Method for producing glass

Abstract

The method for producing glass includes a first etching step S1 for etching glass with a first etching liquid and a second etching step S2 for etching the glass with a second etching liquid after the first etching step S1. The first etching liquid contains, by mass% in a dehydrated state, 30-90% hydrofluoric acid and 10-70% hydrochloric acid. The second etching liquid contains, by mass% in a dehydrated state, 10-50% hydrofluoric acid and 50-90% sulfuric acid.

Description

Glass manufacturing method

[0001] The present invention relates to a method for producing glass.

[0002] Glass is widely used as a cover material for various electronic terminals and display devices. This type of glass is required to have improved mechanical strength and smoothness. Therefore, in order to improve the mechanical strength and smoothness of the glass, etching is sometimes performed on the glass.

[0003] For example, Patent Document 1 discloses that, in order to improve the smoothness of glass, a first etching is performed with an etching solution (surface polishing solution) containing 40 to 90% by weight of sulfuric acid and 0.4 to 4% by weight of hydrofluoric acid, and then a second etching is performed with an etching solution (post-polishing solution) containing 2 to 30% by weight of hydrofluoric acid. Note that, like the etching solution used in the first etching, an etching solution containing hydrofluoric acid and sulfuric acid is exemplified for the second etching.

[0004] Japanese Patent Application Laid-Open No. 2007-297228

[0005] However, conventional etching cannot sufficiently improve the mechanical strength of glass, and there is still room for improvement.

[0006] An object of the present invention is to provide a glass having high mechanical strength.

[0007] (1) The present invention, which has been invented to solve the above-mentioned problems, is a method for manufacturing glass, comprising a first etching step of etching glass with a first etching liquid, and a second etching step of etching the glass with a second etching liquid after the first etching step, wherein the first etching liquid contains, in mass %, 30 to 90% hydrofluoric acid and 10 to 70% hydrochloric acid in a dehydrated state, and the second etching liquid contains, in mass %, 10 to 50% hydrofluoric acid and 50 to 90% sulfuric acid in a dehydrated state.

[0008] In this way, the first etching liquid is a hydrofluoric acid-hydrochloric acid system. Therefore, in the first etching step, a rough processing is performed to smooth out the steep shapes of the glass surface caused by scratches such as microcracks. On the other hand, the second etching liquid is a hydrofluoric acid-sulfuric acid system. Therefore, in the second etching step, a finishing process is performed to remove the gentle irregularities (traces of scratches) on the glass surface left by the first etching step and smooth the glass surface. Therefore, the first etching step and the second etching step remove scratches and their traces that could cause breakage from the glass surface, thereby obtaining glass with high mechanical strength.

[0009] (2) In the above configuration (1), it is preferable that at least one of the first etching solution and the second etching solution contains ammonium hydrogen fluoride.

[0010] This improves the surface quality of the glass and makes it easier to achieve high mechanical strength.

[0011] (3) In the above configuration (2), the first etching solution preferably contains, in a dehydrated state, 40 to 80% by mass of hydrofluoric acid, 10 to 40% by mass of hydrochloric acid, and 3 to 20% by mass of ammonium hydrogen fluoride.

[0012] This improves the surface quality of the glass and makes it easier to achieve high mechanical strength.

[0013] (4) In the above configuration (2) or (3), the second etching solution preferably contains, in a dehydrated state, 10 to 30% by mass of hydrofluoric acid, 50 to 80% by mass of sulfuric acid, and 3 to 20% by mass of ammonium hydrogen fluoride.

[0014] This improves the surface quality of the glass and makes it easier to achieve high mechanical strength.

[0015] (5) In any of the above (1) to (4), it is preferable that the first etching liquid has a water content of 50 to 95 mass %, and the second etching liquid has a water content of 50 to 90 mass %.

[0016] In this way, the concentrations of solutes such as hydrofluoric acid in the first etching liquid and the second etching liquid fall within an appropriate range, making it easier to obtain glass with high mechanical strength.

[0017] (6) In any of the above configurations (1) to (5), when the etching rate in the first etching step is R1 (μm / min) and the etching rate in the second etching step is R2 (μm / min), it is preferable that R1 / R2≦20.

[0018] In this way, the etching rates in the first etching step and the second etching step fall within appropriate ranges, making it easier to obtain glass having high mechanical strength.

[0019] (7) In any of the above configurations (1) to (6), when the etching rate in the first etching step is R1 (μm / min) and the etching rate in the second etching step is R2 (μm / min), it is preferable that R1≦9.5 μm / min and R2≧0.5 μm / min.

[0020] In this way, the etching rates in the first etching step and the second etching step fall within appropriate ranges, making it easier to obtain glass having high mechanical strength.

[0021] (8) In any of the above configurations (1) to (7), when the etching amount in the first etching step is V1 (μm) and the etching amount in the second etching step is V2 (μm), it is preferable that V1 / V2≦80.

[0022] In this way, the etching amount in each of the first etching step and the second etching step falls within an appropriate range, making it easier to obtain glass having high mechanical strength.

[0023] (9) In any of the above configurations (1) to (8), when the etching amount in the first etching step is V1 (μm) and the etching amount in the second etching step is V2 (μm), it is preferable that V1≦80 μm and V2≦10 μm.

[0024] This allows the etching amount in each of the first and second etching steps to fall within an appropriate range, making it easier to obtain glass with high mechanical strength. Furthermore, the amount of glass removed by etching is reduced, improving production efficiency.

[0025] (10) In any of the above configurations (1) to (9), it is preferable that in the first etching step, the temperature of the first etching liquid is 1 to 50°C and the time for treating the glass with the first etching liquid is 0.5 to 50 minutes, and in the second etching step, the temperature of the second etching liquid is 1 to 50°C and the time for treating the glass with the second etching liquid is 0.5 to 50 minutes.

[0026] In this way, the temperature of the etching solution and the treatment time are in appropriate ranges in each of the first etching step and the second etching step, making it easier to obtain glass having high mechanical strength.

[0027] (11) In any of the above configurations (1) to (10), the glass may be an alkali-containing glass containing an alkali metal component as a glass composition, and the method may further include an ion exchange step of subjecting the glass to an ion exchange treatment after the first etching step and before the second etching step.

[0028] In this way, the glass is chemically strengthened by the ion exchange treatment, which makes it easier to increase the mechanical strength of the glass. Furthermore, because the first etching step is performed before the ion exchange step, the ion exchange step can be performed in a balanced manner on the glass surface from which steep irregularities due to microcracks and the like have been removed. Furthermore, because the second etching step is performed after the ion exchange step, even if defects (surface roughness) are formed on the glass surface due to the ion exchange step, these defects can be removed.

[0029] (12) In any of the above configurations (1) to (10), the glass may be an alkali-containing glass containing an alkali metal component as a glass composition, and the method may further include an ion exchange step of subjecting the glass to an ion exchange treatment before the first etching step.

[0030] In this way, the glass is chemically strengthened, which makes it easier to increase the mechanical strength of the glass. Furthermore, since the first etching step and the second etching step are performed after the ion exchange step, even if defects (surface roughness) are formed on the glass surface due to the ion exchange step, the defects can be removed.

[0031] (13) In the above configuration (11) or (12), the glass after the second etching step has a surface compressive stress layer, and when the maximum compressive stress value of the surface compressive stress layer is CS (MPa), the depth of the surface compressive stress layer is DOL (μm), and the thickness of the glass after the second etching step is t1 (μm), it is preferable that CS≧450 MPa and DOL / t1≧0.15.

[0032] In this way, the mechanical strength of the glass can be further improved.

