Glass cover plate with ultrahigh anti-falling strength and preparation method thereof

Abstract

The invention relates to the technical field of glass cover plates, in particular to a glass cover plate with ultrahigh anti-falling strength and a preparation method thereof, and the preparation method comprises the following steps: CNC processing; pre-grinding; strengthening: A, pretreatment; b, primary strengthening; c, secondary strengthening; flat grinding; primary cleaning; screen printing; and performing secondary cleaning. According to the preparation method disclosed by the invention, in the pretreatment process, grease, dust and metal particles on the surface can be thoroughly removed by adopting a neutral or alkaline cleaning agent, pure water rinsing, ultrasonic cleaning and high-temperature drying, so that stress concentration points caused by pollutants in the strengthening process are reduced, and breakage is caused; in the first strengthening, a deeper ion exchange layer is established by utilizing the higher diffusion rate of potassium ions at high temperature, namely, the depth of a pressure stress layer is increased; in the second strengthening, exchange is carried out at a relatively low temperature on the basis of a formed deep layer, and very high surface pressure stress is established on the surface layer by utilizing a huge volume effect generated at the low temperature.

Description

Technical Field

[0001] This invention relates to the field of glass cover technology, specifically to a glass cover with ultra-high drop resistance and its preparation method. Background Technology

[0002] With the development of communication technology, the thinning, larger screen, and portability of mobile terminal devices have rapidly become the market mainstream. Simultaneously, with the increasing prevalence of 5G and wireless charging technologies, the use of glass for the back covers of mobile communication devices (such as mobile phones and smartwatches) has become an inevitable trend. This places higher demands on the front and back cover glass materials used to protect the display devices. How to improve the mechanical strength of glass while simultaneously making it thinner and larger, thus ensuring that the screen does not crack when the mobile communication device is bumped, struck, or dropped from a height (over 150cm) onto rough surfaces (such as cement floors, gravel, asphalt roads), has become a key research focus for major original glass manufacturers and cover glass manufacturers.

[0003] Currently, the protective glass used in display devices on the market is usually medium-high alumina glass or lithium aluminum silicon glass. After primary or secondary strengthening, its surface compressive stress (CS) can reach 700-800 MPa, and its stress layer depth (DOL) can reach 40-100 μm, exhibiting good mechanical properties. However, glass is a brittle material containing many Griffith cracks. Glass breakage is the result of crack propagation. Although the chemically strengthened surface compressive stress layer can play a certain role in sealing cracks, the resistance to crack propagation is limited (it becomes ineffective beyond the compressive stress layer depth). Therefore, when assembled and applied to mobile terminal devices, its overall resistance to impact from sharp objects and drop resistance is still insufficient, especially when dropped from a height onto a rough surface. When the drop height exceeds 120 cm, the screen breakage rate increases significantly.

[0004] Chinese invention patent CN115490428A discloses a transparent microcrystalline glass with ultra-high drop resistance and its preparation method, belonging to the field of glass manufacturing. This transparent microcrystalline glass, by mass percentage of oxides, comprises: 60-78% SiO2, 3-11% Al2O3, 8-16% Li2O, 2-6% ZrO2, 1-4% P2O5, and 0.1-4% clarifying agent. This transparent microcrystalline glass has a spherical crystalline phase and a glassy phase, wherein the spherical crystalline phase includes at least lithium disilicate and lithium feldspar. The transparent microcrystalline glass has a transmittance greater than 86% and a haze less than 0.5% in the visible light range, and can withstand a drop height greater than 180cm with sandpaper, exhibiting high transmittance, high strength, ultra-strong impact resistance, and excellent drop resistance. However, there is still room for improvement in the drop height of this microcrystalline glass. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a glass cover plate with ultra-high drop resistance and its preparation method.

[0006] The objective of this invention is achieved through the following technical solution: a method for preparing a glass cover with ultra-high drop resistance, comprising the following steps:

[0007] (1) CNC machining: The glass cover plate is machined and the holes are engraved using CNC machining;

[0008] (2) Pre-grinding: Overlap the CNC-machined glass cover plates and polish the edges of the glass cover plates.

[0009] (3) Strengthening: The ground glass cover plate is placed into the glass holder for chemical strengthening;

[0010] A. Pretreatment: First, clean the glass cover with a neutral or alkaline cleaning agent, then rinse with pure water, then clean with ultrasonic cleaner, and finally dry at high temperature.

