Reinforcing process for improving weather resistance of glass cover plate

Abstract

The invention relates to the technical field of glass cover plates, in particular to a strengthening process for improving weather resistance of a glass cover plate, which comprises the following steps: (1) primary strengthening; (2) secondary strengthening; (3) low-temperature annealing; and (4) vacuum coating. According to the strengthening process disclosed by the invention, secondary strengthening is adopted, so that the surface compressive stress and the compressive stress layer depth of the glass can be remarkably improved, the impact resistance and the falling resistance are enhanced, and the scratch resistance and the wear resistance are improved; heat treatment is carried out by adopting low-temperature annealing under the condition that the temperature is lower than the ion exchange temperature but higher than the use environment temperature, so that the stress is slightly relaxed in advance under the controlled condition, a more stable stress structure is formed, and the stress structure does not change easily when encountering a high-temperature and high-humidity environment in the future; a physical barrier can be established on the surface of the glass by adopting vacuum coating to isolate corrosive substances such as water vapor, acid and alkali from being in contact with the surface of the glass, so that microcrack growth and strength reduction caused by environmental erosion are prevented.

Description

Technical Field

[0001] This invention relates to the field of glass cover technology, and more specifically to a strengthening process for improving the weather resistance of glass covers. Background Technology

[0002] Consumer electronic devices and display devices (e.g., smartphones, tablets, e-readers, and laptops) often incorporate chemically strengthened glass as a cover glass. To improve the impact resistance of glass, reinforced nanocrystalline glass has been developed, becoming a standard feature in high-end consumer electronic devices and display devices. Nanocrystalline glass is a multiphase composite material with both glass and microcrystalline phases, formed through nucleation crystallization heat treatment. It possesses the excellent properties of both glass and ceramic materials, such as high optical transparency, good mechanical stability, and customizable optical properties. Some practical and potential applications involve long-term use in high-temperature, high-humidity, and thermal cycling environments, and much research focuses on the influence of preparation processes and application environments. As the application scope of microcrystalline glass continues to expand, further research is needed to consider the influence of composition, crystallization processes, and environmental parameters (temperature, strain, etc.) on its structure, performance, and applications. Application environments in fields such as electronics, instrumentation, and medicine involve complex temperature and humidity variations. With the deepening development of microcrystalline glass applications in these fields, research on the weather resistance of microcrystalline glass is required. Microcrystalline glass for mobile phone cover plates boasts advantages such as high impact resistance, good scratch resistance, and adjustable optical properties, making it an increasingly popular material for mobile phone cover plates. However, microcrystalline glass for mobile phone cover plates also faces complex operating environments and is easily contaminated by moisture, sweat, and oil. Therefore, weather resistance is a crucial performance characteristic. In lithium aluminum silicon microcrystalline glass, compared to its matrix glass, the silica phase is partially consumed and crystallized, disrupting the glass's network structure and making it more susceptible to water corrosion. After chemical strengthening, Li+ ions on the glass surface are replaced by Na+ ions. Since Na+ ions have lower weather resistance than Li+ ions, the overall weather resistance of the glass is further reduced.

[0003] Existing chemical strengthening methods are complex and most fail to balance strength and weather resistance. Chinese invention patent CN115432945A discloses a chemical strengthening method to improve the weather resistance of nanocrystalline glass, mainly involving ion exchange technology. This method involves completely immersing the glass in a salt bath for chemical strengthening. The salt bath consists of NaNO3 of industrial grade or higher purity, combined with flux and LiNO3 of industrial grade or higher purity. This patent effectively improves the strength and weather resistance of microcrystalline glass through a one-step ion exchange chemical strengthening method, ensuring the overall performance of the glass in applications such as mobile phones and automotive parts facing complex climatic conditions. However, there is still room for improvement in both strength and weather resistance. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a strengthening process for improving the weather resistance of glass cover plates.

[0005] The objective of this invention is achieved through the following technical solution: a strengthening process for improving the weather resistance of glass cover plates, comprising the following steps:

[0006] (1) First strengthening: The cleaned glass cover plate is preheated at 380-400℃ for 40-80 min, then placed in the first mixed molten salt and strengthened at 420-440℃ for 4-8 h. The strengthened glass is dripped with salt for 4-6 min and then transferred to room temperature to cool for 20-40 min.

[0007] (2) Secondary strengthening: The glass cover plate after the first strengthening is preheated at 380-400℃ for 40-80 minutes, and then placed in the second mixed molten salt and strengthened at 420-440℃ for 2-4 hours. After the strengthened glass is dripped with salt for 4-6 minutes, it is then transferred to room temperature for cooling.

