Chemically strengthened UFG glass and preparation method thereof

Abstract

The invention relates to the technical field of ultrathin flexible glass, in particular to chemically strengthened UFG glass and a preparation method thereof. The chemically strengthened UFG glass is prepared from the following raw materials in percentage by mole: 62.0 percent to 68.3 percent of SiO2, 14.2 percent to 17.5 percent of Na2O, 9.21 percent to 13.2 percent of Al2O3, 2 percent to 6 percent of MgO, 1.0 percent to 3.3 percent of B2O3, 0 to 1 percent of P2O5, 0 to 0.85 percent of ZrO2 and 0.05 percent to 0.19 percent of SnO2, wherein the ratio of (Na2O + MgO) / Al2O3 is 1.5 to 2.5, and the ratio of (Na2O + MgO) / (Al2O3 + B2O3) is 1 to 2. The chemically strengthened UFG glass provided by the invention shows excellent performance in the aspects of transmittance, surface hardness, 500,000 times of static bending, drop pen impact and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-thin flexible glass, and in particular to chemically strengthened UFG glass and a preparation method thereof. Background Art

[0002] With the rapid development of the 5G era, single-screen mobile phones can no longer meet the high-end needs of users. Dual-screen and multi-screen mobile phones that are foldable and easy to carry have won the favor of more consumers. In order to protect the flexible screen of foldable mobile phones, cover glass is generally set on its surface to extend the service life of the flexible screen. At present, in addition to the uniform thickness cover glass (UTG), the unequal thickness cover glass (UFG) with its thin middle and thick sides can reduce the local stress concentration when the flexible screen is folded, make the crease smoother, improve durability, and make the screen less prone to damage, scratches, or other external factors such as slight drops that cause functional failure, and the application scenarios are more extensive. However, when UFG glass is strengthened, due to the difference in thickness, the expansion amount of different thickness areas during the strengthening process is large. The strengthened unequal thickness glass cover is distorted and wrinkled, resulting in a low yield rate, which is not conducive to mass production. Summary of the Invention

[0003] The object of the present invention is to provide a chemically strengthened UFG glass, which is used to solve the problem that the chemically strengthened UFG glass in the prior art is prone to distortion and wrinkling.

[0004] The present invention also provides a method for preparing chemically strengthened UFG glass to solve the problem in the prior art that when UFG glass is chemically strengthened, the different expansion amounts of different thickness areas lead to distortion and wrinkling of the strengthened glass cover plates of unequal thickness.

[0005] In order to solve the above problems, the present invention proposes a chemically strengthened UFG glass, and the technical solution adopted is: A chemically strengthened UFG glass comprises, by mole percentage, 62.0% to 68.3% SiO2, 14.2% to 17.5% Na2O, 9.21% to 13.2% Al2O3, 2% to 6% MgO, 1.0% to 3.3% B2O3, 0% to 1% P2O5, 0% to 0.85% ZrO2, and 0.05% to 0.19% SnO2; wherein the ratio of (Na2O+MgO) to (Al2O3) is 1.5 to 2.5, and the ratio of (Na2O+MgO) to (Al2O3+B2O3) is 1 to 2.

[0006] The beneficial effects of the present invention are as follows: in the present invention, SiO2 is the core component of the glass structure and plays the role of the skeleton of the glass structure; Na2O is an alkali metal oxide, which belongs to the outer body of the glass network and can provide "free oxygen" to destroy the network structure, thereby reducing the viscosity and melting temperature of the glass and making the glass structure loose. In addition, Na2O is an important element for ion exchange in chemical strengthening; Al2O3 is a component of the glass network structure, and the aluminum oxide tetrahedron and silicon oxide tetrahedron formed by it interpenetrate into a network structure, thereby improving the strength of the finally formed glass; MgO is an alkaline earth metal oxide, which plays the role of reducing the viscosity of the glass. The invention relates to a novel glass-forming agent comprising a plurality of quartz crystals, a quartz crystal with a quartz crystal structure, and a quartz crystal with a quartz crystal structure. The invention also comprises ...

[0007] In order to make the surface hardness of chemically strengthened UFG glass ≥5.5, the bending radius ≤0.65㎜, and the pen impact height ≥50㎝, preferably, in terms of molar percentage, its raw materials include: 63.18%~65.39% SiO2, 14.9%~15.8% Na2O, 11.1%~12.7% Al2O3, 3.6%~5.2% MgO, 2.0%~2.8% B2O3, 0~1% P2O5, 0~0.67% ZrO2 and 0.05%~0.11% SnO2; wherein (Na2O+MgO) / Al2O3 is 1.58~1.84, and (Na2O+MgO) / (Al2O3+B2O3) is 1.2~1.56.

