High-strength low-warpage sodium-aluminum-silicon glass as well as strengthening method and application thereof

Abstract

The invention discloses high-strength low-warpage sodium-aluminum-silicon glass as well as a strengthening method and application thereof, and the high-strength low-warpage sodium-aluminum-silicon glass comprises the following components in percentage by mass: 57%-66% of SiO2, 15%-25% of Al2O3, 5%-15% of Na2O, 1%-3% of K2O, 1%-10% of RO, 0.5%-2% of ZrO2 and 0.5%-6% of Y2O3. By accurately controlling the content of each component of the glass, the glass has excellent chemical stability, thermal stability, mechanical strength and hardness and good melting performance and ion exchange efficiency, and the overall quality and performance of the glass are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of alkali-aluminosilicate glass manufacturing, and relates to high-strength, low-warpage sodium-aluminosilicate glass, a strengthening method thereof, and applications thereof. Background Art

[0002] Alkali-aluminosilicate glass has the characteristics of high hardness, high elastic modulus and high light transmittance, and is widely used in electronic products such as display screens of various smartphones, smart watches and computer monitors.

[0003] Currently, with the trend toward thinner and lighter display devices, cover glass thickness is gradually increasing from 1.1mm to 0.5mm. However, as glass becomes thinner, internal and surface defects are magnified, leading to a significant decrease in strength performance indicators such as impact resistance. Therefore, glass strengthening treatment is required to increase its strength.

[0004] The impact resistance of glass stems both from its intrinsic strength and from the impact resistance of the surface layer (DOL) and CCS (Cross-correlation) generated by ion exchange strengthening. Generally, the greater the COS and DOL, the greater the resistance to impact energy and crack propagation. Chemical strengthening involves exchanging smaller alkali metal ions in the glass with larger ions in a molten salt bath at a certain temperature. This creates a compressive stress layer on the surface due to volume expansion, inhibiting the propagation of Griffith microcracks into the glass interior and enhancing its strength. Currently, the mainstream strengthening method for soda-aluminosilicate glass is a one-step chemical strengthening process using pure potassium nitrate molten salt. This results in a shallow compressive stress layer. Achieving a greater compressive stress layer depth requires extending the ion exchange time or increasing the exchange temperature. However, excessively high exchange temperatures and long exchange times lead to stress relaxation, reducing the surface compressive stress. To achieve a higher surface compressive stress, the ion exchange temperature must be lowered, but this results in a smaller compressive stress layer depth. Consequently, the surface compressive stress and compressive stress layer depth achieved by ion exchange cannot be balanced, making the glass inadequate for impact resistance under extreme conditions. Moreover, during low-temperature ion exchange, the compressive stress on the glass surface first increases and then decreases as the compression depth of the stress layer increases. It is difficult to control the strengthening process, which can easily cause poor flatness (warpage value) of the strengthened glass. Poor flatness will affect the bonding effect of the glass, thereby affecting the impact resistance and drop resistance of electronic products. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength, low-warpage sodium-aluminum-silica glass and a strengthening method and application thereof, so as to solve the problem of poor strength and flatness of glass after strengthening by the existing one-step chemical strengthening process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A high-strength, low-warpage soda-aluminosilicate glass comprises, by mass percentage, 57%-66% of SiO2, 15%-25% of Al2O3, 5%-15% of Na2O, 1%-3% of K2O, 1%-10% of RO, 0.5%-2% of ZrO2, and 0.5%-6% of Y2O3.

[0007] Furthermore, the relationship between the mass percentages of ZrO2 and Al2O3 is: 0.02≤ZrO2 / Al2O3≤0.12.

[0008] Furthermore, the mass percentage of Na2O and K2O is: 0.09 <K2O / Na2O<0.2。

[0009] Furthermore, the RO is one or both of MgO and CaO.

[0010] A method for strengthening the high-strength, low-warpage soda-aluminosilicate glass comprises: Preheat the prepared potassium nitrate and glass; Mixing potassium nitrate and sodium nitrate, adding additives to prepare mixed nitrate, placing the preheated proportion into the mixed nitrate for the first ion exchange, cooling, washing, and obtaining a primary strengthened glass; The once strengthened glass is placed in preheated potassium nitrate, subjected to a second ion exchange, annealing, and cooling to obtain a secondary strengthened high-strength low-warpage sodium aluminum silicate glass.

[0011] Furthermore, the preheating temperature of the potassium nitrate is 400-440°C, and the preheating temperature of the glass is 380°C.

