting treatment on the batch mixture, and introduce ultrasonic treatment at the end of the melting treatment; (3) Cast the molten mixture into a mold and perform annealing to obtain a glass sheet; (4) Perform two-step chemical strengthening on the glass sheet to obtain the product lithium aluminosilicate glass.

[0011] Furthermore, the melting temperature is 1500-1600 °C, and the melting time is 6-8 h.

[0012] Furthermore, the ultrasonic wave is 20-40 kHz, and ultrasonic treatment is used for 30 minutes at the end of the melting treatment, which can reduce the generation of bubbles.

[0013] Furthermore, for the two-step strengthening, the first step of strengthening uses a mixed salt of sodium nitrate and potassium nitrate for strengthening, and the second step of strengthening uses pure potassium nitrate for strengthening. The strengthening temperature is 400-450 °C, and the strengthening time is 1-8 h.

[0014] During the glass strengthening process, when using potassium salts (such as potassium nitrate) and / or sodium salts (such as sodium nitrate) for chemical strengthening (ion exchange), the functions and advantages of each salt are different. The low-temperature characteristics of the eutectic system formed after mixing sodium nitrate and potassium nitrate form a compressive stress layer on the surface, reducing the process energy consumption and avoiding glass deformation due to high temperature. The mixed salt optimizes the ion exchange kinetics, making the stress layer deeper and enhancing the impact resistance and bending resistance. For secondary strengthening, pure KNO3 molten salt is used. The diffusion ability of K + is stronger and can penetrate deeper into the glass network structure. The K + concentration in pure KNO3 is higher, and the ion exchange efficiency is better. The compressive stress in the deep layer can more effectively prevent crack propagation.

[0015] Furthermore, in the mixed salt of sodium nitrate and potassium nitrate, the mass ratio of sodium nitrate to potassium nitrate is 1:1 - 3.

[0016] Beneficial Effects

[0017] (1) For the aluminosilicate strengthened glass provided by the present invention, by reasonably adjusting the composition of the aluminosilicate glass (Na2O, K2O, Li2O, BaO, Y2O3, etc.), the mechanical properties of the aluminosilicate strengthened glass are optimized. It has high hardness, high toughness, and is resistant to dropping and scratching, while also having excellent optical properties. It effectively alleviates the problem of easy generation of banded scratches in existing products, and at the same time enhances the drop resistance, surface scratch resistance, and chemical stability of the lithium aluminosilicate glass with anti-dropping and anti-scratching properties.

[0018] (2) The preparation method of the present invention reduces energy consumption through layered melting and ultrasonic treatment, and improves the strength by adjusting the specific operations and parameters of the strengthening steps. Compared with the traditional process, the present invention significantly shortens the melting process time, which is only 4 - 6h, saving energy consumption. Moreover, the process of the present invention has fewer defects such as process bubbles and a high yield. Brief Description of the Drawings

[0019] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0020] Figure 1 It is the scanning transmission microscopic image of the lithium aluminosilicate glass prepared in Example 1 of the present invention in the dark field; Figure 2 It is the scanning transmission microscopic image of the lithium aluminosilicate glass prepared in Example 1 of the present invention in the bright field. Detailed Embodiments

[0021] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below in conjunction with embodiments. The description in this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention.

[0022] Example 1

[0023] SiO2 63.0%, Al2O3 19.0%, Li2O 4.00%, MgO 1.70%, CaO 0.18%, ZrO2 2.50%, K2O 2.00%, Na2O 5.40%, Fe2O3 0.09%, Y2O3 1.60%, BaO 0.53%.

[0024] (1) Weigh the raw materials according to the formula ratio, and fully stir and mix the raw materials to obtain a batch mixture.

[0025] (2) Melt the batch mixture at 1550 °C for 6 h; introduce ultrasonic treatment for 30 minutes at the end of the melting treatment; the ultrasonic frequency is 20 - 40 kHz.

[0026] (4) Annealing treatment, the annealing temperature is 580 °C and the time is 1.5 h.

[0027] (5) Strengthening treatment, first immerse the lithium aluminosilicate glass in a molten mixed salt bath of sodium nitrate and potassium nitrate (the mass ratio of sodium nitrate to potassium nitrate is 1:1) at 415 °C for 150 min; then immerse it in molten potassium nitrate at 420 °C for 150 min.

[0028] Examples 2 - 6, new lithium aluminosilicate glasses are prepared by adjusting the contents of each component, and the specific compositions are shown in Table 1:

[0029] Comparative Example 1: Compared with Example 1, ultrasonic assistance is not used.

