Chemically strengthened glass and preparation method therefor

Abstract

The present application relates to the field of materials, in particular to a chemically strengthened glass and a preparation method therefor. The chemically strengthened glass is not prone to cracking caused by bending. Increasing the depth of a compressive stress layer so as to form a compressive stress layer deep in glass enables the glass to be not liable to crack even under large impacts. A method of increasing the surface compressive stress and the depth of compressive stress while reducing the inner tensile stress value enables a better anti-dropping property of the chemically strengthened glass.

Description

Chemically strengthened glass and preparation method thereof Technical Field

[0001] The present application relates to the field of materials, and in particular to a chemically strengthened glass and a preparation method thereof. Background Art

[0002] Chemically strengthened glass is made by contacting the glass with a molten salt containing metal ions, such as alkali metal ions, to cause ion exchange between the metal ions in the glass and the molten salt, thereby forming a compressive stress layer on the glass surface. Mechanical properties are one of the performance indicators of chemically strengthened glass. Improving the mechanical properties of chemically strengthened glass is the technical problem addressed by this application. Summary of the Invention

[0003] The purpose of the embodiments of the present application is to provide a chemically strengthened glass and a preparation method thereof, which aims to improve the problem of low mechanical properties of existing chemically strengthened glass.

[0004] The present embodiment provides a chemically strengthened glass having a thickness of less than or equal to 1500 μm. The chemically strengthened glass has a surface compressive stress value greater than or equal to 900 MPa as measured using an optical waveguide surface stress meter. When the compressive stress value inside the glass is expressed as a variable using a depth from the surface of the chemically strengthened glass, the chemically strengthened glass satisfies the following conditions:

[0005] (I) In the internal compressive stress layer of the chemically strengthened glass, a stress distribution pattern from 0 μm on the surface of the chemically strengthened glass to a depth of 13 μm is Y1, and the average slope of the curve of the stress distribution pattern Y1 is X1; a stress distribution pattern from a depth of 13 μm inside the chemically strengthened glass to a depth DOL where the compressive stress is zero is Y2, and the average slope of the curve of the stress distribution pattern Y2 is X2, and the absolute value range of the ratio X1 / X2 is 0.5 to 1.8.

[0006] (II) Within the depth range of the internal compressive stress layer from 0 μm to 13 μm, the gradient of the stress curve is from ‑17 MPa / μm to ‑36 MPa / μm.

[0007] In other embodiments of the present application, within the depth range of the internal compressive stress layer of 4 μm to 13 μm, the gradient value of the stress curve is ‑20 MPa / μm to ‑28 MPa / μm.

[0008] In other embodiments of the present application, the absolute value range of the above-mentioned X1 / X2 ratio is 0.8~1.6.

[0009] In another embodiment of the present application, the compressive stress value (CS0) of the chemically strengthened glass on the glass surface measured using an optical waveguide surface stress meter is 950 MPa or more, and the thickness t is 1000 μm or less.

[0010] In another embodiment of the present application, the product of the compressive stress value of the portion with a depth of 50 μm from the surface of the chemically strengthened glass and the cube of the thickness t is 28 MPa·mm 3 .

[0011] In other embodiments of the present application, the chemically strengthened glass has a stress curve with a gradient value of -20 MPa / μm to -28 MPa / μm within a depth range of 4 to 13 μm in the internal compressive stress layer.

[0012] The present invention also provides a method for preparing chemically strengthened glass. The method for preparing chemically strengthened glass includes:

[0013] The raw materials include the following components in percentage by weight: SiO2: 58-62%, Al2O3: 14.5-15.6%, Li2O: 2-7%, Na2O: 6-12%, MgO: 5.5-7.8%, ZrO2: 0.5-1.5%; K2O: 0.5-1.5%; Na2SO4: 0.04-1%.

[0014] Then two chemical strengthenings were carried out; NaNO3, Na 2 CO 3 and K 2 CO 3 ; Activated carbon and diatomaceous earth were added during the second chemical strengthening.

[0015] In other embodiments of the present application, the conditions for the first chemical strengthening include: a temperature of 450-460° C. and a time of 1-3 hours.

[0016] In other embodiments of the present application, the conditions for the second chemical strengthening include: a temperature of 410-420° C. and a time of 0.5-1 hour.

[0017] The chemically strengthened glass and its preparation method provided in the embodiments of the present application have at least the following beneficial effects:

[0018] The chemically strengthened glass provided in the embodiments of this application is less susceptible to cracking due to bending. By increasing the depth of the compressive stress layer, a compressive stress layer is formed deep within the glass, making it less susceptible to cracking even under severe impact. This method reduces internal tensile stress while increasing surface compressive stress and compressive stress depth. Chemically strengthened glass exhibits improved drop resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0020] FIG1 is a stress distribution diagram of the chemically strengthened glass provided in an embodiment of the present application in the internal compressive stress layer from 0 μm on the glass surface to a depth of 13 μm.