[0008] (3) Low temperature annealing: Heat the glass cover plate after secondary strengthening to 280-320℃, keep it at the temperature for 1-3h, and slowly cool it to room temperature at a cooling rate of 1-3℃ / min.

[0009] (4) Vacuum Coating: After low-temperature annealing, the glass cover plate is cleaned and placed in a vacuum coating machine, where it is coated to a temperature of 1×10⁻⁶. -3 -5×10 -3 Pa, preheating temperature is 80-120℃, fluorine-containing material is used for coating treatment, coating time is 1-5min, and coating thickness is 5-20nm.

[0010] Preferably, in step (1), the first mixed molten salt comprises the following raw materials in parts by weight: 85-95 parts potassium nitrate, 4-12 parts sodium nitrate, and 1-3 parts potassium carbonate. Potassium carbonate can purify impurities in the molten salt, thereby improving the purity and transparency of the molten salt. This invention utilizes the exchange reaction between lithium ions and sodium or potassium ions in the salt bath by strictly controlling the weight ratio of the first mixed molten salt. During the strengthening process, lithium ions on the glass surface first exchange with sodium ions in the salt bath, thus initially forming stress.

[0011] Preferably, in step (2), the second mixed molten salt comprises the following raw materials in parts by weight: 95-98 parts potassium nitrate, 1-2 parts potassium pyrophosphate, 0.5-1.5 parts silicon dioxide, and 0.5-1.5 parts silicic acid. Potassium pyrophosphate stabilizes the ion concentration while removing iron impurities from the molten salt, solving the technical problem of iron impurities adhering to the glass surface, affecting ion migration and exchange, causing uneven ion concentration in local areas of the glass surface, low surface compressive stress, and uneven stress, leading to dent defects. The addition of amorphous silicon dioxide improves chemical durability and the mechanical properties of chemically strengthened glass, while also adsorbing impurities in the molten salt. The presence of silicic acid purifies impurities in the molten salt, thereby improving the purity and transparency of the molten salt. This invention, by strictly controlling the weight ratio of the second mixed molten salt, allows potassium ions to replace sodium ions on the surface, further enhancing the compressive stress. After double replacement reinforcement, double-strength glass can form a deeper compressive stress layer, which makes double-strength glass perform well in terms of drop resistance and bending resistance, making it particularly suitable for scenarios with extremely high requirements for wear resistance and impact resistance.

[0012] The principle of low-temperature annealing is to allow overly active ions (such as insufficiently "anchored" Na+) in the glass network to dissipate. + or K + Fine-tuning is performed to move the micro-stress concentration point to a more stable position, thereby releasing the main compressive stress and preventing it from easily relaxing in subsequent high temperature and high humidity environments.

[0013] Preferably, in step (4), the surface cleaning step specifically involves cleaning the glass cover plate with an alkaline cleaning agent, rinsing it with pure water, cleaning it with plasma, and finally drying it at high temperature. The parameters for plasma cleaning are: the gas is oxygen or argon, the power is 200-500W, the time is 60-180s, and the pressure is 10-50Pa.

[0014] The alkaline cleaning agent comprises the following raw materials in parts by weight: 2-8 parts potassium hydroxide, 4-8 parts monoethanolamine, 6-10 parts fatty alcohol polyoxyethylene ether, 1-5 parts sodium dodecylbenzenesulfonate, 1-2 parts hydroxyethylidene diphosphonic acid, 0.5-1.5 parts sodium silicate, 2-4 parts propylene glycol butyl ether, and the balance being deionized water.

[0015] The alkaline cleaning agent of this invention utilizes potassium hydroxide as a strong inorganic base, providing alkalinity and saponification capabilities; KOH is even more alkaline and has a better saponification effect on greases. It employs monoethanolamine as an organic base, which has strong penetrability, assists in dissolving organic dirt, is easy to rinse, and has a better effect when combined with inorganic bases. It uses fatty alcohol polyoxyethylene ether, which wets, penetrates, and emulsifies, and is stable under alkaline conditions, assisting in the removal of particulate dirt. It uses sodium dodecylbenzenesulfonate, which enhances detergency and anti-redeposition, has good synergy with the alkali, and is low in cost. It uses hydroxyethylidene diphosphonic acid, which softens water, disperses particles, prevents scale deposition, and suspends the removed polishing powder and metal particles, preventing their secondary adsorption. It uses sodium silicate, which protects glass by forming a protective film on the glass surface, reducing the corrosion of glass by alkali, especially beneficial for chamfered edges. It uses propylene glycol butyl ether for coupling and solubilization, helping to dissolve non-polar greases, improving the penetration of the cleaning agent into oil stains, and promoting water washability.

