A method of improving surface quality and fracture toughness of flexible glass

Abstract

The application discloses a method for improving surface quality and fracture toughness of flexible glass, and belongs to the technical field of glass preparation. The method comprises the following steps: (a) cleaning and drying a flexible glass substrate; (b) immersing the flexible glass treated in step (a) into a mixed solvent composed of a hydrofluoric acid solution, a sulfuric acid solution, a hydrochloric acid solution and an oxalic acid solution, and performing acid etching treatment at 15-60 DEG C, then taking out and washing with pure water, drying, and then performing heat preservation treatment; (c) placing the flexible glass treated in step (b) into a preheated strengthening solution to perform ion exchange strengthening treatment, and then cooling to room temperature to obtain finished flexible glass. The method can effectively improve the fracture toughness of the flexible glass.

Description

Technical Field

[0001] This invention belongs to the field of glass preparation technology, specifically, it relates to a method for improving the surface quality and fracture toughness of flexible glass. Background Technology

[0002] Flexible glass typically refers to ultra-thin glass with a thickness of no more than 100μm, and it is one of the key basic materials in foldable display devices. Compared with resin-based flexible materials, flexible glass has advantages such as ultra-thinness, wear resistance, high strength, and good bending performance, and is considered an important direction for the development of flexible foldable display technology. With the rapid advancement of flexible foldable electronic devices, the market has placed higher demands on their performance, including good fatigue resistance, high impact resistance, and excellent scratch resistance, to adapt to the increasingly thinner and more portable development trend of electronic products.

[0003] However, flexible glass is still in its developmental stage, and several issues remain regarding its manufacturing process and surface integrity. Due to unavoidable mechanical or thermal stress during production, flexible glass surfaces are prone to defects such as microcracks, which significantly reduce its mechanical strength and bendability. Studies have shown that under external stress, these microcracks are highly susceptible to propagation, potentially leading to overall glass fracture and severely impacting the material's lifespan and reliability.

[0004] Therefore, developing processing techniques that can effectively suppress surface crack propagation and improve fracture toughness is of great technical value for promoting the practical application of flexible glass. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the surface quality and fracture toughness of flexible glass.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for improving the surface quality and fracture toughness of flexible glass includes the following steps: (a) Clean and dry the flexible glass substrate; (b) The flexible glass treated in step (a) is immersed in a mixed solvent consisting of hydrofluoric acid solution, sulfuric acid solution, hydrochloric acid solution and oxalic acid solution, and acid etched at 15-60°C. After that, it is taken out, rinsed with pure water, dried, and then heat-insulated. (c) The flexible glass after the heat preservation treatment in step (b) is placed in the preheating strengthening liquid for ion exchange strengthening treatment, and then cooled to room temperature to obtain the finished flexible glass.

[0007] In a more optimized manner, the mixed solvent, based on a total mass of 100 parts, comprises 1-5 parts hydrofluoric acid solution, 0.5-2 parts sulfuric acid solution, 0.5-2 parts hydrochloric acid solution, 10-20 parts oxalic acid solution, and the remainder being pure water.

[0008] Ideally, the mass fraction of the hydrofluoric acid solution is not less than the sum of the mass fractions of the sulfuric acid solution and the hydrochloric acid solution.

[0009] The optimal process parameters for the heat preservation treatment are: temperature 330-450℃ and time 10-60min.

[0010] Ideally, the temperature of the preheating and strengthening liquid is consistent with the temperature of the heat preservation treatment in step (b).

[0011] Ideally, the ion exchange enhancement treatment should last for 5-15 minutes.

[0012] The beneficial effects of this invention: Macroscopic critical cracks develop from small cracks under cyclic loading. Generally, the sharper the crack tip, the more severe the stress concentration, the easier the crack propagates, leading to a decrease in strength and component fracture. When the surface microstructure of glass is altered (e.g., by acid etching) or when surface-active media are adsorbed, the chemical bonds at the surface crack tip are easily broken, resulting in a decrease in the material's free surface energy and a reduction in crack propagation resistance. However, in dynamic processes, if the newly cracked surface is not promptly eroded by the active medium, its surface energy remains high, and the crack will immediately stop when the propagation force is insufficient.