[0033] (14) In any of the above configurations (11) to (13), the alkali-containing glass preferably contains, as a glass composition, in mole percent, 40 to 80% SiO, 5 to 25% AlO, 0 to 30% BO, 0 to 25% LiO, 1 to 25% NaO, 0 to 15% KO, 0 to 20% MgO, 0 to 10% ZnO, 0 to 15% PO, and 0 to 1% SnO.

[0034] In this way, the mechanical strength of the glass can be easily increased by the ion exchange treatment.

[0035] (15) In any of the above (1) to (10), the glass may be alkali-free glass that does not substantially contain alkali metal components as a glass composition.

[0036] In the present invention, even when the glass is alkali-free glass (untempered glass), the mechanical strength can be improved by the first etching step and the second etching step.

[0037] (16) In any one of the above (1) to (15), the glass after the second etching step is preferably in the form of a sheet having a thickness of 0.3 mm or less.

[0038] The present invention is particularly useful for such thin sheet glass, which is prone to breakage.

[0039] (17) The present invention, which has been invented to solve the above-mentioned problems, is a method for manufacturing glass, comprising: a first etching step of etching glass with a first etching liquid; and a second etching step of etching the glass with a second etching liquid after the first etching step, wherein the first etching liquid contains, by mass, 50 to 95% water, 2 to 45% hydrofluoric acid, and 0.5 to 30% hydrochloric acid; and the second etching liquid contains, by mass, 50 to 90% water, 1 to 25% hydrofluoric acid, and 5 to 45% sulfuric acid.

[0040] In this way, scratches and traces thereof that may cause breakage are removed from the glass surface by the first etching step and the second etching step, so that glass having high mechanical strength can be obtained.

[0041] (18) The present invention, which has been invented to solve the above-mentioned problems, is a method for manufacturing glass, comprising: a first etching step of etching glass with a first etching liquid; and a second etching step of etching the glass with a second etching liquid after the first etching step, wherein the first etching liquid is an etching liquid containing hydrochloric acid, and the second etching liquid is an etching liquid containing sulfuric acid.

[0042] (19) In the configuration of (18) above, it is preferable that at least one of the first etching solution and the second etching solution contains ammonium hydrogen fluoride.

[0043] According to the present invention, a glass having high mechanical strength can be provided.

[0044] Fig. 1 is a flow chart of a method for manufacturing glass according to a first embodiment of the present invention. Fig. 2 is a flow chart of a method for manufacturing glass according to a second embodiment of the present invention. Fig. 3 is a flow chart of a method for manufacturing glass according to a third embodiment of the present invention. Fig. 4 is a perspective view showing an embodiment of a ring-on-ring test (ROR test). Fig. 5 is a side view showing an embodiment of a two-point bending test.

[0045] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that in each embodiment, when only a portion of the configuration is described, the configuration of another embodiment previously described can be applied to the remaining portion of the configuration. Furthermore, in addition to the combination of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments can also be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

[0046] 1 , a method for manufacturing glass according to a first embodiment includes, in this order, a first etching step S1 in which glass is immersed in a first etching liquid and etched, and a second etching step S2 in which glass is immersed in a second etching liquid and etched. Note that the etching steps S1 and S2 are not limited to immersing the glass in the etching liquid, and may be, for example, a method in which the etching liquid is applied or sprayed onto the glass, as long as the etching liquid can be brought into contact with the glass.

[0047] The glass before the first etching step S1 is preferably in a sheet form. The sheet form of glass is obtained, for example, by cutting a sheet form of mother glass obtained by a forming method such as an overflow downdraw method, a slot downdraw method, a float method, or a redraw method into small glass pieces. In order to obtain a smooth surface, the overflow downdraw method is preferably used as the forming method, and in order to obtain thin glass over a large area, the slot downdraw method is preferably used.

[0048] The thickness t0 of the glass before the first etching step S1 is preferably 1.1 mm (1100 μm) or less, 0.7 to 0.02 mm (700 to 20 μm), or 0.5 to 0.025 mm (500 to 25 μm).

[0049] The glass may be an alkali glass containing an alkali metal component in its glass composition, or an alkali-free glass containing substantially no alkali metal component in its glass composition. Here, "substantially no alkali metal component" refers to, for example, a glass composition containing 0.5 mol % or less of alkali metal oxides (LiO, NaO, and KO).

[0050] The alkali-free glass used in the present invention preferably contains, as a glass composition, in mole percent, 60 to 75% SiO, 5 to 20% AlO, 0 to 15% BO, 0 to 0.5% LiO + NaO + KO (total amount of LiO, NaO and KO), 0 to 10% MgO, 0 to 15% CaO, 0 to 10% SrO, and 0 to 10% BaO.

[0051] The first etching solution used in the first etching step S1 contains, in mass %, 30 to 90% hydrofluoric acid and 10 to 70% hydrochloric acid in a dehydrated state. Preferably, the first etching solution contains, in mass %, 40 to 90% hydrofluoric acid and 10 to 60% hydrochloric acid in a dehydrated state.

[0052] The first etching solution preferably contains ammonium hydrogen fluoride (acidic ammonium fluoride) to improve the surface quality of the glass. When containing ammonium hydrogen fluoride, the first etching solution preferably contains, in mass %, in a dehydrated state, (1) 40 to 80% hydrofluoric acid, 10 to 40% hydrochloric acid, and 3 to 20% ammonium hydrogen fluoride, more preferably (2) 42 to 78% hydrofluoric acid, 12 to 38% hydrochloric acid, and 4 to 18% ammonium hydrogen fluoride, and even more preferably (3) 45 to 75% hydrofluoric acid, 15 to 35% hydrochloric acid, and 5 to 15% ammonium hydrogen fluoride.

[0053] The second etching solution used in the second etching step S2 is in a dehydrated state and contains, by mass %, 10 to 50% hydrofluoric acid and 50 to 90% sulfuric acid.

[0054] The second etching solution preferably contains ammonium hydrogen fluoride to improve the surface quality of the glass. When containing ammonium hydrogen fluoride, the second etching solution preferably contains, in mass %, in a dehydrated state, (1) 10 to 30% hydrofluoric acid, 50 to 80% sulfuric acid, and 3 to 20% ammonium hydrogen fluoride; (2) 12 to 28% hydrofluoric acid, 52 to 78% sulfuric acid, and 4 to 18% ammonium hydrogen fluoride; or (3) 15 to 25% hydrofluoric acid, 55 to 75% sulfuric acid, and 5 to 15% ammonium hydrogen fluoride. Furthermore, the hydrofluoric acid content of the second etching solution is preferably less than that of the first etching solution.

[0055] The first etching solution preferably has a water content of 50 to 95% by mass, more preferably 50 to 90% by mass. Similarly, the second etching solution preferably has a water content of 50 to 90% by mass. Specifically, the first etching solution preferably contains, in mass %, 50 to 95% water, 2 to 45% hydrofluoric acid, and 0.5 to 30% hydrochloric acid in a water-containing state, and more preferably contains 50 to 90% water, 4 to 45% hydrofluoric acid, and 1 to 30% hydrochloric acid. The second etching solution preferably contains, in mass %, 50 to 90% water, 1 to 25% hydrofluoric acid, and 5 to 45% sulfuric acid in a water-containing state. When ammonium hydrogen fluoride is included, the first etching solution preferably contains, in mass %, 50 to 90% water, 4 to 40% hydrofluoric acid, 1 to 20% hydrochloric acid, and 0.3 to 10% ammonium hydrogen fluoride in a water-containing state. The second etching liquid preferably contains, in a water-containing state, 50 to 90% by mass of water, 1 to 15% by mass of hydrofluoric acid, 5 to 40% by mass of sulfuric acid, and 0.3 to 10% by mass of ammonium hydrogen fluoride. Note that neither the first etching liquid nor the second etching liquid needs to contain ammonium hydrogen fluoride.