[0011] B. Primary strengthening: After cleaning the glass cover plate, place it in the first mixed molten salt and strengthen it at 420-440℃ for 4-6 hours. Then, slowly cool the strengthened glass to below 150℃ at a rate of 1-3℃ / min, and then transfer it to room temperature for cooling.

[0012] C. Secondary strengthening: After cleaning the glass cover plate, place it in the second mixed molten salt and strengthen it at 370-390℃ for 0.5-1.5h. Then, slowly cool the strengthened glass to below 150℃ at a rate of 1-3℃ / min, and then transfer it to room temperature for further cooling.

[0013] (4) Surface grinding: Place the reinforced glass cover plate on the grinding fixture, and then polish the surface of the glass cover plate.

[0014] (5) First cleaning: Place the ground glass cover into the glass holder and clean it;

[0015] (6) Screen printing: Place the cleaned glass cover plate into the screen printing fixture and screen print the printing area of ​​the glass cover plate.

[0016] (7) Second cleaning: Place the screen-printed glass cover into the glass holder and clean it.

[0017] Preferably, in step A, the neutral cleaning agent comprises the following raw materials in parts by weight: 8-15 parts fatty alcohol polyoxyethylene ether, 5-10 parts alkyl glycoside, 4-8 parts propylene glycol methyl ether, 2-6 parts isopropanol, 1-5 parts disodium ethylenediaminetetraacetate, 0.01-0.05 parts benzotriazole, 0.1-0.3 parts 2-amino-2-methyl-1-propanol, with deionized water as the balance.

[0018] This invention utilizes a neutral cleaning agent, fatty alcohol polyoxyethylene ether, as the primary cleaning agent. It is non-ionic, neutral, low-foaming, has good degreasing properties, is easy to rinse, and is coating-friendly. Alkyl glycosides are used as auxiliary cleaning agents; these are naturally derived, non-toxic, biodegradable, and synergistically solubilize and remove contaminants. Propylene glycol methyl ether is used as a coupling agent and oil stain penetrant to dissolve fingerprint grease, aid solubilization, promote leveling, and has a moderate evaporation rate. Isopropanol is used as a fast-drying solvent to help quickly dissolve organic stains and accelerate drying; however, its content should not be too high to avoid damaging the coating. Disodium EDTA is used as a softener to soften water, preventing the precipitation of calcium and magnesium ions and avoiding watermarks on glass. Benzotriazole is used as a metal ion passivator to prevent slight corrosion of the metal by the cleaning solution if the cover plate has a metal frame. A pH adjuster is used to stabilize the pH value, precisely adjusting the final product's pH to 6.5-7.5.

[0019] The neutral cleaning agent of this invention, by using the above-mentioned raw materials and strictly controlling the weight ratio of each raw material, can effectively remove fingerprints, grease, and dust particles from the glass surface, providing highly efficient cleaning, no corrosion, no residue, safety and environmental protection, and no corrosion to glass and coatings.

[0020] Preferably, in step A, 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.

[0021] 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.

[0022] 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.

[0023] Preferably, in step B, 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 sodium phosphate. Sodium phosphate can complex metal ions, increasing ionic strength; this invention utilizes lithium ions (Li+) by strictly controlling the weight ratio of the first mixed molten salt. + ) and sodium ions (Na) in the salt bath + ) or potassium ions (K + An exchange reaction occurs. During the strengthening process, lithium ions on the glass surface first exchange with sodium ions in the salt bath, thus initially forming stress.

[0024] Preferably, in step C, the second mixed molten salt comprises the following raw materials in parts by weight: 96-98 parts potassium nitrate, 0.5-1.5 parts potassium phosphate, and 1.5-2.5 parts potassium chloride. Potassium phosphate, as a highly efficient molten salt purifier, plays a crucial role in the stability, uniformity, and final glass properties of the strengthening process. Potassium chloride accelerates the ion exchange reaction through induction and also purifies 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 this double replacement strengthening, the double-strength glass can form a deeper compressive stress layer, resulting in excellent drop and bending resistance, making it particularly suitable for applications requiring extremely high wear and drop resistance.

[0025] 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%.

[0026] 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.

[0027] 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%.

[0028] The reasons for limiting the glass composition to the above range are explained below:

[0029] 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%.

[0030] 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%.

[0031] 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%.

[0032] 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%.

[0033] 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%.

[0034] 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%.