[0016] The alkaline cleaning agent of the present invention, by using the above-mentioned raw materials and strictly controlling the weight ratio of each raw material, can powerfully remove more stubborn process dirt, such as polishing powder residue, cutting oil, metal particles, and deeper fingerprint grease, while causing no irreversible damage to the glass substrate itself.

[0017] Preferably, in step (4), the fluorinated material is a mixture of trimethylfluorosilane and perfluoropolyether in a mass ratio of 1-2:1. This invention, by strictly controlling the type, compounding, and proportion of the fluorinated material, forms a thin film that isolates water vapor, acids, alkalis, and other corrosive substances from contacting the glass surface, thereby preventing the growth of microcracks and a decrease in strength caused by environmental erosion.

[0018] Preferably, in step (1), the glass cover is lithium aluminum silicate glass, which, by weight percentage, comprises the following components: SiO2: 58%-68%, Al2O3: 10%-15%, Li2O: 8%-12%, Na2O: 1%-2%, K2O: 0.5%-1.5%, MgO: 3%-5%, CaO: 1.5%-2.5%, B2O3: 0.1%-0.5%, P2O5: 0.5%-1.5%, BaO: 0-2%, Sb2O3: 0-2%, ZrO2: 0-2%, SnO2: 0-0.5%, and RE2O3: 0.3%-3%, the sum of the weight percentages of the above components being 100%.

[0019] This invention utilizes lithium aluminum silicate glass and strictly controls the weight percentage of each component. The resulting lithium aluminum silicate glass, after secondary strengthening, exhibits high surface compressive stress and stress layer compression depth, as well as excellent drop resistance and bending resistance. It is particularly suitable for scenarios with extremely high requirements for wear resistance and impact resistance.

[0020] More preferably, the lithium aluminum silicate glass comprises the following components by weight percentage: SiO2: 60%-66%, Al2O3: 11%-14%, Li2O: 9%-11%, Na2O: 1.2%-1.8%, K2O: 0.8%-1.2%, MgO: 3.5%-4.5%, CaO: 1.8%-2.2%, B2O3: 0.2%-0.4%, P2O5: 0.8%-1.2%, BaO: 0.5%-1.5%, Sb2O3: 0.6%-1.4%, ZrO2: 0.5%-1.5%, SnO2: 0.1%-0.3%, and RE2O3: 1%-2%, the sum of the weight percentages of the above components being 100%.

[0021] The reasons for limiting the glass composition to the above range are explained below:

[0022] Silica (SiO2) is the main component forming the glass framework, improving the glass's strain point, chemical stability, and mechanical strength, while reducing its coefficient of thermal expansion and density. When the content is below 50%, the glass's chemical stability is poor; however, when the content exceeds 68%, the high-temperature viscosity of the glass increases, leading to excessively high melting temperatures and difficulties in melting. To obtain glass with high Young's modulus suitable for rapid chemical strengthening, the SiO2 content is limited to 58%-68%, preferably 60%-66%.

[0023] Alumina (Al₂O₃) is an intermediate oxide that improves the hardness and mechanical strength of glass, enhances its chemical stability, and accelerates ion exchange on the glass surface. When the Al₂O₃ content is below 10%, the ion exchange effect is poor, and the chemical stability of the glass is compromised. When the Al₂O₃ content exceeds 18%, the glass viscosity increases, and its anti-devitrification properties deteriorate. Therefore, the Al₂O₃ content is limited to 10%-15%, preferably 11%-14%.

[0024] Lithium oxide (Li₂O) is the most critical component for achieving glass with a double stress layer. The glass composition must have a sufficiently high Li₂O content to ensure adequate Li-Na ion exchange during the Li-Na ion exchange process in a Na-containing molten salt, enabling rapid formation of the second surface stress layer. If the Li₂O content in the glass is too low, the Li-Na ion exchange capacity is insufficient, and the exchange is easily affected by the molten salt concentration, leading to instability. Extensive experiments have shown that when the Li₂O concentration in the glass is above 8%, the Li-Na ion exchange effect is significantly improved; simultaneously, Li₂O can rapidly reduce the viscosity of the glass, especially at high temperatures, which is beneficial for glass melting and clarification, particularly for glass compositions with high SiO₂ and Al₂O₃ content. However, high Li₂O content reduces glass stability and increases raw material costs; therefore, the Li₂O concentration in this invention is below 12%.

[0025] Sodium oxide (Na₂O) is the main component in the formation of the first surface compressive stress layer through ion exchange. The exchange of Na ions with K ions achieves high surface compressive stress on the glass surface. Simultaneously, as an external network, it acts as a network disruptor in the glass structure, facilitating glass melting. However, excessive Na₂O can limit the stress value at the interface between the first and second surface compressive stress layers. Furthermore, excessive Na₂O can cause a deterioration in a range of glass properties, such as chemical resistance and mechanical properties. Therefore, the Na₂O content is limited to 1%-2%, preferably 1.2%-1.8%.