[0056] At least one of the first etching solution and the second etching solution may contain an additive in an amount of 0.6 to 1.0 mass % in a water-containing state. Examples of the additive include a surfactant and / or a chelating agent. Examples of the chelating agent include compounds having two or more carboxyl groups or two or more hydroxyl groups, such as citric acid, gluconic acid, succinic acid, oxalic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), hydroxyethylidene diphosphinic acid (HEDP), nitrilotriacetic acid, diethylenetriaminepentaacetic acid, dihydroxyethylglycine, and hydroxyethylenediaminetriacetic acid.

[0057] When the etching rate in the first etching step S1 is R1 (μm / min) and the etching rate in the second etching step S2 is R2 (μm / min), the upper limit range of the etching rate ratio R1 / R2 is preferably 20 or less, 18 or less, 15 or less, 10 or less, 7 or less, 5 or less, 3 or less, or 2 or less. The lower limit range of the etching rate ratio R1 / R2 is preferably 0.8 or more, 0.9 or more, or 1.0 or more.

[0058] The upper limit of the etching rate R1 is preferably 9.5 μm / min or less, 9.3 μm / min or less, or 9.0 μm / min or less, and the lower limit of the etching rate R1 is preferably 0.5 μm / min or more, 0.55 μm / min or more, or 0.6 μm / min or more.

[0059] The upper limit range of the etching rate R2 is preferably 7 μm / min or less, 6.5 μm / min or less, 6.0 μm / min or less, or 5.5 μm / min or less.The lower limit range of the etching rate R2 is preferably 0.5 μm / min or more, 0.55 μm / min or more, or 0.6 μm / min or more.

[0060] When the etching amount in the first etching step S1 is V1 (μm) and the etching amount in the second etching step S2 is V2 (μm), the upper limit range of the etching amount ratio V1 / V2 is preferably 80 or less, 70 or less, 50 or less, 30 or less, 20 or less, 10 or less, 5 or less, or 3 or less. The lower limit range of the etching amount ratio V1 / V2 is preferably 0.5 or more, 0.8 or more, 1 or more, or 1.2 or more.

[0061] The upper limit of the etching amount V1 is preferably 80 μm or less, 60 μm or less, or 50 μm or less, and the lower limit of the etching amount V1 is preferably 0.5 μm or more, 0.6 μm or more, or 0.8 μm or more.

[0062] The upper limit range of the etching amount V2 is preferably 10 μm or less, 8 μm or less, or 6 μm or less, and the lower limit range of the etching amount V2 is preferably 0.5 μm or more, 0.6 μm or more, or 0.8 μm or more.

[0063] The thickness t1 of the glass after the second etching step S2 is preferably 1000 μm or less, 700 μm or less, 500 μm or less, or 300 μm or less for display applications that do not require bending deformation. The thickness t1 of the glass after the second etching step S2 is preferably 100 μm or less, 70 μm or less, 50 μm or less, or 35 μm or less for display applications that require bending deformation.

[0064] When the temperature of the first etching solution in the first etching step S1 is H1 and the time for which the glass is immersed in the first etching solution (treatment time) is P1, the temperature H1 is preferably 1 to 50°C, and the immersion time P1 is preferably 0.5 to 50 minutes.

[0065] When the temperature of the second etching solution in the second etching step S2 is H2 and the time for immersing the glass in the second etching solution (treatment time) is P2, the temperature H2 is preferably 1 to 50°C, and the immersion time P2 is preferably 0.5 to 50 minutes.

[0066] The upper limit range of the temperature ratio H1 / H2 is preferably 1.5 or less, 1.3 or less, or 1.2 or less, and the lower limit range of the temperature ratio H1 / H2 is preferably 0.9 or more, 0.8 or more, or 0.6 or more.

[0067] The upper limit range of the immersion time ratio P1 / P2 is preferably 80 or less, 50 or less, 40 or less, or 30 or less. The lower limit range of the immersion time ratio P1 / P2 is preferably 0.7 or more, 0.8 or more, 0.9 or more, or 1.0 or more.

[0068] According to the manufacturing method of the first embodiment described above, the first etching solution used in the first etching step S1 is a hydrofluoric acid-hydrochloric acid solution. Therefore, the first etching step S1 involves rough processing to efficiently smooth out the steep contours of the glass surface caused by scratches such as microcracks. Meanwhile, the second etching solution used in the second etching step S1 is a hydrofluoric acid-sulfuric acid solution. Therefore, the second etching step S2 involves finishing to remove the gentle irregularities (traces of scratches) on the glass surface left by the first etching step S1 and smooth the glass surface. Therefore, the first etching step S1 and the second etching step S2 remove scratches and their traces that could cause breakage from the glass surface, resulting in glass with high mechanical strength.

[0069] The fracture stress of the glass after the second etching step S2 in a ring-on-ring test or a two-point bending test is preferably 2500 MPa or more, more preferably 2600 MPa or more, even more preferably 2800 MPa or more, or even more preferably 3000 MPa or more.

[0070] 2 , a method for manufacturing glass according to a second embodiment includes, in this order, a first etching step S3 of immersing glass in a first etching liquid to etch it, an ion exchange step S4 of immersing the glass in a molten salt (ion exchange liquid) to perform an ion exchange treatment, and a second etching step S5 of immersing the glass in a second etching liquid to etch it. Note that the ion exchange step S4 is not limited to immersing the glass in a molten salt, and may be, for example, a method of applying or spraying molten salt onto the glass, as long as the molten salt can be brought into contact with the glass.

[0071] The first etching step S3 is similar to the first etching step S1 in the first embodiment, and the second etching step S5 is similar to the second etching step S2 in the first embodiment. Therefore, the ion exchange step S5 will be mainly described below.

[0072] The glass is an alkali-containing glass containing an alkali metal component in its glass composition for ion exchange treatment. The alkali-containing glass is preferably, for example, an aluminosilicate glass. The aluminosilicate glass preferably contains, in mole percent, 40-80% SiO2, 5-25% Al2O3, 0-30% BO3, 0-25% Li2O, 1-25% Na2O, 0-15% KO, 0-20% MgO, 0-10% ZnO, 0-15% PO5, and 0-1% SnO2. In the description of the range of each component, percentages refer to mole percent unless otherwise specified.

[0073] SiO2 is a component that forms the glass network. If the SiO2 content is too low, vitrification becomes difficult, and the thermal expansion coefficient becomes too high, which tends to reduce thermal shock resistance. Therefore, the preferred lower limit range of SiO2 is 40% or more, 50% or more, 55% or more, 57% or more, 59% or more, and particularly 61% or more. On the other hand, if the SiO2 content is too high, meltability and formability tend to decrease, and the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of surrounding materials. Therefore, the preferred upper limit range of SiO2 is 80% or less, 70% or less, 68% or less, 66% or less, 65% or less, and particularly 64.5% or less.

[0074] Al2O3 is a component that enhances ion exchange performance and also increases strain point, Young's modulus, fracture toughness, and Vickers hardness. Therefore, the preferred lower limit range of Al2O3 is 5% or more, 8% or more, 10% or more, 11% or more, or 11.2% or more. On the other hand, if the Al2O3 content is too high, the high-temperature viscosity increases, and meltability and formability tend to decrease. In addition, devitrification crystals tend to precipitate in the glass, making it difficult to form it into a plate shape by the overflow downdraw method or the like. In particular, when an alumina-based refractory is used as the formed body refractory and a glass plate is formed by the overflow downdraw method, spinel devitrification crystals tend to precipitate at the interface with the alumina-based refractory. Furthermore, acid resistance also decreases, making it difficult to apply to an acid treatment process. Therefore, the preferred upper limit range of Al2O3 is 25% or less, 21% or less, 20.5% or less, 20% or less, 19.9% ​​or less, 19.5% or less, 19.0% or less, particularly 18.9% or less.