[0021] FIG2 is a stress distribution diagram of the chemically strengthened glass provided in an embodiment of the present application at a depth DOL where the compressive stress is zero at an internal depth of 13 μm.

[0022] FIG3 is a stress distribution diagram of the chemically strengthened glass provided in Comparative Example 2 in the internal compressive stress layer from 0 μm on the glass surface to a depth of 13 μm.

[0023] FIG4 shows the brightness array line when the wavelength of the light source is 580 nm.

[0024] FIG5 shows the brightness array line when the wavelength of the light source is 610 nm. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0026] The chemically strengthened glass and its preparation method according to the embodiments of the present application are described in detail below. A chemically strengthened glass having a thickness of less than or equal to 1500 μm and a surface compressive stress value of greater than or equal to 900 MPa as measured using an optical waveguide surface stress meter is provided.

[0027] Figure 1 shows the stress distribution in the internal compressive stress layer of chemically strengthened glass provided in an embodiment of the present application, from 0 μm on the glass surface to a depth of 13 μm. The stress curve in Figure 1 represents the stress distribution pattern Y1 in the internal compressive stress layer of chemically strengthened glass, from 0 μm on the glass surface to a depth of 13 μm. The average slope of the curve is X1.

[0028] FIG2 is a stress distribution diagram of the chemically strengthened glass provided in an embodiment of the present application at a depth of 13 μm, where the compressive stress reaches zero. In FIG2 , the stress distribution pattern at the depth of 13 μm, where the compressive stress reaches zero, is Y2.

[0029] The above-mentioned DOL is called depth of layers in English, which represents the depth of the compressive stress layer.

[0030] In other words, the chemically strengthened glass has at least two stress distribution modes, namely Y1 in FIG. 1 and Y2 in FIG. 2 .

[0031] Furthermore, the average slope of the curve of stress distribution mode Y1 is X1, the average slope of the curve of stress distribution mode Y2 is X2, and the absolute value range of the ratio X1 / X2 is 0.5~1.8;

[0032] In the depth range of the internal compressive stress layer from 0 to 13 μm, the gradient value of the stress curve is -17 MPa / μm to -36 MPa / μm.

[0033] For example, in some embodiments, within the depth range of 0 to 13 μm of the internal compressive stress layer, the gradient value of the stress curve may be -17 MPa / μm, -20 MPa / μm, -23 MPa / μm, -25 MPa / μm, -28 MPa / μm, -30 MPa / μm or -36 MPa / μm, etc.

[0034] It's generally believed that increasing the compressive stress on the glass surface can make chemically strengthened glass less susceptible to bending-induced cracking. Furthermore, by increasing the depth of the compressive stress layer, forming a compressive stress layer deep within the glass, it can be made less susceptible to cracking even under high impact. However, when a compressive stress layer forms on the glass surface, a tensile stress layer inevitably forms within the glass. When the internal tensile stress is high, chemically strengthened glass shatters violently upon fracture, easily scattering fragments. Therefore, in the embodiments of this application, a method is employed to increase the surface compressive stress and the compressive stress depth while reducing the internal tensile stress. For a given glass thickness, the central stress of the glass is determined by the area under the stress distribution curve, S, using the relationship: central stress = 2S / (t - 2Dol). The stress distribution pattern indicates that the larger the value of X1 and the smaller the value of X2, the lower the central stress of the glass.

[0035] After the test is completed, the stress of the tempered glass in the depth direction from the surface is calculated based on the arrangement positions of the two groups of brightness array lines of the light waves of different wavelengths transmitted through the compressive stress layer inside the glass.

[0036] In some embodiments, the chemically strengthened glass provided in the embodiments of the present application has better drop resistance when the gradient value of the stress curve is -17 MPa / μm to -36 MPa / μm within the depth range of the internal compressive stress layer of 0 to 13 μm, the gradient value of the stress curve is -20 MPa / μm to -28 MPa / μm within the depth range of the internal compressive stress layer of 4 to 13 μm, and the absolute value of the X1 / X2 ratio is in the range of 0.5 to 1.8.

[0037] Illustratively, the absolute value of the ratio X1 / X2 ranges from 0.5, 0.8, 1, 1.1, 1.3, 1.5, 1.6, or 1.8.