[0035] 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%.

[0036] 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%.

[0037] 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%.

[0038] 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%.

[0039] 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%.

[0040] 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.

[0041] In addition, the aluminosilicate glass of the present invention must also meet the following requirements:

[0042] Preferably, the components satisfy the following formula: 71% ≤ SiO2 + Al2O3 ≤ 80%. This can improve the mechanical strength and ion exchange efficiency of the glass.

[0043] 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.

[0044] 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%.

[0045] 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.

[0046] 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.

[0047] Another objective of the present invention is achieved by the following technical solution: a glass cover with ultra-high drop resistance, wherein the glass cover is prepared according to the above-described preparation method.

[0048] The beneficial effects of this invention are as follows: In the preparation method of this invention, the pretreatment by using neutral or alkaline cleaning agents, rinsing with pure water, ultrasonic cleaning, and high-temperature drying can thoroughly remove grease, dust, and metal particles from the surface, reducing the stress concentration points caused by contaminants during the strengthening process and preventing cracking; the first strengthening utilizes the faster diffusion rate of potassium ions at high temperatures to establish a deeper ion exchange layer, that is, to increase the depth of the compressive stress layer; the second strengthening, based on the already formed deep layer, carries out exchange at a relatively low temperature, utilizing the huge volume effect generated at low temperatures to establish a very high surface compressive stress on the surface layer.

[0049] The reinforced glass cover obtained by the preparation method of the present invention has high surface compressive stress and stress layer compression depth, as well as excellent drop resistance and bending resistance, making it particularly suitable for scenarios with extremely high requirements for wear resistance and drop resistance. Detailed Implementation

[0050] 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.

[0051] Example 1

[0052] A method for preparing a glass cover with ultra-high drop resistance includes the following steps:

[0053] (1) CNC machining: The glass cover plate is machined and the holes are engraved using CNC machining;

[0054] (2) Pre-grinding: Overlap the CNC-machined glass cover plates and polish the edges of the glass cover plates.

[0055] (3) Strengthening: The ground glass cover plate is placed into the glass holder for chemical strengthening;

[0056] A. Pretreatment: First, clean the glass cover with a neutral or alkaline cleaning agent, then rinse with pure water, then clean with ultrasonic cleaner, and finally dry at high temperature.

[0057] B. Primary strengthening: After cleaning the glass cover plate, place it in the first mixed molten salt and strengthen it at 420℃ for 4 hours. Then, slowly cool the strengthened glass to below 150℃ at a rate of 1℃ / min, and then transfer it to room temperature for cooling.

[0058] C. Secondary strengthening: After cleaning the glass cover plate, place it in the second mixed molten salt and strengthen it at 370℃ for 1.5h. Then, slowly cool the strengthened glass to below 150℃ at a rate of 1℃ / min, and then transfer it to room temperature for cooling.

[0059] (4) Surface grinding: Place the reinforced glass cover plate on the grinding fixture, and then polish the surface of the glass cover plate.

[0060] (5) First cleaning: Place the ground glass cover into the glass holder and clean it;

[0061] (6) Screen printing: Place the cleaned glass cover plate into the screen printing fixture and screen print the printing area of ​​the glass cover plate.

[0062] (7) Second cleaning: Place the screen-printed glass cover into the glass holder and clean it.

[0063] In step A, the neutral cleaning agent comprises the following raw materials in parts by weight: 8 parts fatty alcohol polyoxyethylene ether, 5 parts alkyl glycoside, 4 parts propylene glycol methyl ether, 2 parts isopropanol, 1 part disodium ethylenediaminetetraacetate, 0.01 parts benzotriazole, 0.1 parts 2-amino-2-methyl-1-propanol, and the balance being deionized water.

[0064] In step A, the alkaline cleaning agent comprises 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 deionized water.

[0065] In step B, 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 sodium phosphate.

[0066] In step C, the second mixed molten salt comprises the following raw materials in parts by weight: 96 parts potassium nitrate, 1.5 parts potassium phosphate, and 2.5 parts potassium chloride.

[0067] 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.

[0068] Example 2

[0069] The difference between this embodiment and Embodiment 1 above is that chemical strengthening includes the following steps:

[0070] A. Pretreatment: First, clean the glass cover with a neutral or alkaline cleaning agent, then rinse with pure water, then clean with ultrasonic cleaner, and finally dry at high temperature.