[0013] Based on the above mechanism, this invention uses a composite acid etching system to controllably passivate microcracks on the surface of flexible glass, effectively mitigating stress concentration at the crack tip and inhibiting its propagation tendency under external force. Furthermore, the activated surface structure formed by acid etching enhances the ion exchange efficiency during subsequent chemical strengthening processes, resulting in a uniform compressive stress layer of a certain depth on the surface, thus constructing a stress gradient structure that is "tight on the outside and tough on the inside." Simultaneously, this process promotes surface layer structure reorganization and densification through temperature control of the acid etching, heat preservation, and strengthening steps. While significantly improving the fracture toughness and fatigue resistance of the glass, it maintains its surface quality and flexibility, demonstrating good process controllability and industrial applicability. Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0015] In the following examples, the concentrations of the hydrofluoric acid solution, sulfuric acid solution, and hydrochloric acid solution in the mixed solvent are 2 mol / L, 3 mol / L, and 3 mol / L, respectively. The preparation process of the strengthening solution is as follows: Accurately weigh 90wt% potassium nitrate, 5wt% potassium carbonate, 4wt% potassium chloride, 0.2wt% cerium nitrate, 0.4wt% diatomaceous earth, and 0.4wt% γ-alumina according to the mass percentage; package the potassium chloride separately, mix the remaining raw materials evenly and add them to the strengthening furnace, start the heating program to 450℃, and during the molten salt heating and melting process, add the potassium chloride evenly into the furnace in 4 batches (each time the addition of potassium chloride must be ensured to be completely melted in the previous addition). After all the materials are added, maintain a constant temperature of 450℃ for melting and maturation for 10-15 minutes to ensure that the components are fully mixed and the ions are evenly distributed to form the strengthening solution.

[0016] Example 1 (a) Clean the flexible glass substrate, remove it, rinse it thoroughly with pure water, and dry it; (b) The flexible glass treated in step (a) is immersed in a mixed solvent and acid-etched at 60°C. The mixed solvent, by weight, comprises 1 part hydrofluoric acid solution, 0.5 parts sulfuric acid solution, 0.5 parts hydrochloric acid solution, 20 parts oxalic acid solution, and 78 parts pure water in a total of 100 parts. After acid etching, the glass is removed, rinsed with pure water, dried, and then heat-treated at 450°C. (c) The flexible glass after the heat preservation treatment in step (b) is placed in the strengthening liquid preheated to 450°C and subjected to ion exchange strengthening treatment for 10 minutes. Then it is cooled to room temperature to obtain the finished flexible glass.

[0017] Example 2 a) Clean the flexible glass substrate, remove it, rinse it thoroughly with pure water, and dry it; (b) The flexible glass treated in step (a) is immersed in a mixed solvent and acid-etched at 40°C. The mixed solvent, by weight, comprises 5 parts hydrofluoric acid solution, 2 parts sulfuric acid solution, 2 parts hydrochloric acid solution, 10 parts oxalic acid solution, and 81 parts pure water in a total of 100 parts. After acid etching, the glass is removed, rinsed with pure water, dried, and then heat-preserved at 380°C. (c) The flexible glass after the heat preservation treatment in step (b) is placed in the strengthening liquid preheated to 380°C and subjected to ion exchange strengthening treatment for 10 minutes. Then it is cooled to room temperature to obtain the finished flexible glass.

[0018] Example 3 (a) Clean the flexible glass substrate, remove it, rinse it thoroughly with pure water, and dry it; (b) The flexible glass treated in step (a) is immersed in a mixed solvent and acid-etched at 15°C. The mixed solvent, by weight, comprises 3 parts hydrofluoric acid solution, 1 part sulfuric acid solution, 1 part hydrochloric acid solution, 15 parts oxalic acid solution, and 80 parts pure water in a total of 100 parts. After acid etching, the glass is removed, rinsed with pure water, dried, and then heat-treated at 330°C. (c) The flexible glass after the heat preservation treatment in step (b) is placed in the strengthening liquid preheated to 330°C and subjected to ion exchange strengthening treatment for 15 minutes. Then it is cooled to room temperature to obtain the finished flexible glass.

[0019] Comparative Example 1 (a) Clean the flexible glass substrate, remove it, rinse it thoroughly with pure water, and dry it; (b) The flexible glass treated in step (a) is immersed in a mixed solvent and acid-etched at 40°C. The mixed solvent, by weight, comprises 10 parts hydrofluoric acid, 4 parts sulfuric acid, 4 parts hydrochloric acid, 15 parts oxalic acid, and 67 parts pure water (the content of hydrofluoric acid, sulfuric acid, and hydrochloric acid are all in excess). After acid etching, the glass is removed, rinsed with pure water, dried, and then heat-treated at 380°C. (c) The flexible glass after the heat preservation treatment in step (b) is placed in the strengthening liquid preheated to 380°C and subjected to ion exchange strengthening treatment for 10 minutes. Then it is cooled to room temperature to obtain the finished flexible glass.