[0038] In some embodiments, if the surface stress is too low, the bending strength and other properties of the glass will deteriorate. If the surface stress is too high, the central stress will increase, which will reduce the drop resistance of the glass. When the product of the compressive stress value of the part with a depth of 50 μm from the surface of the chemically strengthened glass and the cube of the thickness t (CS 50 ×t 3 ) is 28MPa·mm 3 The above features can take into account both glass drop performance and other performance.

[0039] For example, (CS 50 ×t 3 ) is 28MPa·mm 3 , 29MPa·mm 3 、30MPa·mm 3 、32MPa·mm 3 、35MPa·mm 3 , 40MPa·mm 3 wait.

[0040] Among them, the above CS 50 Represents the compressive stress value at a depth of 50 μm from the surface of the chemically strengthened glass. t represents the thickness of the chemically strengthened glass.

[0041] For example, the test method for the light wave transmission surface stress of the chemically strengthened glass is as follows:

[0042] The light wave conversion process from 0μm to a depth of 13μm on the chemically strengthened glass surface is as follows: a light source generator inputs 480nm wavelength light waves through a light wave transmission component into the surface layer of the chemically strengthened glass with a compressive stress layer. After propagating within the glass surface layer, the light waves are emitted through the critical surface of the light wave output component in parallel and perpendicular vibrations, and are converted into brightness array lines due to the refractive index difference.

[0043] The light wave measurement process from 0 μm on the surface of the chemically strengthened glass to a depth of 13 μm is as follows: the two brightness array lines are photographed by an optical precision imaging component, and the arrangement positions of the brightness array lines are precisely measured at the same time.

[0044] The light wave conversion process, from a depth of 13μm inside the chemically strengthened glass to the depth DOL where the compressive stress is zero, uses a light source generator to input a 610nm wavelength light wave through a light wave transmission component into the surface layer of the chemically strengthened glass with a compressive stress layer. After propagating within the glass surface layer, the light wave is emitted through the critical surface of the light wave output component in parallel and perpendicular vibrations, and is converted into brightness array lines due to the refractive index difference.

[0045] The optical wave measurement process from a depth of 13 μm inside the chemically strengthened glass to a depth DOL where the compressive stress is zero is the same as the optical wave measurement process from 0 μm on the surface of the chemically strengthened glass to a depth of 13 μm, and will not be repeated here.

[0046] Typically, two different wavelengths are used, but the position of the bright line on the image sensor varies with each wavelength. The position of the bright line at a given wavelength is determined by factors such as the refractive index of the tempered glass, the rate of change in refractive index due to the ion concentration of the tempered glass, the optical path difference caused by different wavelengths, differences in photoelastic constants, and the refractive index of the prism. These values ​​vary with different wavelengths, so even if light from the light source is incident at the same angle of incidence, the ray trajectories and optical path differences differ, resulting in different conditions for establishing the pattern and causing the bright line to appear at different positions.

[0047] Figures 4 and 5 illustrate the conversion of two brightness array lines due to refractive index differences. Figure 4 shows the brightness array line for a 580nm wavelength light source, while Figure 5 shows the brightness array line for a 610nm wavelength light source. The right ends of the two different wavelength brightness array lines represent the boundary where the brightness changes sharply. This boundary line is generated at a critical angle due to the refractive index difference in chemically strengthened glass. Furthermore, the effective refractive index at this boundary line corresponds to the refractive index of the deep portion of the strengthened glass, where strengthening has not yet reached it. This refractive index is equal to the refractive index of the glass before strengthening.

[0048] The present embodiment provides a method for preparing the chemically strengthened glass. The raw materials for preparing the chemically strengthened glass include the following components, calculated by weight: SiO2: 58-62%, Al2O3: 14.5-15.6%, Li2O: 2-7%, Na2O: 6-12%, MgO: 5.5-7.8%, ZrO2: 0.5-1.5%, K2O: 0.5-1.5%, and Na2SO4: 2-5%.

[0049] SiO2 forms a three-dimensional silicon-oxygen skeleton in glass, and the glass structure is composed of silicon-oxygen tetrahedron (SiO2). 4- As a basic structural unit, it gives the glass good chemical stability, thermal stability, transparency, high softening temperature, hardness and mechanical strength on the one hand, and on the other hand, it is combined with (AlO3) 5- The formation of aluminum-silicon-oxygen anion clusters provides structural support during subsequent chemical strengthening treatments. Low SiO2 content can increase the glass's thermal expansion coefficient, reduce scratch resistance, and lower the glass transition temperature, all of which can affect the effectiveness of subsequent chemical strengthening treatments. High SiO2 content reduces the amounts of other components in the glass. Besides the increased viscosity and difficulty melting caused by SiO2 itself, other glass properties can experience unpredictable changes due to changes in other components, often resulting in reduced performance. The SiO2 content is limited to 58.6% to 61.6%.

