Composite strengthening method for improving strength of ultrathin glass

Abstract

The present invention relates to the technical field of glass. Disclosed is a composite strengthening method for improving the strength of ultrathin glass. The method specifically comprises: the following composite strengthening steps for an ultrathin glass cover plate: step 1. cleaning and drying the surfaces of an ultrathin glass cover plate prepared on a production line; and step 2. using ultrafast laser to perform full-surface heat accumulation treatment on the front and back surfaces of ultrathin glass, and naturally cooling the ultrathin glass to microcrystallize the upper and lower surfaces of the glass. By using these steps to strengthen the ultrathin glass cover plate and using laser to induce microcrystallization on the surfaces of the glass before chemical strengthening, the present invention solves inherent deformation and warpage problems caused by conventional physical tempering, and problems such as insufficient strength of the ultrathin glass caused by insufficient degree of ion exchange in single chemical strengthening, ensuring not only the appearance of the ultrathin glass but also the strength and bending performance of the glass.

Description

A composite strengthening method to improve the strength of flexible glass Technical Field

[0001] This invention relates to the field of glass technology, and more specifically to a composite strengthening method for improving the strength of flexible glass. Background Technology

[0002] The development of smart electronic products such as foldable smartphones and flexible wearable devices, as well as curved display technology, has placed higher demands on flexible displays. Flexible glass (UTG) refers to ultra-thin glass with a thickness of ≤0.1mm. It is the core material for foldable display devices, possessing characteristics such as ultra-thinness, wear resistance, high strength, and bendability. However, as display terminal products become increasingly ultra-thin, the thickness of flexible cover glass is also gradually becoming ultra-thin. But ultra-thin glass amplifies the adverse effects of defects on glass strength. Microcracks inevitably exist on the surface of ultra-thin glass. Under service conditions, the fracture toughness and the pre-applied compressive stress on the glass surface begin to expand. When the crack reaches the tensile stress layer, the glass fractures. At this point, the residual stress in the glass is released instantaneously, and the glass rapidly shatters into countless fragments, seriously affecting the safety and durability of the product. Therefore, high strength of ultra-thin flexible glass cover glass is particularly important.

[0003] Glass strengthening methods mainly include physical strengthening and chemical strengthening. Physical strengthening involves reheating the glass to above its sag temperature but below its softening temperature, followed by rapid cooling in a cooling medium, thereby generating compressive stress on the glass surface. However, the overall heating during physical strengthening of thin glass can cause inherent deformation problems, limiting its application in the field of ultra-thin glass strengthening. Chemical strengthening, also known as ion exchange, involves exchanging small-radius alkali metal ions in the glass surface structure with large-radius alkali metal ions in a high-temperature molten salt, generating compressive stress on the glass surface and thus improving its strength. Chemical strengthening requires a lower temperature, only around 400℃, and the internal tensile stress of the glass after ion exchange is small, while the related optical properties remain unchanged, making it more suitable for strengthening ultra-thin glass than physical strengthening. However, the production process and equipment for making flexible glass extremely thin can amplify surface defects, and surface microcracks have a significant impact on the strength of the glass compared to thicker glass. If the degree of ion exchange is insufficient, the glass is prone to breaking into sharp fragments under external force, greatly reducing its service life and safety. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a composite strengthening method for improving the strength of flexible glass, aiming to enhance the strength and safety of flexible glass.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A composite strengthening method for improving the strength of flexible glass includes a flexible glass cover plate, wherein the thickness of the glass substrate is between 10 and 100 μm, and the composite strengthening steps of the flexible glass cover plate are as follows:

[0007] The first step is to clean and dry the surface of the flexible glass cover plate produced on the production line.

[0008] The second step involves using an ultrafast laser to perform full-surface thermal accumulation treatment on both sides of the flexible glass, followed by natural cooling to microcrystallize the upper and lower shallow surfaces of the glass.

[0009] The third step is to preheat the flexible glass cover plate after the laser treatment in the previous step.

[0010] The fourth step is to immerse the preheated flexible glass cover plate in molten salt for chemical strengthening treatment.

[0011] The fifth step is to anneal the chemically strengthened flexible glass cover.

[0012] The sixth step is to clean and dry the molten salt on the annealed flexible glass cover.

[0013] As a further embodiment of the present invention, the flexible glass composition range is: SiO2: 58-64, Al2O3: 12-20, Na2O: 11-15, K2O: 3-6, CaO: 2-4, MgO: 2-6, ZrO2: 0.2-1.5, Li2O: 0-1.2.

[0014] As a further aspect of the present invention: the ultrafast laser is a linear pulsed laser with a pulse width of 230 fs-6 ps, a laser scanning speed of 10 μm / s-200 μm / s, a laser repetition frequency of 200 kHz to 800 kHz, and a laser wavelength of 780 nm to 1000 nm.

[0015] As a further aspect of the present invention: the molten salt used for chemical strengthening is KNO3 or a mixture of NaNO3 and KNO3, with a mixing ratio of KNO3 / NaNO3: 0.1 to 10.