[0071] B. Primary strengthening: After cleaning the glass cover plate, place it in the first mixed molten salt and strengthen it at 430℃ for 5 hours. Then, slowly cool the strengthened glass to below 150℃ at a rate of 2℃ / min, and then transfer it to room temperature for cooling.

[0072] C. Secondary strengthening: After cleaning the glass cover plate, place it in the second mixed molten salt and strengthen it at 380℃ for 1 hour. Then, slowly cool the strengthened glass to below 150℃ at a rate of 2℃ / min, and then transfer it to room temperature for cooling.

[0073] In step A, the neutral cleaning agent comprises the following raw materials in parts by weight: 12 parts fatty alcohol polyoxyethylene ether, 7 parts alkyl glycoside, 6 parts propylene glycol methyl ether, 4 parts isopropanol, 3 parts disodium ethylenediaminetetraacetate, 0.03 parts benzotriazole, 0.2 parts 2-amino-2-methyl-1-propanol, and the balance being deionized water.

[0074] In step A, the alkaline cleaning agent comprises 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 being deionized water.

[0075] In step B, 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 sodium phosphate.

[0076] In step C, the second mixed molten salt comprises the following raw materials in parts by weight: 97 parts potassium nitrate, 1 part potassium phosphate, and 2 parts potassium chloride.

[0077] 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.

[0078] Example 3

[0079] The difference between this embodiment and Embodiment 1 above is that chemical strengthening includes the following steps:

[0080] A. Pretreatment: First, clean the glass cover with a neutral or alkaline cleaning agent, then rinse with pure water, then clean with ultrasonic cleaner, and finally dry at high temperature.

[0081] B. Primary strengthening: After cleaning the glass cover plate, place it in the first mixed molten salt and strengthen it at 440℃ for 4 hours. Then, slowly cool the strengthened glass to below 150℃ at a rate of 3℃ / min, and then transfer it to room temperature for cooling.

[0082] C. Secondary strengthening: After cleaning the glass cover plate, place it in the second mixed molten salt and strengthen it at 390℃ for 0.5h. Then, slowly cool the strengthened glass to below 150℃ at a rate of 3℃ / min, and then transfer it to room temperature for cooling.

[0083] In step A, the neutral cleaning agent comprises the following raw materials in parts by weight: 15 parts fatty alcohol polyoxyethylene ether, 10 parts alkyl glycoside, 8 parts propylene glycol methyl ether, 6 parts isopropanol, 5 parts disodium ethylenediaminetetraacetate, 0.05 parts benzotriazole, 0.3 parts 2-amino-2-methyl-1-propanol, and the balance being deionized water.

[0084] In step A, the alkaline cleaning agent comprises 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 being deionized water.

[0085] In step B, 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 sodium phosphate.

[0086] In step C, the second mixed molten salt comprises the following raw materials in parts by weight: 98 parts potassium nitrate, 0.5 parts potassium phosphate, and 1.5 parts potassium chloride.

[0087] 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.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Example 2 above is that step A preprocessing is not used.

[0090] Comparative Example 2

[0091] The difference between this comparative example and Example 2 above is that the first mixed molten salt in step B does not contain sodium phosphate.

[0092] Comparative Example 3

[0093] The difference between this comparative example and Example 2 above is that the second mixed molten salt in step C does not contain potassium phosphate and potassium chloride.

[0094] Comparative Example 4

[0095] The difference between this comparative example and Example 2 above is that rare earth oxide RE2O3 is not added.

[0096] The performance tests of the tempered glass prepared in Examples 1-3 and Comparative Examples 1-2 are shown in the table below:

[0097]

[0098] As can be seen from the table above, the strengthening process of the present invention performs pretreatment before secondary strengthening, which significantly improves the glass stress layer depth, surface compressive stress value, and bending strength compared to Comparative Example 1 without pretreatment. By adding sodium phosphate to the first mixed molten salt and potassium phosphate and potassium chloride to the second mixed molten salt, the surface compressive stress value, bending strength, and stress layer depth of the glass are significantly improved compared to Example 2 without sodium phosphate and Example 3 without potassium phosphate and potassium chloride. The present invention uses lithium aluminum silicate glass and adds a certain proportion of rare earth oxides. Compared with Comparative Example 4, 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 870 MPa, and the stress layer compression depth can reach more than 145 μm. It also has excellent drop resistance and bending resistance, and is particularly suitable for scenarios with extremely high requirements for wear resistance and impact resistance.