[0008] In order to make the surface hardness of chemically strengthened UFG glass ≥5.5, the bending radius ≤0.57 mm, and the pen impact height ≥50 cm, preferably, in terms of molar percentage, its raw materials include: 64.72%~65.39% SiO2, 15.7%~15.8% Na2O, 11.1%~12.1% Al2O3, 4%~4.6% MgO, 2% B2O3, 0~1% P2O5, 0~0.25% ZrO2 and 0.08%~0.11% SnO2; among which (Na2O+MgO) / Al2O3 is 1.62~1.84, and (Na2O+MgO) / (Al2O3+B2O3) is 1.3~1.56.

[0009] In order to reduce the distortion, deformation, wrinkling and other phenomena of the chemically strengthened UFG glass, preferably, the chemically strengthened UFG glass includes a first region and a second region, the first region is located at both ends of the chemically strengthened UFG glass, and the second region is located in the middle of the chemically strengthened UFG glass. The thickness of the first region is 60~100μm, and the thickness of the second region is 25~40μm.

[0010] In order to reduce the difference in expansion between regions of different thicknesses during the chemical strengthening process and improve the transmittance, surface hardness, 500,000 static bends, and pen drop impact height of the chemically strengthened UFG glass, preferably, during the chemical strengthening treatment of the UFG glass, the volume expansion rates of the first region and the second region are equal.

[0011] The present invention also proposes a method for preparing chemically strengthened UFG glass, the technical solution adopted is: A method for preparing chemically strengthened UFG glass comprises: mixing, melting, and forming the raw materials in sequence to obtain the UFG glass; and pre-treating, preheating, chemically strengthening, and annealing the UFG glass in sequence to obtain the chemically strengthened UFG glass.

[0012] The beneficial effects of the present invention are as follows: the chemically strengthened UFG glass prepared by the preparation method of the chemically strengthened UFG glass of the present invention exhibits excellent performance in terms of transmittance, surface hardness, 500,000 static bending times and pen impact height, and can improve the appearance quality of flexible glass, increase the overall product yield, and reduce production costs.

[0013] In order to further reduce the difference in expansion of regions of different thicknesses during the chemical strengthening process, preferably, the salt bath used in the chemical strengthening treatment is pure potassium salt, the temperature of the chemical strengthening treatment is 380-460° C., and the time is 5-60 min.

[0014] In order to effectively remove dirt from the surface of UFG glass, improve the surface wettability of UFG glass, and effectively enhance the ion exchange capacity during the chemical strengthening process, preferably, the pretreatment includes: ultrasonically cleaning the UFG glass in sodium hydroxide alkaline solution, oxalic acid and water in sequence; the temperature of the ultrasonic cleaning is 25~60°C and the frequency is 40~120kHz.

[0015] In order to further prevent the difference in expansion between regions of different thicknesses during the chemical strengthening process, preferably, the preheating temperature is 300-400°C.

[0016] In order to reduce defects in the chemically strengthened flexible glass, preferably, the annealing treatment includes: cooling the temperature to 70-150° C. at a cooling rate of 2-10° C. / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic flow chart of a method for preparing chemically strengthened UFG glass according to the present invention; Figure 2 is a schematic cross-sectional view of the chemically strengthened UFG glass of the present invention; In the figure, 1 is the first area, and 2 is the second area. DETAILED DESCRIPTION

[0018] Chemically strengthened UFG glass in the prior art is prone to distortion and wrinkling. The present invention provides a chemically strengthened UFG glass comprising, by molar percentage, 62.0% to 68.3% SiO2, 14.2% to 17.5% Na2O, 9.21% to 13.2% Al2O3, 2% to 6% MgO, 1.0% to 3.3% B2O3, 0% to 1% P2O5, 0% to 0.85% ZrO2, and 0.05% to 0.19% SnO2; wherein the ratio of (Na2O + MgO) to (Al2O3) is 1.5 to 2.5, and the ratio of (Na2O + MgO) to (Al2O3 + B2O3) is 1 to 2.

[0019] The technical concept of the present invention is as follows: In the raw materials used for the UFG glass disclosed in the present invention, SiO2 is a core component forming the glass structure and serves as a skeleton of the glass structure; if its content is too low, the structure of the glass will be weakened; if its content is too high, the melting temperature of the glass will be too high, making it difficult to form, thereby reducing the operability during the quenching process; therefore, the range of SiO2 is 62.0% to 68.3%.

