Strengthened glass sheet, method for manufacturing strengthened glass sheet, and glass sheet for strengthening

Abstract

The strengthened glass sheet of the present application is a strengthened glass sheet having a compressive stress layer on a surface, characterized in that, as a glass composition, it contains, in terms of mol%, SiO2 40 to 80%, Al2O3 6 to 25%, B2O3 0 to 10%, Li2O 3 to 15%, Na2O 1 to 21%, K2O 0 to 10%, MgO 0 to 10%, ZnO 0 to 10%, P2O5 0 to 15%, SnO2 0.001 to 0.30%, ([Li2O] + [Na2O] + [K2O]) / [Al2O3] ≥ 0.86, and ([SiO2] + [B2O3] + [P2O5]) / ((100 x [SnO2]) x ([Al2O3] + [Li2O] + [Na2O] + [K2O] + [MgO] + [CaO] + [SrO] + [BaO] + [ZnO])) ≥ 0.40.

Description

Technical Field

[0001] This invention relates to a reinforced glass plate, a method for manufacturing a reinforced glass plate, and a reinforced glass plate for use, and more particularly to a reinforced glass plate suitable for cover glass of touch panel displays for mobile phones, digital cameras, PDAs (portable terminals), etc., a method for manufacturing a reinforced glass plate, and a reinforced glass plate for use. Background Technology

[0002] In applications such as mobile phones, digital cameras, and PDAs (portable terminals), the cover glass used as a touch panel display is made of ion-exchange treated tempered glass (see Patent Document 1 and Non-Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-83045

[0006] Patent Document 2: Japanese Patent Publication No. 2016-524581

[0007] Patent Document 3: Japanese Patent Publication No. 2011-510903

[0008] Non-patent literature

[0009] Non-patent literature 1: Tetsuro Izumiya et al., Novel Glasses and Their Properties, First Edition, Management Systems Research Institute, Co., Ltd., August 20, 1984, pp. 451-498 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, if a smartphone is accidentally dropped on the ground, the cover glass may break, rendering the smartphone unusable. To avoid this, increasing the strength of the tempered glass becomes important.

[0012] Increasing the stress depth is a useful method to improve the strength of tempered glass. Specifically, if a smartphone is dropped and the cover glass impacts the road surface, protrusions or sand particles from the road can penetrate the cover glass and reach the tensile stress layer, leading to breakage. Therefore, by increasing the stress depth of the compressive stress layer, protrusions or sand particles from the road surface are less likely to reach the tensile stress layer, thus reducing the probability of cover glass breakage.

[0013] Lithium aluminum silicate glass is advantageous in achieving deep stress depths. In particular, by impregnating a strengthening glass plate containing lithium aluminum silicate glass in a molten salt containing NaNO3, ion exchange occurs between the Li ions in the glass and the Na ions in the molten salt, resulting in a strengthening glass plate with a deeper stress depth.

[0014] However, for conventional lithium aluminosilicate glasses, the compressive stress value of the compressive stress layer may become too low. On the other hand, if the glass composition is designed to increase the compressive stress value of the compressive stress layer, the chemical stability may decrease.

[0015] Furthermore, conventional lithium aluminosilicate glasses suffer from insufficient clarification, potentially leaving air bubbles in the glass during sheet forming. On the other hand, if tin oxide (SnO2) is introduced into the glass composition as a clarifier to reduce air bubbles, devitrifying SnO2 bumps may form, making sheet forming difficult.

[0016] The present invention was made in view of the above circumstances. Its technical problem is to provide a reinforced glass plate that is difficult to break when dropped, has excellent chemical stability and clarity, and is difficult to produce devitrifying bumps during forming.

[0017] means for solving problems

[0018] The inventors, through various studies, discovered that the aforementioned technical problems can be solved by limiting the glass composition within a specified range, and thus proposed this invention. Specifically, the reinforced glass sheet of this invention is a reinforced glass sheet with a compressive stress layer on its surface, characterized in that, as a glass composition, it contains, in molar percentages, 40-80% SiO2, 6-25% Al2O3, 0-10% B2O3, 3-15% Li2O, 1-21% Na2O, 0-10% K2O, 0-10% MgO, 0-10% ZnO, 0-15% P2O5, and 0-15% SnO2. The content is 0.001–0.30%, ([Li₂O]+[Na₂O]+[K₂O]) / [Al₂O₃]≥0.86, and ([SiO₂]+[B₂O₃]+[P₂O₅]) / ((100×[SnO₂])×([Al₂O₃]+[Li₂O]+[Na₂O]+[K₂O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40. Here, [Li₂O] refers to the molar percentage content of Li₂O. [Na₂O] refers to the molar percentage content of Na₂O. [K₂O] refers to the molar percentage content of K₂O. [Al₂O₃] refers to the molar percentage content of Al₂O₃. ([Li₂O]+[Na₂O]+[K₂O]) / [Al₂O₃] refers to the value of dividing the total amount of Li₂O, Na₂O, and K₂O by the content of Al₂O₃. [SiO₂] refers to the molar percentage content of SiO₂. [B₂O₃] refers to the molar percentage content of B₂O₃. [P₂O₅] refers to the molar percentage content of P₂O₅. [SnO₂] refers to the molar percentage content of SnO₂. [MgO] refers to the molar percentage content of MgO. [CaO] refers to the molar percentage content of CaO. [SrO] refers to the molar percentage content of SrO. [BaO] refers to the molar percentage content of BaO. [ZnO] refers to the molar percentage content of ZnO. ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO])) refers to the value obtained by multiplying the total amount of SiO2, B2O3, and P2O5 by the content of SnO2 (100 times the content of SnO2) by the total amount of Al2O3, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, and ZnO, and then dividing the result by the total amount of SnO2.

[0019] In addition, the B2O3 content of the reinforced glass plate of the present invention is preferably 0.1 to 3 mol.

[0020] In addition, the SnO2 content of the reinforced glass plate of the present invention is preferably 0.045 mol% or less.

[0021] In addition, the content of Cl in the reinforced glass plate of the present invention is preferably 0.02 to 0.3 mol.

[0022] The reinforced glass plate of the present invention is a reinforced glass plate having a compressive stress layer on its surface. Its characteristic is that, as a glass composition, it contains, in molar percentages: SiO2 40-80%, Al2O3 6-25%, B2O3 0-10%, Li2O 3-15%, Na2O 1-21%, K2O 0-10%, MgO 0-10%, ZnO 0-10%, P2O5 0-15%, SnO2 0.001-0.045%, Cl... 0.02~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100 ×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40.

[0023] The reinforced glass plate of the present invention is a reinforced glass plate having a compressive stress layer on its surface. Its characteristic is that, as a glass composition, it contains, in molar percentages: SiO2 40-80%, Al2O3 6-25%, B2O3 0.1-3%, Li2O 3-15%, Na2O 1-21%, K2O 0-10%, MgO 0-10%, ZnO 0-10%, P2O5 0-15%, SnO2 0.001-0.30%, Cl... 0.02~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100 ×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40.

[0024] In addition, the reinforced glass plate of the present invention preferably has a P2O5 content of 2.5 mol% or more.

[0025] In addition, the Fe2O3 content of the reinforced glass plate of the present invention is preferably 0.001 to 0.1 mol.

[0026] In addition, the TiO2 content of the reinforced glass plate of the present invention is preferably 0.001 to 0.1 mol.