[0016] As a further aspect of the present invention: the preheating temperature of the flexible glass cover is 300-500℃, the preheating temperature of the molten salt is 300-600℃, the chemical strengthening time is 5-180 min, and the annealing temperature is 50-150℃.

[0017] As a further aspect of the present invention: for glass with a thickness of 10-30 nm, only one chemical strengthening treatment is required; for glass with a thickness of 30-100 nm, a second chemical strengthening treatment is required.

[0018] The beneficial effects of this invention are:

[0019] Glass, as an amorphous material, is produced by preventing crystallization of a melt during cooling through rapid cooling and other methods. One of its most important characteristics is metastability. During the transformation from melt to glass, the rapid increase in the viscosity of the melt prevents the atoms or ions within it from arranging themselves in an orderly manner to form crystals, and the latent heat of crystallization cannot be released. Therefore, glass materials generally possess high internal energy, which lies between that of a melt and a crystal. This invention targets the strengthening of ultrathin flexible glass. To address the limitations of traditional thermal tempering methods for ultrathin glass, an ultrafast laser is used to introduce a localized thermal effect, causing relaxation of the glass network structure in the target area. This overcomes the potential barrier required for lattice formation, activates particles in the glass, and promotes their rearrangement, achieving microcrystalline transformation on the glass surface. Furthermore, the depth and intensity of glass strengthening can be adjusted by modifying the pulse width, scanning speed, repetition frequency, and laser wavelength of the pulsed laser.

[0020] The flexible glass cover is strengthened by using the steps described above. Laser-induced microcrystallization of the glass surface is used before chemical strengthening, which solves the inherent deformation and warping problems caused by traditional physical tempering, as well as the problem of insufficient ion exchange caused by insufficient chemical strengthening. This ensures the appearance of the ultra-thin flexible glass while also ensuring the strength and bending performance of the glass. Attached Figure Description

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] Figure 1 shows a schematic diagram of the compressive stress distribution structure on the surface of the composite-reinforced flexible glass cover plate according to an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] Please refer to Figure 1. This invention is a composite strengthening method for improving the strength of flexible glass, comprising the following steps:

[0026] Step 1: Cut the flexible glass cover plate prepared on the production line into glass samples with a size of 140mm*70mm and a thickness of 30um, clean them with ultrasonic waves and then dry them.

[0027] Step 2: A linear femtosecond laser is used to perform a full-surface scan on both sides of the flexible glass. The pulse width is 30 fs, the laser scanning speed is 200 μm / s, the laser repetition frequency is 450 kHz, and the laser wavelength is 800 nm. After scanning, local heat accumulation effects occur on the upper and lower surfaces of the glass. Element migration and chemical bond breaking and recombination occur in the molten area. The upper and lower shallow surfaces of the glass become microcrystalline as it cools naturally.

[0028] Step 3: Insert the flexible glass cover plate after laser treatment in the previous step into the strengthening frame and preheat it at 400℃ for 0.5 hours. Heat the molten salt with a KNO3 / NaNO3 ratio of 0.25 to 420℃ to make it completely melted and clear and homogeneous.

[0029] Step 4: Quickly insert the preheated glass slide into the homogeneous molten salt for chemical strengthening. After holding at 420℃ for 30 minutes, remove the sample.

[0030] Step 5: Place the glass slide and the strengthening frame together in a muffle furnace at 100°C for annealing for 1 hour. Finally, wash the molten salt on the flexible glass cover with running water and dry it in a drying oven to obtain sample I.

[0031] Example 2

[0032] Step 1: Cut the flexible glass cover plate prepared on the production line into glass samples with a size of 140mm*70mm and a thickness of 30um, clean them with ultrasonic waves and then dry them.

[0033] Step 2: Insert the cleaned flexible glass cover into the reinforced frame and preheat it at 400℃ for 0.5 hours. Heat the molten salt with a KNO3 / NaNO3 ratio of 0.25 to 420℃ to completely melt it and make it clear and homogeneous.

[0034] Step 3: Quickly insert the preheated glass slide into the homogeneous molten salt for chemical strengthening. After holding at 420℃ for 30 minutes, remove the sample.

[0035] Step 4: Place the glass plate and the strengthening frame together in a muffle furnace at 100°C for annealing for 1 hour. Finally, rinse the molten salt on the flexible glass cover with running water and dry it in a drying oven.

[0036] Step 5: Preheat the dried glass slides at 400℃ for 0.5 hours, and heat the molten salt with a KNO3 / NaNO3 ratio of 4 to 420℃ to completely melt and make it clear and uniform.

[0037] Step 6: Quickly insert the preheated glass slide into the homogeneous molten salt for secondary chemical strengthening. After holding at 420℃ for 10 minutes, remove the sample.

[0038] Step 7: Place the glass slide after secondary chemical strengthening, along with the strengthening frame, into a muffle furnace at 100°C for annealing for 1 hour. Finally, rinse the molten salt on the flexible glass cover with running water and dry it in a drying oven to obtain Sample II.