[0030] Comparative Example 2: Compared with Example 1, only the first strengthening is used, and the strengthening time is 300 min.

[0031] Comparative Example 3: Compared with Example 1, only the second strengthening is used, and the strengthening time is 300 min.

[0032] Comparative Example 4: Compared with Example 1, only sodium nitrate is used in the second strengthening process.

[0033] Comparative Example 5: Compared with Example 1, the ratio of barium oxide to yttrium oxide is 1:1, and the others remain unchanged.

[0034] Comparative Example 6: Compared with Example 1, the ratio of barium oxide to yttrium oxide is 1:5, and the others remain unchanged.

[0035] After testing, the performance parameters of Examples 1-6 and Comparative Examples 1-6 of the present invention are shown in Table 2 and Table 3 respectively.

[0036] Table 2 Test values of performance parameters of Examples 1-6

[0037] Table 3 Test values of performance parameters of Comparative Examples 1-6

[0038] This optimal implementation mode has been verified through pilot tests. The product yield reaches 95.5%, and the comprehensive performance index exceeds that of existing commercial lithium aluminosilicate glass products, having the value of industrial promotion.

[0039] It should be noted that in this article, the terms: including, containing and any other variants are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Specific examples are used in this article to elaborate on the principle and implementation mode of the technical solution of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention. The above is only the preferred implementation mode of the present invention. It should be pointed out that due to the limited nature of literal expression and objectively infinite specific structures, for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements, refinements or changes can be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the concept and technical solution of the present invention to other occasions without improvement, shall be regarded as the protection scope of the present invention.

Claims

1. A lithium aluminosilicate glass resistant to dropping and scratching, characterized in that, By mass percentage, it contains the following components: SiO2 50.0 - 65.0%, Al2O3 10.0 - 20.0%, Na2O 2.0 - 8.0%, K2O 1.0 - 5.0%, MgO 1.0 - 5.0%, ZrO2 1.0 - 5.0%, Li2O 2.0 - 8.0%, CaO 0.1 - 2.0%, Y2O3 1.0 - 5.0%, BaO 0.1 - 5.0%, and an additive 0.05 - 0.5%; the additive is one or more of Fe2O3, Co2O3, CuO, Cr2O3; wherein, the mass ratio of BaO to Y2O3 is 1:2 - 4.

2. The lithium aluminosilicate glass according to claim 1, wherein By mass percentage, it contains the following components: SiO2 60.0 - 64.0%, Al2O3 18.0 - 20.0%, Na2O 4.0 - 6.0%, K2O 1.0 - 2.5%, MgO 1.0 - 2.0%, ZrO2 1.0 - 3.0%, Li2O 3.0 - 5.0%, CaO 0.1 - 1.0%, Y2O3 1.0 - 2.0%, BaO 0.1 - 1.0%, and an additive 0.05 - 0.5%; wherein, the mass ratio of BaO to Y2O3 is 1:2 - 4.

3. The lithium aluminosilicate glass according to claim 1, wherein The thickness of the lithium aluminosilicate glass is 0.2 - 3.0 mm.

4. The lithium aluminosilicate glass according to claim 1, wherein, The total content of Na2O, K2O, and Li2O is 8% - 14%, and the mass ratio of K2O, Na2O, and Li2O is 1:2 - 3:1.5 - 2.

5.

5. The lithium aluminosilicate glass according to claim 4, wherein, n(R2O) / n(Al2O3) < 1, where R is Na, K, Li.

6. The preparation method of the lithium aluminosilicate glass according to any one of claims 1-5, characterized in that, It includes the following steps: (1) Weigh raw materials according to the formula ratio, and fully stir and mix the raw materials to obtain a batch mixture; (2) Perform high-temperature melting treatment on the batch mixture, and introduce ultrasonic treatment at the end of the melting treatment; (3) Pour the molten mixture into a mold and perform annealing to obtain a glass sheet; (4) Perform two-step chemical strengthening on the glass sheet to obtain the product lithium aluminosilicate glass.

7. The preparation method according to claim 6, characterized in that, The melting temperature is 1500 - 1600 °C, and the melting time is 6 - 8 h.

8. The preparation method according to claim 6, characterized in that, Perform ultrasonic treatment for 30 minutes, and the ultrasonic wave is 20 - 40 kHz.

9. The preparation method according to claim 6, characterized in that, The two-step strengthening is as follows: the first step of strengthening uses a mixed salt of sodium nitrate and potassium nitrate for strengthening, and the second step of strengthening uses pure potassium nitrate for strengthening. The strengthening temperature is 400 - 450 °C, and the strengthening time is 1 - 8 h.

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