[0026] Potassium oxide (K₂O) can reduce the high-temperature viscosity of glass, improving its melting and formability. Furthermore, it reacts with sodium... + Ion exchange enhances the ion exchange rate during chemical strengthening through interdiffusion, thereby achieving the desired compressive stress and deepening the compressive stress layer, while also improving the glass's resistance to devitrification. When the K₂O content exceeds 3%, it hinders the ion exchange rate and affects the strengthening effect. A K₂O content between 0.5% and 1.5% not only increases the etching rate but also shortens the ion exchange treatment time; therefore, the K₂O content is limited to 0.5%-1.5%, with a preferred content of 0.8%-1.2%.

[0027] Magnesium oxide (MgO) is an outer layer of the glass network; introducing a certain amount can promote glass melting and lower its melting temperature. MgO can also reduce crystallization tendency and rate, and improve the chemical stability of the glass. If the MgO content is below 2%, the effect of lowering the glass melting temperature is not significant; however, its content should not be excessive. If it exceeds 6%, it can lead to porous glass, decreased density, easy crystallization, and an excessively high coefficient of thermal expansion. Therefore, its content is limited to 3%-5%, preferably 3.5%-4.5%.

[0028] Calcium oxide (CaO) is a component that reduces the high-temperature viscosity of glass, provides chemical stability, and promotes the melting and formability of glass. It also increases the strain point or tensile modulus of elasticity of glass. When the CaO content exceeds 3%, the ion exchange performance deteriorates, the strengthening effect weakens, and the deterioration resistance of the glass worsens. Therefore, the CaO content is limited to 1.5%-2.5%, with a preferred content of 1.8%-2.2%.

[0029] Barium oxide (BaO) can improve the chemical stability and mechanical strength of glass. However, Ba... 2+ The diameter of the ion affects the ion diffusion rate, and the larger the ion radius, the more significant the effect. At the same time, a larger ion radius can block alkaline ion channels to some extent. Therefore, the BaO content is limited to 0-2%, with a preferred content of 0.5%-1.5%.

[0030] Boron oxide (B2O3) is mainly used to lower the melting temperature of glass, second only to alkali metals. It can accelerate the melting and clarification of glass, improve the luster of glass, enhance the chemical stability of glass, and also improve the mechanical properties of glass. However, a B2O3 content greater than 1 wt% will inhibit the ion exchange depth of glass. Therefore, its content is limited to 0.1%-0.5%, preferably 0.2%-0.4%.

[0031] Phosphorus oxide (P₂O₅) is used to accelerate the ion exchange rate of glass and can also lower the melting temperature of glass. P₂O₅ forms a network of interconnected [PO₄] tetrahedra. This network structure is layered, with layers linked by van der Waals forces. If the content exceeds 2%, the chemical stability of the glass decreases, and the coefficient of thermal expansion increases. Therefore, its content is limited to 0.5%-1.5%, preferably 0.8%-1.2%.

[0032] Zirconium dioxide (ZrO2) can significantly increase the ion exchange performance and strain point of aluminosilicate glass. It can also increase the strength of the matrix glass and improve the chemical stability, thermal stability and scratch resistance of the glass. However, when the content is higher than 3%, the melting temperature of the glass increases and the amount of unmelted matter in the glass increases. Therefore, its content is limited to 0-2%, preferably 0.5%-1.5%.

[0033] Antimony oxide (Sb₂O₃) and tin oxide (SnO₂) are both added as clarifying agents to the glass composition of the present invention, with addition amounts of 0-2% and 0-0.5% respectively. They can eliminate bubbles in the molten glass, achieving the effect of completely removing bubbles while saving raw materials.

[0034] In addition, the aluminosilicate glass of the present invention must also meet the following requirements:

[0035] Preferably, the components satisfy the following formula: 71% ≤ SiO2 + Al2O3 ≤ 80%. This can improve the mechanical strength and ion exchange efficiency of the glass.

[0036] Preferably, the component satisfies the following formula: 3.0 ≤ Li₂O / (Na₂O+K₂O) ≤ 5.5. This can increase the ion exchange rate in chemical strengthening to obtain the desired surface compressive stress and stress layer compression depth.

[0037] Preferably, the components satisfy the following formula: 5.8% ≤ MgO + CaO + BaO ≤ 8.2%. Although alkaline earth metal oxides can stabilize glass and prevent crystallization, they also hinder ion exchange. Therefore, the present invention controls the amount of MgO + CaO + BaO to 5.8%-8.2%.