[0075] BO is a component that reduces high-temperature viscosity and density, stabilizes glass, and reduces crystal precipitation, lowering the liquidus temperature. It also suppresses Young's modulus and increases bending strength and crack resistance. However, excessive BO content tends to cause surface discoloration (known as fading) during ion exchange treatment, reduce water resistance, and reduce the compressive stress value of the compressive stress layer. Therefore, the preferred lower limit of BO is 0% or more, 0.01% or more, 0.02% or more, 0.1% or more, or 0.3% or more, while the preferred upper limit is 30% or less, 25% or less, 22% or less, 20% or less, and particularly 15% or less. From the perspective of prioritizing increasing the maximum compressive stress value CS of the surface compressive stress layer, the BO content can be more preferably 0.2 to 5% or 0.3 to 1%. From the viewpoint of improving chemical durability for the purpose of suppressing defects during etching, the upper limit of the BO content can be preferably 1%, 1.5%, or 2% or more, and the lower limit can be 5%, 4.5%, 4%, or 3% or less. On the other hand, from the viewpoint of prioritizing suppression of the Young's modulus, the BO content can be more preferably 10 to 25%, 15 to 23%, or 18 to 22%.

[0076] Li2O is an ion-exchange component, specifically, Li ions contained in the glass and K ions in the molten salt are ion-exchanged to obtain a high surface compressive stress. Li2O also reduces high-temperature viscosity and improves meltability and formability. Therefore, the preferred lower limit of Li2O is 0% or more, 3% or more, 4% or more, 4.2% 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 particularly 8% or more. The preferred upper limit of Li2O is 25% or less, 20% or less, 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 particularly 8.9% or less.

[0077] Na2O is an ion exchange component and also a component that reduces high-temperature viscosity and improves meltability and formability. Na2O also improves devitrification resistance and reaction devitrification resistance with refractory molded bodies, particularly alumina refractories. Therefore, the preferred lower limit of Na2O is 1% or more, 5% or more, 7% or more, 8% or more, 8.5% or more, 9% or more, 9.5% or more, 10% or more, 11% or more, 12% or more, and particularly 12.5% ​​or more. On the other hand, if the Na2O content is too high, the phase separation viscosity tends to decrease. Furthermore, acid resistance may decrease, and the glass composition may become unbalanced, resulting in a decrease in devitrification resistance. Therefore, the preferred upper limit of Na2O is 25% or less, 20% or less, 19.5% or less, 19% or less, 18% or less, 17% or less, 16.5% or less, 16% or less, 15.5% or less, and particularly 15% or less.

[0078] KO is a component that reduces high-temperature viscosity and improves meltability and formability. It also improves devitrification resistance and increases Vickers hardness. Therefore, the preferred lower limit of KO is 0% or more, 0.01% or more, 0.02% or more, 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, and particularly 3.5% or more. On the other hand, if the KO content is too high, the phase separation viscosity tends to decrease. Furthermore, acid resistance tends to decrease and the glass composition tends to be unbalanced, resulting in a decrease in devitrification resistance. Therefore, the preferred upper limit of KO is 15% or less, 10% or less, 5.5% or less, 5% or less, and particularly less than 4.5%.

[0079] MgO is a component that reduces high-temperature viscosity, improves meltability and formability, and increases the strain point and Young's modulus. Among alkaline earth metal oxides, it is a component that is highly effective in improving ion exchange performance. Therefore, the preferred lower limit of MgO is 0% or more, 0.1% or more, 0.5% or more, 1% or more, and particularly 2% or more. However, if the MgO content is too high, the density and thermal expansion coefficient tend to increase, and the glass is prone to devitrification. Therefore, the preferred upper limit of MgO is 20% or less, 12% or less, 10% or less, 8% or less, 6% or less, and particularly 5% or less.

[0080] ZnO is a component that enhances ion exchange performance, and is particularly effective in increasing the compressive stress value. It also reduces high-temperature viscosity without reducing low-temperature viscosity. However, if the ZnO content is too high, the glass tends to undergo phase separation, reduce devitrification resistance, increase density, and reduce the stress depth of the compressive stress layer. Therefore, the ZnO content is preferably 0 to 10%, 0 to 6%, 0 to 5%, 0 to 1%, or 0 to 0.5%, and particularly preferably 0 to less than 0.1%.

[0081] PO is a component that enhances ion exchange performance, particularly increasing the stress depth of the compressive stress layer. It also suppresses the Young's modulus. Therefore, the preferred lower limit range of PO is 0% or more, 2% or more, 2.1% or more, 2.5% or more, 3% or more, 4% or more, or 4.5% or more. However, if the PO content is too high, the glass may become cloudy due to phase separation, or the water resistance may be reduced. Therefore, the preferred upper limit range of PO is 15% or less, 10% or less, or 8.5% or less.

[0082] SnO2 is a component that enhances ion exchange performance, and therefore the content of SnO2 is preferably 0% to 1%, 0.01% to 1%, 0.05% to 1%, and particularly preferably 0.1% to 1%.

[0083] In addition to the above components, the glass may contain, for example, the following components as part of the glass composition.

[0084] Compared with other components, CaO is highly effective in reducing high-temperature viscosity, improving meltability and formability, and increasing strain point and Young's modulus without reducing devitrification resistance. The CaO content is preferably 0 to 10%. However, if the CaO content is too high, the density and thermal expansion coefficient increase, and the component balance of the glass composition is lost, making the glass more susceptible to devitrification and reducing ion exchange performance. Therefore, the preferred CaO content is 0 to 5%, 0.01 to 4%, 0.1 to 3%, and particularly 1 to 2.5%.

[0085] SrO is a component that reduces high-temperature viscosity, improves meltability and formability, and increases the strain point and Young's modulus without reducing devitrification resistance. However, if the SrO content is too high, the density and thermal expansion coefficient increase, the ion exchange performance decreases, and the component balance of the glass composition is lost, making the glass more susceptible to devitrification. The preferred range of SrO content is 0 to 5%, 0 to 3%, 0 to 1%, and particularly 0 to less than 0.1%.

[0086] BaO is a component that reduces high-temperature viscosity, improves meltability and formability, and increases strain point and Young's modulus without reducing devitrification resistance. However, if the BaO content is too high, the density and thermal expansion coefficient increase, the ion exchange performance decreases, and the component balance of the glass composition is lost, making the glass more susceptible to devitrification. The preferred BaO content range is 0 to 5%, 0 to 3%, 0 to 1%, and particularly 0 to less than 0.1%.

[0087] ZrO2 is a component that significantly enhances ion exchange performance and also increases the viscosity near the liquidus viscosity and the strain point. However, if its content is too high, devitrification resistance may be significantly reduced and the density may become too high. Therefore, the preferred upper limit range of ZrO2 is 10% or less, 8% or less, 6% or less, and particularly 5% or less. When it is desired to enhance ion exchange performance, it is preferable to incorporate ZrO2 into the glass composition. In this case, the preferred lower limit range of ZrO2 is 0.001% or more, 0.01% or more, 0.5%, and particularly 1% or more.

[0088] As a fining agent, one or more selected from the group consisting of As2O3, Sb2O3, F, Cl, and SO3 (preferably Cl and SO3) may be incorporated in an amount of 0 to 30,000 ppm (3%).

[0089] Rare earth oxides such as NdO and LaO increase the Young's modulus and can control the color of glass by eliminating the color when a complementary color is added. However, the raw materials themselves are expensive, and adding a large amount of these oxides can reduce devitrification resistance. Therefore, the content of rare earth oxides is preferably 4% or less, 3% or less, 2% or less, 1% or less, and particularly 0.5% or less.