[0020] Comparative Example 2 (a) Clean the flexible glass substrate, remove it, rinse it thoroughly with pure water, and dry it; (b) The flexible glass treated in step (a) is dried directly and then kept at 330°C (the acid etching step is omitted). (c) The flexible glass after the heat preservation treatment in step (b) is placed in the strengthening liquid preheated to 330°C and subjected to ion exchange strengthening treatment for 15 minutes. Then it is cooled to room temperature to obtain the finished flexible glass.

[0021] Testing experiment: (1) The ion exchange depth of the finished glasses obtained in the examples and comparative examples was tested; (2) The surface compressive stress of the finished glass obtained in the examples and comparative examples was tested using a glass surface stress meter; (3) The fracture toughness of the finished glass obtained in the examples and comparative examples was tested using the microindentation method; (4) The surface roughness of the finished glass products obtained in the examples and comparative examples was detected using an atomic force microscope; The obtained data is shown in the table below: Conclusion: The method for improving the surface quality and fracture toughness of flexible glass provided by this invention has significant effects. By using a mixed acid etching system composed of hydrofluoric acid, sulfuric acid, hydrochloric acid, and oxalic acid in specific proportions, and subjecting the flexible glass to controlled acid etching at 15-60℃, surface microcracks can be effectively passivated, stress concentration alleviated, and crack propagation inhibited. The subsequent heat treatment (330-450℃, 10-60 min) combined with ion exchange in a strengthening solution preheated to the same temperature (5-15 min) not only promotes surface densification but also significantly increases the ion exchange depth and surface compressive stress, thereby forming a gradient-distributed compressive stress structure on the glass surface.

[0022] A comparison of the data from the examples and comparative examples shows that the flexible glass treated by the method of the present invention exhibits improved fracture toughness (up to 0.79 MPa). 1 / 2 The method exhibits excellent performance in terms of ion exchange depth (up to 14.5 μm) and surface quality (roughness as low as 0.03 μm), especially outperforming control samples that have not undergone acid etching or have been excessively acid-etched. Through temperature transitions and process coordination between steps, this method achieves a synergistic effect of surface modification, structural strengthening, and toughness enhancement. It possesses good process controllability and industrial applicability, providing reliable technical support for the application of flexible glass in high-end fields such as foldable displays.

[0023] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0024] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for improving the surface quality and fracture toughness of flexible glass, characterized in that... This includes the following steps: (a) Clean and dry the flexible glass substrate; (b) The flexible glass treated in step (a) is immersed in a mixed solvent consisting of hydrofluoric acid solution, sulfuric acid solution, hydrochloric acid solution and oxalic acid solution, and acid etched at 15-60°C. After that, it is taken out, rinsed with pure water, dried, and then heat-insulated. (c) The flexible glass after the heat preservation treatment in step (b) is placed in the preheating strengthening liquid for ion exchange strengthening treatment, and then cooled to room temperature to obtain the finished flexible glass.

2. The method for improving the surface quality and fracture toughness of flexible glass according to claim 1, characterized in that... The mixed solvent, in a total mass of 100 parts, consists of 1-5 parts hydrofluoric acid solution, 0.5-2 parts sulfuric acid solution, 0.5-2 parts hydrochloric acid solution, 10-20 parts oxalic acid solution, and the remainder being pure water.

3. The method for improving the surface quality and fracture toughness of flexible glass according to claim 2, characterized in that... The mass fraction of the hydrofluoric acid solution is not less than the sum of the mass fractions of the sulfuric acid solution and the hydrochloric acid solution.

4. The method for improving the surface quality and fracture toughness of flexible glass according to claim 1, characterized in that... The process parameters for the heat preservation treatment are: temperature 330-450℃ and time 10-60min.

5. The method for improving the surface quality and fracture toughness of flexible glass according to claim 1, characterized in that... The temperature of the preheating and strengthening liquid is consistent with the temperature of the heat preservation treatment in step (b).

6. The method for improving the surface quality and fracture toughness of flexible glass according to claim 1, characterized in that... The ion exchange enhancement treatment time is 5-15 min.

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