[0038] Preferably, the components satisfy the following formula: 1.2% ≤ Sb₂O₃ + ZrO₂ + SnO₂ ≤ 3.2%. This can improve the chemical stability, thermal stability, and scratch resistance of the glass.

[0039] Preferably, the RE2O3 is a mixture of Ce2O3, Nd2O3, Gd2O3, and Y2O3 in a weight ratio of 2-4:1.5-2.5:1:0.2-0.6. The addition of Ce2O3 can be used in combination with SnO2 as a clarifying agent to help eliminate bubbles and impurities, improve the purity and light transmittance of the glass, and can also improve the glass's radiation resistance and anti-yellowing properties on its own. The addition of Nd2O3 can improve the accuracy of the color display of the glass cover. The combination of Gd2O3 and Y2O3 can enhance the stability of the glass network, making it more water-resistant and acid-resistant; Y2O3 can also increase the hardness and elastic modulus of the glass, making it more scratch-resistant and less prone to permanent deformation during bending, enhancing thermal stability, increasing the glass's transition temperature and softening point, and making it more resistant to high-temperature environments.

[0040] The beneficial effects of this invention are as follows: The strengthening process of this invention, by employing secondary strengthening and strictly controlling the temperature and time of each strengthening, can significantly increase the compressive stress and compressive stress layer depth on the glass surface, enhance impact and drop resistance, improve scratch resistance and wear resistance, and also improve fatigue resistance and extend service life; By using low-temperature annealing for heat treatment at a temperature below the ion exchange temperature but above the ambient temperature, the stress undergoes slight, pre-relaxed stress under controlled conditions, thereby forming a more stable stress structure that will not easily change when encountering high temperature and high humidity environments in the future; By using vacuum coating, a physical barrier can be established on the glass surface to prevent water vapor, acids, alkalis and other corrosive substances from contacting the glass surface, thereby preventing the growth of microcracks and strength reduction caused by environmental erosion. Detailed Implementation

[0041] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0042] Example 1

[0043] A strengthening process for improving the weather resistance of glass covers includes the following steps:

[0044] (1) First strengthening: The cleaned glass cover plate is preheated at 380℃ for 80 minutes, then placed in the first mixed molten salt and strengthened at 420℃ for 8 hours. The strengthened glass is dripped with salt for 4 minutes and then transferred to room temperature for 20 minutes to cool.

[0045] (2) Secondary strengthening: The glass cover plate after the first strengthening is preheated at 380℃ for 80 minutes, and then placed in the second mixed molten salt and strengthened at 420℃ for 4 hours. After the strengthened glass is dripped with salt for 4 minutes, it is then transferred to room temperature for cooling.

[0046] (3) Low temperature annealing: Heat the glass cover plate after secondary strengthening to 280℃, keep it at the temperature for 3 hours, and slowly cool it to room temperature at a cooling rate of 1℃ / min.

[0047] (4) Vacuum Coating: After low-temperature annealing, the glass cover plate is cleaned and placed in a vacuum coating machine, where it is coated to a temperature of 1×10⁻⁶. -3 Pa, preheating temperature is 80℃, fluorine-containing material is used for coating treatment, coating time is 1min, and coating thickness is 5nm.

[0048] In step (1), the first mixed molten salt comprises the following raw materials in parts by weight: 85 parts potassium nitrate, 12 parts sodium nitrate, and 3 parts potassium carbonate.

[0049] In step (2), the second mixed molten salt comprises the following raw materials in parts by weight: 95 parts potassium nitrate, 2 parts potassium pyrophosphate, 1.5 parts silicon dioxide and 1.5 parts silicic acid.

[0050] In step (4), the surface cleaning step specifically involves: first cleaning the glass cover with an alkaline cleaning agent, then rinsing it with pure water, then cleaning it with plasma, and finally drying it at high temperature. The parameters for plasma cleaning are: gas is oxygen or argon, power is 200W, time is 180s, and pressure is 10Pa. The alkaline cleaning agent includes the following raw materials in parts by weight: 2 parts potassium hydroxide, 4 parts monoethanolamine, 6 parts fatty alcohol polyoxyethylene ether, 1 part sodium dodecylbenzenesulfonate, 1 part hydroxyethylidene diphosphonic acid, 0.5 parts sodium silicate, 2 parts propylene glycol butyl ether, and the remainder is deionized water.

[0051] In step (4), the fluorinated material is a mixture of trimethylfluorosilane and perfluoropolyether in a mass ratio of 1:1.