[0090] From an environmental perspective, it is preferable that As2O3, F, PbO, and Bi2O3 are not substantially contained. Here, "substantially not contained" means that these are not actively added as glass components, but are allowed to be present at the impurity level, and specifically means that the content of each of the above components is less than 500 ppm.

[0091] In the ion exchange step S4, the glass is subjected to an ion exchange treatment. In this embodiment, the glass is immersed in a molten salt for the ion exchange treatment. By converting the treatment glass into chemically strengthened glass through the ion exchange treatment in this manner, the mechanical strength of the glass is improved.

[0092] The molten salt is a salt containing a component that can be ion-exchanged with the components in the glass, typically an alkali metal nitrate. Examples of alkali metal nitrates include NaNO, KNO, and LiNO. These can be used alone (at 100% by mass) or in combination. When multiple alkali metal nitrates are mixed, the mixing ratio can be determined arbitrarily. For example, the ratio can be, by mass, 5-95% NaNO and 5-95% KNO, preferably 30-80% NaNO and 20-70% KNO, and more preferably 50-70% NaNO and 30-50% KNO.

[0093] The temperature of the molten salt is, for example, 350°C to 500°C, and preferably 355°C to 470°C, 360°C to 450°C, 365°C to 430°C, or 370°C to 410°C. The immersion time is, for example, 3 to 300 minutes, and preferably 5 to 120 minutes, or 7 to 100 minutes. Of course, the conditions such as the temperature of the molten salt and the immersion time can be appropriately changed depending on the glass composition, etc., within a range in which the above-mentioned stress characteristics can be obtained.

[0094] The glass after the ion exchange step S4 has a compressive stress layer (surface compressive stress layer) on the surface of the glass and a tensile stress layer deeper inside the glass than the compressive stress layer. That is, the glass after the second etching step S5 also has a compressive stress layer and a tensile stress layer, although the surface is slightly removed by etching.

[0095] The lower limit range of the maximum compressive stress value CS of the compressive stress layer after the second etching step S5 is preferably 450 MPa or more, 470 MPa or more, 500 MPa or more, or 530 MPa or more. This allows for high mechanical strength. Note that as the maximum compressive stress value CS increases, the internal tensile stress tends to increase, which may result in a dangerous fracture mode upon fracture. Therefore, the upper limit range of the maximum compressive stress value CS is preferably 1500 MPa or less, 1300 MPa or less, 1100 MPa or less, 1000 MPa or less, or 900 MPa or less.

[0096] The lower limit range of the depth DOL of the compressive stress layer after the second etching step S5 is preferably 2 μm or more, 3 μm or more, or 4 μm or more. In this way, high mechanical strength can be obtained. In addition, in order to keep the integrated value of the compressive stress value low, the upper limit range of the depth DOL of the compressive stress layer is preferably 50 μm or less, 40 μm or less, 20 μm or less, 19 μm or less, 18 μm or less, or 17 μm or less.

[0097] When the depth of the compressive stress layer after the second etching step S5 is DOL and the thickness of the glass after the second etching step S5 is t1, DOL / t1 is preferably 0.1 or more, 0.12 or more, 0.13 or more, 0.14 to 0.3, or 0.15 to 0.28. By setting DOL / t1 in such a range, it is possible to ensure safety by preventing dangerous fractures when broken while maintaining high mechanical strength.

[0098] In addition, CS and DOL can be derived by measuring the stress distribution of glass using, for example, a surface stress meter FSM-6000 or SLP-1000 manufactured by Orihara Seisakusho.

[0099] According to the manufacturing method of the second embodiment described above, the glass is chemically strengthened in the ion exchange step S4, which facilitates increasing the mechanical strength of the glass. Furthermore, because the first etching step S3 is performed before the ion exchange step S4, the ion exchange step S4 can perform a balanced ion exchange treatment on the glass surface from which sharp irregularities due to microcracks and the like have been removed. Furthermore, because the second etching step S5 is performed after the ion exchange step S4, even if defects (surface roughness due to molten salt) are formed on the glass surface due to the ion exchange step S4, these defects can be removed.

[0100] Third Embodiment As shown in FIG. 3 , a method for manufacturing glass according to a third embodiment includes, in this order, an ion exchange step S6 of immersing glass in a molten salt (ion exchange liquid) to perform ion exchange treatment, a first etching step S7 of immersing the glass in a first etching liquid to etch the glass, and a second etching step S8 of immersing the glass in a second etching liquid to etch the glass.

[0101] The ion exchange step S6 is similar to the ion exchange step S4 in the second embodiment, the first etching step S7 is similar to the first etching step S1 in the first embodiment, and the second etching step S8 is similar to the second etching step S2 in the first embodiment. The third embodiment differs from the first and second embodiments in that the ion exchange step S6 is performed before the first etching step S7. This chemically strengthens the glass through the ion exchange step S6, making it easier to increase the mechanical strength of the glass. Furthermore, because the first etching step S7 and the second etching step S8 are performed after the ion exchange step S6, even if defects (surface roughness due to molten salt) are formed on the glass surface due to the ion exchange step S6, the defects can be removed.

[0102] Although the embodiment of the present invention has been described, the embodiment of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention.

[0103] In the above embodiment, the ion exchange step is performed before the first etching step, or after the first etching step and before the second etching step. However, the ion exchange step may be performed after the second etching step. In this case, however, if defects (surface roughness due to molten salt) are formed on the glass surface due to the ion exchange step, the defects cannot be removed in the first etching step or the second etching step. Therefore, if defects on the glass surface due to the ion exchange step are a problem, it is preferable to further perform a third etching step using a sulfuric acid-based etching solution, which corresponds to the second etching step (finishing), after the ion exchange step.

[0104] In the above-described embodiment, the shape of the glass is not particularly limited, and may be, for example, rectangular (square, oblong), circular, elliptical, etc. in plan view.

[0105] In the above-described embodiment, the glass may be subjected to three-dimensional bending as necessary. Specifically, by subjecting the glass to three-dimensional bending in advance, either entirely or partially, the three-dimensional bent shape can be imparted to the glass that is finally produced.

[0106] In the above-described embodiment, the glass may be bendable. In this case, the glass may have a thin portion and a thick portion that is thicker than the thin portion, and may be bendable at the thin portion. Such bendable glass may be suitably used as a cover glass for a foldable device, etc.

[0107] In the above embodiment, a case where a single ion exchange step is performed has been exemplified, but two or more ion exchange steps may be performed. Heat treatment may also be performed before or after ion exchange. Heat treatment can reduce stress and promote ion diffusion, thereby controlling the depth of the compressive stress layer, etc. When multiple ion exchange steps are performed, the stress distribution of the tempered glass may have at least one of a bending point, a maximum value, a minimum value, or an inflection point in the compressive stress layer region.

[0108] The glass article according to the present invention will be described below based on examples. Note that the following examples are merely illustrative and the present invention is not limited to the following examples in any way.

[0109] The samples were prepared as follows: First, glasses having the glass compositions shown in Table 1 were prepared. The glass having composition A was an alkali-free glass, and the glass having composition B was an alkali-containing glass (aluminosilicate glass).

[0110]

[0111] Specifically, glass raw materials were prepared so as to have the compositions shown in Table 1, and were melted in a test melting furnace. Thereafter, the obtained molten glass was formed into a sheet by an overflow downdraw method, and cut to a predetermined size, thereby preparing glass.

[0112] The glass was then subjected to various treatments, including one or two etching steps, under the conditions shown in Tables 2 and 3. Nos. 1 to 7 shown in Table 2 are examples of the present invention, and Nos. 8 to 11 shown in Table 3 are comparative examples.