[0027] Furthermore, the compressive stress value of the outermost surface of the reinforced glass plate of the present invention is preferably 200 to 1200 MPa. Here, "compressive stress value of the outermost surface" and "stress depth" refer to values ​​measured, for example, by observing a phase difference distribution curve using a scattered light photoelastic stress meter SLP-1000 (manufactured by Orihara Corporation). Stress depth refers to the depth at which the stress value becomes zero. It should be noted that when calculating the stress characteristics, the refractive index of each measured sample was set to 1.51, and the optical elastic constant was set to 29.0 [(nm / cm) / MPa].

[0028] In addition, the stress depth of the compressive stress layer in the reinforced glass plate of the present invention is preferably 50 to 200 μm.

[0029] Furthermore, the compressive stress at a depth of 2.5 μm in the reinforced glass plate of the present invention is preferably 350 MPa or higher. This results in higher flexural strength.

[0030] Furthermore, the reinforced glass plate of the present invention preferably has an average compressive stress of 85 MPa or more at a depth of 30–45 μm. This results in higher drop strength.

[0031] Furthermore, the reinforced glass plate of the present invention preferably has a high-temperature viscosity of 10. 2.5 The temperature at dPa·s is below 1650℃. Here, "high-temperature viscosity 10" is used. 2.5 The temperature at dPa·s can be determined using, for example, the platinum ball pulling method.

[0032] Furthermore, the reinforced glass sheet of the present invention preferably has an overflow confluence surface at the center in the thickness direction. Here, the "overflow pull-down method" is a method of manufacturing a glass sheet by causing molten glass to overflow from both sides of the refractory body, confluencing the overflowing molten glass at the lower end of the refractory body, and then pulling it downward to form the sheet.

[0033] Furthermore, the reinforced glass plate of the present invention is preferably used as a cover glass for a touch panel display.

[0034] In addition, the stress distribution curve of the reinforced glass plate of the present invention preferably has at least a first peak, a second peak, a first valley, and a second valley in the thickness direction.

[0035] The manufacturing method of the reinforced glass plate of the present invention is characterized by comprising: preparing a glass composition containing, in molar percentage, 40-80% SiO2, 6-25% Al2O3, 0-10% B2O3, 3-15% Li2O, 1-21% Na2O, 0-10% K2O, 0-10% MgO, 0-10% ZnO, 0-15% P2O5, and 0-15% SnO2. The preparation process of a strengthening glass plate with a content of 0.001 to 0.30%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40; and the ion exchange process of subjecting the strengthening glass plate to multiple ion exchange treatments to obtain a strengthening glass plate with a compressive stress layer on its surface.

[0036] The strengthening glass plate of the present invention is a strengthening glass plate capable of ion exchange, characterized in that, as a glass composition, it contains, in molar percentage, 40-80% SiO2, 6-25% Al2O3, 0-10% B2O3, 3-15% Li2O, 1-21% Na2O, 0-10% K2O, 0-10% MgO, 0-10% ZnO, 0-15% P2O5, and 0-15% SnO2. 0.001~0.30%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((10 0×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40.

[0037] The strengthening glass plate of the present invention is a strengthening glass plate capable of ion exchange, characterized in that, as a glass composition, it contains, in molar percentage, 40-80% SiO2, 6-25% Al2O3, 0-10% B2O3, 3-15% Li2O, 1-21% Na2O, 0-10% K2O, 0-10% MgO, 0-10% ZnO, 0-15% P2O5, 0.001-0.045% SnO2, and Cl. 0.02~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100 ×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40.

[0038] The strengthening glass plate of the present invention is a strengthening glass plate capable of ion exchange, characterized in that, as a glass composition, it contains, in molar percentages, 40-80% SiO2, 6-25% Al2O3, 0.1-3% B2O3, 3-15% Li2O, 1-21% Na2O, 0-10% K2O, 0-10% MgO, 0-10% ZnO, 0-15% P2O5, 0.001-0.30% SnO2, and Cl. 0.02~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100 ×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40. Attached Figure Description

[0039] Figure 1 This is an illustrative diagram showing the stress distribution curves with the first peak, the second peak, the first valley, and the second valley.

[0040] Figure 2 This is the stress distribution curve of the reinforced glass plate involved in Example 3.

[0041] Figure 3 This is the stress distribution curve of the reinforced glass plate involved in Example 3. Detailed Implementation

[0042] The reinforced glass plate (reinforced glass plate) of the present invention is a reinforced glass plate having a compressive stress layer on its surface. Its characteristic is that, as a glass composition, it contains, in molar percentages, 40-80% SiO2, 6-25% Al2O3, 0-10% B2O3, 3-15% Li2O, 1-21% Na2O, 0-10% K2O, 0-10% MgO, 0-10% ZnO, 0-15% P2O5, and 0-15% SnO2. 0.001~0.30%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40. The reasons for limiting the content range of each component are shown below. It should be noted that, unless otherwise specified, the % expression in the description of the content range of each component refers to moles.

[0043] SiO2 is a component that forms the network of glass. If the SiO2 content is too low, vitrification becomes difficult, and the coefficient of thermal expansion becomes too high, easily reducing thermal shock resistance. Therefore, the suitable lower limit range for SiO2 is 40% or higher, 45% or higher, 50% or higher, 55% or higher, 57% or higher, and especially 59% or higher. On the other hand, if the SiO2 content is too high, meltability and formability easily decrease, and the coefficient of thermal expansion becomes too low, making it difficult to match with the coefficient of thermal expansion of the surrounding materials. Therefore, the suitable upper limit range for SiO2 is 80% or lower, 70% or lower, 68% or lower, 66% or lower, 65% or lower, 64.5% or lower, 64% or lower, 63% or lower, and especially 62% or lower.

[0044] Al₂O₃ is a component that improves ion exchange performance, as well as strain point, Young's modulus, fracture toughness, and Vickers hardness. Therefore, the suitable lower limit range for Al₂O₃ is 6% or higher, 7% or higher, 8% or higher, 10% or higher, 12% or higher, 13% or higher, 14% or higher, 14.4% or higher, 15% or higher, 15.3% or higher, 15.6% or higher, 16% or higher, 16.5% or higher, 17% or higher, 17.2% or higher, 17.5% or higher, 17.8% or higher, 18% or higher, exceeding 18%, exceeding 18.3%, and especially exceeding 18.5%, 18.6%, 18.7%, and 18.8%. On the other hand, if the Al₂O₃ content is too high, the high-temperature viscosity increases, and the meltability and formability tend to decrease. Furthermore, devitrification crystals in the glass become more likely to precipitate, making it difficult to form into sheet shapes using methods such as overflow drawing. Especially when using alumina-based refractories as the shaped refractories and forming them into plates using the overflow pull-down method, spinel devitrification crystals easily precipitate at the interface with the alumina-based refractories. Furthermore, acid resistance is reduced, making it unsuitable for acid treatment processes. Therefore, the suitable upper limits for Al2O3 are below 25%, below 21%, below 20.5%, below 20%, below 19.9%, below 19.5%, below 19.0%, and particularly below 18.9%. If the content of Al2O3, which has a significant impact on ion exchange performance, is set within a suitable range, a distribution curve with a first peak, a second peak, a first valley, and a second valley is easily formed.

