Flexible glass and methods of making the same

Abstract

This invention discloses a flexible glass and its preparation method. The flexible glass, by weight percentage, is composed of the following raw materials: SiO2 59.5-64%, Al2O3 22-24.8%, P2O5 0.1-2%, ZrO2 0.1-2%, MgO 0.1-2.5%, Na2O 3.5-6.5%, K2O 0-1.1%, Li2O 3.5-4.4%, B2O3 3-4.2%, and ZnO 0.1-0.3%. The preparation method includes melting, forming, chemical thinning, leveling, and chemical strengthening, wherein P2O5 is added to the molten salt used for chemical strengthening. This invention increases the stress layer depth and ion exchange efficiency of the flexible glass by adjusting the Si / O ratio, the proportion of Li2O and P2O5 in the raw material composition, and by adding phosphorus pentoxide during chemical strengthening, thereby improving the flexibility of the glass.

Description

Technical Field

[0001] This invention belongs to the field of flexible glass technology, specifically relating to a flexible glass and its preparation method. Background Technology

[0002] Flexible glass refers to a type of glass that can be bent and possesses flexibility. It has good chemical stability, excellent surface and optical quality, and is lightweight, leading to its increasingly widespread application in flexible displays, OLED lighting, photoelectric conversion, and many other fields in recent years. However, flexible glass is not only a flexible material but also brittle. Due to its extremely low thickness, microcracks and other defects in the glass have a greater impact on its joint strength, making it more prone to breakage than ordinary glass. Therefore, its strength and performance still cannot meet the requirements of most application scenarios.

[0003] Currently, the strength of flexible glass is mainly improved through the following technical solutions: First, by designing the composition, the microstructure of the glass is made more stable, thereby improving the strength of the base glass; second, the processing technology is optimized by using a combination of mechanical grinding and chemical thinning to reduce surface defects in ultra-thin flexible glass and improve surface quality; finally, by using chemical strengthening to increase surface compressive stress on the glass body, it can inhibit the propagation of microcracks on the glass surface, thereby improving the bending strength and impact resistance of flexible glass.

[0004] Chinese patent CN114656142B discloses a flexible glass and its preparation method. The raw materials used in this flexible glass have the following weight ratios: silicon dioxide 60.04–63.01 parts by weight, aluminum oxide 16.7–21.5 parts by weight, boron oxide 12.93–19.85 parts by weight, calcium carbonate 2.43–14.19 parts by weight, magnesium oxide 0.16–2.07 parts by weight, strontium carbonate 0.5–2.74 parts by weight, and barium nitrate 0.12–4.16 parts by weight. The preparation method involves melting the glass and then drawing and cutting it into tubes in a polar atmosphere to obtain the flexible glass. However, it does not contain lithium oxide, has a long chemical tempering time, and the glass forming conditions are quite harsh, requiring a high-quality production environment.

[0005] Chinese patent CN118324427A discloses a chemical strengthening method for ultrathin flexible glass. The method involves first tempering the glass sample, then micro-etching it using HF etching solution, and finally performing a second tempering treatment to obtain ultrathin flexible glass. This method improves the product's appearance while maintaining the tempering stress value, and simplifies the operation process. Compared to traditional tempering methods, it is faster, more efficient, and increases production capacity and product yield. However, the chemical strengthening steps are relatively cumbersome and require a large amount of HF etching solution to complete the chemical thinning.

[0006] Chinese patent CN114262163A discloses a chemical strengthening method for suppressing microcracks on the surface of flexible glass. This method utilizes nano-sized silica, dispersants, and base materials to prepare a transparent thin film material, which is then cured onto the surface of flexible glass using laser evaporation. Finally, chemical strengthening is performed to obtain chemically strengthened flexible glass with a surface coating. This effectively suppresses the generation and propagation of cracks on the glass surface, improves the chemical strengthening efficiency, and increases the glass strength. However, it requires additional coating steps and film materials and cannot increase the depth of chemical strengthening.