[0113]

[0114]

[0115] In Example No. 1, a hydrochloric acid-based etching process (first time) using a first etching solution of hydrofluoric acid-hydrochloric acid-ammonium bifluoride system and a sulfuric acid-based etching process (second time) using a second etching solution of hydrofluoric acid-sulfuric acid-ammonium bifluoride system was performed on an alkali-free glass having composition A, measuring 300 mm x 400 mm and having a thickness t0 of 500 μm (hydrochloric acid-based etching process → sulfuric acid-based etching process). In each etching process, the alkali-free glass was immersed in the respective etching solution. The etching amount V1 in the first hydrochloric acid-based etching process was 100 μm, and the etching amount V2 in the second sulfuric acid-based etching process was 100 μm. As a result, the total etching amount was 200 μm, and the thickness t1 of the alkali-free glass after processing was 300 μm. As shown in Table 2, Example No. In Example 1, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, 40 to 90% by mass of hydrofluoric acid and 10 to 60% by mass of hydrochloric acid, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, 10 to 50% by mass of hydrofluoric acid and 50 to 90% by mass of sulfuric acid.

[0116] In Example No. 2, an alkali-containing glass having composition B and measuring 300 mm x 400 mm and a thickness t0 of 500 μm was subjected to a hydrochloric acid-based etching process (first time) using a first etching solution of hydrofluoric acid, hydrochloric acid, and ammonium hydrogen fluoride, an ion exchange process using a molten salt of KNO3, and a sulfuric acid-based etching process (second time) using a second etching solution of hydrofluoric acid, sulfuric acid, and ammonium hydrogen fluoride, in this order (hydrochloric acid-based etching process → ion exchange process → sulfuric acid-based etching process). In each etching process, the alkali-containing glass was immersed in the respective etching solution, and in the ion exchange process, the alkali-containing glass was immersed in the molten salt. The etching depth V1 in the first hydrochloric acid-based etching process was 198 μm, and the etching depth V2 in the second sulfuric acid-based etching process was 2 μm. As a result, the total etching depth was 200 μm, and the thickness t1 of the alkali-containing glass after processing was 300 μm. As shown in Table 2, Example No. In Example 2, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, 40 to 90% by mass of hydrofluoric acid and 10 to 60% by mass of hydrochloric acid, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, 10 to 50% by mass of hydrofluoric acid and 50 to 90% by mass of sulfuric acid.

[0117] In Example No. 3, an alkali-containing glass having composition B and measuring 65 mm × 160 mm and a thickness t0 of 35 μm was subjected to an ion exchange process using a molten salt made of KNO3, a hydrochloric acid-based etching process using a first etching solution of hydrofluoric acid, hydrochloric acid, and ammonium hydrogen fluoride, and a sulfuric acid-based etching process using a second etching solution of hydrofluoric acid, sulfuric acid, and ammonium hydrogen fluoride, in this order (ion exchange process → hydrochloric acid-based etching process → sulfuric acid-based etching process). In each etching process, the alkali-containing glass was immersed in the respective etching solution, and in the ion exchange process, the alkali-containing glass was immersed in molten salt. The etching depth V1 in the first hydrochloric acid-based etching process was 2 μm, and the etching depth V2 in the second sulfuric acid-based etching process was 1 μm. As a result, the total etching depth was 3 μm, and the thickness t1 of the alkali-containing glass after processing was 32 μm. As shown in Table 2, Example No. In Example 3, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, 40 to 90% by mass of hydrofluoric acid and 10 to 60% by mass of hydrochloric acid, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, 10 to 50% by mass of hydrofluoric acid and 50 to 90% by mass of sulfuric acid.

[0118] In Example No. 4, an alkali-containing glass having composition B and measuring 65 mm x 160 mm and a thickness t0 of 35 μm was subjected to a hydrochloric acid-based etching process (first time) using a first etching solution based on hydrofluoric acid, hydrochloric acid, and ammonium hydrogen fluoride, an ion exchange process using a molten salt composed of KNO, and a sulfuric acid-based etching process (second time) using a second etching solution based on hydrofluoric acid, sulfuric acid, and ammonium hydrogen fluoride, in this order (hydrochloric acid-based etching process → ion exchange process → sulfuric acid-based etching process). In each etching process, the alkali-containing glass was immersed in the respective etching solution, and in the ion exchange process, the alkali-containing glass was immersed in the molten salt. The etching depth V1 in the first hydrochloric acid-based etching process was 3 μm, and the etching depth V2 in the second sulfuric acid-based etching process was 2 μm. As a result, the total etching depth was 5 μm, and the thickness t1 of the alkali-containing glass after processing was 30 μm. As shown in Table 2, Example No. In Example 4, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, 40 to 90 mass % of hydrofluoric acid and 10 to 60 mass % of hydrochloric acid, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, 10 to 50 mass % of hydrofluoric acid and 50 to 90 mass % of sulfuric acid.

[0119] In Example No. 5, an alkali-containing glass having composition B and measuring 65 mm × 160 mm and a thickness t0 of 35 μm was subjected to a hydrochloric acid-based etching process (first time) using a hydrofluoric acid-hydrochloric acid-based first etching solution (not containing ammonium bifluoride), an ion exchange process using a molten salt composed of KNO3, and a sulfuric acid-based etching process (second time) using a hydrofluoric acid-sulfuric acid-ammonium bifluoride-based second etching solution in this order (hydrochloric acid-based etching process → ion exchange process → sulfuric acid-based etching process). In each etching process, the alkali-containing glass was immersed in the respective etching solution, and in the ion exchange process, the alkali-containing glass was immersed in the molten salt. The etching depth V1 in the first hydrochloric acid-based etching process was 3 μm, and the etching depth V2 in the second sulfuric acid-based etching process was 2 μm. As a result, the total etching depth was 5 μm, and the thickness t1 of the alkali-containing glass after processing was 30 μm. As shown in Table 2, Example No. In No. 5, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, hydrofluoric acid: 40 to 90 mass % and hydrochloric acid: 10 to 60 mass %, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, hydrofluoric acid: 10 to 50 mass % and sulfuric acid: 50 to 90 mass %.

[0120] In Example No. 6, an alkali-containing glass having composition B and measuring 65 mm x 160 mm and a thickness t0 of 35 μm was subjected to a hydrochloric acid-based etching process (first time) using a hydrofluoric acid-hydrochloric acid-based first etching solution (not containing ammonium bifluoride), an ion exchange process using a molten salt consisting of KNO3, and a sulfuric acid-based etching process (second time) using a hydrofluoric acid-sulfuric acid-based second etching solution (not containing ammonium bifluoride) in this order (hydrochloric acid-based etching process → ion exchange process → sulfuric acid-based etching process). In each etching process, the alkali-containing glass was immersed in the respective etching solution, and in the ion exchange process, the alkali-containing glass was immersed in the molten salt. The etching depth V1 in the first hydrochloric acid-based etching process was 4 μm, and the etching depth V2 in the second sulfuric acid-based etching process was 1 μm. As a result, the total etching depth was 5 μm, and the thickness t1 of the alkali-containing glass after processing was 30 μm. As shown in Table 2, Example No. In Example 6, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, 40 to 90% by mass of hydrofluoric acid and 10 to 60% by mass of hydrochloric acid, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, 10 to 50% by mass of hydrofluoric acid and 50 to 90% by mass of sulfuric acid.