[0045] B₂O₃ reduces high-temperature viscosity and density, stabilizes glass, hinders crystallization, and lowers the liquidus temperature. It also increases the binding force of oxygen electrons based on cations and reduces the basicity of the glass. If the B₂O₃ content is too low, the stress depth in the ion exchange between Li ions in the glass and Na ions in the molten salt becomes too deep, resulting in a lower compressive stress value (CS) of the compressive stress layer. Na The basicity of B2O3 can easily decrease. Additionally, the glass may become unstable, reducing its devitrification resistance. Furthermore, the basicity of the glass may become too high, reducing the amount of O2 released from the clarifier reaction, decreasing foaming properties, and leaving residual bubbles in the glass during sheet forming. Therefore, the suitable lower limit range for B2O3 is 0% or more, 0.10% or more, 0.12% or more, 0.15% or more, 0.18% or more, 0.20% or more, 0.23% or more, 0.25% or more, 0.27% or more, 0.30% or more, 0.35% or more, and especially 0.4% or more. On the other hand, if the B2O3 content is too high, the stress depth may become shallower. In particular, the efficiency of ion exchange between Na ions in the glass and K ions in the molten salt becomes more easily reduced, decreasing the stress depth (DOL_ZERO) of the compressive stress layer. KThe content of B2O3 tends to decrease. Therefore, the suitable upper limits for B2O3 are below 10%, below 5%, below 4%, below 3.8%, below 3.5%, below 3.3%, below 3.2%, below 3.1%, below 3%, below 2.9%, below 2.8%, below 2.5%, below 2.0%, below 1.5%, below 1.0%, below 1.0%, below 0.8%, and especially below 0.5%. If the content of B2O3 is set within a suitable range, a distribution curve with a first peak, a second peak, a first trough, and a second trough is easily formed.

[0046] Alkali metal oxides are ion-exchange components that reduce viscosity at high temperatures and improve meltability and formability. However, if the content of alkali metal oxides ([Li₂O] + [Na₂O] + [K₂O]) is too high, the coefficient of thermal expansion may increase. Additionally, acid resistance may decrease. Therefore, the suitable lower limit range for alkali metal oxides ([Li₂O] + [Na₂O] + [K₂O]) is 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 14.2% or more, 14.5% or more, 14.8% or more, 15% or more, 15.2% or more, 15.5% or more, 15.8% or more, especially 16% or more; and the suitable upper limit range is 25% or less, 23% or less, 20% or less, 19% or less, especially 18% or less.

[0047] Li₂O is an ion-exchange component, particularly essential for achieving deep stress depth by exchanging Li ions in the glass with Na ions in the molten salt. Additionally, Li₂O reduces high-temperature viscosity, improves melt flow and formability, and increases Young's modulus. Therefore, the suitable lower limit range for Li₂O is 3% or more, 4% or more, 5% or more, 5.5% or more, 6.5% or more, 7% or more, 7.3% or more, 7.5% or more, 7.8% or more, and especially 8% or more. Conversely, the suitable upper limit range for Li₂O is 15% or less, 13% or less, 12% or less, 11.5% or less, 11% or less, 10.5% or less, less than 10%, 9.9% or less, 9% or less, and especially 8.9% or less.

[0048] Na₂O is an ion-exchange component, and also a component that reduces high-temperature viscosity and improves melt flow and formability. Furthermore, Na₂O improves devitrification resistance, particularly inhibiting devitrification during reactions with alumina-based refractories. Therefore, the suitable lower limit range for Na₂O is 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 7.5% or more, 8% or more, 8.5% or more, 8.8% or more, and especially 9% or more. On the other hand, if the Na₂O content is too high, the coefficient of thermal expansion becomes excessively high, and thermal shock resistance is easily reduced. Additionally, an imbalance in the glass composition can sometimes reduce devitrification resistance. Therefore, the suitable upper limit range for Na₂O is 21% or less, 20% or less, 19% or less, especially 18% or less, 15% or less, 13% or less, 11% or less, and especially 10% or less.

[0049] K₂O is a component that reduces viscosity at high temperatures and improves melt flow and formability. However, if the K₂O content is too high, the coefficient of thermal expansion becomes too high, and the thermal shock resistance is easily reduced. Additionally, the compressive stress value of the outermost surface tends to decrease. Therefore, the suitable upper limit range for K₂O is below 10%, below 7%, below 6%, below 5%, below 4%, below 3%, below 2%, and especially below 1.5%. It should be noted that if increasing the depth of stress is a priority, the suitable lower limit range for K₂O is above 0%, above 0.1%, above 0.3%, and especially above 0.4%.

[0050] The suitable lower limit range of ([Li2O]+[Na2O]+[K2O]) / [Al2O3] is preferably 0.86 or higher, 0.87 or higher, and especially 0.88 or higher. If ([Li2O]+[Na2O]+[K2O]) / [Al2O3] is too small, the efficiency of ion exchange is prone to decrease. On the other hand, even if the molar ratio ([Li2O]+[Na2O]+[K2O]) / [Al2O3] is too large, the efficiency of ion exchange is also prone to decrease. Therefore, the suitable upper limit range of ([Li2O]+[Na2O]+[K2O]) / [Al2O3] is preferably 2.0 or lower, 1.8 or lower, 1.7 or lower, 1.6 or lower, 1.5 or lower, 1.4 or lower, 1.3 or lower, 1.2 or lower, 1.1 or lower, 1.0 or lower, and especially 0.95 or lower.

[0051] ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]+[Al2O3])) is preferably 0.40 or more, 0.41 or more, 0.42 or more, 0.43 or more, 0.44 or more, 0.45 or more, 0.48 or more, 0.50 or more, 0.51 or more, 0.52 or more, 0.53 or more, 0.54 or more, and especially 0.55 or more. If the molar ratio ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]+[Al2O3])) is too small, SnO2 protrusions are prone to precipitate. Furthermore, less oxygen is released from the clarifying agent during melting and forming, making it easier for air bubbles to remain in the glass during plate forming. The upper limit of ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]+[Al2O3])) is not particularly limited. In order to improve clarity while suppressing devitrification, it is preferred to be 4.0 or less, 3.0 or less, 2.0 or less, 1.8 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.90 or less, 0.80 or less, and especially 0.70 or less.

[0052] The ratio of [Li₂O] / ([Na₂O]+[K₂O]) is preferably 0.4–1.0, 0.5–0.9, and particularly 0.6–0.8. If [Li₂O] / ([Na₂O]+[K₂O]) is too small, the ion exchange performance may not be fully utilized. In particular, the efficiency of ion exchange between Li ions in the glass and Na ions in the molten salt is easily reduced. On the other hand, if the molar ratio [Li₂O] / ([Na₂O]+[K₂O]) is too large, devitrification crystals in the glass become more likely to precipitate, making it difficult to form into plates using methods such as overflow pull-down. It should be noted that [Li₂O] / ([Na₂O]+[K₂O]) refers to the value obtained by dividing the Li₂O content by the total amount of Na₂O and K₂O.

[0053] MgO is a component that reduces high-temperature viscosity, improves meltability and formability, or increases strain point and Vickers hardness. In alkaline earth metal oxides, it is the most effective component in improving ion exchange performance. However, if the MgO content is too high, devitrification resistance becomes more easily reduced, especially making it difficult to suppress devitrification during reactions with alumina-based refractories. Therefore, suitable MgO contents are 0–10%, 0–7%, 0–5%, 0.1–3%, 0.2–2.5%, 0.3–2%, 0.4–1.5%, and especially 0.5–1.0%.