[0007] Current technologies primarily use aluminosilicate or lithium aluminosilicate glass as the base glass, but the chemical strengthening capabilities of these two types of glass are limited and still have room for improvement. Furthermore, chemical strengthening using potassium nitrate baths or two-step strengthening using sodium nitrate and potassium nitrate salts has limited effect on increasing the strengthening stress of the finished flexible glass and does not significantly improve its bending performance. Therefore, it is necessary to develop a flexible glass with high chemical strengthening capabilities and optimize the chemical strengthening method to improve the performance of flexible glass. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a flexible glass and its preparation method. By adjusting the Si / O ratio, the proportion of Li2O and P2O5 in the raw material components, and by adding phosphorus pentoxide to the chemically strengthened molten salt, the stress layer depth and ion exchange efficiency of the flexible glass are increased, thereby improving the flexibility of the glass.

[0009] To achieve the above objectives, the present invention provides a flexible glass, which, by weight percentage, is composed of the following raw materials: SiO2 59.5-64%, Al2O3 22-24.8%, P2O5 0.1-2%, ZrO2 0.1-2%, MgO 0.1-2.5%, Na2O 3.5-6.5%, K2O 0-1.1%, Li2O 3.5-4.4%, B2O3 3-4.2%, and ZnO 0.1-0.3%.

[0010] Preferably, the thickness of the flexible glass is ≤0.025mm.

[0011] This invention also provides a method for preparing flexible glass, comprising the following steps:

[0012] (1) Melting: After removing iron from quartz sand, magnesite and zinc ore, they are mixed with each raw material and melted at 1580-1660℃ for 5-8 hours to obtain glass melt;

[0013] (2) Molding: Molten glass is shaped and annealed to prepare precursor glass;

[0014] (3) Chemical thinning: The precursor glass is placed in a chemical thinning solution for thinning treatment to obtain thinned flexible glass;

[0015] (4) Flattening treatment: The thinned flexible glass is cut and flattened;

[0016] (5) Chemical strengthening: After the glass is flattened, it is preheated and then placed in molten salt for chemical strengthening. After slow cooling, flexible glass is obtained.

[0017] Preferably, the annealing temperature in step (2) is 650-670℃ and the annealing time is 30-60min.

[0018] Preferably, the thickness of the precursor glass in step (2) is ≤0.15mm.

[0019] Preferably, the chemical thinning solution in step (3) is prepared by diluting the sulfuric acid solution and mixing it with the hydrofluoric acid solution to obtain the chemical thinning solution.

[0020] More preferably, the sulfuric acid solution has a volume concentration of 50% and a dilution factor of 25 times, and the hydrofluoric acid solution has a volume concentration of 50%; the volume ratio of the sulfuric acid solution to the hydrofluoric acid solution is 1:1.

[0021] Preferably, the molten salt in step (5) is composed of NaNO3, KNO3, and P2O5; the chemical strengthening temperature is 300-400℃ and the time is 10-20min.

[0022] More preferably, the weight percentages of NaNO3, KNO3, and P2O5 are 50:40-45:5-10.

[0023] Preferably, the preheating temperature in step (5) is 300-330℃ and the preheating time is 100-140min; the slow cooling temperature is 350-380℃ and the slow cooling time is 90-120min.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. By controlling the Si / O ratio between 2 and 3.5, the three-dimensional network structure formed by SiO4 tetrahedra connected by bridging oxygen and the three-dimensional network structure formed by non-bridging oxygen bonds in the internal structure of the glass are combined. The presence of bridging oxygen bonds ensures the glass's low coefficient of thermal expansion and good light transmission performance, while the presence of non-bridging oxygen weakens some of the strength of the silicon-oxygen bonds, resulting in a lower melting point and viscosity of the glass, making it easier to mass-produce.

[0026] 2. By adjusting the ratio of Li2O and P2O5 in the flexible glass raw material formulation, the bonding breaking and fluxing effects of Li2O and its ability to form a glass network structure using phosphorus-oxygen tetrahedra [PO4] are controlled. This improves the exchange efficiency and depth of the glass during ion exchange, thus enhancing the chemical strengthening ability of the original high-alumina and lithium aluminum silicon glasses. Simultaneously, the presence of Li2O and P2O5 effectively reduces the coefficient of thermal expansion of the glass, helping to improve its heat resistance and ensuring dimensional stability during subsequent high-temperature processing. Furthermore, Li2O and P2O5 can form microbubbles during high-temperature glass melting, facilitating the removal of bubbles in the molten glass, resulting in greater transparency and purity, and improving the optical transmittance of the finished glass product. P2O5 has hygroscopic and dehydrating properties; the combined use of these two materials effectively prevents excessive reaction between Li2O and moisture in the environment, which could lead to deliquescence and affect the actual amount of lithium oxide introduced into the batch.