[0050] Al2O3 due to Al 3+ The coordination number is not fixed, either 4 or 6, and the structure network is based on aluminum oxide tetrahedron (AlO4) 4- and aluminum oxide octahedron (AlO6) 8- In the presence of alkali metal oxide R2O or alkaline earth metal oxide RO, it is in the form of (AlO3) 5- Exists due to (AlO3) 5- The volume is about 41cm3 / mol, which is smaller than (SiO2) 4- Volume 27.24cm 3 Because Al2O3 has a high content of 1.5% / mol, increasing the Al2O3 content expands the glass's structural network, facilitating ion diffusion and exchange. Al2O3 also stabilizes and resists crystallization, and a higher Al2O3 content increases the glass's high-temperature viscosity. The Al2O3 content is preferably between 13.0% and 16.8%, ensuring good ion exchange capacity without excessively high high-temperature viscosity that would be unsuitable for production. This imparts excellent intrinsic properties to the glass while also providing excellent support for subsequent chemical processing.

[0051] Furthermore, the raw materials also include sulfate, which can increase the redox index of the mixture and achieve chemical decolorization, so that the Fe 3+ The proportion is higher than Fe 2+ At the same time, the amount of sulfate used must be controlled. Sulfate not only has an oxidizing effect, but excessive sulfate will cause an increase in bubbles and corrode the kiln refractory materials.

[0052] Then two chemical strengthenings were carried out; NaNO3, Na 2 CO 3and K 2 CO 3 ; Activated carbon and diatomaceous earth were added during the second chemical strengthening.

[0053] For example, NaNO3, Na 2 CO 3 and K 2 CO 3 Among them, sodium nitrate begins to decompose when heated to above 380℃, and the decomposition product is sodium nitrite. Sodium nitrite is unstable and continues to decompose to produce nitric oxide, nitric oxide and sodium oxide. 2 CO 3 and K 2 CO 3 Reacts with nitrogen oxides to form sodium nitrite and sodium nitrate, releasing CO 2 gas, inhibiting the decomposition of nitrite, thereby reducing Na 2 The effect of O concentration.

[0054] During the second chemical strengthening, activated carbon and diatomaceous earth are added. Activated carbon and diatomaceous earth have an adsorption effect and can absorb impurities.

[0055] For example, the conditions for the first chemical strengthening include: a temperature of 450-460° C. and a time of 1-3 hours. The temperature for the first chemical strengthening is 450° C., 455° C., or 460° C., and the time for the first chemical strengthening is 1 hour, 2 hours, or 3 hours.

[0056] For example, the second chemical strengthening conditions include: a temperature of 410-420° C. and a time of 0.5-1 hour. The second chemical strengthening temperature is 410° C., 415° C., or 420° C. The second chemical strengthening time is 0.5 hour, 1 hour, etc.

[0057] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0058] Examples 1-3, Comparative Examples 1-2

[0059] The raw materials of the chemically strengthened glass in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1. The values ​​in Table 1 represent mass percentages.

[0060] Table 1

[0061]

[0062] The specific preparation process of the glass sheet of the present invention is as follows: the components are mixed according to the proportions in Table 1 above. Simultaneously, the mixed raw materials are charged into a small mixer and mixed uniformly therein. The mixed raw materials are then melted in a small experimental high-temperature kiln. The molten glass is flattened and polished in a small experimental tin bath, then placed in an annealing furnace for precision annealing and cooling, and cut into sheets of glass with a thickness of 0.7 mm.

[0063] Each example was chemically strengthened twice according to Table 2 to obtain a finished product. In Table 2, the primary strengthening salt bath additives accounted for 2% of the total mass of the primary strengthening salt bath. The secondary strengthening salt bath additives accounted for 2% of the total mass of the secondary strengthening salt bath.

[0064] The chemically strengthened glass provided herein was measured using an FSM-6000 to determine a stress distribution pattern Y1 in the internal compressive stress layer, extending from 0 μm on the glass surface to a depth of 13 μm. A second stress distribution pattern was measured using an SLP-2000. An Orihara SLP-2000 stress meter was used to measure a stress distribution pattern Y2 from a depth of 13 μm within the chemically strengthened glass to a depth DOL where the compressive stress is zero. The average slope X1 of the curve for the stress distribution pattern Y1 and the average slope X2 of the curve for the stress distribution pattern Y2 from a depth of 13 μm within the glass to a depth DOL where the compressive stress is zero were calculated. (Based on the cross-sectional compressive stress distribution curve, two straight lines were determined, each taking the starting and ending points of the stress distribution patterns Y1 and Y2, respectively. The slope of these two straight lines was the average slope of X1 and X2.)