[0121] In Example No. 7, an alkali-containing glass having composition B and measuring 65 mm x 160 mm and a thickness t0 of 55 μm was subjected to a hydrochloric acid-based etching process (first time) using a first etching solution based on hydrofluoric acid, hydrochloric acid, and ammonium hydrogen fluoride, an ion exchange process using a molten salt composed of KNO, and a sulfuric acid-based etching process (second time) using a second etching solution based on hydrofluoric acid, sulfuric acid, and ammonium hydrogen fluoride, in this order (hydrochloric acid-based etching process → ion exchange process → sulfuric acid-based etching process). In each etching process, the alkali-containing glass was immersed in the respective etching solution, and in the ion exchange process, the alkali-containing glass was immersed in the molten salt. The etching depth V1 in the first hydrochloric acid-based etching process was 4 μm, and the etching depth V2 in the second sulfuric acid-based etching process was 1 μm. As a result, the total etching depth was 5 μm, and the thickness t1 of the alkali-containing glass after processing was 50 μm. As shown in Table 2, Example No. In Example 7, the concentrations of the components of the etching solution in the first hydrochloric acid-based etching step are, in a dehydrated state, 40 to 90% by mass of hydrofluoric acid and 10 to 60% by mass of hydrochloric acid, and the concentrations of the components of the etching solution in the second sulfuric acid-based etching step are, in a dehydrated state, 10 to 50% by mass of hydrofluoric acid and 50 to 90% by mass of sulfuric acid.

[0122] In Comparative Example No. 8, a hydrochloric acid-based etching process using a hydrofluoric acid-hydrochloric acid-ammonium bifluoride-based etching solution was performed on alkali-free glass of composition A, measuring 300 mm x 400 mm and having a thickness t0 of 500 μm. In other words, the etching process was performed only once. In the etching process, the alkali-free glass was immersed in the etching solution. The etching amount in the etching process was 200 μm. As a result, the thickness t1 of the alkali-free glass after processing was 300 μm. Note that, as shown in Table 3, in Comparative Example No. 8, the component concentrations of the etching solution in the hydrochloric acid-based etching process satisfied the following in a dehydrated state: hydrofluoric acid: 40 to 90 mass% and hydrochloric acid: 10 to 60 mass%, but a sulfuric acid-based etching process using a hydrofluoric acid-sulfuric acid-ammonium bifluoride-based etching solution was not performed.

[0123] In Comparative Example No. 9, a non-alkali glass having composition A and measuring 300 mm x 400 mm and having a thickness t0 of 500 μm was subjected to a hydrochloric acid-based etching process (first time) using a hydrofluoric acid-hydrochloric acid-ammonium bifluoride-based etching solution, followed by a sulfuric acid-based etching process (second time) using a hydrofluoric acid-sulfuric acid-ammonium bifluoride-based etching solution (hydrochloric acid-based etching process → sulfuric acid-based etching process). In each etching process, the non-alkali glass was immersed in the respective etching solution. The etching depth V1 in the first sulfuric acid-based etching process was 100 μm, and the etching depth V2 in the second hydrochloric acid-based etching process was 100 μm. As a result, the total etching depth was 200 μm, and the thickness t1 of the non-alkali glass after the process was 300 μm. As shown in Table 3, Comparative Example No. In Example 9, the concentration of each component of the etching solution in the first hydrochloric acid etching step is, in a dehydrated state, 40 to 90 mass% hydrofluoric acid, but does not satisfy the concentration of 10 to 60 mass% hydrochloric acid. Also, the concentration of each component of the etching solution in the second sulfuric acid etching step is, in a dehydrated state, 50 to 90 mass% sulfuric acid, but does not satisfy the concentration of 10 to 50 mass% hydrofluoric acid.

[0124] In Comparative Example No. 10, an alkali-containing glass having composition B, measuring 65 mm × 160 mm and having a thickness t0 of 35 μm, was subjected to an ion exchange process using a molten salt made of KNO3 and a sulfuric acid-based etching process using a hydrofluoric acid-sulfuric acid-ammonium bifluoride-based etching solution, in that order (ion exchange process → sulfuric acid-based etching process). In other words, only one etching process was performed. In the ion exchange process, the alkali-containing glass was immersed in the molten salt, and in the etching process, the alkali-containing glass was immersed in the etching solution. The etching depth V1 in the etching process was 3 μm. As a result, the thickness t1 of the alkali-free glass after treatment was 32 μm. Note that, as shown in Table 3, in Comparative Example No. 10, the component concentrations of the etching solution in the sulfuric acid-based etching process in a dehydrated state satisfied the following ranges: hydrofluoric acid: 10 to 50 mass % and sulfuric acid: 50 to 90 mass %. However, the hydrochloric acid-based etching process using a hydrofluoric acid-hydrochloric acid-ammonium bifluoride-based etching solution was not performed.

[0125] In Comparative Example No. 11, an alkali-containing glass having composition B and measuring 65 mm × 160 mm and a thickness t0 of 35 μm was subjected to an ion exchange process using a molten salt made of KNO3, a sulfuric acid-based etching process (first process) using a hydrofluoric acid-sulfuric acid-ammonium bifluoride-based etching solution, and a hydrochloric acid-based etching process (second process) using a hydrofluoric acid-hydrochloric acid-ammonium bifluoride-based etching solution, in this order (ion exchange process → sulfuric acid-based etching process → hydrochloric acid-based etching process). In the ion exchange process, the alkali-containing glass was immersed in the molten salt, and in each etching process, the alkali-containing glass was immersed in the respective etching solutions. The etching depth V1 in the first sulfuric acid-based etching process was 2 μm, and the etching depth V2 in the second hydrochloric acid-based etching process was 1 μm. As a result, the total etching depth was 3 μm, and the thickness t1 of the alkali-free glass after processing was 32 μm. As shown in Table 3, Comparative Example No. In Example 11, the concentrations of the components of the etching solution in the first sulfuric acid-based etching step are, in a dehydrated state, 40 to 90% by mass of hydrofluoric acid and 10 to 60% by mass of hydrochloric acid, and the concentrations of the components of the etching solution in the second hydrochloric acid-based etching step are, in a dehydrated state, 10 to 50% by mass of hydrofluoric acid and 50 to 90% by mass of sulfuric acid. However, the sulfuric acid-based etching step is performed before the hydrochloric acid-based etching step, which is the reverse of the order from the examples.

[0126] For some of the examples (Nos. 2 to 7) and comparative examples (Nos. 10 and 11) in which the ion exchange process was performed, the CS and DOL of each glass after treatment were measured. The CS and DOL shown in Tables 2 and 3 are values ​​measured for each glass after treatment using a surface stress meter FSM-6000LE manufactured by Orihara Seisakusho.

[0127] In order to compare the performance of the above-mentioned Examples (Nos. 1 to 7) and Comparative Examples (Nos. 8 to 11), strength tests were conducted on each glass. For each of the glasses Nos. 1, 2, 8, and 9, which had a relatively thick thickness after treatment, the fracture stress was measured by a ring-on-ring test (ROR test). On the other hand, for each of the glasses Nos. 3 to 7, 10, and 11, which had a relatively thin thickness after treatment, the fracture stress was measured by a two-point bending test.

[0128] As shown in Figure 4, in the ring-on-ring test, a glass 2 was supported from below by a support ring 1 having a relatively large diameter, and a piston ring 3 having a relatively small diameter was lowered from above while applying a load to the glass 2, and the fracture stress value at the time when the glass 2 broke was measured. The glass 2 had a size of 50 mm x 50 mm and a thickness (thickness after treatment) of 300 µm. The diameter of the support ring 1 was 12.5 mm, the diameter of the piston ring 3 was 6.25 mm, and the descending speed of the piston ring 3 was 5 mm / min. The ring-on-ring test was performed on 20 pieces of each of the glasses Nos. 1, 2, 8, and 9, and the median, maximum, and minimum fracture stress values ​​were evaluated for each glass. Note that a fracture stress of 2500 MPa or more in the ring-on-ring test can be considered to have sufficient mechanical strength.