[0020] Na2O is an alkali metal oxide, which belongs to the outer body of the glass network. It can provide "free oxygen" to destroy the network structure, thereby reducing the viscosity and melting temperature of the glass and making the glass structure loose. In addition, Na2O is an important element for ion exchange in chemical strengthening. When the content of Na2O is too high, it will increase the thermal expansion coefficient and reduce the chemical stability. In addition, Na2O is easy to volatilize, resulting in uneven glass composition. When the content of Na2O is too low, it is not conducive to the melting and molding of the glass, as well as the Na2O content. + With K + Therefore, the range of Na2O is 14.2%~17.5%.

[0021] Al2O3 is a component that forms the glass network structure, forming an interpenetrating network of aluminum oxide and silicon oxide tetrahedra. A low content reduces thermal and chemical stability, mechanical strength, and hardness. However, a high content increases the glass's melting temperature, making it difficult to form and, consequently, reducing workability during quenching. Therefore, the Al2O3 content ranges from 9.21% to 13.2%. MgO, an alkaline earth metal oxide, lowers the glass's melting point and improves its chemical stability. It also regulates melt viscosity and fracture toughness. Therefore, the MgO content ranges from 2% to 6%. B2O3 is used to reduce the viscosity of the glass, and can also serve as a flux to help lower the softening point of the obtained glass and adjust the melting viscosity; therefore, the range of B2O3 is 1.0%~3.3%.

[0022] P2O5 makes the glass structure loose, which is beneficial to increasing the ion exchange depth of the glass. Therefore, the range of P2O5 is 0~1%.

[0023] ZrO2 is a network former or intermediate in the base glass, which can significantly reduce the devitrification phenomenon during glass forming and lower the liquidus temperature, and is used to increase the chemical durability and fracture toughness of the glass; therefore, the range of ZrO2 is 0~0.85%.

[0024] SnO2 acts as a clarifier to improve the defoaming ability of glass. Therefore, the range of SnO2 is 0.05%~0.19%.

[0025] (Na2O+MgO) / Al2O3 is 1.5~2.5, and (Na2O+MgO) / (Al2O3+B2O3) is 1~2. By controlling this content range, the strength of the glass is improved, the viscosity and softening point of the glass are reduced, the ion exchange effect in the chemical strengthening process of the glass is improved, the ion exchange rate is increased, and at the same time, the glass melting is improved, making the glass melt faster and easier, thereby increasing the strain point, Young's modulus and elastic modulus of the glass.

[0026] By adjusting the ratios of the aforementioned components, the UFG glass formed during the chemical strengthening process achieves equal volume expansion rates for the first and second regions of unequal thickness. This prevents distortion and wrinkling of the unequally thick cover glass during the folding process, improving product yield and facilitating mass production. Furthermore, the chemically strengthened UFG glass exhibits excellent performance in transmittance, surface hardness, 500,000 static bends, and pen drop impact.

[0027] Specifically, if Figure 1 As shown, the preparation method of chemically strengthened UFG glass includes the following steps: S1. Weighing raw materials, mixing, melting, and forming the raw materials in sequence to obtain UFG glass; S2. Pre-treating, preheating, chemically strengthening, and annealing the UFG glass in sequence to obtain chemically strengthened UFG glass.

[0028] Specifically, the preparation method of chemically strengthened UFG glass includes the following steps: First, the raw material formula is mixed, melted, and formed to obtain UFG glass; Secondly, the UFG glass is pretreated, that is, the UFG glass is ultrasonically cleaned in sodium hydroxide alkaline solution, oxalic acid and water in sequence, wherein the ultrasonic cleaning temperature is 25-60°C and the frequency is 40-120kHz; Next, the pretreated UFG glass is placed in a preheating furnace for preheating, wherein the preheating temperature is 300-400°C; Then, the preheated UFG glass is placed in pure potassium salt for chemical strengthening treatment to obtain chemically strengthened UFG glass; wherein the chemical strengthening treatment temperature is 380-460° C. and the time is 5-60 minutes; Finally, the chemically strengthened UFG glass was cooled to 70-150°C at a cooling rate of 2-10°C / min, and then naturally cooled to room temperature to complete the chemical strengthening and obtain the target glass, namely, chemically strengthened UFG glass.

[0029] The implementation process of the present invention is described in detail below in conjunction with specific embodiments. However, it will be understood by those skilled in the art that the following embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the embodiments. It should be noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0030] In the following examples and comparative examples, the raw materials used are all common commercial products that can be directly purchased or can be prepared according to conventional techniques in the art.