[0012] Furthermore, the mass percentage of the potassium nitrate and the sodium nitrate is 70%~90%:10%~30%.

[0013] Furthermore, the mass of the additive is 2% to 5% of the total mass of potassium nitrate and sodium nitrate, the additive is a mixture of Al2O3 and Li2O, and the mass ratio of Al2O3 to Li2O is 1:2.

[0014] Furthermore, the temperature of the first ion exchange is 390-420° C., and the time is 6-9 hours; The temperature of the second ion exchange is 405-420° C., and the time is 0.5-2 h.

[0015] The application of the high-strength, low-warpage sodium-aluminum-silicate glass in electronic display devices.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a high-strength, low-warpage sodium-aluminosilicate glass. By designing the SiO2 content to 57% to 66% by mass, the glass achieves desired solubility, chemical durability, and mechanical strength while stabilizing its network structure. Al2O3 (15% to 25% by mass) reduces the glass's crystallization tendency, improves its chemical stability, thermal stability, mechanical strength, and hardness, and increases its elastic modulus. It also provides ion exchange channels, which improves ion exchange efficiency. The co-introduction of Na2O and K2O facilitates a deeper ion exchange depth. MgO and CaO can be adjusted to reduce high-temperature viscosity and improve glass melting properties, but excessive content may cause glass crystallization. ZrO2 (0.5% to 2% by mass) improves the glass's chemical stability, resists crack formation and crack propagation, prevents the precipitation of alkali metal ions, and increases the glass's viscosity, hardness, elasticity, refractive index, and chemical stability. It also reduces the glass's thermal expansion coefficient and enhances the glass's network structure, thereby increasing its toughness. Y2O3 improves the glass's network structure and Young's modulus, thereby increasing its intrinsic strength. By precisely controlling the content of each glass component, this invention achieves excellent chemical and thermal stability, mechanical strength, and hardness, as well as good melting properties and ion exchange efficiency. This avoids issues like glass devitrification and ensures the overall quality and performance of the glass.

[0017] The present invention also provides a method for strengthening high-strength, low-warpage sodium-aluminum-silica glass. This method utilizes a two-step process. The first step involves strengthening in a mixed nitrate bath containing additives to increase the ion exchange rate and depth, enabling a deeper stress layer compression depth to be achieved in a shorter period of time. The second step involves rapid strengthening in a molten salt containing a high concentration of potassium nitrate to achieve a suitable compressive stress on the glass surface, thereby avoiding warping of the glass sheet after strengthening and simultaneously improving the impact resistance of the sodium-aluminum-silica glass. The present invention enhances the intrinsic strength of the glass by adding high-valent metal ion oxides. Furthermore, the two-step chemical strengthening method achieves a higher surface compressive stress and a deeper ion exchange depth, improving the glass surface smoothness to a certain extent while also enhancing the impact resistance of the sodium-aluminum-silica glass.

[0018] Furthermore, a mixture of Al2O3 and Li2O is added as an additive. Al2O3 absorbs the resulting infusible materials and protects the glass surface from molten salt transition erosion. Al2O3 replaces SiO2 or Na2O in the glass, increasing the ion volume while accelerating the entry of molten salt ions into the glass, promoting rapid ion exchange, and resulting in high surface stress and impact resistance after strengthening the glass. The diameter of the lithium ions in Li2O intervenes between the potassium and sodium ions. Through the intermediate activation of the lithium ions, the ion replacement efficiency is improved and, more importantly, the uniformity of the compressive stress layer formed after potassium ion replacement is enhanced. DETAILED DESCRIPTION

[0019] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0021] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values within the range (including integers and fractions).

[0022] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0023] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0024] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0025] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0026] The present invention will be further described in detail below: The present invention provides a high-strength and low-warpage sodium aluminosilicate glass, which, by mass percentage, comprises 57% - 66% of SiO2, 15% - 25% of Al2O3, 5% - 15% of Na2O, 1% - 3% of K2O, 1% - 10% of RO, 0.5% - 2% of ZrO2, and 0.5% - 6% of Y2O3.

[0027] SiO2 is an important glass-forming oxide and the framework in the glass structure. It can increase the melting temperature, viscosity, chemical stability, thermal stability, hardness, strain point, and mechanical strength of the glass, and can also reduce the thermal expansion coefficient and density of the glass. However, too high content of SiO2 will cause an increase in melting temperature and viscosity, which is not conducive to glass melting and clarification. Therefore, the content of SiO2 is limited to 57% - 66%.