[0054] Compared to other components, CaO does not decrease high-temperature viscosity, improve meltability and formability, or increase strain point and Vickers hardness while reducing devitrification resistance. However, excessive CaO content may reduce ion exchange performance or degrade the ion exchange solution during ion exchange treatment. Therefore, suitable upper limits for CaO are below 6%, 5%, 4%, 3.5%, 3%, 2%, 1%, below 1%, below 0.7%, below 0.5%, below 0.3%, below 0.1%, below 0.05%, and especially below 0.01%.

[0055] SrO and BaO are components that reduce high-temperature viscosity, improve melt flow and formability, or increase strain point and Young's modulus. However, if their content is too high, ion exchange reactions can be easily hindered, and the density and coefficient of thermal expansion can become inappropriately high, making the glass more prone to devitrification. Therefore, the suitable contents of SrO and BaO are 0–2%, 0–1.5%, 0–1%, 0–0.5%, 0–0.1%, and especially above 0% and below 0.1%.

[0056] ZnO is a component that improves ion exchange performance, especially its effect on increasing the compressive stress value of the outermost surface. It also reduces high-temperature viscosity without decreasing low-temperature viscosity. The suitable lower limit range for ZnO is 0% or more, 0.1% or more, 0.3% or more, 0.5% or more, 0.7% or more, and especially 1% or more. On the other hand, if the ZnO content is too high, there is a tendency for glass phase separation, decreased devitrification resistance, increased density, or shallower stress depth. Therefore, the suitable upper limit range for ZnO is 10% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1.5% or less, 1.3% or less, 1.2% or less, and especially 1.1% or less.

[0057] P2O5 is a component that improves ion exchange performance, particularly increasing the stress depth. It also improves acid resistance. Furthermore, it enhances the binding force of oxygen electrons based on cations and reduces the basicity of the glass. If the P2O5 content is too low, the ion exchange performance may not be fully realized. In particular, the efficiency of ion exchange between Na ions in the glass and K ions in the molten salt becomes more easily reduced, thus decreasing the stress depth (DOL_ZERO) of the compressive stress layer. K It is easy for the concentration of P2O5 to decrease. Additionally, the glass may become unstable, leading to reduced devitrification resistance. Furthermore, the basicity of the glass may become excessive, reducing the amount of O2 released from the clarifier reaction, decreasing foaming properties, and leaving residual bubbles in the glass during sheet forming. Therefore, the suitable lower limit range for P2O5 is 0% or more, 0.1% or more, 0.4% or more, 0.7% or more, 1% or more, 1.2% or more, 1.4% or more, 1.6% or more, 2% or more, 2.3% or more, 2.5% or more, 2.6% or more, 2.7% or more, 2.8% or more, 2.9% or more, 3.0% or more, 3.2% or more, 3.5% or more, 3.8% or more, 3.9% or more, 4.0% or more, 4.1% or more, 4.2% or more, 4.3% or more, 4.4% or more, 4.5% or more, and especially 4.6% or more. On the other hand, if the P2O5 content is too high, phase separation may occur in the glass, or its water resistance may easily decrease. Furthermore, the stress depth during ion exchange between Li ions in the glass and Na ions in the molten salt becomes excessive, resulting in an insufficient compressive stress value (CS) of the compressive stress layer. Na The concentration of P2O5 tends to decrease. Therefore, the suitable upper limits for P2O5 are below 15%, 10%, 8%, 7%, 6%, 5%, 4.9%, and 4.8%. Setting the P2O5 content within a suitable range will easily result in a non-monotonic distribution curve.

[0058] The preferred concentration of ([SiO2]+1.2×[P2O5])-(3×[Al2O3]+2×[Li2O]+1.5×[Na2O]+[K2O]+[B2O3]) is -40% or more, -30% or more, -25% or more, -24% or more, -23% or more, -22% or more, -21% or more, -20% or more, -19% or more, and especially -18% or more. If ([SiO2]+1.2×[P2O5])-(3×[Al2O3]+2×[Li2O]+1.5×[Na2O]+[K2O]+[B2O3]) is too small, the acid resistance will easily decrease. On the other hand, if ([SiO2]+1.2×[P2O5])-(3×[Al2O3] +2×[Li2O]+1.5×[Na2O]+[K2O]+[B2O3]) is too large, there is a possibility that the ion exchange performance cannot be fully utilized. Therefore, ([SiO2]+1.2×[P2O5])-(3×[Al2O3]+2×[Li2O]+1.5×[Na2O]+[K2O]+[B2O3]) is preferably 30 mol% or less, 20 mol% or less, 15 mol% or less, 10 mol% or less, 5 mol% or less, and especially 0 mol% or less. It should be noted that ([SiO2]+1.2×[P2O5])-(3×[Al2O3]+2×[Li2O]+1.5×[Na2O]+[K2O]+[B2O3]) refers to the total value of SiO2 content and P2O5 content (1.2 times the content) minus the total value of Al2O3 content (3 times the content), Li2O content (2 times the content), Na2O content (1.5 times the content), K2O content, and B2O3 content.

[0059] SnO2 is a clarifying agent and a component that improves ion exchange performance; however, excessive SnO2 content can easily reduce devitrification resistance. Therefore, the suitable lower limit range for SnO2 is 0.001%, 0.002%, 0.005%, 0.007%, and especially 0.010%, while the suitable upper limit range is below 0.30%, 0.27%, 0.25%, 0.20%, 0.18%, 0.15%, 0.12%, 0.10%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.047%, 0.045%, 0.042%, 0.040%, 0.038%, 0.035%, 0.032%, and especially below 0.030%.

[0060] In addition to the ingredients mentioned above, the following ingredients may also be added.

[0061] ZrO2 is a component that improves Vickers hardness and also increases viscosity and strain point near the liquid phase viscosity. However, if its content is too high, its resistance to devitrification may be significantly reduced. Therefore, the suitable content of ZrO2 is 0–3%, 0–1.5%, 0–1%, and especially 0–0.1%.

[0062] TiO2 is a component that improves ion exchange performance and reduces high-temperature viscosity. However, if its content is too high, transparency and devitrification resistance can easily decrease. Therefore, the suitable content of TiO2 is 0-3%, 0-1.5%, 0-1%, 0-0.1%, and especially 0.001-0.1%.

[0063] Cl is a clarifying agent. Especially when used in combination with SnO2, it facilitates the expansion of bubble sizes in glass, thus enhancing the clarifying effect. Because of this relationship, using SnO2 and Cl together allows for maintaining the clarifying effect even with a reduced SnO2 content. On the other hand, excessive Cl content is a component that negatively impacts the environment and equipment. Therefore, the suitable lower limit range of Cl is above 0%, above 0.001%, above 0.005%, above 0.008%, above 0.010%, above 0.015%, above 0.018%, above 0.019%, above 0.020%, above 0.021%, above 0.022%, above 0.023%, above 0.024%, above 0.025%, above 0.027%, above 0.030%, above 0.035%, above 0.040%, above 0.050%, above 0.070%, above 0.090%, especially above 0.100%, and the suitable upper limit range is below 0.3%, below 0.2%, below 0.17%, below 0.15%, especially below 0.12%.

[0064] In addition to the above, 0.001 to 1% of SO3 and CeO2 can also be added as clarifying agents.