[0031] 1. Example of the method for preparing chemically strengthened UFG glass of the present invention Examples 1-18 Examples 1-18 all provide chemically strengthened UFG glass, wherein the preparation method of the chemically strengthened UFG glass comprises the following steps: First, according to the composition ratios of each component in Table 1 and Table 2, the raw materials corresponding to each component are calculated and weighed, and the raw materials of each component are sequentially mixed, melted, and formed to obtain UFG glass; Secondly, the UFG glass was pretreated, that is, the UFG glass was ultrasonically cleaned in sodium hydroxide alkaline solution, oxalic acid and water in sequence, wherein the ultrasonic cleaning temperature was 25°C and the frequency was 40kHz; Next, the pretreated UFG glass is placed in a preheating furnace for preheating, wherein the preheating temperature is 300°C; Then, the preheated UFG glass is placed in pure KNO3 for chemical strengthening treatment to obtain chemically strengthened UFG glass; Finally, the chemically strengthened UFG glass was cooled to 70°C at a cooling rate of 2°C / min and then naturally cooled to room temperature to complete the chemical strengthening and obtain the target glass, i.e., the chemically strengthened UFG glass.

[0032] The chemical strengthening process in the preparation process of chemically strengthened UFG glass is shown in Tables 3 and 4.

[0033] Table 1 Ratios of the raw materials for chemically strengthened UFG glass in Examples 1-9

[0034] Table 2 Ratios of the raw materials for chemically strengthened UFG glass in Examples 10-18

[0035] Table 3 Chemical strengthening process of chemically strengthened UFG glass of Examples 1-9

[0036] Table 4 Chemical strengthening process of chemically strengthened UFG glass of Examples 10-18

[0037] 2. Experimental Examples Experimental Example 1 The cross section of the chemically strengthened UFG glass prepared in Example 1-18 was tested. Figure 2 As shown, it can be seen that the chemically strengthened UFG glass includes a first region 1 and a second region 2. The first region 1 is located at both ends of the chemically strengthened UFG glass, and the second region 2 is located in the middle of the chemically strengthened UFG glass.

[0038] During the preparation of the chemically strengthened UFG glass of Examples 1-18, the expansion rates of the first region 1 and the second region 2 formed during the chemical strengthening treatment were measured. The expansion rates were calculated based on the volume changes of the first region 1 and the second region 2, where the length and width dimensions of the volume were both calculated as 140 mm × 140 mm. Simultaneously, the thicknesses of the first region 1 and the second region 2 of the prepared chemically strengthened UFG glass were measured. The results are shown in Table 5: Table 5 Expansion ratios of the first and second regions during the preparation of Examples 1-18 and thicknesses of the first and second regions of the obtained chemically strengthened UFG glass

[0039] Table 5 shows that the thickness of the first region 1 is 60-100 μm, and the thickness of the second region 2 is 25-40 μm. During the chemical strengthening process of the UFG glass, the volume expansion rates of the first region 1 and the second region 2 are equal and remain stable during the manufacturing process.

[0040] Experimental Example 2 The chemically strengthened UFG glass obtained in Examples 1-18 above was subjected to relevant performance tests.

[0041] Specifically, transmittance test: Use Analytik Jena SPECORD 50 visible spectrophotometer, place the sample vertically in the spectrophotometer light path, and measure the light transmittance of the sample to air at a wavelength of 550mm. The standard is that the transmittance is not less than 90%, and the product is considered qualified (OK).

[0042] Surface hardness test: pencil hardness test.

[0043] Bending strength test: The Shangzhun universal material testing machine RS-N8000 uses a special fixture to clamp the chemically strengthened UFG glass. The instrument steps forward from top to bottom until the product breaks. The bending radius of the product at the time of crushing is recorded. This is a destructive test. The judgment standard is: if the bending radius is less than 0.7mm and the product does not break, the product is considered qualified (OK); otherwise, the product is considered unqualified (NG).

[0044] Pen drop impact test: Shangzhun SA-8220V fully automatic pen drop impact tester, pen drop weight 8.6g, M&G 0.5mm refill, hollow fixture, test starting from 5cm, raising 1cm each time until breaking, to obtain the final pen drop impact height.

[0045] Static Bending Test: Fix each end of the product's long side to a bending fatigue testing machine. Set the machine's reciprocating frequency to 30 cycles / min. Once the product reaches the bending radius, the moving plate returns to its starting position, completing one bending fatigue test. The test cycle then repeats. The criterion is: if the product survives more than 500,000 static bending cycles without breaking, it is considered acceptable (OK); otherwise, it is considered unacceptable (NG).