[0065] The samples of the embodiment and the comparative example were subjected to a sandpaper drop test using a drop tester to evaluate their drop resistance. The test conditions were: 180-grit sandpaper, 186 g total weight, 30 cm base height, 10 cm increments, 1 time per height until broken.

[0066] Table 2

[0067]

[0068] Figure 1 shows the stress distribution in the internal compressive stress layer of the chemically strengthened glass provided in an embodiment of the present application, from 0 μm on the glass surface to a depth of 13 μm. Figure 2 shows the stress distribution at a depth DOL (deep line) where the compressive stress is zero, from 13 μm on the glass surface. Figure 3 shows the stress distribution in the internal compressive stress layer of the chemically strengthened glass provided in Comparative Example 2, from 0 μm on the glass surface to a depth of 13 μm.

[0069] As can be seen from Table 2, the sandpaper drop height of the chemically strengthened glass provided by Examples 1 to 3 is significantly higher than that of Comparative Examples 1 and 2. The absolute values ​​of the Y1 gradient values ​​of Comparative Examples 1 and 2 are much smaller than those of Examples 1 to 3.

[0070] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A chemically strengthened glass, characterized in that: The thickness of the chemically strengthened glass is less than or equal to 1500 μm; the compressive stress value of the glass surface of the chemically strengthened glass measured by using an optical wave conduction surface stress meter is greater than or equal to 900 MPa; When the compressive stress value inside the chemically strengthened glass is expressed as a variable using the depth from the surface of the chemically strengthened glass as a variable, the chemically strengthened glass satisfies the following: (I) In the internal compressive stress layer of the chemically strengthened glass, the stress distribution mode from 0 μm on the surface of the chemically strengthened glass to a depth of 13 μm is Y1, and the average slope of the curve of the stress distribution mode Y1 is X1; the stress distribution mode from the depth of 13 μm inside the chemically strengthened glass to the depth DOL where the compressive stress is zero is Y2, and the average slope of the curve of the stress distribution mode Y2 is X2, and the absolute value range of the ratio X1 / X2 is 0.5 to 1.8; (II) Within the depth range of the internal compressive stress layer of 0μm~13μm, the gradient value of the stress curve is ‑17MPa / μm~‑36MPa / μm.

2. The chemically strengthened glass according to claim 1, wherein: In the depth range of 4μm~13μm of the internal compressive stress layer, the gradient value of the stress curve is ‑20MPa / μm~‑28MPa / μm.

3. The chemically strengthened glass according to claim 1, wherein: The absolute value range of the X1 / X2 ratio is 0.8~1.

6.

4. The chemically strengthened glass according to claim 1, wherein: The product of the compressive stress value at a depth of 50 μm from the surface of the chemically strengthened glass and the cube of the thickness t is 28 MPa·mm 3 .

5. The chemically strengthened glass according to claim 1, wherein: The chemically strengthened glass has a compressive stress value of 950 MPa or more on a glass surface of the chemically strengthened glass measured using an optical waveguide surface stress meter.

6. The chemically strengthened glass according to claim 1, wherein: Within the depth range of 0 μm to 13 μm of the internal compressive stress layer of the chemically strengthened glass, the gradient value of the stress curve is ‑20 MPa / μm to ‑28 MPa / μm.

7. The chemically strengthened glass according to claim 1, wherein: The chemically strengthened glass includes alkali aluminosilicate glass.

8. A method for preparing chemically strengthened glass, characterized in that: The preparation method of the chemically strengthened glass comprises: the raw materials include the following components in weight percentage: SiO2: 58-62%, Al2O3: 14.5-15.6%, Li2O: 2-7%, Na2O: 6-12%, MgO: 5.5-7.8%, ZrO2: 0.5-1.5%, K2O: 0.5-1.5% and Na2SO4: 0.04-1%; Then two chemical strengthenings were carried out; NaNO3, Na 2 CO 3 and K 2 CO 3 ; Activated carbon and diatomaceous earth were added during the second chemical strengthening.

9. The method for preparing chemically strengthened glass according to claim 8, characterized in that: The conditions of the first chemical strengthening include: The temperature is 450-460°C and the time is 1-3 hours.

10. The method for preparing chemically strengthened glass according to claim 8, characterized in that: The conditions of the second chemical strengthening include: The temperature is 410-420°C and the time is 0.5-1 hour.

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