[0039] Example 3

[0040] Step 1: Cut the flexible glass cover plate prepared on the production line into glass samples with a size of 140mm*70mm and a thickness of 100um, clean them with ultrasonic waves and then dry them.

[0041] Step 2: A linear femtosecond laser is used to perform a full surface scan on both sides of the flexible glass. The pulse width is 10 fs, the laser scanning speed is 200 μm / s, the laser repetition frequency is 400 kHz, and the laser wavelength is 980 nm. After scanning, local heat accumulation effects occur on the upper and lower surfaces of the glass. Element migration and chemical bond breaking and recombination occur in the molten area. The upper and lower shallow surfaces of the glass become microcrystalline as it cools naturally.

[0042] Step 3: Insert the flexible glass cover plate after laser treatment in the previous step into the strengthening frame and preheat it at 400℃ for 0.5 hours. Heat the molten salt with a KNO3 / NaNO3 ratio of 0.25 to 420℃ to make it completely melted and clear and homogeneous.

[0043] Step 4: Quickly insert the preheated glass slide into the homogeneous molten salt for chemical strengthening. After holding at 420℃ for 30 minutes, remove the sample.

[0044] Step 5: Place the glass plate and the strengthening frame together in a muffle furnace at 100°C for annealing for 1 hour. Finally, rinse the molten salt on the flexible glass cover with running water and dry it in a drying oven.

[0045] Step 6: Preheat the dried glass slides at 400℃ for 0.5 hours, and heat the molten salt with a KNO3 / NaNO3 ratio of 4 to 420℃ to completely melt and make it clear and uniform.

[0046] Step 7: Quickly insert the preheated glass slide into the homogeneous molten salt for secondary chemical strengthening. After holding at 420℃ for 30 minutes, remove the sample.

[0047] Step 8: Place the glass slide after secondary chemical strengthening, along with the strengthening frame, into a muffle furnace at 100°C for annealing for 1 hour. Finally, wash the molten salt on the flexible glass cover with running water and dry it in a drying oven to obtain Sample III.

[0048] As shown in Figure 1, due to the different thicknesses of the original sheets of Sample I and Sample III, the embodiments respectively employed primary and secondary chemical strengthening steps. The strengthened glass exhibited higher surface compressive stress and strengthening stress depth, resulting in excellent drop resistance. Furthermore, compared to Sample II, the flexible glass of Samples I and III underwent femtosecond laser thermal excitation crystallization followed by chemical strengthening. This chemical strengthening process resulted in higher ion exchange efficiency, which is more conducive to increasing the surface compressive stress and strengthening stress depth, while also reducing the rate of change in compressive stress value. This better resists central tensile stress and crack propagation, ensuring both the appearance of the ultra-thin flexible glass and its strength and bending performance.

[0049] Sample II, however, did not undergo femtosecond laser thermal excitation but only underwent secondary chemical strengthening. The excessive rate of change in surface compressive stress value easily caused warping and surface unevenness in the flexible glass. If only one chemical strengthening was performed, it would result in problems such as excessively low surface compressive stress value and insufficient tempering.

[0050] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A composite strengthening method for improving the strength of flexible glass, comprising a flexible glass cover plate, the glass substrate thickness is between 10-100 um, characterized in that, The composite reinforcement steps of the flexible glass cover are as follows: The first step is to clean and dry the surface of the flexible glass cover plate produced on the production line. The second step involves using an ultrafast laser to perform full-surface thermal accumulation treatment on both sides of the flexible glass, followed by natural cooling to microcrystallize the upper and lower shallow surfaces of the glass. The third step is to preheat the flexible glass cover plate after the laser treatment in the previous step. The fourth step is to immerse the preheated flexible glass cover plate in molten salt for chemical strengthening treatment. The fifth step is to anneal the chemically strengthened flexible glass cover. The sixth step is to clean and dry the molten salt on the annealed flexible glass cover.

2. The method of claim 1, wherein the method further comprises, The composition range of the flexible glass is: SiO2: 58-64, Al2O3: 12-20, Na2O: 11-15, K2O: 3-6, CaO: 2-4, MgO: 2-6, ZrO2: 0.2-1.5, Li2O: 0-1.

2.

3. The method of claim 1, wherein the method further comprises, The ultrafast laser is a linear pulsed laser with a pulse width of 230 fs-6 ps, a laser scanning speed of 10 μm / s-200 μm / s, a laser repetition frequency of 200 kHz to 800 kHz, and a laser wavelength of 780 nm to 1000 nm.

4. The method of claim 1, wherein the method further comprises, The molten salt used for chemical strengthening is KNO3 or a mixture of NaNO3 and KNO3, with a mixing ratio of KNO3 / NaNO3: 0.1 to 10.

5. The method of claim 1, wherein the method further comprises, The flexible glass cover is preheated at 300–500°C, the molten salt is preheated at 300–600°C, the chemical strengthening time is 5–180 min, and the annealing temperature is 50–150°C.

6. The method of claim 1, wherein the method further comprises, The glass with a thickness of 10-30 nm only requires one chemical strengthening treatment, while the glass with a thickness of 30-100 nm requires two chemical strengthening treatments.

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