[0065] Fe2O3 is an impurity that is unavoidably introduced from the raw materials. Suitable Fe2O3 content is below 1000 ppm (below 0.1%), below 800 ppm, below 600 ppm, below 400 ppm, and especially below 300 ppm. If the Fe2O3 content is too high, the transmittance of the cover glass is likely to decrease. On the other hand, suitable lower limits for Fe2O3 are above 10 ppm, above 20 ppm, above 30 ppm, above 50 ppm, above 80 ppm, and especially above 100 ppm. If the Fe2O3 content is too low, the cost of raw materials can easily increase due to the use of high-purity raw materials.

[0066] Rare earth oxides such as Nd₂O₃, La₂O₃, Y₂O₃, Nb₂O₅, Ta₂O₅, and Hf₂O₃ are components that improve Young's modulus. However, the raw material cost is high, and if added in large quantities, the devitrification resistance can easily decrease. Therefore, the suitable content of rare earth oxides is below 5%, below 4%, below 3%, below 2%, below 1%, below 0.5%, and especially below 0.1%.

[0067] From an environmental perspective, the tempered glass sheet (glass sheet for tempering) of the present invention preferably contains substantially no As₂O₃, Sb₂O₃, PbO, and F as its glass composition. Furthermore, from an environmental perspective, it is also preferably substantially free of Bi₂O₃. "Substantially free of" means that while the stated components are not actively added as glass components, the addition of impurities at a permissible level is allowed; specifically, it refers to the case where the content of the stated components is less than 0.05%.

[0068] The reinforced glass plate (reinforced glass plate) of the present invention preferably has the following characteristics.

[0069] The preferred density is 2.55 g / cm³. 3 Below, 2.53g / cm 3 Below, 2.50g / cm 3 Below, 2.49g / cm 3 Below, 2.45g / cm 3 The following, especially 2.35–2.44 g / cm³ 3 The lower the density, the lighter the reinforced glass sheet can be. It should be noted that "density" can be measured using well-known methods such as Archimedes' method.

[0070] The coefficient of thermal expansion at 30–380℃ is preferably 150 × 10⁻⁶. －7 / ℃ below, 100×10 －7 Below / ℃, especially 50×10 －7 ~95×10 －7 / ℃. It should be noted that "the coefficient of thermal expansion at 30~380℃" refers to the value of the average coefficient of thermal expansion measured using a dilatometer.

[0071] The softening point is preferably below 950°C, 930°C, 920°C, 910°C, or 900°C, particularly between 880 and 900°C. If the softening point is too high, bending processes based on heat treatment become difficult. It should be noted that "softening point" refers to the value determined using the method described in ASTM C338.

[0072] High temperature viscosity 10 2.5The preferred temperature for achieving the desired viscosity at dPa·s is below 1660°C, below 1600°C, below 1590°C, below 1580°C, below 1570°C, and below 1560°C, with a particularly preferred temperature of 1400–1550°C. If the high-temperature viscosity is 10... 2.5 If the temperature at dPa·s is too high, the meltability and formability decrease, making it difficult to shape the molten glass into a plate. It should be noted that "high temperature viscosity 10..." 2.5 "Temperature at dPa·s" refers to the value measured using the platinum ball pulling method.

[0073] The preferred liquid phase viscosity is 10. 3.74 dPa·s or more, 10 4.5 dPa·s or more, 10 4.8 dPa·s or more, 10 4.9 dPa·s or more, 10 5.0 dPa·s or more, 10 5.1 dPa·s or more, 10 5.2 dPa·s or more, 10 5.3 dPa·s or more, 10 5.4 dPa・s and above, especially 10 5.5 Above dPa·s. It should be noted that the higher the liquid phase viscosity, the better the resistance to devitrification, and the less likely devitrification bumps are to form during molding. Here, "liquid phase viscosity" refers to the viscosity value at the liquid phase temperature determined using the platinum ball pulling method. The "liquid phase temperature" is set as follows: glass powder that has passed through a standard 30-mesh (500μm) sieve but remains at a 50-mesh (300μm) sieve is placed in a platinum boat, kept in a temperature gradient furnace for 24 hours, and then the platinum boat is removed. The highest temperature at which devitrification (devitrification bumps) is observed inside the glass is then observed under a microscope.

[0074] The preferred Young's modulus is above 70 GPa, above 74 GPa, 75–100 GPa, and especially 76–90 GPa. If the Young's modulus is low, the cover glass is prone to bending when the plate thickness is thin. It should be noted that the "Young's modulus" can be calculated using the well-known resonance method.

[0075] The reinforced glass plate of the present invention has a compressive stress layer on its surface. The compressive stress value of the outermost surface is preferably 200 MPa or more, 220 MPa or more, 250 MPa or more, 280 MPa or more, 300 MPa or more, 310 MPa or more, and particularly 320 MPa or more. The higher the compressive stress value of the outermost surface, the higher the Vickers hardness. On the other hand, if extremely high compressive stress is formed on the surface, the tensile stress inside the reinforced glass becomes extremely high, and the dimensional changes before and after ion exchange treatment may become larger. Therefore, the compressive stress value of the outermost surface is preferably 1200 MPa or less, 1100 MPa or less, 1000 MPa or less, 900 MPa or less, 700 MPa or less, 680 MPa or less, 650 MPa or less, and particularly 600 MPa or less. It should be noted that shortening the ion exchange time or lowering the temperature of the ion exchange solution tends to increase the compressive stress value of the outermost surface.

[0076] The preferred stress depth is 50 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, 110 μm or more, 120 μm or more, 130 μm or more, and especially 140 μm or more. A deeper stress depth makes it less likely for protrusions or sand particles from the road surface to reach the tensile stress layer when the smartphone is dropped, thus reducing the probability of breakage of the cover glass. On the other hand, if the stress depth is too deep, the dimensional changes before and after ion exchange treatment may increase. There is also a tendency for the compressive stress value of the outermost surface to decrease. Therefore, the preferred stress depth is 200 μm or less, 180 μm or less, and especially 170 μm or less. It should be noted that increasing the ion exchange time or raising the temperature of the ion exchange solution tends to increase the stress depth.

[0077] The compressive stress value at a depth of 2.5 μm is preferably 350 MPa or more, 360 MPa or more, 370 MPa or more, 380 MPa or more, 390 MPa or more, 400 MPa or more, 410 MPa or more, 420 MPa or more, 430 MPa or more, 440 MPa or more, 450 MPa or more, 460 MPa or more, 470 MPa or more, 480 MPa or more, 490 MPa or more, 500 MPa or more, 510 MPa or more, 520 MPa or more, 530 MPa or more, 540 MPa or more, 550 MPa or more, and especially 600 MPa or more. The higher the compressive stress value at a depth of 2.5 μm, the higher the flexural strength. On the other hand, if an extremely large compressive stress is formed at a depth of 2.5 μm, the tensile stress inside the reinforced glass plate may become extremely high. Therefore, the compressive stress value at a depth of 2.5 μm is preferably 800 MPa or less, 750 MPa or less, 730 MPa or less, 700 MPa or less, 680 MPa or less, 650 MPa or less, 640 MPa or less, and especially 630 MPa or less.