[0052] In step (1), the glass cover is lithium aluminum silicate glass, which, by weight percentage, comprises the following components: SiO2: 60%, Al2O3: 14%, Li2O: 11%, Na2O: 1.2%, K2O: 1.2%, MgO: 4.5%, CaO: 2.2%, B2O3: 0.4%, P2O5: 0.8%, BaO: 0.5%, Sb2O3: 1.4%, ZrO2: 1.5%, SnO2: 0.3%, and RE2O3: 1%. The RE2O3 is a mixture of Ce2O3, Nd2O3, Gd2O3, and Y2O3 in a weight ratio of 2:1.5:1:0.2.

[0053] Example 2

[0054] A strengthening process for improving the weather resistance of glass covers includes the following steps:

[0055] (1) First strengthening: The cleaned glass cover plate is preheated at 390℃ for 60 minutes, then placed in the first mixed molten salt and strengthened at 430℃ for 6 hours. The strengthened glass is dripped with salt for 5 minutes and then transferred to room temperature for 30 minutes to cool.

[0056] (2) Secondary strengthening: The glass cover plate after the first strengthening is preheated at 390℃ for 60 minutes, and then placed in the second mixed molten salt and strengthened at 430℃ for 3 hours. After the strengthened glass is dripped with salt for 5 minutes, it is then transferred to room temperature for cooling.

[0057] (3) Low temperature annealing: Heat the glass cover plate after secondary strengthening to 300℃, keep it at the temperature for 2h, and slowly cool it to room temperature at a cooling rate of 2℃ / min.

[0058] (4) Vacuum Coating: After low-temperature annealing, the glass cover plate is cleaned and placed in a vacuum coating machine, where it is coated to 3×10⁻⁶ mm. -3 Pa, preheating temperature is 100℃, fluorine-containing material is used for coating treatment, coating time is 3min, and coating thickness is 12nm.

[0059] In step (1), the first mixed molten salt comprises the following raw materials in parts by weight: 90 parts potassium nitrate, 8 parts sodium nitrate, and 2 parts potassium carbonate.

[0060] In step (2), the second mixed molten salt comprises the following raw materials in parts by weight: 96 parts potassium nitrate, 2 parts potassium pyrophosphate, 1 part silicon dioxide and 1 part silicic acid.

[0061] In step (4), the surface cleaning step specifically involves: first cleaning the glass cover with an alkaline cleaning agent, then rinsing it with pure water, then cleaning it with plasma, and finally drying it at high temperature; the parameters for plasma cleaning are: gas is oxygen or argon, power is 350W, time is 120s, and pressure is 30Pa. The alkaline cleaning agent includes the following raw materials in parts by weight: 5 parts potassium hydroxide, 6 parts monoethanolamine, 8 parts fatty alcohol polyoxyethylene ether, 3 parts sodium dodecylbenzenesulfonate, 1.5 parts hydroxyethylidene diphosphonic acid, 1 part sodium silicate, 3 parts propylene glycol butyl ether, and the remainder is deionized water.

[0062] In step (4), the fluorinated material is a mixture of trimethylfluorosilane and perfluoropolyether in a mass ratio of 1.5:1.

[0063] In step (1), the glass cover is lithium aluminum silicate glass, which, by weight percentage, comprises the following components: SiO2: 63%, Al2O3: 12.5%, Li2O: 10%, Na2O: 1.5%, K2O: 1%, MgO: 4%, CaO: 2%, B2O3: 0.3%, P2O5: 1%, BaO: 1%, Sb2O3: 1%, ZrO2: 1%, SnO2: 0.2%, and RE2O3: 1.5%. The RE2O3 is a mixture of Ce2O3, Nd2O3, Gd2O3, and Y2O3 in a weight ratio of 3:2:1:0.4.

[0064] Example 3

[0065] A strengthening process for improving the weather resistance of glass covers includes the following steps:

[0066] (1) First strengthening: The cleaned glass cover plate is preheated at 400℃ for 40 minutes, then placed in the first mixed molten salt and strengthened at 440℃ for 4 hours. The strengthened glass is dripped with salt for 6 minutes and then transferred to room temperature for 40 minutes to cool.

[0067] (2) Secondary strengthening: The glass cover plate after the first strengthening is preheated at 400℃ for 40 minutes, and then placed in the second mixed molten salt and strengthened at 440℃ for 2 hours. The strengthened glass is dripped with salt for 6 minutes and then transferred to room temperature for cooling.

[0068] (3) Low temperature annealing: Heat the glass cover plate after secondary strengthening to 320℃, keep it at the temperature for 1 hour, and slowly cool it to room temperature at a cooling rate of 3℃ / min.

[0069] (4) Vacuum Coating: After low-temperature annealing, the glass cover plate is cleaned and placed in a vacuum coating machine, where it is coated to 5×10⁻⁶ mm. -3Pa, preheating temperature is 120℃, fluorine-containing material is used for coating treatment, coating time is 5min, and coating thickness is 20nm.