[0028] Al2O3 is an intermediate oxide, which can reduce the crystallization tendency of the glass and improve the chemical stability, thermal stability, mechanical strength, hardness, and elastic modulus of the glass. When the molar ratio of Na2O + K2O / Al2O3 in the glass is greater than 1, aluminum-oxygen tetrahedrons [AlO4] are formed, creating large channels for the migration and diffusion of alkali ions. Therefore, a high content of Al2O3 in the glass can promote the migration and replacement rate of alkali metal ions. However, too high content of Al2O3 will lead to an increase in the high-temperature viscosity of the glass, which is not conducive to controlling defects such as bubbles and stones. Therefore, the content of Al2O3 is limited to 15% - 25%.

[0029] Na2O can provide free oxygen to increase the O / Si ratio in the glass structure, break the bonds in the glass network structure, reduce the viscosity of the glass, and make the glass easier to melt. In addition, Na ions are necessary ion-exchange components. When a high content of Na ions is in the voids of the glass structure network, it can be exchanged by larger ions in molten salts (such as KNO3). Without losing other properties, the content of Na should be as high as possible to provide a sufficient number of ion-exchange sites. Therefore, the content of Na2O is limited to 5% - 15%.

[0030] K2O can reduce the high-temperature viscosity of the glass and improve the melting property and formability of the glass. For a mixed-alkali glass containing both K2O and Na2O, an increase in the content of K2O will increase the stress depth. However, when the content of K2O exceeds 3%, it will hinder the ion-exchange speed and affect the strengthening effect. Therefore, the content of K2O is limited to 1% - 3%. In addition, the mass percentages of Na2O and K2O satisfy the following relationship: 0.09 < K2O / Na2O < 0.2. By controlling the ratio of K2O and Na2O, a higher surface compressive stress and stress layer compression depth can be obtained.

[0031] Alkaline earth metal oxides, which can be selected from MgO, CaO, and combinations thereof, can be added to enhance the meltability, durability, and stability of the glass. Alkaline earth metal oxides can be added as stabilizers to help prevent degradation of the glass composition upon exposure to environmental conditions. Furthermore, they offer numerous advantages in improving stress relaxation while minimizing the adverse effects on alkali metal diffusivity. However, excessive addition of alkaline earth metal oxides to the glass composition can reduce its formability, so the RO content is limited to 1% to 10%.

[0032] ZrO2 can significantly increase the ion exchange performance of aluminosilicate glass and increase the strain point. It can also increase the hardness of the glass after chemical strengthening and improve the chemical stability of the glass. However, excessive ZrO2 will increase the number of coordination structures. 4+ The ionic radius is large, and this group is a network modifier in the glass structure, which can cause crystallization. Therefore, the ZrO2 content is limited to 0.5%~2%.

[0033] Y2O3 has the effect of tightening the glass structure, increasing the internal packing density, improving the glass's network structure and Young's modulus, thereby enhancing the glass's intrinsic strength. It also improves the chemical strengthening properties of the glass, enhancing the stress effect per unit ion exchange in chemically strengthened glass, and reducing warpage. However, excessive addition to the glass composition is not recommended, as it reduces the chemical strengthening rate, makes the glass more susceptible to devitrification, and reduces its manufacturability. Therefore, the Y2O3 content is limited to 0.5% to 6%.

[0034] The high-strength, low-warpage soda-aluminosilicate glass of the present invention is prepared by preparing raw materials according to the above-mentioned composition, melting and clarifying the raw materials, and then forming the glass. The alkaline earth metal oxide additives MgO and CaO can be added separately or in combination. The proper ratio is key to achieving optimal performance.

[0035] The method for strengthening high-strength, low-warpage sodium-aluminosilicate glass of the present invention is a two-step ion exchange method, which specifically includes the following steps: Heat the prepared potassium nitrate to 400-440°C to form a molten state and keep the temperature stable through temperature control. Preheat the glass to 380°C in the preheating area and keep the temperature constant for 30 minutes. The first step is ion exchange: the mass percentage of potassium nitrate and sodium nitrate is 70%~90%:10%~30%. 2%~5% of the total mass of additives are added to the potassium nitrate and sodium nitrate raw materials to make a mixed nitrate. The additive is a mixture of Al2O3 and Li2O in a mass ratio of 1:2. The preheated glass is exchanged at 390~420℃ for 6~9h to obtain a deeper stress layer compression depth. It is then slowly removed from the molten salt, placed in a slow cooling area for annealing, and then slowly cooled to room temperature and cleaned.