[0078] The average compressive stress value at a depth of 30–45 μm is preferably 85 MPa or more, 86 MPa or more, 87 MPa or more, 88 MPa or more, 89 MPa or more, 90 MPa or more, 92 MPa or more, 95 MPa or more, 98 MPa or more, and especially 100 MPa or more. The higher the average compressive stress value at a depth of 30–45 μm, the less likely the smartphone will crack due to road protrusions or sand particles when dropped, thus reducing the probability of breakage of the cover glass. On the other hand, if the average compressive stress value at a depth of 30–45 μm becomes extremely high, the tensile stress inside the tempered glass sheet may become extremely high. Therefore, the average compressive stress value at a depth of 30–45 μm is preferably 150 MPa or less, 140 MPa or less, 130 MPa or less, 125 MPa or less, 120 MPa or less, 115 MPa or less, 110 MPa or less, and especially 105 MPa or less.

[0079] The tempered glass sheet of the present invention preferably has a thickness of 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, 1.1 mm or less, 1.0 mm or less, 0.9 mm or less, and particularly 0.8 mm or less. The thinner the sheet, the lighter the tempered glass sheet becomes. On the other hand, if the sheet is too thin, it is difficult to obtain the desired mechanical strength. Therefore, the sheet thickness is preferably 0.3 mm or more, 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, and particularly 0.7 mm or more.

[0080] The manufacturing method of the reinforced glass plate of the present invention is characterized by comprising the following steps: a preparation step of preparing a reinforced glass plate to be manufactured in accordance with the glass composition described above; and an ion exchange step of subjecting the reinforced glass plate to multiple ion exchange treatments to obtain a reinforced glass plate having a compressive stress layer on its surface. It should be noted that the manufacturing method of the reinforced glass plate of the present invention is characterized by performing multiple ion exchange treatments, but the reinforced glass plate of the present invention includes not only cases involving multiple ion exchange treatments but also cases involving only a single ion exchange treatment.

[0081] The method for manufacturing strengthened glass according to the present invention is as follows. Preferably, glass raw materials mixed in a manner that results in a desired glass composition are first fed into a continuous melting furnace and heated to 1400–1700°C for melting. After clarification, the molten glass is fed into a forming apparatus and formed into a sheet shape, which is then cooled. The method for cutting the sheet shape to a specified size can be a known method.

[0082] As a method for forming molten glass into a sheet, the overflow-draw method is preferred. In the overflow-draw method, the surface of the glass sheet should not contact the surface of the refractory body, and it is formed into a sheet with a free surface. Therefore, it is possible to manufacture glass sheets with good surface quality even without grinding at low cost. Furthermore, in the overflow-draw method, alumina-based refractories or zirconia-based refractories are used as the refractory body. Moreover, the reinforced glass sheet (reinforced glass sheet) of the present invention has good compatibility with alumina-based refractories and zirconia-based refractories (especially alumina-based refractories), and therefore has the property of being difficult to react with these refractories to produce bubbles, bumps, etc.

[0083] Besides the overflow pull-down method, various other forming methods can be used. For example, the float process, pull-down method (slit pull-down method, re-pull-down method, etc.), rolling process, and pressing process can be used.

[0084] During the forming of molten glass, it is preferable to cool it at a cooling rate of 3°C / min or higher and below 1000°C / min within the temperature range between the annealing point and the strain point. The lower limit of this cooling rate is preferably 10°C / min or higher, 20°C / min or higher, 30°C / min or higher, and particularly 50°C / min or higher, while the upper limit is preferably below 1000°C / min, below 500°C / min, and particularly below 300°C / min. If the cooling rate is too fast, the glass structure becomes coarser, making it difficult to improve Vickers hardness after ion exchange treatment. On the other hand, if the cooling rate is too slow, the production efficiency of the glass sheets decreases.

[0085] In the manufacturing method of the reinforced glass plate of the present invention, multiple ion exchange processes are performed. Preferably, after an ion exchange process involving immersion in a molten salt containing KNO3, an ion exchange process involving immersion in a molten salt containing NaNO3 is performed. This ensures a deep stress depth while increasing the compressive stress value of the outermost surface.

[0086] In particular, in the manufacturing method of the reinforced glass plate of the present invention, it is preferable to perform an ion exchange treatment (first ion exchange step) in a mixed molten salt of KNO3 and LiNO3 after performing an ion exchange treatment (second ion exchange step) in a mixed molten salt of KNO3 and LiNO3. In this way, a... Figure 1 The stress distribution curve shown is non-monotonic, meaning it has at least a first peak, a second peak, a first trough, and a second trough. As a result, the probability of cover glass breakage when a smartphone is dropped can be significantly reduced.

[0087] In the first ion exchange step, Li ions in the glass exchange with Na ions in the molten salt. When using a mixed molten salt of NaNO3 and KNO3, Na ions in the glass further exchange with K ions in the molten salt. Here, the ion exchange rate between Li ions in the glass and Na ions in the molten salt is faster than that between Na ions in the glass and K ions in the molten salt, resulting in higher ion exchange efficiency. In the second ion exchange step, Na ions near the glass surface (a shallow region from the outermost surface to 20% of the plate thickness) exchange with Li ions in the molten salt, and Na ions near the glass surface (a shallow region from the outermost surface to 20% of the plate thickness) exchange with K ions in the molten salt. That is, in the second ion exchange step, Na ions near the glass surface can be removed, and K ions with larger ionic radii can be introduced. As a result, the compressive stress value of the outermost surface can be increased while maintaining a deep stress depth.

[0088] In the first ion exchange step, the temperature of the molten salt is preferably 360–400°C, and the ion exchange time is preferably 30 minutes to 6 hours. In the second ion exchange step, the temperature of the ion exchange solution is preferably 370–400°C, and the ion exchange time is preferably 15 minutes to 3 hours.

[0089] Regarding the formation of a non-monotonic stress distribution curve, in the mixed molten salt of NaNO3 and KNO3 used in the first ion exchange process, the concentration of NaNO3 is preferably higher than the concentration of KNO3, and in the mixed molten salt of KNO3 and LiNO3 used in the second ion exchange process, the concentration of KNO3 is preferably higher than the concentration of LiNO3.

[0090] In the first ion exchange process, the concentration of KNO3 in the mixed molten salt of NaNO3 and KNO3 is preferably 0% by mass or more, 0.5% by mass or more, 1% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more, 15% by mass or more, and particularly 20 to 90% by mass. If the concentration of KNO3 is too high, the compressive stress value formed when Li ions in the glass undergo ion exchange with Na ions in the molten salt may be excessively reduced. Furthermore, if the concentration of KNO3 is too low, stress measurement based on a surface stress gauge may become difficult.

[0091] In the second ion exchange process, the concentration of LiNO3 in the mixed molten salt of KNO3 and LiNO3 is preferably more than 0% and less than 5% by mass, more than 0% and less than 3% by mass, more than 0% and less than 2% by mass, and particularly 0.1% to 1% by mass. If the concentration of LiNO3 is too low, Na ions near the glass surface become difficult to remove. On the other hand, if the concentration of LiNO3 is too high, the compressive stress value formed by the ion exchange between Na ions near the glass surface and K ions in the molten salt may be excessively reduced.

[0092] Example 1

[0093] The present invention will now be described based on embodiments. It should be noted that the following embodiments are merely illustrative and are not intended to limit the invention in any way.

[0094] Table 1 shows the glass composition and glass properties of the embodiments of the present invention (samples No. 1 to 8 and No. 12). Table 2 shows the glass composition and glass properties of the comparative examples of the present invention (samples No. 9 to 11). It should be noted that in the table, "NA" means not measured, "(Li2O+Na2O+K2O) / Al2O3" refers to the molar ratio ([Li2O]+[Na2O]+[K2O]) / [Al2O3], and "(Si+P+B) / ((100Sn)×(Al+Li+Na+K+Mg+Ca+Sr+Ba+Zn))" refers to the molar ratio ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO])).