[0099] 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 method of making a glass cover plate with ultra-high drop strength, characterized by: It comprises the following steps: (1) CNC processing: the glass cover plate is processed in shape and hole position by CNC; (2) Pre-grinding: the glass cover plate after CNC processing is overlapped, and the edge of the glass cover plate is polished; (3) Strengthening: the glass cover plate after grinding is placed in a glass holder and chemically strengthened; A, pretreatment: the glass cover plate is cleaned with a neutral cleaning agent or an alkaline cleaning agent, then rinsed with pure water, then cleaned with ultrasonic waves, and finally dried at high temperature; B, primary strengthening: the cleaned glass cover plate is placed in the first mixed molten salt and strengthened at a temperature of 420-440℃ for 4-6h, the strengthened glass is slowly cooled to below 150℃ at a rate of 1-3℃ / min, and then moved to room temperature for cooling; C, secondary strengthening: the cleaned glass cover plate is placed in the second mixed molten salt and strengthened at a temperature of 370-390℃ for 0.5-1.5h, the strengthened glass is slowly cooled to below 150℃ at a rate of 1-3℃ / min, and then moved to room temperature for cooling; (4) Flat grinding: the strengthened glass cover plate is placed in a grinding jig, and then the surface of the glass cover plate is polished; (5) Primary cleaning: the glass cover plate after grinding is placed in a glass holder and cleaned; (6) Screen printing: the cleaned glass cover plate is placed in a screen printing jig, and the printing area of the glass cover plate is screen printed; (7) Secondary cleaning: the screen printed glass cover plate is placed in a glass holder and cleaned.

2. The method of claim 1, wherein the glass cover plate has an ultra-high drop resistance. In step A, the neutral cleaning agent comprises the following raw materials by weight: fatty alcohol polyoxyethylene ether 8-15 parts, alkyl glycoside 5-10 parts, propylene glycol methyl ether 4-8 parts, isopropyl alcohol 2-6 parts, ethylenediaminetetraacetic acid disodium 1-5 parts, benzotriazole 0.01-0.05 parts, 2-amino-2-methyl-1-propanol 0.1-0.3 parts, and deionized water in excess; the alkaline cleaning agent comprises the following raw materials by weight: potassium hydroxide 2-8 parts, monoethanolamine 4-8 parts, fatty alcohol polyoxyethylene ether 6-10 parts, sodium dodecylbenzenesulfonate 1-5 parts, hydroxyethylidene diphosphonic acid 1-2 parts, sodium silicate 0.5-1.5 parts, propylene glycol butyl ether 2-4 parts, and deionized water in excess.

3. The method of claim 1, wherein the glass cover plate has an ultra-high drop resistance. In step B, the first mixed molten salt comprises the following raw materials by weight: potassium nitrate 85-95 parts, sodium nitrate 4-12 parts, and sodium phosphate 1-3 parts.

4. The method of claim 1, wherein the glass cover plate has an ultra-high drop resistance. In step C, the second mixed molten salt comprises the following raw materials by weight: potassium nitrate 96-98 parts, potassium phosphate 0.5-1.5 parts, and potassium chloride 1.5-2.5 parts.

5. The method of claim 1, wherein the glass cover plate has an ultra-high drop resistance. In the step (1), the glass cover plate is a lithium-aluminum silicate glass, which comprises the following components in percentage by weight: 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%, and the sum of the percentages by weight of the above components is 100%.

6. The method of claim 5, wherein the glass cover plate has an ultra-high drop resistance. The components satisfy the following formula: 3.0≤Li2O / (Na2O+K2O)≤5.

5.

7. The method of claim 5, wherein the glass cover plate has an ultra-high drop resistance. The components satisfy the following formula: 6.8%≤MgO+CaO+BaO≤8.2%.

8. The method of claim 5, wherein the glass cover plate has an ultra-high drop resistance. The components satisfy the following formula: 1.2%≤Sb2O3+ZrO2+SnO2≤3.2%.

9. The method of claim 5, wherein the glass cover plate has an ultra-high drop resistance. The RE2O3 is a mixture consisting of Ce2O3, Nd2O3, Gd2O3 and Ho2O3 in a weight ratio of 2-4:1.5-2.5:0.2-0.

6. The glass cover plate is prepared according to the preparation method of any one of claims 1-9.

10. A glass cover plate having ultra-high drop-strength, characterized by: ​

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