[0046] The specific test results are shown in Table 6: Table 6 Performance test results of chemically strengthened UFG glass prepared in Examples 1-18

[0047] As can be seen from Table 6, the transmittance of the chemically strengthened UFG glass of Examples 1-18 of the present application is not less than 90%; the surface hardness is above 5.0H, and can reach a maximum of 5.5H; in the bending strength test, the bending radius of the products is less than 0.7mm, with the lowest being 0.52mm, and the products are qualified (OK); the height of the pen drop impact is above 45cm, and can reach a maximum of 54cm; the chemically strengthened UFG glass prepared in the examples of the present application remains unshattered after being statically bent more than 500,000 times, and the chemically strengthened UFG glass products are qualified (OK).

[0048] This shows that the chemically strengthened UFG glass prepared by the preparation method of chemically strengthened UFG glass provided in this application shows excellent performance in terms of transmittance, bending strength, pen impact, surface hardness, 500,000 static bending times, etc. The chemically strengthened UFG glass is not prone to distortion, deformation, or wrinkles in the folding process of glass covers of unequal thickness, thereby improving the yield rate and facilitating mass production.

[0049] It can effectively improve the strength of flexible glass, which helps to overcome the destructive effect of stress concentration on the glass surface. The strengthened flexible glass has good flexible properties such as bending or folding, and is suitable for the production of flexible screens and related equipment.

[0050] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A chemically strengthened UFG glass, characterized in that: In terms of molar percentage, the raw materials include: 62.0%~68.3%SiO2, 14.2%~17.5%Na2O, 9.21%~13.2%Al2O3, 2%~6%MgO, 1.0%~3.3%B2O3, 0~1%P2O5, 0~0.85%ZrO2 and 0.05%~0.19%SnO2; among which (Na2O+MgO) / Al2O3 is 1.5~2.5, and (Na2O+MgO) / (Al2O3+B2O3) is 1~2.

2. The chemically strengthened UFG glass according to claim 1, wherein In terms of molar percentage, the raw materials include: 63.18%~65.39%SiO2, 14.9%~15.8%Na2O, 11.1%~12.7%Al2O3, 3.6%~5.2%MgO, 2.0%~2.8%B2O3, 0~1%P2O5, 0~0.67%ZrO2 and 0.05%~0.11%SnO2; among which (Na2O+MgO) / Al2O3 is 1.58~1.84, and (Na2O+MgO) / (Al2O3+B2O3) is 1.2~1.

56.

3. The chemically strengthened UFG glass according to claim 1, wherein In terms of molar percentage, the raw materials include: 64.72%~65.39%SiO2, 15.7%~15.8%Na2O, 11.1%~12.1%Al2O3, 4%~4.6%MgO, 2%B2O3, 0~1%P2O5, 0~0.25%ZrO2 and 0.08%~0.11%SnO2; among which (Na2O+MgO) / Al2O3 is 1.62~1.84, and (Na2O+MgO) / (Al2O3+B2O3) is 1.3~1.

56.

4. The chemically strengthened UFG glass according to claim 1, wherein The chemically strengthened UFG glass includes a first region and a second region, wherein the first region is located at both ends of the chemically strengthened UFG glass, and the second region is located in the middle of the chemically strengthened UFG glass. The thickness of the first region is 60-100 μm, and the thickness of the second region is 25-40 μm.

5. The chemically strengthened UFG glass according to claim 4, wherein: During the chemical strengthening process of the UFG glass, the volume expansion rates of the first region and the second region are equal.

6. A method for preparing chemically strengthened UFG glass, characterized in that: The method comprises the following steps: according to the chemically strengthened UFG glass according to any one of claims 1 to 5, sequentially mixing, melting, and forming the raw materials to obtain UFG glass; and sequentially performing pretreatment, preheating, chemical strengthening treatment, and annealing treatment on the UFG glass to obtain chemically strengthened UFG glass.

7. The method for preparing chemically strengthened UFG glass according to claim 6, wherein: The salt bath used in the chemical strengthening treatment is pure potassium salt, the temperature of the chemical strengthening treatment is 380-460° C., and the time is 5-60 minutes.

8. The method for preparing chemically strengthened UFG glass according to claim 6, wherein: The pretreatment comprises: ultrasonically cleaning the UFG glass in sodium hydroxide alkaline solution, oxalic acid and water in sequence; the ultrasonic cleaning temperature is 25-60° C. and the frequency is 40-120 kHz.

9. The method for preparing chemically strengthened UFG glass according to claim 6, wherein: The preheating temperature is 300-400°C.

10. The method for preparing chemically strengthened UFG glass according to claim 6, wherein: The annealing treatment includes: cooling the temperature to 70-150° C. at a cooling rate of 2-10° C. / min.

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