[0095] Table 1

[0096]

[0097] Table 2

[0098]

[0099] The samples listed in the table were prepared as follows: First, the glass raw materials were mixed according to the glass composition shown in the table and melted in a platinum autoclave at 1600°C for 21 hours. Next, the resulting molten glass was poured onto a carbon plate, shaped into a flat plate, and cooled at a rate of 3°C / min within the temperature range between the annealing point and the strain point to obtain a glass plate (for strengthening). The obtained glass plates were optically polished to a thickness of 1.5 mm, and various properties were evaluated.

[0100] Density (ρ) is a value determined using the well-known Archimedes method.

[0101] The coefficient of thermal expansion (α) at ​​30–380℃ 30-380℃ () is the value of the average coefficient of thermal expansion determined using a dilatometer.

[0102] High temperature viscosity 10 2.5 Temperature at dPa·s (10 2.5 dPa・s) is a value determined using the platinum ball dip method.

[0103] The softening point (Ts) is a value determined based on the method of ASTM C338.

[0104] The liquidus temperature (TL) is set as follows: glass powder that has passed through a standard sieve of 30 mesh (500 μm) but remains at 50 mesh (300 μm) is placed in a platinum boat and kept in a temperature gradient furnace for 24 hours. Afterward, the platinum boat is removed, and the highest temperature at which devitrification (devitrifying bumps) is observed inside the glass under a microscope. Liquidus viscosity (logη at TL) is the viscosity value at the liquidus temperature determined using the platinum ball pulling method, and is expressed as logη (logarithm).

[0105] The acid resistance test was evaluated as follows: A glass sample, mirror-polished on both sides to a size of 50 × 10 × 1.0 mm, was used as the test sample. After thorough cleaning with neutral detergent and pure water, it was immersed in a 5% (w / w) HCl aqueous solution heated to 80°C for 24 hours. The mass loss per unit surface area (mg / cm²) before and after immersion was calculated. 2 ).

[0106] The alkali resistance test was evaluated as follows: A glass sample, mirror-polished on both sides to a size of 50 × 10 × 1.0 mm, was used as the test sample. After thorough cleaning with neutral detergent and pure water, it was immersed in a 5% (w / w) NaOH aqueous solution heated to 80°C for 6 hours. The mass loss per unit surface area (mg / cm²) before and after immersion was calculated. 2 ).

[0107] Young's modulus (E) was calculated using the method described in JIS R1602-1995 "Test method for elastic modulus of fine ceramics".

[0108] Next, each glass plate was immersed in molten KNO3 at 430°C for 4 hours to perform ion exchange treatment, resulting in a strengthened glass plate with a compressive stress layer on the surface. After cleaning the glass surface, the compressive stress value (CS) of the outermost compressive stress layer was calculated by observing the number and spacing of interference fringes using a surface stress meter FSM-6000 (manufactured by Orihara Corporation). K ) and stress depth (DOL_ZERO K Here, DOL_ZERO K It is the depth at which the compressive stress value becomes zero. It should be noted that when calculating the stress characteristics, the refractive index of each sample was set to 1.51, and the optical elastic constant was set to 29.0 [(nm / cm) / MPa].

[0109] In addition, each glass plate was immersed in molten NaNO3 at 380°C for 1 hour to perform ion exchange treatment, resulting in a strengthened glass plate. After cleaning the glass surface, the compressive stress value (CS) of the outermost surface was calculated from the phase difference distribution curve observed using a SLP-1000 photoelastic stress meter (manufactured by Orihara Corporation). Na ) and stress depth (DOL_ZERO Na Here, DOL_ZERO Na It is the depth at which the stress value becomes zero. It should be noted that when calculating the stress characteristics, the refractive index of each sample was set to 1.51, and the optical elastic constant was set to 29.0 [(nm / cm) / MPa].

[0110] In addition, each glass plate was crushed into a size of 2 to 5.6 mm, graded, and heated to 1650 °C. When the molten glass was directly observed (High Temperature Observation; HTO), the clarity was rated as "0" for those that did not observe bubbles larger than 75 μm, and "△" for those that did not.

[0111] Table 1 clearly shows that samples No. 1–8 and No. 12, due to their large molar ratio ([Li₂O] + [Na₂O] + [K₂O]) / [Al₂O₃], exhibited higher compressive stress values ​​(CS) in the compressive stress layer after ion exchange treatment with KNO₃ molten salt. K With a compressive stress exceeding 1090 MPa, and further ion exchange treatment with NaNO3 molten salt, the compressive stress value (CS) of the outermost compressive stress layer... Na The pressure is above 279 MPa.

[0112] Furthermore, as can be clearly seen from Table 1, samples No. 1 to 8 and No. 12 have a good clarification rating because the molar ratio ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO])) is above 0.40.

[0113] On the other hand, as can be clearly seen from Table 2, samples No. 9 and 10 have a lower molar ratio ([Li2O]+[Na2O]+[K2O]) / [Al2O3] than 0.86, therefore, compared with the samples in the examples, the compressive stress values ​​(CS) of the compressive stress layer are lower. K The clarification of sample No. 11 is poor because the molar ratio ([SiO2]+[B2O3]+[P2O5]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO])) is less than 0.40.

[0114] Example 2

[0115] First, glass raw materials were blended according to the glass compositions of samples No. 1 and No. 6 in Table 1, and melted in a platinum autoclave at 1600°C for 21 hours. Next, the resulting molten glass was poured onto a carbon plate, shaped into a flat plate, and cooled at a rate of 3°C / min within the temperature range between the annealing point and the strain point to obtain a glass plate (for strengthening). The obtained glass plate was then optically polished to a thickness of 0.7 mm.

[0116] The obtained reinforced glass plate was immersed in molten NaNO3 at 380°C (100% by mass) for 3 hours for ion exchange treatment, and then immersed in a mixed molten salt of KNO3 and LiNO3 at 380°C (2.5% by mass) for 75 minutes for ion exchange treatment. Further, after cleaning the surface of the obtained reinforced glass plate, the stress distribution curve of the reinforced glass plate was measured using a scattered light photoelastic stress meter SLP-1000 (manufactured by Orihara Corporation) and a surface stress meter FSM-6000 (manufactured by Orihara Corporation). The results were consistent with... Figure 1 The same non-monotonic stress distribution curve, i.e., a stress distribution curve with the first peak, the second peak, the first valley, and the second valley.

[0117] Example 3

[0118] First, glass raw materials were blended according to the glass compositions of samples No. 6, 9, and 12 in Table 1, and melted in a platinum autoclave at 1600°C for 21 hours. Next, the resulting molten glass was poured onto a carbon plate, shaped into a flat plate, and cooled at a rate of 3°C / min within the temperature range between the annealing point and the strain point to obtain a glass plate (for strengthening). The surface of the obtained glass plate was optically polished to a thickness of 0.8 mm.

[0119] The obtained reinforced glass plate was immersed in a mixed molten salt of KNO3 and NaNO3 (NaNO3 concentration 60% by mass) at 380°C for 3 hours for ion exchange treatment, and then immersed in a mixed molten salt of KNO3 and LiNO3 (LiNO3 concentration 1.0% by mass) at 380°C for 30 minutes for ion exchange treatment (condition A). Furthermore, after cleaning the surface of the obtained reinforced glass plate, the stress distribution curve of the reinforced glass plate was measured using a scattered light photoelastic stress meter SLP-1000 (manufactured by Orihara Corporation) and a surface stress meter FSM-6000 (manufactured by Orihara Corporation). The results were obtained... Figure 2 The stress distribution curve shown is non-monotonic.