[0027] 3. In the chemical strengthening process, sodium nitrate, potassium nitrate and phosphorus pentoxide are mixed in a certain proportion as molten salt, with the content of phosphorus pentoxide maintained between 5-10 wt%, which improves the exchange efficiency of flexible glass in the ion exchange process; at the same time, due to the phosphorus pentoxide doping salt bath, the stress layer depth of the glass can be increased during the strengthening process, and the flexibility of the glass can be improved, thereby enhancing its bending performance.

[0028] 4. Due to the boiling point of phosphorus pentoxide being 360℃, the salt bath temperature was designed to be lower than 360℃. Compared with existing technologies, the lower chemical strengthening temperature can significantly improve the operational safety of the tempering furnace and reduce the energy consumption of the equipment. Detailed Implementation

[0029] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0030] Examples 1-10, Comparative Examples 1-4

[0031] (1) Melting: Quartz sand, magnesite, and smithsonite are cleaned and iron removed, and then mixed with feldspar, heavy soda ash, lithium carbonate, potassium carbonate, zircon and other raw materials in proportion. The mixture is melted at 1580℃ for 8 hours to obtain glass melt; the mixing amount of raw materials is shown in Table 1.

[0032] (2) Forming: The molten glass is formed using a slit-pull process with a forming thickness of 0.15 mm, and then annealed at 650°C for 60 min to obtain the precursor glass;

[0033] (3) Preparation of chemical thinning solution: Take 1L of sulfuric acid with a volume concentration of 50% and pour it into 25L of pure water. Mix thoroughly to obtain mixture A. Then pour mixture A into 1L of hydrofluoric acid with a volume concentration of 50% and mix thoroughly to obtain chemical thinning solution.

[0034] (4) Chemical thinning: The precursor glass is placed in a chemical thinning solution for chemical thinning to obtain a thinned flexible glass with a thickness of 0.025 mm;

[0035] (5) The edges of the flexible glass are thinned by laser cutting and then flattened to obtain a size of 170×140×0.025mm (length×width×thickness).

[0036] (6) Place 10 pieces of thinned flexible glass after flattening into a chemical strengthening fixture, and then place the fixture together with the flexible glass substrate into a chemical strengthening preheating furnace. Preheat at 300°C for 110 min, and then place it in a molten salt of NaNO3 and KNO3 (50wt%:50wt%) after precipitation for 8 h. Chemically strengthen at 350°C for 16 min, and then transfer the fixture together with the flexible glass to a slow cooling furnace. Slowly cool at 360°C for 120 min, and then cool at room temperature to obtain flexible glass.

[0037] Table 1 Formulation of Flexible Glass

[0038]

[0039] Results Testing: The surface stress (CS) and stress layer depth (DOL) of the tempered glass were measured using an FSM-6000LE tempered glass surface stress meter. Data were measured at five locations each at the center and four corners of both surfaces of the sample, and the average value was recorded. The center position of each of the four sides of the two surfaces of the sample was measured using a QVS laser flatness measuring instrument from Jiateng Instruments, and the average value was recorded. The bending radius of the sample was measured using a Keyence IM-8000, and the average value was recorded. In addition, if glass breakage occurred during the tempering process, the breakage rate was recorded.

[0040] Table 2. Effect of formulation on the properties of flexible glass

[0041]

[0042] The results showed that when the mass ratio of Li2O to P2O5 in the raw materials was controlled at 2-3:1, the bond-breaking and fluxing effects of Li2O and the ability of phosphorus-oxygen tetrahedra [PO4] to form a glass network structure could be regulated, thereby improving the exchange efficiency and chemical strengthening depth of the glass body during the chemical strengthening process.

[0043] Examples 11-12, Comparative Examples 5-14

[0044] (1) Melting: Quartz sand, magnesite, and smithsonite are cleaned and iron removed, and then mixed with feldspar, heavy soda ash, lithium carbonate, potassium carbonate, zircon and other raw materials in proportion. The mixture is melted at 1660℃ for 5 hours to obtain glass melt; the amount of raw materials used is the same as in Example 5.