[0070] In step (1), the first mixed molten salt comprises the following raw materials in parts by weight: 95 parts potassium nitrate, 4 parts sodium nitrate, and 1 part potassium carbonate.

[0071] In step (2), the second mixed molten salt comprises the following raw materials in parts by weight: 98 parts potassium nitrate, 1 part potassium pyrophosphate, 0.5 parts silicon dioxide and 0.5 parts silicic acid.

[0072] In step (4), the surface cleaning step specifically involves: first cleaning the glass cover with an alkaline cleaning agent, then rinsing it with pure water, then cleaning it with plasma, and finally drying it at high temperature; the parameters for plasma cleaning are: gas is oxygen or argon, power is 500W, time is 60s, and pressure is 50Pa. The alkaline cleaning agent includes the following raw materials in parts by weight: 8 parts potassium hydroxide, 8 parts monoethanolamine, 10 parts fatty alcohol polyoxyethylene ether, 5 parts sodium dodecylbenzenesulfonate, 2 parts hydroxyethylidene diphosphonic acid, 1.5 parts sodium silicate, 4 parts propylene glycol butyl ether, and the remainder is deionized water.

[0073] In step (4), the fluorinated material is a mixture of trimethylfluorosilane and perfluoropolyether in a mass ratio of 2:1.

[0074] In step (1), the glass cover is lithium aluminum silicate glass, which, by weight percentage, comprises the following components: SiO2: 66%, Al2O3: 11%, Li2O: 9%, Na2O: 1.8%, K2O: 0.8%, MgO: 3.5%, CaO: 4.8%, B2O3: 0.2%, P2O5: 1.2%, BaO: 1.5%, Sb2O3: 0.6%, ZrO2: 0.5%, SnO2: 0.1%, and RE2O3: 2%. The RE2O3 is a mixture of Ce2O3, Nd2O3, Gd2O3, and Y2O3 in a weight ratio of 4:2.5:1:0.6.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 2 above is that step (3) low-temperature annealing is not used.

[0077] Comparative Example 2

[0078] The difference between this comparative example and Example 2 above is that step (4) vacuum coating is not used.

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 2 above is that the first mixed molten salt in step (1) does not contain potassium carbonate.

[0081] Comparative Example 4

[0082] The difference between this comparative example and Example 2 above is that the second mixed molten salt in step (2) does not contain potassium pyrophosphate, silicon dioxide and silicic acid.

[0083] Comparative Example 5

[0084] The difference between this comparative example and Example 2 above is that the lithium aluminum silicate glass does not contain rare earth oxide RE2O3.

[0085] The performance tests of the tempered glass obtained in Examples 1-3 and Comparative Examples 1-5 are shown in the table below:

[0086]

[0087] As can be seen from the table above, the strengthening process of the present invention, by employing secondary strengthening and strictly controlling the temperature and time of each strengthening, can significantly increase the compressive stress on the glass surface and the depth of the compressive stress layer, enhance impact and drop resistance, improve scratch resistance and wear resistance, improve fatigue resistance, and extend service life. By using low-temperature annealing for heat treatment at a temperature lower than the ion exchange temperature but higher than the ambient temperature, the stress undergoes slight, pre-relaxed stress under controlled conditions, thereby forming a more stable stress structure that will not easily change when encountering high temperature and high humidity environments in the future. Compared with Comparative Example 1, which does not use low-temperature annealing, all properties are significantly improved.

[0088] The strengthening process of this invention can establish a physical barrier on the glass surface by using vacuum coating, which isolates water vapor, acids, alkalis and other corrosive substances from contacting the glass surface, thereby preventing the growth of microcracks and the decrease in strength caused by environmental erosion. Compared with Comparative Example 2, which does not use vacuum coating, the acid resistance, thermal cycling resistance and damp heat resistance are significantly improved.

[0089] The strengthening process of the present invention, by adding potassium carbonate to the first mixed molten salt and adding potassium pyrophosphate, silicon dioxide and silicic acid to the second mixed molten salt, significantly improves the compressive stress value and stress layer depth of the glass surface compared with Comparative Example 3 without potassium carbonate and Comparative Example 4 without potassium pyrophosphate, silicon dioxide and silicic acid.

[0090] This invention utilizes lithium aluminum silicate glass and adds a certain proportion of rare earth oxides. Compared with Comparative Example 5, the lithium aluminum silicate glass prepared by secondary strengthening has higher surface compressive stress and stress layer compression depth. The surface compressive stress of the glass can reach more than 950 MPa, and the stress layer compression depth can reach more than 160 μm. It also has excellent drop resistance and bending resistance, making it particularly suitable for scenarios with extremely high requirements for wear resistance and impact resistance.