[0120] The obtained reinforced glass plate was immersed in a mixed molten salt of KNO3 and NaNO3 (NaNO3 concentration 60% by mass) at 380°C for 3 hours for ion exchange treatment, and then immersed in a mixed molten salt of KNO3, NaNO3 and LiNO3 (NaNO3 concentration 4.0% by mass, LiNO3 concentration 1.0% by mass) at 380°C for 45 minutes for ion exchange treatment (condition B). Furthermore, after cleaning the surface of the obtained reinforced glass plate, the stress distribution curve of the reinforced glass plate was measured using a scattered light photoelastic stress meter SLP-1000 (manufactured by Orihara Corporation) and a surface stress meter FSM-6000 (manufactured by Orihara Corporation). The results were all obtained... Figure 3 The stress distribution curve shown is non-monotonic.

[0121] Table 3 shows the compressive stress (CS), stress depth (DOC), and compressive stress (CS) at a depth of 2.5 μm at the outermost surface of each sample's stress distribution curve. 2.5 ), and the average compressive stress at a depth of 30–45 μm (CS) 30‐45 ).

[0122] Table 3

[0123]

[0124] Depend on Figure 2 , Figure 3Table 3 clearly shows that in the stress distribution curves of samples No. 6 and 12 after ion exchange under conditions A and B, CS 2.5 For pressures above 350 MPa and CS 30‐45 The stress is above 85 MPa, therefore it is considered to have high bending strength and high drop strength. On the other hand, in the stress distribution curves of sample No. 9 under conditions A and B, CS... 30‐45 The drop strength is less than 85 MPa, therefore it is considered low.

[0125] Industrial availability

[0126] The tempered glass plate of the present invention is suitable as a cover glass for touch panel displays in mobile phones, digital cameras, PDAs (portable terminals), etc. In addition to these applications, the tempered glass plate of the present invention is also expected to be used in applications requiring high mechanical strength, such as window glass, disk substrates, flat panel display substrates, flexible display substrates, cover glass for solar cells, cover glass for solid-state imaging elements, and automotive cover glass.

Claims

1. A reinforced glass plate, characterized in that, a reinforced glass plate having a compressive stress layer on its surface, wherein... As a glass composition, it contains, by mole percent, 40%–80% SiO2, 17%–25% Al2O3, 0%–10% B2O3, 3%–15% Li2O, 1%–21% Na2O, 0%–10% K2O, 0%–10% MgO, 0%–10% ZnO, 0%–15% P2O5, and SnO2. 0.001%~0.30%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((10 0×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.

40.

2. The reinforced glass plate according to claim 1, characterized in that, The content of B2O3 is 0.1 mol% to 3 mol%.

3. The reinforced glass plate according to claim 1 or 2, characterized in that, The SnO2 content is less than 0.045 mol%.

4. The reinforced glass plate according to claim 1 or 2, characterized in that, The Cl content is 0.02 mol% to 0.3 mol%.

5. A reinforced glass plate, characterized in that, a reinforced glass plate having a compressive stress layer on its surface, is characterized in that, As a glass composition, it contains, in molar percentage, 40%–80% SiO2, 17%–25% Al2O3, 0%–10% B2O3, 3%–15% Li2O, 1%–21% Na2O, 0%–10% K2O, 0%–10% MgO, 0%–10% ZnO, 0%–15% P2O5, 0.001%–0.045% SnO2 and 0.02%–0.3% Cl, and ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.

86.

6. A reinforced glass plate, which is a reinforced glass plate having a compressive stress layer on its surface, characterized in that, As a glass composition, it contains, by mole percent: SiO2 40%–80%, Al2O3 17%–25%, B2O3 0.1%–3%, Li2O 3%–15%, Na2O 1%–21%, K2O 0%–10%, MgO 0%–10%, ZnO 0%–10%, P2O5 0%–15%, and SnO2. 0.001%~0.30% and Cl0.02%~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5 ]) / ((100×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.

40.

7. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The content of P2O5 is above 2.5 mol%.

8. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The Fe2O3 content is 0.001 mol% to 0.1 mol%.

9. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The TiO2 content is 0.001 mol% to 0.1 mol%.

10. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The compressive stress value of the outermost surface of the compressive stress layer is 200MPa to 1200MPa.

11. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The stress depth of the compressive stress layer is 50μm to 200μm.

12. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The compressive stress at a depth of 2.5 μm is above 350 MPa.

13. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The average compressive stress at a depth of 30μm to 45μm is above 85MPa.

14. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, High temperature viscosity 10 2.5 The temperature at dPa・s is below 1650℃.

15. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, It has an overflow confluence surface in the central part in the thickness direction of the plate.

16. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, Cover glass for touch panel displays.

17. The tempered glass plate according to any one of claims 1, 2, 5, and 6, characterized in that, The stress distribution curve in the thickness direction has at least the first peak, the second peak, the first valley, and the second valley.

18. A method for manufacturing a reinforced glass plate, characterized in that, It includes the following processes: The preparation process for a strengthening glass plate, wherein the strengthening glass plate is composed of, by molar percentage, 40%–80% SiO2, 17%–25% Al2O3, 0%–10% B2O3, 3%–15% Li2O, 1%–21% Na2O, 0%–10% K2O, 0%–10% MgO, 0%–10% ZnO, 0%–15% P2O5, and SnO2. 0.001%~0.30%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((10 0×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40; and The ion exchange process involves subjecting the reinforced glass plate to multiple ion exchange treatments to obtain a reinforced glass plate with a compressive stress layer on its surface.

19. A strengthening glass plate, which is a strengthening glass plate capable of ion exchange, characterized in that, As a glass composition, it contains, by mole percent: 40%–80% SiO2, 17%–25% Al2O3, 0%–10% B2O3, 3%–15% Li2O, 1%–21% Na2O, 0%–10% K2O, 0%–10% MgO, 0%–10% ZnO, 0%–15% P2O5, and SnO2. 0.001%~0.30%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((10 0×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.

40.

20. A strengthening glass plate, which is a strengthening glass plate capable of ion exchange, characterized in that, As a glass composition, it contains, by mole percent: 40%–80% SiO2, 17%–25% Al2O3, 0%–10% B2O3, 3%–15% Li2O, 1%–21% Na2O, 0%–10% K2O, 0%–10% MgO, 0%–10% ZnO, 0%–15% P2O5, 0.001%–0.045% SnO2, and Cl. 0.02%~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100 ×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.

40.

21. A strengthening glass plate, which is a strengthening glass plate capable of ion exchange, characterized in that, As a glass composition, it contains, by mole percent: 40%–80% SiO2, 17%–25% Al2O3, 0.1%–3% B2O3, 3%–15% Li2O, 1%–21% Na2O, 0%–10% K2O, 0%–10% MgO, 0%–10% ZnO, 0%–15% P2O5, 0.001%–0.30% SnO2, and Cl. 0.02%~0.3%, ([Li2O]+[Na2O]+[K2O]) / [Al2O3]≥0.86, and ([SiO2]+[B2O3]+[P2O5]) / ((100 ×[SnO2])×([Al2O3]+[Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO]))≥0.40.

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