[0036] The second step is ion exchange: the mass percentage of potassium nitrate is 100%, and the glass that has completed the first step of ion exchange is exchanged at 405-420°C for 0.5-2 hours. A high-concentration potassium nitrate melt is used to quickly strengthen the glass to obtain a suitable surface compressive stress. The glass is slowly removed from the molten salt, placed in a slow cooling area for annealing, and then slowly cooled to room temperature. After cleaning, the high-strength, low-warpage sodium aluminum silicate glass of the present invention is obtained.

[0037] The present invention provides five embodiments. The specific ingredients, strengthening processes and performance parameters of the material recipes in Examples 1 to 5 are shown in Table 1.

[0038] Table 1 Comparison of glass composition, strengthening process and performance of various examples

[0039] The present invention uses FSM-6000+SLP1000 to measure the surface compressive stress CS and stress layer compression depth DOL of the samples in Examples 1 to 5 above; a fully automatic drop ball tester to measure the impact strength of the samples; and a four-point bending strength tester to measure the flexural strength of the above samples. The results show that after the first strengthening, the compressive stress on the glass surface is 560~710MPa, and the stress layer compression depth is 44~50μm; after the second strengthening, the compressive stress on the glass surface is 720~950MPa, and the stress layer compression depth is 46~53μm. The sodium aluminum silicate glass of the present invention significantly improves the ion exchange rate during the strengthening process, and due to the improved uniformity of the permeation layer, the warping of the glass sheet after strengthening is avoided. After the glass is chemically strengthened by ion exchange, the crack propagation on the glass surface is further strengthened, thereby improving the strength of the glass, enhancing the impact resistance, and increasing the service life of the glass.

[0040] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-strength, low-warpage sodium-aluminosilicate glass, characterized in that: Calculated by mass percentage, it includes 57%~66% SiO2, 15%~25% Al2O3, 5%~15% Na2O, 1%~3% K2O, 1%~10% RO, 0.5%~2% ZrO2 and 0.5%~6% Y2O3.

2. The high-strength, low-warpage sodium aluminosilicate glass according to claim 1, characterized in that: The relationship between the mass percentages of ZrO2 and Al2O3 is: 0.02≤ZrO2 / Al2O3≤0.

12.

3. The high-strength, low-warpage soda-aluminosilicate glass according to claim 1, characterized in that: The mass percentage relationship between Na2O and K2O is: 0.09 <K2O / Na2O<0.2。 4. The high-strength, low-warpage sodium aluminosilicate glass according to claim 1, characterized in that: The RO is one or both of MgO and CaO.

5. A method for strengthening the high-strength, low-warpage soda-aluminosilicate glass according to any one of claims 1 to 4, characterized in that: include: Preheat the prepared potassium nitrate and glass; Mixing potassium nitrate and sodium nitrate, adding additives to prepare mixed nitrate, placing the preheated proportion into the mixed nitrate for the first ion exchange, cooling, washing, and obtaining a primary strengthened glass; The once strengthened glass is placed in preheated potassium nitrate, subjected to a second ion exchange, annealing, and cooling to obtain a secondary strengthened high-strength low-warpage sodium aluminum silicate glass.

6. The method for strengthening high-strength, low-warpage soda-aluminosilicate glass according to claim 5, wherein: The preheating temperature of the potassium nitrate is 400-440°C, and the preheating temperature of the glass is 380°C.

7. The method for strengthening high-strength, low-warpage soda-aluminosilicate glass according to claim 5, wherein: The mass percentage of the potassium nitrate and sodium nitrate is (70%~90%):(10%~30%).

8. The method for strengthening high-strength, low-warpage soda-aluminosilicate glass according to claim 5, wherein: The mass of the additive is 2% to 5% of the total mass of potassium nitrate and sodium nitrate. The additive is a mixture of Al2O3 and Li2O, and the mass ratio of Al2O3 to Li2O is 1:

2.

9. The method for strengthening high-strength, low-warpage soda-aluminosilicate glass according to claim 5, wherein: The temperature of the first ion exchange is 390-420°C and the time is 6-9 hours; The temperature of the second ion exchange is 405-420° C., and the time is 0.5-2 h.

10. Use of the high-strength, low-warpage soda-aluminosilicate glass according to any one of claims 1 to 4 in electronic display devices.

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