[0129] As shown in Table 2, Examples 1 and 2 exhibited favorable results, with the minimum fracture stress exceeding 2500 MPa in the ring-on-ring test. On the other hand, as shown in Table 3, Comparative Example 8 exhibited favorable results, with the microcracks removed by the action of the hydrochloric acid-based etching solution, resulting in a minimum fracture stress exceeding 1800 MPa in the ring-on-ring test. However, since no sulfuric acid-based etching solution was used, the minimum fracture stress in the ring-on-ring test was less than 2500 MPa. Comparative Example 9 employed both a hydrochloric acid-based etching solution and a sulfuric acid-based etching solution, but the respective component concentrations were inappropriate, resulting in insufficient improvement in surface quality, and even the median fracture stress in the ring-on-ring test was less than 2500 MPa.

[0130] As shown in FIG. 5 , in the two-point bending test, a glass sheet 4 was sandwiched between two plates 5 and 6 from above and below, and the upper plate 5 was lowered while being bent in a U-shape. This so-called two-point bending test measured and evaluated the fracture stress. In the two-point bending test, the fracture stress was calculated based on the distance between the two plates 5 and 6 when the glass sheet 4 broke due to the bend. The glass sheet 4 measured 65 mm × 160 mm and had a thickness (after treatment) of 30 μm. The glass sheet 4 was placed between the plates 5 and 6 so that it bent in a U-shape along its long side (160 mm). The plate 5 was lowered at a speed of 20 mm / min. The two-point bending test was performed on 20 sheets of each of the glasses Nos. 3 to 7, 10, and 11, and the median, maximum, and minimum fracture stresses were evaluated for each glass sheet. If the breaking stress in the two-point bending test is 2500 MPa or more, the glass can be considered to have sufficient mechanical strength.

[0131] As shown in Table 2, in Examples 3 to 7, the minimum breaking stress in the two-point bending test exceeded 2500 MPa, demonstrating favorable results. In particular, in Example 4, the ion exchange process was performed after the hydrochloric acid-based etching process and before the sulfuric acid-based etching process, resulting in favorable reinforcement quality in the ion exchange process and a very high breaking stress in the two-point bending test. Furthermore, the fact that both the first and second etching solutions in Example 4 contain ammonium hydrogen fluoride is also thought to be one of the factors contributing to the improved breaking stress. On the other hand, as shown in Table 3, in Comparative Example 10, only a sulfuric acid-based etching solution was used, resulting in insufficient removal of microcracks, resulting in large variations in the breaking stress in the two-point bending test and a minimum breaking stress significantly below 2500 MPa. Furthermore, in Comparative Example 11, the order of the hydrochloric acid-based etching solution and the sulfuric acid-based etching solution was reversed, resulting in finish machining followed by rough machining. As a result, the minimum value of the breaking stress in the two-point bending test is more than 2000 MPa, but less than 2500 MPa.

[0132] The glass article of the present invention can be used, for example, for smartphones, mobile phones, tablet computers, personal computers, digital cameras, touch panel displays, cover glass for other display devices, in-vehicle display devices, in-vehicle panels, etc.

[0133] 1 Support ring 2 Glass 3 Piston ring 4 Glass 5, 6 Plate-shaped body

Claims

1. A method for manufacturing glass, comprising: a first etching step of etching the glass with a first etching liquid; and a second etching step of etching the glass with a second etching liquid after the first etching step, wherein the first etching liquid contains, by mass %, 30 to 90% hydrofluoric acid and 10 to 70% hydrochloric acid in a dehydrated state, and the second etching liquid contains, by mass %, 10 to 50% hydrofluoric acid and 50 to 90% sulfuric acid in a dehydrated state.

2. The method for producing glass according to claim 1, wherein at least one of the first etching solution and the second etching solution contains ammonium hydrogen fluoride.

3. The method for manufacturing glass according to claim 2, wherein the first etching solution contains, in a dehydrated state, by mass percentage: hydrofluoric acid: 40 to 80%, hydrochloric acid: 10 to 40%, and ammonium hydrogen fluoride: 3 to 20%.

4. A method for manufacturing glass according to claim 2 or 3, wherein the second etching solution contains, in a dehydrated state, by mass percentage: hydrofluoric acid: 10 to 30%, sulfuric acid: 50 to 80%, and ammonium hydrogen fluoride: 3 to 20%.

5. A method for manufacturing glass according to claim 1 or 2, wherein the first etching liquid has a water content of 50 to 95% by mass, and the second etching liquid has a water content of 50 to 90% by mass.

6. The method for producing glass according to claim 1 or 2, wherein, when an etching rate in the first etching step is R1 (μm / min) and an etching rate in the second etching step is R2 (μm / min), R1 / R2≦20.

7. The method for producing glass according to claim 1 or 2, wherein, when an etching rate in the first etching step is R1 (μm / min) and an etching rate in the second etching step is R2 (μm / min), R1≦9.5 μm / min and R2≧0.5 μm / min.

8. The method for producing glass according to claim 1 or 2, wherein, when the etching amount in the first etching step is V1 (μm) and the etching amount in the second etching step is V2 (μm), V1 / V2≦80.

9. The method for producing glass according to claim 1 or 2, wherein, when an etching amount in the first etching step is V1 (μm) and an etching amount in the second etching step is V2 (μm), V1≦80 μm and V2≦10 μm.

10. A method for manufacturing glass according to claim 1 or 2, wherein in the first etching step, the temperature of the first etching liquid is 1 to 50°C, and the time for treating the glass with the first etching liquid is 0.5 to 50 minutes, and in the second etching step, the temperature of the second etching liquid is 1 to 50°C, and the time for treating the glass with the second etching liquid is 0.5 to 50 minutes.

11. The method for producing glass according to claim 1 or 2, wherein the glass is an alkali-containing glass that contains an alkali metal component as a glass composition, and the method further comprises an ion exchange step of subjecting the glass to an ion exchange treatment after the first etching step and before the second etching step.

12. The method for producing glass according to claim 1 or 2, wherein the glass is an alkali-containing glass that contains an alkali metal component as a glass composition, and the method further comprises an ion exchange step of subjecting the glass to an ion exchange treatment prior to the first etching step.

13. A method for manufacturing glass according to claim 12, wherein the glass after the second etching step has a surface compressive stress layer, and where the maximum compressive stress value of the surface compressive stress layer is CS (MPa), the depth of the surface compressive stress layer is DOL (μm), and the thickness of the glass after the second etching step is t1 (μm), then CS≧450 MPa DOL / t1≧0.

15.

14. A method for producing glass as set forth in claim 12, wherein the alkali-containing glass contains, as a glass composition, in mole percent, 40-80% SiO2, 5-25% Al2O3, 0-30% B2O3, 0-25% Li2O, 1-25% Na2O, 0-15% K2O, 0-20% MgO, 0-10% ZnO, 0-15% PO5, and 0-1% SnO2.

15. The method for producing glass according to claim 1 or 2, wherein the glass is an alkali-free glass that contains substantially no alkali metal components in its glass composition.

16. A method for manufacturing glass as described in claim 1 or 2, wherein the glass after the second etching step is in the form of a sheet having a thickness of 0.3 mm or less.

17. A method for manufacturing glass, comprising: a first etching step of etching the glass with a first etching liquid; and a second etching step of etching the glass with a second etching liquid after the first etching step, wherein the first etching liquid contains, by mass, 50 to 95% water, 2 to 45% hydrofluoric acid, and 0.5 to 30% hydrochloric acid, and the second etching liquid contains, by mass, 50 to 90% water, 1 to 25% hydrofluoric acid, and 5 to 45% sulfuric acid.

18. A method for manufacturing glass, comprising: a first etching step of etching the glass with a first etching liquid; and a second etching step of etching the glass with a second etching liquid after the first etching step, wherein the first etching liquid is an etching liquid containing hydrochloric acid, and the second etching liquid is an etching liquid containing sulfuric acid.

19. The method of claim 18, wherein at least one of the first etchant and the second etchant comprises ammonium bifluoride.

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