[0091] The testing standards are as follows:

[0092] Transmittance: Take a sample with a thickness of 2mm after polishing and test the transmittance of the glass. The test wavelength is 380-760nm with a step size of 10nm.

[0093] Heat resistance cycling performance test standard: Tested according to standard JC / T2170-2013(2017) / 6.10. The sample temperature is cycled between -40℃ and 85℃ for 200 cycles. The average attenuation of the effective solar transmittance after the test should not exceed 1%.

[0094] The test standard for resistance to damp heat is as follows: The test shall be conducted in accordance with standard JC / T2170-2013(2017) / 6.12. The temperature is 85℃, the relative humidity is 85%, and the test duration is 1000 hours. The average attenuation of the effective solar transmittance after the test should not exceed 1%.

[0095] Acid resistance test standard: Tested according to standard JC / T2170-2013(2017) / 6.8. The sample is placed in a 1mol / L hydrochloric acid solution at (23±2)℃ and immersed for 24h. The average attenuation of the effective transmittance of sunlight after the test should not be greater than 1%.

[0096] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A strengthening process for improving the weather resistance of glass cover plates, characterized in that: Includes the following steps: (1) First strengthening: The cleaned glass cover plate is preheated at 380-400℃ for 40-80 min, then placed in the first mixed molten salt and strengthened at 420-440℃ for 4-8 h. The strengthened glass is dripped with salt for 4-6 min and then transferred to room temperature to cool for 20-40 min. (2) Secondary strengthening: The glass cover plate after the first strengthening is preheated at 380-400℃ for 40-80 minutes, and then placed in the second mixed molten salt and strengthened at 420-440℃ for 2-4 hours. After the strengthened glass is dripped with salt for 4-6 minutes, it is then transferred to room temperature for cooling. (3) Low temperature annealing: Heat the glass cover plate after secondary strengthening to 280-320℃, keep it at the temperature for 1-3h, and slowly cool it to room temperature at a cooling rate of 1-3℃ / min. (4) Vacuum Coating: After low-temperature annealing, the glass cover plate is cleaned and placed in a vacuum coating machine, where it is coated to a temperature of 1×10⁻⁶. -3 -5×10 -3 Pa, preheating temperature is 80-120℃, fluorine-containing material is used for coating treatment, coating time is 1-5min, and coating thickness is 5-20nm.

2. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: In step (1), the first mixed molten salt comprises the following raw materials in parts by weight: 85-95 parts potassium nitrate, 4-12 parts sodium nitrate, and 1-3 parts potassium carbonate.

3. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: In step (2), the second mixed molten salt comprises the following raw materials in parts by weight: 95-98 parts potassium nitrate, 1-2 parts potassium pyrophosphate, 0.5-1.5 parts silicon dioxide and 0.5-1.5 parts silicic acid.

4. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: In step (4), the surface cleaning step is as follows: the glass cover is first cleaned with an alkaline cleaning agent, then rinsed with pure water, then cleaned with plasma, and finally dried at high temperature; the parameters of plasma cleaning are: gas is oxygen or argon, power is 200-500W, time is 60-180s, and pressure is 10-50Pa.

5. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: In step (4), the fluorinated material is a mixture of trimethylfluorosilane and perfluoropolyether in a mass ratio of 1-2:

1.

6. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: In step (1), the glass cover is lithium aluminum silicate glass, which, by weight percentage, comprises the following components: SiO2: 58%-68%, Al2O3: 10%-15%, Li2O: 8%-12%, Na2O: 1%-2%, K2O: 0.5%-1.5%, MgO: 3%-5%, CaO: 1.5%-2.5%, B2O3: 0.1%-0.5%, P2O5: 0.5%-1.5%, BaO: 0-2%, Sb2O3: 0-2%, ZrO2: 0-2%, SnO2: 0-0.5%, and RE2O3: 0.3%-3%, the sum of the weight percentages of the above components being 100%.

7. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: The components satisfy the following formula: 3.0≤Li2O / (Na2O+K2O)≤5.

5.

8. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: The components satisfy the following formula: 6.8% ≤ MgO + CaO + BaO ≤ 8.2%.

9. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: The components satisfy the following formula: 1.2% ≤ Sb₂O₃ + ZrO₂ + SnO₂ ≤ 3.2%.

10. The strengthening process for improving the weather resistance of glass cover plates according to claim 1, characterized in that: The RE2O3 is composed of Ce2O3, Nd2O3, Gd2O3, and Ho2O3 in a weight ratio of 2-4: A mixture consisting of 1.5-2.5:1:0.2-0.6.

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