[0045] (2) Forming: The molten glass is formed using a slit-pull process with a forming thickness of 0.15 mm, and then annealed at 670°C for 30 min to obtain the precursor glass;

[0046] (3) Preparation of chemical thinning solution: Take 1L of sulfuric acid with a volume concentration of 50% and pour it into 25L of pure water. Mix thoroughly to obtain mixture A. Then pour mixture A into 1L of hydrofluoric acid with a volume concentration of 50% and mix thoroughly to obtain chemical thinning solution.

[0047] (4) Chemical thinning: The precursor glass is placed in a chemical thinning solution for chemical thinning to obtain a thinned flexible glass with a thickness of 0.025 mm;

[0048] (5) The edges of the flexible glass are thinned by laser cutting and then flattened to obtain a size of 170×140×0.025mm (length×width×thickness).

[0049] (6) Place 10 pieces of thinned flexible glass after flattening into a chemical strengthening fixture, and then place the fixture together with the flexible glass substrate into a chemical strengthening preheating furnace. After preheating, place it in molten salt for chemical strengthening. Then transfer the fixture together with the flexible glass to a slow cooling furnace. After slow cooling, cool to room temperature to obtain flexible glass.

[0050] Table 3 Preheating, Chemical Fortification and Slow Cooling Conditions

[0051]

[0052] Note: Na represents NaNO3, K represents KNO3, P represents P2O5; IOX1 represents the first chemical strengthening, and IOX2 represents the second chemical strengthening.

[0053] Table 4. Effect of preparation conditions on the properties of flexible glass

[0054]

[0055] The results showed that mixing sodium nitrate, potassium nitrate, and phosphorus pentoxide in a certain proportion during chemical strengthening improved the exchange efficiency of flexible glass during the ion exchange process. Because the phosphorus pentoxide-doped salt bath increased the stress layer depth of the glass during strengthening and improved its flexibility, thus enhancing its bending performance. Furthermore, due to the boiling point of phosphorus pentoxide being 360℃, the designed salt bath temperature was lower than 360℃. Compared to existing technologies, this lower chemical strengthening temperature significantly improves the operational safety of the tempering furnace and reduces energy consumption.

Claims

1. A method of making a flexible glass, characterized by: The method comprises the following steps: (1) melting: mixing raw materials, melting at 1580-1660℃ for 5-8h to obtain glass liquid; (2) forming: forming and annealing the glass liquid to prepare precursor glass; (3) chemical thinning: placing the precursor glass in a chemical thinning solution for thinning treatment to obtain flexible glass; (4) flattening treatment: cutting and flattening the flexible glass; (5) chemical strengthening: preheating the flattened glass and then placing it in molten salt for chemical strengthening, and slowly cooling to obtain flexible glass; The molten salt in step (5) is composed of NaNO3, KNO3 and P2O5; the chemical strengthening temperature is 300-400℃, and the time is 10-20min; The flexible glass is composed of the following raw materials in percentage by weight: SiO2 59.5-64%, Al2O3 22-24.8%, P2O5 0.1-2%, ZrO2 0.1-2%, MgO 0.1-2.5%, Na2O 3.5-6.5%, K2O 0-1.1%, Li2O 3.5-4.4%, B2O3 3-4.2%, and ZnO 0.1-0.3%. The weight percentage concentration ratio of NaNO3, KNO3 and P2O5 is 50:40-45:5-10.

2. The method of making a flexible glass of claim 1, wherein: The thickness of the flexible glass is ≤0.025mm.

3. The method of claim 1, wherein: The annealing temperature in step (2) is 650-670℃, and the annealing time is 30-60min.

4. The method of claim 1, wherein: The thickness of the precursor glass in step (2) is ≤0.15mm.

5. The method of claim 1, wherein: The preparation method of the chemical thinning solution in step (3) is as follows: diluting a sulfuric acid solution, mixing with a hydrofluoric acid solution, and then obtaining the chemical thinning solution.

6. The method of claim 5, wherein: The volume concentration of the sulfuric acid solution is 50%, the dilution multiple is 25, and the volume concentration of the hydrofluoric acid solution is 50%; the volume ratio of the sulfuric acid solution to the hydrofluoric acid solution is 1:

1.

7. The method of claim 1, wherein: The preheating temperature in step (5) is 300-330℃, and the preheating time is 100-140min; the slow cooling temperature is 350-380℃, and the slow cooling time is 90-120min.

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